Activatable cytokine constructs and combination methods

Abstract

Provided herein are methods of treating a subject by administering a combination of an activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor in which the ACC includes: a first monomer construct including an optional first peptide mask (PM1), an optional third cleavable moiety (CM3), a first mature cytokine protein (CP1), a first cleavable moiety (CM1), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CP1 and the DD1; and a second monomer construct including an optional second peptide mask (PM2), an optional forth cleavable moiety (CM4), a second mature cytokine protein (CP2), a second cleavable moiety (CM2), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2; wherein the DD1 and the DD2 bind to each other thereby forming a dimer of the first monomer construct and the second monomer construct; and where the ACC is characterized by a reduction in at least one activity of the CP1 and / or CP2 as compared to a control level of the at least one activity of the CP1 and / or CP2.

Description

This application claims the benefit of U.S. Provisional Application No. 63 / 253,893, filed October 8, 2021 and U.S. Provisional Application No. 63 / 328,525, filed April 7, 2022. The entire contents of the above-identified applications are hereby fully incorporated herein by reference. REFERENCE TO AN ELECTRONIC SEQUENCE LISTING The contents of the electronic sequence listing entitled “CYTX086PCT.xml”; Size: 907,197 bytes; and Date of Creation: October 3, 2022, are incorporated herein by reference in their entirety. TECHNICAL FIELD The present disclosure relates to the field of biotechnology, and more specifically, to activatable cytokine constructs, including activatable cytokine constructs for use in immuno-oncology therapy. BACKGROUND Antibody-based therapies have been used for treating various diseases with varying degrees of success and, in some cases, toxicities due to broad target expression have limited their therapeutic effectiveness. In addition, antibody-based therapeutics have exhibited other limitations such as rapid clearance from the circulation following administration. Combination therapies have also been used with antibody-based therapies, but are often limited by increases in toxicities from the respective active drugs. Cytokines are a family of naturally-occurring small proteins and glycoproteins produced and secreted by most nucleated cells in response to viral infection and / or other antigenic stimuli. Interferons are a subclass of cytokines. Interferons are presently grouped into three major classes: interferon type I, interferon type II, and interferon type III. Interferons exert their cellular activities by binding to specific membrane receptors on a cell surface. Interferon therapy has many clinical benefits. For example, interferons are known to up-regulate the immune system and also to have antiviral and anti-proliferative properties. These biological properties have led to the clinical use of interferons as therapeutic agents for the treatment of viral infections and malignancies. Further, interferons are useful for recruiting a patient’s innate immune system to identify and attack cancer cells. Accordingly, interferon therapy has been extensively used in cancer and antiviral therapy, including for the treatment of hepatitis, Kaposi sarcoma, hairy cell leukemia, chronic myeloid leukemia (CML), follicular lymphoma, renal cell cancer (RCC), melanoma, and other disease states. However, systemic administration of interferons is accompanied by dose-dependent toxicities, including strong flu-like symtpoms, neurological symptoms, hepatotoxicity, bone marrow suppression, and arrythmia, among others. In a melanoma patient study, the combination of Pembrolizumab and Pegylated IFNa led to an ORR of 60.5%. The combination treatment was also associated with 49% of G3 / G4 adverse events which required dose reduction of Pegylated IFNa (Davar et al., J. Clin. Oncol., 2018). These undesired side-effects have limited the dosage of interferon therapies and sometimes leads to discontinuation or delay of interferon treatment. Interleukins are another subclass of cytokines. Interleukins regulate cell growth, differentiation, and motility. They are particularly important in stimulating immune responses, such as inflammation. Interleukins have been used for treatment of cancer, autoimmune disorders, and other disorders. For example, interleukin-2 (IL2) is indicated for treatment of melamona, graft-versus-host disease (GVHD), neuroblastoma, renal cell cancer (RCC), and is also considered useful for conditions including acute coronary syndrome, acute myeloid syndrome, atopic dermatitis, autoimmune liver diseases, basal cell carcinoma, bladder cancer, breast cancer, candidiasis, colorectal cancer, cutaneous T-cell lymphoma, endometriomas, HIV invention, ischemic heart disease, rheumatoid arthritis, nasopharyngeal adenocarcimoa, non-small cell lung cancer (NSCLC), ovarian cancer, pancreatic cancer, systemic lupus erythematosus, tuberculosis, and other disorders. Other interleukins, such as IL-6, IL-7, IL-12, and IL-21, among others, are potential treatments for cancers and other disorders. Interleukin therapy is often accompanied by undesired side effects, including flu-like symptoms, nausea, vomiting, diarrhea, low blood pressure, and arrhythmia, among others. Under conditions of chronic stimulation, T cells upregulate and sustain expression of the inhibitory receptor PD-1 to negatively regulate the quality and magnitude of T cell responses. The primary ligand for PD-1, PD-L1, is upregulated on many tumor cells and 2022360371   26 Mar 2026 has been associated with inhibition of anti-tumor T-cell immunity via its engagement of PD-1 on tumor-infiltrating T cells. Clinical trials have confirmed the capacity of antibody blockade of either PD-1 or PD-L1 to restore the activity of durable tumor-specific immunity in patients across multiple tumor types. (Herbst et al, 2014; Lipson et al, 2015). PD-1 / PD-L1 5 monotherapy has drawbacks, however, including a substantial number of non-responsive patients and / or patients showing recurrences, tumor resistance, and side effects associated with the autoimmune response. Thus, the need and desire for improved specificity and selectivity of cytokine therapy to the desired target is of great interest. Increased targeting of cytokine therapeutics to the disease 10 site could reduce systemic mechanism-based toxicities and lead to broader therapeutic utility. A further need exists for combination therapies to improve efficacy of treatments directed at inducing immune responses against various targets with specificity and selectivity. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general 15 knowledge in the field. SUMMARY According to a first aspect, the present invention provides use of a combination of an activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor for treating a subject in need thereof comprising administering to the subject the combination, wherein the ACC 20 includes a first monomer construct and a second monomer construct, wherein: (a) the first monomer construct comprises a first peptide mask (PM1), a first mature cytokine protein (CP1), a first and a third cleavable moieties (CM1 and CM3), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CP1 and the DD1 and the CM3 is positioned between the PM1 and the CP1, wherein the PM1 comprises a sequence 25 that is at least 85% identical to SEQ ID NO: 292 and the CP1 is an interferon comprising a sequence that is at least 80% identical to SEQ ID NO: 1 or SEQ ID NO: 448; and (b) the second monomer construct comprises a second peptide mask (PM2), a second mature cytokine protein (CP2), a second and fourth cleavable moiety (CM2 and CM4), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the 30 DD2 and the CM4 is positioned between the PM2 and the CP2; 2022360371   26 Mar 2026 wherein the DD1 and the DD2 bind to each other thereby forming a dimer of the first monomer construct and the second monomer construct; wherein the first monomer and second monomer are the same. According to a second aspect, the present invention provides Use of a combination of an 5 activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor for treatment of cancer in a subject, wherein the ACC comprises a first monomer construct and a second monomer construct, wherein: (a) the first monomer construct is a polypeptide comprising a first peptide mask (PM1), a first mature cytokine protein (CP1), a first and a third cleavable moieties (CM1 and CM3), and a 10 first dimerization domain (DD1), wherein the CM1 is positioned between the CP1 and the DD1 and the CM3 is positioned between the PM1 and the CP1, wherein the CM1 and the CM3 each comprise a sequence selected from the group consisting of SEQ ID NO: 41, SEQ ID NO: 68 and SEQ ID NO: 100, and wherein the ACC comprises a linker L1 between the PM1 and the CM3, and a linker L2 between the CM3 and the CP1 and wherein each of L1 and L2 independently 15 comprises GSGGS (SEQ ID NO: 227) or a sequence that is at least 80% identical to SEQ ID NO: 293; and (b) the second monomer construct is a polypeptide comprising a second peptide mask (PM2), a second mature cytokine protein (CP2), a second and a fourth cleavable moieties (CM2 and CM4), and a second dimerization domain (DD2) wherein the CM2 is positioned between the 20 CP2 and the DD2 and the CM4 is positioned between the PM2 and the CP2; wherein the DD1 and the DD2 bind to each other thereby forming a dimer of the first monomer construct and the second monomer construct, and wherein the first monomer construct and the second monomer construct are the same. According to a third aspect, the present invention provides Use of a combination of an 25 activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor for treatment of cancer in a subject, wherein the ACC comprises a first monomer construct and a second monomer construct, each of which comprises SEQ ID NO: 290 or SEQ ID NO: 290 without N-terminal spacer sequence QSGQ (SEQ ID NO: 480), wherein the first monomer construct and the second monomer construct are the same; and b) a PD-1 pathway inhibitor or a PD-L1 30 pathway inhibitor. 2022360371   26 Mar 2026 According to a fourth aspect, the present invention provides a method of treating a subject having a cancer comprising sequentially administering to the subject: a) an activatable cytokine construct (ACC) comprising a first monomer construct and a second monomer construct, each of which comprises SEQ ID NO: 290 or SEQ ID NO: 290 without N-terminal 5 spacer sequence QSGQ (SEQ ID NO: 480), wherein the first monomer construct and the second monomer construct are the same; and b) a PD-1 pathway inhibitor or a PD-L1 pathway inhibitor. The present disclosure provides combinations, compositions, kits, and methods for treating a subject by administering a combination of an activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor to the subject. In certain aspects, the combination increases 10 efficacy in therapy. In certain aspects, the combination reduces toxicity of one or both of the combination components when administered to the subject. In certain aspects, the combination reduces or inhibits tumor growth, proliferation, and / or metastasis. In certain aspects, the combination treats a subject suffering from cancer or an infection. In certain aspects, the combination augments or potentiates therapeutic efficacy and / or therapeutic index relative to a 15 conventional cytokine therapy and / or conventional PD-1 / PD-L1 inhibitor therapy in the subject. In certain aspects, the combination augments or potentiates therapeutic efficacy and / or therapeutic index relative to a conventional cytokine and PD-1 / PD-L1 inhibitor combination therapy in the subject. In certain aspects, the combination augments or potentiates therapeutic efficacy and / or therapeutic index relative to administering the ACC alone. 20          In one aspect, the ACC may include: (a) a first monomer comprising a first peptide mask (PM1), a first mature cytokine protein (CP1), a first and a third cleavable moieties (CM1 and CM3), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CPI and the DD1, and the CM3 is positioned between the PM1 and the CPI; and (b) a second monomer comprising a second mature cytokine protein (CP2), a second cleavable moiety (CM2), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2, where: the CM1, the CM2, and the CM3 function as a substrate for a protease; the DD1 and the DD2 bind to each other; and where the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. The protease(s) that cleave the CM1, CM2, and CM3 may be overexpressed in diseased tissue (e.g., tumor tissue) relative to healthy tissue. The ACC may be activated upon cleavage of the CM1, CM2, and / or CM3 so that the cytokine may exert its activity in the diseased tissue (e.g., in a tumor microenvironment) while the cytokine activity is attenuated in the context of healthy tissue. Thus, the ACCs provided herein may provide reduced toxicity relative to traditional cytokine therapeutics, enable higher effective dosages of cytokine, and / or increase the therapeutic window for the cytokine. Provided herein are activatable cytokine constructs (ACC) that include a first monomer construct and a second monomer construct, wherein: (a) the first monomer construct comprises a first peptide mask (PM1), a first mature cytokine protein (CPI), a first and a third cleavable moieties (CM1 and CM3), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CPI and the DD1, and the CM3 is positioned between the PM1 and the CPI; and (b) the second monomer construct comprises a second mature cytokine protein (CP2), a second cleavable moiety (CM2), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2; wherein the DD1 and the DD2 bind each other thereby forming a dimer of the first monomer construct and the second monomer construct; and wherein the ACC is characterized by having a reduced level of at least one CPI and / or CP2 activity as compared to a control level of the at least one CPI and / or CP2 activity. In some embodiments, the second monomer construct further comprises a second peptide mask (PM2) and a fourth cleavable moiety (CM4), wherein the CM4 is positioned between the PM2 and the CP2. In some embodiments, the first monomer construct comprises a first polypeptide that comprises the PM1, the CM3, the CPI, the CM1, and the DD1. In some embodiments, the second monomer construct comprises a second polypeptide that comprises the CP2, the CM2, and the DD2. In some embodiments, the second monomer construct comprises a second polypeptide that comprises the PM2, the CM4, the CP2, the CM2, and the DD2. In some embodiments, the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299-336, and the CPI is an interferon; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299-332, and the CPI is an interferon a; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 299-328, and 330-332, and the CPI is an interferon P; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 299-328, and 333-336, and the CPI is an interferon y; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 337-341, and the CPI is an IL-12; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 342-349, 436-444, and 445, and the CPI is an IL-15; the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 350-435, and 436-445, and the CPI is an IL-2; or the PM1 comprises a sequence selected from the group consisting of SEQ ID NOs: 445 and 446, and the CPI is an IL-21. In some embodiments, the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299-336, and the CP2 is an interferon; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299-364, and the CP2 is an interferon a; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 299-328, and 330-332, and the CP2 is an interferon P; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 299-328, and 333-336, and the CP2 is an interferon y; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 337-341, and the CP2 is an IL-12; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 342-349, 436-444, and 445, and the CP2 is an IL-15; the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 350-435, 436-445, and the CP2 is an IL-2; or the PM2 comprises a sequence selected from the group consisting of SEQ ID NOs: 445 and 446, and the CP2 is an IL-21. In some embodiments, the PM1 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299- 446. In some embodiments, the PM2 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 297, 298, 292, and 299-446. In some embodiments, the DD1 and the DD2 are a pair selected from the group consisting of: a pair of Fc domains, a sushi domain from an alpha chain of human IL-15 receptor (IL15Ra) and a soluble IL-15; bamase and barnstar; a protein kinase A (PKA) and an A-kinase anchoring protein (AKAP); adapter / docking tag modules based on mutated RNase I fragments; an epitope and single domain antibody (sdAb); an epitope and single chain variable fragment (scFv); and soluble N-ethyl-maleimide sensitive factor attachment protein receptors (SNARE) modules based on interactions of the proteins syntaxin, synaptotagmin, synaptobrevin, and SNAP25, an antigen-binding domain and an epitope. In some embodiments, the DD1 and the DD2 are a pair of Fc domains. In some embodiments, the pair of Fc domains is a pair of human Fc domains. In some embodiments, the human Fc domains are human IgGl Fc domains, human IgG2 Fc domains, human IgG3 Fc domains, or human IgG4 Fc domains. In some embodiments, the human Fc domains are human IgG4 Fc domains. In some embodiments, the human Fc domains each comprise a sequence that is at least 80% identical to SEQ ID NO: 3. In some embodiments, the human Fc domains each comprise a sequence that is at least 90%, 95%, 96%, 97%, 98%, or 99% identical to SEQ ID NO: 3. In some embodiments, the human Fc domains comprise SEQ ID NO: 3. In some embodiments, the DD1 and the DD2 comprise SEQ ID NOs: 287 and 288, respectively. In some embodiments, the DD1 and the DD2 are the same. In some embodiments, the human Fc domains include mutations to eliminate glycosylation and / or to reduce Fc-gamma receptor binding. In some embodiments, the human Fc domains comprise the mutation N297Q, N297A, or N297G; in some embodiments the human Fc domains comprise a mutation at postion 234 and / or 235, for example L235E, or L234A and L235A (in IgGl), or F234A and L235A (in IgG4); in some embodiments the human Fc domains are IgG2 Fc domains that comprise the mutations V234A, G237A, P238S, H268Q / A, V309L, A330S, or P331S, or a combination thereof (all according to EU numbering). Additional examples of engineered human Fc domains are known to those skilled in the art. Examples of Ig heavy chain constant region amino acids in which mutations in at least one amino acid leads to reduced Fc function include, but are not limited to, mutations in amino acid 228, 233, 234, 235, 236, 237, 239, 252, 254, 256, 265, 270, 297, 318, 320, 322, 327, 329, 330, and 331 of the heavy constant region (according to EU numbering). Examples of combinations of mutated amino acids are also known in the art, such as, but not limited to a combination of mutations in amino acids 234, 235, and 331, such as L234F, L235E, and P331S or a combination of amino acids 318, 320, and 322, such as E318A, K320A, and K322A. Further examples of engineered Fc domains include F243L / R292P / Y300L / V305I / P396 IgGl; S239D / I332E IgGl; S239D / I332E / A330L IgGl; S298A / E333A / K334A; in one heavy chain, L234Y / L235Q / G236W / S239M / H268D / D270E / S298A IgGl, and in the opposing heavy chain, D270E / K326D, A330M / K334E IgG; G236A / S239D / I332E IgGl; K326W / E333S IgGl; S267E / H268F / S324T IgGl; E345R / E430G / S440Y IgGl; N297A or N297Q or N297G IgGl; L235E IgGl; L234A / L235A IgGl; F234A / L235A IgG4; H268Q / V309L / A330S / P331S IgG2; V234A / G237A / P238S / H268A / V309L / A330S / P331S IgG2; M252Y / S254T / T256E IgGl; M428L / N434S IgGl; S267E / L328F IgGl; N325S / L328F IgGl, and the like. In some embodiments, the engineered Fc domain comprises one or more substitutions selected from the group consisting of N297A IgGl, N297Q IgGl, and S228P IgG4. In some embodiments, the DD1 comprises an antigen-binding domain and the DD2 comprises a corresponding epitope. In some embodiments, the antigen-binding domain is an anti-His tag antigen-binding domain and wherein the DD2 comprises a His tag. In some embodiments, the antigen-binding domain is a single chain variable fragment (scFv). In some embodiments, the antigen-binding domain is a single domain antibody (sdAb). In some embodiments, at least one of the DD1 and the DD2 comprises a dimerization domain substituent selected from the group consisting of a non-polypeptide polymer and a small molecule. In some embodiments, the DD1 and the DD2 comprise non-polypeptide polymers covalently bound to each other. In some embodiments, the non-polypeptide polymer is a sulfur-containing polyethylene glycol, and wherein the DD1 and the DD2 are covalently bound to each other via one or more disulfide bonds. In some embodiments, at least one of the DD1 and the DD2 comprises a small molecule. In some embodiments, the small molecule is biotin. In some embodiments, the DD1 comprises biotin and the DD2 comprises an avidin. In some embodiments, the CPI and the CP2 are mature cytokines. In some embodiments, each of the CPI and the CP2 comprise a mature cytokine sequence and further comprise a signal peptide. A signal peptide is also referred to herein as a “signal sequence.” In some embodiments, the CPI and / or the CP2 is / are each individually selected from the group consisting of: an interferon, an interleukin, GM-CSF, G-CSF, LIF, OSM, CD154, LT-p, TNF-a, TNF-p, 4-1BBL, APRIL, CD70, CD153, CD178, GITRL, LIGHT, OX40L, TALL-1, TRAIL, TWEAK, TRANCE, TGF-pl, TGF-pl, TGF-P3, Epo, Tpo, Flt-3L, SCF, M-CSF, and MSP, optionally wherein the CPI and / or the CP2 is independently selected from IL-2, IL-7, IL-8, IL-10, IL-12, IL-15, IL-21, an IFN-alpha, an IFN beta, an IFN gamma, GM-CSF, TGF-beta, LIGHT, GITR-L, CD40L, CD27L, 4-1BB-L, OX40, and OX40L. In some embodiments, the CPI and the CP2 are the same. In some embodiments, the CPI and the CP2 are different. In some embodiments, the CPI and / or the CP2 is / are an interferon. In some embodiments, the CPI and the CP2 both are an interferon. In some embodiments, the CPI and the CP2 are different interferons. In some embodiments, the CPI and the CP2 are the same interferon. In some embodiments, one of the CPI or the CP2 is an interferon, and the other of CPI or CP2 is a cytokine other than an interferon. In some aspects, one or both cytokines are monomeric cytokines. In some aspects, one or both interferons are monomeric inteferons. In some aspects, either CPI or CP2 is a monomeric interferon and the other CPI or CP2 is a different cytokine. In some aspects, the CPI and / or the CP2 include a mutant cytokine sequence. In some aspects, the CPI and / or the CP2 include a universal cytokine sequence. In some aspects, the CPI and / or the CP2 include a truncated sequence that retains cytokine activity. In some embodiments, the interferon(s) is / are a human wildtype mature interferon. In some embodiments, the interferon(s) may be type I and type II interferons, for example including, but not limited to interferon-alpha, interferon-beta, interferongamma, interferon-omega, and interferon-tau. In some embodiments, the interferons is / are an interferon-alpha. In some embodiments, the interferon(s) is / are selected from the group consisting of: interferon alpha-2a, interferon alpha-2b, and interferon alpha-n3. In some embodiments, the interferon(s) is / are interferon alpha-2b. In some embodiments, the interferon(s) is / are a mutant interferon. In some embodiments, the interferon(s) is / are a mutant interferon wherein an endogenous protease cleavage site has been rendered disfunctional by substitution, deletion, or insertion of one or more amino acids. In some embodiments, the interferon(s) is / are a universal cytokine molecule, e.g., having a hybrid sequence of different cytokine subtypes or a chimeric cytokine sequence or a humanized cytokine sequence. In some embodiments, the interferon(s) is / are a universal interferon molecule. In some embodiments, the interferon(s) is / are a universal interferon alpha, e.g., a hybrid of interferon alpha 1 and interferon alpha 2a. In some embodiments, the CPI and / or the CP2 comprises a sequence that is at least 80% identical to SEQ ID NO: 1. In some embodiments, the CPI and / or the CP2 comprises a sequence that is at least 90%, 95%, 96%, 97%, 98%, or 99% identical to SEQ ID NO: 1. In some embodiments, the CPI and / or the CP2 comprises a sequence of SEQ ID NO: 1. In some embodiments, the interferon is an interferon beta. In some embodiments, the interferon beta is selected from the group consisting of interferon beta-la, and interferon beta-lb. In some embodiments, the CPI and / or the CP2 comprises an IFab domain. In some embodiments, the CPI and / or the CP2 comprises an interleukin. In some embodiments, the interleukin is selected from the group consisting of IL-la, IL-ip, IL-IRA, IL-18, IL-2, IL-4, IL-7, IL-9, IL-13, IL-15, IL-3, IL-5, IL-6, IL-11, IL-12, IL-10, IL-20, IL-14, IL-16, and IL-17. In some embodiments, the CM1 and / or the CM2 comprise a total of about 3 amino acids to about 15 amino acids. In some embodiments, the CM1 and the CM2 comprise substrates for different proteases. In some embodiments, wherein the CM1 and the CM2 comprise substrates for the same protease. In some embodiments, the protease(s) is / are selected from the group consisting of: ADAM8, ADAM9, ADAM10, ADAM12, ADAM15, ADAM17 / TACE, ADAMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, Renin, Cathepsin D, Cathepsin E, Caspase 1, Caspase 2, Caspase 3, Caspase 4, Caspase 5, Caspase 6, Caspase 7, Caspase 8, Caspase 9, Caspase 10, Caspase 14, Cathepsin B, Cathepsin C, Cathepsin K, Cathespin L, Cathepsin S, Cathepsin V / L2, Cathepsin X / Z / P, Cruzipain, Legumain, Otubain-2, KLK4, KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13, KLK14, Meprin, Neprilysin, PSMA, BMP-1, matrix metalloproteinases (e.g., MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-10, MMP- 11, MMP-12, MMP-13, MMP-14, MMP-15, MMP-16, MMP-17, MMP-19, MMP-20, MMP-23, MMP-24, MMP-26, MMP-27), activated protein C, cathepsin A, cathepsin G, Chymase, FVIIa, FIXa, FXa, FXIa, FXIIa, Elastase, Granzyme B, Guanidinobenzoatase, HtrAl, human neutrophil lyase, lactoferrin, marapsin, NS3 / 4A, PACE4, Plasmin, PSA, tPA, thrombin, tryptase, uPA, DESCI, DPP-4, FAP, Hepsin, Matriptase-2, MT-SPl / Matripase, TMPRSS2, TMPRSS3, and TMPRSS4. In some embodiments, the protease(s) is / are selected from the group consisting of: uPA, legumain, MT-SP1, ADAM 17, BMP-1, TMPRSS3, TMPRSS4, MMP-2, MMP-9, MMP-12, MMP-13, and MMP-14. Suitable cleavable moieties have been disclosed in WO 2010 / 081173, WO 2015 / 048329, WO 2015 / 116933, WO 2016 / 118629, and WO 2020 / 118109, the disclosures of which are incorporated herein by reference in their entireties. In some embodiments, the CM1 and / or the CM2 comprise a sequence selected from the group consisting of: LSGRSDNH (SEQ ID NO: 5), TGRGPSWV (SEQ ID NO: 6), PLTGRSGG (SEQ ID NO: 7), TARGPSFK (SEQ ID NO: 8), NTLSGRSENHSG (SEQ ID NO: 9), NTLSGRSGNHGS (SEQ ID NO: 10), TSTSGRSANPRG (SEQ ID NO: 11), TSGRSANP (SEQ ID NO: 12), VHMPLGFLGP (SEQ ID NO: 13), AVGLLAPP (SEQ ID NO: 14), AQNLLGMV (SEQ ID NO: 15), QNQALRMA (SEQ ID NO: 16), LAAPLGLL (SEQ ID NO: 17), STFPFGMF (SEQ ID NO: 18), ISSGLLSS (SEQ ID NO: 19), PAGLWLDP (SEQ ID NO: 20), VAGRSMRP (SEQ ID NO: 21), VVPEGRRS (SEQ ID NO: 22), ILPRSPAF (SEQ ID NO: 23), MVLGRSLL (SEQ ID NO: 24), QGRAITFI (SEQ ID NO: 25), SPRSIMLA (SEQ ID NO: 26), SMLRSMPL (SEQ ID NO: 27), ISSGLLSGRSDNH (SEQ ID NO: 28), AVGLLAPPGGLSGRSDNH (SEQ ID NO: 29), ISSGLLSSGGSGGSLSGRSDNH (SEQ ID NO: 30), LSGRSGNH (SEQ ID NO: 31), SGRSANPRG (SEQ ID NO: 32), LSGRSDDH (SEQ ID NO: 33), LSGRSDIH (SEQ ID NO: 34), LSGRSDQH (SEQ ID NO: 35), LSGRSDTH (SEQ ID NO: 36), LSGRSDYH (SEQ ID NO: 37), LSGRSDNP (SEQ ID NO: 38), LSGRSANP (SEQ ID NO: 39), LSGRSANI (SEQ ID NO: 40), LSGRSDNI (SEQ ID NO: 41), MIAPVAYR (SEQ ID NO: 42), RPSPMWAY (SEQ ID NO: 43), WATPRPMR (SEQ ID NO: 44), FRLLDWQW (SEQ ID NO: 45), ISSGL (SEQ ID NO: 46), ISSGLLS (SEQ ID NO: 47), ISSGLL (SEQ ID NO: 48), ISSGLLSGRSANPRG (SEQ ID NO: 49), AVGLLAPPTSGRSANPRG (SEQ ID NO: 50), AVGLLAPPSGRSANPRG (SEQ ID NO: 51), ISSGLLSGRSDDH (SEQ ID NO: 52), ISSGLLSGRSDIH (SEQ ID NO: 53), ISSGLLSGRSDQH (SEQ ID NO: 54), ISSGLLSGRSDTH (SEQ ID NO: 55), ISSGLLSGRSDYH (SEQ ID NO: 56), ISSGLLSGRSDNP (SEQ ID NO: 57), ISSGLLSGRSANP (SEQ ID NO: 58), ISSGLLSGRSANI (SEQ ID NO: 59), AVGLLAPPGGLSGRSDDH (SEQ ID NO: 60), AVGLLAPPGGLSGRSDIH (SEQ ID NO: 61), AVGLLAPPGGLSGRSDQH (SEQ ID NO: 62), AVGLLAPPGGLSGRSDTH (SEQ ID NO: 63), AVGLLAPPGGLSGRSDYH (SEQ ID NO: 64), AVGLLAPPGGLSGRSDNP (SEQ ID NO: 65), AVGLLAPPGGLSGRSANP (SEQ ID NO: 66), AVGLLAPPGGLSGRSANI (SEQ ID NO: 67), ISSGLLSGRSDNI (SEQ ID NO: 68), AVGLLAPPGGLSGRSDNI (SEQ ID NO: 69), GLSGRSDNHGGAVGLLAPP (SEQ ID NO: 70), GLSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 71), LSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 72), ISSGLSS (SEQ ID NO: 73), PVGYTSSL (SEQ ID NO: 74), DWLYWPGI (SEQ ID NO: 75), LKAAPRWA (SEQ ID NO: 76), GPSHLVLT (SEQ ID NO: 77), LPGGLSPW (SEQ ID NO: 78), MGLFSEAG (SEQ ID NO: 79), SPLPLRVP (SEQ ID NO: 80), RMHLRSLG (SEQ ID NO: 81), LLAPSHRA (SEQ ID NO: 82), GPRSFGL (SEQ ID NO: 83), GPRSFG (SEQ ID NO: 84), SARGPSRW (SEQ ID NO: 85), GGWHTGRN (SEQ ID NO: 86), HTGRSGAL (SEQ ID NO: 87), AARGPAIH (SEQ ID NO: 88), RGPAFNPM (SEQ ID NO: 89), SSRGPAYL (SEQ ID NO: 90), RGPATPIM (SEQ ID NO: 91), RGPA (SEQ ID NO: 92), GGQPSGMWGW (SEQ ID NO: 93), FPRPLGITGL (SEQ ID NO: 94), SPLTGRSG (SEQ ID NO: 95), SAGFSLPA (SEQ ID NO: 96), LAPLGLQRR (SEQ ID NO: 97), SGGPLGVR (SEQ ID NO: 98), PLGL (SEQ ID NO: 99), and SGRSDNI (SEQ ID NO: 100). In some embodiments, the CM comprises a sequence selected from the group consisting of: ISSGLLSGRSDNH (SEQ ID NO: 28), LSGRSDDH (SEQ ID NO: 33), ISSGLLSGRSDQH (SEQ ID NO: 54), SGRSDNI (SEQ ID NO: 100), and ISSGLLSGRSDNI (SEQ ID NO: 68). In some embodiments, the protease(s) is / are produced by a tumor in the subject, e.g., the protease(s) are produced in greater amounts in the tumor than in healthy tissues of the subject. In some embodiments, the subject has been diagnosed or identified as having a cancer. In some embodiments, the CPI and the CM1 directly abut each other in the first monomer construct. In some embodiments, the CM1 and the DD1 directly abut each other in the first monomer construct. In some embodiments, the CP2 and the CM2 directly abut each other in the second monomer construct. In some embodiments, the CM2 and the DD2 directly abut each other in the second monomer construct. In some embodiments, the first monomer contruct comprises the CPI directly abutting the CM1, and the CM1 directly abutting the DD1, wherein the CM1 comprises a sequence that is selected from the group consisting of SEQ ID Nos 5-100. In some embodiments, the second monomer contruct comprises the CP2 directly abutting the CM2, and the CM2 directly abutting the DD2, wherein the CM2 comprises a sequence that is selected from the group consisting of SEQ ID Nos 5-100. In some embodiments, the first monomer contruct comprises the CPI directly abutting the CM1, and the CM1 directly abutting the DD1, wherein the CM1 comprises a sequence that is no more than 13, 12, 11, 10, 9, 8, 7, 6, 5 or 4 amino acids in length. In some embodiments, the second monomer contruct comprises the CP2 directly abutting the CM2, and the CM2 directly abutting the DD2, wherein the CM2 comprises a sequence that is no more than 13, 12, 11, 10, 9, 8, 7, 6, 5 or 4 amino acids in length. In some embodiments, the first and second monomer construct each are configured such that the cytokine (CM1 and CM2, respectively) directly abuts a cleavable moiety (CM1 and CM2, respectively) that is no more than 10, 9, 8, 7, 6, 5, or 4 amino acids in length, and the cleavable moiety directly abuts a dimerization domain (DD1 and DD2, respectively) that is the Fc region of a human IgG, wherein the N-terminus of the Fc region is the first cysteine residue (reading in the N- to C- direction) in the hinge region that participates in a disulfide linkage with a second Fc domain (e.g., Cysteine 226 of human IgGl, using EU numbering). In some aspects, the dimerization domain is an IgG Fc region wherein the upper hinge residues have been deleted. For example, the Fc is a variant wherein N-terminal sequences EPKSCDKTHT (SEQ ID NO: 522), ERK, ELKTPLGDTTHT (SEQ ID NO: 523), or ESKYGPP (SEQ ID NO: 524 have been deleted. In some embodiments, the first monomer construct comprises at least one linker. In some embodiments, the at least one linker is a linker LI disposed between the PM1 and the CM3 and / or a linker L2 disposed between the CM3 and the CPI. In some embodiments, the second monomer construct comprises at least one linker. In some embodiments, the at least one linker is a linker L3 disposed between the PM2 and the CM4 and / or a linker L4 disposed between the CM4 and the CP2. In some embodiments, the first monomer construct comprises a linker LI and the second monomer construct comprises a linker L3. In some embodiments, LI and L3 are the same. In some embodiments, the first monomer construct comprises a linker L2 and the second monomer construct comprises a linker L4. In some embodiments, L2 and L4 are the same. In some embodiments, the first monomer construct comprises a linker between the CPI and CM1 and / or a linker between the CM1 and the DDL In some embodiments, the second monomer construct comprises a linker between the CP2 and the CM2 and / or a linker between the CM2 and the DD2. In some embodiments, each linker has a total length of 1 amino acid to about 15 amino acids. In some embodiments, each linker has a total length of at least 5 amino acids. In some embodiments, the first monomer construct comprises at least one linker, wherein each linker is independently selected from from the group consisting of GSSGGSGGSGG (SEQ ID NO: 210); GGGS (SEQ ID NO: 2); GGGSGGGS (SEQ ID NO: 211); GGGSGGGSGGGS (SEQ ID NO: 212); GGGGSGGGGSGGGGS (SEQ ID NO: 213); GGGGSGGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214); GGGGSGGGGS (SEQ ID NO: 215); GGGGS (SEQ ID NO: 216); GS; GGGGSGS (SEQ ID NO: 217); GGGGSGGGGSGGGGSGS (SEQ ID NO: 218); GGSLDPKGGGGS (SEQ ID NO: 219); PKSCDKTHTCPPCPAPELLG (SEQ ID NO: 220); SKYGPPCPPCPAPEFLG (SEQ ID NO: 221); GKSSGSGSESKS (SEQ ID NO: 222); GSTSGSGKSSEGKG (SEQ ID NO: 223); GSTSGSGKSSEGSGSTKG (SEQ ID NO: 224); GSTSGSGKPGSGEGSTKG (SEQ ID NO: 225); GSTSGSGKPGSSEGST (SEQ ID NO: 226); (GS)n, (GGS)n, (GSGGS)n (SEQ ID NO: 227), (GGGS)n (SEQ ID NO: 228), (GGGGS)n (SEQ ID NO: 216), wherein each n is an integer of at least one; GGSG (SEQ ID NO: 229); GGSGG (SEQ ID NO: 230); GSGSG (SEQ ID NO: 231; GSGGG (SEQ ID NO: 232); GGGSG (SEQ ID NO: 233); GSSSG (SEQ ID NO: 234); GGGGSGGGGSGGGGS (SEQ ID NO: 213); GGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214); and GSTSGSGKPGSSEGST (SEQ ID NO: 226). In some embodiments, the linker comprises a sequence of GGGS (SEQ ID NO: 2). In some embodiments, the first monomer construct, comprises in an N- to C-terminal direction, the PM1, the CM3, the CPI, the CM1, and, linked directly or indirectly to the C-terminus of the CM1, the DD1. In some embodiments, the first polypeptide comprises in a C- to N-terminal direction, the PM1, the CM3, the CPI, the CM1, and, linked directly or indirectly to the N-terminus of the CM1, the DD1. In some embodiments, the second polypeptide comprises in a N- to C-terminal direction, the PM2, the CM4, the CP2, the CM2, and, linked directly or indirectly to the C-terminus of the CM2, the DD2. In some embodiments, the second polypeptide comprises in a C- to N-terminal direction, the PM2, the CM4, the CP2, the CM2, and, linked directly or indirectly to the CM2, the DD2. In some embodiments, the first monomer construct comprises in an N- to C-terminal direction, the CPI, an optional linker, the CM1, an optional linker, and the DD1, wherein DD1 is an Fc region of an IgG, wherein the N-terminus of the Fc region is the first cysteine residue (reading in the N- to C- direction) in the hinge region that participates in a disulfide linkage with a second Fc domain (e.g., Cysteine 226 of human IgGl or IgG4, using EU numbering), and wherein the CM1 and any linker(s) interposed between the CPI and the N-terminal cysteine of DD1 (the “linking region” or “LR”) have a combined total length of no more than 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4 amino acids, preferably no more than 10 amino acids, especially preferably no more than 7 amino acids. In some such embodiments, the first monomer construct further comprises, in an N- to C- terminal direction, the PM1, an optional linker, the CM3, and an optional linker attached to the N-terminus of the CPI. In some embodiments, the second monomer construct comprises in an N- to C- terminal direction, the CP2, an optional linker, the CM2, an optional linker, and the DD2, wherein DD2 is an Fc region of an IgG, wherein the N-terminus of the Fc region is the first cysteine residue (reading in the N- to C- direction) in the hinge region that participates in a disulfide linkage with a second Fc domain (e.g., Cysteine 226 of human IgGl or IgG4, using EU numbering), and wherein the CM2 and any linker(s) interposed between the CP2 and the N-terminal cysteine of the DD2 (the “linking region” or “LR”) have a combined total length of no more than 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4 amino acids, preferably no more than 10 amino acids, especially preferably no more than 7 amino acids. In some such embodiments, the second monomer construct further comprises, in an N- to C-terminal direction, the PM2, an optional linker, the CM4, and an optional linker attached to the N-terminus of the CP2. In some aspects, there is no linker or spacer between a peptide mask and a cleavable moiety. In some aspects, there is no linker or spacer between a cytokine protein and a cleavable moiety. In some aspects, there is no linker or spacer between a cleavable moiety and a dimerization domain. In some embodiments, the ACC is a homodimer in which the first monomer construct and the second monomer construct are identical and comprise the amino acid sequence of SEQ ID NO: 290. In some embodiments, the first monomer construct and the second monomer construct each comprise an amino acid sequence that is at least 90%, 95%, 96%, 97%, 98%, or 99% identical to SEQ ID NO: 290. In some embodiments, the ACC is a homodimer in which the first monomer construct and the second monomer construct are identical and comprise the amino acid sequence of SEQ ID NO: 290 without the N-terminal spacer sequence (QSGQ). In some embodiments, the first monomer construct and the second monomer construct each comprise, in an N- to C-terminal direction, SEQ ID NO: 292; an optional flexible linker of zero to 10 amino acids; a CM comprising an amino acid sequence selected from the group consisting of SEQ ID NO: 41, SEQ ID NO: 68, and SEQ ID NO: 100; an optional flexible linker of zero to 10 amino acids; SEQ ID NO:1; a second CM comprising an amino acid sequence selected from the group consisting of SEQ ID NO: 41, SEQ ID NO: 68, and SEQ ID NO: 100; and a dimerization domain. In some embodiments, the at least one CPI and / or CP2 activity is a binding affinity of the CPI and / or the CP2 for its cognate receptor as determined using surface plasmon resonance. For example, where the CPI or CP2 is an interferon, the cognate receptor may be the interferon-alpha / beta receptor (IFNAR). In some embodiments, the at least one CPI and / or CP2 activity is a level of proliferation of lymphoma cells. In some embodiments, the at least one CPI and / or CP2 activity is the level of JAK / STAT / ISGF3 pathway activation in a lymphoma cell. In some embodiments, the at least one activity is a level of secreted alkaline phosphatase (SEAP) production in a lymphoma cell. In some embodiments, the ACC is characterized by at least a 2-fold reduction in at least one of the CPI and the CP2 activity as compared to the control level. In some embodiments, the ACC is characterized by at least a 5-fold, 10-fold, 20-fold, 50fold, 100-fold, 200-fold, 300-fold, 400-fold, 500-fold, 600-fold, 700-fold, 800-fold, 900fold, 1000-fold, 1100-fold, 1200-fold, 1300-fold, 1400-fold, 1500-fold, 1600-fold, 1700fold, 1800-fold, 1900-fold, 2000-fold, 3000-fold, or 4000-fold reduction in at least one CPI and / or the CP2 activity as compared to the control level. In some embodiments, the ACC is characterized by at least a 5000-fold reduction in at least one activity of the CPI and / or the CP2 as compared to the control level. In some embodiments, the control level of the at least one activity of the CPI and / or CP2, is the activity of the CPI and / or the CP2 in the ACC following exposure of the ACC to the protease(s). In some embodiments, the control level of the at least one CPI and / or the CP2, is the corresponding the CPI and / or the CP2 activity of a corresponding wildtype mature cytokine. In some embodiments, the ACC is characterized by generating a cleavage product following exposure to the protease(s), wherein the cleavage product comprises the at least one activity of the CPI and / or the CP2. In some embodiments, the at least one activity of the CPI and / or the CP2 is anti-proliferation activity. In some embodiments, the control level is an EC50 value of the wildtype mature cytokine, and wherein ratio of EC50 (cleavage product) to EC50 (wildtype control level) is less than about 10, or less than about 9, or less than about 8, or less than about 7, or less than about 6, or less than about 5, or less than about 4, or less than about 3, or less than about 2, or less than about 1.5, or equal to about 1. In some embodiments, the EC50 of the cleavage product is approximately the same as the EC50 of the wildtype mature cytokine, demonstrating that the following cleavage, the activity of the CPI and / or CP2 is fully recovered, or nearly fully recovered. In some aspects, the ACCs include: (a) a first monomer comprising a first mature cytokine protein (CPI), a first cleavable moiety (CM1), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CPI and the DD1; and (b) a second monomer comprising a second mature cytokine protein (CP2), a second cleavable moiety (CM2), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2, where: the CM1 and the CM2 function as a substrate for a protease; the DD1 and the DD2 bind each other; and where the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. The protease(s) that cleave the CM1 and CM2 may be over-expressed in diseased tissue (e.g., tumor tissue) relative to healthy tissue. The ACC may be activated upon cleavage of the CM1 and / or CM2 so that the cytokine may exert its activity in the diseased tissue (e.g., in a tumor microenvironment) while the cytokine activity is attenuated in the context of healthy tissue. Provided herein are activatable cytokine constructs (ACC) that include a first monomer construct and a second monomer construct, wherein: (a) the first monomer construct comprises a first mature cytokine protein (CPI), a first cleavable moiety (CM1), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CPI and the DD1; and (b) the second monomer construct comprises a second mature cytokine protein (CP2), a second cleavable moiety (CM2), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2; wherein the DD1 and the DD2 bind each other thereby forming a dimer of the first monomer construct and the second monomer construct; and wherein the ACC is characterized by having a reduced level of at least one CPI and / or CP2 activity as compared to a control level of the at least one CPI and / or CP2 activity. The present disclosure provides activatable cytokine constructs (ACCs) that include: (a) a first monomer comprising a first mature cytokine protein (CPI), a first dimerization domain (DD1); and (b) a second monomer comprising a second mature cytokine protein (CP2), a cleavable moiety (CM), and a second dimerization domain (DD2), wherein the CM is positioned between the CP2 and the DD2, where: the CM functions as a substrate for a protease; the DD1 and the DD2 bind each other; and where the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. The present disclosure provides activatable cytokine constructs (ACCs) that include: (a) a first monomer comprising a first mature cytokine protein (CPI), a cleavable moiety (CM), and a first dimerization domain (DD1), wherein the CM is positioned between the CPI and the DD1; and (b) a second monomer comprising a second mature cytokine protein (CP2), and a second dimerization domain (DD2), where: the CM functions as a substrate for a protease; the DD1 and the DD2 bind each other; and where the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. The present disclosure provides activatable cytokine constructs (ACCs) that include: (a) a first monomer comprising a first mature cytokine protein (CPI), and a first dimerization domain (DD1); and (b) a second monomer comprising a second mature cytokine protein (CP2), and a second dimerization domain (DD2), wherein the CPI, the CP2, or both CPI and CP2 include(s) an amino acid sequence that functions as a substrate for a protease; the DD1 and the DD2 bind each other; and where the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. Thus, the ACCs of the present disclosure do not require that CPI and CP2 are connected to peptide masks, for example, affinity masking moieties; such peptide masks are an optional feature of certain ACCs of the present disclosure. In some embodiments, the ACC is administered in combination with a PD-l / PD-L1 pathway inhibitor. The disclosure provides inhibitors that specifically bind programmed cell death protein 1 (PD-1), also known as CD279, SLEB2, and / or hSLEl, and inhibitors that specifically bind programmed death-ligand 1, also known as cluster of differentiation 274 or B7 homolog 1 and / or B7-H1. The use of the term “PD-1” or “PD-Ll” is intended to cover any variation thereof, such as, by way of non-limiting example, PD1 and / or PD-1 and PDL1 and / or PD-L1, all variations are used herein interchangeably. In some embodiments, the ACC that is administered in combination with the PD-1 / PD-L1 pathway inhibitor comprises a CPI and / or the CP2 that is / are each individually selected from the group consisting of: an interferon, an interleukin, GM-CSF, G-CSF, LIF, OSM, CD154, LT-p, TNF-a, TNF-p, 4-1BBL, APRIL, CD70, CD153, CD178, GITRL, LIGHT, OX40L, TALL-1, TRAIL, TWEAK, TRANCE, TGF-pl, TGF-pl, TGF-P3, Epo, Tpo, Flt-3L, SCF, M-CSF, and MSP, optionally wherein the CPI and / or the CP2 is independently selected from IL-2, IL-7, IL-8, IL-10, IL-12, IL-15, IL-21, an IFN-alpha, an IFNbeta, an IFN gamma, GM-CSF, TGF-beia, LIGHT, (UTk-L CD40L. CD27L, 4-lBB-L, OX40, and OX40L. In preferred embodiments, CPI and / or the CP2 is / are each individually selected from an interferon as described above. In more preferred embodiments, the ACC that is administered in combination with the PD-1 / PD-L1 pathway inhibitor comprises a CPI and CP2 that are each interferon alpha-2b. In some embodiments, the PD-1 / PD-L1 pathway inhibitor is an antibody or antigen-binding fragment thereof that specifically binds PD-1 or PD-L1. In some embodiments, the antibody or antigen-binding fragment thereof that binds PD-1 or PD-L1 is a monoclonal antibody, domain antibody, single chain, Fab fragment, a F(ab')2 fragment, a scFv, a scAb, a dAb, a single domain heavy chain antibody, or a single domain light chain antibody. In some embodiments, such an antibody or antigenbinding fragment thereof that binds PD-1 or PD-L1 is a mouse, other rodent, chimeric, humanized or fully human monoclonal antibody. In some embodiments, the antibody includes an isolated antibody or antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 or PD-L1, wherein the AB has one or more of the characteristics selected from the group consisting of: (a) the AB inhibits binding of mammalian PD-1 to mammalian PDL1. In some embodiments, the PD-1 / PD-L1 pathway inhibitor is an activatable antibody. In some embodiments, the antibody includes an isolated antibody or antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 or PD-L1, wherein the AB has one or more of the characteristics selected from the group consisting of: (a) the AB inhibits binding of mammalian PD-1 to mammalian PDL1 with an EC50 value less than 5 nM; (b) the AB inhibits binding of mammalian PD-1 to mammalian PDL2 with an EC50 value less than 5 nM; and (c) the AB specifically binds to human PD-1 and cynomolgus monkey PD-1. In some embodiments, the antibody specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant of 0.01 nM to 5 nM, 0.05 nM to 5 nM, 0.1 nM to 5 nM, 0.2 nM to 5 nM, 0.3 nM to 5 nM, 0.4 nM to 5 nM, 0.5 nM to 5 nM, 0.75 nM to 5 nM, 1 nM to 5 nM, 2 nM to 5 nM, 0.01 nM to 2 nM, 0.05 nM to 2 nM, 0.1 nM to 2 nM, 0.2 nM to 2 nM, 0.3 nM to 2 nM, 0.4 nM to 2 nM, 0.5 nM to 2 nM, 0.75 nM to 1 nM, 1 nM to 2 nM, 0.01 nM to 1 nM, 0.05 nM to 1 nM, 0.1 nM to 1 nM, 0.2 nM to 1 nM, 0.3 nM to 1 nM, 0.4 nM to 1 nM, 0.5 nM to 1 nM, 0.75 nM to 1 nM, 0.01 nM to 0.75 nM, 0.05 nMto 0.75 nM, 0.1 nMto 0.75 nM, 0.2 nMto 0.75 nM, 0.3 nMto 0.75 nM, 0.4 nM to 0.75 nM, 0.5 nM to 0.75 nM, 0.01 nM to 0.5 nM, 0.05 nM to 0.5 nM, 0.1 nM to 0.5 nM, 0.2 nM to 0.5 nM, 0.3 nM to 0.5 nM, 0.4 nM to 0.5 nM, 0.01 nM to 0.4 nM, 0.05 nM to 0.4 nM, 0.1 nM to 0.4 nM, 0.2 nM to 0.4 nM, 0.3 nM to 0.4 nM, 0.01 nM to 0.3 nM, 0.05 nMto 0.3 nM, 0.1 nMto 0.3 nM, 0.2 nMto 0.3 nM, 0.01 nMto 0.2 nM, 0.05 nM to 0.2 nM, 0.1 nM to 0.2 nM, 0.01 nM to 0.1 nM, 0.05 nM to 0.1 nM, or 0.01 nM to 0.05 nM. In some embodiments, the mammalian PD-1 / PD-L1 is selected from the group consisting of a human PD-1 / PD-L1 and a cynomolgus monkey PD-1 / PD-L1. In some embodiments, the mammalian PD-1 / PD-L1 is a murine PD-1 / PD-L1. In some embodiments, the antibody specifically binds to human PD-1 / PD-L1 or cynomolgus monkey PD-1 / PD-L1 with a dissociation constant of less than or equal to 1 nM. In some embodiments, the mammalian PD-1 / PD-L1 is a human PD-1 / PD-L1. In some embodiments, the antibody or antigen binding fragment thereof specifically binds to the mammalian PD-1 or PD-Llwith a dissociation constant is less than or equal to 0.01 nM, less than or equal to 0.05 nM, less than or equal to 0.1 nM, less than or equal to 0.2 nM, less than or equal to 0.3 nM, less than or equal to 0.4 nM, less than or equal to 0.5 nM, less than or equal to 0.75 nM, and less than or equal to 1 nM. In some embodiments, the antibody has one or more of the characteristics selected from the group consisting of: (a) the AB specifically binds human PD-1 or PD-L1 and cynomolgus monkey PD-1 or PD-L1; (b) the AB inhibits binding of human PDL1 and human PDL2 to human PD-1; (c) the AB inhibits binding of cynomolgus monkey PDL1 and cynomolgus monkey PDL2 to cynomolgus monkey PD-1; (d) the AB specifically binds to murine PD-1; and (e) the AB inhibits binding of murine PDL1 and murine PDL2 to murine PD-1. In some embodiments, the antibody blocks the ability of a natural ligand to bind to the mammalian PDL1 with an EC50 of 0.1 nM to 10 nM, 0.1 nM to 5 nM, 0.1 nM to 3 nM, 0.1 nM to 2 nM, 0.1 nM to 1 nM, 0.1 nM to 0.5 nM, 0.1 nM to 0.25 nM, 0.25 nM to 10 nM, 0.25 nM to 5 nM, 0.25 nM to 3 nM, 0.25 nM to 2 nM, 0.25 nM to 1 nM, 0.25 nM to 0.5 nM, 0.5 nM to 10 nM, 0.5 nM to 5 nM, 0.5 nM to 3 nM, 0.5 nM to 2 nM, 0.5 nM to 1 nM, 1 nM to 10 nM, 1 nM to 5 nM, 1 nM to 3 nM, 1 nM to 2 nM, 2 nM to 10 nM, 2 nM to 5 nM, 2 nM to 3 nM, 3 nM to 10 nM, 3 nM to 5 nM, or 5 nM to 10 nM. In some embodiments, the natural ligand is a mammalian PDL1 or a mammalian PDL2. In some embodiments, the natural ligand is selected from the group consisting of: a human PDL1, a human PDL2, a cynomolgus monkey PDL1, and a cynomolgus monkey PDL2. In some embodiments, the natural ligand is a murine PDL1 or a murine PDL2. In some embodiments, the antibody blocks the ability of a natural ligand to bind to the mammalian PDL1 with an EC50 of less than or equal to 0.1 nM, less than or equal to 0.25 nM, less than or equal to 0.5 nM, less than or equal to 1 nM, less than or equal to 2 nM, less than or equal to 3 nM, less than or equal to 4 nM, less than or equal to 5 nM or less than or equal to 10 nM. In some embodiments, the anti-PD-1 antibody includes a heavy chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 610-614 and 620-628, and a light chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 615619 and 629-639. In some embodiments, the anti-PD-1 antibody comprises a heavy chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 610-614 and 620-628 and comprises a light chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 615-619 and 629-639. In some embodiments, the anti-PD-1 antibody includes: (a) a variable heavy chain complementarity determining region 1 (VH CDR1) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 487 and 642-645; (b) a variable heavy chain complementarity determining region 2 (VH CDR2) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 488 and 646-650; (c) a variable heavy chain complementarity determining region 3 (VH CDR3) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 489 and 652655; (d) a variable light chain complementarity determining region 1 (VL CDR1) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 656-663; (e) a variable light chain complementarity determining region 2 (VL CDR2) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 491 and 664-666; and (f) variable light chain complementarity determining region 3 (VL CDR3) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 492 and 667-670. In some embodiments, the anti-PD-1 antibody includes a combination of a variable heavy chain complementarity determining region 1 (VH CDR1, also referred to herein as CDRH1) sequence, a variable heavy chain complementarity determining region 2 (VH CDR2, also referred to herein as CDRH2) sequence, and a variable heavy chain complementarity determining region 3 (VH CDR3, also referred to herein as CDRH3) sequence, wherein the VH CDR1 sequence comprises GITFSNSG (SEQ ID NO: 525); the VH CDR2 sequence comprises IWYDGSKR (SEQ ID NO: 526); and the VH CDR3 sequence comprises TNDDY (SEQ ID NO: 527). In some embodiments, the anti-PD-1 antibody includes a combination of a variable light chain complementarity determining region 1 (VL CDR1, also referred to herein as CDRL1) sequence, a variable light chain complementarity determining region 2 (VL CDR2, also referred to herein as CDRL2) sequence, and a variable light chain complementarity determining region 3 (VL CDR3, also referred to herein as CDRL3) sequence, wherein the VL CDR1 sequence comprises QSVSSY (SEQ ID NO: 528); the VL CDR2 sequence comprises DAS; and the VL CDR3 sequence comprises QQSSNWPRT (SEQ ID NO: 529). In some embodiments, the anti-PD-1 antibody includes a combination of a variable heavy chain complementarity determining region 1 (VH CDR1, also referred to herein as CDRH1) sequence, a variable heavy chain complementarity determining region 2 (VH CDR2, also referred to herein as CDRH2) sequence, and a variable heavy chain complementarity determining region 3 (VH CDR3, also referred to herein as CDRH3) sequence, wherein the VH CDR1 sequence comprises GYTFTNYY (SEQ ID NO: 530); the VH CDR2 sequence comprises INPSNGGT (SEQ ID NO: 531); and the VH CDR3 sequence comprises RRDYRFDMGFDY (SEQ ID NO: 532). In some embodiments, the anti-PD-1 antibody includes a combination of a variable light chain complementarity determining region 1 (VL CDR1, also referred to herein as CDRL1) sequence, a variable light chain complementarity determining region 2 (VL CDR2, also referred to herein as CDRL2) sequence, and a variable light chain complementarity determining region 3 (VL CDR3, also referred to herein as CDRL3) sequence, wherein the VL CDR1 sequence comprises KGVSTSGYSY (SEQ ID NO: 533); the VL CDR2 sequence comprises LAS; and the VL CDR3 sequence comprises QHSRDLPLT (SEQ ID NO: 534). In some embodiments, the anti-PD-Ll antibody a heavy chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 673-694 and a light chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NO: 671 or SEQ ID NO: 672. In some embodiments, the anti-PD-Ll antibody comprises a heavy chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 673-694 and comprises a light chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NO: 671 or SEQ ID NO: 672. In some embodiments, the anti-PD-Ll antibody comprises a combination of a VH CDR1 sequence, a VH CDR2 sequence, a VH CDR3 sequence, a VL CDR1 sequence, a VL CDR2 sequence, and a VL CDR3 sequence, wherein at least one CDR sequence is selected from the group consisting of a VL CDR1 sequence comprising RASQSISSYLN (SEQ ID NO: 535); a VL CDR2 sequence comprising AASSLQS (SEQ ID NO: 536); a VL CDR3 sequence comprising DNGYPST (SEQ ID NO: 537); a VH CDR1 sequence comprising SYAMS (SEQ ID NO: 538); a VH CDR2 sequence comprising SSIWRNGIVTVYADS (SEQ ID NO: 539); and a VH CDR3 sequence comprising WSAAFDY (SEQ ID NO: 540). In some embodiments, the PD-1 / PD-L1 pathway inhibitor is selected from the group consisting of nivolumab, pembrolizumab, tislelizumab, spartalizumab, camrelizumab, cetrelimab, cemiplimab, Balstilimab, Dostarlimab, Prolgolimab, Sasanlimab, zimberelimab, Atezolizumab, Avelumab, Durvalumab, adebrelimab, Lodapolimab, Envafolimab, Cosibelimab, budigalimab, ezabenlimab, fmotonlimab, geptanolimab, lodapolimab, penpulimab, pimivalimab, pucotenlimab, serplulimab, Sintilimab, toripalimab, zeluvalimab, iparomlimab, nofazinlimab, rulonilimab, garivulimab, manelimab, opucolimab, pacmilimab (CX-072), sudubrilimab, sugemalimab, socazolimab, and tagitanlimab. In some embodiments, the PD1 / PD-L1 pathway inhibitor comprises pacmilimab (CX-072 (SEQ ID NO: 485-HC, SEQ ID NO: 496-LC); CX-075 (SEQ ID NO: 485-HC, SEQ ID NO: 497-LC), CX-171 (SEQ ID NOs: 504 or 505- HC, SEQ ID NO: 506- LC), or CX-188 (SEQ ID NO: 483-HC, SEQ ID NO: 484-LC). The disclosure also provides activatable antibodies that include an antibody or antigen-binding fragment thereof that specifically binds PD-1 or PD-L1 coupled to a masking moiety (MM), such that coupling of the MM reduces the ability of the antibody or antigen-binding fragment thereof to bind PD-1 or PD-L1. In some embodiments, the MM is coupled via a cleavable moiety (CM) that includes sequence that functions as a substrate for a protease. The activatable anti-PD- 1 or anti-PD-Ll antibodies of the disclosure are activated when the cleavable moiety is cleaved by a protease. For example, the protease is produced by a tumor that is in proximity to T cells that express PD- 1 or PD-L1. In some embodiments, the protease is produced by a tumor that is co-localized with T cells that express PD-1 or PD-L1. The activatable anti-PD-1 or anti-PD-Ll antibodies provided herein, also referred to herein as anti-PD-1 or anti-PD-Ll activatable antibodies or PD-1 and anti-PD-Ll activatable antibodies, are stable in circulation, activated at intended sites of therapy and / or diagnosis but not in normal, e.g., healthy tissue or other tissue not targeted for treatment and / or diagnosis, and, when activated, exhibit binding to PD-1 or PD-L1 that is at least comparable to the corresponding, unmodified antibody. The invention also provides methods of treating, preventing and / or delaying the onset or progression of, or alleviating a symptom associated with aberrant expression and / or activity of PD-1 or PD-L1 in a subject using antibodies or activatable antibodies that bind PD-1 or PD-L1, particularly activatable antibodies that bind and neutralize or otherwise inhibit at least one biological activity of PD-1 or PD-L1, alone or in combination with an activatable cytokine such as an activatable interferon. In some embodiments, the activatable anti-PD-1 or anti-PD-Ll antibody comprises an activatable antibody that, in an activated state, specifically binds to mammalian PD-1 or PD-L1, wherein said activatable antibody comprises: an antibody or an antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 or anti-PD-Ll; a masking moiety (MM) that inhibits the binding of the AB to mammalian PD-1 or PD-L1 when the activatable antibody is in an uncleaved state; and a cleavable moiety (CM) coupled to the AB, wherein the CM is a polypeptide that functions as a substrate for a protease. In some embodiments, the activatable anti-PD-1 or anti-PD-Ll antibody comprises an activatable antibody that, in an activated state, (a) specifically binds to mammalian PD-1 or PD-L1; and (b) specifically blocks a natural ligand of PD-1 from binding to the mammalian PD-1, wherein the activatable antibody comprises: an antibody or an antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 or PD-L1; a masking moiety (MM) that inhibits the binding of the AB to mammalian PD-1 or PD-L1 when the activatable antibody is in an uncleaved state; and a cleavable moiety (CM) coupled to the AB, wherein the CM is a polypeptide that functions as a substrate for a protease. In some embodiments, the activatable antibody in an uncleaved state specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant of 0.5 nM to 1 nM, 0.5 nM to 2 nM, 0.5 nM to 5 nM, 0.5 nM to 10 nM, 0.5 nM to 15 nM, 0.5 nM to 20 nM, 0.5 nM to 25 nM, 0.5 nM to 50 nM, 0.5 nM to 75 nM, 0.5 nM to 100 nM, 0.5 nM to 150 nM, 0.5 nM to 200 nM, 0.5 nM to 300 nM, 0.5 nM to 400 nM, 1 nM to 2 nM, 1 nM to 5 nM, 1 nM to 10 nM, 1 nM to 15 nM, 1 nM to 20 nM, 1 nM to 25 nM, 1 nM to 50 nM, 1 nM to 75 nM, 1 nM to 100 nM, 1 nM to 150 nM, 1 nM to 200 nM, 1 nM to 300 nM, 1 nM to 400 nM, 2 nM to 5 nM, 2 nM to 10 nM, 2 nM to 15 nM, 2 nM to 20 nM, 2 nM to 25 nM, 2 nM to 50 nM, 2 nM to 75 nM, 2 nM to 100 nM, 2 nM to 150 nM, 2 nM to 200 nM, 2 nM to 300 nM, 2 nM to 400 nM, 5 nM to 10 nM, 5 nM to 15 nM, 5 nM to 20 nM, 5 nM to 25 nM, 5 nM to 50 nM, 5 nM to 75 nM, 5 nM to 100 nM, 5 nM to 150 nM, 5 nM to 200 nM, 5 nM to 300 nM, 5 nM to 400 nM, 10 nM to 15 nM, 10 nM to 20 nM, 10 nM to 25 nM, 10 nM to 50 nM, 10 nM to 75 nM, 10 nM to 100 nM, 10 nM to 150 nM, 10 nM to 200 nM, 10 nM to 300 nM, 10 nM to 400 nM, 15 nM to 20 nM, 15 nM to 25 nM, 15 nM to 50 nM, 15 nM to 75 nM, 15 nM to 100 nM, 15 nM to 150 nM, 15 nM to 200 nM, 15 nM to 300 nM, 15 nM to 400 nM, 20 nM to 25 nM, 20 nM to 50 nM, 20 nM to 75 nM, 20 nM to 100 nM, 20 nM to 150 nM, 20 nM to 200 nM, 20 nM to 300 nM, 20 nM to 400 nM, 25 nM to 50 nM, 25 nM to 75 nM, 25 nM to 100 nM, 25 nM to 150 nM, 25 nM to 200 nM, 25 nM to 300 nM, 25 nM to 400 nM, 50 nM to 75 nM, 50 nM to 100 nM, 50 nM to 150 nM, 50 nM to 200 nM, 50 nM to 300 nM, 50 nM to 400 nM, 75 nM to 100 nM, 75 nM to 150 nM, 75 nM to 200 nM, 75 nM to 300 nM, 75 nM to 400 nM, 100 nM to 150 nM, 100 nM to 200 nM, 100 nM to 300 nM, 100 nM to 400 nM, 150 nM to 200 nM, 150 nM to 300 nM, 150 nM to 400 nM, 200 nM to 300 nM, 200 nM to 400 nM, or 300 nM to 400 nM. In some embodiments, the activatable antibody in an activated state specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant of 0.01 nM to 5 nM, 0.05 nM to 5 nM, 0.1 nM to 5 nM, 0.2 nM to 5 nM, 0.3 nM to 5 nM, 0.4 nM to 5 nM, 0.5 nM to 5 nM, 0.75 nM to 5 nM, 1 nM to 5 nM, 2 nM to 5 nM, 0.01 nM to 2 nM, 0.05 nM to 2 nM, 0.1 nM to 2 nM, 0.2 nM to 2 nM, 0.3 nM to 2 nM, 0.4 nM to 2 nM, 0.5 nM to 2 nM, 0.75 nM to 1 nM, 1 nM to 2 nM, 0.01 nM to 1 nM, 0.05 nM to 1 nM, 0.1 nM to 1 nM, 0.2 nM to 1 nM, 0.3 nM to 1 nM, 0.4 nM to 1 nM, 0.5 nM to 1 nM, 0.75 nM to 1 nM, 0.01 nMto 0.75 nM, 0.05 nMto 0.75 nM, 0.1 nMto 0.75 nM, 0.2 nMto 0.75 nM, 0.3 nM to 0.75 nM, 0.4 nM to 0.75 nM, 0.5 nM to 0.75 nM, 0.01 nM to 0.5 nM, 0.05 nM to 0.5 nM, 0.1 nMto 0.5 nM, 0.2 nMto 0.5 nM, 0.3 nMto 0.5 nM, 0.4 nMto 0.5 nM, 0.01 nM to 0.4 nM, 0.05 nM to 0.4 nM, 0.1 nM to 0.4 nM, 0.2 nM to 0.4 nM, 0.3 nM to 0.4 nM, 0.01 nMto 0.3 nM, 0.05 nMto 0.3 nM, 0.1 nMto 0.3 nM, 0.2 nMto 0.3 nM, 0.01 nM to 0.2 nM, 0.05 nM to 0.2 nM, 0.1 nM to 0.2 nM, 0.01 nM to 0.1 nM, 0.05 nM to 0.1 nM, or 0.01 nM to 0.05 nM. In some embodiments, the activatable antibody comprises an AB that specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant of 0.01 nM to 5 nM, 0.05 nM to 5 nM, 0.1 nM to 5 nM, 0.2 nM to 5 nM, 0.3 nM to 5 nM, 0.4 nM to 5 nM, 0.5 nM to 5 nM, 0.75 nM to 5 nM, 1 nM to 5 nM, 2 nM to 5 nM, 0.01 nM to 2 nM, 0.05 nM to 2 nM, 0.1 nM to 2 nM, 0.2 nM to 2 nM, 0.3 nM to 2 nM, 0.4 nM to 2 nM, 0.5 nM to 2 nM, 0.75 nM to 1 nM, 1 nM to 2 nM, 0.01 nM to 1 nM, 0.05 nM to 1 nM, 0.1 nM to 1 nM, 0.2 nM to 1 nM, 0.3 nM to 1 nM, 0.4 nM to 1 nM, 0.5 nM to 1 nM, 0.75 nM to 1 nM, 0.01 nMto 0.75 nM, 0.05 nMto 0.75 nM, 0.1 nMto 0.75 nM, 0.2 nMto 0.75 nM, 0.3 nM to 0.75 nM, 0.4 nM to 0.75 nM, 0.5 nM to 0.75 nM, 0.01 nM to 0.5 nM, 0.05 nM to 0.5 nM, 0.1 nMto 0.5 nM, 0.2 nMto 0.5 nM, 0.3 nMto 0.5 nM, 0.4 nMto 0.5 nM, 0.01 nM to 0.4 nM, 0.05 nM to 0.4 nM, 0.1 nM to 0.4 nM, 0.2 nM to 0.4 nM, 0.3 nM to 0.4 nM, 0.01 nMto 0.3 nM, 0.05 nMto 0.3 nM, 0.1 nMto 0.3 nM, 0.2 nMto 0.3 nM, 0.01 nM to 0.2 nM, 0.05 nM to 0.2 nM, 0.1 nM to 0.2 nM, 0.01 nM to 0.1 nM, 0.05 nM to 0.1 nM, or 0.01 nM to 0.05 nM. In some embodiments, the mammalian PD-1 or PD-L1 is selected from the group consisting of a human PD-1 or PD-L1 and a cynomolgus monkey PD-1 or PD-L1. In some embodiments, the AB specifically binds to human PD-1 or PD-L1 or cynomolgus monkey PD-1 or PD-L1 with a dissociation constant of less than or equal to 1 nM. In some embodiments, the mammalian PD-1 or PD-L1 is a human PD-1 or PD-L1. In some embodiments, the AB has one or more of the characteristics selected from the group consisting of: (a) the AB specifically binds human PD-1 or PD-L1 and cynomolgus monkey PD-1 or PD-L1; (b) the AB inhibits binding of human PDL1 and human PDL2 to human PD-1; and (c) the AB inhibits binding of cynomolgus monkey PDL1 and cynomolgus monkey PDL2 to cynomolgus monkey PD-1. In some embodiments, the mammalian PD-1 or PD-L1 is mouse PD-1 or PD-L1. In some embodiments, the activatable antibody comprises an AB that specifically binds mouse PD-1 or PD-L1 or inhibits binding of mouse PDL1 and mouse PDL2 to mouse PD1. In some embodiments, the activatable antibody in an uncleaved state specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant greater than or equal to 0.5 nM, greater than or equal to 1 nM, greater than or equal to 2 nM, greater than or equal to 3 nM, greater than or equal to 4 nM, greater than or equal to 5 nM, greater than or equal to 10 nM, greater than or equal to 15 nM, greater than or equal to 20 nM, greater than or equal to 25 nM, greater than or equal to 50 nM, greater than or equal to 75 nM, greater than or equal to 100 nM, greater than or equal to 150 nM, greater than or equal to 200 nM, greater than or equal to 300 nM and / or greater than or equal to 400 nM. In some embodiments, the activatable antibody in an activated state specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant less than or equal to 0.01 nM, less than or equal to 0.05 nM, less than or equal to 0.1 nM, less than or equal to 0.2 nM, less than or equal to 0.3 nM, less than or equal to 0.4 nM, less than or equal to 0.5 nM, less than or equal to 0.75 nM, and less than or equal to 1 nM. In some embodiments, the activatable antibody comprises an AB that specifically binds to the mammalian PD-1 or PD-L1 with a dissociation constant less than or equal to 0.01 nM, less than or equal to 0.05 nM, less than or equal to 0.1 nM, less than or equal to 0.2 nM, less than or equal to 0.3 nM, less than or equal to 0.4 nM, less than or equal to 0.5 nM, less than or equal to 0.75 nM, and less than or equal to 1 nM. In some embodiments, the activatable antibody comprises an AB blocks the ability of a natural ligand to bind to the mammalian PDL1 with an ECso of 0.1 nM to 10 nM, 0.1 nM to 5 nM, 0.1 nM to 3 nM, 0.1 nM to 2 nM, 0.1 nM to 1 nM, 0.1 nM to 0.5 nM, 0.1 nM to 0.25 nM, 0.25 nM to 10 nM, 0.25 nM to 5 nM, 0.25 nM to 3 nM, 0.25 nM to 2 nM, 0.25 nM to 1 nM, 0.25 nM to 0.5 nM, 0.5 nM to 10 nM, 0.5 nM to 5 nM, 0.5 nM to 3 nM, 0.5 nM to 2 nM, 0.5 nM to 1 nM, 1 nM to 10 nM, 1 nM to 5 nM, 1 nM to 3 nM, 1 nM to 2 nM, 2 nM to 10 nM, 2 nM to 5 nM, 2 nM to 3 nM, 3 nM to 10 nM, 3 nM to 5 nM, or 5 nM to 10 nM. In some embodiments, the natural ligand is a mammalian PDL1 or a mammalian PDL2. In some embodiments, the natural ligand is selected from the group consisting of: a human PDL1, a human PDL2, a cynomolgus monkey PDL1, and a cynomolgus monkey PDL2. The activatable antibodies in an activated state bind PD-1 or PD-L1 and include (i) an antibody or an antigen binding fragment thereof (AB) that specifically binds to PD-1 or PD-L1; (ii) a masking moiety (MM) that, when the activatable antibody is in an uncleaved state, inhibits the binding of the AB to PD-1 or PD-L1; and (c) a cleavable moiety (CM) coupled to the AB, wherein the CM is a polypeptide that functions as a substrate for a protease. In some embodiments, the activatable PD-1 or PD-L1 antibody in the uncleaved state has the structural arrangement from N-terminus to C-terminus as follows: MM-CM-AB or AB-CM- MM. In some embodiments, the activatable PD-1 or PD-L1 antibody comprises a linking peptide between the MM and the CM. In some embodiments, the activatable PD-1 or PD-L1 antibody comprises a CM as defined herein. In some embodiments, the activatable PD-1 or PD-L1 antibody comprises a linking peptide between the CM and the AB. In some embodiments, the activatable PD-1 or PD-L1 antibody comprises a first linking peptide (LP1) and a second linking peptide (LP2), and wherein the activatable antibody in the uncleaved state has the structural arrangement from N-terminus to C-terminus as follows: MM-LP1-CM- LP2-AB or AB-LP2-CM-LP1-MM. In some embodiments, the two linking peptides need not be identical to each other. In some embodiments, each of LP1 and LP2 is a peptide of about 1 to 20 amino acids in length. In some embodiments, at least one of LP1 or LP2 comprises an amino acid sequence selected from the group consisting of (GS)n, (GGS)n, (GSGGS)n (SEQ ID NO: 227) and (GGGS)n (SEQ ID NO: 228), where n is an integer of at least one. In some embodiments, at least one of LP1 or LP2 comprises an amino acid sequence selected from the group consisting of GGSG (SEQ ID NO: 229), GGSGG (SEQ ID NO: 230), GSGSG (SEQ ID NO: 231), GSGGG (SEQ ID NO: 232), GGGSG (SEQ ID NO: 233), and GSSSG (SEQ ID NO: 234). In some embodiments, LP1 comprises the amino acid sequence GSSGGSGGSGGSG (SEQ ID NO: 541), GSSGGSGGSGG (SEQ ID NO: 210), GSSGGSGGSGGS (SEQ ID NO: 542), GSSGGSGGSGGSGGGS (SEQ ID NO: 588), GSSGGSGGSG (SEQ ID NO: 543), GSSGGSGGSGS (SEQ ID NO: 544), GGGSSGGS (SEQ ID NO: 545), or GGGSSGG (SEQ ID NO: 546). In some embodiments, LP2 comprises the amino acid sequence GSS, GGS, GGGS (SEQ ID NO: 2), GSSGT (SEQ ID NO: 548) or GSSG (SEQ ID NO: 549). In some embodiments, the activatable antibody also includes a signal peptide. In some embodiments, the signal peptide is conjugated to the activatable antibody via a spacer. In some embodiments, the spacer is conjugated to the activatable antibody in the absence of a signal peptide. In some embodiments, the spacer is joined directly to the MM of the activatable antibody. In some embodiments, the spacer is joined directly to the MM of the activatable antibody in the structural arrangement from N-terminus to C-terminus of spacer-MM-CM-AB. In some embodiments, the activatable anti-PD-1 antibody includes a heavy chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 610-614 and 620-628, and a light chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 615-619 and 629-639. In some aspects, the present disclosure includes an activatable anti-PD-1 antibody disclosed in WO2017011580, which is incorporated herein by reference in its entirety. In some embodiments, the activatable anti-PD-1 antibody comprises a masking moiety (MM) comprising an amino acid sequence selected from the group consisting of AMSGCSWSAFCPYLA (SEQ ID NO: 550), DVNCAIWYSVCITVP (SEQ ID NO: 551), LVCPLYALSSGVCMG (SEQ ID NO: 552), SVNCRIWSAVCAGYE (SEQ ID NO: 553), MLVCSLQPTAMCERV (SEQ ID NO: 554), APRCYMFASYCKSQY (SEQ ID NO: 555), VGPCELTPKPVCNTY (SEQ ID NO: 556), ETCNQYERSSGLCFA (SEQ ID NO: 557), APRTCYTYQCSSFYT (SEQ ID NO: 558), GLCSWYLSSSGLCVD (SEQ ID NO: 559), VPWCQLTPRVMCMWA (SEQ ID NO: 560), NWLDCQFYSECSVYG (SEQ ID NO: 561), SCPLYVMSSFGGCWD (SEQ ID NO: 562), MSHCWMFSSSCDGVK (SEQ ID NO: 563), VSYCTWLIEVICLRG (SEQ ID NO: 564), VLCAAYALSSGICGG (SEQ ID NO: 565), TTCNLYQQSSMFCNA (SEQ ID NO: 566), APRCYMFASYCKSQY (SEQ ID NO: 567), PCDQNPYFYPYVCHA (SEQ ID NO: 568), SVCPMYALSSMLCGA (SEQ ID NO: 569), LSVECYVFSRCSSLP (SEQ ID NO: 570), FYCTYLVSLTCHPQ (SEQ ID NO: 571), SMAGCQWSSFCVQRD (SEQ ID NO: 572), IYSCYMFASRCTSDK (SEQ ID NO: 573), SRCSVYEVSSGLCDW (SEQ ID NO: 574), GMCSAYAYSSKLCTI (SEQ ID NO: 575), MTTNTCNLLCQQFLT (SEQ ID NO: 576), FQPCLMFASSCFTSK (SEQ ID NO: 577), WNCHPAGVGPVFCEV (SEQ ID NO: 578), ALCSMYLASSGLCNK (SEQ ID NO: 579), NYLSCQFFQNCYETY (SEQ ID NO: 580), GWCLFSDMWLGLCSA (SEQ ID NO: 581), EFCARDWLPYQCSSF (SEQ ID NO: 582), TSYCSIEHYPCNTHH (SEQ ID NO: 583). In some embodiments, the activatable anti-PD-1 antibody comprises a heavy chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 610-614 and 620-628 and comprises a light chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 615-619 and 629-639. In some embodiments, the activatable anti-PD-1 antibody includes: (a) a variable heavy chain complementarity determining region 1 (VH CDR1) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 487 and 642-645; (b) a variable heavy chain complementarity determining region 2 (VH CDR2) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 488 and 646650; (c) a variable heavy chain complementarity determining region 3 (VH CDR3) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 489 and 652-655; (d) a variable light chain complementarity determining region 1 (VL CDR1) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 656-663; (e) a variable light chain complementarity determining region 2 (VL CDR2) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 491 and 664-666; and (f) variable light chain complementarity determining region 3 (VL CDR3) comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 683-687. In some embodiments, the activatable anti-PD-1 antibody includes a combination of a variable heavy chain complementarity determining region 1 (VH CDR1, also referred to herein as CDRH1) sequence, a variable heavy chain complementarity determining region 2 (VH CDR2, also referred to herein as CDRH2) sequence, and a variable heavy chain complementarity determining region 3 (VH CDR3, also referred to herein as CDRH3) sequence, wherein the VH CDR1 sequence comprises GITFSNSG (SEQ ID NO: 525); the VH CDR2 sequence comprises IWYDGSKR (SEQ ID NO: 526); and the VH CDR3 sequence comprises TNDDY (SEQ ID NO: 527). In some embodiments, the activatable anti-PD-1 antibody includes a combination of a variable light chain complementarity determining region 1 (VL CDR1, also referred to herein as CDRL1) sequence, a variable light chain complementarity determining region 2 (VL CDR2, also referred to herein as CDRL2) sequence, and a variable light chain complementarity determining region 3 (VL CDR3, also referred to herein as CDRL3) sequence, wherein the VL CDR1 sequence comprises QSVSSY (SEQ ID NO: 528); the VL CDR2 sequence comprises DAS; and the VL CDR3 sequence comprises QQSSNWPRT (SEQ ID NO: 529). In some embodiments, the activatable anti-PD-1 antibody includes a combination of a variable heavy chain complementarity determining region 1 (VH CDR1, also referred to herein as CDRH1) sequence, a variable heavy chain complementarity determining region 2 (VH CDR2, also referred to herein as CDRH2) sequence, and a variable heavy chain complementarity determining region 3 (VH CDR3, also referred to herein as CDRH3) sequence, wherein the VH CDR1 sequence comprises GYTFTNYY (SEQ ID NO: 530); the VH CDR2 sequence comprises INPSNGGT (SEQ ID NO: 531); and the VH CDR3 sequence comprises RRDYRFDMGFDY (SEQ ID NO: 532). In some embodiments, the activatable anti-PD-1 antibody includes a combination of a variable light chain complementarity determining region 1 (VL CDR1, also referred to herein as CDRL1) sequence, a variable light chain complementarity determining region 2 (VL CDR2, also referred to herein as CDRL2) sequence, and a variable light chain complementarity determining region 3 (VL CDR3, also referred to herein as CDRL3) sequence, wherein the VL CDR1 sequence comprises KGVSTSGYSY (SEQ ID NO: 533); the VL CDR2 sequence comprises LAS; and the VL CDR3 sequence comprises QHSRDLPLT (SEQ ID NO: 534). In some embodiments, the activatable anti-PD-Ll antibody a heavy chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NOs: 673-694 and a light chain that comprises or is derived from an amino acid sequence selected from the group consisting of SEQ ID NO: 671 or SEQ ID NO: 672. In some aspects, the present disclosure includes an activatable anti-PD-Ll antibody disclosed in WO2016 / 149201, which is incorporated herein by reference in its entirety. In some embodiments, the activatable anti-PD-Ll antibody comprises a heavy chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs: 673-694 and comprises a light chain amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NO: 671 or SEQ ID NO: 672. In some embodiments, the activatable anti-PD-Ll antibody comprises a combination of a VH CDR1 sequence, a VH CDR2 sequence, a VH CDR3 sequence, a VL CDR1 sequence, a VL CDR2 sequence, and a VL CDR3 sequence, wherein at least one CDR sequence is selected from the group consisting of a VL CDR1 sequence comprising RASQSISSYLN (SEQ ID NO: 535); a VL CDR2 sequence comprising AASSLQS (SEQ ID NO: 536); a VL CDR3 sequence comprising DNGYPST (SEQ ID NO: 537); a VH CDR1 sequence comprising SYAMS (SEQ ID NO: 538); a VH CDR2 sequence comprising SSIWRNGIVTVYADS (SEQ ID NO: 539); and a VH CDR3 sequence comprising WSAAFDY (SEQ ID NO: 540). In some embodiments, the activatable anti-PD-Ll antibody comprises a masking moiety (MM) comprising an amino acid sequence selected from the group consisting of YCEVSELFVLPWCMG (SEQ ID NO: 584), SCLMHPHYAHDYCYV (SEQ ID NO:  585), LCEVLMLLQHPWCMG (SEQ ID NO:  586), IACRHFMEQLPFCHH   (SEQ ID NO: 587), FGPRCGEASTCVPYE (SEQ ID NO:  588), LYCDSWGAGCLTRP  (SEQ ID NO:  589), GIALCPSHFCQLPQT    (SEQ ID NO: 590), DGPRCFVSGECSPIG  (SEQ ID NO:  591), LCYKLDYDDRSYCHI (SEQ ID NO:  592), PCHPHPYDARPYCNV   (SEQ ID NO: 593), PCYWHPFFAYRYCNT (SEQ ID NO: 594), VCYYMDWLGRNWCSS (SEQ ID NO: 595), LCDLFKLREFPYCMG   (SEQ ID NO: 596), YLPCHFVPIGACNNK (SEQ ID NO:  597), FCHMGVVVPQCANY (SEQ ID NO:  598), ACHPHPYDARPYCNV   (SEQ ID NO: 599), PCHPAPYDARPYCNV (SEQ ID NO: 600), PCHPHAYDARPYCNV (SEQ ID NO: 601), PCHPHPADARPYCNV   (SEQ ID NO: 602), PCHPHPYAARPYCNV (SEQ ID NO:  603), PCHPHPYDAAPYCNV (SEQ ID NO:  604), PCHPHPYDARPACNV   (SEQ ID NO: 605), PCHPHPYDARPYCAV (SEQ ID NO: 606), PCHAHPYDARPYCNV (SEQ ID NO: 607), PCHPHPYDARAYCNV   (SEQ ID NO: 608). Provided herein are compositions comprising any one of the ACCs described herein. In some embodiments, the composition is a pharmaceutical composition. Also provided herein are kits comprising at least one dose of any one of the compositions described herein. Provided herein are are compositions comprising any one of the ACCs described herein and a PD-1 or PD-L1 antibody. Provided herein are are compositions comprising any one of the ACCs described herein and an activatable PD-1 or PD-L1 antibody. Also provided herein are kits comprising at least one dose of any one of the ACCs described herein and at least one dose of a PD-1 or PD-L1 antibody or a PD-1 or PD-L1 activatable antibody. Provided herein are methods of treating a subject in need thereof comprising administering to the subject a therapeutically effective amount of any one of the ACCs described herein with or without a PD1 / PD-L1 inhibitor selected from a PD-1 antibody, an activatable PD-1 antibody, aPD-Ll antibody, or an activatable PD-L1 antibody, or any one of the compositions described herein. In some embodiments, the subject has been identified or diagnosed as having a cancer. In some non-limiting embodiments, the cancer is Kaposi sarcoma, hairy cell leukemia, chronic myeloid leukemia (CML), follicular lymphoma, renal cell cancer (RCC), melanoma, neuroblastoma, basal cell carcinoma, bladder cancer, breast cancer, colorectal cancer, cutaneous T-cell lymphoma, nasopharyngeal adenocarcimoa, non-small cell lung cancer (NSCLC), colon cancer, renal cancer, ovarian cancer, pancreatic cancer. In some non-limiting embodiments, the cancer is a carcinoma. In some non-limiting embodiments, the cancer is a sarcoma. In some non-limiting embodiments, the cancer is a lymphoma. In some non-limiting embodiments, the lymphoma is Burkitt’s lymphoma. Provided herein are nucleic acids encoding a polypeptide that comprises the CPI and the CM1 of any one of the ACCs described herein. In some embodiments, the polypeptide further comprises any one of the DD1 described herein. In some embodiments, the polypeptide further comprises any one of the PM1 and the CM3 described herein. Also provided herein are nucleic acids encoding a polypeptide that comprises the CP2 and the CM2 of any one of the ACCs described herein. When the monomers are identical, then the present disclosure provides a single nucleic acid encoding the monomer that dimerizes to form ACC. In some embodiments, the polypeptide further comprises any one of the DD2 described herein. In some embodiments, the polypeptide further comprises any one of the PM2 and the CM4 described herein. In certain embodiments, the first monomer construct and the second monomer construct comprise identical CP, CM, and DD components. In some of these embodiments, the first and second monomer constructs are encoded by the same polypeptide (i.e., the same amino acid sequence). Often, when the first and second monomer constructs comprise the same amino acid sequence, they are encoded by the same nucleic acid (i.e., the same nucleic acid sequence). In some of these embodiments, the first and second monomer constructs are encoded by the same nucleic acid. Also provided herein are vectors comprising any one of the nucleic acids described herein. In some embodiments, the vector is an expression vector. Also provided herein are cells comprising any one of the nucleic acids described herein or any one of the vectors described herein. Provided herein are pairs of nucleic acids that together encode a polypeptide that comprises the CPI and the CM1 of the first monomer construct and a polypeptide that comprises the CP2 and the CM2 of the second monomer construct of any one of the ACCs described herein. Also provided herein are pairs of nucleic acids that together encode a polypeptide that comprises the PM1, the CM3, CPI and the CM1 of the first monomer construct and a polypeptide that comprises the PM2, the CM4, the CP2 and the CM2 of the second monomer construct of any one of the ACCs described herein. Also provided herein are pairs of vectors that together comprise any of one of the pair of nucleic acids described herein. In some embodiments, the pair of vectors is a pair of expression vectors. Also provided herein are cells comprising any one of the pairs of nucleic acids described herein or any one of the pairs of vectors described herein. In other embodiments, the present invention provides a vector comprising the pair of vectors. Provided herein are methods of producing an ACC comprising: culturing any one of the cells described herein in a liquid culture medium under conditions sufficient to produce the ACC; and recovering the ACC from the cell or the liquid culture medium. In some embodiments, the method further comprises: isolating the ACC recovered from the cell or the liquid culture medium. In some embodiments, the method further comprises: formulating isolated ACC into a pharmaceutical composition. In other embodiments, the method further comprises: formulating isolated ACC and a PD1 / PD-L1 inhibitor selected from aPD-1 antibody, an activatable PD-1 antibody, aPD-Ll antibody, or an activatable PD-L1 antibody into a pharmaceutical composition. Provided herein are ACCs produced by any one of the methods described herein. Also provided herein are compositions comprising any one the ACCs described herein with or without a PD1 / PD-L1 inhibitor selected from a PD-1 antibody, an activatable PD-1 antibody, a PD-L1 antibody, or an activatable PD-L1 antibody. Also provided herein are compositions of any one of the compositions described herein, wherein the composition is a pharmaceutical composition. Also provided herein are kits comprising at least one dose of any one of the compositions described herein. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. Other features and advantages of the invention will be apparent from the following detailed description and figures, and from the claims. The term “a” and “an” refers to one or more (i.e., at least one) of the grammatical object of the article. By way of example, “a cell” encompasses one or more cells. As used herein, the terms “about” and “approximately,” when used to modify an amount specified in a numeric value or range, indicate that the numeric value as well as reasonable deviations from the value known to the skilled person in the art. For example, ± 20%, ± 10%, or ± 5%, are within the intended meaning of the recited value where appropriate. Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 0.01 to 2.0” should be interpreted to include not only the explicitly recited values of about 0.01 to about 2.0, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 0.5, 0.7, and 1.5, and sub-ranges such as from 0.5 to 1.7, 0.7 to 1.5, and from 1.0 to 1.5, etc. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. Additionally, it is noted that all percentages are in weight, unless specified otherwise. In understanding the scope of the present disclosure, the terms “including” or “comprising” and their derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and / or steps. The foregoing also applies to words having similar meanings such as the terms “including”, “having” and their derivatives. The term “consisting” and its derivatives, as used herein, are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, but exclude the presence of other unstated features, elements, components, groups, integers and / or steps. The term “consisting essentially of,” as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and / or steps as well as those that do not materially affect the basic and novel characteristic(s) of features, elements, components, groups, integers, and / or steps. It is understood that reference to any one of these transition terms (i.e. “comprising,” “consisting,” or “consisting essentially”) provides direct support for replacement to any of the other transition term not specifically used. For example, amending a term from “comprising” to “consisting essentially of’ or “consisting of’ would find direct support due to this definition for any elements disclosed throughout this disclosure. Based on this definition, any element disclosed herein or incorporated by reference may be included in or excluded from the claimed invention. As used herein, a plurality of compounds, elements, or steps may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. Furthermore, certain molecules, constructs, compositions, elements, moieties, excipients, disorders, conditions, properties, steps, or the like may be discussed in the context of one specific embodiment or aspect or in a separate paragraph or section of this disclosure. It is understood that this is merely for convenience and brevity, and any such disclosure is equally applicable to and intended to be combined with any other embodiments or aspects found anywhere in the present disclosure and claims, which all form the application and claimed invention at the filing date. For example, a list of constructs, molecules, method steps, kits, or compositions described with respect to a construct, composition, or method is intended to and does find direct support for embodiments related to constructs, compositions, formulations, and methods described in any other part of this disclosure, even if those method steps, active agents, kits, or compositions are not re-listed in the context or section of that embodiment or aspect. Unless otherwise specified, a “nucleic acid sequence encoding a protein” includes all nucleotide sequences that are degenerate versions of each other and thus encode the same amino acid sequence. The term “N-terminally positioned” when referring to a position of a first domain or sequence relative to a second domain or sequence in a polypeptide primary amino acid sequence means that the first domain or sequence is located closer to the N-terminus of the polypeptide primary amino acid sequence than the second domain or sequence. In some embodiments, there may be additional sequences and / or domains between the first domain or sequence and the second domain or sequence. The term “C-terminally positioned” when referring to a position of a first domain or sequence relative to a second domain or sequence in a polypeptide primary amino acid sequence means that the first domain or sequence is located closer to the C-terminus of the polypeptide primary amino acid sequence than the second domain or sequence. In some embodiments, there may be additional sequences and / or domains between the first domain or sequence and the second domain or sequence. The term “exogenous” refers to any material introduced from or originating from outside a cell, a tissue, or an organism that is not produced by or does not originate from the same cell, tissue, or organism in which it is being introduced. The term “transduced,” “transfected,” or “transformed” refers to a process by which an exogenous nucleic acid is introduced or transferred into a cell. A “transduced,” “transfected,” or “transformed” cell (e.g., mammalian cell) is one that has been transduced, transfected, or transformed with exogenous nucleic acid (e.g., a vector) that includes an exogenous nucleic acid encoding any of the activatable cytokine constructs described herein. The term “nucleic acid” refers to a deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), or a combination thereof, in either a single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses complementary sequences as well as the sequence explicitly indicated. In some embodiments of any of the nucleic acids described herein, the nucleic acid is DNA. In some embodiments of any of the nucleic acids described herein, the nucleic acid is RNA. Modifications can be introduced into a nucleotide sequence by standard techniques known in the art, such as site-directed mutagenesis and polymerase chain reaction (PCR)-mediated mutagenesis. Conservative amino acid substitutions are ones in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include: amino acids with acidic side chains (e.g., aspartate and glutamate), amino acids with basic side chains (e.g., lysine, arginine, and histidine), nonpolar amino acids (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, and tryptophan), uncharged polar amino acids (e.g., glycine, asparagine, glutamine, cysteine, serine, threonine and tyrosine), hydrophilic amino acids (e.g., arginine, asparagine, aspartate, glutamine, glutamate, histidine, lysine, serine, and threonine), hydrophobic amino acids (e.g., alanine, cysteine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan, tyrosine, and valine). Other families of amino acids include: aliphatic-hydroxy amino acids (e.g., serine and threonine), amide family (e.g., asparagine and glutamine), alphatic family (e.g., alanine, valine, leucine and isoleucine), and aromatic family (e.g., phenylalanine, tryptophan, and tyrosine). As used herein the phrase “specifically binds,” or “immunoreacts with” means that the activatable antigen-binding protein complex reacts with one or more antigenic determinants of the desired target antigen and does not react with other polypeptides, or binds at much lower affinity, e.g., about or greater than 10'6 M. The term “treatment” refers to ameliorating at least one symptom of a disorder. In some embodiments, the disorder being treated is a cancer and to ameliorate at least one symptom of a cancer. BRIEF DESCRIPTION OF DRAWINGS Figs. 1-4 are schematics of illustrative activatable cytokine constructs. Figs. 5A-5B depict the cleavage reaction of a cytokine construct without a peptide mask, IFNa-2b-hIgG4 Fc (with either cleavable moiety 1204dL or cleavable moiety 1490), and a protease (either uPA or MT-SP1), which generates monomeric mature IFNa-2b. Figs. 6A-6C show activation of a cytokine construct (ProC440) by proteases uPa and MMP14. The ProC440 in Fig. 6B has a sequence of SEQ ID NO: 286. Figs. 7A-7B show the activity of a cytokine construct (ProC440) tested in vitro using IFN-responsive HEK293 cells (Fig. 7A) and Daudi cells (Fig. 7B). Fig. 8 shows the sequence of a masked cytokine construct, ProC732 with an optional signal sequence in italics, the masking peptide sequence in double-underline, the sequences of cleavable moieties in bold, and the sequence of the mature IFNalpha-2b underlined. Fig. 9 shows shows the sequence of a masked cytokine construct with no cleavable moiety sequence between the cytokine and the dimerization domain, ProC733, with an optional signal sequence in italics, the masking peptide sequence in doubleunderline, the cleavable moiety sequence in bold, and the sequence of the mature IFNalpha-2b underlined. Fig. 10A shows schematics of ProC440, ProC732 and ProC733. Fig. 10B shows the activity of cytokine constructs (ProC440, ProC732 and ProC733) tested using IFN-responsive HEK293 cells. Fig. 11A shows a schematic of the structure of cytokine construct ProC286, and the activity of ProC286 compared to the activity of Sylatron® (PEGylated interferon alpha-2b) in the Daudi apoptosis assay. ProC286 and Sylatron® showed similar levels of activity indicating that ProC286 could be used as surrogate Sylatron® control to evaluate the tolerability of IFNa-2b in the hamster study. Fig. 11B depicts a schematic of the structure of ProC291 and the activity of ProC291 compared to the activity of Sylatron® in the Daudi apotosis assay. ProC291 showed significantly reduced activity compared to Sylatron® and ProC286 Fig. 12 shows the specific activity of IFNa-con (recombinant interferon alpha, a non-naturally occurring type-I interferon); the active cytokine cleavage product of ProC440 (ProC440+uPA); Sylatron® (“PEG-IFNa2b”); and ProC440, and and anticipated toxic dosages in a dose-escalation study in vivo, e.g., at escalating doses of 0.08, 0.4, 2, 10, and 15 mg / kg (“mpk”). Fig. 13A-13D show body weight loss profiles of animals in response to different doses of cytokine constructs ProC286, ProC440, and ProC732 or control (human IgG4) in tolerability tests at different dosages in Syrian Gold Hamsters. Fig. 13 A shows data for 2 mg / kg (“2 mpk”) dosages; Fig. 13B shows data for 10 mg / kg dosages; and Fig. 13C shows data for 15 mg / kg dosages of each construct tested; Fig. 13D shows FNFa2b mediated toxicity in animals dosed with unmasked IFNa2b / Fc corresponding to increased ALP and increased therapeutic index of IFNa2b single and dual mask. Fig. 14 shows clinical chemistry analysis outcomes (Alkaline phosphatase, Alanine transaminase, and Aspartate transaminase) of Syrian Gold Hamsters in response to different doses (2 mpk, 10 mpk, and 15 mpk) of cytokine constructs ProC286, ProC440, and ProC732 or control (human IgG4) in tolerability tests. Fig. 15 shows hematology analysis outcomes (Reticulocyte, Neutrophil, and White Blood Cells (WBC) counts) in Syrian Gold Hamsters in response to different doses (2 mpk, 10 mpk, and 15 mpk) of cytokine constructs ProC286, ProC440, and ProC732 or control (human IgG4) in tolerability tests. Fig. 16 depicts the effect of length of a Linking Region (LR) on the activities of IFNalpha-2b-Fc fusion proteins without a peptide mask, as determined from a Daudi apoptosis assay. Fig. 17 schematically illustrates a cytokine construct without a peptide mask, including a depiction of the linking region (LR). Fig. 18A shows anti-tumor activity of masked activatable IFNa A / D (ProC1023) at 10, 50, and 200 pg. Fig. 18B shows in vivo activation of masked IFNa A / D relative (ProC1023) to an uncleavable masked IFNa A / D (ProC1549). Fig. 18C shows the antitumour activity of the combination of masked IFNa A / D (ProC1023) with PD-L1 monoclonal antibody (CX-171) compared to masked IFNa A / D (ProC1023) alone and compared to PD-L1 monoclonal antibody (CX-171) alone. Figs. 19A-19B show immune memory in response to MC38 tumor cell rechallenge in mice previously treated with activatable IFNa A / D (200 micrograms ProC1023) (bottom, Fig. 19B) compared to MC38 tumor cell challenge in naive control mice (top, Fig. 19A). Fig. 20 shows the combinatorial effect of Pro-IFN-a2b and PD-L1 monoclonal antibody on IFN-gamma release in patients’ tissues compared to masked IFN-a2b, unmasked IFN-a2b, Peg-IFN-a2b alone, PD-L1 monoclonal antibody alone, and control in Patient’s PBMC (left) and Patient’s dissociated tumor cells (right). Fig. 21 shows activation-dependent induction of type I interferon signature by unmasked IFN-a2b. Fig. 22 shows pharmacokinetics of the dual masked INF-a2b (ProC732) and control molecules in hamsters. Fig. 23 shows anti-tumor activity of masked activatable IFNa A / D at 20 pg and 200 pg compared to control. Fig. 24A shows the activity of ProC1023 compared to ProC859 in an IFNa reporter assay in B16 mouse melanoma cells. Figs. 24B and 24C show the activity of ProC1023 compared to ProC1549 in an IFNa reporter assay in B16 mouse melanoma cells. Fig. 25 shows the activity of ProC1239 and ProC732 tested in vitro using IFN-responsive HEK293 cells. Fig. 26 shows the activity of ProC732, ProC1550 and ProC1552 tested in vitro using IFN-responsive HEK293 cells in an uncleaved state and after protease activation with either uPa or MTSP1. Fig. 27 shows activity of recombinant IFNa2b, monomeric IFNa2b / Fc, activated homodimeric IFNa2b / Fc, and homodimeric IFNa2b / Fc using IFN-responsive HEK293 cells in an uncleaved state and after protease activation. Fig. 28 shows anti-tumor activity of single masked IFNa2b / Fc (top) and peginterferon (bottom) at increasing doses. Fig. 29 depicts the structure of ACC ProC859 universal interferon (top), the antiproliferative effects of ACC ProC859 in a B16 mouse melanoma cell assay and the activity of ACC ProC859 in the IFN-responsive HEK293 assay. Fig. 30 shows CD14, CD3, PD-L1, and IFNAR1 positive cells in the PBMC population and myeloid cells from healthy donors compared to patient PBMC and disassociated tumor. Fig. 31 shows the combinatorial effect of activated IFN-a2b and PD-L1 monoclonal antibody on IFN-gamma release in patients’ tissues compared to untreated, dual masked IFN-a2b, sylatron alone, and PD-L1 monoclonal antibody or dual masked IFN-a2b alone. Fig. 32 shows the activity of activated and non-activated single masked IFNa2b and activated and non-activated dual mask IFNa2b tested in vitro using IFN-responsive HEK293 cells in an uncleaved state and after protease activation. Fig. 33A shows anti-tumor activity of dual masked activatable IFNa A / D compared to dual masked non-activatable IFNa A / D at 10 pg, 50 pg, and 200 pg. Fig. 33B shows shows anti-tumor activity of dual masked IFNa A / D in combination with PD-L1 monoclonal antibody compared to dual masked IFNa A / D or PD-L1 monoclonal antibody alone. Fig. 34A shows anti-tumor activity of Pro IFNa A / D (ProC1023) at 10, 50, and 200 pg compared to PBS control. Fig. 34B shows anti-tumor activity of Pro IFNa A / D (ProC1023) compared to IFNa A / D NSUB (ProC1549) at 200 pg. Fig. 35A shows anti-tumor activity of Pro IFNa A / D (ProC1023) at 10 pg, 50 pg, and 200 pg compared to 200 pg PD-L1 monoclonal antibody (CX-171). Fig. 35B shows anti-tumor activity of IFNa A / D NSUB (ProC1549) at 50 and 200 pg compared to PBS control. Fig. 36 schematically illustrates a cytokine construct including a depiction of the linking region (LR) and mask linking region (MLR). Fig. 37 shows changes in tumor volume over time and survival for mice implanted with CT26 and B16 synegeneic tumor models. Figs. 38A-38D show binding of single masked Pb-IFN-a2b molecules to human IFNAR2. The ligands were captured on a chip coated with immobilized anti-human Fc (Figs. 38A-38B) or anti-histidine antibodies (Figs. 38C-38D). Concentrations of IFN-a2b (ProC1640) ranging from 25 nM to 1.5625 pM were flowed over the ligand-captured chip to generate multi-cycle kinetic sensorgrams (Figs. 38A and 38C). Masked Pb-IFN-a2b molecules (ProC440 - Fig. 38D, ProC1976 - Fig. 38B) at concentrations ranging from 250 nM to 15.625 pM were flowed over the ligand-captured chip to generate multicycle kinetic sensorgrams. Fig. 39A shows MMP restores NSUB (ProC649) activity. Fig. 39B shows conditional activation of ProC732 and ProC1299 by uPA. Fig. 39C shows IFNa2b (SEQ ID NO: 1) compared to IFNaAD and that ProC1301 is resistant to activation compared to ProC732. Figs. 40A-40D show binding of activated Pb-IFN-a2b to interferon alpha receptors in vitro. Human IFNARl, human IFNAR2, cyno IFNAR1 or cyno IFNAR2 proteins were captured on a chip coated with immobilized anti-human Fc. Concentrations of activated IFN-a2b (ProC1640) ranging from 25 nM to 1.5625 pM were flowed over the ligand-captured chip to generate multi-cycle kinetic sensorgrams. Figs. 41A-41C show an assay of activation of ProC732 by tumor tissues (Fig. 41 A) and results. Fluorescently labeled ProC732 was incubated on tumor tissue sections at 37°C. Recovered solution was then analyzed through capillary electrophoresis enabling quantification of active molecules (Fig. 4IC) and using HEK-blue IFNA reporter model (Fig. 4IB). Enzymatically inactive samples were used as control tissues. Figs. 42A-42C show changes in bioactivity of ProC732 (Fig. 42A) and recombinant IFN-a2b (Fig. 42B) molecules after incubation with tumor tissues analyzed by HEK-blue IFNA reporter model. Fold change of bioactivity of 10 ng / mL ProC732or 1 ng / mL of recombinant IFN-a2b was calculated relative to Oh values. Bioactivity of ProC732 and IFN-a2b proteins incubated in the absence of tumor tissues for 24h (Fig. 42C). Each line connects an individual sample (concentration range 100-0.01 ng / mL) analyzed before and after 24h incubation. Figs. 43, 44A, and 44B show pharmacokinetics of the masked INF-a2b and control molecules in non-human primates. Cynomolgus monkey (N=2 per group) were treated with a single dose subcutaneous administration of ProC732 at 0.03, 0.3, 3 or 15 mg / kg. Fig. 43 shows results where plasma samples were collected at indicated time points and analyzed for total ProC732 concentration. Fig. 44A shows concentrations of IP-10 in serum were measured by MSD V-plex assay. Fig. 44B shows concentrations of circulating Pb-IFN-a2b and IP-10 plotted against each other at day 1 and day 7 after administration. Figs. 45 and 46 show gene expression profile changes induced by ProC732 nonhuman primates based on concentration (Fig. 45). Cynomolgus monkey (N=2 per group) were treated with a single dose subcutaneous administration of ProC732 at 0.03, 0.3, 3 or 15 mg / kg. PBMC from treated animals were harvested and analyzed by bulk RNAseq. Genes were called differentially expressed if number of reads changes were >3 (Fig. 46). Fig. 47 shows that ProC1023 preferentially activates immune cells in tumor tissues. Six days after the treatment tumors and tissues were harvested and analyzed by flow cytometry. Gated on viable CD45+CD3+ cells. Fig. 48 shows that ProC732 is well tolerated after multidose administration. Male Syrian golden hamsters (N=5) were treated i.p. with three weekly administrations of 15, 30 or 60 mg / kg Pb-IFN-a2b (ProC732), or 3.75, 7.5 or 15 mg / kg of unmasked Fc-IFN-a2b (ProC286) fusion proteins. Survival results include animals found dead or experienced body weight loss >15%. Fig. 49 shows that masking of ProC732 attenuates cytokine / chemokine release in non-human primates. Fig. 50 shows that dual masked Pb-IFN-a2b (ProC732) suppresses tumor growth in immune competent rodents in vivo. Male Syrian golden hamsters (N=16) were implanted with 10 mln RPMI-1846 hamster melanoma cells subcutaneously and treated intraperitoneally with twice weekly administrations of 5, 10 or 20 mg / kg Pb-IFN-a2b. Fig. 51 shows anti-tumor activity of dual masked IFNa2b / Fc and peginterferon at increasing doses. Beige / SCID mice (n=8 per group) were implanted subcutaneously with 10 mln human lymphoma (Daudi) cells and treated when the average tumor volume reached -200 mm3. Indicated doses of Pb-IFN-a2b (ProC732), unmasked Fc-IFN-a2b (ProC286) and Peg-IFN-a2b were administered i.v. once weekly for 3 weeks. Fig. 52 shows pharmacokinetics of the dual masked Pb-INF-a2b (ProC732) in Biege / SCID mice. Beige / SCID mice (n=15 per group) were treated with single administration of indicated doses of Pb-IFN-a2b (ProC732). Plasma for PK studies was collected at 1, 2, 3, 6, 24, 48, 72, 120 hours, 7 and 14 days after the administration. Samples were analyzed by MSD assay. Fig. 53 shows that Pb-IFN-a2b is stable in non-human primates. Cynomolgus monkey (N=4 per group, 2 males + 2 females) were treated intravenously with three weekly administrations of 7.5, 15, 30 or 60 mg / kg of Pb-IFN-a2b (ProC732). In a satellite experiment, a single group of monkeys (N=2, 1 per sex) was treated with 30 mg / kg Pb-IFN-a2b weekly for three weeks. Plasma concentration of Pb-IFN-a2b (ProC732) and its activation products was measured by LC-MS. DETAILED DESCRIPTION Provided herein are activatable cytokine constructs (ACCs) that exhibit a reduced level of at least one activity of the corresponding cytokine, but which, after exposure to an activation condition, yield a cytokine product having substantially restored activity. Activatable cytokine constructs of the present invention may be designed to selectively activate upon exposure to diseased tissue, and not in normal tissue. Further provided herein is a combination therapy or use of an ACC described herein in combination with a PD1 / PD-L1 inhibitor selected from a PD-1 antibody, an activatable PD-1 antibody, a PD-L1 antibody, or an activatable PD-L1 antibody. As such, these compounds have the potential for conferring the benefit of a cytokine-based therapy, with potentially less of the toxicity associated with certain cytokine-based therapies. Further, this combination therapy may confer the benefits of a cytokine-based therapy and an anti-PDl and / or anti-PD-L1 therapy, with potentially less of the toxicity associated with respective monotherapies and respective combination therapies that do not include use of the ACCs disclosed herein. Also provided herein are related intermediates, compositions, kits, nucleic acids, and recombinant cells, as well as related methods, including methods of using and methods of producing any of the activatable cytokine constructs described herein. The inventors have surprisingly found that ACCs having the specific elements and structural orientations described herein appear potentially effective in improving the safety and therapeutic index of cytokines in therapy, particulary for treating cancers. While cytokines are regulators of innate and adaptive immune system and have broad anti-tumor activity in pre-clinical models, their clinical success has been limited by systemic toxicity and poor systemic exposure to target tissues. The inventors have surprisingly found that ACCs having the specific elements and structural orientations described herein appear to reduce the systemic toxicity associated with cytokine therapeutics and improve targeting and exposure to target issues. As such, the present disclosure provides a method of reducing target-mediated drug disposition (TMDD) of cytokine therapeutics by administering ACCs having the specific elements and structural orientations described herein to a subject. As such, the invention solves the problem of sequestration of a significant fraction of the administered cytokine dose by normal tissues, which is a problem that limits the fraction of the dose available in the systemic circulation to reach the target tissues, e.g., cancerous tissue, in conventional cytokine therapeutics. The present cytokine constructs localizes target binding to tumor tissues, thereby maintaining potency, reducing side effects, enabling new target opportunities, improving the therapeutic window for validated targets, creating a therapeutic window for undruggable targets, and providing multiple binding modalities. The present disclosure further provides methods of administering ACCs in combination with a PD1 / PD-L1 inhibitor selected from a PD-1 antibody, an activatable PD-1 antibody, a PD-L1 antibody, or an activatable PD-L1 antibody. In some embodiments, the combination of an ACC and PD1 / PDL1 inhibitor may augment or potentiate therapeutic efficacy and / or therapeutic index relative to a conventional cytokine therapy. In some embodiments, the combination of an ACC and PD1 / PDL1 inhibitor may augment or potentiate therapeutic efficacy and / or therapeutic index relative to a conventional PD1 / PDL1 inhibitor therapy. In some embodiments, the combination of an ACC and PD1 / PDL1 inhibitor may augment or potentiate therapeutic efficacy and / or therapeutic index relative to a conventional cytokine and PD1 / PDL1 inhibitor combination therapy. In still other embodiments, the combination of an ACC and a PD1 / PDL1 inhibitor may augment or potentiate therapeutic efficacy and / or therapeutic index relative to administering an ACC of the present disclsosure alone. The present disclosure enables safe and effective systemic delivery, thereby avoiding the dose-dependent toxicities of conventional systemic cytokine therapies, and also avoids a requirement for intra-tumoral injection. The present disclosure provides a means for imparting localized anti-viral activity, immunomodulatory activity, antiproliferative activity and pro-apoptotic activity. The inventors surprisingly found that dimerization of the first and second monomer constructs achieves high reduction of cytokine activity, and surprisingly discovered that the cytokine activity can be substantially reduced with very high masking efficiency by the addition of a peptide mask at the other terminus of the activatable construct. See, e.g., Figs. 10A-10B. Applicant’s U.S. Provisional App. No. 63 / 008,542, filed April 10, 2020, and U.S. Provisional App. No. 63 / 161,889 filed March 16, 2021, which describe certain activatable cytokine constructs without an affinity peptide mask, are incorporated herein by reference in their entireties. Activatable Cytokine Constructs and Activatable Antibodies Activatable cytokine constructs (ACCs) of the present invention are dimer complexes comprising a first monomer construct and a second monomer construct. Dimerization of the monomeric components is facilitated by a pair of dimerization domains. In one aspect, each monomer construct includes a cytokine protein (CP), one or more cleavable moieties (CM), a dimerization domain (DD), and a peptide mask (PM). The present inventors unexpectedly found that ACC structures comprising both a dimerization domain and a peptide mask have improved masking efficiency to minimize or eliminate off-target effects and undesired activity and / or toxic side effects of cytokines. In a specific embodiment, the present invention provides an activatable cytokine construct (ACC) that includes a first monomer construct and a second monomer construct, wherein: (a) the first monomer construct comprises a first peptide mask (PM1), a first mature cytokine protein (CPI), a first and third cleavable moieties (CM1 and CM2), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CPI and the DD1 and the CM2 is positioned between the PM1 and the CPI; and (b) the second monomer construct comprises a second mature cytokine protein (CP2), a second cleavable moiety (CM3), and a second dimerization domain (DD2), wherein the CM3 is positioned between the CP2 and the DD2; wherein the DD1 and the DD2 bind each other thereby forming a dimer of the first monomer construct and the second monomer construct; and wherein the ACC is characterized by having a reduced level of at least one CPI and / or CP2 activity as compared to a control level of the at least one CPI and / or CP2 activity. In some embodiments, the second monomer construct further comprises a second peptide mask (PM2) and a fourth cleavable moiety (CM4) positioned between the PM2 and the CP2. In some embodiments, the first monomer construct and the second monomer construct are identical and bind one another to form a homodimer. In other embodiments, at least one of the CP, CM, PM, or DD components in each of the first and second monomer constructs is not identical, and the first and second monomer constructs bind one another to form a heterodimer. In another specific embodiment, the ACC is used in a combination therapy with an isolated antibody or antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 orPD-Ll. In further specific embodiment, the ACC is used in a combination therapy with an activatable anti-PD-1 or an anti-PD-Ll antibody that, in an activated state, specifically binds to mammalian PD-1 or PD-L1, wherein said activatable antibody comprises: an antibody or an antigen binding fragment thereof (AB) that specifically binds to mammalian PD-1 or anti-PD-Ll; a masking moiety (MM) that inhibits the binding of the AB to mammalian PD-1 or PD-L1 when the activatable antibody is in an uncleaved state; a cleavable moiety (CM) coupled to the AB, wherein the CM is a polypeptide that functions as a substrate for a protease; and optionally a first linking peptide (LP1) and / or a second linking peptide (LP2). The term “activatable” when used in reference to a cytokine construct and an activatable anti-PD-1 or anti-PD-Ll antibody, refers to a cytokine construct or anti-PD-1 or anti-PD-Ll antibody that exhibits a first level of one or more activities, whereupon exposure to a condition that causes cleavage of one or more cleavable moieties results in the generation of a cytokine construct or an anti-PD-1 or anti-PD-Ll antibody that exhibits a second level of the one or more activities, where the second level of activity is greater than the first level of activity. Non-limiting examples of an activities include any of the exemplary activities of a cytokine, anti-PD-1, or anti-PD-Ll described herein or known in the art, respectively. The term “mature cytokine protein” refers herein to a cytokine protein that lacks a signal sequence. A signal sequence is also referred to herein as a “signal peptide.” A cytokine protein (CP) may be a mature cytokine protein or a cytokine protein with a signal peptide. Thus, the ACCs of the present disclosure may include a mature cytokine protein sequence in some aspects. In some aspects, the ACCs of the present disclosure may include a mature cytokine protein sequence and, additionally, a signal sequence. In some aspects, the ACCs of the present disclosure may include sequences disclosed herein, including or lacking the signal sequences recited herein. In some embodiments, a signal sequence is selected from the group consisting of SEQ ID NO: 468, SEQ ID NO: 469, and SEQ ID NO: 470. The terms “cleavable moiety” and “CM” are used interchangeably herein to refer to a peptide, the amino acid sequence of which comprises a substrate for a sequencespecific protease. Cleavable moieties that are suitable for use as a CM include any of the protease substrates that are known the art. Exemplary cleavable moieties are described in more detail below. The terms “peptide mask” and “PM” are used interchangeably herein to refer to an amino acid sequence of less than 50 amino acids that reduces or inhibits one or more activities of a cytokine protein. The PM may bind to the cytokine and limit the interaction of the cytokine with its receptor. In some embodiments, the PM is no more than 40 amino acids in length. In preferred embodiments, the PM is no more than 20 amino acids in length. In some embodiments, the PM is no more than 19, 18, 17, 16, or 15 amino acids in length. In some aspects, the PM has at least 13 amino acids (including any number from 13 to 49). In some aspects, the PM has at least 14 amino acids (including any number from 14 to 49). In some aspects, the PM has at least 15 amino acids (including any number from 15 to 49). In certain aspects, the number of amino acids in the PM may be counted as those amino acids that bind to the cytokine protein. For example, the PM excludes large polypeptides. For example, the PM is not a latency associated peptide. For example, the PM is not a cytokine. For example, the PM is not a receptor for a cytokine. For example, the PM is not a fragment of a receptor for a cytokine. In some aspects, the PM does not have an amino acid sequence that is at least 85% identical to a receptor for a cytokine. For example, the PM is not an albumin. For example, the PM excludes proteins or polypeptides having more than 50 amino acids. In some aspects, the PM excludes proteins or polypeptides having more than 25 amino acids. In some aspects, the PM excludes proteins or polypeptides having more than 20 amino acids. In some aspects, the PM excludes proteins or polypeptides having more than 15 amino acids. In some aspects, the PM does not include amino acids forming flexible N-terminal or C-terminal tail regions. A “masking moiety” or “MM” in an activatable macromolecule (that is not yet activated) “masks” or reduces or otherwise inhibits the binding of the activatable macromolecule to its target and / or epitope. In some embodiments, the coupling or modifying of anti-PD-1 or anti-PD-Ll antibody with a MM can inhibit the ability of the anti-PD-1 or anti-PD-Ll antibody to specifically bind its target and or epitope by means of inhibition known in the art (e.g., without limitation, structural change and competition for antigen-binding domain). In some embodiments, the coupling or modifying of anti-PD-1 or anti-PD-Ll antibody with a MM can effect a structural change that reduces or inhibits the ability of the protein to specifically bind its target and or epitope. In some embodiments, the coupling or modifying of anti-PD-1 or anti-PD-Ll antibody with a MM sterically blocks, reduces or inhibits the ability of the anti-PD-1 or anti-PD-Ll antibody to specifically bind its target and or epitope. In some embodiments, the MM may be a polypeptide of about 2 to 50 amino acids in length. For example, the MM may be a polypeptide of from 2 to 40, from 2 to 30, from 2 to 20, from 2 to 10, from 5 to 15, from 10 to 20, from 15 to 25, from 20 to 30, from 25 to 35, from 30 to 40, from 35 to 45, from 40 to 50 amino acids in length. For example, the MM may be a polypeptide with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 amino acids in length. In some examples, the MM may be a polypeptide of more than 50 amino acids in length, e.g., 100, 200, 300, 400, 500, 600, 700, 800, or more amino acids. The terms “dimerization domain” and “DD” are used interchangeably herein to refer to one member of a pair of dimerization domains, wherein each member of the pair is capable of binding to the other via one or more covalent or non-covalent interactions. The first DD and the second DD may be the same or different. Exemplary DDs suitable for use as DD1 and or DD2 are described in more detail herein below. As used herein, the terms “linker,” “linking peptide,” “LP” refers to a peptide, the amino acid sequence of which is not a substrate for a protease. Exemplary linkers and LPs are described in more detail below. As used herein, the term “linking region” or “LR” refers to the stretch of amino acid residues between the C-terminus of the cytokine and the amino acid residue that is N-terminally adjacent to the proximal point of interaction between the dimerization domains (i.e., the linking region does not include the C-terminal amino acid of the cytokine or the N-terminal amino acid of the DD that forms the proximal point of interaction to the DD of the corresponding second monomer). For example, when the DDs are a pair of Fc domains, the linking region is the stretch of amino acid residues between the C-terminus of the cytokine and the first N-terminal cysteine residue of the Fc that participates in the disulfide linkage with the second Fc domain (e.g., Cysteine 226 of an IgGl or IgG4 Fc domain, according to EU numbering). When the dimerization domain is not a polypeptide, then the linking region is the stretch of amino acid residues following the C-terminus of the cytokine until the last amino acid. For example, when the DDs are a biotin-streptavidin pair, the linking region of the biotin-containing monomer is the stretch of amino acid residues between the C-terminus of the cytokine and the biotin molecule, and the linking region of the streptavidin-containing monomer is the stretch of amino acid residues between the C-terminus of the cytokine and the streptavidin molecule. As used herein, the term “mask linking region” or “MLR” refers to the stretch of amino acid residues between a PM and a CP. As shown in Fig. 36, the MLR spans from the N-terminus of a CP to the C-terminus of a PM. Thus, the MLR may include a PM, a PM and a linker, or a PM and two linkers. In some aspects, the MLR spans 15 to 22 amino acids. In some aspects, the MLR spans 16 to 21 amino acids. In some aspects, the MLR spans 17 to 20 amino acids. In some aspects, the MLR spans 18 to 20 amino acids. In some aspects, the MLR spans 15, 16, 17, 18, 18, 20, 21, or 22 amino acids. As used herein, the term “masking efficiency” refers to the activity (e.g., EC50) of the uncleaved ACC, activatable anti-PD-1, or activatable anti-PD-Ll antibody divided by the activity of a control cytokine, anti-PD-1, or anti-PD-Ll antibody wherein the control cytokine, anti-PD-1, or anti-PD-Ll antibody may be either cleavage product of the ACC, activatable anti-PD-1, or activatable anti-PD-Ll or the cytokine, anti-PD-1, or anti-PD-Ll used as the CP of the ACC, activatable anti-PD-1, or activatable anti-PD-Ll antibody. An ACC having a reduced level of at least one CPI and / or CP2 activity has a masking efficiency that is greater than 10. In some embodiments, the ACCs, activatable anti-PD-1, or activatable anti-PD-Ll antibodies described herein have a masking efficiency that is greater than 10, greater than 100, greater than 1000, or greater than 5000. As used herein, the term “spacer” refers herein to an amino acid residue or a peptide incorporated at a free terminus of the mature ACC, for example between the signal peptide and the N-terminus of the mature ACC. In some aspects, a spacer (or “header”) may contain glutamine (Q) residues. In some aspects, residues in the spacer minimize aminopeptidase and / or exopeptidase action to prevent cleavage of N-terminal amino acids. Illustrative and non-limiting spacer amino acid sequences may comprise or consist of any of the following exemplary amino acid sequences: QGQSGS (SEQ ID NO: 471); GQSGS (SEQ ID NO: 472); QSGS (SEQ ID NO: 473); SGS; GS; S; QGQSGQG (SEQ ID NO: 474); GQSGQG (SEQ ID NO: 475); QSGQG (SEQ ID NO: 476); SGQG (SEQ ID NO: 477); GQG; QG; G; QGQSGQ (SEQ ID NO: 478); GQSGQ (SEQ ID NO: 479); QSGQ (SEQ ID NO: 480); QGQSG (SEQ ID NO: 481); QGQS (SEQ ID NO: 482); SGQ; GQ; and Q. In some embodiments, spacer sequences may be omitted. As used herein, a polypeptide, such as a cytokine or an Fc domain, may be a wildtype polypeptide (e.g., a naturally-existing polypeptide) or a variant of the wild-type polypeptide. A variant may be a polypeptide modified by substitution, insertion, deletion and / or addition of one or more amino acids of the wild-type polypeptide, provided that the variant retains the basic function or activity of the wild-type polypeptide. In some examples, a variant may have altered (e.g., increased or decreased) function or activity comparing with the wild-type polypeptide. In some aspects, the variant may be a functional fragment of the wild-type polypeptide. The term “functional fragment” means that the sequence of the polypeptide (e.g., cytokine) may include fewer amino acids than the full-length polypeptide sequence, but sufficient polypeptide chain length to confer activity (e.g., cytokine activity). The first and second monomer constructs may further comprise additional elements, such as, for example, one or more linkers, and the like. The additional elements are described below in more detail. The organization of the CP, CM, PM, and DD components in each of the first and second monomer constructs may be arranged in the same order in each monomer construct. The CPI, CM1, PM1, and DD1 components may be the same or different as compared to the corresponding CP2, CM2, PM2, and DD2, in terms of, for example, molecular weight, size, amino acid sequence of the CP, CM, and PM components (and the DD components in embodiments where the DD components are polypeptides), and the like. Thus, the resulting dimer may have symmetrical or asymmetrical monomer construct components. In some embodiments, the first monomer construct comprises, from N- to C-terminus of the CP and CM components, the PM1, the CM3, the CPI, the CM1, and, linked directly or indirectly (via a linker) to the C-terminus of the CM1, the DD1. In other embodiments, the first monomer construct comprises from C- to N- terminus of the CP and CM components, the PM1, the CM3, the CPI, the CM1, and, linked directly or indirectly (via a linker) to the N-terminus of the CM1, the DD1. In some embodiments, the second monomer construct comprises, from N- to C- terminal terminus of the CP and CM components, the PM2, the CM4, the CP2, the PM2, the CM2, and, linked directly or indirectly (via a linker) to the C-terminus of the CM2, the DD2. In other embodiments, the second monomer construct comprises, from C- to N- terminus of the CP and CM components, the PM2, the CM4, the CP2, the PM2, the CM2, and, linked directly or indirectly (via a linker) to the N-terminus of the CM2, the DD2. In one example, the first monomer construct comprises a first polypeptide that comprises the PM1, the CM3, the CPI, the CM1, and the DD1. In one example, the second monomer construct comprises a second polypeptide that comprises the CP2, the CM2, and the DD2. In another example, second monomer construct comprises a second polypeptide that comprises the PM2, the CM4, the CP2, the CM2, and the DD2. In some embodiments, the CP and DD components are linked by a linker that is not cleavable by a protease. For example, the CP and DD components may be linked by a non-cleavable substrate sequence (NSUB). In some embodiments, one of the first and second monomer constructs comprises a NSUB between the CP and DD, and the other comprises a CM between the CP and DD. In some aspects, the linker may be an amino acid substrate sequence that includes glycine and serine residues, but is not susceptible to protease cleavage. Examples of non-cleavable linker sequences include those described in U.S. Patent No. 10,611,845B2, which is incorporated by reference herein by its entirety. In such cases, the CP and / or the DD may have a cleavage site for a protease. Examples of the ACCs in the present disclosure can be presented by the following formulae (in the form of monomer 1 / monomer 2, from the N-terminus to the C-terminus in each monomer) PM1-CM3-CP1-CM1-DD1 / PM2-CM4-CP2-CM2-DD2 PM1-CM3-CP1-CM1-DD1 / CP2-CM2-DD2 DD1-CM1-CP1-CM3-PM1 / DD2-CM2-CP2-CM4-PM2 DD1-CM1-CP1-CM3-PM1 / DD2-CM2-CP2 The ACCs may comprise one or more linkers between the components. For example, the ACCs may comprise one or more linkers between PM and CP, and / or between CP and DD. Thus, as used herein and unless otherwise stated, each dash (-) between the ACC components represents either a direct linkage or linkage via one or more linkers. In some aspects, when the ACC has an orientation of N-PM-CM1-CP-CM2-DD-C, then the entire span of amino acids from the N-terminus of the ACC to the N-terminal amino acid of the cytokine is 17 to 71 amino acids in length. In some aspects, when the ACC has an orientation of N-DD-CM1-CP-CM2-PM-C, then the entire span of amino acids from the C-terminus of the ACC to the C-terminal amino acid of the cytokine is 17 to 71 amino acids in length. In certain embodiments, the first and second monomeric constructs are oriented such that the components in each member of the dimer are organized in the same order from N-terminus to C-terminus of the CP and CM components. A schematic of an illustrative ACC is provided in Fig. 1. With reference to Fig. 1, the ACC comprises, from N-terminus to C-terminus: (1) a first monomer construct 110 having a PM1 119, a CM3 117, a CPI 115, a CM1 113, and a DD1 111, and; (2) a second monomer construct 120 having optionally a PM2 129 and a CM4 127, a CP2 125, a CM2 123, and a DD2 121; and (3) one or more covalent or non-covalent bonds bonding the first monomer construct 110 to the second monomer construct 120. The ACC may further comprise one or more of the optional linkers 112, 114, 116, 118, 122, 124, 126, and 128 between the components. In one example, DD1 111 and DD2 121 are the same. In another example, DD1 111 and DD2 121 are different. A schematic of a further illustrative ACC, with its components organized in the reverse orientation of the ACC is provided in Fig. 2. With reference to Fig. 2, the ACC comprises, from N-terminus to C-terminus of the CP and CM components: (1) a first monomer construct 210 having a DD1 211, a CM1 213, a CPI 215, a CM3 217, and a PM1 219; (2) a second monomer construct 220 having a DD2 221, a CM2 223, a CP2 225, and optionally a CM4 227 and a PM2 229; and (3) one or more covalent or non-covalent bonds (^-->) bonding the first monomer construct 210 to the second monomer construct 220. The ACC may further comprise one or more of the optional linkers 212, 214, 216, 218, 222, 224, 226, and 228 between the components. In one example, DD1 211 and DD2 221 are the same. In another example, DD1 211 and DD2 221 are different. A schematic of another illustrative ACC is provided in Fig. 3. With reference to Fig. 3, the ACC comprises, from N-terminus to C-terminus: (1) a first monomer construct 310 having a PM1 319, a CM3 317, a CPI 315, a CM1 313, andaDDl 311; and (2) a second monomer construct 320 having a CP2 325, a CM2 323, and a DD2 321, and optionally a PM2 329 and a CM4 327. DD1 311 and DD2 321 are binding partners, e.g., a ligand / receptor pair or an antigen / antigen-binding peptide pair, so that DD1 and DD2 are covalently or non-covalently bound together. The ACC may further comprise one or more of the optional linkers 312, 314, 316, 318, 322, 324, 326, and 328 between the components. In one example, DD1 311 and DD2 321 are the same. In another example, DD1 311 and DD2 321 are different. In alternative aspects, one of the two moi eties depicted as CPI 315 and CP2 325 is a truncated cytokine protein that lacks cytokine activity. For example, either CPI or CP2 may be a truncated interferon alpha 2b having the first 151 amino acids of wild-type interferon alpha 2b. In alternative aspects, one of the two moieties depicted as CPI 315 and CP2 325 is a mutated cytokine protein that lacks cytokine activity. For example, either CPI or CP2 may be a truncated interferon alpha 2b having a L130P mutation (e.g., SEQ ID NO: 298). In alternative aspects, one of the two moieties depicted as CPI 315 and CP2 325 is a polypeptide sequence that lacks cytokine activity, e.g., a signal moiety and / or a stub sequence. In alternative aspects, a first one of the two moieties depicted as CPI 315 and CP2 325 is a polypeptide sequence that binds with high affinity to a second one of the two moieties depicted as CPI 315 and CP2 325 and reduces the cytokine activity of the second moiety as compared to the control level of the second moiety. A schematic of another illustrative ACC, with its components organized in the reverse orientation, is provided in Fig. 4. With reference to Fig. 4, the ACC comprises, from N-terminus to C-terminus of the CP and CM components: (1) a first monomer construct 410 having a DD1 411, a CM1 413, a CPI 415, a CM3 417, and a PM1 419; and (2) a second monomer construct 420 having a DD2 421, a CM2 423, a CP2 425, and optionally a CM4 427 and a PM2 429. DD1 411 and DD2 421 are binding partners, e.g., a ligand / receptor pair or an antigen / antigen-binding peptide pair, so that DD1 and DD2 are covalently or non-covalently bound together. The ACC may further comprise one or more of the optional linkers 412, 414, 416, 418, 422, 424, 426, and 428 between the components. In one example, DD1 411 and DD2 421 are the same. In another example, DD1 411 and DD2 421 are different. In certain aspects of the present disclosure, the PM1 and PM2 depicted in the figures may be absent in ACCs used in combination with an anti-PDl or anti-PD-Ll antibody. The ACC structure was discovered to be highly effective at reducing activity of the mature cytokine protein components in a way that does not lead to substantially impaired cytokine activity after activation. The CP’s activity in the ACC may be reduced by both the structure of the ACC (e.g., the dimer structure) and the peptide mask(s) in the ACC. In some embodiments, the activation condition for the ACCs described herein is exposure to one or more proteases that can dissociate the CP from both the DD and the PM. For example, the one or more proteases may cleave the CM between the CP and the PM and the CM between the CP and the DD. As demonstrated in the Examples, activation of the ACC resulted in substantial recovery of cytokine activity. The results suggest that conformation of the cytokine components was not irreversibly altered within the context of the ACC. Significantly, the inventors have discovered that the present structure, utilizing both a dimerization domain and one or more peptide masks that have specific binding affinity for the cytokine protein appears to result in a substantial masking effect achieved over use of either a peptide mask alone or a dimerization domain alone. The ACC may employ any of a variety of mature cytokine proteins, cleavable moieties, peptide masks, and dimerization domains as the CPI, CP2, CM1, CM2, CM3, CM4, PM1, PM2, DD1, and DD2, respectively. For example, any of a variety of mature cytokine proteins that are known in the art or sequence and / or truncation variants thereof, may be suitable for use as either or both CPI and CP2 components of the ACC. The mature cytokine proteins, CPI and CP2 may be the same or different. In certain specific embodiments, CPI and CP2 are the same. In other embodiments, CPI and CP2 are different. The ACC may comprise additional amino acid residues at either or both N-and / or C-terminal ends of the CPI and / or CP2. In some embodiments, the CPI and / or the CP2 may each independently comprise a mature cytokine protein selected from the group of: an interferon (such as, for example, an interferon alpha, an interferon beta, an interferon gamma, an interferon tau, and an interferon omega), an interleukin (such as, for example, IL-la, IL-ip, IL-IRA, IL-18, IL-2, IL-4, IL-7, IL-9, IL-13, IL-15, IL-3, IL-5, GM-CSF, IL-6, IL-11, IL-21), G-CSF, IL-12, LIF, OSM, IL-10, IL-20, IL-14, IL-16, IL-17, CD154, LT-p, TNF-a, TNF-p, 4-1BBL, APRIL, CD27, CD70, CD153, CD178, GITRL, LIGHT, OX40L, OX40, TALL-1, TRAIL, TWEAK, TRANCE, TGF-pl, TGF-p2, TGF-p3, EPOo, TPO, Flt-3L, SCF, M-58 CSF, and MSP, and the like, as well as sequence and truncation variants thereof. In particular, an ACC for use in combination may contain 11,-2, IL-7, IL-8, IL-10, IL-12. ILIA, IL-21, an IFN-alpha, an IFN beta, an IFN gamma, GM-CSF, TGF-beta, LIGHT, GITR-L, CD40L, CD27L, 4-1BB-L, OX40, 0X4OL For example, sequences of such proteins include those in Table 23 and additional examples of the sequences can be obtained from ncbi.nlm.nih.gov / protein. Truncation variants that are suitable for use in the ACCs of the present invention include any N- or C- terminally truncated cytokine that retains a cytokine activity. Exemplary truncation variants employed in the present invention include any of the truncated cytokine polypeptides that are known in the art (see, e.g., Slutzki et al., J. Mol. Biol. 360:1019-1030, 2006, and US 2009 / 0025106), as well as cytokine polypeptides that are N- and / or C-terminally truncated by 1 to about 40 amino acids, 1 to about 35 amino acids, 1 to about 30 amino acids, 1 to about 25 amino acids, 1 to about 20 amino acids, 1 to about 15 amino acids, 1 to about 10 amino acids, 1 to about 8 amino acids, 1 to about 6 amino acids, 1 to about 4 amino acids, that retain a cytokine activity. In some of the foregoing embodiments, the truncated CP is an N-terminally truncated CP. In other embodiments, the truncated CP is a C-terminally truncated CP. In certain embodiments, the truncated CP is a C- and an N-terminally truncated CP. In some embodiments, the CPI and / or the CP2 each independently comprise an amino acid sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to a cytokine reference sequence selected from the group consisting of: SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103, SEQ ID NO: 104, SEQ ID NO: 105, SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108, SEQ ID NO: 109, SEQ ID NO: 110, SEQ ID NO: 111, SEQ ID NO: 112, SEQ ID NO: 113, SEQ ID NO: 114, SEQ ID NO: 115, SEQ ID NO: 116, SEQ ID NO: 117, SEQ ID NO: 118, SEQ ID NO: 119, SEQ ID NO: 12, SEQ ID NO: 121, SEQ ID NO: 122, SEQ ID NO: 123, SEQ ID NO: 124, SEQ ID NO: 125, SEQ ID NO: 126, SEQ ID NO: 127, SEQ ID NO: 128, SEQ ID NO: 129, SEQ ID NO: 130, SEQ ID NO: 131, SEQ ID NO: 132, SEQ ID NO: 133, SEQ ID NO: 134, SEQ ID NO: 135, SEQ ID NO: 136, SEQ ID NO: 137, SEQ ID NO: 138, SEQ ID NO: 139, SEQ ID NO: 140, SEQ ID NO: 141, SEQ ID NO: 142, SEQ ID NO: 143, SEQ ID NO: 144, SEQ ID NO: 145, SEQ ID NO: 146, SEQ ID NO: 147, SEQ ID NO: 148, SEQ ID NO: 149, SEQ ID NO: 150, SEQ ID NO: 151, SEQ ID NO: 152, SEQ ID NO: 153, SEQ ID NO: 154, SEQ ID NO: 155, SEQ ID NO: 156, SEQ ID NO: 157, SEQ ID NO: 158, SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 162, SEQ ID NO: 163, SEQ ID NO: 164, SEQ ID NO: 165, SEQ ID NO: 166, SEQ ID NO: 167, SEQ ID NO: 168, SEQ ID NO: 169, SEQ ID NO: 170, SEQ ID NO: 171, SEQ ID NO: 172, SEQ ID NO: 173, SEQ ID NO: 174, SEQ ID NO: 175, SEQ ID NO: 176, SEQ ID NO: 177, SEQ ID NO: 178, SEQ ID NO: 179, SEQ ID NO: 180, SEQ ID NO: 181, SEQ ID NO: 182, SEQ ID NO: 183, SEQ ID NO: 184, SEQ ID NO: 185, SEQ ID NO: 186, SEQ ID NO: 187, SEQ ID NO: 188, SEQ ID NO: 189, SEQ ID NO: 190, SEQ ID NO: 191, SEQ ID NO: 192, SEQ ID NO: 193, SEQ ID NO: 194, SEQ ID NO: 195, SEQ ID NO: 196, SEQ ID NO: 197, SEQ ID NO: 198, SEQ ID NO: 199, SEQ ID NO: 200, SEQ ID NO: 201, SEQ ID NO: 202, SEQ ID NO: 203, SEQ ID NO: 204, SEQ ID NO: 205, SEQ ID NO: 206, SEQ ID NO: 207, SEQ ID NO: 208, and SEQ ID NO: 209. The percentage of sequence identity refers to the level of amino acid sequence identity between two or more peptide sequences when aligned using a sequence alignment program, e.g., the suite of BLAST programs, publicly available on the Internet at the NCBI website. See also Altschul et al., J. Mol. Biol. 215:403-10, 1990. In some aspects, the ACC includes an interferon alpha 2b mutant, for example, an interferon alpha 2b molecule having a mutation at position L130, e.g., L130P mutation relative to SEQ ID NO: 1 (e.g., SEQ ID NO: 298), as either CPI or CP2. In some aspects, the ACC includes an interferon alpha 2b mutant having a mutation at position 124, F64,160,163, F64, W76,1116, LI 17, F123, or L128, or a combination thereof. For example, the interferon alpha 2b mutant may include mutations 1116 to T, N. or R; L128 to N, H, or R; 124 to P or Q; LI 17H; or L128T, or a combination thereof. In some aspects, the interferon alpha 2b mutant may include mutations I24Q, I60T, F64A, W76H, I116R, and L128N, or a subset thereof. In some aspects, the ACC includes as one of CPI and CP2 a truncated interferon alpha 2b molecule that lacks cytokine activity. For example, the truncated interferon alpha 2b may consist of 151 or fewer amino acids of interferon alpha 2b, e.g., any one of amino acids in the wild-type interferon alpha 2b sequence from N to C-terminus: 1 to 151, 1 to 150, 1 to 149, 1 to 148, . . . 1 to 10, 1 to 9, 1 to 8, 1 to 7, 1 to 6, or 2 to 151, 3 to 151, 4 to 151, 5 to 150, 6 to 149, 7 to 148, 8 to 147, or any intervening sequence of amino acids or mutants thereof. In certain specific embodiments, the CPI and / or the CP2 comprise an interferon. Interferons that are suitable for use in the constructs of the present invention as CPI and / or CP2 include, for example, an interferon-alpha, an interferon-beta, an interferongamma, an interferon-omega, and an interferon-tau. In some embodiments, when the interferon is an interferon alpha, it may be an interferon alpha-2a, an interferon alpha-2b, or an interferon alpha-n3. Further examples of interferon alpha include interferon alpha-1, interferon alpha-4, interferon alpha-5, interferon alpha-6, interferon alpha-7, interferon alpha-8, interferon alpha-10, interferon alpha-13, interferon alpha-14, interferon alpha-16, interferon alpha-17, and interferon alpha-21. In some embodiments, the interferon is a recombinant or purified interferon alpha. In certain embodiments, when the interferon is an interferon-beta, it is selected from the group consisting of an interferon beta-la and an interferon beta-lb. In some embodiments, the CPI and / or the CP2 comprises an IFab domain, which is a conserved protein domain found in interferon alpha or interferon beta. The IFab domain is responsible for the cytokine release and antivirus functions of interferons. Exemplary IFab sequences are provided in SEQ ID Nos: 449-458. In one example, the CPI and the CP2 are different interferons. In another example, the CPI and the CP2 are the same interferon. In some embodiments, the CPI and / or the CP2 exhibit(s) an interferon activity and include(s) an amino acid sequence that is at least 80% identical, at least 82% identical, at least 84% identical, at least 86% identical, at least 88% identical, at least 90% identical, at least 92% identical, at least 94% identical, at least 96% identical, at least 98% identical, or at least 99% identical, or 100% identical to an interferon alpha reference sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103, SEQ ID NO: 104, and SEQ ID NO: 105. In certain specific embodiments, the interferon alpha reference sequence is SEQ ID NO: 1 (human interferon alpha-2b). In some embodiments, the CPI and / or the CP2 comprise a mature alpha interferon having an amino acid sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103, SEQ ID NO: 104, and SEQ ID NO: 105. In certain embodiments, the CPI and / or the CP2 comprise a mature human alpha interferon having the amino acid sequence of SEQ ID NO: 1. In some of the above-described embodiments, the CPI and the CP2 comprise the same amino acid sequence. In other embodiments, the CPI and / or the CP2 exhibit(s) an interferon activity and include(s) an amino acid sequence that is at least 80% identical, at least 82% identical, at least 84% identical, at least 86% identical, at least 88% identical, at least 90% identical, at least 92% identical, at least 94% identical, at least 96% identical, at least 98% identical, or at least 99% identical, or 100% identical to an interferon beta reference sequence selected from the group consisting of SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108, and SEQ ID NO: 109. In certain embodiments, the interferon beta reference sequence is a human interferon beta reference sequence selected from the group consisting of SEQ ID NO: 106 and SEQ ID NO: 107. In some embodiments, the CPI and / or the CP2 comprise a mature beta interferon having an amino acid sequence selected from the group consisting of SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108, and SEQ ID NO: 109. In some of the above-described embodiments, the CPI and the CP2 comprise the same amino acid sequence. In some embodiments, the CPI and / or CP2 exhibit(s) an interferon activity and include(s) an amino acid sequence that is at least 80% identical, at least 82% identical, at least 84% identical, at least 86% identical, at least 88% identical, at least 90% identical, at least 92% identical, at least 94% identical, at least 96% identical, at least 98% identical, or at least 99% identical, or 100% identical to an interferon omega reference sequence corresponding to SEQ ID NO: 110 (human interferon omega). In certain specific embodiments, the CPI and / or CP2 comprise a mature human omega interferon having the amino acid sequence of SEQ ID NO: 110. In some of the above-described embodiments, the CPI and the CP2 comprise the same amino acid sequence. In some embodiments, the CPI and / or the CP2 exhibit(s) an interleukin activity and include(s) an amino acid sequence that is at least 80% identical, at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical or 100% identical to an interleukin reference sequence selected from the group consisting of: SEQ ID NO: 111, SEQ ID NO: 112, SEQ ID NO: 113, SEQ ID NO: 114, SEQ ID NO: 115, SEQ ID NO: 116, SEQ ID NO: 117, SEQ ID NO: 118, SEQ ID NO: 119, SEQ ID NO: 12 , SEQ ID NO: 121, SEQ ID NO: 122, SEQ ID NO: 123, SEQ ID NO: 124, SEQ ID NO: 125, SEQ ID NO: 126, SEQ ID NO: 127, SEQ ID NO: 128, SEQ ID NO: 129, SEQ ID NO: 130, SEQ ID NO: 131, SEQ ID NO: 132, SEQ ID NO: 133, SEQ ID NO: 134, SEQ ID NO: 135, SEQ ID NO: 136, SEQ ID NO: 137, SEQ ID NO: 138, SEQ ID NO: 139, SEQ ID NO: 140, SEQ ID NO: 143, SEQ ID NO: 144, SEQ ID NO: 145, SEQ ID NO: 146, SEQ ID NO: 151, SEQ ID NO: 152, SEQ ID NO: 153, SEQ ID NO: 154, SEQ ID NO: 155, SEQ ID NO: 156, SEQ ID NO: 157, SEQ ID NO: 158, SEQ ID NO: 159, and SEQ ID NO: 160. In some embodiments, CPI and / or CP2 comprises a mature interleukin having an amino acid sequence selected from the group consisting of: SEQ ID NO: 111, SEQ ID NO: 112, SEQ ID NO: 113, SEQ ID NO: 114, SEQ ID NO: 115, SEQ ID NO: 116, SEQ ID NO: 117, SEQ ID NO: 118, SEQ ID NO: 119, SEQ ID NO: 12 , SEQ ID NO: 121, SEQ ID NO: 122, SEQ ID NO: 123, SEQ ID NO: 124, SEQ ID NO: 125, SEQ ID NO: 126, SEQ ID NO: 127, SEQ ID NO: 128, SEQ ID NO: 129, SEQ ID NO: 130, SEQ ID NO: 131, SEQ ID NO: 132, SEQ ID NO: 133, SEQ ID NO: 134, SEQ ID NO: 135, SEQ ID NO: 136, SEQ ID NO: 137, SEQ ID NO: 138, SEQ ID NO: 139, SEQ ID NO: 140, SEQ ID NO: 143, SEQ ID NO: 144, SEQ ID NO: 145, SEQ ID NO: 146, SEQ ID NO: 151, SEQ ID NO: 152, SEQ ID NO: 153, SEQ ID NO: 154, SEQ ID NO: 155, SEQ ID NO: 156, SEQ ID NO: 157, SEQ ID NO: 158, SEQ ID NO: 159, and SEQ ID NO: 160. In some of the above-described embodiments, the CPI and the CP2 comprise the same amino acid sequence. In some embodiments, CPI and / or CP2 exhibit(s) an interleukin activity and include(s) an amino acid sequence that is at least 80% identical, at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to an interleukin reference sequence selected from the group consisting of SEQ ID NO: 111 (human IL-1 alpha), SEQ ID NO: 113 (human IL-1 beta), SEQ ID NO: 115 (human IL-IRA), SEQ ID NO: 117 (human IL-18), SEQ ID NO: 119 (human IL-2), SEQ ID NO: 121 (human IL-4), SEQ ID NO: 123 (human IL-7), SEQ ID NO: 125 (human IL-9), SEQ ID NO: 127 (human IL-13), SEQ ID NO: 129 (human IL-15), SEQ ID NO: 131 (human IL-3), SEQ ID NO: 133 (human IL-5), SEQ ID NO: 137 (human IL-6), SEQ ID NO: 139 (human IL- 11), SEQ ID NO: 143 (human IL-12 alpha), SEQ ID NO: 144 (human IL-12 beta), SEQ ID NO: 151 (human IL-10), SEQ ID NO: 153 (human IL-20); SEQ ID NO: 155 (human IL-14), SEQ ID NO: 157 (human IL-16), and SEQ ID NO: 159 (human IL-17). In certain of these embodiments, CPI and / or CP2 comprise an amino acid sequence from the group consisting of SEQ ID NO: 111 (human IL-1 alpha), SEQ ID NO: 113 (human IL-1 beta), SEQ ID NO: 115 (human IL-IRA), SEQ ID NO: 117 (human IL-18), SEQ ID NO: 119 (human IL-2), SEQ ID NO: 121, SEQ ID NO: 123 (human IL-7), SEQ ID NO: 125 (human IL-9), SEQ ID NO: 127 (human IL-13), SEQ ID NO: 129 (human IL-15), SEQ ID NO: 131 (human IL-3), SEQ ID NO: 133 (human IL-5), SEQ ID NO: 137 (human IL-6), SEQ ID NO: 139 (human IL-11), SEQ ID NO: 143 (human IL-12 alpha), SEQ ID NO: 144 (human IL-12 beta), SEQ ID NO: 151 (human IL-10), SEQ ID NO: 153 (human IL-20); SEQ ID NO: 155 (human IL-14), SEQ ID NO: 157 (human IL-16), and SEQ ID NO: 159 (human IL-17). In some of the above-described embodiments, the CPI and the CP2 comprise the same amino acid sequence. The number of amino acids in the sequence of the cytokine proteins employed may vary, depending on the specific cytokine protein employed. In some embodiments, the CPI and / or the CP2 includes a total of about 10 amino acids to about 700 amino acids, about 10 amino acids to about 650 amino acids, about 10 amino acids to about 600 amino acids, about 10 amino acids to about 550 amino acids, about 10 amino acids to about 500 amino acids, about 10 amino acids to about 450 amino acids, about 10 amino acids to about 400 amino acids, about 10 amino acids to about 350 amino acids, about 10 amino acids to about 300 amino acids, about 10 amino acids to about 250 amino acids, about 10 amino acids to about 200 amino acids, about 10 amino acids to about 150 amino acids, about 10 amino acids to about 100 amino acids, about 10 amino acids to about 80 amino acids, about 10 amino acids to about 60 amino acids, about 10 amino acids to about 40 amino acids, about 10 amino acids to about 20 amino acids, about 20 amino acids to about 700 amino acids, about 20 amino acids to about 650 amino acids, about 20 amino acids to about 600 amino acids, about 20 amino acids to about 550 amino acids, about 20 amino acids to about 500 amino acids, about 20 amino acids to about 450 amino acids, about 20 amino acids to about 400 amino acids, about 20 amino acids to about 350 amino acids, about 20 amino acids to about 300 amino acids, about 20 amino acids to about 250 amino acids, about 20 amino acids to about 200 amino acids, about 20 amino acids to about 150 amino acids, about 20 amino acids to about 100 amino acids, about 20 amino acids to about 80 amino acids, about 20 amino acids to about 60 amino acids, about 20 amino acids to about 40 amino acids, about 40 amino acids to about 700 amino acids, about 40 amino acids to about 650 amino acids, about 40 amino acids to about 600 amino acids, about 40 amino acids to about 550 amino acids, about 40 amino acids to about 500 amino acids, about 40 amino acids to about 450 amino acids, about 40 amino acids to about 400 amino acids, about 40 amino acids to about 350 amino acids, about 40 amino acids to about 300 amino acids, about 40 amino acids to about 250 amino acids, about 40 amino acids to about 200 amino acids, about 40 amino acids to about 150 amino acids, about 40 amino acids to about 100 amino acids, about 40 amino acids to about 80 amino acids, about 40 amino acids to about 60 amino acids, about 60 amino acids to about 700 amino acids, about 60 amino acids to about 650 amino acids, about 60 amino acids to about 600 amino acids, about 60 amino acids to about 550 amino acids, about 60 amino acids to about 500 amino acids, about 60 amino acids to about 450 amino acids, about 60 amino acids to about 400 amino acids, about 60 amino acids to about 350 amino acids, about 60 amino acids to about 300 amino acids, about 60 amino acids to about 250 amino acids, about 60 amino acids to about 200 amino acids, about 60 amino acids to about 150 amino acids, about 60 amino acids to about 100 amino acids, about 60 amino acids to about 80 amino acids, about 80 amino acids to about 700 amino acids, about 80 amino acids to about 650 amino acids, about 80 amino acids to about 600 amino acids, about 80 amino acids to about 550 amino acids, about 80 amino acids to about 500 amino acids, about 80 amino acids to about 450 amino acids, about 80 amino acids to about 400 amino acids, about 80 amino acids to about 350 amino acids, about 80 amino acids to about 300 amino acids, about 80 amino acids to about 250 amino acids, about 80 amino acids to about 200 amino acids, about 80 amino acids to about 150 amino acids, about 80 amino acids to about 100 amino acids, about 100 amino acids to about 700 amino acids, about 100 amino acids to about 650 amino acids, about 100 amino acids to about 600 amino acids, about 100 amino acids to about 550 amino acids, about 100 amino acids to about 500 amino acids, about 100 amino acids to about 450 amino acids, about 100 amino acids to about 400 amino acids, about 100 amino acids to about 350 amino acids, about 100 amino acids to about 300 amino acids, about 100 amino acids to about 250 amino acids, about 100 amino acids to about 200 amino acids, about 100 amino acids to about 150 amino acids, about 150 amino acids to about 700 amino acids, about 150 amino acids to about 650 amino acids, about 150 amino acids to about 600 amino acids, about 150 amino acids to about 550 amino acids, about 150 amino acids to about 500 amino acids, about 150 amino acids to about 450 amino acids, about 150 amino acids to about 400 amino acids, about 150 amino acids to about 350 amino acids, about 150 amino acids to about 300 amino acids, about 150 amino acids to about 250 amino acids, about 150 amino acids to about 200 amino acids, about 200 amino acids to about 700 amino acids, about 200 amino acids to about 650 amino acids, about 200 amino acids to about 600 amino acids, about 200 amino acids to about 550 amino acids, about 200 amino acids to about 500 amino acids, about 200 amino acids to about 450 amino acids, about 200 amino acids to about 400 amino acids, about 200 amino acids to about 350 amino acids, about 200 amino acids to about 300 amino acids, about 200 amino acids to about 250 amino acids, about 250 amino acids to about 700 amino acids, about 250 amino acids to about 650 amino acids, about 250 amino acids to about 600 amino acids, about 250 amino acids to about 550 amino acids, about 250 amino acids to about 500 amino acids, about 250 amino acids to about 450 amino acids, about 250 amino acids to about 400 amino acids, about 250 amino acids to about 350 amino acids, about 250 amino acids to about 300 amino acids, about 300 amino acids to about 700 amino acids, about 300 amino acids to about 650 amino acids, about 300 amino acids to about 600 amino acids, about 300 amino acids to about 550 amino acids, about 300 amino acids to about 500 amino acids, about 300 amino acids to about 450 amino acids, about 300 amino acids to about 400 amino acids, about 300 amino acids to about 350 amino acids, about 350 amino acids to about 700 amino acids, about 350 amino acids to about 650 amino acids, about 350 amino acids to about 600 amino acids, about 350 amino acids to about 550 amino acids, about 350 amino acids to about 500 amino acids, about 350 amino acids to about 450 amino acids, about 350 amino acids to about 400 amino acids, about 400 amino acids to about 700 amino acids, about 400 amino acids to about 650 amino acids, about 400 amino acids to about 600 amino acids, about 400 amino acids to about 550 amino acids, about 400 amino acids to about 500 amino acids, about 400 amino acids to about 450 amino acids, about 450 amino acids to about 700 amino acids, about 450 amino acids to about 650 amino acids, about 450 amino acids to about 600 amino acids, about 450 amino acids to about 550 amino acids, about 450 amino acids to about 500 amino acids, about 500 amino acids to about 700 amino acids, about 500 amino acids to about 650 amino acids, about 500 amino acids to about 600 amino acids, about 500 amino acids to about 550 amino acids, about 550 amino acids to about 700 amino acids, about 550 amino acids to about 650 amino acids, about 550 amino acids to about 600 amino acids, about 600 amino acids to about 700 amino acids, about 600 amino acids to about 650 amino acids, or about 650 amino acids to about 700 amino acids. In some embodiments, CPI and / or the CP2 is a mature wildtype human cytokine protein. Each monomer construct of the ACC may employ any of a variety of dimerization domains. Suitable DDs include both polymeric (e.g., a synthetic polymer, a polypeptide, a polynucleotide, and the like) and small molecule (non-polymeric moieties having a molecular weight of less than about 1 kilodalton, and sometimes less than about 800 daltons) types of moieties. The pair of DDs may be any pair of moieties that are known in the art to bind to each other. For example, in some embodiments, the DD1 and the DD2 are members of a pair selected from the group of: a sushi domain from an alpha chain of human IL-15 receptor (IL15Ra) and a soluble IL-15; barnase and bamstar; a protein kinase A (PKA) and an A-kinase anchoring protein (AKAP); adapter / docking tag molecules based on mutated RNase I fragments; a pair of antigen-binding domains (e.g., a pair of single domain antibodies); soluble N-ethyl-maleimide sensitive factor attachment protein receptors (SNARE); modules based on interactions of the proteins syntaxin, synaptotagmin, synaptobrevin, and SNAP25; a single domain antibody (sdAb) and corresponding epitope; an antigen-binding domain (e.g., a single chain antibody such as a single chain variable fragment (scFv), a single domain antibody, and the like) and a corresponding epitope; coiled coil polypeptide structions (e.g., Fos-Jun coiled coil structures, acid / base coiled-coil helices, Glu-Lys coiled coil helices, leucine zipper structures), small molecule binding pairs such as biotin and avidin or streptavidin, amine / aldehyde, lectin / carbohydrate; a pair of polymers that can bind each other, such as, for example, a pair of sulfur- or thiol-containing polymers (e.g., a pair of Fc domains, a pair of thiolized-human serum albumin polypeptides, and the like); and the like. In some embodiments, the DD1 and DD2 are non-polypeptide polymers. The non-polypeptide polymers may covalently bound to each other. In some examples, the non-polypeptide polymers may be a sulfur-containing polymer, e.g., sulfur-containing polyethylene glycol. In such cases, the DD1 and DD2 may be covalently bound to each other via one or more disulfide bonds. When the pair of DD1 and DD2 are members of a pair of epitope and antigenbinding domain, the epitope may be a naturally or non-naturally occurring epitope. Exemplary non-naturally occurring epitopes include, for example, a non-naturally occurring peptide, such as, for example, a poly-His peptide (e.g., a His tag, and the like). In certain specific embodiments, the DD1 and the DD2 are a pair of Fc domains. As used herein, an “Fc domain” refers to a contiguous amino acid sequence of a single heavy chain of an immunoglobulin. A pair of Fc domains associate together to form an Fc region of an immunoglobulin. In some embodiments, the pair of Fc domains is a pair of human Fc domains (e.g., a pair of wildtype human Fc domains). In some embodiments, the human Fc domains are human IgGl Fc domains (e.g., wildtype human IgGl Fc domains), human IgG2 Fc domains (e.g., wildtype human IgG2 Fc domains), human IgG3 Fc domains (e.g., wildtype human IgG3 Fc domains), or human IgG4 Fc domains (e.g., wildtype human IgG4 Fc domains). In some embodiments, the human Fc domains comprise a sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to SEQ ID NO: 3. In some embodiments, the pair of Fc domains comprise a knob mutant and a hole mutant of a Fc domain. The knob and hole mutants may interact with each other to facilitate the dimerization. In some embodiments, the knob and hole mutants may comprise one or more amino acid modifications within the interface between two Fc domains (e.g., in the CH3 domain). In one example, the modifications comprise amino acid substitution T366W and optionally the amino acid substitution S354C in one of the antibody heavy chains, and the amino acid substitutions T366S, L368A, Y407V and optionally Y349C in the other one of the antibody heavy chains (numbering according to EU index of Kabat numbering system). Examples of the knob and hole mutants include Fc mutants of SEQ ID NOs: 287 and 288, as well as those described in U.S. Pat. Nos. 5,731,168; 7,695,936; and 10,683,368, which are incorporated herein by reference in their entireties. In some embodiments, the dimerization domains comprise a sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to SEQ ID NOs: 287 and 288, respectively. In some embodiments, DD1 and / or DD2 can further include a serum half-life extending moiety (e.g., polypeptides that bind serum proteins, such as immunoglobulin (e.g., IgG) or serum albumin (e.g., human serum albumin (HSA)). Examples of half-life extending moieties include hexa-hat GST (glutathione S-transferase) glutathione affinity, Calmodulin-binding peptide (CBP), Strep-tag, Cellulose Binding Domain, Maltose Binding Protein, S-Peptide Tag, Chitin Binding Tag, Immuno-reactive Epitopes, Epitope Tags, E2Tag, HA Epitope Tag, Myc Epitope, FLAG Epitope, AU1 and AU5 Epitopes, Glu-Glu Epitope, KT3 Epitope, IRS Epitope, Btag Epitope, Protein Kinase-C Epitope, and VSV Epitope. In some embodiments, DD1 and / or DD2 each include a total of about 5 amino acids to about 250 amino acids, about 5 amino acids to about 200 amino acids, about 5 amino acids to about 180 amino acids, about 5 amino acids to about 160 amino acids, about 5 amino acids to about 140 amino acids, about 5 amino acids to about 120 amino acids, about 5 amino acids to about 100 amino acids, about 5 amino acids to about 80 amino acids, about 5 amino acids to about 60 amino acids, about 5 amino acids to about 40 amino acids, about 5 amino acids to about 20 amino acids, about 5 amino acids to about 10 amino acids, about 10 amino acids to about 250 amino acids, about 10 amino acids to about 200 amino acids, about 10 amino acids to about 180 amino acids, about 10 amino acids to about 160 amino acids, about 10 amino acids to about 140 amino acids, about 10 amino acids to about 120 amino acids, about 10 amino acids to about 100 amino acids, about 10 amino acids to about 80 amino acids, about 10 amino acids to about 60 amino acids, about 10 amino acids to about 40 amino acids, about 10 amino acids to about 20 amino acids, about 20 amino acids to about 250 amino acids, about 20 amino acids to about 200 amino acids, about 20 amino acids to about 180 amino acids, about 20 amino acids to about 160 amino acids, about 20 amino acids to about 140 amino acids, about 20 amino acids to about 120 amino acids, about 20 amino acids to about 100 amino acids, about 20 amino acids to about 80 amino acids, about 20 amino acids to about 60 amino acids, about 20 amino acids to about 40 amino acids, about 40 amino acids to about 250 amino acids, about 40 amino acids to about 200 amino acids, about 40 amino acids to about 180 amino acids, about 40 amino acids to about 160 amino acids, about 40 amino acids to about 140 amino acids, about 40 amino acids to about 120 amino acids, about 40 amino acids to about 100 amino acids, about 40 amino acids to about 80 amino acids, about 40 amino acids to about 60 amino acids, about 60 amino acids to about 250 amino acids, about 60 amino acids to about 200 amino acids, about 60 amino acids to about 180 amino acids, about 60 amino acids to about 160 amino acids, about 60 amino acids to about 140 amino acids, about 60 amino acids to about 120 amino acids, about 60 amino acids to about 100 amino acids, about 60 amino acids to about 80 amino acids, about 80 amino acids to about 250 amino acids, about 80 amino acids to about 200 amino acids, about 80 amino acids to about 180 amino acids, about 80 amino acids to about 160 amino acids, about 80 amino acids to about 140 amino acids, about 80 amino acids to about 120 amino acids, about 80 amino acids to about 100 amino acids, about 100 amino acids to about 250 amino acids, about 100 amino acids to about 200 amino acids, about 100 amino acids to about 180 amino acids, about 100 amino acids to about 160 amino acids, about 100 amino acids to about 140 amino acids, about 100 amino acids to about 120 amino acids, about 120 amino acids to about 250 amino acids, about 120 amino acids to about 200 amino acids, about 120 amino acids to about 180 amino acids, about 120 amino acids to about 160 amino acids, about 120 amino acids to about 140 amino acids, about 140 amino acids to about 250 amino acids, about 140 amino acids to about 200 amino acids, about 140 amino acids to about 180 amino acids, about 140 amino acids to about 160 amino acids, about 160 amino acids to about 250 amino acids, about 160 amino acids to about 200 amino acids, about 160 amino acids to about 180 amino acids, about 180 amino acids to about 250 amino acids, about 180 amino acids to about 200 amino acids, or about 200 amino acids to about 250 amino acids. In some embodiments, DD1 and DD2 are each an Fc domain that comprises a portion of the hinge region that includes two cysteine residues, a CH2 domain, and a CH3 domain. In some embodiments, DD1 and DD2 are each an Fc domain whose N-terminus is the first cysteine residue (reading in the N- to C- direction) in the hinge region that participates in a disulfide linkage with a second Fc domain (e.g., Cysteine 226 of human IgGl or IgG4, using EU numbering). In some aspects, positioned between the CP and the DD, and / or between the CP and the PM components, either directly or indirectly (e.g., via a linker), is a cleavable moiety (CM) that comprises a substrate for a protease. In some embodiments, the CMs may each independently comprise a substrate for a protease selected from the group consisting of ADAM8, ADAM9, ADAM10, ADAM12, ADAM I 5, ADAM17 / TACE, ADEMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, Renin, Cathepsin D, Cathepsin E, Caspase 1, Caspase 2, Caspase 3, Caspase 4, Caspase 5, Caspase 6, Caspase 7, Caspase 8, Caspase 9, Caspase 10, Caspase 14, Cathepsin A, Cathepsin B, Cathepsin C, Cathepsin G, Cathepsin K, Cathepsin L, Cathepsin S, Cathepsin V / L2, Cathepsin X / Z / P, Chymase, Cruzipain, DESCI, DPP-4, FAP, Legumain, Otubain-2, Elastase, FVIIa, FiXA, FXa, FXIa, FXIIa, Granzyme B, Guanidinobenzoatase, Hepsin, HtrAl, Human Neutrophil Elastase, KLK4, KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13, KLK14, Lactoferrin, Marapsin, Matriptase-2, Meprin, MT-SPl / Matriptase, Neprilysin, NS3 / 4A, PACE4, Plasmin, PSMA, PSA, BMP-1, MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP11, MMP12, MMP13, MMP14, MMP15, MMP16, MMP17, MMP19, MMP20, MMP23, MMP24, MMP26, MMP27, TMPRSS2, TMPRSS3, TMPRSS4, tPA, Thrombin, Tryptase, and uPA, and any combination of two or more thereof. In some embodiments of any of the ACCs described herein, the protease that cleaves any of the CMs described herein can be ADAM8, ADAM9, ADAMI 0, ADAM12, ADAM15, ADAM17 / TACE, ADAMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, Renin, Cathepsin D, Cathepsin E, Caspase 1, Caspase 2, Caspase 3, Caspase 4, Caspase 5, Caspase 6, Caspase 7, Caspase 8, Caspase 9, Caspase 10, Caspase 14, Cathepsin B, Cathepsin C, Cathepsin K, Cathespin L, Cathepsin S, Cathepsin V / L2, Cathepsin X / Z / P, Cruzipain, Legumain, Otubain-2, KLK4, KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13, KLK14, Meprin, Neprilysin, PSMA, BMP-1, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-10, MMP-11, MMP-12, MMP-13, MMP-14, MMP-15, MMP-16, MMP-17, MMP-19, MMP-20, MMP-23, MMP-24, MMP-26, MMP-27, activated protein C, cathepsin A, cathepsin G, Chymase, FVIIa, FIXa, FXa, FXIa, FXIIa, Elastase, Granzyme B, Guanidinobenzoatase, HtrAl, human neutrophil lyase, lactoferrin, marapsin, NS3 / 4A, PACE4, Plasmin, PSA, tPA, thrombin, tryptase, uPA, DESCI, DPP-4, FAP, Hepsin, Matriptase-2, MT-SPl / Matripase, TMPRSS2, TMPRSS3, and TMPRSS4, and any combination of two or more thereof. In some embodiments of any of the ACCs described herein, the protease is selected from the group of: uPA, legumain, MT-SP1, ADAM17, BMP-1, TMPRSS3, TMPRSS4, MMP-2, MMP-9, MMP-12, MMP-13, and MMP-14. Increased levels of proteases having known substrates have been reported in a number of cancers. See, e.g., La Roca et al., British J. Cancer 90(7): 1414-1421, 2004. Substrates suitable for use in the CMs components employed herein include those which are more prevalently found in cancerous cells and tissue. Thus, in certain embodiments, CMs each independently comprise a substrate for a protease that is more prevalently found in diseased tissue associated with a cancer. In some embodiments, the cancer is selected from the group of: gastric cancer, breast cancer, osteosarcoma, and esophageal cancer. In some embodiments, the cancer is breast cancer. In some embodiments, the cancer is a HER2-positive cancer. In some embodiments, the cancer is Kaposi sarcoma, hairy cell leukemia, chronic myeloid leukemia (CML), follicular lymphoma, renal cell cancer (RCC), melanoma, neuroblastoma, basal cell carcinoma, cutaneous T-cell lymphoma, nasopharyngeal adenocarcimoa, breast cancer, ovarian cancer, bladder cancer, BCG-resistant non-muscle invasive bladder cancer (NMIBC), endometrial cancer, pancreatic cancer, non-small cell lung cancer (NSCLC), colorectal cancer, esophageal cancer, gallbladder cancer, glioma, head and neck carcinoma, uterine cancer, cervical cancer, or testicular cancer, and the like. In some of the above-described embodiments, the CM components comprise substrates for protease(s) that is / are more prevalent in tumor tissue In some embodiments, CMs each independently include(s) a sequence selected from the group consisting of SEQ ID NO: 5 through SEQ ID NO: 100, as well as C-terminal and N-terminal truncation variants thereof. In some embodiments, the CM includes a sequence selected from the group of: ISSGLLSGRSDNH (SEQ ID NO: 28), LSGRSDDH (SEQ ID NO: 33), ISSGLLSGRSDQH (SEQ ID NO: 54), and ISSGLLSGRSDNI (SEQ ID NO: 68). In certain embodiments, CM1 and / or CM1 include(s) a sequence selected from the group of: AQNLLGMY (SEQ ID NO: 237), LSGRSDNHGGAVGLLAPP (SEQ ID NO: 238), VHMPLGFLGPGGLSGRSDNH (SEQ ID NO: 239), LSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 240), LSGRSDNHGGSGGSISSGLLSS (SEQ ID NO: 241), ISSGLLSSGGSGGSLSGRSGNH (SEQ ID NO: 242), LSGRSDNHGGSGGSQNQALRMA (SEQ ID NO: 243), QNQALRMAGGSGGSLSGRSDNH (SEQ ID NO:244), LSGRSGNHGGSGGSQNQALRMA (SEQ ID NO: 245), QNQALRMAGGSGGSLSGRSGNH (SEQ ID NO: 246), ISSGLLSGRSGNH (SEQ ID NO: 247), as well as C-terminal and N-terminal truncation variants thereof. Examples of CMs also include those described in U.S. Patent Application Publication Nos. US20160289324, US20190284283, and in publication numbers WO 2010 / 081173, WO 2015 / 048329, WO 2015 / 116933, WO 2016 / 118629, and WO 2020 / 118109, which are incorporated herein by reference in their entireties. Truncation variants of the aforementioned amino acid sequences that are suitable for use in the CMs are any that retain the recognition site for the corresponding protease. These include C-terminal and / or N-terminal truncation variants comprising at least 3 contiguous amino acids of the above-described amino acid sequences, or at least 4, or at least 5, or at least 6, or at least 7 amino acids of the foregoing amino acid sequences that retain a recognition site for a protease. In certain embodiments, the truncation variant of the above-described amino acid sequences is an amino acid sequence corresponding to any of the above, but that is C- and / or N-terminally truncated by 1 to about 10 amino acids, 1 to about 9 amino acids, 1 to about 8 amino acids, 1 to about 7 amino acids, 1 to about 6 amino acids, 1 to about 5 amino acids, 1 to about 4 amino acids, or 1 to about 3 amino acids, and which: (1) has at least three amino acid residues; and (2) retains a recognition site for a protease. In some of the foregoing embodiments, the truncated CM is an N-terminally truncated CM. In some embodiments, the truncated CM is a C-terminally truncated CM. In some embodiments, the truncated C is a C- and an N-terminally truncated CM. In some embodiments of any of the ACCs or activatable antibodies described herein, the CM may comprise a total of about 3 amino acids to about 25 amino acids. In some embodiments, the CM may comprise a total of about 3 amino acids to about 25 amino acids, about 3 amino acids to about 20 amino acids, about 3 amino acids to about 15 amino acids, about 3 amino acids to about 10 amino acids, about 3 amino acids to about 5 amino acids, about 5 amino acids to about 25 amino acids, about 5 amino acids to about 20 amino acids, about 5 amino acids to about 15 amino acids, about 5 amino acids to about 10 amino acids, about 10 amino acids to about 25 amino acids, about 10 amino acids to about 20 amino acids, about 10 amino acids to about 15 amino acids, about 15 amino acids to about 25 amino acids, about 15 amino acids to about 20 amino acids, or about 20 amino acids to about 25 amino acids. In some embodiments, the ACC, activatable anti-PDl, or activatable anti-PD-Ll may comprise multiple CMs that comprise substrates for different proteases. In some embodiments, the ACC, activatable anti-PDl, or activatable anti-PD-Ll may comprise multiple CMs that are substrates for the same protease. In one example, the CM(s) between each CP and PM may be substrates for the same protease as each other, and the CM(s) between each CP and DD may be substates for the same protease as each other, but may be substrates for a different protease than the CM(s) between the CP and the PM. In another example, the CM(s) between the CP and the PM and the CM(s) between the CP and the DD may comprise substrates for the same protease. In another example, the CM(s) between the CP and the PM may comprise substrates for different proteases. In another example, the CM(s) between the CP and the PM may comprise substrates for the same protease. In another example, the CM(s) between the CP and the DD may comprise substrates for different proteases. In another example, the CM(s) between the CP and the DD may comprise substrates for the same protease. In one example, the CM(s) between each activatable anti-PDl or activatable anti-PD-Ll and MM may be substrates for the same protease as each other. In another example, the CM(s) between the activatable anti- PD1 or activatable anti-PD-Ll and the MM may comprise substrates for different proteases. In another example, the CM(s) between the activatable anti-PDl or activatable anti-PD-Ll and the MM may comprise substrates for the same protease. The first and second monomer constructs may comprise one or more additional components including one or more linkers, and the like. In some embodiments, the first monomer can include a linker disposed between the CPI and the CM1. In some embodiments, the CPI and the CM1 directly abut each other in the first monomer. In some embodiments, the first monomer comprises a linker disposed between the CM1 and the DDL In some embodiments, the CM1 and the DD1 directly abut each other in the first monomer. In some embodiments, the first monomer can include a linker disposed between the CPI and the CM3. In some embodiments, the CPI and the CM3 directly abut each other in the first monomer. In some embodiments, the first monomer can include a linker disposed between the CPI and the PM1. In some embodiments, the CPI and the PM1 directly abut each other in the first monomer. In some embodiments, the linker has a total length of 1 amino acid to about 15 amino acids. In some embodiments, the CM and any linkers disposed between the CPI and DD1 have a combined total length of 3 to 15 amino acids, or 3 to 10 amino acids, or 3 to 7 amino acids. In some embodiments, the second monomer comprises a linker disposed between the CP2 and the CM2. In some embodiments, the CP2 and the CM2 directly abut each other in the second monomer. In some embodiments, the second monomer comprises a linker disposed between the CM2 and the DD2. In some embodiments, the CM2 (e.g., any of the cleavable moi eties described herein) and the DD2 (e.g., any of the DDs described herein) directly abut each other in the second monomer. In some embodiments, the second monomer can include a linker disposed between the CP2 and the CM4. In some embodiments, the CP2 and the CM4 directly abut each other in the second monomer. In some embodiments, the second monomer can include a linker disposed between the CP2 and the PM2. In some embodiments, the CP2 and the PM2 directly abut each other in the second monomer. In some embodiments, the linker has a total length of 1 amino acid to about 15 amino acids. In some embodiments, the linker comprises a sequence of GGGS (SEQ ID NO: 2). In some embodiments, the CM and any linkers disposed between the CP2 and DD2 have a combined total length of 3 to 15 amino acids, or 3 to 10 amino acids, or 3 to 7 amino acids. In some embodiments, the first monomer and / or the second monomer can include a total of about 50 amino acids to about 800 amino acids, about 50 amino acids to about 750 amino acids, about 50 amino acids to about 700 amino acids, about 50 amino acids to about 650 amino acids, about 50 amino acids to about 600 amino acids, about 50 amino acids to about 550 amino acids, about 50 amino acids to about 500 amino acids, about 50 amino acids to about 450 amino acids, about 50 amino acids to about 400 amino acids, about 50 amino acids to about 350 amino acids, about 50 amino acids to about 300 amino acids, about 50 amino acids to about 250 amino acids, about 50 amino acids to about 200 amino acids, about 50 amino acids to about 150 amino acids, about 50 amino acids to about 100 amino acids, about 100 amino acids to about 800 amino acids, about 100 amino acids to about 750 amino acids, about 100 amino acids to about 700 amino acids, about 100 amino acids to about 650 amino acids, about 100 amino acids to about 600 amino acids, about 100 amino acids to about 550 amino acids, about 100 amino acids to about 500 amino acids, about 100 amino acids to about 450 amino acids, about 100 amino acids to about 400 amino acids, about 100 amino acids to about 350 amino acids, about 100 amino acids to about 300 amino acids, about 100 amino acids to about 250 amino acids, about 100 amino acids to about 200 amino acids, about 100 amino acids to about 150 amino acids, about 150 amino acids to about 800 amino acids, about 150 amino acids to about 750 amino acids, about 150 amino acids to about 700 amino acids, about 150 amino acids to about 650 amino acids, about 150 amino acids to about 600 amino acids, about 150 amino acids to about 550 amino acids, about 150 amino acids to about 500 amino acids, about 150 amino acids to about 450 amino acids, about 150 amino acids to about 400 amino acids, about 150 amino acids to about 350 amino acids, about 150 amino acids to about 300 amino acids, about 150 amino acids to about 250 amino acids, about 150 amino acids to about 200 amino acids, about 200 amino acids to about 800 amino acids, about 200 amino acids to about 750 amino acids, about 200 amino acids to about 700 amino acids, about 200 amino acids to about 650 amino acids, about 200 amino acids to about 600 amino acids, about 200 amino acids to about 550 amino acids, about 200 amino acids to about 500 amino acids, about 200 amino acids to about 450 amino acids, about 200 amino acids to about 400 amino acids, about 200 amino acids to about 350 amino acids, about 200 amino acids to about 300 amino acids, about 200 amino acids to about 250 amino acids, about 250 amino acids to about 800 amino acids, about 250 amino acids to about 750 amino acids, about 250 amino acids to about 700 amino acids, about 250 amino acids to about 650 amino acids, about 250 amino acids to about 600 amino acids, about 250 amino acids to about 550 amino acids, about 250 amino acids to about 500 amino acids, about 250 amino acids to about 450 amino acids, about 250 amino acids to about 400 amino acids, about 250 amino acids to about 350 amino acids, about 250 amino acids to about 300 amino acids, about 300 amino acids to about 800 amino acids, about 300 amino acids to about 750 amino acids, about 300 amino acids to about 700 amino acids, about 300 amino acids to about 650 amino acids, about 300 amino acids to about 600 amino acids, about 300 amino acids to about 550 amino acids, about 300 amino acids to about 500 amino acids, about 300 amino acids to about 450 amino acids, about 300 amino acids to about 400 amino acids, about 300 amino acids to about 350 amino acids, about 350 amino acids to about 800 amino acids, about 350 amino acids to about 750 amino acids, about 350 amino acids to about 700 amino acids, about 350 amino acids to about 650 amino acids, about 350 amino acids to about 600 amino acids, about 350 amino acids to about 550 amino acids, about 350 amino acids to about 500 amino acids, about 350 amino acids to about 450 amino acids, about 350 amino acids to about 400 amino acids, about 400 amino acids to about 800 amino acids, about 400 amino acids to about 750 amino acids, about 400 amino acids to about 700 amino acids, about 400 amino acids to about 650 amino acids, about 400 amino acids to about 600 amino acids, about 400 amino acids to about 550 amino acids, about 400 amino acids to about 500 amino acids, about 400 amino acids to about 450 amino acids, about 450 amino acids to about 800 amino acids, about 450 amino acids to about 750 amino acids, about 450 amino acids to about 700 amino acids, about 450 amino acids to about 650 amino acids, about 450 amino acids to about 600 amino acids, about 450 amino acids to about 550 amino acids, about 450 amino acids to about 500 amino acids, about 500 amino acids to about 800 amino acids, about 500 amino acids to about 750 amino acids, about 500 amino acids to about 700 amino acids, about 500 amino acids to about 650 amino acids, about 500 amino acids to about 600 amino acids, about 500 amino acids to about 550 amino acids, about 550 amino acids to about 800 amino acids, about 550 amino acids to about 750 amino acids, about 550 amino acids to about 700 amino acids, about 550 amino acids to about 650 amino acids, about 550 amino acids to about 600 amino acids, about 600 amino acids to about 800 amino acids, about 600 amino acids to about 750 amino acids, about 600 amino acids to about 700 amino acids, about 600 amino acids to about 650 amino acids, about 650 amino acids to about 800 amino acids, about 650 amino acids to about 750 amino acids, about 650 amino acids to about 700 amino acids, about 700 amino acids to about 800 amino acids, about 700 amino acids to about 750 amino acids, or about 750 amino acids to about 800 amino acids. In some embodiments of any of the ACCs described herein, one or more linkers (e.g., flexible linkers) can be introduced into the activatable cytokine construct to provide flexibility at one or more of the junctions between domains, between moieties, between moieties and domains, or at any other junctions where a linker would be beneficial. In some embodiments, where the ACC is provided as a conformationally constrained construct, a flexible linker can be inserted to facilitate formation and maintenance of a structure in the uncleaved activatable cytokine construct. Any of the linkers described herein can provide the desired flexibility to facilitate the inhibition of the binding of a target (e.g., a receptor of a cytokine), or to facilitate cleavage of a CM by a protease. In some embodiments, linkers are included in the ACC that are all or partially flexible, such that the linker can include a flexible linker as well as one or more portions that confer less flexible structure to provide for a desired ACC. Some linkers may include cysteine residues, which may form disulfide bonds and reduce flexibility of the construct. It has been found that reducing the length of the linkers or linking region reduces the activity of the mature cytokine protein in ACCs (see, e.g., Fig. 16 showing data for ACCs without a peptide affinity mask). In most instances, linker length is determined by counting, in a N- to C- direction, the number of amino acids from the N-terminus of the linker adjacent to the C-terminal amino acid of the preceding component, to the C-terminus of the linker adjacent to the N-terminal amino acid of the following component (i.e., where the linker length does not include either the C-terminal amino acid of the preceding component or the N-terminal amino acid of the following component). In embodiments in which a linker is employed at the N-terminus of a DD that comprises an Fc domain, linker length is determined by counting the number of amino acids from the N-terminus of the linker adjacent to the C-terminal amino acid of the preceding component to C-terminus of the linker adjacent to the first cysteine of an Fc hinge region that participates in the disulfide linkage with a second Fc domain (i.e., where the linker length does not include the C-terminal amino acid of the preceding component or the first cysteine of the Fc hinge region). As apparent from the present disclosure and Fig. 17, ACCs of the present disclosure include a stretch of amino acids between the CP and the proximal point of interaction between the dimerization domains. That stretch of amino acids may be referred to as a Linking Region (LR). As used herein, the term “linking region” or “LR” refers to the stretch of amino acid residues between the C-terminus of the cytokine and the amino acid residue that is N-terminally adjacent to the proximal point of interaction between the dimerization domains (i.e., the linking region does not include the C-terminal amino acid of the cytokine or the N-terminal amino acid of the DD that forms the proximal point of interaction to the DD of the corresponding second monomer). For example, when the DDs are a pair of Fc domains, the linking region is the stretch of amino acid residues between the C-terminus of the cytokine and the first N-terminal cysteine residue of the Fc that participates in the disulfide linkage with the second Fc domain (e.g., Cysteine 226 of an IgGl or IgG4 Fc domain, according to EU numbering). When the dimerization domain is not a peptide, then the linking region is the stretch of amino acid residues following the C-terminus of the cytokine until the last amino acid. For example, when the DDs are a biotin-streptavidin pair, the linking region of the biotincontaining monomer is the stretch of amino acid residues between the C-terminus of the cytokine and the biotin molecule, and the linking region of the streptavidin-containing monomer is the stretch of amino acid residues between the C-terminus of the cytokine and the streptavidin molecule. In some embodiments, additional amino acid sequences may be positioned N-terminally or C-terminally to any of the domains of any of the ACCs. Examples include, but are not limited to, targeting moieties (e.g., a ligand for a receptor of a cell present in a target tissue) and serum half-life extending moieties (e.g., polypeptides that bind serum proteins, such as immunoglobulin (e.g., IgG) or serum albumin (e.g., human serum albumin (HSA)). In some embodiments of any of the activatable cytokine constructs described herein, the linker can include a total of about 1 amino acid to about 25 amino acids (e.g., about 1 amino acid to about 24 amino acids, about 1 amino acid to about 22 amino acids, about 1 amino acid to about 20 amino acids, about 1 amino acid to about 18 amino acids, about 1 amino acid to about 16 amino acids, about 1 amino acid to about 15 amino acids, about 1 amino acid to about 14 amino acids, about 1 amino acid to about 12 amino acids, about 1 amino acid to about 10 amino acids, about 1 amino acid to about 8 amino acids, about 1 amino acid to about 6 amino acids, about 1 amino acid to about 5 amino acids, about 1 amino acid to about 4 amino acids, about 1 amino acid to about 3 amino acids, about 1 amino acid to about 2 amino acids, about 2 amino acids to about 25 amino acids, about 2 amino acids to about 24 amino acids, about 2 amino acids to about 22 amino acids, about 2 amino acids to about 20 amino acids, about 2 amino acids to about 18 amino acids, about 2 amino acids to about 16 amino acids, about 2 amino acids to about 15 amino acids, about 2 amino acids to about 14 amino acids, about 2 amino acids to about 12 amino acids, about 2 amino acids to about 10 amino acids, about 2 amino acids to about 8 amino acids, about 2 amino acids to about 6 amino acids, about 2 amino acids to about 5 amino acids, about 2 amino acids to about 4 amino acids, about 2 amino acids to about 3 amino acids, about 4 amino acids to about 25 amino acids, about 4 amino acids to about 24 amino acids, about 4 amino acids to about 22 amino acids, about 4 amino acids to about 20 amino acids, about 4 amino acids to about 18 amino acids, about 4 amino acids to about 16 amino acids, about 4 amino acids to about 15 amino acids, about 4 amino acids to about 14 amino acids, about 4 amino acids to about 12 amino acids, about 4 amino acids to about 10 amino acids, about 4 amino acids to about 8 amino acids, about 4 amino acids to about 6 amino acids, about 4 amino acids to about 5 amino acids, about 5 amino acids to about 25 amino acids, about 5 amino acids to about 24 amino acids, about 5 amino acids to about 22 amino acids, about 5 amino acids to about 20 amino acids, about 5 amino acids to about 18 amino acids, about 5 amino acids to about 16 amino acids, about 5 amino acids to about 15 amino acids, about 5 amino acids to about 14 amino acids, about 5 amino acids to about 12 amino acids, about 5 amino acids to about 10 amino acids, about 5 amino acids to about 8 amino acids, about 5 amino acids to about 6 amino acids, about 6 amino acids to about 25 amino acids, about 6 amino acids to about 24 amino acids, about 6 amino acids to about 22 amino acids, about 6 amino acids to about 20 amino acids, about 6 amino acids to about 18 amino acids, about 6 amino acids to about 16 amino acids, about 6 amino acids to about 15 amino acids, about 6 amino acids to about 14 amino acids, about 6 amino acids to about 12 amino acids, about 6 amino acids to about 10 amino acids, about 6 amino acids to about 8 amino acids, about 8 amino acids to about 25 amino acids, about 8 amino acids to about 24 amino acids, about 8 amino acids to about 22 amino acids, about 8 amino acids to about 20 amino acids, about 8 amino acids to about 18 amino acids, about 8 amino acids to about 16 amino acids, about 8 amino acids to about 15 amino acids, about 8 amino acids to about 14 amino acids, about 8 amino acids to about 12 amino acids, about 8 amino acids to about 10 amino acids, about 10 amino acids to about 25 amino acids, about 10 amino acids to about 24 amino acids, about 10 amino acids to about 22 amino acids, about 10 amino acids to about 20 amino acids, about 10 amino acids to about 18 amino acids, about 10 amino acids to about 16 amino acids, about 10 amino acids to about 15 amino acids, about 10 amino acids to about 14 amino acids, about 10 amino acids to about 12 amino acids, about 12 amino acids to about 25 amino acids, about 12 amino acids to about 24 amino acids, about 12 amino acids to about 22 amino acids, about 12 amino acids to about 20 amino acids, about 12 amino acids to about 18 amino acids, about 12 amino acids to about 16 amino acids, about 12 amino acids to about 15 amino acids, about 12 amino acids to about 14 amino acids, about 14 amino acids to about 25 amino acids, about 14 amino acids to about 24 amino acids, about 14 amino acids to about 22 amino acids, about 14 amino acids to about 20 amino acids, about 14 amino acids to about 18 amino acids, about 14 amino acids to about 16 amino acids, about 14 amino acids to about 15 amino acids, about 15 amino acids to about 25 amino acids, about 15 amino acids to about 24 amino acids, about 15 amino acids to about 22 amino acids, about 15 amino acids to about 20 amino acids, about 15 amino acids to about 18 amino acids, about 15 amino acids to about 16 amino acids, about 16 amino acids to about 25 amino acids, about 16 amino acids to about 24 amino acids, about 16 amino acids to about 22 amino acids, about 16 amino acids to about 20 amino acids, about 16 amino acids to about 18 amino acids, about 18 amino acids to about 25 amino acids, about 18 amino acids to about 24 amino acids, about 18 amino acids to about 22 amino acids, about 18 amino acids to about 20 amino acids, about 20 amino acids to about 25 amino acids, about 20 amino acids to about 24 amino acids, about 20 amino acids to about 22 amino acids, about 22 amino acid to about 25 amino acids, about 22 amino acid to about 24 amino acids, or about 24 amino acid to about 25 amino acids). In some embodiments of any of the ACCs described herein, the linker includes a total of about 1 amino acid, about 2 amino acids, about 3 amino acids, about 4 amino acids, about 5 amino acids, about 6 amino acids, about 7 amino acids, about 8 amino acids, about 9 amino acids, about 10 amino acids, about 11 amino acids, about 12 amino acids, about 13 amino acids, about 14 amino acids, about 15 amino acids, about 16 amino acids, about 17 amino acids, about 18 amino acids, about 19 amino acids, about 20 amino acids, about 21 amino acids, about 22 amino acids, about 23 amino acids, about 24 amino acids, or about 25 amino acids. Surprisingly, the applicant has discovered that ACCs that do not comprise any linkers between the CP and the DD exhibit the most significant reduction in cytokine activity relative to the wildtype mature cytokine, compared to ACCs that include linkers or additional sequences in the linking region. See, e.g., Fig. 16 (showing data for ACCs without a peptide affinity mask). Further, a configuration in which there are no linkers between the CP and the DD still allows effective cleavage of a CM positioned between the CP and the DD. See e.g., Figs. 7A, 7B, 10A and 10B. Thus, in some embodiments, the ACC does not comprise any linkers between the CP and the DD, and the CM between the CP and the DD comprises not more than 10, 9, 8, 7, 6, 5, 4, or 3 amino acids. In some embodiments the total number of amino acids in the LR comprises not more than 25 amino acids, e.g., not more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, or 3 amino acids, or 3 to 10 amino acids or 5 to 15 amino acids, or 7 to 12 amino acids, or any range or specific number of amino acids selected from the range encompassed by 3 to 25 amino acids. In some embodiments of any of the ACCs described herein, a linker can be rich in glycine (Gly or G) residues. In some embodiments, the linker can be rich in serine (Ser or S) residues. In some embodiments, the linker can be rich in glycine and serine residues. In some embodiments, the linker has one or more glycine-serine residue pairs (GS) (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more GS pairs). In some embodiments, the linker has one or more Gly-Gly-Gly-Ser (GGGS) sequences (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more GGGS sequences). In some embodiments, the linker has one or more Gly-Gly-Gly-Gly-Ser (GGGGS) sequences (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more GGGGS sequences). In some embodiments, the linker has one or more Gly-Gly-Ser-Gly (GGSG) sequences (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more GGSG sequences). In some embodiments of any of the ACCs described herein, a linker includes any one of or a combination of one or more of: GSSGGSGGSGG (SEQ ID NO: 210), GGGS (SEQ ID NO: 2), GGGSGGGS (SEQ ID NO: 211), GGGSGGGSGGGS (SEQ ID NO: 212), GGGGSGGGGSGGGGS (SEQ ID NO: 213), GGGGSGGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214), GGGGSGGGGS (SEQ ID NO: 215), GGGGS (SEQ ID NO: 216), GS, GGGGSGS (SEQ ID NO: 217), GGGGSGGGGSGGGGSGS (SEQ ID NO: 218), GGSLDPKGGGGS (SEQ ID NO: 219), PKSCDKTHTCPPCPAPELLG (SEQ ID NO: 220), SKYGPPCPPCPAPEFLG (SEQ ID NO: 221), GKSSGSGSESKS (SEQ ID NO: 222), GSTSGSGKSSEGKG (SEQ ID NO: 223), GSTSGSGKSSEGSGSTKG (SEQ ID NO: 224), and GSTSGSGKPGSGEGSTKG (SEQ ID NO: 225). Non-limiting examples of linkers can include a sequence that is at least 70% identical (e.g., at least 72%, at least 74%, at least 75%, at least 76%, at least 78%, at least 80%, at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to GGGS (SEQ ID NO: 2), GSSGGSGGSGG (SEQ ID NO: 210), GGGGSGGGGSGGGGS (SEQ ID NO: 213), GGGGSGS (SEQ ID NO: 217), GGGGSGGGGSGGGGSGS (SEQ ID NO: 218), GGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214), GGSLDPKGGGGS (SEQ ID NO: 215), and GSTSGSGKPGSSEGST (SEQ ID NO: 226). In some embodiments, the linker includes a sequence selected from the group of: GGSLDPKGGGGS (SEQ ID NO: 219), GGGGSGGGGSGGGGSGS (SEQ ID NO: 218), GGGGSGS (SEQ ID NO: 217), GS, (GS)n, (GGS)n, (GSGGS)n (SEQ ID NO: 227) and (GGGS)n (SEQ ID NO: 228), GGSG (SEQ ID NO: 229), GGSGG (SEQ ID NO: 230), GSGSG (SEQ ID NO: 231), GSGGG (SEQ ID NO: 232), GGGSG (SEQ ID NO: 233), GSSSG (SEQ ID NO: 234), GGGGSGGGGSGGGGS (SEQ ID NO: 213), GGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214), GSTSGSGKPGSSEGST (SEQ ID NO: 226), (GGGGS)n (SEQ ID NO: 216), wherein n is an integer of at least one. In some embodiments, the linker includes a sequence selected from the group consisting of: GGSLDPKGGGGS (SEQ ID NO: 219), GGGGSGGGGSGGGGSGS (SEQ ID NO: 218), GGGGSGS (SEQ ID NO: 217), and GS. In some embodiments of any of the ACCs described herein, the linker includes a sequence selected from the group of: GGGGSGGGGSGGGGS (SEQ ID NO: 213), GGGGSGGGGSGGGGSGGGGS (SEQ ID NO: 214), and GSTSGSGKPGSSEGST (SEQ ID NO: 226). In some embodiments of any of the activatable cytokine constructs described herein, the linker includes a sequence selected from the group of: GGGGSGGGGSGGGGS (SEQ ID NO: 213) or GGGGS (SEQ ID NO: 216). In some embodiments, the linker comprises a sequence of GGGS (SEQ ID NO: 2). Additional examples of linkers include those listed in Table 23. In some embodiments, an ACC can include one, two, three, four, five, six, seven, eight, nine, or ten linker sequence(s) (e.g., the same or different linker sequences of any of the exemplary linker sequences described herein or known in the art). In some embodiments, a linker comprises sulfo-SIAB, SMPB, and sulfo-SMPB, wherein the linkers react with primary amines sulfhydryls. In some embodiments of any of the ACCs described herein, the ACC is characterized by a reduction in at least one activity of the CPI and / or CP2 as compared to a control level of the at least one activity of the CPI and / or CP2. In some embodiments, a control level can be the level of the activity for a recombinant CPI and / or CP2 (e.g., a commercially available recombinant CPI and / or CP2, a recombinant wildtype CPI and / or CP2, and the like). In some embodiments, a control level can be the level of the activity of a cleaved (activated) form of the ACC. In certain embodiments, a control level can be the level of the activity of a pegylated CPI and / or CP2. In some embodiments, the at least one activity is the binding affinity of the CPI and / or the CP2 for its cognate receptor as determined using surface plasmon resonance (e.g., performed in phosphate buffered saline at 25 degrees Celsius). In certain embodiments, the at least one activity is the level of proliferation of lymphoma cells. In other embodiments, the at least one activity is the level of JAK / STAT / ISGF3 pathway activation in a lymphoma cell. In some embodiments, the at least one activity is a level of SEAP production in a lymphoma cell. In a further embodiment, the at least one activity of the CPI and / or CP2 is level of cytokine-stimulated gene induction using, for example RNAseq methods (see, e.g., Zimmerer et al., Clin. Cancer Res. 14(18):5900-5906, 2008; Hilkens et al., J. Immunol. 171:5255-5263, 2003). In some embodiments, the ACC is characterized by at least a 2-fold reduction in at least one CPI and / or CP2 activity as compared to the control level of the at least one CPI and / or CP2 activity. In some embodiments, the ACC is characterized by at least a 5fold reduction in at least one activity of the CPI and / or CP2 as compared to the control level of the at least one activity of the CPI and / or CP2. In some embodiments, the ACC is characterized by at least a 10-fold reduction in at least one activity of the CPI and / or CP2 as compared to the control level of the at least one activity of the CPI and / or CP2. In some embodiments, the ACC is characterized by at least a 20-fold reduction in at least one activity of the CPI and / or CP2 as compared to the control level of the at least one activity of the CPI and / or CP2. In some embodiments, the ACC is characterized by at least a 30-fold, 40-fold, 50-fold, 60-fold, 70-fold, 80-fold, 90-fold, 100-fold, 500-fold, 1000-fold, 2000-fold, 3000-fold, 5000-fold or 5,000-fold reduction in at least one activity of the CPI and / or CP2 as compared to the control level of the at least one activity of the CPI and / or CP2. In some embodiments, ACC is characterized by at least a 1- to 20-fold reduction, a 200- to 2000-fold reduction, a 300- to 2000-fold reduction, a 400- to 2000fold reduction, a 500- to 2000-fold reduction, a 1000- to 2000-fold reduction, a 1500- to 2000-fold reduction, a 100- to 1500-fold reduction, a 200- to 1500-fold reduction, a 300-to 1500-fold reduction, a 400- to 1500-fold reduction, a 500- to 1500-fold reduction, a 1000- to 1500-fold reduction, a 100- to 1000-fold reduction, a 200- to 1000-fold reduction, a 300- to 1000-fold reduction, a 400- to 1000-fold reduction, a 500- to 1000fold reduction, a 1000- to 5000-fold reduction, a 2000- to 5000-fold reduction, a 3000- to 5000-fold reduction, a 4000- to 5000-fold reduction, a 1000- to 4000-fold reduction, a 2000- to 4000-fold reduction, a 3000- to 4000-fold reduction, a 1000- to 3000-fold reduction, a 2000- to 3000-fold reduction, or a 1000- to 2000-fold reduction in at least one activity of the CPI and / or CP2 as compared to the control level of the at least one activity of the CPI and / or CP2. In some embodiments, the control level of the at least one activity of the CPI and / or CP2 is the activity of the CPI and / or CP2 released from the ACC following cleavage of the CMs by protease(s) (the “cleavage product”). In some embodiments, the control level of the at least one activity of the CPI and / or CP2 is the activity of a corresponding wildtype mature cytokine (e.g., recombinant wildtype mature cytokine). In some embodiments, incubation of the ACC with the protease yields an activated cytokine product(s), where one or more activities of CPI and / or CP2 of the activated cytokine product(s) is greater than the one or more activities of CPI and / or CP2 of the intact ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 1-fold greater than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 2-fold greater than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 5-fold greater than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 10-fold greater than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 20-fold greater than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, one or more activities of CPI and / or CP2 of the activated cytokine product(s) is at least 1- to 20-fold greater, a 200- to 2000-fold greater, a 300- to 2000-fold greater, a 400- to 2000-fold greater, a 500- to 2000-fold greater, a 1000- to 2000-fold greater, a 1500- to 2000-fold greater, a 100- to 1500-fold greater, a 200- to 1500-fold greater, a 300- to 1500-fold greater, a 400- to 1500-fold greater, a 500-to 1500-fold greater, a 1000- to 1500-fold greater, a 100- to 1000-fold greater, a 200- to 1000-fold greater, a 300- to 1000-fold greater, a 400- to 1000-fold greater, a 500- to 1000-fold greater, a 1000- to 5000-fold greater, a 2000- to 5000-fold greater, a 3000- to 5000-fold greater, a 4000- to 5000-fold greater, a 1000- to 4000-fold greater, a 2000- to 4000-fold greater, a 3000- to 4000-fold greater, a 1000- to 3000-fold greater, a 2000- to 3000-fold greater, or a 1000- to 2000-fold than the one or more activities of CPI and / or CP2 of the ACC. In some embodiments, an ACC can include a sequence that is at least 80% (e.g., at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 96%, at least 98%, at least 99%, or 100%) identical to SEQ ID NO: 290 or 291. In some embodiments, an ACC can be encoded by a nucleic acid including a sequence that is at least 80% (e.g., at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 96%, at least 98%, at least 99%, or 100%) identical to a nucleic acid encoding SEQ ID NOs: 290 or 291. In some aspects, an ACC may include such sequences but either without the signal sequences of those sequences. Signal sequences are not particularly limited. Some non-limiting examples of signal sequences include, e.g., SEQ ID NO: 470 and corresponding residues and nucleotides in the other sequences, or substituted with a signal sequence from another species or cell line. Other examples of signal sequences include MRAWIFFLLCLAGRALA (SEQ ID NO: 468) and MALTFALLVALLVLSCKSSCSVG (SEQ ID NO: 469). Various exemplary aspects of these ACCs and activatable antibodies are described below and can be used in any combination in the methods provided herein without limitation. Exemplary aspects of the ACCs and activatable antibodies and methods of making ACCs and activatable antibodies are described below. In some embodiments, the CM is selected for use with a specific protease. The protease may be one produced by a tumor cell (e.g., the tumor cell may express greater amounts of the protease than healthy tissues). In some embodiments, the CM is a substrate for at least one protease selected from the group of an ADAM 17, a BMP-1, a cysteine protease such as a cathepsin, a HtrAl, a legumain, a matriptase (MT-SP1), a matrix metalloprotease (MMP), a neutrophil elastase, a TMPRSS, such as TMPRSS3 or TMPRSS4, a thrombin, and a u-type plasminogen activator (uPA, also referred to as urokinase). In some embodiments, a CM is a substrate for at least one matrix metalloprotease (MMP). Examples of MMPs include MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP11, MMP12, MMP13, MMP14, MMP15, MMP16, MMP17, MMP19, MMP20, MMP23, MMP24, MMP26, and MMP27. In some embodiments, the CM is a substrate for MMP9, MMP14, MMP1, MMP3, MMP13, MMP17, MMP11, and MMP19. In some embodiments, the CM is a substrate for MMP7. In some embodiments, the CM is a substrate for MMP9. In some embodiments, the CM is a substrate for MMP14. In some embodiments, the CM is a substrate for two or more MMPs. In some embodiments, the CM is a substrate for at least MMP9 and MMP14. In some embodiments, the CM includes two or more substrates for the same MMP. In some embodiments, the CM includes at least two or more MMP9 substrates. In some embodiments, the CM includes at least two or more MMP14 substrates. In some embodiments, a CM is a substrate for an MMP and includes the sequence ISSGLLSS (SEQ ID NO: 19); QNQALRMA (SEQ ID NO: 16); AQNLLGMV (SEQ ID NO: 15); STFPFGMF (SEQ ID NO: 18); PVGYTSSL (SEQ ID NO: 74); DWLYWPGI (SEQ ID NO: 75); MIAPVAYR (SEQ ID NO: 42); RPSPMWAY (SEQ ID NO: 43); WATPRPMR (SEQ ID NO: 44); FRLLDWQW (SEQ ID NO: 45); LKAAPRWA (SEQ ID NO: 76); GPSHLVLT (SEQ ID NO: 77); LPGGLSPW (SEQ ID NO: 78); MGLFSEAG (SEQ ID NO: 79); SPLPLRVP (SEQ ID NO: 80); RMHLRSLG (SEQ ID NO: 81); LAAPLGLL (SEQ ID NO: 17); AVGLLAPP (SEQ ID NO: 14); LLAPSHRA (SEQ ID NO: 82); PAGLWLDP (SEQ ID NO: 20); and / or ISSGLSS (SEQ ID NO: 73). In some embodiments, a CM is a substrate for thrombin. In some embodiments, the CM is a substrate for thrombin and includes the sequence GPRSFGL (SEQ ID NO: 83) or GPRSFG (SEQ ID NO: 84). In some embodiments, a CM includes an amino acid sequence selected from the group of NTLSGRSENHSG (SEQ ID NO: 9); NTLSGRSGNHGS (SEQ ID NO: 10); TSTSGRSANPRG (SEQ ID NO: 11); TSGRSANP (SEQ ID NO: 12); VAGRSMRP (SEQ ID NO: 21); VVPEGRRS (SEQ ID NO: 22); ILPRSPAF (SEQ ID NO: 23); MVLGRSLL (SEQ ID NO: 24); QGRAITFI (SEQ ID NO: 25); SPRSIMLA (SEQ ID NO: 26); and SMLRSMPL (SEQ ID NO: 27). In some embodiments, a CM is a substrate for a neutrophil elastase. In some embodiments, a CM is a substrate for a serine protease. In some embodiments, a CM is a substrate for uPA. In some embodiments, a CM is a substrate for legumain. In some embodiments, the CM is a substrate for matriptase. In some embodiments, the CM is a substrate for a cysteine protease. In some embodiments, the CM is a substrate for a cysteine protease, such as a cathepsin. In some embodiments, a CM includes a sequence of ISSGLLSGRSDNH (SEQ ID NO: 28); ISSGLLSSGGSGGSLSGRSDNH (SEQ ID NO: 30); AVGLLAPPGGTSTSGRSANPRG (SEQ ID NO: 275); TSTSGRSANPRGGGAVGLLAPP (SEQ ID NO: 276); VHMPLGFLGPGGTSTSGRSANPRG (SEQ ID NO: 277); TSTSGRSANPRGGGVHMPLGFLGP (SEQ ID NO: 278); AVGLLAPPGGLSGRSDNH (SEQ ID NO: 29); LSGRSDNHGGAVGLLAPP (SEQ ID NO: 70); VHMPLGFLGPGGLSGRSDNH (SEQ ID NO: 266); LSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 267); LSGRSDNHGGSGGSISSGLLSS (SEQ ID NO: 268); LSGRSGNHGGSGGSISSGLLSS (SEQ ID NO: 279); ISSGLLSSGGSGGSLSGRSGNH (SEQ ID NO: 269); LSGRSDNHGGSGGSQNQALRMA(SEQ ID NO: 270); QNQALRMAGGSGGSLSGRSDNH (SEQ ID NO: 271); LSGRSGNHGGSGGSQNQALRMA (SEQ ID NO: 272); QNQALRMAGGSGGSLSGRSGNH (SEQ ID NO: 273), and / or ISSGLLSGRSGNH (SEQ ID NO: 274). In some embodiments, a CM comprises a sequence selected from the group consisting of SEQ ID NO: 5 through SEQ ID NO: 100. In some embodiments, the CM comprises a sequence selected from the group of: ISSGLLSGRSDNH (SEQ ID NO: 28), LSGRSDDH (SEQ ID NO: 33), ISSGLLSGRSDQH (SEQ ID NO: 54), SGRSDNI (SEQ ID NO: 100), and ISSGLLSGRSDNI (SEQ ID NO: 68). Any one or combination of the CMs disclosed herein may be used in the context of any of the ACCs and activatable antibodies of the present disclosure. In some aspects, the ACC includes a first monomer comprising a CPI selected from SEQ ID Nos: 1 and 101-209, a CM1 selected from SEQ ID Nos: 5-100 and 237281, a PM1 selected from SEQ ID Nos: 297, 298, 292, and 299-446, a CM3 selected from SEQ ID Nos: 5-100 and 237-281, and a DD1 dimerized with a second monomer comprising a CP2 selected from SEQ ID Nos: 1 and 101-209, a CM2 selected from SEQ ID Nos: 5-100 and 237-281, a PM2 selected from SEQ ID Nos: 297, 298, 292, and 299446, a CM3 selected from SEQ ID Nos: 5-100 and 237-281and a DD2. In some aspects, the ACC may include, between CPI and CM1, between CPI and PM1, between CPI and CM3, between PM1 and CM3, and / or between CM1 and DD1, a linker selected from SEQ ID Nos: 2 and 210-263, and between CP2 and CM2, between CP2 and PM2, between CP2 and CM4, between PM2 and CM4, and / or between CM2 and DD2, a linker selected from SEQ ID Nos: 2 and 210-2236. In some aspects, the PM1 is selected for use with the CPI in accordance with Table 24, and the PM2 is selected for use with the CP2, in accordance with Table 24. In some embodiments, the ACC includes a DD1 and / or a DD2 that has an amino acid sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to SEQ ID NO: 3 or SEQ ID NO: 4. In some embodiments, the ACC includes a DD1 that has an amino acid sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to SEQ ID NO: 287 or SEQ ID NO: 288. In some embodiments, the ACC includes a DD2 that has an amino acid sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 85%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to SEQ ID NO: 287 or SEQ ID NO: 288. One or both monomers of the ACC herein may comprise one or more peptide masks (PMs), which can interfere with the binding of the CP to its binding partner (e.g., receptors). In some embodiments, when an ACC is not activated, the PM in the ACC prevents the CP from target binding; but when the ACC is activated, the PM does not substantially or significantly interfere with the CP’s binding to its binding partner. In some embodiments, a PM is coupled to a CP by a CM and optionally one or more linkers described herein. In some embodiments, a PM may interact with the CP, thus reducing or inhibiting the interaction between the CP and its binding partner. In some embodiments, the PM may not specifically bind to the CP, but rather interfere with CP’s binding to its binding partner through non-specific interactions such as steric hindrance. For example, the PM may be positioned in the uncleaved ACC such that the tertiary or quaternary structure of the ACC allows the PM to mask the CP through charge-based interaction, thereby holding the PM in place to interfere with binding partner access to the CP. The structural properties of the PM may be selected according to factors such as the minimum amino acid sequence required for interference with protein binding to target, the target protein-protein binding pair of interest, the size of the cytokine, the presence or absence of linkers, and the like. The PMs may be identified and / or further optimized through a screening procedure from a library of candidate ACC having variable PMs. For example, a CP and a CM can be selected to provide for a desired enzyme / target combination, and the amino acid sequence of the PM can be identified by the screening procedure described below to identify a PM that provides for a switchable phenotype. For example, a random peptide library (e.g., of peptides comprising about 2 to about 40 amino acids or more) may be used in the screening methods disclosed herein to identify a suitable PM. In specific embodiments, PMs with specific binding affinity for a CP can be identified through a screening procedure that includes providing a library of peptide scaffolds consisting of candidate PMs wherein each scaffold is made up of a transmembrane protein and the candidate PM. The library may then be contacted with an entire or portion of a protein such as a full length protein, a naturally occurring protein fragment, or a non-naturally occurring fragment containing a protein (also capable of binding the binding partner of interest), and identifying one or more candidate PMs having detectably bound protein. The screening may be performed by one more rounds of magnetic-activated sorting (MACS) or fluorescence-activated sorting (FACS), as well as determination of the binding affinity of PM towards the CP and subsequent determination of the masking efficiency, e.g., as described in US20200308243A1, which is incorporated herein by reference in its entirety. In some embodiments, the PM is unique for the coupled CP. Examples of PMs include PMs that were specifically screened to bind a binding domain of the cytokine or protein fragment (e.g., affinity peptide masks). Methods for screening PMs to obtain PMs unique for the cytokine and those that specifically and / or selectively bind a binding domain of a binding partner / target are provided herein and can include protein display methods. Table 7 discloses exemplary PMs suitable for use with various exemplary CPs. In some embodiments, when a CP is coupled to a PM and in the presence of a natural binding partner of the CP, there is no binding or substantially no binding of the CP to the binding partner, or no more than 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 50% binding of the CP to its binding partner, as compared to the binding of the CP not coupled to a PM, for at least 2, 4, 6, 8, 12, 28, 24, 30, 36, 48, 60, 72, 84, 96 hours, or 5, 10, 15, 30, 45, 60, 90, 120, 150, 180 days, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 months or greater when measured in a masking efficiency assay, e.g., as described in Example 1. The PMs contemplated by this disclosure may range from 1-50 amino acids (e.g., at least 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 30, or 40 amino acids, or no greater than 40, 30, 20, 15, 12, 10, 9, 8, 7, 6, 5, 4, or 3 amino acids). In some examples, the PMs may be from 8 to 15 amino acids in length. The PMs may contain genetically encoded or genetically non-encoded amino acids. Examples of genetically non-encoded amino acids are but not limited to D-amino acids, P-amino acids, and y-amino acids. In specific embodiments, the PMs contain no more than 50%, 40%, 30%, 20%, 15%, 10%, 5% or 1% of genetically non-encoded amino acids. The binding affinity of the cytokine towards the target or binding partner when coupled to a PM may be at least 5, 10, 25, 50, 100, 250, 500, 1,000, 2,500, 5,000, 10,000, 50,000, 100,000, 500,000, 1,000,000, 5,000,000, 10,000,000, 50,000,000 or greater times lower than the binding affinity of the cytokine towards its binding partner when not coupled to a PM, or between 5-10, 10-100, 10-1,000, 10-10,000, 10-100,000, 101,000,000, 10-10,000,000, 100-1,000, 100-10,000, 100-100,000, 100-1,000,000, 10010,000,000, 1,000-10,000, 1,000-100,000, 1,000-1,000,000, 1000-10,000,000, 10,000100,000, 10,000-1,000,000, 10,000-10,000,000, 100,000-1,000,000, or 100,00010,000,000 times lower than the binding affinity of the cytokine towards its binding partner when not coupled to a PM. When the cytokine is coupled to a PM and is in the presence of the binding partner, specific binding of the cytokine to its binding partner may be be reduced or inhibited, as compared to the specific binding of the cytokine not coupled to a PM to its binding partner. When compared to the binding of the cytokine not coupled to a PM to its binding partner, the cytokine's ability to bind the binding partner when coupled to a PM can be reduced by at least 50%, 60%, 70%, 80%, 90%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% and even 100% for at least 2, 4, 6, 8, 12, 28, 24, 30, 36, 48, 60, 72, 84, 96, hours, or 5, 10, 15, 30, 45, 60, 90, 120, 150, 180 days, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 months or greater when measured in vivo or in a masking efficiency assay, e.g., as shown in Example 1, an in vitro immunoabsorbant assay, e.g., as described in US20200308243A1. The Kd of the PM towards the cytokine may be generally greater than the Kd of the cytokine towards the cytokine’s binding partner. The Kd of the PM towards the cytokine may be at least 5, 10, 25, 50, 100, 250, 500, 1,000, 2,500, 5,000, 10,000, 100,000, 1,000,000 or even 10,000,000 times greater than the Kd of the cytokine towards its binding partner. Alternatively, the binding affinity of the PM towards the cytokine may be generally lower than the binding affinity of the cytokine towards the cytokine’s binding partner. The binding affinity of PM towards the cytokine may be at least 5, 10, 25, 50, 100, 250, 500, 1,000, 2,500, 5,000, 10,000, 100,000, 1,000,000 or 10,000,000 times lower than the binding affinity of the cytokine towards its binding partner. In some embodiments, the PM comprises at least partial or complete amino acid sequence of a naturally occurring binding partner of the CP (e.g., a receptor of the CP). The PM may be a fragment of a naturally occurring binding partner. The fragment may retain no more than 95%, 90%, 80%, 75%, 70%, 60%, 50%, 40%, 30%, 25%, or 20% nucleic acid or amino acid sequence homology to the naturally occurring binding partner. In some embodiments, the PM comprises an amino acid sequence that is not naturally occurring or does not contain the amino acid sequence of a naturally occurring binding partner or target protein. In certain embodiments the PM is not a natural binding partner of the CP. The PM may be a modified binding partner for the CP which contains amino acid changes that at least slightly decrease affinity and / or avidity of binding to the CP. In some embodiments the PM contains no or substantially no nucleic acid or amino acid homology to the CP's natural binding partner. In other embodiments the PM is no more than 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80% similar to the natural binding partner of the CP. In some embodiments, the PM comprises an amino acid sequence that is at least 80% identical (e.g., at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical) to a sequence selected from SEQ ID Nos: 297, 298, 292, and 299-446. An exemplary PM for use with a CP that is an interferon, preferably an IFN-alpha, can contain the consensus sequence: TDVDYYREWXXXXXXXX (SEQ ID No: 329), where X is any amino acid. In some embodiments, an ACC may comprise a pair of PM1 and CPI or a pair of PM2 and CP2 listed in Table 7, which contains example PMs for use with specific exemplary cytokines. In some examples, the PM1 comprises a sequence selected from SEQ ID NOs: 297, 298, 292, and 299-336, and the CPI is an interferon; the PM1 comprises a sequence selected from SEQ ID NOs: 297, 298, 292, and 299-332, and the CPI is an interferon alpha; the PM1 comprises a sequence selected from SEQ ID NOs: 299-328, and 330-332, and the CPI is an interferon beta; the PM1 comprises a sequence selected from SEQ ID NOs: 299-328, and 333-336, and the CPI is an interferon gamma; the PM1 comprises a sequence selected from SEQ ID NOs: 337-341, and the CPI is an IL-12; the PM1 comprises a sequence selected from SEQ ID NOs: 342-349, 436-444, 478, and the CPI is an IL-15; the PM1 comprises a sequence selected from SEQ ID NOs: 350-435, 436-445, and the CPI is an IL-2; or the PM1 comprises a sequence selected from SEQ ID NOs: 445 and 446, and the CPI is an IL-21. In some examples, the PM2 comprises a sequence selected from SEQ ID NOs: 297, 298, 292, and 299-336, and the CP2 is an interferon; the PM2 comprises a sequence selected from SEQ ID NOs: 297, 298, 292, and 299-332, and the CP2 is an interferon alpha; the PM2 comprises a sequence selected from SEQ ID NOs: 299-328, and 330-332, and the CP2 is an interferon beta; the PM2 comprises a sequence selected from SEQ ID NOs: 299-328, and 333-336, and the CP2 is an interferon gamma; the PM2 comprises a sequence selected from SEQ ID NOs: 337-341, and the CP2 is an IL-12; the PM2 comprises a sequence selected from SEQ ID NOs: 342-349, 436-444, 478, and the CP2 is an IL-15; the PM2 comprises a sequence selected from SEQ ID NOs: 350-435, 436-445, and the CP2 is an IL-2; or the PM2 comprises a sequence selected from SEQ ID NOs: 445 and 446, and the CP2 is an IL-21. In some embodiments, the PM may comprise an inactive cytokine. For example, the inactive cytokine may interact with the CP component in the ACC and interfere the interaction between the CP and its binding partner. In one example, the inactive cytokine may comprise a mutation, e.g., an IFN alpha-2b with L130P mutation (SEQ ID Nos: 297 and 298). In another example, the inactive cytokine may be a truncation of a wild type cytokine, e.g., IFN alpha-2b with amino acids 1-150. In some embodiments, once uncoupled from the cytokine and in a free state, the PM may have a biological activity or a therapeutic effect, such as binding capability. For example, the free peptide can bind with the same or a different binding partner. In certain embodiments the free PM (uncoupled PM) can exert a therapeutic effect, providing a secondary function to the compositions disclosed herein. In some embodiments, once uncoupled from the cytokine and in a free state, the PM may advantageously not exhibit biological activity. For example, in some embodiments the PM in a free state does not elicit an immune response in the subject. Conjugation to Agents This disclosure also provides methods and materials for including additional elements in any of the ACCs and antibodies described herein including, for example, a targeting moiety to facilitate delivery to a cell or tissue of interest, an agent (e.g., a therapeutic agent, an antineoplastic agent), a toxin, or a fragment thereof. Any of the following disclosures for conjugation of agents to ACCs also apply equally to and should be construed to support conjugation of agents to the antibodies of the present disclosure. In some embodiments of any of the ACCs described herein, the ACC can be conjugated to a cytotoxic agent, including, without limitation, a toxin (e.g., an enzymatically active toxin of bacterial, fungal, plant, or animal origin, or fragments thereof) or a radioactive isotope. In some embodiments of any of the ACCs described herein, the activatable cytokine construct can be conjugated to a cytotoxic agent including, without limitation, a toxin (e.g., an enzymatically active toxin of bacterial, fungal, plant, or animal origin, or fragments thereof), or a radioactive isotope. Non-limiting exemplary cytotoxic agents that can be conjugated to any of the ACCs described herein include: dolastatins and derivatives thereof (e.g., auristatin E, AFP, monomethyl auristatin D (MMAD), monomethyl auristatin F (MMAF), monomethyl auristatin E (MMAE), desmethyl auristatin E (DMAE), auristatin F, desmethyl auristatin F (DMAF), dolastatin 16 (DmJ), dolastatin 16 (Dpv), auristatin derivatives (e.g., auristatin tyramine, auristatin quinolone), maytansinoids (e.g., DM-1, DM-4), maytansinoid derivatives, duocarmycin, alpha-amanitin, turbostatin, phenstatin, hydroxyphenstatin, spongistatin 5, spongistatin 7, halistatin 1, halistatin 2, halistatin 3, halocomstatin, pyrrolobenzimidazoles (PBI), cibrostatin6, doxaliform, cemadotin analogue (CemCH2-SH), Pseudomonas toxin A (PES8) variant, Pseudomonase toxin A (ZZ-PE38) variant, ZJ-101, anthracycline, doxorubicin, daunorubicin, bryostatin, camptothecin, 7-substituted campothecin, 10, 11-difluoromethylenedioxycamptothecin, combretastatins, debromoaplysiatoxin, KahaMide-F, discodermolide, and Ecteinascidins. Non-limiting exemplary enzymatically active toxins that can be conjugated to any of the ACCs described herein include: diphtheria toxin, exotoxin A chain from Pseudomonas aeruginosa, ricin A chain, abrin A chain, modeccin A chain, alpha-sarcin, Aleuriies fordii proteins, dianfhin proteins, Phytoiaca Americana proteins (e.g., PAPI, PAPII, and PAP-8), momordica charantia inhibitor, curcin, crotirs, sapaonaria officinalis inhibitor, geionin, mitogeliin, restrictocin, phenomycin, neomycin, and tricothecenes. Non-limiting exemplary anti-neoplastics that can be conjugated to any of the ACCs described herein include: adriamycin, cerubidine, bleomycin, alkeran, velban, oncovin, fluorouracil, methotrexate, thiotepa, bisantrene, novantrone, thioguanine, procarabizine, and cytarabine. Non-limiting exemplary antivirals that can be conjugated to any of the ACCs described herein include: acyclovir, vira A, and Symmetrel. Non-limiting exemplary antifungals that can be conjugated to any of the ACCs described herein include: nystatin. Non-limiting exemplary conjugatable detection reagents that can be conjugated to any of the ACCs described herein include: fluorescein and derivatives thereof, fluorescein isothiocyanate (FITC). Non-limiting exemplary antibacterials that can be conjugated to any of the activatable cytokine constructs described herein include: aminoglycosides, streptomycin, neomycin, kanamycin, amikacin, gentamicin, and tobramycin. Non-limiting exemplary 3beta,16beta,17alpha-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-beta-D-xylopyranosyl)-(l— >3)-(2-O-acetyl-alpha-L-arabinopyranoside) (OSW-1) that can be conjugated to any of the activatable cytokine constructs described herein include: s-nitrobenzyloxycarbonyl derivatives of 06-benzylguanine, toposisomerase inhibitors, hemiasterlin, cephalotaxine, homoharringionine, pyrrol obenzodiazepine dimers (PBDs), functionalized pyrrolobenzodiazepenes, calcicheamicins, podophyiitoxins, taxanes, and vinca alkoids. Non-limiting exemplary radiopharmaceuticals that can be conjugated to any of the activatable cytokine constructs described herein include: 123I , 89Zr, 1251,131I, "mTc, 2O1T1, 62Cu, 18F, 68Ga,13 N, 150, 38K, 82Rb, mIn, 133Xe, UC, and "mTc (Technetium). Non-limiting exemplary heavy metals that can be conjugated to any of the ACCs described herein include: barium, gold, and platinum. Non-limiting exemplary anti-mycoplasmals that can be conjugated to any of the ACCs described herein include: tylosine, spectinomycin, streptomycin B, ampicillin, sulfanilamide, polymyxin, and chloramphenicol. Those of ordinary skill in the art will recognize that a large variety of possible moieties can be conjugated to any of the activatable cytokine constructs described herein. Conjugation can include any chemical reaction that will bind the two molecules so long as the ACC and the other moiety retain their respective activities. Conjugation can include many chemical mechanisms, e.g., covalent binding, affinity binding, intercalation, coordinate binding, and complexation. In some embodiments, the preferred binding is covalent binding. Covalent binding can be achieved either by direct condensation of existing side chains or by the incorporation of external bridging molecules. Many bivalent or polyvalent linking agents are useful in conjugating any of the activatable cytokine constructs described herein. For example, conjugation can include organic compounds, such as thioesters, carbodiimides, succinimide esters, glutaraldehyde, diazobenzenes, and hexamethylene diamines. In some embodiments, the activatable cytokine construct can include, or otherwise introduce, one or more nonnatural amino acid residues to provide suitable sites for conjugation. In some embodiments of any of the ACCs described herein, an agent and / or conjugate is attached by disulfide bonds (e.g., disulfide bonds on a cysteine molecule) to the antigen-binding domain. Since many cancers naturally release high levels of glutathione, a reducing agent, glutathione present in the cancerous tissue microenvironment can reduce the disulfide bonds, and subsequently release the agent and / or the conjugate at the site of delivery. In some embodiments of any of the ACCs described herein, when the conjugate binds to its target in the presence of complement within the target site (e.g., diseased tissue (e.g., cancerous tissue)), the amide or ester bond attaching the conjugate and / or agent to the linker is cleaved, resulting in the release of the conjugate and / or agent in its active form. These conjugates and / or agents when administered to a subject, will accomplish delivery and release of the conjugate and / or the agent at the target site (e.g., diseased tissue (e.g., cancerous tissue)). These conjugates and / or agents are particularly effective for the in vivo delivery of any of the conjugates and / or agents described herein. In some embodiments, the linker is not cleavable by enzymes of the complement system. For example, the conjugate and / or agent is released without complement activation since complement activation ultimately lyses the target cell. In such embodiments, the conjugate and / or agent is to be delivered to the target cell (e.g., hormones, enzymes, corticosteroids, neurotransmitters, or genes). Furthermore, the linker is mildly susceptible to cleavage by serum proteases, and the conjugate and / or agent is released slowly at the target site. In some embodiments of any of the ACCs described herein, the conjugate and / or agent is designed such that the conjugate and / or agent is delivered to the target site (e.g., disease tissue (e.g., cancerous tissue)) but the conjugate and / or agent is not released. In some embodiments of any of the ACCs described herein, the conjugate and / or agent is attached to an antigen-binding domain either directly or via a non-cleavable linker. Exemplary non-cleavable linkers include amino acids (e.g., D-amino acids), peptides, or other organic compounds that may be modified to include functional groups that can subsequently be utilized in attachment to antigen-binding domains by methods described herein. In some embodiments of any of the ACCs described herein, an ACC includes at least one point of conjugation for an agent. In some embodiments, all possible points of conjugation are available for conjugation to an agent. In some embodiments, the one or more points of conjugation include, without limitation, sulfur atoms involved in disulfide bonds, sulfur atoms involved in interchain disulfide bonds, sulfur atoms involved in interchain sulfide bonds but not sulfur atoms involved in intrachain disulfide bonds,, and / or sulfur atoms of cysteine or other amino acid residues containing a sulfur atom. In such cases, residues may occur naturally in the protein construct structure or may be incorporated into the protein construct using methods including, without limitation, site-directed mutagenesis, chemical conversion, or mis-incorporation of non-natural amino acids. This disclosure also provides methods and materials for preparing an ACC for conjugation. In some embodiments of any of the ACCs described herein, an ACC is modified to include one or more interchain disulfide bonds. For example, disulfide bonds in the ACC can undergo reduction following exposure to a reducing agent such as, without limitation, TCEP, DTT, or P-mercaptoethanol. In some cases, the reduction of the disulfide bonds is only partial. As used herein, the term partial reduction refers to situations where an ACC is contacted with a reducing agent and a fraction of all possible sites of conjugation undergo reduction (e.g., not all disulfide bonds are reduced). In some embodiments, an activatable cytokine construct is partially reduced following contact with a reducing agent if less than 99%, (e.g., less than 98%, 97%, 96%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10% or less than 5%) of all possible sites of conjugation are reduced. In some embodiments, the ACC having a reduction in one or more interchain disulfide bonds is conjugated to a drug reactive with free thiols. This disclosure also provides methods and materials for conjugating a therapeutic agent to a particular location on an ACC. In some embodiments of any of the ACC described herein, an ACC is modified so that the therapeutic agents can be conjugated to the ACC at particular locations on the ACC. For example, an ACC can be partially reduced in a manner that facilitates conjugation to the ACC. In such cases, partial reduction of the ACC occurs in a manner that conjugation sites in the ACC are not reduced. In some embodiments, the conjugation site(s) on the ACC are selected to facilitate conjugation of an agent at a particular location on the protein construct. Various factors can influence the “level of reduction” of the ACC upon treatment with a reducing agent. For example, without limitation, the ratio of reducing agent to ACC, length of incubation, incubation temperature, and / or pH of the reducing reaction solution can require optimization in order to achieve partial reduction of the ACC with the methods and materials described herein. Any appropriate combination of factors (e.g., ratio of reducing agent to ACC, the length and temperature of incubation with reducing agent, and / or pH of reducing agent) can be used to achieve partial reduction of the ACC (e.g., general reduction of possible conjugation sites or reduction at specific conjugation sites). An effective ratio of reducing agent to ACC can be any ratio that at least partially reduces the ACC in a manner that allows conjugation to an agent (e.g., general reduction of possible conjugation sites or reduction at specific conjugation sites). In some embodiments, the ratio of reducing agent to ACC will be in a range from about 20:1 to 1:1, from about 10:1 to 1:1, from about 9:1 to 1:1, from about 8:1 to 1:1, from about 7:1 to 1:1, from about 6:1 to 1:1, from about 5:1 to 1:1, from about 4:1 to 1:1, from about 3:1 to 1:1, from about 2:1 to 1:1, from about 20:1 to 1:1.5, from about 10:1 to 1:1.5, from about 9:1 to 1:1.5, from about 8:1 to 1:1.5, from about 7:1 to 1:1.5, from about 6:1 to 1:1.5, from about 5:1 to 1:1.5, from about 4:1 to 1:1.5, from about 3:1 to 1:1.5, from about 2:1 to 1:1.5, from about 1.5:1 to 1:1.5, or from about 1:1 to 1:1.5. In some embodiments, the ratio is in a range of from about 5:1 to 1:1. In some embodiments, the ratio is in a range of from about 5:1 to 1.5:1. In some embodiments, the ratio is in a range of from about 4:1 to 1:1. In some embodiments, the ratio is in a range from about 4:1 to 1.5:1. In some embodiments, the ratio is in a range from about 8:1 to about 1:1. In some embodiments, the ratio is in a range of from about 2.5:1 to 1:1. An effective incubation time and temperature for treating an ACC with a reducing agent can be any time and temperature that at least partially reduces the ACC in a manner that allows conjugation of an agent to an ACC (e.g., general reduction of possible conjugation sites or reduction at specific conjugation sites). In some embodiments, the incubation time and temperature for treating an ACC will be in a range from about 1 hour at 37 °C to about 12 hours at 37 °C (or any subranges therein). An effective pH for a reduction reaction for treating an ACC with a reducing agent can be any pH that at least partially reduces the ACC in a manner that allows conjugation of the ACC to an agent (e.g., general reduction of possible conjugation sites or reduction at specific conjugation sites). When a partially-reduced ACC is contacted with an agent containing thiols, the agent can conjugate to the interchain thiols in the ACC. An agent can be modified in a manner to include thiols using a thiol-containing reagent (e.g., cysteine or N-acetyl cysteine). For example, the ACC can be partially reduced following incubation with reducing agent (e.g., TEPC) for about 1 hour at about 37 °C at a desired ratio of reducing agent to ACC. An effective ratio of reducing agent to ACC can be any ratio that partially reduces at least two interchain disulfide bonds located in the ACC in a manner that allows conjugation of a thiol-containing agent (e.g., general reduction of possible conjugation sites or reduction at specific conjugation sites). In some embodiments of any of the ACCs described herein, an ACC is reduced by a reducing agent in a manner that avoids reducing any intrachain disulfide bonds. In some embodiments of any of the ACCs described herein, an ACC is reduced by a reducing agent in a manner that avoids reducing any intrachain disulfide bonds and reduces at least one interchain disulfide bond. In some embodiments of any of the ACCs described herein, the ACC can also include an agent conjugated to the ACC. In some embodiments, the conjugated agent is a therapeutic agent. In some embodiments, the agent (e.g., agent conjugated to an activatable cytokine construct) is a detectable moiety such as, for example, a label or other marker. For example, the agent is or includes a radiolabeled amino acid, one or more biotinyl moieties that can be detected by marked avidin (e.g., streptavidin containing a fluorescent marker or enzymatic activity that can be detected by optical or calorimetric methods), one or more radioisotopes or radionuclides, one or more fluorescent labels, one or more enzymatic labels, and / or one or more chemiluminescent agents. In some embodiments, detectable moieties are attached by spacer molecules. In some embodiments, the agent (e.g., cytotoxic agent conjugated to an activatable cytokine construct) is linked to the ACC using a carbohydrate moiety, 5 sulfhydryl group, amino group, or carboxylate group. In some embodiments of any of the ACCs described herein conjugated to an agent, the agent (e.g., cytotoxic agent conjugated to an activatable cytokine construct) is conjugated to the ACC via a linker and / or a CM (also referred to as a cleavable sequence). In some embodiments, the agent (e.g., cytotoxic agent conjugated to an 1 o activatable cytokine construct) is conjugated to a cysteine or a lysine in the ACC. In some embodiments, the agent (e.g., cytotoxic agent conjugated to an activatable cytokine construct) is conjugated to another residue of the ACC, such as those residues disclosed herein. In some embodiments, the linker is a thiol-containing linker. Some non-limiting examples of the linker and / or CMs are provided in Table 1. Table 1. Types of Cleavable Sequences / CMs Amino Acid Sequence Plasmin CMs Pro-urokinase TGFp Plasminogen Staphylokinase Factor Xa CMs PRFKIIGG (SEQ ID NO: 253) PRFRIIGG (SEQ ID NO: 254) SSRHRRALD (SEQ ID NO: 255) RKSSIIIRMRDVVL (SEQ ID NO: 256) SSSFDKGKYKKGDDA (SEQ ID NO: 257) SSSFDKGKYKRGDDA (SEQ ID NO: 258) IEGR (SEQ ID NO: 259) IDGR (SEQ ID NO: 260) GGSIDGR (SEQ ID NO: 261) MMPCMs Gelatinase A PLGLWA (SEQ ID NO: 262) Collagenase CMs Calf skin collagen (al (I) chain) GPQGIAGQ (SEQ ID NO: 263) Calf skin collagen (a2(I) chain) GPQGLLGA (SEQ ID NO: 264) Bovine cartilage collagen (al(II) chain) GIAGQ (SEQ ID NO: 265) Human liver collagen (al(III) chain) GPLGIAGI (SEQ ID NO: 266) Human azM GPEGLRVG (SEQ ID NO: 267) Human PZP YGAGLGVV (SEQ ID NO: 268) AGLGVVER (SEQ ID NO: 269) AGLGISST (SEQ ID NO: 270) Rat aiM EPQALAMS (SEQ ID NO: 271) Q ALAMS AI (SEQ ID NO: 272) Rat a2M AAYHLVSQ (SEQ ID NO: 273) MDAFLESS (SEQ ID NO: 274) Rat ail3(2J) ESLPVVAV (SEQ ID NO: 275) Rat ail3(27J) SAPAVESE (SEQ ID NO: 276) Human fibroblast collagenase DVAQFVLT (SEQ ID NO: 277) (autolytic cleavages) VAQFVLT (SEQ ID NO: 278) VAQFVLTE (SEQ ID NO: 279) AQFVLTEG (SEQ ID NO: 280) PVQPIGPQ (SEQ ID NO: 281) Those of ordinary skill in the art will recognize that a large variety of possible moieties can be coupled to the ACCs of the disclosure. (See, for example, “Conjugate Vaccines”, Contributions to Microbiology and Immunology, J. M. Cruse and R. E. 5 Lewis, Jr (eds), Carger Press, New York, (1989), the entire contents of which are incorporated herein by reference). In general, an effective conjugation of an agent (e.g., cytotoxic agent) to an ACC can be accomplished by any chemical reaction that will bind the agent to the ACC while also allowing the agent and the ACC to retain functionality. In some embodiments of any of the ACCs conjugated to an agent, a variety of 1 o bifunctional protein-coupling agents can be used to conjugate the agent to the ACC including, without limitation, N-succinimidyl-3-(2-pyridyl dithiol) propionate (SPDP), iminothiolane (IT), bifunctional derivatives of imidoesters (e.g., dimethyl adipimidate HCL), active esters (e.g., disuccinimidyl suberate), aldehydes (e.g., glutareldehyde), bisazido compounds (e.g., bis (p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (e.g., bis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (e.g., tolyene 2,6-diisocyanate), and bis-active fluorine compounds (e.g., l,5-difluoro-2,4-dinitrobenzene). For example, a ricin immunotoxin can be prepared as described in Vitetta et al., Science 238: 1098 (1987). In some embodiments, a carbon-14-labeled l-isothiocyanatobenzyl-3-methyldiethylene triaminepentaacetic acid (MX-DTPA) chelating agent can be used to conjugate a radionucleotide to the ACC. (See, e.g., WO94 / 11026). Suitable linkers and CMs are described in the literature. (See, for example, Ramakrishnan, S. etal., Cancer Res. 44:201-208 (1984) describing use of MBS (M-maleimidobenzoyl-N-hydroxysuccinimide ester). See also, U.S. Patent No. 5,030,719, describing use of halogenated acetyl hydrazide derivative coupled to an ACC by way of an oligopeptide linker. In some embodiments, suitable linkers include: (i) EDC (1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride; (ii) SMPT (4-succinimidyloxycarbonyl-alpha-methyl-alpha-(2-pridyl-dithio)-toluene (Pierce Chern. Co., Cat. (21558G); (iii) SPDP (succinimidyl-6 [3-(2-pyridyldithio) propionamido] hexanoate (Pierce Chern. Co., Cat #21651G); (iv) Sulfo-LC-SPDP (sulfosuccinimidyl 6 [3-(2-pyridyldithio)-propianamide] hexanoate (Pierce Chern. Co. Cat. #2165-G); and (v) sulfo-NHS (N-hydroxysulfo-succinimide: Pierce Chern. Co., Cat. #24510) conjugated to EDC. Additional linkers include, but are not limited to, SMCC, sulfo-SMCC, SPDB, or sulfo-SPDB. The linkers and CMs described above contain components that have different attributes, thus leading to conjugates with differing physio-chemical properties. For example, sulfo-NHS esters of alkyl carboxylates are more stable than sulfo-NHS esters of aromatic carboxylates. NHS-ester containing linkers are less soluble than sulfo-NHS esters. Further, the linker SMPT contains a sterically-hindered disulfide bond, and can form conjugates with increased stability. Disulfide linkages, are in general, less stable than other linkages because the disulfide linkage is cleaved in vitro, resulting in less conjugate available. Sulfo-NHS, in particular, can enhance the stability of carbodimide couplings. Carbodimide couplings (such as EDC) when used in conjunction with sulfo- NHS, forms esters that are more resistant to hydrolysis than the carbodimide coupling reaction alone. In some embodiments of any of the ACCs, an agent can be conjugated to the ACC using a modified amino acid sequence included in the amino acid sequence of the ACC. By inserting conjugation-enabled amino acids at specific locations within the amino acid sequence of the ACC, the protein construct can be designed for controlled placement and / or dosage of the conjugated agent (e.g., cytotoxic agent). For example, the ACC can be modified to include a cysteine amino acid residue at positions on the first monomer, the second monomer, the third monomer, and / or the fourth monomer that provide reactive thiol groups and does not negatively impact protein folding and / or assembly and does not alter antigen-binding properties. In some embodiments, the ACC can be modified to include one or more non-natural amino acid residues within the amino acid sequence of the ACC to provide suitable sites for conjugation. In some embodiments, the ACC can be modified to include enzymatically activatable peptide sequences within the amino acid sequence of the ACC. Nucleic Acids Provided herein are nucleic acids including sequences that encode the first monomer construct (or the protein portion of the first monomer construct) (e.g., any of the first monomers constructs described herein) and the second monomer construct (or the protein portion of the second monomer construct) (e.g., any of the second monomer constructs described herein) of any of the ACCs described herein. In some embodiments, a pair of nucleic acids together encode the first monomer construct (or the protein portion of the first monomer construct) and the second monomer construct (or the protein portion of the second monomer construct). In some embodiments, the nucleic acid sequence encoding the first monomer construct (or the protein portion of the first monomer construct) is at least 70% identical (e.g., at least 72% identical, at least 74% identical, at least 76% identical, at least 78% identical, at least 80% identical, at least 82% identical, at least 84 % identical, at least 86% identical, at least 88% identical, at least 90% identical, at least 92% identical, at least 94% identical, at least 96% identical, at least 98% identical, at least 99% identical, or 100% identical) to the nucleic acid sequence encoding the second monomer construct (or the protein portion of the second monomer construct). In some embodiments, the nucleic acid encoding the protein portion of a first monomer construct encodes a polypeptide comprising the PM1, CPI, CM1, and CM3 moieties. In some embodiments, the nucleic acid encoding the protein portion of a second monomer encodes a polypeptide comprising the CP2 and CM2moieties. In some embodiments, the nucleic acid encoding the protein portion of a second monomer encodes a polypeptide comprising the CP2, CM2, PM2, and CM4 moieties. In some embodiments, a pair of nucleic acids together encode the protein portion of a first monomer construct and the protein portion of the second monomer construct, wherein the protein portions are then conjugated to the DD1 and DD2 moieties, respectively (in a subsequent conjugation step). In some embodiments, the nucleic acid encoding the first monomer construct encodes a polypeptide comprising the DD1 moiety. In some embodiments, the nucleic acid encoding the second monomer construct encodes a polypeptide comprising the DD2 moiety. Vectors Provided herein are vectors and sets of vectors including any of the nucleic acids described herein. One skilled in the art will be capable of selecting suitable vectors or sets of vectors (e.g., expression vectors) for making any of the ACCs described herein, and using the vectors or sets of vectors to express any of the ACCs described herein. For example, in selecting a vector or a set of vectors, the cell must be considered because the vector(s) may need to be able to integrate into a chromosome of the cell and / or replicate in it. Exemplary vectors that can be used to produce an ACC are also described below. As used herein, the term “vector” refers to a polynucleotide capable of inducing the expression of a recombinant protein (e.g., a first or second monomer) in a cell (e.g., any of the cells described herein). A “vector” is able to deliver nucleic acids and fragments thereof into a host cell, and includes regulatory sequences (e.g., promoter, enhancer, poly(A) signal). Exogenous polynucleotides may be inserted into the expression vector in order to be expressed. The term “vector” also includes artificial chromosomes, plasmids, retroviruses, and baculovirus vectors. Methods for constructing suitable vectors that include any of the nucleic acids described herein, and suitable for transforming cells (e.g., mammalian cells) are well-known in the art. See, e.g., Sambrook et al., Eds. “Molecular Cloning: A Laboratory Manual,” 2nd Ed., Cold Spring Harbor Press, 1989 and Ausubel et al., Eds. “Current Protocols in Molecular Biology,” Current Protocols, 1993. Non-limiting examples of vectors include plasmids, transposons, cosmids, and viral vectors (e.g., any adenoviral vectors (e.g., pSV or pCMV vectors), adeno-associated virus (AAV) vectors, lentivirus vectors, and retroviral vectors), and any Gateway® vectors. A vector can, for example, include sufficient cis-acting elements for expression; other elements for expression can be supplied by the host mammalian cell or in an in vitro expression system. Skilled practitioners will be capable of selecting suitable vectors and mammalian cells for making any of the ACCs described herein. In some embodiments of any of the ACCs described herein, the ACC may be made biosynthetically using recombinant DNA technology and expression in eukaryotic or prokaryotic species. In some embodiments, the vector includes a nucleic acid encoding the first monomer and the second monomer of any of the ACCs described herein. In some embodiments, the vector is an expression vector. In some embodiments, a pair of vectors together include a pair of nucleic acids that together encode the first monomer and the second monomer of any of the ACCs described herein. In some embodiments, the pair of vectors is a pair of expression vectors. Cells Also provided herein are host cells including any of the vector or sets of vectors described herein including any of the nucleic acids described herein. Any of the ACCs and antibodies described herein can be produced by any cell (e.g., a mammalian cell). In some embodiments, a host cell is a mammalian cell (e.g., a human cell), a rodent cell (e.g., a mouse cell, a rat cell, a hamster cell, or a guinea pig cell), or a non-human primate cell. Methods of introducing nucleic acids and vectors (e.g., any of the vectors or any of the sets of vectors described herein) into a cell are known in the art. Non-limiting examples of methods that can be used to introducing a nucleic acid into a cell include: lipofection, transfection, calcium phosphate transfection, cationic polymer transfection, viral transduction (e.g., adenoviral transduction, lentiviral transduction), nanoparticle transfection, and electroporation. In some embodiments, the introducing step includes introducing into a cell a vector (e.g., any of the vectors or sets of vectors described herein) including a nucleic acid encoding the monomers that make up any of the ACCs and antibodies described herein. In some embodiments of any of the methods described herein, the cell can be a eukaryotic cell. As used herein, the term “eukaryotic cell” refers to a cell having a distinct, membrane-bound nucleus. Such cells may include, for example, mammalian (e.g., rodent, non-human primate, or human), insect, fungal, or plant cells. In some embodiments, the eukaryotic cell is a yeast cell, such as Saccharomyces cerevisiae. In some embodiments, the eukaryotic cell is a higher eukaryote, such as mammalian, avian, plant, or insect cells. Non-limiting examples of mammalian cells include Chinese hamster ovary (CHO) cells and human embryonic kidney cells (e.g., HEK293 cells). In some embodiments, the cell contains the nucleic acid encoding the first monomer and the second monomer of any one of the ACCs and antibodies described herein. In some embodiments, the cell contains the pair of nucleic acids that together encode the first monomer and the second monomer of any of the ACCs and antibodies described herein. Methods of Producing Activatable Cytokine Constructs Provided herein are methods of producing any of the ACCs described herein that include: (a) culturing any of the recombinant host cells described herein in a liquid culture medium under conditions sufficient to produce the ACC; and (b) recovering the ACC from the host cell and / or the liquid culture medium. Methods of culturing cells are well known in the art. Cells can be maintained in vitro under conditions that favor cell proliferation, cell differentiation and cell growth. For example, cells can be cultured by contacting a cell (e.g., any of the cells described herein) with a cell culture medium that includes the necessary growth factors and supplements sufficient to support cell viability and growth. In some embodiments of any of the methods described herein, the method further includes isolating the recovered ACC. Non-limiting examples of methods of isolation include: ammonium sulfate precipitation, polyethylene glycol precipitation, size exclusion chromatography, ligand-affinity chromatography, ion-exchange chromatography (e.g., anion or cation), and hydrophobic interaction chromatography. In some embodiments, the cells can produce a protein portion of a first monomer construct that includes the CPI, the CM1, the PM2, and the CM3, and a protein portion of a second monomer construct that includes the CP2, and the CM2, and optionally the PM2 and the CM4, and then the protein portions are subsequently conjugated to the DD1 and DD2 moieties, respectively. Compositions and methods described herein may involve use of non-reducing or partially-reducing conditions that allow disulfide bonds to form between the dimerization domains to form and maintain dimerization of the ACCs. In some embodiments of any of the methods described herein, the method further includes formulating the isolated ACC into a pharmaceutical composition. Various formulations are known in the art and are described herein. Any of the isolated ACCs and / or antibodies described herein can be formulated for any route of administration (e.g., intravenous, intratumoral, subcutaneous, intradermal, oral (e.g., inhalation), transdermal (e.g., topical), transmucosal, or intramuscular). Also provided herein are ACCs produced by any of the methods described herein. Also provided are compositions (e.g., pharmaceutical compositions) that include any of the ACCs produced by any of the methods described herein. Also provided herein are kits that include at least one dose of any of the compositions (e.g., pharmaceutical compositions) described herein. Methods of Treatment Provided herein are methods of treating a disease (e.g., a cancer (e.g., any of the cancers described herein) or an infectious disease) in a subject including administering a therapeutically effective amount of any of the ACCs and antibodies described herein to the subject. As used herein, the term “subject” refers to any mammal. In some embodiments, the subject is a feline (e.g., a cat), a canine (e.g., a dog), an equine (e.g., a horse), a rabbit, a pig, a rodent (e.g., a mouse, a rat, a hamster or a guinea pig), a non-human primate (e.g., a simian (e.g., a monkey (e.g., a baboon, a marmoset), or an ape (e.g., a chimpanzee, a gorilla, an orangutan, or a gibbon)), or a human. In some embodiments, the subject is a human. In some embodiments, the subject has been previously identified or diagnosed as having the disease (e.g., cancer (e.g., any of the cancers described herein)). As used herein, the term “treat” includes reducing the severity, frequency or the number of one or more (e.g., 1, 2, 3, 4, or 5) symptoms or signs of a disease (e.g., a cancer (e.g., any of the cancers described herein)) in the subject (e.g., any of the subjects described herein). In some embodiments where the disease is cancer, treating results in reducing cancer growth, inhibiting cancer progression, inhibiting cancer metastasis, or reducing the risk of cancer recurrence in a subject having cancer. In some embodiments, the methods and uses of the present disclosure include administering the ACC and the PD-1 / PD-L1 pathway inhibitor simultaneously or sequentially, e.g., in series in any order. In some embodiments, the methods and uses of the present disclosure include administering the ACC and the PD-1 / PD-L1 pathway inhibitor separately. In some aspects, a therapeutic or a sub-therapeutic dose of each agent is administered. In some aspects, the methods and uses of the present disclosure include administering the ACC and the PD-1 / PD-L1 pathway inhibitor sequentially or simultaneously such that an additive or synergistic therapeutic effect is achieved in the subject. As used herein, die term “combination” broadly includes administration simultaneously or sequentially and also includes administering the actives separately or in the same composition or container. In particular, an ACC for use in combination may contain IL-2, M.-7, IL-8, IL-10, IL-12, 0.-15. IL-21, an IFN-alpha, an IFNbeta, an IFN gamma, GM-CSF, TGF-beta, LIGHT, GITR-L, CD40L, CD27L, 4-1BB-L, 0X40, OX40L. In some embodiments, the methods and uses of the present disclosure include any route of administration including intravenous, infusion, intratumoral, subcutaneous, intraperitoneal, intradermal, oral (e.g., inhalation), intranasal, transdermal (e.g., topical), transmucosal, and / or intramuscular. In some embodiments of any of the methods described herein, the disease is a cancer. Also provided herein are methods of treating a subject in need thereof (e.g., any of the exemplary subjects described herein or known in the art) that include administering to the subject a therapeutically effective amount of any of the ACCs described herein or any of the compositions (e.g., pharmaceutical compositions) described herein. In some embodiments of these methods, the subject has been identified or diagnosed as having a cancer. Non-limiting examples of cancer include: solid tumor, hematological tumor, sarcoma, osteosarcoma, glioblastoma, neuroblastoma, melanoma, rhabdomyosarcoma, Ewing sarcoma, osteosarcoma, B-cell neoplasms, multiple myeloma, a lymphoma (e.g., B-cell lymphoma, B-cell non-Hodgkin’s lymphoma, Hodgkin’s lymphoma, cutaneous T-cell lymphoma), a leukemia (e.g., hairy cell leukemia, chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphocytic leukemia (ALL)), myelodysplastic syndromes (MDS), Kaposi sarcoma, retinoblastoma, stomach cancer, urothelial carcinoma, lung cancer, renal cell carcinoma, gastric and esophageal cancer, pancreatic cancer, prostate cancer, brain cancer, colon cancer, bone cancer, lung cancer, breast cancer, colorectal cancer, ovarian cancer, nasopharyngeal adenocarcimoa, non-small cell lung carcinoma (NSCLC), squamous cell head and neck carcinoma, endometrial cancer, bladder cancer, cervical cancer, liver cancer, and hepatocellular carcinoma. In some embodiments, the cancer is a lymphoma. In some embodiments, the lymphoma is Burkitt’s lymphoma. In some aspects, the subject has been identified or diagnosed as having familial cancer syndromes such as Li Fraumeni Syndrome, Familial Breast-Ovarian Cancer (BRCA1 or BRAC2 mutations) Syndromes, and others. The disclosed methods are also useful in treating nonsolid cancers. Exemplary solid tumors include malignancies (e.g., sarcomas, adenocarcinomas, and carcinomas) of the various organ systems, such as those of lung, breast, lymphoid, gastrointestinal (e.g., colon), and genitourinary (e.g., renal, urothelial, or testicular tumors) tracts, pharynx, prostate, and ovary. Exemplary adenocarcinomas include colorectal cancers, renal-cell carcinoma, liver cancer, non-small cell carcinoma of the lung, and cancer of the small intestine. Exemplary cancers described by the National Cancer Institute include: Acute Lymphoblastic Leukemia, Adult; Acute Lymphoblastic Leukemia, Childhood; Acute Myeloid Leukemia, Adult; Adrenocortical Carcinoma; Adrenocortical Carcinoma, Childhood; AIDS-Related Lymphoma; AIDS-Related Malignancies; Anal Cancer; Astrocytoma, Childhood Cerebellar; Astrocytoma, Childhood Cerebral; Bile Duct Cancer, Extrahepatic; Bladder Cancer; Bladder Cancer, Childhood; Bone Cancer, Osteosarcoma / Malignant Fibrous Histiocytoma; Brain Stem Glioma, Childhood; Brain Tumor, Adult; Brain Tumor, Brain Stem Glioma, Childhood; Brain Tumor, Cerebellar Astrocytoma, Childhood; Brain Tumor, Cerebral Astrocytoma / Malignant Glioma, Childhood; Brain Tumor, Ependymoma, Childhood; Brain Tumor, Medulloblastoma, Childhood; Brain Tumor, Supratentorial Primitive Neuroectodermal Tumors, Childhood; Brain Tumor, Visual Pathway and Hypothalamic Glioma, Childhood; Brain Tumor, Childhood (Other); Breast Cancer; Breast Cancer and Pregnancy; Breast Cancer, Childhood; Breast Cancer, Male; Bronchial Adenomas / Carcinoids, Childhood; Carcinoid Tumor, Childhood; Carcinoid Tumor, Gastrointestinal; Carcinoma, Adrenocortical; Carcinoma, Islet Cell; Carcinoma of Unknown Primary; Central Nervous System Lymphoma, Primary; Cerebellar Astrocytoma, Childhood; Cerebral Astrocytoma / Malignant Glioma, Childhood; Cervical Cancer; Childhood Cancers; Chronic Lymphocytic Leukemia; Chronic Myelogenous Leukemia; Chronic Myeloproliferative Disorders; Clear Cell Sarcoma of Tendon Sheaths; Colon Cancer; Colorectal Cancer, Childhood; Cutaneous T-Cell Lymphoma; Endometrial Cancer; Ependymoma, Childhood; Epithelial Cancer, Ovarian; Esophageal Cancer; Esophageal Cancer, Childhood; Ewing's Family of Tumors; Extracranial Germ Cell Tumor, Childhood; Extragonadal Germ Cell Tumor; Extrahepatic Bile Duct Cancer; Eye Cancer, Intraocular Melanoma; Eye Cancer, Retinoblastoma; Gallbladder Cancer; Gastric (Stomach) Cancer; Gastric (Stomach) Cancer, Childhood; Gastrointestinal Carcinoid Tumor; Germ Cell Tumor, Extracranial, Childhood; Germ Cell Tumor, Extragonadal; Germ Cell Tumor, Ovarian; Gestational Trophoblastic Tumor; Glioma, Childhood Brain Stem; Glioma, Childhood Visual Pathway and Hypothalamic; Hairy Cell Leukemia; Head and Neck Cancer; Hepatocellular (Liver) Cancer, Adult (Primary); Hepatocellular (Liver) Cancer, Childhood (Primary); Hodgkin's Lymphoma, Adult; Hodgkin's Lymphoma, Childhood; Hodgkin's Lymphoma During Pregnancy; Hypopharyngeal Cancer; Hypothalamic and Visual Pathway Glioma, Childhood; Intraocular Melanoma; Islet Cell Carcinoma (Endocrine Pancreas); Kaposi's Sarcoma; Kidney Cancer; Laryngeal Cancer; Laryngeal Cancer, Childhood; Leukemia, Acute Lymphoblastic, Adult; Leukemia, Acute Lymphoblastic, Childhood; Leukemia, Acute Myeloid, Adult; Leukemia, Acute Myeloid, Childhood; Leukemia, Chronic Lymphocytic; Leukemia, Chronic Myelogenous; Leukemia, Hairy Cell; Lip and Oral Cavity Cancer; Liver Cancer, Adult (Primary); Liver Cancer, Childhood (Primary); Lung Cancer, Non-Small Cell; Lung Cancer, Small Cell; Lymphoblastic Leukemia, Adult Acute; Lymphoblastic Leukemia, Childhood Acute; Lymphocytic Leukemia, Chronic; Lymphoma, AIDS-Related; Lymphoma, Central Nervous System (Primary); Lymphoma, Cutaneous T-Cell; Lymphoma, Hodgkin's, Adult; Lymphoma, Hodgkin's, Childhood; Lymphoma, Hodgkin's During Pregnancy; Lymphoma, Non-Hodgkin's, Adult; Lymphoma, Non-Hodgkin's, Childhood; Lymphoma, Non-Hodgkin's During Pregnancy; Lymphoma, Primary Central Nervous System; Macroglobulinemia, Waldenstrom's; Male Breast Cancer; Malignant Mesothelioma, Adult; Malignant Mesothelioma, Childhood; Malignant Thymoma; Medulloblastoma, Childhood; Melanoma; Melanoma, Intraocular; Merkel Cell Carcinoma; Mesothelioma, Malignant; Metastatic Squamous Neck Cancer with Occult Primary; Multiple Endocrine Neoplasia Syndrome, Childhood; Multiple Myeloma / Plasma Cell Neoplasm; Mycosis Fungoides; Myelodysplastic Syndromes; Myelogenous Leukemia, Chronic; Myeloid Leukemia, Childhood Acute; Myeloma, Multiple; Myeloproliferative Disorders, Chronic; Nasal Cavity and Paranasal Sinus Cancer; Nasopharyngeal Cancer; Nasopharyngeal Cancer, Childhood; Neuroblastoma; Non-Hodgkin's Lymphoma, Adult; Non-Hodgkin's Lymphoma, Childhood; Non-Hodgkin's Lymphoma During Pregnancy; Non-Small Cell Lung Cancer; Oral Cancer, Childhood; Oral Cavity and Lip Cancer; Oropharyngeal Cancer; Osteosarcoma / Malignant Fibrous Histiocytoma of Bone; Ovarian Cancer, Childhood; Ovarian Epithelial Cancer; Ovarian Germ Cell Tumor; Ovarian Low Malignant Potential Tumor; Pancreatic Cancer; Pancreatic Cancer, Childhood; Pancreatic Cancer, Islet Cell; Paranasal Sinus and Nasal Cavity Cancer; Parathyroid Cancer; Penile Cancer; Pheochromocytoma; Pineal and Supratentorial Primitive Neuroectodermal Tumors, Childhood; Pituitary Tumor; Plasma Cell Neoplasm / Multiple Myeloma; Pleuropulmonary Blastoma; Pregnancy and Breast Cancer; Pregnancy and Hodgkin's Lymphoma; Pregnancy and Non-Hodgkin's Lymphoma; Primary Central Nervous System Lymphoma; Primary Liver Cancer, Adult; Primary Liver Cancer, Childhood; Prostate Cancer; Rectal Cancer; Renal Cell (Kidney) Cancer; Renal Cell Cancer, Childhood; Renal Pelvis and Ureter, Transitional Cell Cancer; Retinoblastoma; Rhabdomyosarcoma, Childhood; Salivary Gland Cancer; Salivary Gland Cancer, Childhood; Sarcoma, Ewing's Family of Tumors; Sarcoma, Kaposi's; Sarcoma (Osteosarcoma) / Malignant Fibrous Histiocytoma of Bone; Sarcoma, Rhabdomyosarcoma, Childhood; Sarcoma, Soft Tissue, Adult; Sarcoma, Soft Tissue, Childhood; Sezary Syndrome; Skin Cancer; Skin Cancer, Childhood; Skin Cancer (Melanoma); Skin Carcinoma, Merkel Cell; Small Cell Lung Cancer; Small Intestine Cancer; Soft Tissue Sarcoma, Adult; Soft Tissue Sarcoma, Childhood; Squamous Neck Cancer with Occult Primary, Metastatic; Stomach (Gastric) Cancer; Stomach (Gastric) Cancer, Childhood; Supratentorial Primitive Neuroectodermal Tumors, Childhood; T-Cell Lymphoma, Cutaneous; Testicular Cancer; Thymoma, Childhood; Thymoma, Malignant; Thyroid Cancer; Thyroid Cancer, Childhood; Transitional Cell Cancer of the Renal Pelvis and Ureter; Trophoblastic Tumor, Gestational; Unknown Primary Site, Cancer of, Childhood; Unusual Cancers of Childhood; Ureter and Renal Pelvis, Transitional Cell Cancer; Urethral Cancer; Uterine Sarcoma; Vaginal Cancer; Visual Pathway and Hypothalamic Glioma, Childhood; Vulvar Cancer; Waldenstrom's Macro globulinemia; and Wilms' Tumor. Further exemplary cancers include diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL). Metastases of the aforementioned cancers can also be treated or prevented in accordance with the methods described herein. In some embodiments, these methods can result in a reduction in the number, severity, or frequency of one or more symptoms of the cancer in the subject (e.g., as compared to the number, severity, or frequency of the one or more symptoms of the cancer in the subject prior to treatment). In some embodiments of any of the methods described herein, the disease is an infectious disease. The ACCs and antibodies of the present disclosure may also be used to prevent or treat infections and infectious diseases. The ACCs and antibodies can be used to stimulate immune responses against pathogens, toxins, and autoantigens. The ACCs and antibodies can be used to stimulate immune responses to pathogenic viruses including, but not limited to HIV, hepatitis (A, B or C) virus, herpes virus (e.g., VZV, HSV-1, HAV-6, HSV-II, CMV, and Epstein-Barr virus), adenovirus, influenza viruses, flavivirus, echovirus, rhinovirus, coxsackie virus, coronaviruses, respiratory syncytial virus, mumps virus, rotavirus, measles virus, rubella virus, parvovirus, vaccinia virus, HTLV virus, dengue virus, papillomavirus, molluscum virus, poliovirus, rabies virus, JC virus, and arboviral encephalitis virus. The ACCs and antibodies can also be used to stimulate immune responses to infections caused by bacteria, fungi, parasites, or other pathogens. In some embodiments of any of the methods described herein, the methods further include administering to a subject an additional therapeutic agent (e.g., one or more of the therapeutic agents listed in Table 2). Table 2. Additional Therapeutic Agents Antibody Trade Name (antibody name) Target Raptiva™ (efalizumab) CDlla Arzerra™ (ofatumumab) CD20 Bexxar™ (tositumomab) CD20 Gazyva™ (obinutuzumab) CD20 Ocrevus™ (ocrelizumab) CD20 Rituxan™ (rituximab) CD20 Zevalin™ (ibritumomab tiuxetan) CD20 Adcetris™ (brentuximab vedotin) CD30 Myelotarg™ (gemtuzumab) CD33 Mylotarg™ (gemtuzumab ozogamicin) CD33 (vadastuximab) CD33 (vadastuximab talirine) CD33 Campath™ (alemtuzumab) CD52 Lemtrada™ (alemtuzumab) CD52 Tactress™ (tamtuvetmab) CD52 Soliris™ (eculizumab) Complement C5 UI tomiris™ (ravulizumab) Complement C5 (olendalizumab) Complement C5 Yervoy™ (ipilimumab) CTLA-4 (tremelimumab) CTLA-4 Orencia™ (abatacept) CTLA-4 Hu5c8 CD40L (letolizumab) CD40L Rexomun™ (ertumaxomab) CD3 / Her2 Erbitux™ (cetuximab) EGFR Portrazza™ (necitumumab) EGFR Vectibix™ (panitumumab) EGFR CH806 EGFR (depatuxizumab) EGFR (depatuxizumab mafodotin) EGFR (futuximab: modotuximab) EGFR ICR62 (imgatuzumab) EGFR (laprituximab) EGFR (losatuxizumab) EGFR (losatuxizumab vedotin) EGFR mAb 528 EGFR (matuzumab) EGFR (nimotuzumab) EGFR (tomuzotuximab) EGFR (zalutumumab) EGFR MDX-447 EGFR / CD64 (adecatumumab) EpCAM Panorex™ (edrecolomab) EpCAM Vicinium™ EpCAM Synagis™ (palivizumab) F protein of RSV ReoPro™ (abiciximab) Glycoprotein receptor Ilb / IIIa Herceptin™ (trastuzumab) Her2 Herceptin™ Hylecta (trastuzumab; Hyaluronidase) Her2 (trastuzumab deruxtecan) Her2 (hertuzumab verdotin) Her2 Kadcyla™ (trastuzumab emtansine) Her2 (margetuximab) Her2 (timigutuzumab) Her2 Xolair™ (omalizumab) IgE (ligelizumab) IgE (figitumumab) IGF1R (teprotumumab) IGF1R Simulect™ (basiliximab) IL2R Zenapax™ (daclizumab) IL2R Zinbryta™ (daclizumab) IL2R Actemra™ (tocilizumab) IL-6 receptor Kevzara™ (sarilumab) IL-6 receptor (vobarilizumab) IL-6 receptor Stelara™ (ustekinumab) IL-12 / IL-23 Tysabri™ (natalizumab) Integrina4 (abrilumab) Integrina4 Jagged 1 or Jagged 2 (fasinumab) NGF (fulranumab) NGF (tanezumab) NGF Notch, e.g., Notch 1 Pidilizumab Delta like-1 (PD-1 pathway inhibitor) Opdivo® (nivolumab) PD1 Keytruda® (pembrolizumab) PD1 Libtayo® (cemiplimab) PD1 BGB-A317 (tislelizumab) PD1 PDR001 (spartalizumab) PD1 JNJ-63723283 (cetrelimab) PD1 TSR042 (dostarlimab) PD1 AGEN2034 (balstilimab) PD1 JS001 (toripalimab) PD1 IOBI308 (sintilimab) PD1 BCD 100 (prolgolimab) PD1 CBT-501 (genolimzumab PD1 ABB VI81 (budigalimab) PD1 AK105 PD1 B1-754091 PD1 INCSHR-1210 PD1 MEDI0680 PD1 MGA012 PD1 SHR-1210 PD1 Imfinzi™ (durvalumab) PD-L1 Tecentriq® (atezolizumab) PD-L1 Bavencio® (avelumab) PD-L1 KN035 (envafolimab) PD-L1 BMS936559 (MDX1105) PD-L1 BGBA 333 PD-L1 FAZ053 PD-L1 LY-3300054 PD-L1 SH-1316 PD-L1 AMP-224 PD-L2 (bavituximab) Phosphatidylserine huJ591 PSMA RAV12 RAAG12 Prolia™ (denosumab) RANKL GC1008 (fresolimumab) TGFbeta Cimzia™ (Certolizumab Pegol) TNFa Remicade™ (infliximab) TNFa Humira™ (adalimumab) TNFa Simponi™ (golimumab) TNFa Enbrel™ (etanercept) TNF-R (mapatumumab) TRAIL-RI Avastin™ (bevacizumab) VEGF Lucentis™ (ranibizumab) VEGF (brolucizumab) VEGF (vanucizumab) VEGF Compositions / Kits Also provided herein are compositions (e.g., pharmaceutical compositions) including any of the ACCs and / or antibodies described herein and one or more (e.g., 1, 2, 3, 4, or 5) pharmaceutically acceptable carriers (e.g., any of the pharmaceutically acceptable carriers described herein), diluents, or excipients. In some embodiments, the compositions (e.g. pharmaceutical compositions) that include any of the ACCs and / or antibodies described herein can be disposed in a sterile vial or a pre-loaded syringe. In some embodiments, the compositions (e.g. pharmaceutical compositions) that include any of the ACCs and / or antibodies described herein can be formulated for different routes of administration (e.g., intravenous, subcutaneous, intramuscular, intraperitoneal, or intratumoral). In some embodiments, any of the pharmaceutical compositions described herein can include one or more buffers (e.g., a neutral-buffered saline, a phosphate-buffered saline (PBS), amino acids (e.g., glycine), one or more carbohydrates (e.g., glucose, mannose, sucrose, dextran, or mannitol), one or more antioxidants, one or more chelating agents (e.g., EDTA or glutathione), one or more preservatives, and / or a pharmaceutically acceptable carrier (e.g., bacteriostatic water, PBS, or saline). As used herein, the phrase “pharmaceutically acceptable carrier” refers to any and all solvents, dispersion media, coatings, antibacterial agents, antimicrobial agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. Suitable carriers include, but are not limited to: water, saline, ringer’s solutions, dextrose solution, and about 5% human serum albumin. In some embodiments of any of the pharmaceutical compositions described herein, any of the ACCs and / or antibodies described herein are prepared with carriers that protect against rapid elimination from the body, e.g., sustained and controlled release formulations, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, e.g., ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collage, polyorthoesters, and polylactic acid. Methods for preparation of such pharmaceutical compositions and formulations are apparent to those skilled in the art. Also provided herein are kits that include any of the ACCs and / or antibodies described herein, any of the compositions that include any of the ACCs and / or antibodies described herein, or any of the pharmaceutical compositions that include any of the ACCs and / or antibodies described herein. Also provided are kits that include one or more second therapeutic agent(s) selected from Table 2 in addition to an ACC and / or antibody described herein. The second therapeutic agent(s) may be provided in a dosage administration form that is separate from the ACC and / or antibody. Alternatively, the second therapeutic agent(s) may be formulated together with the ACC and / or antibody. Any of the kits described herein can include instructions for using any of the compositions (e.g., pharmaceutical compositions) and / or any of the ACCs and / or antibodies described herein. In some embodiments, the kits can include instructions for performing any of the methods described herein. In some embodiments, the kits can include at least one dose of any of the compositions (e.g., pharmaceutical compositions) described herein. In some embodiments, the kits can provide a syringe for administering any of the pharmaceutical compositions described herein. Anti-PDl sequences In some embodiments the anti-PD-1, which may in certain aspects be configured as an activable antibody and in others aspects not be configured as an activatable antibody, comprises sequences shown below: ml36-M13- MHC723 mlgGl / K MHC723HC.1 Variable heavy chain region amino acid sequence: EVKLVESGGGLVKPGGSLKLSCAASGFTFSGYAMSWVRQTPAKRLEWV AYISNSGGNAHYPDSVKGRFTISRDNAKNTLYLQMSSLRSEDTAMYYCTREDYG TSPFVYWGQGTLVTVSA (SEQ ID NO: 610). MHC723LC.3 Variable light chain region amino acid sequence: DIVLTQSPASLAVSLGQRTTISCRASESVDNYGISFMNWFQQKPGQPPKLL IYAASNQGSGVPARFSGSGSGTDFSLNIHPMEEDDTAVYFCQQSKDVPWTFGGG TKLEIR (SEQ ID NO: 615). MHC725HC.2 Variable heavy chain region amino acid sequence: EVQLQQSGPELVKPGDSVKMSCKASGYTFTDYYMDWVKQSHGKSLEWI GYIYPKNGGSSYNQKFKGKATLTVDKSSSTAYMELHSLTSEDSAVYYCARKVV ATDYWGQGTTLTVSS (SEQ ID NO: 611). MHC725LC.2 Variable light chain region amino acid sequence: DIVMSQSPSSLAVSVGEKVTMSCKSSQSLLYSSNQKNYLAWYQQKPGQSPKLLIF WASIRESGVPDRFTGSGSGTDFTLTISSVKAEDRAVYYCQQCDSYPWTFGGGTK LEIK (SEQ ID NO: 616). MHC728HC.4 Variable heavy chain region amino acid sequence: EVKLVESGGGLVKPGGSLKLSCAASGFTFSNYAMSWVRQTPAKRLEWV AYISNGGGDTHYPDSLKGRFTVSRDNAKNTLYLQMSSLKSEDTAMYYCARENY GTSPFVYWGQGTLVTVSA (SEQ ID NO: 612). MHC728LC.2Variable light chain region amino acid sequence: DIVLTQSPASLAVSLGQRATISCRASESVDNYGISFMNWFQQKPGQPPKLL IYAASNQGSGVPARFSGSGSGTDFSLNIHPMEEDDTAMYFCQQSKDVPWTFGGG TKLEIK (SEQ ID NO: 617). MHC729HC.1 Variable heavy chain region amino acid sequence: EVQLVESGGGLVKSGGSLKLSCAHSGFSFSSYDMSWVRQTPAKRLEWVA TISGGGRYTYYPDSVKGRFTISRDNAKNTLYLQMSGLRSEDTAMYYCASNYYGF DYWGQGTTLTVSS (SEQ ID NO: 613). MHC729LC.3 Variable light chain region amino acid sequence: DIVMTQSHKFMSTSVGDRVSITCKASQDVGTAVAWYQQKPGQSPKLLIY WASTRHTGVPDRFTGSGSGTDFTLTISNVQSEDLADYFCQQYSSYPWTFGGGTK LEIK (SEQIDNO: 618). MHC724HC.3 Variable heavy chain region amino acid sequence: KVMLVESGGDLVKPGGSLKLSCAASGFTFSSYGMSWVRQTPEKRLEWV ATISGGGRDIYYADTVKGRFTISRDNAKNTLYLQMSSLRSEDTALYFCARLYLGF DYWGQGTTLTVSS (SEQ ID NO: 614). MHC724LC.1 Variable light chain region amino acid sequence: DIQMTQSPASQSASLGESVTITCLASQTIGTWLAWYQQKPGKSPQLLIYAA TSLADGVPSRFSG SGSGTKFSFKISSLQAEDFVSYYCQQLYSIPWTFGGGTKLEIK (SEQIDNO: 619). PD-1 A Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSGYAMSWVRQAPGKGLEWV AYISNSGGNAHYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCTREDYG TSPFVYWGQGTLVTVSS (SEQ ID NO: 620). PD-1 Ab Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSGYAMSWVRQAPGKGLEWV SYISNSGGNAHYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKEDYG TSPFVYWGQGTLVTVSS (SEQ ID NO: 621). PD-1 Ae Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSGYAMSWVRQAPGKGLEWV AYISNSGGNTHYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAREDYG TSPFVYWGQGTLVTVSS (SEQ ID NO: 622). PD-1 Af Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSGYAMSWVRQAPGKGLEWV AYISNSGGNTHYADSLKGRFTVSRDNSKNTLYLQMNSLRAEDTAVYYCAREDY GTSPFVYWGQGTLVTVSS (SEQ ID NO: 623). PD-1 Ba Hv Variable heavy chain region amino acid sequence: QVQLVQSGAEVKKPGASVKMSCKASGYTFTDYYMDWVRQAPGQGLEW IGYIYPKNGGSSYAQKFQGRATLTVDTSTSTAYMELSSLRSEDTAVYYCARKVV ATDYWGQGTLLTVSS (SEQ ID NO: 624). PD-1 Bb Hv Variable heavy chain region amino acid sequence: QVQLVQSGAEVKKPGASVKMSCKASGYTFTDYYMDWVRQAPGQGLEW IGYIYPKNGGSSYAQKFQGRATLTVDKSTSTAYMELSSLRSEDTAVYYCARKVV ATDYWGQGTLLTVSS (SEQ ID NO: 625). PD-1 C Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSNYAMSWVRQAPGKGLEWV AYISNGGGDTHYADSLKGRFTVSRDNSKNTLYLQMNSLRAEDTAVYYCARENY GTSPFVYWGQGTLVTVSS (SEQ ID NO: 626). PD-1 Ca Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSNYAMSWVRQAPGKGLEWV AYISNQGGDTHYADSLKGRFTVSRDNSKNTLYLQMNSLRAEDTAVYYCARENY GTSPFVYWGQGTLVTVSS (SEQ ID NO: 627). PD-1 D Hv Variable heavy chain region amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAHSGFSFSSYDMSWVRQAPGKGLEWVA TISGGGRYTYYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCASNYYGF DYWGQGTLLTVSS (SEQ ID NO: 628). PD-11.0 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDNYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 629). PD-11.1 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSVSVGDRATITCRASESVDNYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 630). Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDQYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 631). PD-11.4 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDSYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 632). PD-11.5 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDAYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 633). PD-11.6 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDNYGISFMNWFQQKPGKAPKLL IYAASDQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 634). PD-11.7 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSVSVGDRATITCRASESVDAYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KLEIK (SEQ ID NO: 635). PD-11.9 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDAYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPWTFGQGT KVEIK (SEQ ID NO: 636). PD-11.10 Lv Variable light chain region amino acid sequence: DIQLTQSPSSLSASVGDRVTITCRASESVDAYGISFMNWFQQKPGKAPKLL IYAASNQGSGVPSRFSGSGSGTDFTLTISSMQPEDFATYYCQQSKDVPYTFGQGT KLEIK (SEQ ID NO: 637). PD-12 Lv Variable light chain region amino acid sequence: DIQMTQSPSSLSASVGDRVTMTCKSSQSLLYSSNQKNYLAWYQQKPGKA PKLLIFWASIRESGVPSRFSGSGSGTDFTLTISSVQPEDFATYYCQQSDSYPWTFG QGTKLEIK (SEQ ID NO: 638). PD-14 Lv Variable light chain region amino acid sequence: DIQMTQSPSSLSASVGDRVTITCKASQDVGTAVAWYQQKPGKAPKLLIY WASTRHTGVPSRFSGSGSGTDFTLTISSVQPEDFATYYCQQYSSYPWTFGQGTKL EIK (SEQ ID NO: 639). Kappa constant region amino acid sequence: RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSG NSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRG EC (SEQ ID NO: 640). 5         hIgG4 S228P amino acid sequence: ASTKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGV HTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESKYGPP CPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSQEDPEVQFNWYVD GVEVHNAKTKPREEQFNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKGLPSSIEK 10 TISKAKGQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPEN NYKTTPPVLDSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSL SLGK (SEQ ID NO: 641). In some embodiments, anti-PDl CDR sequences comprise the sequences listed in the following tables. 15 Table 3 VH CDR1 (SEQ ID NO) CDR2 (SEQ ID NO) CDR3 (SEQ ID NO) GFTFSGYAMS YISNSGGNAH EDYGTSPFVY (487) (488) (489) GYTFTDYYMD YIYPKNGGSS KVVATDY (642) (646) (652) GFTFSNYAMS YISNGGGDTH ENYGTSPFVY (643) (647) (653) GFSFSSYDMS TISGGGRYTY NYYGFDY (644) (648) (654) GFTFSSYGMS TISGGGRDIY LYLGFDY (645) (649) (655) GFTFSGYAMS YISNSGGNAH EDYGTSPFVY (487) (488) (489) GFTFSGYAMS YISNSGGNAH EDYGTSPFVY (487) (488) (489) GFTFSGYAMS (487) YISNSGGNTH (650) EDYGTSPFVY (489) GFTFSGYAMS (487) YISNSGGNTH (650) EDYGTSPFVY (489) GYTFTDYYMD (487) YIYPKNGGSS (646) KVVATDY (652) GYTFTDYYMD (487) YIYPKNGGSS (646) KVVATDY (652) GFTFSNYAMS (643) YISNGGGDTH (647) ENYGTSPFVY (653) GFTFSNYAMS (643) AYISNQGGDTH (651) ENYGTSPFVY (653) GFSFSSYDMS (644) TISGGGRYTY (648) NYYGFDY (654) Table 4 VL CDR1 (SEQ IDNO) CDR2 (SEQ IDNO) CDR3 (SEQ IDNO) RASES VDNYGISFMN (656) AASNQGS (691) QQSKDVPWT (492) KSSQSLLYSSNQKNY L(657) WASIRES (664) QQCDSYPWT (667) RASES VDNYGISFMN (656) AASNQGS (691) QQSKDVPWT (492) KASQDVGTAVA (658) WASTRHT (665) QQYSSYPWT (668) LASQTIGTWLA (659) AATSLAD (666) QQLYSIPWT (669) RASES VDNYGISFMN (660) AASNQGS (691) QQSKDVPWT (492) RASESVDQYGISFM N (661) WASIRES (664) QQCDSYPWT (667) RASES VDSYGISFM N (662) WASTRHT (665) QQYSSYPWT (668) RASESVDAYGISFM N (490) QQLYSIPWT (669) KSSQSLLYSSNQKN YLA (663) QQSDSYPWT (670) In some embodiments, the PD-1 pathway inhibitor is an antibody comprising one or more sequences in Tables 7-9 of WO2017011580A2. In some embodiments, the PD1 pathway inhibitor comprises an activatable PD-1 antibody that comprises: (i) an antibody or an antigen binding fragment thereof (AB) that comprises one or more sequences in Tables 7-9 of WO2017011580A2; (ii) a masking moiety (MM) that, when the activatable antibody is in an uncleaved state, inhibits the binding of the AB to PD-1; and (c) a cleavable moiety (CM) coupled to the AB, wherein the CM is a polypeptide that functions as a substrate for a protease; and optionally a first linking peptide and / or a second linking peptide. Any of the polypeptides described above can be combined with human immunoglobulin constant regions to result in fully human IgGs including IgGl, IgG2, IgG4 or mutated constant regions to result in human IgGs with altered functions such as IgGl N297A, IgGl N297Q, or IgG4 S228P. The polypeptides described above are not limited by the particular combinations and include any mask sequence matched with any substrate sequence matched with any VL sequence matched with any VH sequence. In addition to the substrate sequences any CM disclosed herein can be used. Anti-PD-Ll sequences In some embodiments the anti-PD-Ll, which may in certain aspects be configured as an activable antibody and in others aspects not be configured as an activatable antibody, comprises sequences shown below: Variable light chain region amino acid sequence: DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYYA STLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQDNGYPSTFGQGTKVEIK R (SEQ ID NO: 671). Variable light chain region amino acid sequence: DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYAA SSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQDNGYPSTFGGGTKVEIK R (SEQ ID NO: 672). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGQ SRPGFDYWGQGTLVTVSS (SEQ ID NO: 673). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGQ SWPGFDYWGQGTLVTVSS (SEQ ID NO: 674). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGQ SFPGFDYWGQGTLVTVSS (SEQ ID NO: 675). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAAF DYWGQGTLVTVSS (SEQ ID NO: 676). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAG YDYWGQGTLVTVSS (SEQ ID NO: 677). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIYSTGGATAYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSKGF DYWGQGTLVTVSS (SEQ ID NO: 678). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWKQGIVTVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTV (SEQ ID NO: 679). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRNGIVTVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 680). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS DIWKQGMVTVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGF DYWGQGTLVTVSS (SEQ ID NO: 681). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRQGLATAYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 682). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS EIVATGILTSYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFDY WGQGTLVTVSS (SEQ ID NO: 683). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIGRQGLITVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFDY WGQGTLVTVSS (SEQ ID NO: 684). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWYQGLVTVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 685). EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS DIWKQGFATADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 686). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWKQGIVTVYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 687). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRQGLATAYDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKSSAGFD YWGQGTLVTVSS (SEQ ID NO: 688). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRNGIVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAAF DYWGQGTLVTVSS (SEQ ID NO: 689). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRNGIVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAG YDYWGQGTLVTVSS (SEQ ID NO: 690). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWRNGIVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSKGF DYWGQGTLVTVSS (SEQ ID NO: 691). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWYQGLVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAA FDYWGQGTLVTVSS (SEQ ID NO: 692). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWYQGLVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSAG YDYWGQGTLVTVSS (SEQ ID NO: 693). Variable heavy chain region amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVS SIWYQGLVTVYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKWSKG FDYWGQGTLVTVSS (SEQ ID NO: 694). In some embodiments, anti-PD-Ll CDR sequences comprise the sequences listed 5 in the following tables. Table 5 VH CDR1 (SEQ ID NO) CDR2 (SEQ ID NO) CDR3 (SEQ ID NO) SYAMS (SEQ ID NO: 538) DITASGQRTTYADS (SEQ IDNO: 695) SKAIFDY (SEQ ID NO: 696) SINKDGHYTSYADS (SEQ IDNO: 697) NLDEFDY (SEQ ID NO: 698) SIMATGAGTLYADS (SEQ IDNO: 699) DGAGEDY (SEQ ID NO: 700) TITSSGAATYYADS (SEQ IDNO: 701) NYTGFDY (SEQ ID NO: 702) SIYSTGGATAYADS (SEQ ID NO: 703) SSAGFDY (SEQ ID NO: 704) SSIYSTGGATAYADS (SEQ IDNO: 705) SSAGOSRPGFDY (SEQ ID NO: 706) SSIWKQGIVTVYDS (SEQ ID NO: 707) SSAGQSWPGFDY (SEQ ID NO: 708) SSIWRNGIVTVYDS (SEQ ID NO: 709) SSAGQSFPGFDY (SEQ IDNO: 710) SDIWKQGMVTVYDS (SEQIDNO: 711) WSAAFDY (SEQ ID NO: 540) SSIWROGLATAYDS (SEQ IDNO: 712) WSAGYDY (SEQIDNO: 713) SEIVAT GILT SYDS (SEQ IDNO: 714) WSKGFDY (SEQIDNO: 715) SSIGRQGLITVYDS (SEQIDNO: 716) SSIWYQGLVTVYD (SEQIDNO: 717) SDIWKQGFATADS (SEQIDNO: 718) SSIWRNGIVTVYADS (SEQ ID NO: 539) SSIWYQGLVTVYADS (SEQIDNO: 719) Table 6 VL CDR1 (SEQ ID NO) CDR2 (SEQ ID NO) CDR3 (SEQID NO) RASQSISSYLN (SEQIDNO: 535) KASRLOS (SEQ ID NO: 720) RALKPVT (SEQIDNO: 721) AASSLQS (SEQ ID NO: 536) SYSTPNT (SEQ IDNO: 722) SASQLQS (SEQ ID NO: 723) ANSRPST (SEQ ID NO: 724) NASSLOS (SEQ ID NO: 725) YPYGPG (SEQ IDNO: 726) YASTLQS (SEQ ID NO: 727) DNGYPST (SEQ ID NO: 537) Any of the polypeptides described above can be combined with human immunoglobulin constant regions to result in fully human IgGs including IgGl, IgG2, IgG4 or mutated constant regions to result in human IgGs with altered functions such as IgGl N297A, IgGl N297Q, or IgG4 S228P. The polypeptides described above are not limited by the particular combinations and include any mask sequence matched with any substrate sequence matched with any VL sequence matched with any VH sequence. In addition to the substrate sequences any CM disclosed herein can be used. As a non-limiting example a spacer sequence and Mask can be combined with substrate and combined with human kappa constant domain to give SEQ ID NO: 496; or Mask can be combined with substrate and combined with human kappa constant domain to give SEQ ID NO: 728. Furthermore, a VH domain can be combined with human immunoglobulin heavy chain constant domains to give human IgGl (SEQ ID NO: 729), mutated human IgG4 S228P (SEQ ID NO: 485), mutated human IgGl N297A (SEQ ID NO: 730), or mutated human IgGl N297Q (SEQ ID NO: 731). Co-expression will yield an activatable antibody. Light chain sequence...

Claims

1. Use of a combination of an activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor for treating a subject in need thereof comprising administering to the subject the combination, wherein the ACC includes a first monomer construct and a second monomer construct, wherein:(a) the first monomer construct comprises a first peptide mask (PM1), a first mature cytokine protein (CP1), a first and a third cleavable moieties (CM1 and CM3), and a first dimerization domain (DD1), wherein the CM1 is positioned between the CP1 and the DD1 and the CM3 is positioned between the PM1 and the CP1, wherein the PM1 comprises a sequence that is at least 85% identical to SEQ ID NO: 292 and the CP1 is an interferon comprising a sequence that is at least 80% identical to SEQ ID NO: 1 or SEQ ID NO: 448; and(b) the second monomer construct comprises a second peptide mask (PM2), a second mature cytokine protein (CP2), a second and fourth cleavable moiety (CM2 and CM4), and a second dimerization domain (DD2), wherein the CM2 is positioned between the CP2 and the DD2 and the CM4 is positioned between the PM2 and the CP2;wherein the DD1 and the DD2 bind to each other thereby forming a dimer of the first monomer construct and the second monomer construct; wherein the first monomer and second monomer are the same.

2. The use of claim 1, wherein each of the CP1 and the CP2 comprises a sequence that is at least 80% identical to SEQ ID NO: 1.

3. The use of claim 1 or claim 2, wherein each of the CP1 and the CP2 comprises a sequence of SEQ ID NO: 1.

4. The use of any one of claims 1-3, wherein:(a) the PM1 and PM2 comprise a sequence that is at least 95% identical to SEQ ID NO: 292;2022360371   17 Jun 2026(b) the first monomer construct is characterized in that the CP1 and the DD1 are linked by a linking region of no more than 18 amino acids such that the linking region of no more than 18 amino acids includes the CM3; or(c) wherein the second monomer construct is characterized in that the CP2 and the DD2 are linked by a linking region of no more than 18 amino acids such that the linking region of no more than 18 amino acids includes the CM2.

5. The use of any one of claims 1-4, wherein the CM1, CM2, CM3, and / or the CM4 comprise a sequence selected from the group consisting of: LSGRSDNH (SEQ ID NO: 5), TGRGPSWV (SEQ ID NO: 6), PLTGRSGG (SEQ ID NO: 7), TARGPSFK (SEQ ID NO: 8), NTLSGRSENHSG (SEQ ID NO: 9), NTLSGRSGNHGS (SEQ ID NO: 10), TSTSGRSANPRG (SEQ ID NO: 11), TSGRSANP (SEQ ID NO: 12), VHMPLGFLGP (SEQ ID NO: 13), AVGLLAPP (SEQ ID NO: 14), AQNLLGMV (SEQ ID NO: 15), QNQALRMA (SEQ ID NO: 16), LAAPLGLL (SEQ ID NO: 17), STFPFGMF (SEQ ID NO: 18), ISSGLLSS (SEQ ID NO: 19), PAGLWLDP (SEQ ID NO: 20), VAGRSMRP (SEQ ID NO: 21), VVPEGRRS (SEQ ID NO: 22), ILPRSPAF (SEQ ID NO: 23), MVLGRSLL (SEQ ID NO: 24), QGRAITFI (SEQ ID NO: 25), SPRSIMLA (SEQ ID NO: 26), SMLRSMPL (SEQ ID NO: 27), ISSGLLSGRSDNH (SEQ ID NO: 28), AVGLLAPPGGLSGRSDNH (SEQ ID NO: 29), ISSGLLSSGGSGGSLSGRSDNH (SEQ ID NO: 30), LSGRSGNH (SEQ ID NO: 31), SGRSANPRG (SEQ ID NO: 32), LSGRSDDH (SEQ ID NO: 33), LSGRSDIH (SEQ ID NO: 34), LSGRSDQH (SEQ ID NO: 35), LSGRSDTH (SEQ ID NO: 36), LSGRSDYH (SEQ ID NO: 37), LSGRSDNP (SEQ ID NO: 38), LSGRSANP (SEQ ID NO: 39), LSGRSANI (SEQ ID NO: 40), LSGRSDNI (SEQ ID NO: 41), MIAPVAYR (SEQ ID NO: 42), RPSPMWAY (SEQ ID NO: 43), WATPRPMR (SEQ ID NO: 44), FRLLDWQW (SEQ ID NO: 45), ISSGL (SEQ ID NO: 46), ISSGLLS (SEQ ID NO: 47), ISSGLL (SEQ ID NO: 48), ISSGLLSGRSANPRG (SEQ ID NO: 49), AVGLLAPPTSGRSANPRG (SEQ ID NO: 50), AVGLLAPPSGRSANPRG (SEQ ID NO: 51), ISSGLLSGRSDDH (SEQ ID NO: 52), ISSGLLSGRSDIH (SEQ ID NO: 53), ISSGLLSGRSDQH (SEQ ID NO: 54), ISSGLLSGRSDTH (SEQ ID NO: 55), ISSGLLSGRSDYH (SEQ ID NO: 56), ISSGLLSGRSDNP (SEQ ID NO: 57), ISSGLLSGRSANP (SEQ ID NO: 58),2022360371   17 Jun 2026ISSGLLSGRSANI (SEQ ID NO: 59), AVGLLAPPGGLSGRSDDH (SEQ ID NO: 60), AVGLLAPPGGLSGRSDIH (SEQ ID NO: 61), AVGLLAPPGGLSGRSDQH (SEQ ID NO: 62), AVGLLAPPGGLSGRSDTH (SEQ ID NO: 63), AVGLLAPPGGLSGRSDYH (SEQ ID NO: 64), AVGLLAPPGGLSGRSDNP (SEQ ID NO: 65), AVGLLAPPGGLSGRSANP (SEQ ID NO: 66), AVGLLAPPGGLSGRSANI (SEQ ID NO: 67), ISSGLLSGRSDNI (SEQ ID NO: 68), AVGLLAPPGGLSGRSDNI (SEQ ID NO: 69), GLSGRSDNHGGAVGLLAPP (SEQ ID NO: 70), GLSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 71), LSGRSDNHGGVHMPLGFLGP (SEQ ID NO: 72), ISSGLSS (SEQ ID NO: 73), PVGYTSSL (SEQ ID NO: 74), DWLYWPGI (SEQ ID NO: 75), LKAAPRWA (SEQ ID NO: 76), GPSHLVLT (SEQ ID NO: 77), LPGGLSPW (SEQ ID NO: 78), MGLFSEAG (SEQ ID NO: 79), SPLPLRVP (SEQ ID NO: 80), RMHLRSLG (SEQ ID NO: 81), LLAPSHRA (SEQ ID NO: 82), GPRSFGL (SEQ ID NO: 83), GPRSFG (SEQ ID NO: 84), SARGPSRW (SEQ ID NO: 85), GGWHTGRN (SEQ ID NO: 86), HTGRSGAL (SEQ ID NO: 87), AARGPAIH (SEQ ID NO: 88), RGPAFNPM (SEQ ID NO: 89), SSRGPAYL (SEQ ID NO: 90), RGPATPIM (SEQ ID NO: 91), RGPA (SEQ ID NO: 92), GGQPSGMWGW (SEQ ID NO: 93), FPRPLGITGL (SEQ ID NO: 94), SPLTGRSG (SEQ ID NO: 95), SAGFSLPA (SEQ ID NO: 96), LAPLGLQRR (SEQ ID NO: 97), SGGPLGVR (SEQ ID NO: 98), PLGL (SEQ ID NO: 99), and SGRSDNI (SEQ ID NO: 100).

6. The use according to any one of claims 1-5, wherein the CM1, CM2, CM3, and / or CM4 comprises an amino acid sequence selected from SEQ ID NOs: 41, 68, and 100.

7. The use according to any one of claims 1-6, wherein:(a) the CM1, the CM2, and the CM3 comprise substrates for the same protease;(b) the CP1 and the CM1 directly abut each other in the first monomer construct; and(c) the CM1 and the DD1 directly abut each other in the first monomer construct;.(d) the CP2 and the CM2 directly abut each other in the second monomer construct; and / or(e) the CM2 and the DD2 directly abut each other in the second monomer construct.2022360371   17 Jun 20268. The use according to any one of claims 1-7:(a) wherein:(i) the first monomer construct comprises in a N- to C- terminal direction, the PM1, the CM3, the CP1, the CM1, and the DD1; or(ii) the first polypeptide comprises in a C- to N-terminal direction, the PM1, the CM3, the CP1, the CM1, and the DD1.

9. The use according to any one of claims 1-8, wherein:(a) the first monomer construct comprises, in an N- to C- terminal direction, the PM1, the CM3, the CP1, the CM1, and the DD1;(i) the CM1 and the DD1 directly abut each other,(ii) the CM1 comprises a sequence that is at least 85% identical to SEQ ID NO: 41, and(iii) the CP1 comprises a sequence that is at least 85% identical to SEQ ID NO: 1;(b) the DD1 and DD2 are a pair of human IgG4 Fc domains;(c) the DD1 and the DD2 covalently bind to each other via at least one disulfide bond, thereby forming a homodimer of the first monomer construct and the second monomer construct; and(d) the ACC is characterized by having a reduced level of interferon activity as compared to a corresponding wildtype interferon or a corresponding pegylated interferon.

10. The use according to any one of claims 1-9, wherein the DD1 and the DD2 are selected from the group consisting of: human IgG1 Fc domains, human IgG2 Fc domains, human IgG3 Fc domains, or human IgG4 Fc domains, or wherein the DD1 and DD2 comprise SEQ ID NO: 3.

11. Use of a combination of an activatable cytokine construct (ACC) and a PD-1 / PD-L1 pathway inhibitor for treatment of cancer in a subject, wherein the ACC comprises a first2022360371   17 Jun 2026monomer construct and a second monomer construct, each of which comprises SEQ ID NO: 290 or SEQ ID NO: 290 without N-terminal spacer sequence QSGQ (SEQ ID NO: 480), wherein the first monomer construct and the second monomer construct are the same; and b) a PD-1 pathway inhibitor or a PD-L1 pathway inhibitor.

12. The use according to claim 11, wherein each of the first and second monomer constructs comprises SEQ ID NO: 290.

13. The use according to any one of claims 1-12, wherein the PD1 / PD-L1 pathway inhibitor comprises nivolumab, pembrolizumab, tislelizumab, spartalizumab, camrelizumab, cetrelimab, Balstilimab, Dostarlimab, Prolgolimab, Sasanlimab, zimberelimab, Atezolizumab, Avelumab, Durvalumab, adebrelimab, Lodapolimab, Envafolimab, Cosibelimab, budigalimab, ezabenlimab, finotonlimab, geptanolimab, lodapolimab, penpulimab, pimivalimab, pucotenlimab, serplulimab. Sintilimab, toripalimab, zeluvalimab, iparomlimab, nofazinlimab, rulonilimab, garivulimab, manelimab, opucolimab, sudubrilimab, sugemalimab, socazolimab, or tagitanlimab.

14. The use according to any one of claims 1-13, wherein the PD1 / PD-L1 pathway inhibitor comprises pembrolizumab.

15. The use according to any one of claims 1-14, wherein the ACC comprises a Linking Region comprising 7 to 12 amino acids.

16. The use according to any of claims 1-15, wherein the first monomer construct and the second monomer construct each comprise, in an N- to C- terminal direction, SEQ ID NO: 292; an optional flexible linker of zero to 10 amino acids; a CM comprising an amino acid sequence selected from the group consisting of SEQ ID NO: 41, SEQ ID NO: 68, and SEQ ID NO: 100; an optional flexible linker of zero to 10 amino acids; SEQ ID NO:1; a second CM comprising an amino acid sequence selected from the group consisting of SEQ ID NO: 41, SEQ ID NO: 68, and SEQ ID NO: 100; and a dimerization domain.

17. The use according to any one of claims 1-16, wherein the first monomer construct and the second monomer construct comprise the amino acid sequence of SEQ ID NO: 290, and wherein the PD-1 / PD-L1 pathway inhibitor is pembrolizumab.2022360371   17 Jun 202618. The use according to any one of claims 1-17, wherein the subject has been identified or diagnosed as having a cancer.

19. The use according to any one of claims 1-18, wherein the subject has melanoma, renal cell carcinoma, or a head and neck tumor.

20. A method of treating a subject having a cancer comprising sequentially administering to the subject: a) an activatable cytokine construct (ACC) comprising a first monomer construct and a second monomer construct, each of which comprises SEQ ID NO: 290 or SEQ ID NO: 290 without N-terminal spacer sequence QSGQ (SEQ ID NO: 480), wherein the first monomer construct and the second monomer construct are the same; and b) a PD-1 pathway inhibitor or a PD-L1 pathway inhibitor.

21. A method of treating a subject having a cancer comprising sequentially administering to the subject: a) an activatable cytokine construct (ACC) comprising a first monomer construct and a second monomer construct, wherein each of the first and second monomer constructs comprises SEQ ID NO: 290; and b) a PD-1 pathway inhibitor or a PD-L1 pathway inhibitor.

22. The method of claim 20 or claim 21, wherein b) is selected from the group consisting of nivolumab, pembrolizumab, tislelizumab, spartalizumab, camrelizumab, cetrelimab, cemiplimab, Balstilimab, Dostarlimab, Prolgolimab, Sasanlimab, zimberelimab, Atezolizumab, Avelumab, Durvalumab, adebrelimab, Lodapolimab, Envafolimab, Cosibelimab, budigalimab, ezabenlimab, finotonlimab, geptanolimab, lodapolimab, penpulimab, pimivalimab, pucotenlimab, serplulimab, Sintilimab, toripalimab, zeluvalimab, iparomlimab, nofazinlimab, rulonilimab, garivulimab, manelimab, opucolimab, pacmilimab (CX-072), sudubrilimab, sugemalimab, socazolimab, and tagitanlimab.

23. The method of any one of claims 20-22, wherein b) is pembrolizumab.

24. The method of any one of claims 20-23, wherein the subject has melanoma, renal cellcarcinoma, or a head and neck tumor.

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