Fc-CELL COMPLEX AND METHOD FOR PRODUCING THE SAME

Abstract

This Fc-cell complex comprises a cell and an antibody Fc region bound to a surface of the cell. In the antibody Fc region, two Fc constituent polypeptides are disulfide-bonded to each other. The antibody Fc region is chemically bonded to the cell surface via a linker introduced into a functional group in a side chain of a specific amino acid residue present at one or more positions of the two antibody Fc constituent polypeptides.

Description

Fc-Cell Complex and Method for Producing the Same The present invention relates to an Fc-cell complex (also referred to as an Fc-cell conjugate) and a method for producing the same. Techniques for binding an antibody to the cell surface in order to confer a function on the cell are known. For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2016-523237) discloses a technique for producing a protein-cell conjugate by binding a protein such as an antibody to the cell surface by reacting a sulfhydryl group on the cell surface with a side-chain amino group of the protein using a bifunctional crosslinking agent. However, in this technique, since the crosslinking agent randomly reacts with the side-chain amino groups of the protein such as the antibody, it is difficult to control the introduction ratio of the protein to the cell, and there is also a problem that the binding position of the linker in the protein becomes non-uniform. Japanese Unexamined Patent Application Publication No. 2016-523237 International Publication No. 2018 / 199337 International Publication No. 2019 / 240287 International Publication No. 2019 / 240288 International Publication No. 2020 / 090979 An object of the present invention is to provide a technique capable of efficiently introducing an Fc region into a cell by controlling the binding position of a linker in the Fc region and the introduction ratio of the Fc region into the cell in producing an Fc-cell complex in which an antibody-like molecule such as an antibody variable region or a functional protein-Fc fusion protein is introduced onto the cell surface via the Fc region of the antibody. Another object of the present invention is to provide an Fc-cell complex in which the binding position of the linker in the Fc region and the introduction ratio of the Fc region into the cell are controlled. The present applicant has reported a technique for preparing an antibody having a functional substance such as a drug in a site-selective manner by a chemical synthesis method using a predetermined compound containing an affinity peptide (Patent Documents 2 to 5). In this technique, linkers are introduced into both of the two heavy-chain constant region-derived polypeptides constituting the Fc region. However, the present inventors considered that it is more preferable to introduce a linker into only one of the two heavy-chain constant region-derived polypeptides constituting the Fc region for the above object. Therefore, with the aim of developing a technique that enables easy chemical modification of only one of the two heavy chain constant region-derived polypeptides constituting the Fc region, intensive studies were conducted to improve the above technique. As a result, it was found that by using an affinity substance having an affinity for the Fc region, preferably an affinity substance containing first and second affinity moieties, and a compound containing a reactive group for the Fc region, only one of the heavy chain constant region-derived polypeptides in the constituent unit of the Fc region can be easily chemically modified. By using this technique, an Fc-cell complex in which the Fc region is bound to the cell surface via one of its polypeptides can be obtained, and it was found that an antibody or a functional protein can be introduced onto the cell surface via the Fc region when the Fc region contains an antibody variable region or a functional protein. According to the above technique, an affinity substance having an affinity for the Fc region, preferably an affinity substance (A) containing first and second affinity moieties, and a compound containing a reactive group (R) for the Fc region can associate with the Fc region via the affinity substance (A). Next, via the reactive group (R), it can specifically react with the side chain of a specific amino acid residue in one of the heavy chain constant region-derived polypeptides in the constituent unit of the Fc region to generate an affinity substance-modified Fc region in which only one of the two heavy chain constant region-derived polypeptides constituting the Fc is modified (Figure 1) (WO2023 / 234416). Although it is not desired that the present invention be restricted by theory, the modification mechanism of only one of the heavy chain constant region-derived polypeptides in the constituent unit of the Fc region is as follows. The affinity substance (A) contained in the compound can stably associate with the two heavy chain constant region-derived polypeptides constituting the Fc region. Therefore, the reactive group (R) contained in the compound can modify only one of the heavy chain constant region-derived polypeptides (Figure 1). At this time, since the other heavy chain constant region-derived polypeptide has an associated affinity moiety and steric hindrance occurs, the reactive group (R) of other molecules of the same compound cannot react with the side chain amino acids of the other heavy chain constant region-derived polypeptide, so only one of the heavy chain constant region-derived polypeptides can be modified (Figure 1). By using the Fc region in which only one of the polypeptides derived from one heavy chain constant region obtained in this way is modified, and binding it to the cell surface via a linker, the Fc region is linked to the cell surface via a linker introduced into the functional group in the side chain of a specific amino acid residue present at one or more positions of one of the two polypeptides derived from the heavy chain constant region contained therein. An Fc-cell complex can be obtained. When this Fc region contains an antibody variable region or a functional protein, antibody-like molecules such as antibodies and functional protein-Fc fusion proteins are linked to the cell surface via a linker introduced into the functional group in the side chain of a specific amino acid residue present at one or more positions of one of the two polypeptides derived from the heavy chain constant region contained in the Fc region. An antibody-like molecule-cell complex can be obtained. That is, the present invention has the following aspects. [1] An Fc-cell complex comprising a cell and an antibody Fc region bound to the surface of the cell, The antibody Fc region is a dimer of two Fc constituent polypeptides linked by a disulfide bond, The antibody Fc region is chemically bound to the cell surface via a linker introduced into the functional group in the side chain of a specific amino acid residue present at one or more positions of one of the two antibody Fc constituent polypeptides, The Fc-cell complex. [2] The specific amino acid residue is any one or more of 14 amino acid residues consisting of asparagine, glutamine, methionine, proline, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, arginine, histidine, and lysine. The Fc-cell complex according to [1]. [3] The specific amino acid residue is a lysine residue. The Fc-cell complex according to [1]. [4] The lysine residue is any one or more of the lysine residues at positions 246, 248, 274, 288, 290, 317, 320, 322, 360, 414, and 439. The Fc-cell complex according to [3]. [5] The Fc region of the antibody has a functional substance introduced via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions of the other of the two Fc constituent polypeptides, the Fc-cell complex according to any one of [1] to [4]. [6] The Fc-cell complex according to [5], wherein the functional substance is a drug, a labeling substance, an affinity substance, a transport substance, or a stabilizer. [7] The Fc-cell complex according to any one of [1] to [6], wherein the Fc region of the antibody contains an antibody variable region. [8] The Fc-cell complex according to any one of [1] to [6], wherein the Fc region of the antibody contains a fusion protein of an antibody Fc constituent polypeptide and a functional polypeptide. [9] The Fc region of the antibody is introduced onto the cell surface by the reaction of a bioorthogonal functional group introduced via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions of one of the two Fc constituent polypeptides with a group that is present on the cell surface or reacts with the introduced bioorthogonal functional group, the Fc-cell complex according to any one of [1] to [8].

[10] A method for producing a cell-Fc region complex, (I) A step of preparing an antibody Fc region in which two antibody Fc constituent polypeptides are disulfide-bonded; (II) Reacting the antibody Fc region with a compound represented by the following formula (Ia) or formula (Ib) to form an Fc-compound (Ia) complex or an Fc-compound (Ib) complex; [In the formula, R represents a reactive group for the Fc region, L １ represents a first linker, L ２ represents a second linker, CLE(B) represents a cleavable moiety capable of generating a bioorthogonal functional group on the reactive group side by cleavage, and A represents an affinity substance containing an affinity peptide. 〔In the formula, R represents the reactive group, and L ５ represents the fifth linker, and L ６ represents the sixth linker, B represents a group containing a bioorthogonal functional group, CLE represents a cleavable moiety, and A represents the affinity substance.〕 (III) A step of cleaving the Fc-compound (Ia) complex or the Fc-compound (Ib) complex with the cleavable moiety to form an Fc region that does not contain the affinity substance and into which a bioorthogonal functional group is introduced; (IV) A step of preparing cells having a functional group that reacts with a bioorthogonal functional group on the surface; (V) A step of introducing the Fc region onto the cell surface by reacting the Fc region into which the bioorthogonal functional group is introduced with the cells, by reacting the bioorthogonal functional group of the Fc region with the functional group of the cells that reacts with the bioorthogonal functional group of the cells; A method comprising:

[11] The compound (Ia) is represented by the following formula (Ia-1): 〔In the formula, X represents a leaving group, and W １ , W ２ and W ３ each independently represents an oxygen atom or a sulfur atom, L ３ represents the third linker, L ４ represents the fourth linker, S represents a sulfur atom, and A represents the affinity substance.〕 The method for producing a cell-Fc region complex according to

[10] .

[12] The compound (Ib) is represented by the following formula (Ib-1): 〔In the formula, X represents a leaving group, and W １ , W ２ and W ３ each independently represents an oxygen atom or a sulfur atom, L ７ represents the seventh linker, L ８represents the 8th linker, B represents a group containing a bioorthogonal functional group, V represents an oxygen atom or a sulfur atom, and A represents the affinity substance. The method for producing the cell-Fc region complex according to

[10] , which is represented by [ ].

[13] A is AP1-L Ａ -AP2 (wherein AP1 represents a first affinity peptide having an affinity for the constant region in the heavy chain of the antibody, AP2 represents a second affinity peptide having an affinity for the constant region in the heavy chain of the antibody, and L Ａ represents a linker), the method according to any one of

[10] to

[12] .

[14] The method for producing the cell-Fc region complex according to any one of

[10] to

[13] , wherein the bioorthogonal functional group is an azide group, an alkyne residue, a tetrazine residue, an alkene residue, a thiol group, a maleimide residue, a furan residue, or a halocarbonyl residue.

[15] The method for producing the cell-Fc region complex according to any one of

[10] to

[14] , wherein the cell-Fc region complex is the Fc-cell complex according to any one of [1] to [9].

[16] The method for producing the cell-Fc region complex according to any one of

[10] to

[14] , wherein the cell-Fc region complex is the Fc-cell complex according to [5], and the method includes a step of introducing a functional substance into a functional group in the side chain of a specific amino acid residue present at one or more positions of the other of the two Fc constituent polypeptides in the antibody Fc region. According to the present invention, only one of the constituent units (two heavy chain constant region-derived polypeptides) of the Fc region of an antibody can be easily modified. Further, according to the present invention, it is possible to easily modify only one of the heavy chain constant region-derived polypeptides in the constituent unit of the antibody Fc region and provide a site-selectively modified Fc region. By using a modified Fc in which a bioorthogonal functional group is introduced only into one of the constituent units of the Fc region obtained by such a site-selective modification technique, the Fc region can be site-selectively introduced into the cell surface only through one of its constituent units to obtain an Fc-cell complex. Thereby, the orientation of an antibody or a fusion protein containing the Fc region presented on the cell surface can be controlled, and the effect can be exerted in a small amount without impairing the activity of the antibody or the fusion protein. Figure showing the presumed principle of a method for modifying an affinity substance only to one of the two heavy chain constant region-derived polypeptides constituting Fc. Figure showing the reaction using compound (Ia) (steps (II) and (III)). r indicates the modification rate to the immunoglobulin unit (hereinafter the same). Figure showing the reaction using compound (Ia-1) (steps (II) and (III)). Figure showing the reaction using compound (Ib) (steps (II) and (III)). T 1 represents a monovalent group generated by cleavage (hereinafter, T ２The same applies to others). Diagram showing the reaction using compound (Ib-1) (Steps (II) and (III)). Diagram showing the reaction using compound (Ia) (Steps (II) (Reactions 1, 2) and (III) (Reaction 3)) (introduction of bioorthogonal functional groups into each of the two heavy chain constant region-derived polypeptides constituting Fc). Diagram showing the reaction using compound (Ib) (Steps (II) (Reactions 1, 2) and (III) (Reaction 3)) (introduction of bioorthogonal functional groups into each of the two heavy chain constant region-derived polypeptides constituting Fc). Diagram showing the proportion of T-4 antibody-positive cells after adding the T-4 antibody to cells at each concentration and reacting for 1 hour or 24 hours in the presence or absence of DBCO. The results of flow cytometry are represented graphically. Diagram showing the amount of fluorescence derived from T-5 (left) or HER2-biotin / StAv-AF488 (right) bound to cells immediately after addition or 48 hours after addition, after adding the T-5 antibody to cells (left) and further adding HER2-biotin / StAv-AF488 (right). Micrograph showing AF488-derived fluorescence in HEL cells / HER2-Fc / StAv-AF488 or HEL cells / DBCO-modified T-5 / HER2-Fc / StAv-AF488. Graphs showing Cy5-derived fluorescence (top), AF488-derived fluorescence (middle) 0 hours, 24 hours, 48 hours, 72 hours or 96 hours after adding the T-5 antibody to cells (with or without DBCO modification) and further adding HER2-biotin / StAv-AF488, and a graph showing the HER2 binding ability per antibody 0 hours, 24 hours, 48 hours later (bottom). The results of flow cytometry are represented graphically. Diagram showing the amount of fluorescence derived from T-5, T-8 or T-9 (left) or HER2-biotin / StAv-AF488 (right) bound to cells immediately after addition or 48 hours after addition, after adding the T-5 antibody, T-8 antibody or T-9 antibody to cells at 0.3 μM or 1 μM (left) and further adding HER2-biotin / StAv-AF488 (right).Graph showing the results of calculating the HER2 binding ability per antibody based on the amount of fluorescence derived from T-5, T-8, or T-9 and the fluorescence derived from HER2-biotin / StAv-AF488 bound to cells immediately after addition or 24 hours after addition, where T-5 antibody, T-8 antibody, or T-9 antibody was added to the cells at 0.3 μM or 1 μM, and then HER2-biotin / StAv-AF488 was added. Diagram showing the percentage of T-4 antibody-positive cells after adding the T-4 antibody to the cells at each concentration and reacting for 1 hour or 24 hours in the presence or absence of DBCO. On the left is Gated (%), and on the right is MFI (mean fluorescence intensity: excluding background). The results of flow cytometry are represented graphically. Diagram showing the expression of each polypeptide in each transformant (electrophoresis photograph). Diagram showing the luminescence intensity from the surface antibody of the antibody-NK cell conjugate (ACC-1). NK cells are shown as a control. Graph showing the luminescence intensity from the surface antibody of the antibody-NK cell conjugates (ACC-3, ACC-4, and ACC-5). NK cells are shown as a control. Diagram showing the cytotoxicity evaluation of ACC-1, ACC-2, ACC-3, ACC-4, and ACC-5 (ratio of NK cells (control) or antibody-NK cell conjugate to SK-BR-3 = 6:1). Graph showing the cytotoxicity evaluation of ACC-3, ACC-4, ACC-5, and ACC-6 (effector:target ratio = 6:1). NK cells are shown as a control. Diagram showing the HER2 binding ability of ACC-5 and ACC-6. NK cells are shown as a control. <Fc-cell complex> The Fc-cell complex of the present invention comprises a cell and an Fc region bound to the surface of the cell. The Fc region is a disulfide-bonded product of two Fc region constituent units (i.e., polypeptides derived from the heavy chain constant region). The Fc region is chemically bound to the cell surface via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions, preferably one position, of one of the two Fc region constituent units. <Cell> The cell type and origin are not particularly limited and may be either eukaryotic cells or prokaryotic cells. Examples of eukaryotic cells include animal cells, plant cells, yeast cells, fungal cells, etc., and examples of prokaryotic cells include bacterial cells, but are not limited thereto. The cells are preferably eukaryotic cells, such as mammalian cells, and typically include human cells, mouse cells, rat cells, etc., and are preferably human cells. The cells may be somatic cells or germ cells. Examples of somatic cells include, but are not limited to, blood cells, immune cells, vascular cells, skeletal muscle cells, cardiomyocytes, nerve cells, retinal cells, hepatocytes, gastrointestinal cells, fibroblasts, ovarian cells, testicular cells, etc. Examples of germ cells include sperm cells and egg cells. The cells may also be stem cells. Stem cells include, for example, pluripotent and multipotent stem cells, and include induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), etc. The cells may be cells of the immune system. Examples of cells of the immune system include B cells, T cells, natural killer (NK) cells, etc. T cells include naive T (TN) cells, effector T cells (TEFF), memory T cells and their subtypes, such as stem cell memory T (TSCM), central memory T (TCM), effector memory T (TEM) or terminally differentiated effector memory T cells, tumor-infiltrating lymphocytes (TIL), immature T cells, mature T cells, helper T cells, cytotoxic T cells, mucosal-associated invariant T (MAIT) cells, natural and adaptive regulatory T (Treg) cells, helper T cells, such as TH1 cells, TH2 cells, TH3 cells, TH17 cells, TH9 cells, TH22 cells, follicular helper T cells, alpha / beta T cells, as well as delta / gamma T cells. The cells may be monocytes, granulocytes, bone marrow cells, macrophages, neutrophils, dendritic cells, mast cells, eosinophils and / or basophils. The cells may contain one or more types of nucleic acids introduced by genetic manipulation, and thereby may be cells that express recombinant products of the introduced nucleic acids, etc. The cells may be immortalized cells or primary cells. The immortalized cells can be obtained, for example, from a cell bank or the like. When the cells are primary cells isolated from a subject, the sample from which the cells are isolated includes, for example, whole blood, peripheral blood mononuclear cells (PBMC), leukocytes, bone marrow, thymus, tissue biopsy, tumor, leukemia, lymphoma, lymph node, gut-associated lymphoid tissue, mucosa-associated lymphoid tissue, spleen, other lymphoid tissues, liver, lung, stomach, intestine, colon, kidney, pancreas, breast, bone, prostate, neck, testis, ovary, tonsil or other organs, and / or cells derived therefrom. <Fc region> The antibody Fc region is formed by two Fc region constituent units (i.e., polypeptides derived from the heavy chain constant region) disulfide-bonded to each other. Here, the Fc region constituent unit is a polypeptide containing the hinge region, CH2 region, and CH3 region of the heavy chain constant region. The disulfide bond is formed by the reaction of the thiol groups of cysteine residues in the respective hinge regions of the two antibody Fc region constituent units. The antibody Fc region can be obtained, for example, by papain digestion of immunoglobulin by a known method. The Fc region may further include an antibody variable region, for example, the F(ab’) 2 region. That is, the Fc-cell complex of the present invention may be an antibody-cell conjugate in which an antibody containing an F(ab’) 2 region and an Fc region, i.e., an immunoglobulin, is bound to the cell surface via a linker introduced into the side chain functional groups of specific amino acid residues present in one of its heavy chain constant regions, preferably the CH2 region and the CH3 region. The origin of the antibody containing Fc and Fc is not particularly limited, and it may be derived from animals such as mammals, birds (e.g., chickens), etc. Preferably, the immunoglobulin unit is derived from a mammal. Such mammals include, for example, primates (e.g., humans, monkeys, chimpanzees), rodents (e.g., mice, rats, guinea pigs, hamsters, rabbits), pets (e.g., dogs, cats), livestock (e.g., cows, pigs, goats), draft animals (e.g., horses, sheep), and are preferably primates or rodents, more preferably humans. The type of antibody may be a polyclonal antibody or a monoclonal antibody. The antibody may also be a bivalent antibody (e.g., IgG, IgD, IgE), or an antibody with a valency of 4 or more (e.g., IgA antibody, IgM antibody). Preferably, the antibody is a monoclonal antibody. Examples of monoclonal antibodies include chimeric antibodies, humanized antibodies, human antibodies, antibodies with a predetermined sugar chain added (e.g., antibodies modified to have a sugar chain binding consensus sequence such as an N-type sugar chain binding consensus sequence), bispecific antibodies, Fc region proteins, Fc fusion proteins, and disulfide bond-reduced antibodies. Examples of the isotype of monoclonal antibodies include IgG (e.g., IgG1, IgG2, IgG3, IgG4), IgM, IgA, IgD, IgE, and IgY. When the Fc-cell conjugate is an antibody-cell conjugate, any antigen can be used as the antigen of the antibody. For example, such antigens include proteins [including oligopeptides and polypeptides. It may be a protein modified with a biomolecule such as a sugar (e.g., glycoprotein)], sugar chains, nucleic acids, and low molecular weight compounds. Preferably, the antibody may be an antibody using a protein as an antigen. Examples of proteins include cell membrane receptors, cell membrane proteins other than cell membrane receptors (e.g., extracellular matrix proteins), ligands, and soluble receptors. Specific examples of monoclonal antibodies include certain chimeric antibodies (e.g., rituximab, basiliximab, infliximab, cetuximab, siltuximab, dinutuximab, ortuxizumab), certain humanized antibodies (e.g., daclizumab, palivizumab, trastuzumab, alemtuzumab, omalizumab, efalizumab, bevacizumab, natalizumab (IgG4), tocilizumab, eculizumab (IgG2), mogamulizumab, pertuzumab, obinutuzumab, vedolizumab, pemprolizumab (IgG4), mepolizumab, elotuzumab, daratumumab, ikesekiizumab (IgG4), reslizumab (IgG4), atezolizumab), and certain human antibodies (e.g., adalimumab (IgG1), panitumumab, golimumab, ustekinumab, canakinumab, ofatumumab, denosumab (IgG2), ipilimumab, belimumab, lirilumab, ramucirumab, nivolumab, dupilumab (IgG4), secukinumab, evolocumab (IgG2), alirocumab, nesvacumab, brodalumab (IgG2), orlaratumumab) (when not referring to the IgG subtype, it indicates IgG1). In other embodiments, the Fc region may further comprise a functional polypeptide. That is, a fusion protein of the Fc region and the functional polypeptide may be an Fc fusion protein - cell conjugate bound to the cell surface via a linker introduced into the side chain functional groups of specific amino acid residues present in one of the heavy chain constant regions constituting the Fc region, preferably the CH2 region and the CH3 region. In this case, the Fc fusion protein may be a dimer of functional polypeptide - Fc constituent polypeptide (heavy chain constant region polypeptide) fusion proteins, or a dimer of a functional polypeptide - Fc constituent polypeptide fusion protein and an Fc constituent polypeptide. In the latter case, either of the two Fc constituent polypeptides may bind to the cell. The functional polypeptide is not particularly limited, and examples include enzymes, fluorescent proteins, growth factors, hormones, cytokines, blood proteins, enzymes, antigens, antibodies, transcription factors, receptors, or partial peptides thereof. Here, examples of the enzyme include lipase, protease, steroid synthase, kinase, phosphatase, xylanase, esterase, methylase, demethylase, oxidase, reductase, cellulase, aromatase, collagenase, transglutaminase, glycosidase, and chitinase. Examples of the growth factor include epidermal growth factor (EGF), insulin-like growth factor (IGF), transforming growth factor (TGF), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), platelet-derived growth factor (PDGF), erythropoietin (EPO), thrombopoietin (TPO), fibroblast growth factor (FGF), and hepatocyte growth factor (HGF). Examples of the cytokine include interleukin, interferon (IFNα, IFNβ, IFNγ), and tumor necrosis factor (TNF). Examples of the blood protein include thrombin, serum albumin, factor VII, factor VIII, factor IX, factor X, and tissue plasminogen activator. Such a fusion protein can be obtained by ligating a polynucleotide encoding Fc and a polynucleotide encoding a functional polypeptide in-frame, expressing the resulting construct in a host cell or the like, and purifying the expressed product. The antibody Fc region is chemically bound to the cell surface via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions, preferably one position, of one of the two antibody Fc region-constituting polypeptides. Here, the specific amino acid residue can be selected from any one or two or more (e.g., 2, 3, 4) of 14 amino acid residues consisting of asparagine, glutamine, methionine, proline, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, arginine, histidine, and lysine present in the Fc region, preferably the CH2 domain. As such specific amino acid residues, more preferably, lysine residues, tyrosine residues, serine residues, and threonine residues may be mentioned. For example, in human IgG such as human IgG1, since the following amino acid residues present in the heavy chain constant region can be exposed on the antibody surface, these amino acid residues can be used for the introduction of specific cleavage sites. Exposed lysine residue CH2 domain (e.g., positions 246, 248, 274, 288, 290, 317, 320, 322) CH3 domain (e.g., positions 360, 414, 439) Exposed tyrosine residue CH2 domain (e.g., positions 278, 296, 300) CH3 domain (e.g., position 436) Exposed serine residue CH2 domain (e.g., positions 254, 267, 298) CH3 domain (e.g., positions 400, 415, 440) Exposed threonine residue CH2 domain (e.g., positions 256, 289) CH3 domain (e.g., positions 335, 359) Regarding the positions of amino acid residues in the antibody and the positions of the constant regions of the heavy chain (e.g., CH2 domain), follow EU numbering (see http: / / www.imgt.org / IMGTScientificChart / Numbering / Hu_IGHGnumber.html). For example, when targeting human IgG, the lysine residue at position 246 corresponds to the 16th amino acid residue in the CH2 region of human IgG, the lysine residue at position 248 corresponds to the 18th amino acid residue in the CH2 region of human IgG, the lysine residue at position 288 corresponds to the 58th amino acid residue in the CH2 region of human IgG, the lysine residue at position 290 corresponds to the 60th amino acid residue in the CH2 region of human IgG, and the lysine residue at position 317 corresponds to the 87th amino acid residue in the CH2 region of human IgG. The notation at positions 246 / 248 indicates that the lysine residue at position 246 or 248 is the target. The notation at positions 288 / 290 indicates that the lysine residue at position 288 or 290 is the target (see, for example, International Publication Nos. WO 2016 / 186206, WO 2018 / 199337, WO 2019 / 240287, WO 2019 / 240288, WO 2020 / 009165, and WO 2020 / 090979). Preferably, specific amino acid residues in the constant region of the heavy chain that are site-specifically modified can site-specifically modify lysine residues (e.g., lysine residues at positions 246 / 248 or 288 / 290). The linker introduced into the side chain of a specific amino acid residue of one polypeptide constituting the Fc region is chemically bonded, on the one hand, to the positions of functional groups such as amino groups and carboxyl groups possessed by proteins and sugar chains present on the cell surface. The length and structure of the linker are not particularly limited as long as they do not inhibit the functions of the cell, antibody, or the fusion protein, and those skilled in the art can select any length and structure. Depending on the type of linker compound used for preparing the Fc-cell complex, examples include divalent groups as follows. The divalent group is a divalent linear hydrocarbon group, a divalent cyclic hydrocarbon group, a divalent heterocyclic group, -C(=O)-, -C(=S)-, -NR １ -, -C(=O)-NR １ -, -NR １ -C(=O)-, -C(=S)-NR １ -, -NR １ -C(=S)-, -O-, -S-, -(O-R ２ ). ｎ-, and -(S-R ２ ) ｍ - is a group selected from the group consisting of 1 group, or a group having a main chain structure containing 2 or more of these groups. R １ represents a hydrogen atom or a substituent described later. R ２ represents a divalent linear hydrocarbon group, a divalent cyclic hydrocarbon group, or a divalent heterocyclic group. n and m are each an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 6, even more preferably an integer of 1 to 5, and particularly preferably an integer of 1 to 3. The divalent linear hydrocarbon group is linear alkylene, linear alkenylene, or linear alkynylene. The linear alkylene is a linear alkylene having 1 to 6 carbon atoms, and a linear alkylene having 1 to 4 carbon atoms is preferred. Examples of the linear alkylene include methylene, ethylene, n-propylene, n-butylene, n-pentylene, and n-hexylene. The linear alkenylene is a linear alkenylene having 2 to 6 carbon atoms, and a linear alkenylene having 2 to 4 carbon atoms is preferred. Examples of the linear alkenylene include ethylenylene, n-propynylene, n-butenylene, n-pentenylene, and n-hexenylene. The linear alkynylene is a linear alkynylene having 2 to 6 carbon atoms, and a linear alkynylene having 2 to 4 carbon atoms is preferred. Examples of the linear alkynylene include ethynylene, n-propynylene, n-butynylene, n-pentynylene, and n-hexynylene. As the divalent linear hydrocarbon group, linear alkylene is preferred. The divalent cyclic hydrocarbon group is arylene or a divalent non-aromatic cyclic hydrocarbon group. As arylene, arylene having 6 to 14 carbon atoms is preferred, arylene having 6 to 10 carbon atoms is more preferred, and arylene having 6 carbon atoms is particularly preferred. Examples of arylene include phenylene, naphthylene, and anthracenylene. The divalent non-aromatic cyclic hydrocarbon group is preferably a divalent non-aromatic cyclic hydrocarbon group which is monocyclic or polycyclic and has 3 to 12 carbon atoms, more preferably a divalent non-aromatic cyclic hydrocarbon group which is monocyclic or polycyclic and has 4 to 10 carbon atoms, and particularly preferably a divalent non-aromatic cyclic hydrocarbon group which is monocyclic and has 5 to 8 carbon atoms. Examples of the divalent non-aromatic cyclic hydrocarbon group include cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, and cyclooctylene. As the divalent cyclic hydrocarbon group, arylene is preferred. The divalent heterocyclic group is a divalent aromatic heterocyclic group or a divalent non-aromatic heterocyclic group. The heteroatom constituting the heterocyclic ring preferably contains at least one selected from the group consisting of an oxygen atom, a sulfur atom, a nitrogen atom, a phosphorus atom, a boron atom, and a silicon atom, and more preferably contains at least one selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom. The divalent aromatic heterocyclic group is preferably a divalent aromatic heterocyclic group having 3 to 15 carbon atoms, more preferably a divalent aromatic heterocyclic group having 3 to 9 carbon atoms, and particularly preferably a divalent aromatic heterocyclic group having 3 to 6 carbon atoms. Examples of the divalent aromatic heterocyclic group include pyrrolediyl, furandiyl, thiophenediyl, pyridinediyl, pyridazinediyl, pyrimidinediyl, pyrazinediyl, triazinediyl, pyrazolediyl, imidazolediyl, thiazolediyl, isothiazolediyl, oxazolediyl, isoxazolediyl, triazolediyl, tetrazolediyl, indolediyl, purinediyl, anthraquinonediyl, carbazolediyl, fluorenediyl, quinolinediyl, isoquinolinediyl, quinazolinediyl, and phthalazinediyl. The divalent non-aromatic heterocyclic group is preferably a non-aromatic heterocyclic group having 3 to 15 carbon atoms, more preferably a non-aromatic heterocyclic group having 3 to 9 carbon atoms, and particularly preferably a non-aromatic heterocyclic group having 3 to 6 carbon atoms. Examples of the divalent non-aromatic heterocyclic group include pyrrolidionediy l, pyrrolinedionediy l, oxirany l, aziridinediy l, azetidinediy l, oxetany l, thietany l, pyrrolidinediy l, dihydrofurandiy l, tetrahydrofurandiy l, dioxolanediy l, tetrahydrothiophenediy l, pyrrolinediy l, imidazolidinediy l, oxazolidinediy l, piperidinediy l, dihydropyrandiy l, tetrahydropyrandiy l, tetrahydrothiopyrandiy l, morpholinediy l, thiomorpholinediy l, piperazinediy l, dihydrooxazinediy l, tetrahydrooxazinediy l, dihydropyrimidinediy l, and tetrahydropyrimidinediy l. As the divalent heterocyclic group, a divalent aromatic heterocyclic group is preferred. Examples of the substituent include the following: (i) A halogen atom; (ii) A monovalent hydrocarbon group; (iii) A monovalent heterocyclic group; (iv) An aralkyl; (v) R ａ -O-, R ａ -C(=O)-, R ａ -O-C(=O)-, or Ra-C(=O)-O- (Ra represents a hydrogen atom or a monovalent hydrocarbon group.); or (vi) NR ｂ R ｃ -, NR ｂ R ｃ -C(=O)-, NR ｂ R ｃ -C(=O)-O-, or R ｂ -C(=O)-NR ｃ - (R ｂ and R ｃ are the same or different and each represents a hydrogen atom or a monovalent hydrocarbon group.); (vii) A nitro group, a sulfuric acid group, a sulfonic acid group, a cyano group, and a carboxyl group. The definitions, examples, and preferred examples of the halogen atom, monovalent hydrocarbon group, and monovalent heterocyclic group in the above-described substituents are the same as those described above, respectively. Aralkyl means arylalkyl. The definitions, examples, and preferred examples of aryl and alkyl in arylalkyl are as described above. As the aralkyl, aralkyl having 3 to 15 carbon atoms is preferred. Examples of such aralkyl include benzoyl, phenethyl, naphthylmethyl, and naphthylethyl. In addition, as the linker, for example, a divalent group derived from a substance selected from amino acids, peptides, nucleic acids, sugars, other polymeric substances (e.g., polyethylene glycol), etc. may be used alone or in combination of two or more, or may be used in combination with the divalent group as described above. The total number of atoms constituting the main chain in the linker is not particularly limited, and may be, for example, 1 or more, 2 or more, 5 or more, 10 or more, or 20 or more. The total number of such atoms may be 1000 or less, 500 or less, 300 or less, 200 or less, or 100 or less. The linker is a chemical structure connecting the Fc and the cell surface, which is formed by the reaction of a bioorthogonal functional group introduced into a specific amino acid residue of one polypeptide in the Fc region with a group that reacts with a bioorthogonal functional group present on or introduced into the cell surface. More specifically, it may be a chemical structure of the portion connecting the functional group in the side chain of a specific amino acid residue present in the Fc region-constituting polypeptide and the functional group on the cell surface. <Modification of the Other Polypeptide> The antibody Fc region may have a functional substance introduced via a linker introduced into a functional group in the side chain of a specific amino acid residue at one or more positions of the other of the two Fc region-constituting polypeptides, that is, the polypeptide not involved in cell binding. (Functional Substance) The functional substance is not particularly limited as long as it is a substance that imparts any function to the antibody, and examples thereof include drugs, labeling substances, affinity substances, transport substances, and stabilizers. Preferably, it may be a drug, a labeling substance, an affinity substance, or a transport substance. The functional substance may also be a single functional substance or a substance in which two or more functional substances are linked. The drug may be a drug for any disease. Examples of such diseases include cancer (e.g., lung cancer, gastric cancer, colorectal cancer, pancreatic cancer, kidney cancer, liver cancer, thyroid cancer, prostate cancer, bladder cancer, ovarian cancer, uterine cancer, bone cancer, skin cancer, brain tumor, melanoma), autoimmune diseases and inflammatory diseases (e.g., allergic diseases, rheumatoid arthritis, systemic lupus erythematosus), cerebrovascular diseases (e.g., cerebral infarction, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis), infectious diseases (e.g., bacterial infections, viral infections), hereditary and rare diseases (e.g., hereditary spherocytosis, non-dystrophic myotonia), eye diseases (e.g., age-related macular degeneration, diabetic retinopathy, retinitis pigmentosa), diseases in the orthopedic field (e.g., osteoarthritis), blood diseases (e.g., leukemia, purpura), and other diseases (e.g., metabolic disorders such as diabetes and hyperlipidemia, liver diseases, kidney diseases, lung diseases, cardiovascular diseases, digestive organ diseases). The drug may be a preventive or therapeutic drug for the disease or a drug for alleviating side effects. More specifically, the drug may be an anticancer agent. Examples of the anticancer agent include chemotherapeutic agents, toxins, radioisotopes, or substances containing them. Examples of chemotherapeutic agents include DNA damaging agents, antimetabolites, enzyme inhibitors, DNA intercalating agents, DNA cleaving agents, topoisomerase inhibitors, DNA binding inhibitors, tubulin binding inhibitors, cytotoxic nucleosides, and platinum compounds. Examples of toxins include bacterial toxins (e.g., diphtheria toxin) and plant toxins (e.g., ricin). Examples of radioisotopes include radioisotopes of hydrogen atoms (e.g., ３ H), radioisotopes of carbon atoms (e.g., １４ C), radioisotopes of phosphorus atoms (e.g., ３２ P), radioisotopes of sulfur atoms (e.g., 35 Ｓ ), radioisotopes of yttrium (e.g., ９０ Y), radioisotopes of technetium (e.g.,９９ｍ Technetium (Tc), radioisotopes of indium (e.g., １１１ In), radioisotopes of iodine atoms (e.g., １２３ I, １２５ I, １２９ I, １３１ I), radioisotopes of samarium (e.g., １５３ Sm), radioisotopes of rhenium (e.g., １８６ Re), radioisotopes of astatine (e.g., ２１１ At), radioisotopes of bismuth (e.g., ２１２ Bi) can be mentioned. More specifically, as drugs, auristatins (MMAE, MMAF), maytansines (DM1, DM4), PBD (pyrrolobenzodiazepine), IGN, camptothecin analogs, calicheamicin, duocarmycin, eribulin, anthracyclines, dmDNA31, tubulysin can be mentioned. The labeling substance is a substance that enables the detection of a target (e.g., tissue, cell, substance). Examples of the labeling substance include enzymes (e.g., peroxidase, alkaline phosphatase, luciferase, β-galactosidase), affinity substances (e.g., streptavidin, biotin, digoxigenin, aptamer), fluorescent substances (e.g., fluorescein, fluorescein isothiocyanate, rhodamine, green fluorescent protein, red fluorescent protein), luminescent substances (e.g., luciferin, aequorin, acridinium ester, tris(2,2'-bipyridyl)ruthenium, luminol), radioisotopes (e.g., those described above), or substances containing them. The affinity substance is a substance having an affinity for the target. Examples of the affinity substance include affinity proteins or peptides such as antibodies, aptamers, lectins, and complementary strands to the target nucleic acid. The affinity substance is preferably an affinity protein or an affinity peptide, and may be an antibody. The type of animal from which the antibody used as the functional substance is derived is the same as those described above. Examples of the antibody used as the functional substance include full-length antibodies and their fragments (fragment antibodies). The fragment antibody only needs to maintain the binding property to the desired antigen. For example, Fab, Fab', F(ab') ２, such as scFv and VHH antibodies. The substance for transport is a substance having the ability to transport a compound. As the substance for transport, a substance that can encapsulate a compound in a protein outer shell (e.g., multimer), such as ferritin, virus particles, virus-like particles, is preferable. The stabilizer is a substance that enables the stabilization of an antibody. Examples of the stabilizer include diols, glycerin, nonionic surfactants, anionic surfactants, natural surfactants, saccharides, and polyols. The functional substance may also be a peptide, protein, nucleic acid, organic compound, inorganic compound, sugar chain, lipid, polymer, metal (e.g., gold), or chelator. Examples of the peptide include cell-penetrating peptides, blood-brain barrier-permeable peptides, and peptide pharmaceuticals. Examples of the protein include enzymes, cytokines, antibody fragments, lectins, interferons, serum albumin, antibodies, and ferritin. Examples of the nucleic acid include DNA, RNA, and artificial nucleic acids. Examples of the nucleic acid also include RNA interference-inducing nucleic acids (e.g., siRNA), aptamers, and antisense. Examples of the organic compound include low-molecular-weight organic compounds such as proteolysis-inducing chimeric molecules, dyes, and photodegradable compounds. Examples of the inorganic compound include silica, talc, and alumina. Among the Fc constituent polypeptides, the specific amino acid residues to which the functional substance binds in the polypeptide not involved in cell binding may be amino acid residues such as lysine described above. The functional substance is introduced to the specific amino acid residue via a linker. The linker connecting the functional substance to Fc can be a divalent group, and the divalent groups described above can be used. Examples of the substituent when the divalent group is substituted include those described above. Here, the total number of atoms constituting the main chain in the linker is not particularly limited, and may be, for example, 1 or more, 2 or more, 5 or more, 10 or more, or 20 or more. Such a total number of atoms may be 1000 or less, 500 or less, 300 or less, 200 or less, 100 or less, or 50 or less. The linker is a chemical structure of the part connecting Fc and the functional substance, which is formed by the reaction between a bioorthogonal functional group introduced into specific amino acid residues of a polypeptide not involved in the cell binding of the Fc region and a group that reacts with the bioorthogonal functional group linked to the functional substance. More specifically, it may be the chemical structure of the part connecting the functional group in the side chain of a specific amino acid residue present in the polypeptide constituting the Fc region and the functional substance. <Use of the Fc-cell complex> The Fc-cell complex can be used for various applications. When the Fc-cell complex is an antibody-cell complex, for example, when the antibody is an antibody against the surface antigen of the target tissue, it can be used as a cell medicine for delivering cells to the target tissue. Also, when the Fc-cell complex is an antibody-cell complex and the antibody is an antibody against a cancer cell-specific surface antigen, and the cell is an NK cell, a T cell, etc., it can be used as a cell medicine having a cancer cell killing effect. In addition, when the Fc-cell complex is a cell-Fc enzyme fusion protein complex, it can also be used for substance production by performing an enzyme reaction on the cell surface. <Method for producing the Fc-cell complex> The method for producing the Fc-cell complex of the present invention includes the following steps (I) to (V). (I) A step of preparing an antibody Fc region in which two antibody Fc region-constituting polypeptides are disulfide-bonded. (II) To the antibody Fc region, A step of reacting a compound represented by the following formula (Ia) or formula (Ib) to form an Fc-compound (Ia) complex or an Fc-compound (Ib) complex. (III) A step of cleaving the Fc-compound (Ia) complex or the Fc-compound (Ib) complex with the cleavable moiety to form an Fc region containing no affinity substance and having a bioorthogonal functional group introduced therein. (IV) A step of preparing cells having a functional group that reacts with a bioorthogonal functional group on the surface. Step (V): Introducing the Fc region into the cell surface by reacting the Fc region with the introduced bioorthogonal functional group and the functional group that reacts with the bioorthogonal functional group of the cell. Hereinafter, each step will be described. <Step (I): Step of preparing an antibody Fc region> The antibody Fc region is as described above. The Fc region may further be an antibody containing F(ab'), that is, an immunoglobulin, or the Fc region may be an Fc fusion protein further containing a functional polypeptide. ２ Such an antibody or Fc fusion protein may be a commercially available one, or one prepared by a known method can be used. For example, an antibody or Fc fusion protein produced by genetic recombination can be used. <Step (II): Step of reacting the antibody Fc region with a compound represented by formula (Ia) or formula (Ib) (also referred to as compound (Ia) and compound (Ib)) to form an Fc-compound (Ia) complex or an Fc-compound (Ib) complex> First, the components of formula (Ia) or formula (Ib) will be described. <Affinity substance A> The affinity substance A is an affinity substance containing a peptide having an affinity for the constant region in the heavy chain of the antibody. Here, as the peptide having an affinity for the constant region in the heavy chain of the antibody, it can be selected from the affinity peptides having a lysine residue and the affinity peptides having no lysine residue described later. The affinity substance A may be an affinity substance represented by AP1-L -AP2 (wherein AP1 represents a first affinity peptide having an affinity for the constant region in the heavy chain of the antibody, AP2 represents a second affinity peptide having an affinity for the constant region in the heavy chain of the antibody, and L Ａ represents a linker.). Ａ In the formula (A) and other formulas presented in connection with the present invention, a -(hyphen) indicates that two units present on both sides thereof are covalently bonded. Therefore, in the formula (A), AP1 is covalently bonded to L, L is covalently bonded to both AP1 and AP2, and AP2 is covalently bonded to L. The first and second affinity peptides are not particularly limited as long as they are peptides having an affinity for the constant region in the heavy chain of an antibody, and can be selected from an affinity peptide having a lysine residue and an affinity peptide having no lysine residue. Preferably, one of the first and second affinity peptides may be an affinity peptide having one lysine residue, and the other may be an affinity peptide having no lysine residue. A number of peptides have been reported as affinity peptides having an affinity for the constant region in the heavy chain of an antibody and having one lysine residue (see, for example, International Publication No. 2016 / 186206, International Publication No. 2018 / 199337, International Publication No. 2019 / 240287, International Publication No. 2019 / 240288, International Publication No. 2020 / 090979). Therefore, in the present invention, such a peptide can be used as one of the first and second affinity peptides. More specifically, the following may be used as an affinity peptide having an affinity for the constant region in the heavy chain of an antibody and having one lysine residue: An affinity peptide containing the amino acid sequences of SEQ ID NOs: 39 to 72 of International Publication No. 2018 / 199337; An affinity peptide containing the amino acid sequences of SEQ ID NOs: 5, 6, 37 to 100 of International Publication No. 2019 / 240288; An affinity peptide containing the amino acid sequences of SEQ ID NOs: 5, 8 to 57, 68 to 92 of International Publication No. 2019 / 240287; An affinity peptide having QET at the N-terminus (SEQ ID NOs: 7 to 10, 22 to 25, 52, 53 of International Publication No. 2020 / 090979); and Among the following affinity peptides (1) to (12), an affinity peptide having one lysine residue. (1) Various IgG-binding peptides having an affinity for a specific region (CH2 domain) of human IgG in general (i.e., human IgG1, IgG2, IgG3, and IgG4; the same applies hereinafter) (see, for example, International Publication No. 2008 / 054030, International Publication 2013 / 027796, International Publication No. 2016 / 186206); (2) Protein A Mimetic (PAM) peptide having an affinity for a specific region (CH2 domain) of human IgG in general (see, for example, Fassina G et al., JOURNAL OF MOLECULAR RECOGNITION, 1996, VOL. 6, 564-569); (3) EPIHRSTLTALL (SEQ ID NO: 1) having an affinity for a specific region (CH2 domain) of human IgG in general (see, for example, Ehrlich G.K et al., J. Biochem. Biophys. Methods, 2001, VOL. 49, 443-454); (4) (NH ２ -Cys1-X1-X2-X3-X4)2-Lys-Gly-OH having an affinity for a specific region (Fc region) of human IgG in general (see, for example, Ruvo M et al., ChemBioChem, 2005, VOL. 6, 1242-1253); (5) FARLVSSIRY (SEQ ID NO: 2), FGRLVSSIRY (SEQ ID NO: 3), and TWKT SRISIF (SEQ ID NO: 4) having an affinity for a specific region (Fc region) of human IgG in general (see, for example, Kook M etal., Journal of Immunological Methods, 1998, VOL. 221, 151-157); (6) QSYP (SEQ ID NO: 5) having an affinity for a specific region of human IgG in general (see, for example, Jacobs J.M. et al., Bio. Techniques, 2003, VOL. 34, 132-141); HWRGWYV (SEQ ID NO: 6), HYFKFD (SEQ ID NO: 7), and HFRRHL (SEQ ID NO: 8) that have an affinity for a specific region (Fc region) of human IgG in general (see, for example, Carbonell R.G. et al., Journal of Chromatography A, 2009, VOL. 1216, 910-918); DAAG (SEQ ID NO: 9) that has an affinity for a specific region (Fc region) of human IgG in general (see, for example, Lund L.N. et al., Journal of Chromatography A, 2012, VOL. 1225, 158-167); Fc-I, Fc-II, and Fc-III that have an affinity for a specific region (Fc region) of human IgG in general (see, for example, Warren L.Delano et al., Science, 2000, VOL. 287, 1279-1283; International Publication No. 2001 / 045746); and NARKFYKG (SEQ ID NO: 10) and NKFRGKYK (SEQ ID NO: 11) that have an affinity for a specific region (Fc region) of human IgG in general (see, for example, Biochemical Engineering Journal, 2013, VOL. 79, 33-40); Protein A, Protein G, Protein L, or Protein Z that have an affinity for a specific region (Fc region) of human IgG in general, or fragments thereof (see, for example, Moks Tet al., Eur J Biochem. 1986 May 2;156(3):637-43; Sjobring UJ et al., Biol Chem. 1991 Jan 5;266(1):399-405; Graille M el al., Structure. 2001 Aug;9(8):679-87; Nilsson B et al., Protein Eng. 1987 Feb-Mar;1(2):107-13); Various IgG-binding peptides that have an affinity for a specific region (Fc region or CH2 domain) of human IgG in general (see, for example, International Publication No. 2018 / 199337, International Publication No. 2019 / 240287, International Publication No. 2019 / 240288, International Publication No. 2020 / 090979). In certain embodiments, examples of the affinity peptide that has an affinity for the constant region in the heavy chain of an antibody and has one lysine residue include, for example, the following (1) to (4): (1) An affinity peptide containing the amino acid sequence (Fc3K) of RGNCAYHKGQI IWCTYH (SEQ ID NO: 12); (2) An affinity peptide that contains an amino acid sequence in which one or two amino acid residues other than the lysine residue and the cysteine residue in the amino acid sequence of RGNCAYHKGQI IWCTYH (SEQ ID NO: 12) are substituted with another amino acid residue other than the lysine residue and the cysteine residue, and has an affinity for the constant region in the heavy chain of an antibody; (3) An affinity peptide containing the amino acid sequence (Z34CK) of FN KQCQRRFYEA LHDPNLNEEQRNA RIRSIREE C (SEQ ID NO: 13); and (4) An affinity peptide that contains an amino acid sequence in which one or two amino acid residues other than the lysine residue and the cysteine residue in the amino acid sequence of FN KQCQRRFYEA LHDPNLNEEQRNA RIRSIREE C (SEQ ID NO: 13) are substituted with another amino acid residue other than the lysine residue and the cysteine residue, and has an affinity for the constant region in the heavy chain of an antibody. Here, the two cysteine residues contained in the above amino acid sequence may be cross-linked by a disulfide bond. Numerous affinity peptides have been reported that have an affinity for the constant region in the heavy chain of an antibody and do not have a lysine residue. Further, in the above affinity peptide that has an affinity for the constant region in the heavy chain of an antibody and has one lysine residue, the lysine residue is often not for maintaining the affinity for the constant region in the heavy chain of the antibody, but is introduced for covalent bonding with another moiety (e.g., a partial compound containing a reactive group) to derivatize the affinity substance (see, for example, International Publication No. 2016 / 186206, International Publication No. 2018 / 199337, International Publication No. 2019 / 240287, International Publication No. 2019 / 240288, International Publication No. 2020 / 090979). Therefore, even if such a lysine residue is replaced with another amino acid residue, the affinity for the constant region in the heavy chain of the antibody can be maintained. Accordingly, as the affinity peptide that has an affinity for the constant region in the heavy chain of an antibody and does not have a lysine residue, an affinity peptide in which the lysine residue in the affinity peptide that has an affinity for the constant region in the heavy chain of the antibody and has one lysine residue is replaced with another amino acid residue (preferably, a normal natural amino acid residue constituting a protein other than a lysine residue and a cysteine residue) and has an affinity for the constant region in the heavy chain of the antibody can be used. More specifically, the following may be used as the affinity peptide that has an affinity for the constant region in the heavy chain of an antibody and does not have a lysine residue: SEQ ID NOs: 20 to 38, 73 to 75 (when Xaa1 is other than a lysine residue), SEQ ID NO: 92 of International Publication No. 2018 / 199337; SEQ ID NOs: 7, 11 to 14, 108 of International Publication No. 2019 / 240288; Among the above (1) to (4) listed as examples of the affinity peptide that has an affinity for the constant region in the heavy chain of an antibody and has one lysine residue, an affinity peptide in which the lysine residue is replaced with another amino acid residue (preferably, another amino acid residue other than a cysteine residue); and Among the above (1) to (12) affinity peptides listed as examples of the affinity peptide, an affinity peptide that does not have a lysine residue. In certain embodiments, examples of affinity peptides having no lysine residue include, for example, the following (5) to (10): (5) An affinity peptide comprising the amino acid sequence (Z34CM) of FNMQCQRRFYEAHLDPNLNEEQRNARIRSIREEEC (SEQ ID NO: 14); (6) An affinity peptide comprising an amino acid sequence in which one or two amino acid residues other than cysteine residues in the amino acid sequence of FNMQCQRRFYEAHLDPNLNEEQRNARIRSIREEEC (SEQ ID NO: 14) are substituted with another amino acid residue other than lysine residue and cysteine residue, and having an affinity for the constant region in the heavy chain of an antibody; (7) An affinity peptide comprising the amino acid sequence (ProAR) of FNREQQNAFYEILHLPNLNEEQRNGFIQSLRDDPSSQSANLLAEA (SEQ ID NO: 15); (8) An affinity peptide comprising an amino acid sequence in which one or two amino acid residues other than cysteine residues in the amino acid sequence of FNREQQNAFYEILHLPNLNEEQRNGFIQSLRDDPSSQSANLLAEA (SEQ ID NO: 15) are substituted with another amino acid residue other than lysine residue and cysteine residue, and having an affinity for the constant region in the heavy chain of an antibody; (9) An affinity peptide comprising the amino acid sequence of RGNCAYHRGQI IWCTYH (SEQ ID NO: 16); and (10) An affinity peptide comprising an amino acid sequence in which one or two amino acid residues other than cysteine residues in the amino acid sequence of RGNCAYHRGQI IWCTYH (SEQ ID NO: 16) are substituted with another amino acid residue other than lysine residue and cysteine residue, and having an affinity for the constant region in the heavy chain of an antibody. Here, the two cysteine residues contained in the above amino acid sequence may be crosslinked by a disulfide bond. Substitution of amino acid residues may be a conservative substitution. The term "conservative substitution" refers to substituting a given amino acid residue with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains are well known in the art. For example, such families include amino acids having basic side chains (e.g., lysine, arginine, histidine), amino acids having acidic side chains (e.g., aspartic acid, glutamic acid), amino acids having uncharged polar side chains (e.g., asparagine, glutamine, serine, threonine, tyrosine, cysteine), amino acids having nonpolar side chains (e.g., glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), amino acids having β-branched side chains (e.g., threonine, valine, isoleucine), amino acids having aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine), amino acids having side chains containing a hydroxyl group (e.g., alcoholic, phenolic) (e.g., serine, threonine, tyrosine), and amino acids having sulfur-containing side chains (e.g., cysteine, methionine). Amino acids having uncharged polar side chains and amino acids having nonpolar side chains may be collectively referred to as neutral amino acids. Preferably, conservative substitution of amino acids may be substitution between aspartic acid and glutamic acid, substitution among arginine, lysine and histidine, substitution between tryptophan and phenylalanine, substitution between phenylalanine and valine, substitution among leucine, isoleucine and alanine, and substitution between glycine and alanine. L Ａ The linker represented by Ａ is a divalent group. The divalent group may or may not be substituted. Examples of the divalent group include those described above. Examples of the substituent when the divalent group is substituted include those described above. Here, the total number of atoms constituting the main chain in the linker may be 2 to 10. Such a total number of atoms may be 3 or more, or 4 or more. Such a total number of atoms may be 9 or less, 8 or less, or 7 or less. More specifically, such a total number of atoms may be 3 to 9, 4 to 8, or 4 to 7. As the linker, substances such as peptides, nucleic acids, sugars, other polymeric substances (e.g., polyethylene glycol), divalent hydrocarbon groups (e.g., alkyl chains), etc. may be used, but a peptide linker is more preferred. The number of amino acid residues constituting the peptide linker can be appropriately set according to conditions such as the type of amino acid residue (e.g., α-amino acid, β-amino acid, γ-amino acid. Preferably α-amino acid). For example, the peptide linker may consist of 20 or more amino acid residues. The peptide linker may consist of 22 or more, 24 or more, 26 or more, 28 or more, 30 or more, 32 or more, 34 or more, 36 or more, 38 or more, or 40 or more amino acid residues. The peptide linker may also consist of less than 50, less than 49, less than 48, less than 47, less than 46, or less than 45 amino acid residues. As the amino acid residues constituting the peptide linker, the above-mentioned natural amino acids or residues of unnatural amino acids can be used. Preferably, the amino acid residues constituting the peptide linker may contain only the residues of the above-mentioned natural amino acids. Examples of amino acid residues suitable for the peptide linker include, but are not limited to, alanine, proline, serine, and glycine. As the peptide linker, those disclosed in International Publication No. 2021 / 112249 and International Publication No. 2011 / 144756 can also be used. <Reactive group R against antibody> As the reactive group for the antibody, among the amino acid residues constituting the antibody (protein), a reactive group for an amino acid residue having a side chain that is prone to reaction can be used. Among the above-described 20 natural amino acids constituting the protein, glycine having no side chain, and alanine, isoleucine, leucine, phenylalanine, and valine whose side chains are hydrocarbon groups are inert to normal reactions. Therefore, the reactive group for the antibody is a group capable of reacting with the side chain of any one or two or more (e.g., 2, 3, 4) of the 14 amino acids consisting of asparagine, glutamine, methionine, proline, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, arginine, histidine, and lysine. The reactive group for the antibody is more preferably a reactive group specific to the side chain of any one of lysine, tyrosine, tryptophan, or cysteine, even more preferably a reactive group specific to the side chain of any one of lysine, tyrosine, or tryptophan, and particularly preferably a reactive group specific to the side chain of lysine or tyrosine, especially the side chain of lysine. For details of such reactive groups, see, for example, International Publication No. WO2016 / 186206, International Publication No. WO2018 / 199337, International Publication No. WO2019 / 240287, International Publication No. WO2019 / 240288, International Publication No. WO2020 / 090979. The reactive group specific to the side chain of the lysine residue is a group capable of specifically reacting with the amino group (NH ２ ) present in the side chain of the lysine residue, and examples include an activated ester residue (e.g., N-hydroxysuccinimide residue), vinyl sulfone residue, sulfonyl chloride residue, isocyanate residue, isothiocyanate residue, aldehyde residue, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid residue, 2-imino-2-methoxyethyl residue, diazonium terephthalic acid residue, α-halogen-substituted acetamide, α-halogen-substituted methyl ketone. The above-described reactive group specific to the side chain of the lysine residue and the amino group (NH ２According to the reaction with ( ), as a linking moiety, for example, an amide residue, a urea residue, a pyridine residue, a carbamate residue, or a sulfonamide residue can be formed. (Group B containing a bioorthogonal functional group) A bioorthogonal functional group refers to a group that does not react with biological components (e.g., amino acids, proteins, nucleic acids, lipids, sugars, phosphates) or reacts with them at a slow rate, but selectively reacts with components other than biological components. Bioorthogonal functional groups are well-known in the art (see, for example, Sharpless K. B. et al., Angew. Chem. Int. Ed. 40, 2004 (2015); Bertozzi C. R. et al., Science 291, 2357 (2001); Bertozzi C. R. et al., Nature Chemical Biology 1, 13 (2005)). A bioorthogonal functional group for a protein is a group that does not react with the side chains of the 20 natural amino acid residues that make up the protein, or reacts with the side chains of these residues at a slow rate, but reacts with the target functional group. The 20 natural amino acids that make up a protein are alanine (A), asparagine (N), cysteine (C), glutamine (Q), glycine (G), isoleucine (I), leucine (L), methionine (M), phenylalanine (F), proline (P), serine (S), threonine (T), tryptophan (W), tyrosine (Y), valine (V), aspartic acid (D), glutamic acid (E), arginine (R), histidine (H), and lysine (K). Among these 20 natural amino acids, glycine, which has no side chain (i.e., is a hydrogen atom), and alanine, isoleucine, leucine, phenylalanine, and valine, whose side chains are hydrocarbon groups (i.e., do not contain a heteroatom selected from the group consisting of sulfur, nitrogen, and oxygen atoms in the side chain), are inert to normal reactions. Therefore, a bioorthogonal functional group for a protein is a group that does not react with, or reacts with at a slow rate, the side chains of these amino acids having side chains that are inert to normal reactions, in addition to the side chains of asparagine, glutamine, methionine, proline, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, arginine, histidine, and lysine, but reacts with the target functional group. Examples of such bioorthogonal functional groups include an azide group, an aldehyde residue, a thiol group, an alkene residue (in other words, it suffices to have a vinylene (ethenylene) moiety which is the smallest unit having a double bond between carbon atoms. The same applies hereinafter), an alkyne residue (in other words, it suffices to have an ethynylene moiety which is the smallest unit having a triple bond between carbon atoms. The same applies hereinafter), a halogen residue, a tetrazine residue, a nitrone residue, a hydroxylamine residue, a nitrile residue, a hydrazine residue, a ketone residue, a boronic acid residue, a cyanobenzothiazole residue, an allyl residue, a phosphine residue, a maleimide residue, a disulfide residue, a thioester residue, an α-halocarbonyl residue (e.g., a carbonyl residue having a fluorine atom, a chlorine atom, a bromine atom or an iodine atom at the α-position. The same applies hereinafter), an isonitrile residue, a sydnone residue, and a selenium residue. Examples of the group having an alkyne residue (i.e., an ethynylene moiety) include dibenzocyclooctyne (DBCO), diazacyclononine (DACN), and the like. The bioorthogonal functional group may or may not be protected. The bioorthogonal functional group refers to an unprotected bioorthogonal functional group or a protected bioorthogonal functional group. The unprotected bioorthogonal functional group corresponds to the above-mentioned bioorthogonal functional group. The protected bioorthogonal functional group is a group that generates a bioorthogonal functional group by cleavage of a protecting group. Cleavage of the protecting group can be carried out by specific treatment under conditions (mild conditions) that cannot cause protein denaturation and decomposition (e.g., cleavage of amide bonds). Such specific treatment includes, for example, (a) treatment with one or more substances selected from the group consisting of acidic substances, basic substances, reducing agents, oxidizing agents, and enzymes, (b) treatment with physicochemical stimuli selected from the group consisting of light, or (c) leaving in the case of using a cleavable linker containing a self-degradable cleavable moiety. Such protecting groups and their cleavage conditions are common general knowledge in the art (e.g., G. Leriche, L. Chisholm, A. Wagner, Bioorganic & Medicinal Chemistry. 20, 571 (2012); Feng P. et al., Journal of American Chemical Society. 132, 1500 (2010).; Bessodes M. et al., Journal of Controlled Release, 99, 423 (2004).; DeSimone, J.M., Journal of American Chemical Society. 132, 17928 (2010); Thompson, D.H., Journal of Controlled Release, 91, 187 (2003); Schoenmarks, R.G., Journal of Controlled Release, 95, 291 (2004)). The reaction conditions (e.g., reaction temperature, reaction time, reaction solution) for mild conditions are as described below. Examples of the protected bioorthogonal functional group include a disulfide residue, an ester residue, an acetal residue, a ketal residue, an imine residue, and a vicinal diol residue. Preferably, the bioorthogonal functional group is an unprotected bioorthogonal functional group. More preferably, the bioorthogonal functional group may be a specific bioorthogonal functional group that is excellent in reactivity (e.g., reaction level and / or reaction specificity) with other bioorthogonal functional groups. Examples of such bioorthogonal functional groups include an azide group, an alkyne residue (preferably, a cyclic group having a triple bond between carbon atoms, which may be substituted with a substituent as described above), a tetrazine residue, an alkene residue, a thiol group, a maleimide residue, a furan residue, and a halocarbonyl residue. The group containing the bioorthogonal functional group represented by B may be a group consisting of a bioorthogonal functional group or a group containing a bioorthogonal functional group and other moieties. Examples of the other moieties include, for example, a linking moiety between the bioorthogonal functional group and a linker. The linking moiety is, for example, a divalent group. The divalent group may or may not be substituted. The definitions, examples, and preferred examples of the bioorthogonal functional group, the divalent group, and the substituent when the divalent group is substituted are as described above. <Cleavable moiety CLE> The cleavable moiety is a site that can be cleaved by a specific treatment under conditions (mild conditions) that cannot cause denaturation and decomposition of proteins (e.g., cleavage of amide bonds). Therefore, it can be said that the cleavable moiety is a site (a bond other than an amide bond) that can be cleaved by a specific cleavage treatment under mild conditions. Examples of such specific treatments include (a) treatment with one or more substances selected from the group consisting of acidic substances, basic substances, reducing agents, oxidizing agents, and enzymes, (b) treatment with physicochemical stimuli such as light, or (c) incubation when using a cleavable linker containing a self-degradable cleavable moiety. Such cleavable linkers and their cleavage conditions are common general knowledge in the art (e.g., G. Leriche, L. Chisholm, A. Wagner, Bioorganic & Medicinal Chemistry. 20, 571 (2012); Feng P. et al., Journal of American Chemical Society. 132, 1500 (2010).; Bessodes M. et al., Journal of Controlled Release, 99, 423 (2004).; DeSimone, J.M., Journal of American Chemical Society. 132, 17928 (2010); Thompson, D.H., Journal of Controlled Release, 91, 187 (2003); Schoenmarks, R.G., Journal of Controlled Release, 95, 291 (2004)). The reaction conditions (e.g., reaction temperature, reaction time, reaction solution) for mild conditions are as described below.Examples of the cleavable moiety as described above include a disulfide residue, an acetal residue, a ketal residue, an ester residue, a carbamoyl residue, an alkoxyalkyl residue, an imine residue, a tertiary alkyloxycarbamate residue (e.g., tert-butyloxycarbamate residue), a silane residue, a hydrazone-containing residue (e.g., hydrazone residue, acylhydrazone residue, bisarylhydrazone residue), a phosphoramidate residue, an aconityl residue, a trityl residue, an azo residue, a vicinal diol residue, a selenium residue, an aromatic ring-containing residue having an electron-withdrawing group, a coumarin-containing residue, a sulfone-containing residue, an unsaturated bond-containing chain residue, and a glycosyl residue. The aromatic ring group having an electron-withdrawing group preferably has an aromatic ring group selected from the group consisting of aryl, aralkyl, aromatic heterocyclic group, and alkyl having an aromatic heterocyclic group, and more preferably aralkyl or alkyl having an aromatic heterocyclic group. The electron-withdrawing group is preferably bonded to the 2-position of the ring. Even more preferably, the aromatic ring-containing residue having an electron-withdrawing group is, for example, an aralkyl (e.g., benzyl) having an electron-withdrawing group at the 2-position. Examples of the electron-withdrawing group include a halogen atom, an alkyl substituted with a halogen atom (e.g., trifluoromethyl), a boronic acid residue, mesyl, tosyl, triflate, nitro, cyano, a phenyl group, and a keto group (e.g., acyl). Examples of the ester residue include a normal ester residue composed of a carbon atom and an oxygen atom [e.g., alkyl ester (e.g., tertiary alkyloxycarbonyl such as tert-butyloxycarbonyl), aryl ester (e.g., phenacyl ester, 2-(diphenylphosphino)benzoate), glycosyl ester residue, orthoester residue], an ester residue containing a sulfur atom and an oxygen atom (e.g., thioester residue such as α-thiophenyl ester residue, alkylthioester residue), an ester residue containing a phosphorus atom and an oxygen atom (e.g., phosphodiester residue, phosphotriester residue), and an activated ester residue (e.g., N-hydroxysuccinimide residue). Examples of the sulfone-containing residue include a sulfone residue and a quinolinylbenzenesulfonate residue. The silane residue is preferably a silane residue having a group selected from the group consisting of alkyl, aryl, aralkyl, and alkoxy. Examples of such silane residues include dialkyldialkoxysilane residues (e.g., dimethyldialkoxysilane, diethyldialkoxysilane), or diaryldialkoxysilane residues (e.g., diphenyldialkoxysilane). The alkoxyalkyl (i.e., alkyloxyalkyl) residue is a group combining the above-described alkyloxy and alkyl, and examples include, but are not limited to, methoxymethyl residue, ethoxymethyl residue, methoxyethyl residue, and ethoxyethyl residue. The unsaturated bond-containing chain residue is a residue containing an unsaturated bond portion consisting of only carbon atoms [e.g., vinyl (ethenyl), which is the minimum unit having a carbon-carbon double bond, or ethynyl, which is the minimum unit having a carbon-carbon triple bond], or a residue containing an unsaturated bond portion consisting of carbon atoms and heteroatoms (e.g., nitrogen atom, sulfur atom, oxygen atom) (e.g., aldehyde, cyano). Examples of the unsaturated bond-containing chain residue include vinyl ether residue, cyanoethyl residue, ethylene residue, and malondialdehyde residue. Examples of the acidic substance (also referred to as an electrophilic reagent) include inorganic acidic substances such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acidic substances such as formic acid, acetic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, 3-morpholinopropanesulfonic acid, sodium dihydrogen phosphate, citric acid, dodecyl sulfate, N-dodecanoylsarcosine, and trifluoroacetic acid. Examples of the site cleavable by the acidic substance include alkyloxyarylalkyl residue, tertiary alkyloxycarbamate residue, acetal residue, silane residue, imine residue, vinyl ether residue, β-thiopropionate residue, trityl residue, hydrazone residue, aconityl residue, orthoester residue, carbamoyl residue, and 2-(diphenylphosphino)benzoate residue. Examples of basic substances (also referred to as nucleophilic reagents) include inorganic basic substances such as sodium hydroxide, potassium hydroxide, sodium acetate, potassium acetate, ammonium acetate, and organic basic substances such as hydroxylamine, triethylamine, N,N'-diisopropylamine. Examples of sites cleavable by basic substances include silane residues, cyanoethyl residues, sulfone residues, ethylene residues, glycosyl disuccinate residues, α-thiophenyl ester residues, unsaturated vinyl sulfide residues, malondialdehyde residues, acylhydrazone residues, and alkylthioester residues. Examples of reducing agents include cysteine, dithiothreitol, reduced glutathione, and β-mercaptoethanol. Examples of sites cleavable by reducing agents include disulfide residues, alkoxyalkyl residues, and azo residues. Examples of oxidizing agents include sodium periodate and oxidized glutathione. Examples of sites cleavable by oxidizing agents include vicinal diol residues and selenium residues. Examples of enzymes include trypsin, papain, TEV, thrombin, cathepsin B, cathepsin D, cathepsin K, caspase, protease, matrix metalloprotease, lipase, endoglycosidase, and PNGase F. Examples of sites cleavable by enzymes include ester residues, phosphodiester residues, and glycosyl residues. Examples of sites cleavable by light include 2-nitrobenzyl residues, phenacyl ester residues, 8-quinolinebenzenesulfonate residues, coumarin residues, phosphotriester residues, bisarylhydrazone residues, and biman dithiopropionate residues. Examples of self-degradable cleavable moieties include activated ester residues (e.g., N-hydroxysuccinimide residues). <Cleavable moiety CLE(B) capable of generating a bioorthogonal functional group upon cleavage> The cleavable moiety may be one that can generate a bioorthogonal functional group on the reactive group side by cleavage. Examples of such cleavable moieties include disulfide residues, ester residues (including the other ester residues described above such as normal ester residues and thioester residues), acetal residues (including the other acetal residues such as normal ester residues and thioacetal residues), ketal residues, imine residues, and vicinal diol residues. <Spacer> L １ The first linker represented by, and L ２ The second linker represented by may be the same or different divalent groups. The divalent group may or may not be substituted. Examples of the divalent group include those described above. Examples of the substituent when the divalent group is substituted include those described above. Also, as the linker, for example, substances such as peptides, nucleic acids, sugars, other polymeric substances (e.g., polyethylene glycol), and divalent hydrocarbon groups (e.g., alkyl chains) may be used. Those skilled in the art can appropriately determine the presence or absence of the linker and the type of the linker according to the types of the first and second affinity moieties used. In a specific embodiment, the total number of atoms constituting the main chain in the first linker and the second linker may be 2 to 10. Such a total number of atoms may be 3 or more, or 4 or more. Such a total number of atoms may be 9 or less, 8 or less, or 7 or less. More specifically, such a total number of atoms may be 3 to 9, 4 to 8, or 4 to 7. The number of atoms constituting the main chain in the first linker and the second linker may each be 1 to 9. Such a number of atoms may be 2 or more, or 3 or more. Such a number of atoms may be 8 or less, 7 or less, or 6 or less. More specifically, such a number of atoms may be 2 to 8, 3 to 7, or 3 to 6. The main chains in the first linker and the second linker are composed of a structure including a chain structure, a cyclic structure, or a combination thereof. When the main chain is a chain structure that does not include a cyclic structure, the number of atoms in the main chain can be determined by counting the number of atoms in the chain structure. On the other hand, when the main chain is a structure including a cyclic structure, the number of predetermined atoms constituting the cyclic structure can be determined by counting it as the number of atoms in the main chain. Specifically, the number of atoms in the main chain in the cyclic structure can be determined by counting the number of atoms in the shortest path connecting two bonds in the cyclic structure (for example, refer to the bold paths in (a) to (d) below). When the main chain is a structure including a combination of a chain structure and a cyclic structure, the number of atoms in the main chain can be determined by adding the number of atoms in the chain structure that does not include a cyclic structure to the number of atoms in the shortest path connecting two bonds in the cyclic structure. The method of counting the number of atoms in the main chain is the same for other linkers. In the case of, since the shortest path is the bold path, the number of atoms in the divalent cyclic structure that can be counted as the number of atoms in the main chain is 2. In the case of (b), since the shortest path is the bold path, the number of atoms in the divalent cyclic structure that can be counted as the number of atoms in the main chain is 3. In the case of (c), since any path is the shortest path (equidistant), the number of atoms in the divalent cyclic structure that can be counted as the number of atoms in the main chain is 4. In the case of (d), since the path at the condensation site is the shortest path, the number of atoms in the divalent cyclic structure that can be counted as the number of atoms in the main chain is 4. <Compound (Ia)> Compound (Ia) is a compound in which a reactive group for the Fc region and an affinity substance are linked by a linker, and the linker has a cleavable moiety capable of generating a bioorthogonal functional group on the reactive group side by cleavage. [In the formula, R represents a reactive group for the Fc region, and L １ represents a first linker, and L ２represents a second linker, CLE(B) represents a cleavable moiety capable of generating a bioorthogonal functional group on the reactive group side upon cleavage, and A represents AP1-L Ａ -AP2 (wherein AP1 represents a first affinity peptide having an affinity for the constant region in the heavy chain of an antibody, AP2 represents a second affinity peptide having an affinity for the constant region in the heavy chain of an antibody, and L Ａ represents a linker.) represents an affinity substance.]] The reactions using compound (Ia) (steps (II) and (III)) are shown in Figure 2. As an example of compound (Ia), a compound of the following formula (Ia-1) can be mentioned. [In the formula, X represents a leaving group, W １ , W ２ and W ３ each independently represent an oxygen atom or a sulfur atom, L ３ represents a third linker, L ４ represents a fourth linker, S represents a sulfur atom, A represents an affinity substance containing first and second affinity moieties having an affinity for the constant region in the heavy chain of an antibody.]] It may be a compound represented by or a salt thereof. The definition, examples, and preferred examples of the affinity substance represented by A are as described above. The leaving group represented by X is a group that can be eliminated by the reaction between the carbon atom in C=W １ adjacent to X and the amino group. Those skilled in the art can appropriately set such a leaving group. Examples of such a leaving group include, for example: (a) R Ａ -S (where R Ａ represents a hydrogen atom, a monovalent hydrocarbon group which may have a substituent, or a monovalent heterocyclic group which may have a substituent, and S represents a sulfur atom.); (b) R Ａ -O (where R Ａrepresents a hydrogen atom, a monovalent hydrocarbon group which may have a substituent, or a monovalent heterocyclic group which may have a substituent, and O represents an oxygen atom.); (c) R Ａ -(R Ｂ -)N (wherein R Ａ and R Ｂ each independently represent a hydrogen atom, a monovalent hydrocarbon group which may have a substituent, or a monovalent heterocyclic group which may have a substituent, and N represents a nitrogen atom.); or (d) a halogen atom. W １ 、W ２ and W ３ each independently represent an oxygen atom or a sulfur atom. Preferably, W １ 、W ２ and W ３ may be an oxygen atom. The third linker represented by L ３ , and the fourth linker represented by L ４ may be the same or different divalent groups. The divalent group may or may not be substituted. Examples of the divalent group include those described above. Examples of the substituent when the divalent group is substituted include those described above. In a specific embodiment, the total number of atoms constituting the main chain in the third linker and the fourth linker may be 2 to 10. Such a total number of atoms may be 3 or more, or 4 or more. Such a total number of atoms may be 9 or less, 8 or less, or 7 or less. More specifically, such a total number of atoms may be 3 to 9, 4 to 8, or 4 to 7. The number of atoms constituting the main chain in the third linker and the fourth linker may each be 1 to 9. Such a number of atoms may be 2 or more, or 3 or more. Such a number of atoms may be 8 or less, 7 or less, or 6 or less. More specifically, such a number of atoms may be 2 to 8, 3 to 7, or 3 to 6. The reactions using the compound (Ia-1) (Step (II) and Step (III)) are shown in FIG. 3. <Compound (Ib)> Compound (Ib) is a compound in which a reactive group for the Fc region and an affinity substance are linked by a linker, the linker has a cleavable moiety, and further contains a bioorthogonal functional group between the reactive group for the antibody and the cleavable moiety. The bioorthogonal functional group is as described above. Preferably, the bioorthogonal functional group includes an azide group, an alkyne residue (preferably a cyclic group having a triple bond between carbon atoms which may be substituted by a substituent as described above), a tetrazine residue, an alkene residue, a thiol group, a maleimide residue, a furan residue, and a halocarbonyl residue. [In the formula, R represents the reactive group, L ５ represents a fifth linker, L ６ represents a sixth linker, B represents a group containing a bioorthogonal functional group, CLE represents a cleavable moiety, and A represents the affinity substance. ] The reaction using compound (Ib) (steps (II) and (III)) is shown in Figure 4. As an example of compound (Ib), a compound of the following formula (Ib-1) can be mentioned. [In the formula, X represents a leaving group, W １ , W ２ and W ３ each independently represent an oxygen atom or a sulfur atom, L ７ represents a seventh linker, L ８ represents an eighth linker, B represents a group containing a bioorthogonal functional group, V represents an oxygen atom or a sulfur atom, A represents an affinity substance containing first and second affinity moieties having an affinity for the constant region in the heavy chain of the antibody. ] It may be a compound represented thereby or a salt thereof. The definitions, examples, and preferred examples of the leaving group represented by X, the group containing the bioorthogonal functional group represented by B, and the affinity substance represented by A are as described above. W １ , W ２and W ３ each independently represents an oxygen atom or a sulfur atom. Preferably, W １ , W ２ and W ３ may be an oxygen atom. L ７ The 7th linker represented by, and L ８ The 8th linker represented by may be the same or different divalent groups. The divalent group may or may not be substituted. Examples of the divalent group include those described above. Examples of the substituent when the divalent group is substituted include those described above. In a specific embodiment, the total number of atoms constituting the main chain in the 7th linker and the 8th linker may be 2 to 10. Such a total number of atoms may be 3 or more, or 4 or more. Such a total number of atoms may be 9 or less, 8 or less, or 7 or less. More specifically, such a total number of atoms may be 3 to 9, 4 to 8, or 4 to 7. The number of atoms constituting the main chain in the 7th linker and the 8th linker may each be 1 to 9. Such a number of atoms may be 2 or more, or 3 or more. Such a number of atoms may be 8 or less, 7 or less, or 6 or less. More specifically, such a number of atoms may be 2 to 8, 3 to 7, or 3 to 6. V represents an oxygen atom or a sulfur atom. Preferably, V may be a sulfur atom. The reactions using compound (Ib-1) (Steps (II) and (III)) are shown in Figure 5. The production of the above series of compounds or their salts can be carried out by reacting an affinity substance with a partial compound containing a reactive group against an antibody. For example, such a reaction can be carried out in a suitable organic solvent system (e.g., CH ２ Cl ２In an organic solvent containing an alkyl halide such as (e.g., methyl halide) and an amine such as triethylamine, it can be carried out at an appropriate temperature (e.g., about -10 to 30 °C). The reaction time is, for example, 1 minute to 20 hours, preferably 10 minutes to 15 hours, more preferably 20 minutes to 10 hours, and even more preferably 30 minutes to 8 hours.

[0213] Confirmation of the formation of the above series of compounds or salts thereof depends on the specific raw materials and the molecular weights of the products. For example, it can be carried out by electrophoresis, chromatography (e.g., gel filtration chromatography, ion exchange chromatography, reverse phase column chromatography, HPLC), NMR, or mass spectrometry. Such compounds or salts thereof can be appropriately purified by any method such as chromatography (e.g., the above-mentioned chromatography and affinity chromatography). The reaction between Fc and the compound represented by formula (Ia) or formula (Ib) is not particularly limited, but it can be easily carried out by mixing Fc and the compound represented by formula (Ia) or formula (Ib) in a solution. After the reaction, it is preferable to remove the unreacted compound as appropriate. Thereby, an Fc-compound (Ia) complex or an Fc-compound (Ib) complex is formed. <Step (III): A step of subjecting the Fc-compound (Ia) complex or the Fc-compound (Ib) complex to a cleavage treatment with the cleavable moiety to form an Fc region that does not contain the affinity substance and into which a bioorthogonal functional group is introduced> Examples of the cleavage treatment include (a) treatment with one or more substances selected from the group consisting of an acidic substance, a basic substance, a reducing agent, an oxidizing agent, and an enzyme as described above, (b) treatment with a physicochemical stimulus such as light, or (c) incubation when using a cleavable linker containing a self-cleavable cleavable moiety. For these cleavage treatments, reference can also be made to International Publication No. WO2019 / 240287, International Publication No. WO2019 / 240288, International Publication No. WO2020 / 009165, and International Publication No. WO2020 / 090979. Such cleavage reactions can be appropriately carried out under conditions (mild conditions) that cannot cause denaturation and degradation of proteins (e.g., cleavage of amide bonds). For example, such mild conditions are as described above. Also, when the cleavage site is an ester (e.g., a normal ester or another ester such as a thioester), the cleavage reaction can be carried out by incubating in a hydroxylamine hydrochloride solution (e.g., pH 4.0 - 8.0, 10 mM - 10 M) for an appropriate time (e.g., 1 hour) (e.g., Vance, N. et al., Bioconjugate Chem. 2019, 30, 148 - 160). Confirmation of the production of an antibody or a salt thereof that does not contain the affinity substance obtained by the cleavage reaction depends on the specific raw materials and the molecular weight of the product. For example, it can be carried out by electrophoresis, chromatography (e.g., gel filtration chromatography, ion exchange chromatography, reverse phase column chromatography, HPLC), or mass spectrometry. Confirmation of the site selectivity can be carried out by peptide mapping as described above. Confirmation of the number of introduced affinity substances can be carried out by mass spectrometry (the DAR calculator (software from Agilent) can be used in combination). The affinity substance-modified antibody or a salt thereof can be appropriately purified by any method such as chromatography (e.g., the chromatography described above and affinity chromatography). Thereby, a bioorthogonal functional group can be bound to the side chain functional group of a specific amino acid of one polypeptide constituting the Fc region. In addition, by reacting this bioorthogonal functional group with a compound containing another bioorthogonal functional group, the latter bioorthogonal functional group may be used as a bioorthogonal functional group that reacts with the functional group on the cell surface. <Modification with a functional substance> When the Fc - cell region complex has a functional substance introduced via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions of the other of the two antibody Fc - constituting polypeptides (the polypeptide that does not bind to cells), further, in the antibody Fc region, a step of introducing a functional substance into a functional group in the side chain of a specific amino acid residue present at one or more positions of the other of the two antibody Fc - constituting polypeptides is included. In this case, in step (II), the reaction of the Fc region with compound (Ia) or compound (Ib) may be carried out twice using compound (Ia) or compound (Ib) containing different types of bio - orthogonal functional groups, with one used for cell binding and the other used for binding of the functional substance. Thereby, a compound (Ia) - Fc - compound (Ia) complex or a compound (Ib) - Fc - compound (Ib) complex can be obtained. Note that a compound (Ia) - Fc - compound (Ib) complex may also be used. After such a compound - Fc - compound complex is cleaved with a cleavable moiety to obtain a modified Fc in which two types of bio - orthogonal functional groups are each bound to the respective Fc - constituting polypeptide, before reacting with cells in step (V), a functional substance bound to a functional group that reacts with the bio - orthogonal functional group can be reacted with one of the bio - orthogonal functional groups to introduce the functional substance into one of the polypeptides constituting the Fc region. Then, by reacting this with cells, a cell - Fc - functional substance complex, that is, an Fc - cell complex in which the Fc modified with the functional substance or an antibody or Fc fusion protein containing the same is bound to the cell, can be obtained. The reactions using compound (Ia) (steps (II) (reactions 1, 2) and step (III) (reaction 3)) are shown in FIG. 6. By cleavage with the cleavable moiety, the affinity substance is removed and a modified Fc (VIa) in which two types of bio - orthogonal functional groups are each bound to the respective Fc - constituting polypeptide is obtained. Thus, a functional substance can be introduced into one of the two types of bio - orthogonal functional groups B Ｌ and B Ｒ and the other can be used for cell introduction. The reactions using compound (Ib) (Step (II) (Reactions 1 and 2) and Step (III) (Reaction 3)) are shown in Fig. 7. By cleavage with the cleavable moiety, the affinity substance is removed, and a modified Fc (VIb) in which two types of bioorthogonal functional groups are attached to their respective Fc constituent polypeptides is obtained. Thus, a functional substance can be introduced into one of the two types of bioorthogonal functional groups B Ｌ and B Ｒ and the other can be used for cell introduction. <Step (IV): Step of preparing cells having a functional group reactive with a bioorthogonal functional group on the surface> As the cells, the cells as described above can be used. The functional group reactive with the bioorthogonal functional group can be appropriately selected depending on the type of the bioorthogonal functional group and is not particularly limited. For example, for an azide group, an alkyne residue, ortho-phosphane benzoic acid, etc. can be mentioned, and for a thiol group, a maleimide residue, an alkene residue, an alkyne residue, a haloamide residue, a haloketone residue, etc. can be mentioned. For a tetrazine residue, norbornene, isonitrile, BCN (bicyclo [6.1.0]nonyne) can be mentioned. Similarly, for an alkyne residue, an azide group, and for a maleimide residue, a thiol group. The combination of the bioorthogonal functional group and the functional group reactive with the bioorthogonal functional group may be reversed. When the cell has a functional group on its surface that reacts with a bioorthogonal functional group, the cell can be used as it is. However, usually, it is preferable to modify the cell surface to introduce a functional group that reacts with a bioorthogonal functional group on the cell surface. For example, cell surface modification using enzymes (e.g., GlcNAc-tagging (Glycocalyx Tagging) using O-GlcNAcase (OGA) and N-acetylglucosaminyltransferase (OGT), HaloTag Technology using haloalkane dehalogenase, Sortagging (Sortase-mediated Tagging) using Sortase A, Q-Tagging using transglutaminase), introduction of a functional group by modifying the sugar chain on the cell surface, introduction of a functional group into the lipid membrane via a fatty chain, etc. can be used to introduce a functional group that reacts with a bioorthogonal functional group on the cell surface. Also, it is also preferable to react a crosslinkable compound containing a functional group that reacts with a bioorthogonal functional group or a reagent such as Traut's Reagent that can generate a functional group that reacts with a bioorthogonal functional group with functional groups such as thiol groups, amino groups, and carboxyl groups present in proteins on the cell surface. As the crosslinkable compound, known crosslinkable compounds can be used. For example, as crosslinkable compounds that react with thiol groups, maleimide compounds, haloacetic acid compounds, pyridyldisulfide compounds, thiosulfone compounds, vinyl sulfone compounds, etc. can be mentioned. Also, as crosslinkable compounds that react with amino groups, NHS ester compounds, imide ester compounds, pentafluorophenyl ester compounds, hydroxymethylphosphine compounds, etc. can be mentioned. Also, as crosslinkable compounds that react with carboxyl groups, oxazoline compounds, etc. can be mentioned.That is, a compound containing a crosslinkable reactive group such as maleimide, haloacetic acid, pyridyldisulfide, thiosulfone, vinyl sulfone, NHS ester, imide ester, pentafluorophenyl ester, hydroxymethylphosphine, oxazoline, etc., and a functional group that reacts with a bioorthogonal functional group is reacted with a functional group such as a thiol group, amino group, carboxyl group, etc. on the cell surface, whereby cells having a functional group that reacts with a bioorthogonal functional group on the surface can be prepared. In such a compound containing a crosslinkable reactive group and a functional group that reacts with a bioorthogonal functional group, the linker portion connecting the crosslinkable reactive group and the functional group that reacts with the bioorthogonal functional group is a divalent linear hydrocarbon group, a divalent cyclic hydrocarbon group, a divalent heterocyclic group, -C(=O)-, -C(=S)-, -NR １ -, -C(=O)-NR １ -, -NR １ -C(=O)-, -C(=S)-NR １ -, -NR １ -C(=S)-, -O-, -S-, -(O-R ２ ) ｎ -, and -(S-R ２ ) ｍ -, and a group selected from the group consisting of divalent groups derived from substances selected from amino acids, peptides, nucleic acids, sugars, other polymeric substances (e.g., polyethylene glycol), etc., or a group having a main chain structure containing two or more of these groups. The total number of atoms constituting the main chain in the linker portion is not particularly limited, and may be, for example, 1 or more, 2 or more, 5 or more, 10 or more. Such a total number of atoms may be 1000 or less, 500 or less, 300 or less, 200 or less, 100 or less, 50 or less, or 20 or less. <Step (V): A step of introducing the Fc region into the cell surface by reacting the Fc region into which a bioorthogonal functional group has been introduced with the cell, using the bioorthogonal functional group of the Fc region and the functional group that reacts with the bioorthogonal functional group of the cell> The reaction between the Fc region into which a bioorthogonal functional group has been introduced and a cell having a functional group on its surface that reacts with the bioorthogonal functional group is not particularly limited. For example, it can be carried out by adding and mixing the Fc region into which the bioorthogonal functional group has been introduced in a solution such as a culture medium containing cells or physiological saline. After the reaction, it is preferably appropriate to remove the cells and the unreacted Fc region into which the bioorthogonal functional group has been introduced. Thereby, an Fc-cell complex is formed. Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the embodiments of the following examples. Example 1 Synthesis of an antibody into which a fluorescent molecule and an azide group have been introduced one molecule each Example 1-1 Synthesis of an antibody into which AF488 and an azide group have been introduced one molecule each (T-4) Example 1-1-1 Synthesis of Trastuzumab (T-1) into which one molecule of a peptide reagent has been introduced To a 10 mg / mL acetate buffer (50 mM Sodium acetate, pH 5.5) solution of the anti-human HER2 monoclonal antibody Trastuzumab (manufactured by Chugai Pharmaceutical), a dimethylformamide solution of the peptide reagent (P1) described in the prior report (WO2019 / 240287A1) (1 equivalent to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. After the reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva), an antibody (T-1) into which one molecule of the peptide reagent had been introduced was obtained using AKTA pure25 (manufactured by Cytiva). HIC-HPLC analysis was performed according to the prior report (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that one peptide reagent had been introduced. Purification by AKTA pure25 (manufactured by Cytiva) was performed under the following conditions. Column: RESOURCE S (manufactured by Cytiva) Eluent A: 50 mM Sodium acetate, 0.1% tween20 (pH 5.0) Eluent B: 50 mM Sodium acetate, 1 M NaCl, 0.1% tween20 (pH 5.0) Flow rate: 5.0 ml / min Detector: Detected at wavelengths of 215 and 280 nm. Example 1-1-2 Synthesis of Trastuzumab (T-2) into which two molecules of peptide reagent were introduced Subsequently, according to the method described in the prior report (WO2022 / 191283A1), an antibody (T-2) into which peptide reagents (P1) and (P2) were introduced was obtained using a peptide reagent (P2). HIC-HPLC analysis was performed according to the prior report (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that two peptide reagents were introduced. Example 1-1-3 Synthesis of Trastuzumab (T-3) into which one molecule each of a thiol group and an azide group were introduced To the antibody (T-2) into which the peptide reagents (P1) and (P2) obtained in Example 1-1-2 were introduced, a methoxyamine solution was added according to the prior report (WO2022 / 191283A1), and the mixture was shaken at room temperature for 3 hours to obtain an antibody (T-3) into which one molecule each of a thiol group and an azide group were introduced. HIC-HPLC analysis was performed according to the prior report (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that one molecule each of a thiol group and an azide group were introduced. Example 1-1-4 Synthesis of Trastuzumab (T-4) into which one molecule each of AF488 and an azide group were introduced To a 3 mg / mL PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) solution of Trastuzumab (T-3) with one molecule of thiol group and azide group introduced in Example 1-1-3, a dimethylformamide solution of Alexa Fluor 488 C5 Maleimide (Invitrogen) (2.5 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-4) with one molecule of fluorescent molecule introduced. HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of AF488. Example 1-2 Synthesis of Trastuzumab (T-5) with one molecule of Cy5 and one molecule of azide group introduced To a 3 mg / mL PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) solution of Trastuzumab (T-4) with one molecule of thiol group and one molecule of azide group introduced in Example 1-1-3, a dimethylformamide solution of N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 (BroadPharm) (2.5 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-5) with one molecule of Cy5 introduced. HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of Cy5. Comparative Example 1 Synthesis of an antibody with one molecule of Cy5 and multiple azide groups introduced Comparative Example 1-1 Synthesis of an antibody with one molecule of Cy5 and multiple azide groups introduced via lysine residues Comparative Example 1-1-1 Synthesis of Trastuzumab (T-6) with one molecule of thiol group introduced To the antibody (T-1) into which the peptide reagent (P1) obtained in Example 1-1-1 was introduced, a hydroxylamine solution was added according to a previous report (WO2019 / 240287A1), and the mixture was shaken at room temperature for 1 hour to obtain an antibody (T-6) into which one molecule of a thiol group was introduced. HIC-HPLC analysis was performed according to a previous report (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm that the thiol group was introduced. Comparative Example 1-1-2 Synthesis of Trastuzumab (T-7) into which one molecule of Cy5 was introduced To a 3 mg / mL PBSE buffer solution (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) of Trastuzumab (T-6) into which one molecule of a thiol group was introduced, obtained in Comparative Example 1-1-1, a dimethylformamide solution of N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 (BroadPharm) (2.5 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-7) into which one molecule of a fluorescent molecule was introduced. HIC-HPLC analysis was performed according to a previous report (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm that Cy5 was introduced. Comparative Example 1-1-3 Synthesis of Trastuzumab (T-8) into which one molecule of Cy5 and a plurality of azide groups were introduced via a lysine residue To a 3 mg / mL PBS buffer (10 mM Phosphate Buffered Saline (PBS), pH 7.4) solution of Trastuzumab (T-7) with one molecule of Cy5 introduced obtained in Comparative Example 1-1-2, a dimethylformamide solution of 4-azidobenzoic acid N-hydroxysuccinimide ester (7 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-8) with one molecule of Cy5 and multiple azide groups introduced. QTOF-MS analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that 4-5 molecules of azide groups were introduced. Comparative Example 1-2 Synthesis of Trastuzumab (T-9) with Multiple Azide Groups Introduced via One Molecule of Cy5 and Cysteine Residues An equal volume of a dimethylformamide solution of 3-azidopropylamine (20 mM) was added to a commercially available dimethylformamide solution of N-Succinimidyl 3-Maleimidopropionate (20 mM), and the mixture was shaken for 30 minutes to prepare a dimethylformamide solution of Azido-PEG3-Maleimide (10 mM). To a 3 mg / mL solution of Trastuzumab (T-7) with one molecule of Cy5 introduced, obtained in Comparative Example 1-1-2, in PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4), an aqueous solution of Tris(2-carboxyethyl)phosphine (12 equivalents relative to the antibody) was added, and the mixture was shaken at 37 °C for one and a half hours. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva). To the obtained antibody in PBSE buffer, an Azido-PEG3-Maleimide solution (12 equivalents relative to the antibody, in dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-9) with one molecule of Cy5 and multiple azide groups introduced. QOF-MS analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that 7-8 molecules of azide groups were introduced. Example 2 Synthesis of AF488 Antibody-Cell Conjugate Example 2-1 Cell Culture HEL cells (JCRB) were cultured in D-MEM / F12 medium (manufactured by Thermo Fisher Scientific) supplemented with 10% FBS (manufactured by Thermo Fisher Scientific) and 1% Penicillin-Streptomycin (manufactured by Nacalai Tesque). Example 2-2 Synthesis of Antibody-Cell Conjugate After detaching HEL cells by pipetting, the cell count and viability were measured using a Countess Automated Cell Counter (manufactured by Thermo Fisher Scientific). 2.0 × 10 ６HEL cells were sorted, centrifuged (at 6,000 rpm for 15 seconds), and then the supernatant was removed. After adding 1 mL of PBS to the HEL cells for washing, they were centrifuged again to remove the supernatant. 1 mL of 0.1 mg / mL Traut's reagent (Sigma-Aldrich) / PBS was added to the HEL cells and left standing at room temperature for 20 minutes. After centrifuging to remove the supernatant, the process of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain HEL cells with sulfhydryl groups modified on the cell surface. Next, 1 mL of 20 μM dibenzocyclooctyne (DBCO)-PEG4-maleimide (BroadPharm) / PBS was added to the HEL cells and left standing at room temperature for 30 minutes. After centrifuging to remove the supernatant, the process of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain HEL cells with the cell surface modified with DBCO. 0.5 × 10 HEL cells with the cell surface modified with DBCO or unmodified HEL cells were sorted ６ per cell, suspended in 200 μL of D-MEM / F12 medium. 0.33 μM or 1 μM of T-4 was added to each and left standing at 37 °C for 1 hour. After centrifuging to remove the supernatant, the process of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain a complex of antibody and cells. Example 2-3 Evaluation of Antibody-Cell Conjugates 0.2 × 10 ６ The amount of antibody bound to the cells was evaluated by performing flow cytometry analysis of the cells using an Attune NxT Flow Cytometer (Thermo Fisher Scientific). The remaining cells were cultured in 200 μL of D-MEM / F12 + 10% FBS + 1% Penicillin-Streptomycin for 24 hours and then analyzed by flow cytometry in the same manner as above. As shown in Fig. 8, the group in which the T-4 antibody was reacted with the cells modified with DBCO had stronger fluorescence compared to the group reacted with the cells not modified with DBCO, indicating that the antibody could be bound with higher efficiency. Also, 24 hours after the reaction, while the fluorescence was lost in most cells in the mixture of cells not modified with DBCO and the T-4 antibody, most cells in the group in which the T-4 antibody was reacted with the cells modified with DBCO retained fluorescence, suggesting that the formation of a covalent bond between the DBCO group on the cell surface and the azide group of the antibody contributed to the high stability of the antibody modification. Example 3 Synthesis of Cy5 Antibody-Cell Conjugate and Evaluation of HER2 Binding Ability Example 3-1 Synthesis of Antibody-Cell Conjugate HEL cells with their cell surfaces modified with DBCO were aliquoted at 2 × 10 ６ cells each and suspended in 200 μL of D-MEM / F12 medium. 1 μM of T-5 was added and left standing at 37 °C for 1 hour. After centrifugation to remove the supernatant, 1 mL of PBS was added for washing, and the process of centrifuging to remove the supernatant was repeated twice to obtain a complex of the antibody and the cells. Example 3-2 Evaluation of HER2 Binding of Antibody-Cell Conjugate 0.3 × 10 ６ The cells were subjected to HER2 binding evaluation, and the remaining cells were cultured in 200 μL of D-MEM / F12 + 10% FBS + 1% Penicillin-Streptomycin for 48 hours and then subjected to the same HER2 binding evaluation as above. 0.3 × 10 ６ To the cells, 45 μL of FACS buffer (PBS + 1% FBS) supplemented with 2% of Human TruStain FcX Fc Receptor Blocking Solution (BioLegend) was added and reacted on ice for 10 minutes. Biotin Labeling Kit - NH ２Human recombinant HER2-Fc (R&D Systems) biotinylated at the Institute of Homologous Chemistry was added to the cells to a concentration of 10 μg / mL and reacted on ice for 20 minutes. The cells were washed three times with FACS buffer, and 100 μL of FACS buffer containing 20 μg / mL of Streptavidin-Alexa Fluor 488 (Thermo Fisher Scientific) was added and reacted on ice for 20 minutes... The cells were washed three times with FACS buffer and suspended in 500 μL of FACS buffer. By performing flow cytometry analysis using an Attune NxT Flow Cytometer (Thermo Fisher Scientific), the amount of antibody bound to the cells and the binding amount of HER2-Fc were evaluated. In addition, fluorescence microscopy observation was performed on the cells that had undergone the same HER2 binding treatment using a BZ-X700 (Keyence). As shown in Figure 9, for the cells conjugated with the T-5 antibody, fluorescence derived from Cy5 modified on the antibody and Streptavidin-Alexa 488 was detected from the cells, confirming that the cells were modified with the antibody and that human recombinant HER2-Fc was bound. On the other hand, neither fluorescence was observed in the cells modified with DBCO and the unmodified cells, indicating that HER2-Fc was not bound. From the above results, it was clarified that the T-5-cell conjugate acquired the HER2 binding ability derived from the antibody. In addition, it was confirmed that the HER2 binding ability was retained even after 48 hours. Also, as shown in Figure 10, for the cells conjugated with the T-5 antibody in fluorescence microscopy observation, since fluorescence derived from Alexa Fluor 488 was observed on the cell membrane, it was confirmed that HER2 was bound to the antibody conjugated to the cells. Example 4 Comparison between the conjugate and non-conjugate of antibody and cell Example 4-1 Synthesis of antibody-cell conjugate and preparation of non-conjugate The synthesis of the antibody-cell conjugate was performed as follows. HEL cells with their cell surfaces modified with DBCO were dispensed at 2 × 10 ６ cells each, and suspended in 200 μL of D-MEM / F12 medium. 1 μM was added, and the mixture was allowed to stand at 37 °C for 1 hour. After centrifugation to remove the supernatant, 1 mL of PBS was added for washing, and the process of centrifuging to remove the supernatant was repeated twice to obtain a complex of the antibody and the cells. The unconjugated body was prepared by performing the above operations on HEL cells whose cell surfaces were not modified with DBCO. Example 4-2 Evaluation of HER2 Binding of Antibody-Cell Conjugate and Unconjugated Body Similar to the above, the HER2 binding ability of each antibody-cell conjugate was evaluated by flow cytometry analysis. As shown in Fig. 11, the proportion of cells showing the fluorescence of Streptavidin-Alexa Fluor 488 was higher in the antibody-cell conjugate group than in the unconjugated group. Also, by calculating (fluorescence intensity of Streptavidin-Alexa Fluor 488) / (fluorescence intensity of Cy5) in each group, the amount of HER2 binding per antibody bound to the cells was calculated. As a result, the conjugate group showed a value more than 6 times higher. From this, it became clear that by conjugating the antibody to the cells, the antigen-binding ability of the antibody was maintained higher than that of the unconjugated body. Example 5 Comparison of Various Azide-Modified Antibody-Cell Conjugates Example 5-1 Synthesis of Antibody-Cell Conjugate HEL cells with their cell surfaces modified with DBCO were dispensed at 2 × 10 ６ cells each, and suspended in 200 μL of D-MEM / F12 medium. 0.3 μM or 1 μM of T-5, T-8 or T-9 was added, and the mixture was allowed to stand at 37 °C for 1 hour. After centrifugation to remove the supernatant, 1 mL of PBS was added for washing, and the process of centrifuging to remove the supernatant was repeated twice to obtain a conjugate of the antibody and the cells. Example 5-2 Evaluation of HER2 Binding of Antibody-Cell Conjugate In the same manner as described above, the HER2 binding of each antibody-cell conjugate was evaluated using flow cytometry. As shown in Fig. 12A, for all cells conjugated with the modified antibodies, fluorescence derived from Cy5 modified on the antibody and fluorescence derived from Streptavidin-Alexa 488 were detected from the cells. From this result, it was confirmed that the cells were modified with the antibody and that human recombinant HER2-Fc was bound. In each group, the amount of HER2 bound per antibody bound to the cells was calculated by calculating (fluorescence intensity of Streptavidin-Alexa Fluor 488) / (fluorescence intensity of Cy5). As a result, as shown in Fig. 12B, the antibody-cell conjugate modified with T-5 showed a value more than 6 times higher than that of the antibody-cell conjugate modified with T-8 or T-9. From this, by conjugating a site-specifically modified antibody to cells, an antibody-cell conjugate having a higher antigen-binding ability than an antibody-cell conjugate synthesized using an antibody in which lysine residues on the antibody were randomly modified or an antibody in which sulfhydryl groups generated by reducing disulfide bonds on the antibody were modified was obtained. Example 6 Synthesis of Cy5 antibody-T cell conjugate and evaluation of HER2 binding ability Example 6-1 Cultivation of T cells A 24-well plate was coated with DPBS supplemented with 5 μg / mL anti-CD3 antibody (Thermo Fisher Scientific) and 25 μg / mL RetroNectin (Takara Bio). The plate was washed three times with DPBS, and 6×10 ４　 cells / well of T cells were added and cultured in a medium supplemented with Optimizer (Thermo Fisher Scientific) and IL-2 (PeproTech). Example 6-2 Synthesis of T antibody-cell conjugate After collecting the T cells, the cell number and viability were measured using a Countess Automated Cell Counter (Thermo Fisher Scientific). 2.5×10７ T cells of the cells were sorted, centrifuged (at 6,000 rpm for 15 seconds), and then the supernatant was removed. After adding 1 mL of PBS to the T cells for washing and then centrifuging to remove the supernatant, 1 mL of 0.1 mg / mL Traut's reagent (Sigma-Aldrich) / PBS was added to the T cells and allowed to stand at room temperature for 20 minutes. After centrifuging to remove the supernatant, the step of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain T cells with sulfhydryl groups modified on the cell surface. Next, 1 mL of 20 μM dibenzocyclooctyne (DBCO)-PEG4-maleimide (BroadPharm) / PBS was added to the T cells and allowed to stand at room temperature for 30 minutes. After centrifuging to remove the supernatant, the step of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain T cells with the cell surface modified with DBCO. T cells with the cell surface modified with DBCO or unmodified T cells were taken at 0.5×10 ６ cells each and suspended in 200 μL of medium for T cells. 0.33 μM or 1 μM of T-4 was added to each and allowed to stand at 37 °C for 1 hour. After centrifuging to remove the supernatant, the step of adding 1 mL of PBS for washing and then centrifuging to remove the supernatant was repeated twice to obtain a complex of the antibody and the cells. Example 6-3 Evaluation of Antibody-Cell Conjugate 0.2 × 10 ６ The amount of antibody bound to the cells was evaluated by performing flow cytometry analysis using an Attune NxT Flow Cytometer (Thermo Fisher Scientific). As shown in Figure 13, the group in which the T-4 antibody was reacted with the cells modified with DBCO had stronger fluorescence compared to the group reacted with the cells not modified with DBCO, indicating that the antibody could be bound with higher efficiency. <Reference Example> Hereinafter, as a reference example, a method for synthesizing a compound containing a bioorthogonal functional group and an affinity substance using an affinity substance containing two affinity peptides, and a method for introducing a bioorthogonal functional group into only one of the polypeptides derived from the heavy chain constant region constituting the Fc region of an antibody using the compound will be described. By using an antibody in which a bioorthogonal functional group is introduced into only one of the polypeptides derived from the heavy chain constant region constituting the Fc region thus obtained, the antibody or Fc fusion protein can also be chemically bound to the cell surface via a linker introduced into the functional group in the side chain of a specific amino acid residue present at one or more positions of the polypeptide derived from the Fc-constituting heavy chain constant region to obtain an Fc-cell complex. (Reference Example 1) Design of Affinity Substance and Secretory Expression of Affinity Substance in C. glutamicum (1-1) Outline of Design of Affinity Substance In the present invention, it is necessary to design an affinity substance containing two or more sites capable of binding to an antibody in the molecule. That is, the affinity substance is A) A molecule containing two or more sites capable of binding to an antibody (and a linker for linking these sites if necessary) needs to be designed as such. Next, in the present invention, in order to be able to modify the immunoglobulin unit, it is preferable to bind a compound having a reactive group for the immunoglobulin unit to the affinity substance. Further, in order to remove the affinity substance after modification of the immunoglobulin unit, it is preferable to contain a cleavable moiety between the reactive group and the affinity substance. Furthermore, in order to achieve specific binding of the compound to a specific site in the affinity substance, it is preferable to design so that there is only one site in the affinity substance that can react with the compound. Therefore, when using an affinity polypeptide as the affinity substance and binding the affinity polypeptide and the compound via the amino group in the side chain of the lysine residue (K) in the affinity polypeptide, it is preferable to design the affinity polypeptide so that there is only one lysine residue in the affinity polypeptide. Thus, the affinity polypeptide was designed as follows. B) The polypeptide contains only 1 residue of K C) By making the N-terminal amino acid Q (glutamine), it is pyroglutamylated to convert the N-terminal amino group to an amide. According to the above rules A), B) and C), polypeptide-like affinity substances were designed as follows (a)-(h). (1-2) Preparation of affinity substances The following affinity substances were prepared. (a) QET-Z34CM-PA32-Fc3K QET-FNMQCQRRFYEALHDPNLNEEQRNARIRSIREEEC-GGAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPGG-RGNCAYHKGQIIWCTYH-NH ２ (SEQ ID NO: 17) (b) QET-Z34CM-PA48-Fc3K QET-FNMQCQRRFYEALHDPNLNEEQRNARIRSIREEEC-GGAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPGG-RGNCAYHKGQIIWCTYH-NH ２ (SEQ ID NO: 18) (c) QET-Fc3K-PA32-Z34CM QETRGNCAYHKGQIIWCTYH-GGAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPGG-FNMQCQRRFYEALHDPNLNEEQRNARIRSIREEEC-NH ２ (SEQ ID NO: 19) (d) QET-Fc3K-PA48-Z34CM QETRGNCAYHKGQIIWCTYH-GGAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPAA-PAAPAPGG-FNMQCQRRFYEALHDPNLNEEQRNARIRSIREEEC-NH ２ (SEQ ID NO: 20) (e) QET-Fc3K-PA32-ProAR QETRGNCAYHKGQIIWCTYH-GGAA PAA PAPA AAP AAP APAA PAA PAPA AAP AAP APAA PAA PAPA GG-FNREQQNAFYEILHLPNLNE EQRNGFIQSLRDDPSQSANLLA EA-NH ２ (SEQ ID NO: 21) (f) QET-Fc3K-PA48-ProAR QETRGNCAYHKGQIIWCTYH-GGAA PAA PAPA AAP AAP APAA PAA PAPA AAP AAP APAA PAA PAPA GG-FNREQQNAFYEILHLPNLNE EQRNGFIQSLRDDPSQSANLLA EA-NH ２ (SEQ ID NO: 22) (g) QET-ProAR-PA32-Z34CK QET-FNREQQNAFYEILHLPNLNE EQRNGFIQSLRDDPSQSANLLA EA-GGAA PAA PAPA AAP AAP APAA PAA PAPA AAP AAP APAA PAA PAPA GG-FNKQCQRRFYEA LHDPNLNE EQRNA RIRSIREE C-NH ２ (SEQ ID NO: 23) (h) QET-ProAR-PA48-Z34CK QET-FNREQQNAFYEILHLPNLNE EQRNGFIQSLRDDPSQSANLLA EA-GGAA PAA PAPA AAP AAP APAA PAA PAPA AAP AAP APAA PAA PAPA GG-FNKQCQRRFYEA LHDPNLNE EQRNA RIRSIREE C-NH ２ (SEQ ID NO: 24) (1-3) Expression of the affinity substance The expression of these polypeptide - like affinity substances was examined using Corynex (registered trademark). In the expression using Corynex (registered trademark), the CspB fusion method (WO2013 / 062029) was utilized, that is, a base sequence encoding an amino acid sequence containing the N - terminal 3 residues Gln - Glu - Thr (QET) of the CspB mature protein was inserted between the base sequence encoding the signal peptide and the base sequence encoding the target polypeptide, thereby taking advantage of the technology that can improve the secretion production amount of the target polypeptide. Also, since the N - terminal of the CspB tag is Q, there is an advantage that after signal sequence cleavage, the first residue Q can be pyroglutamylated to protect the N - terminal amino group. That is, in addition to the above rules A), B), and C), considering the following rule D) is effective for improving the expression of the affinity polypeptide using Corynex (registered trademark). D) Add 3 residues of QET to the N - terminal to improve the secretion efficiency with Corynex (registered trademark) Hereinafter, reference examples of the expression examination using Corynex (registered trademark) will be described. (1 - 4) Construction of each secretion - expression plasmid of QET - Z34CM - PA32 - Fc3K, QET - Z34CM - PA48 - Fc3K, QET - Fc3K - PA32 - Z34CM, QET - Fc3K - PA48 - Z34CM, QET - Fc3K - PA32 - ProAR, QET - Fc3K - PA48 - ProAR, QET - ProAR - PA32 - Z34CK, and QET - ProAR - PA48 - Z34CK As the affinity polypeptide, eight amino acid sequences of QET - Z34CM - PA32 - Fc3K, QET - Z34CM - PA48 - Fc3K, QET - Fc3K - PA32 - Z34CM, QET - Fc3K - PA48 - Z34CM, QET - Fc3K - PA32 - ProAR, QET - Fc3K - PA48 - ProAR, QET - ProAR - PA32 - Z34CK, and QET - ProAR - PA48 - Z34CK were designed respectively, and the base sequences encoding these polypeptides were designed considering the codon usage frequency of C. glutamicum. Furthermore, the following expression cassettes were designed respectively to enable secretion - expression by C. glutamicum. QET-Z34CM-PA32-Fc3K was secreted and expressed as a fusion protein of the signal peptide of 30 amino acid residues of CspB derived from C. glutamicum ATCC13869 strain, the N-terminal 3 amino acid residues QET of the mature protein of CspB derived from the same strain, and Z34CM-PA32-Fc3K (hereinafter referred to as "CspBss-QET-Z34CM-PA32-Fc3K"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Z34CM-PA32-Fc3K are shown in SEQ ID NO: 25 and SEQ ID NO: 26, respectively. Nucleotide sequence encoding CspBss-QET-Z34CM-PA32-Fc3K atgtttaac aaccgtatcc gcactgcaag ctctcgctgg tgcaatcgca atctccacca gcacttccgg cgtagctatc ccaagcatcg ctccaggaag accttcaaca tgcagtgccaa cggcgctttt acgaagcgct ccacgatccc aacctgaacg aggagacagc gtaacgcgcg catcgctcca tccgtgaaga atgtggcggt gctgccccc tgctgccccc agcaccggca gcaccgctgg cacccagctc cggcagctcc agctgcaccg gcccccagcc gctccagcag cgccagctcc cggaagtcga ggcaattgcc ctatcacaag gggcagatca tctggtgcat cttaccatta a (SEQ ID NO: 25) Amino acid sequence of CspBss-QET-Z34CM-PA32-Fc3K MFNNRIRTAALAGAIAISTAAASGVAI PAF AQETFNMQCQRRFYEALHDPNLNEEQR NARIRSIREE CGGGAAPAAAP AAP AAP AAP AAP AAP AAP AAP GGRGNCAYHKGQIIWCTYH (SEQ ID NO: 26) QET-Z34CM-PA48-Fc3K was secreted and expressed as a fusion protein of the 30 amino acid residues of the signal peptide of CspB from C. glutamicum ATCC13869 strain, the 3 amino acid residues QET at the N-terminus of the mature protein of CspB from the same strain, and Z34CM-PA48-Fc3K (hereinafter referred to as "CspBss-QET-Z34CM-PA48-Fc3K"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Z34CM-PA48-Fc3K are shown in SEQ ID NO: 27 and SEQ ID NO: 28, respectively. Nucleotide sequence encoding CspBss-QET-Z34CM-PA48-Fc3K atgtttaacaaaccgtatccgcactgcagctctcgctggtgcaatcgcaatctccaccgcaagcttccggcgtagctatcccagcatttcgctcaggagaacctttaacatgcagtgccaaacgtcgtctttttacgaagcgctgcacgatcccagcctgaacgaaggaaacagcgcaatgcgcgaaatacgctccattcgcgaggaaatgtggcggagcagctcccgcggcctcctgctccagcagcgcctgctgctccctgcccccctgcggcacctgcagcacctgcaccagcagctccggcagcacccagctccagctgcaccccgcgcccccagctcctgcagcgcctgccggctccggcccccccgagggtagggggcaactgcgcatatcacaagggggcagataatctggtgcatcttatcactaa (SEQ ID NO: 27) Amino acid sequence of CspBss-QET-Z34CM-PA48-Fc3K MFNNRIRTAALAGAIAISTAAASGVAI PAF AQETFNMQCQRRFY EALHDPNLNEEQR NARIRSIREE CGGGAAPAA PAPAAPAAA PAPAAPAAA PAPAAPAAA PAPAAPAAA PAPAAPAAA PAPAAPGGRGN CAYHKGQIIWCTYH (SEQ ID NO: 28) QET-Fc3K-PA32-Z34CM was secreted and expressed as a fusion protein of 30 amino acid residues of the signal peptide of CspB derived from Corynebacterium glutamicum ATCC13869 strain, the N-terminal 3 amino acid residues QET of the mature protein of CspB derived from the same strain, and Fc3K-PA32-Z34CM (hereinafter referred to as "CspBss-QET-Fc3K-PA32-Z34CM"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Fc3K-PA32-Z34CM are shown in SEQ ID NO: 29 and SEQ ID NO: 30, respectively. Nucleotide sequence encoding CspBss-QET-Fc3K-PA32-Z34CM atgtttaacaccaatcctgcactgcaagctctcgctggtgcaatcgcaatctccaccgcaagcttccggcgtagctatcccagcatttcgctcaggagaacccgtggcaactgtgccctaccacaaggcccagatcatctggtgcatgtaccacggaggtgccgcgccctgccgccaccctgccctcagctgctccccgctgcccccctgcaccagctgccgccagcagcaccagctccagcggcaccctgcagcaccggcaccctggtggcttcaacatgcagtcgccagacgacgctttacgagggctctgcacgatccgaacctcaacgaggaaacagcgcgaatgcccgatatccggtccatcaggaggaaatgctaa (SEQ ID NO: 29) Amino acid sequence of CspBss-QET-Fc3K-PA32-Z34CM MFNNRIRTAALAGAIAISTAAASGVAIAPAF AQETRGNCAYHKGQIIWCTYHGG AAPAAAPAP AAPAAAPAP AAPAAAPAP AAPAAAPAP GGGFNMQCQRRFYEALHDPNLNEEQRNARIRSIREE C (SEQ ID NO: 30) QET-Fc3K-PA48-Z34CM was secreted and expressed as a fusion protein of the 30 amino acid residues of the signal peptide of CspB derived from Corynebacterium glutamicum ATCC13869 strain, the 3 amino acid residues QET at the N-terminus of the mature protein of CspB derived from the same strain, and Fc3K-PA48-Z34CM (hereinafter referred to as "CspBss-QET-Fc3K-PA48-Z34CM"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Fc3K-PA48-Z34CM are shown in SEQ ID NO: 31 and SEQ ID NO: 32, respectively. Nucleotide sequence encoding CspBss-QET-Fc3K-PA48-Z34CM atgtttaac aaccgtatcc gcactgcaag ctctcgctgg tgcaatcgca atctccacca gcacttccgg cgtagctatc cccagcatcg ctccaggaag acccgtggca attgccgcta tcacaagggt cagatcattt ggtgcaccta ccatggtggt gcaagcacca gctgcccccgg ctccggctgc gccctgctgc accctgcgcc agctgcacct gcagcaccgg cacctgctgc tccagcagca cccgctcctg cagctccccg ctgcccccag ctccagcggc gccctgcggc gccagcacct ggaagggttc aacatgcagt gccaaacgtc gctttttacg agggctttgc atgatcctaa cttgaacgag gaacagcgga atgcgcggat acgctccata cgcgaaagaa tgttaa (SEQ ID NO: 31) Amino acid sequence of CspBss-QET-Fc3K-PA48-Z34CM MFNNRIRTAALAGAIAISTAAASGVAI PAF AQETRGNCAYHKGQIIWCTYHGGAA P A A P A P A A P A A P A P A A P A A P A P A A P A A P A P A A P A A P A P GGFNMQCQRRFY EALHDPNLNEEQRNARIRSIREE C (SEQ ID NO: 32) QET-Fc3K-PA32-ProAR was secreted and expressed as a fusion protein of 30 amino acid residues of the signal peptide of CspB from Corynebacterium glutamicum ATCC13869 strain, the N-terminal 3 amino acid residues QET of the mature protein of CspB from the same strain, and Fc3K-PA32-ProAR (hereinafter referred to as "CspBss-QET-Fc3K-PA32-ProAR"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Fc3K-PA32-ProAR are shown in SEQ ID NO: 33 and SEQ ID NO: 34, respectively. Nucleotide sequence encoding CspBss-QET-Fc3K-PA32-ProAR atgtttaacaccaatcaccgcatgctagctctcgctggtgcaatcgcaatctccaccgcaagcttccggcgttagctatcccagcatttcgctccaggaacccgcggcaactgtgccctaccacaaggagagcatcttggtgcatctatcacggtggtggcggctccggctgctccagcgccagcagctccccgctgcaccagccccagcggcacctgccgccacctgcaccctgcagctccagcggctccccgaccgggaggctttaccgcgaacagcagagacgccctttacgagattctccatctgcccaactctcaacgaggaagcaacggaatggcttcattccagagcttgctgtacgatcctgtctcaatccgccaatctgcttgccggaagccaaa (SEQ ID NO: 33) Amino acid sequence of CspBss-QET-Fc3K-PA32-ProAR MFNNRIRTAAALAGAIAISTAAASGVAIAPAFAQETRGNCAYHKGQIIWCTYHGGAAPAAAPAPAPAPAPAPAPAPGGFNREQQNAFYEILHLPNLNEEQRNGFIQSLRDDPSQSANLLAEA (SEQ ID NO: 34) QET-Fc3K-PA48-ProAR was secreted and expressed as a fusion protein of the 30 amino acid residues of the signal peptide of CspB derived from Corynebacterium glutamicum ATCC 13869 strain, the 3 amino acid residues QET at the N-terminus of the mature protein of CspB derived from the same strain, and Fc3K-PA48-ProAR (hereinafter referred to as "CspBss-QET-Fc3K-PA48-ProAR"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-Fc3K-PA48-ProAR are shown in SEQ ID NO: 35 and SEQ ID NO: 36, respectively. Nucleotide sequence encoding CspBss-QET-Fc3K-PA48-ProAR atgtttaacaccaatcctgcactgcaagctctcgctggtgcaatcgcaatctccaccgcaagcttccggcgtagctatcccagcatttcgctccaggaacccgtgggaactgcgcgtaccataaggccagatcatctggtgcatctatcatggcgggtgctgccgccagcctgggctcctgccgctccagccgctgccagcccccagcagctccagcagcacctgcacctgctgcacccagcgggctccagctcctgcggcacccgctgcacccggcacccagccgctccggctgcccccagctccgggtggctttaatccgcgaacagcagaaacgctttctacgagatactccacctttcccaacctgaacgaggaagcagcgaaacggcttcattccagtctctttcgcgatgatccatcccagagcgctaatttgcttgcaagaagcgaaa (SEQ ID NO: 35) Amino acid sequence of CspBss-QET-Fc3K-PA32-ProAR MFNNRIRTAAALAGAIAISTAAASGVAI PAFAQETRGNCAYHKGQIIWCTYHGG AAPAAAPAAAPAAAPAAAPAAAPAA AAPAAAPAAAPAAAPAAAPGGGFNR EQQNAFYEILHLPNLNE EQRNGFIQSLRDDPSQSANLLAEA (SEQ ID NO: 36) QET - ProAR - PA32 - Z34CK was secreted and expressed as a fusion protein of the 30 - amino - acid residue signal peptide of CspB from Corynebacterium glutamicum ATCC13869 strain, the N - terminal 3 - amino - acid residue QET of the mature protein of CspB from the same strain, and ProAR - PA32 - Z34CK (hereinafter referred to as "CspBss - QET - ProAR - PA32 - Z34CK"). The nucleotide sequence and amino - acid sequence encoding the designed CspBss - QET - ProAR - PA32 - Z34CK are shown in SEQ ID NO: 37 and SEQ ID NO: 38, respectively. The nucleotide sequence encoding CspBss - QET - ProAR - PA32 - Z34CK atgtttaac aaccgtatcc gcactgcaag ctctcgctgg tgcaatcgca atctccacca gccttccgga cgtagctatc cccagcatcg ctccaggaag acctttaacc gcgagacagc aggaacgctt ctacgagatc ctgcatctcc ccaatctgaa cgaagagcag gaggaatggc tttatccaga gccttctgta cgatccgtcg caatctgcca acctgttggc ggagagctgg aggttgccgc gccagcggca ccagcaccag ctgcaccggc tgctcccgcg cctgccgcaa ccagccgctc ctgcccccag cagctccggc agctcctgca cctggtggct tcaacaagca gtgccaacgt cgcttttatg aagcgctaca cgatccccaa cctcaacgag gaacagcgcg aatgcgcgaa tccggtccat tcgagaagag ctttaa (SEQ ID NO: 37) The amino - acid sequence of CspBss - QET - ProAR - PA32 - Z34CK MFNNRIRTAA LAGAIAISTA ASGVAI PAF AQETFNR EQQNAFYE ILHLPNLNE EQRN GFIQS LRDDPSQSANLLAEAGG AAPAA PAPAA PAPAA PAPAA PAPAA PAPAA PAPAA PAPGG FN KQCQRRFYEA LHDPNLNE EQRNARIRSIREE C (SEQ ID NO: 38) QET-ProAR-PA48-Z34CK was secreted and expressed as a fusion protein of the 30 amino acid residues of the signal peptide of CspB from C. glutamicum ATCC13869 strain, the 3 amino acid residues QET at the N-terminus of the mature protein of CspB from the same strain, and ProAR-PA48-Z34CK (hereinafter referred to as "CspBss-QET-ProAR-PA48-Z34CK"). The nucleotide sequence and amino acid sequence encoding the designed CspBss-QET-ProAR-PA48-Z34CK are shown in SEQ ID NO: 39 and SEQ ID NO: 40, respectively. Nucleotide sequence encoding CspBss-QET-ProAR-PA48-Z34CK atgtttaac aaccgtatcc gcactgcaag ctctcgctgg tgcaatcgca atctccacca gccttccgga gtctatccca gcattcgctc aggagaactt taaccgcaaa cagcagaacg ccttctacga gatcctccat ctgccaaact gaacgaagaa cagcgcaacg gctttatcca gtccctcagg gatcgatcgt ctctagtcgg ccaattttgc tagccaagcg gggaggtgct gctccggcag caccctgcac cagccgccgc ccgctgctcc agcgccggca gctcctgcgg cacccagctc cagcagcacc agcggcctcc agcacctgcc ggcacctgca gctccggctc cctgcaagcc ccccgccgct cctgcgccgg gtgcttcaac aagcagtgcc aacgacgctt ctacgagggc gcttacgatc ccaacctgaa tgaggaagca acggaagtgc ccgatatccg tagcatttcg caagaatgtt aa (SEQ ID NO: 39) Amino acid sequence of CspBss-QET-ProAR-PA48-Z34CK MFNNRIRTAALAGAIAISTAASGVAIAPAFAQETFNRQQNAFYEILHLPNLNEQQRNGFIQSLRDDPSQSANLLAEGGAAAPAAAPAPAAAPAPAAAPAPAAAPAPAAAPAPAAAPAPAAAPAPAAAPAPAAAPAPGGFNKQCQRRFYEALHDPNLNEEQRNAIRSIREEEC (SEQ ID NO: 40) Upstream of the base sequences described in CspBss-QET-Z34CM-PA32-Fc3K, CspBss-QET-Z34CM-PA48-Fc3K, CspBss-QET-Fc3K-PA32-Z34CM, CspBss-QET-Fc3K-PA48-Z34CM, CspBss-QET-Fc3K-PA32-ProAR, CspBss-QET-Fc3K-PA48-ProAR, CspBss-QET-ProAR-PA32-Z34CK, and CspBss-QET-ProAR-PA48-Z34CK, the promoter of the cspB gene derived from C. glutamicum ATCC13869 strain was ligated, and a KpnI site was added to the 5'-side and a BamHI site was added to the 3'-side. Eight expression cassettes of affinity polypeptides were designed and fully synthesized. By inserting the fully synthesized DNA fragment (expression cassette of affinity polypeptide) into the KpnI-BamHI site of pPK4 described in JP-A-9-322774, pPK4_CspBss-QET-Z34CM-PA32-Fc3K, pPK4_CspBss-QET-Z34CM-PA48-Fc3K, pPK4_CspBss-QET-Fc3K-PA32-Z34CM, pPK4_CspBss-QET-Fc3K-PA48-Z34CM, pPK4_CspBss-QET-Fc3K-PA32-ProAR, pPK4_CspBss-QET-Fc3K-PA48-ProAR, pPK4_CspBss-QET-ProAR-PA32-Z34CK, and pPK4_CspBss-QET-ProAR-PA48-Z34CK, which are secretion expression plasmids of affinity polypeptides, were constructed respectively. As a result of determining the base sequence of the inserted fragment, it was confirmed that the expression cassettes of affinity polypeptides as designed were constructed. The determination of the base sequence was performed using BigDye(R) Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems) and 3500xL Genetic Analyzer (Applied Biosystems). (1-5) Secretion expression of affinity polypeptide in C. glutamicum Using the pPK4_CspBss-QET-Z34CM-PA32-Fc3K, pPK4_CspBss-QET-Z34CM-PA48-Fc3K, pPK4_CspBss-QET-Fc3K-PA32-Z34CM, pPK4_CspBss-QET-Fc3K-PA48-Z34CM, pPK4_CspBss-QET-Fc3K-PA32-ProAR, pPK4_CspBss-QET-Fc3K-PA48-ProAR, pPK4_CspBss-QET-ProAR-PA32-Z34CK, and pPK4_CspBss-QET-ProAR-PA48-Z34CK constructed above, C. glutamicum YDK0107 strain described in WO2016 / 171224 was transformed to obtain YDK0107 / pPK4_CspBss-QET-Z34CM-PA32-Fc3K strain, YDK0107 / pPK4_CspBss-QET-Z34CM-PA48-Fc3K strain, YDK0107 / pPK4_CspBss-QET-Fc3K-PA32-Z34CM strain, YDK0107 / pPK4_CspBss-QET-Fc3K-PA48-Z34CM strain, YDK0107 / pPK4_CspBss-QET-Fc3K-PA32-ProAR strain, YDK0107 / pPK4_CspBss-QET-Fc3K-PA48-ProAR strain, YDK0107 / pPK4_CspBss-QET-ProAR-PA32-Z34CK strain, and YDK0107 / pPK4_CspBss-QET-ProAR-PA48-Z34CK strain. Each of the obtained transformants was cultured in an MMTG liquid medium (glucose 120 g, magnesium sulfate heptahydrate 3 g, ammonium sulfate 30 g, potassium dihydrogen phosphate 1.5 g, iron sulfate heptahydrate 0.03 g, manganese sulfate pentahydrate 0.03 g, thiamine hydrochloride 0.45 mg, biotin 0.45 mg, DL-methionine 0.15 g, soybean hydrochloride hydrolyzate (total nitrogen content 0.2 g), calcium carbonate 50 g, adjusted to pH 7.0 with water to 1 L) containing 25 mg / L of kanamycin at 30°C for 72 hours. After completion of the culture, 6.5 μL of the culture supernatant obtained by centrifuging each culture solution was subjected to reducing SDS-PAGE using NuPAGE (registered trademark) 12% Bis-Tris Gel (Thermo Fisher Scientific), and then stained with Quick-CBB (Wako). As a result, a polypeptide band presumed to be QET-Z34CM-PA32-Fc3K was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Z34CM-PA32-Fc3K strain (Fig. 14, Lanes 2-5), a polypeptide band presumed to be QET-Z34CM-PA32-Fc3K was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Z34CM-PA32-Fc3K strain (Fig. 14, Lanes 6-9), a polypeptide band presumed to be QET-Fc3K-PA32-Z34CM was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Fc3K-PA32-Z34CM strain (Fig. 14, Lanes 10-13), a polypeptide band presumed to be QET-Fc3K-PA48-Z34CM was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Fc3K-PA48-Z34CM strain (Fig. 14, Lanes 14-17), a polypeptide band presumed to be QET-Fc3K-PA32-ProAR was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Fc3K-PA32-ProAR strain (Fig. 14, Lanes 18-21), a polypeptide band presumed to be QET-Fc3K-PA48-ProAR was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-Fc3K-PA48-ProAR strain (Fig. 14, Lanes 22-25), a polypeptide band presumed to be QET-ProAR-PA32-Z34CK was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-ProAR-PA32-Z34CK strain (Fig. 14, Lanes 26-29), and a polypeptide band presumed to be QET-ProAR-PA48-Z34CK was detected in the culture supernatant of the YDK0107 / pPK4_CspBss-QET-ProAR-PA48-Z34CK strain (Fig. 14, Lanes 30-33). (Reference Example 2) Preparation of a compound having an affinity substance, a cleavable moiety and a reactive group for an antibody A compound having a cleavable moiety and a reactive group was conjugated to the purified polypeptide. According to the previously reported (WO2019 / 0240287), an affinity reagent (1) was prepared by amidating the affinity substance QET-Z34CM-PA32-Fc3K prepared in Reference Examples 1-2. MS (ESI) m / z: z = 11 885.80 [M + 3H] ３＋ Similarly, an affinity reagent (2) was prepared from the affinity substance QET-Z34CM-PA48-Fc3K prepared in Reference Examples 1-2. MS (ESI) m / z: z = 13 849.35 [M + 3H] ３＋ Similarly, an affinity reagent (3) was prepared from the affinity substance QET-Fc3K-PA32-Z34CM prepared in Reference Examples 1-2. MS (ESI) m / z: z = 11 886.15 [M + 3H] ３＋ Similarly, an affinity reagent (4) was prepared from the affinity substance QET-Fc3K-PA48-Z34CM prepared in Reference Examples 1-2. MS (ESI) m / z: z = 13 849.20 [M + 3H] ３＋ Similarly, an affinity reagent (5) was prepared from the affinity substance QET-Fc3K-PA32-ProAR prepared in Reference Examples 1-2. MS (ESI) m / z: z = 12 885.1 [M + 3H] ３＋ Similarly, an affinity reagent (6) was prepared from the affinity substance QET-Fc3K-PA48-ProAR prepared in Reference Examples 1-2. MS (ESI) m / z: z = 11 1082.00 [M + 3H] ３＋ Similarly, an affinity reagent (7) was prepared from the affinity substance QET-ProAR-PA32-Z34CK prepared in Reference Examples 1-2. MS (ESI) m / z: z = 15 855.20 [M + 3H] ３＋ Similarly, an affinity reagent (8) was prepared from the affinity substance QET-ProAR-PA48-Z34CK prepared in Reference Example 1-2. MS (ESI) m / z: z = 17 830.75 [M + 3H] ３＋ (Reference Example 3) Specific modification of anti-HER2 IgG antibody trastuzumab and synthesis of ADC mimics (3-1) Specific modification of anti-HER2 antibody trastuzumab using affinity reagent (4) 500 μg of anti-HER2 IgG antibody trastuzumab (Chugai Pharmaceutical) was dissolved in 171 μL of 50 mM sodium acetate buffer (pH 5.5). An N,N'-dimethylformamide solution (10 equivalents) of the affinity reagent (4) synthesized in Reference Example 2 was added to the trastuzumab solution, and the mixture was stirred at room temperature for 1 hour. After removing the excess affinity reagent (4) by ultrafiltration, the mass was measured by ESI-TOFMS. As a result, a peak was observed at 148400 for the raw material trastuzumab, a peak was observed at 159300 for the product with one conjugated peptide introduced, and a peak was confirmed at 170390 for the product with two conjugated peptides introduced. (3-2) Synthesis of Trastuzumab (T-6) with one molecule of thiol group introduced The antibody obtained above was subjected to a thiol ester group cleavage reaction (treatment with hydroxylamine) according to a previously reported method (WO2019 / 240287) to obtain a thiol group-introduced antibody derivative (T-1-SH) having the following structural formula with one thiol group introduced. When the mass was measured by ESI-TOFMS, a peak was confirmed at 148489 where the cleavage reaction proceeded. (3-3) Specific modification of anti-HER2 antibody trastuzumab using affinity reagent (6) and synthesis of thiol group-introduced antibody derivative by cleavage of thiol ester group Similarly, using the affinity reagent (6) synthesized in Reference Example 2, the modification reaction of trastuzumab was carried out. After removing the excess affinity reagent (6), when the mass was measured by ESI-TOFMS, the peak of the raw material trastuzumab was observed at 148227, the peak of the product with one binding peptide introduced was observed at 160165, and the peak of the product with two binding peptides introduced was confirmed at 171953. In addition, Table 1 shows the results of confirming the peptide / antibody binding ratio using a DAR calculator (software of Agilent). The antibody obtained above was subjected to a cleavage reaction of the thioester group according to a previously reported method (WO2019 / 0240287) to obtain a thiol group-introduced antibody derivative (T-1-SH) with one thiol group introduced. When the mass was measured by ESI-TOFMS, a peak was confirmed at 148489 where the cleavage reaction proceeded. (3-4) Peptide mapping by trypsin treatment Peptide mapping was performed on the trastuzumab thiol-introduced product (T-1-SH) obtained in (3-2) in the following steps. (3-4-1) Trypsin treatment of trastuzumab thiol-introduced product 10 μL of the sample solution, 10 μL of a 20 mM aqueous solution of dithiothreitol dissolved in 150 mM Tris-HCl buffer (pH 8.0) and 40% trifluoroethanol were added to a 1.5 mL low adsorption microtest tube, and the mixture was heated at 65 °C for 1 hour. Then, 10 μL of a 50 mM aqueous solution of iodoacetamide was added, and the reaction was carried out at room temperature for 30 minutes under light shielding. After the reaction, 40 μL of 150 mM Tris-HCl buffer (pH 8.0) was added and stirred, 10 μL of a 20 ng / μL aqueous solution of trypsin was added, and enzymatic digestion was carried out at 37 °C for 16 hours. After digestion, 2 μL of a 20% aqueous solution of trifluoroacetic acid was added to stop the reaction, and the sample solution was diluted 10-fold with a 0.1% formic acid, 2% acetonitrile aqueous solution and subjected to LC-MS / MS measurement. (3-4-2) LC-MS / MS measurement of trastuzumab (Analytical instrument) Nano HPLC: EASY-nLC 1000 (Thermo Fisher Scientific) Mass spectrometer: Triple quadrupole mass spectrometer Orbitrap Fusion (Thermo Fisher Scientific) (HPLC analysis conditions) Trap column: Acclaim PepMap (registered trademark) 100, 75μm x 2cm (Thermo Fisher Scientific) Analytical column: ESI-column (NTCC-360 / 75-3-125, 75μm × 12.5cm, 3μm (Nikkatsu Technos Co., Ltd.)) Mobile phase A: 0.1% aqueous formic acid solution Mobile phase B: 0.1% formic acid, acetonitrile solution Loading solution: 0.1% aqueous trifluoroacetic acid solution Flow rate: 300 nL / min Sample injection volume: 0.6 μL Gradient conditions (B%): 2% (0.0 - 0.5 min), 2% → 50% (0.5 - 50 min), 50% (50 - 55.5 min), 50% → 95% (55.5 - 56.5 min), 95% (56.5 - 60 min) (Mass spectrometer analysis conditions) Ionization method: ESI, Positive mode Scan type: Data Dependent Acquisition Activation Type: Collision Induced Dissociation (CID) Data acquisition was performed using the attached software Xcalibur 4.3 (Thermo Fisher Scientific) and Thermo Orbitrap Fusion Tune Application 3.3 (Thermo Fisher Scientific). Example 7 Preparation of natural killer cell (hereinafter referred to as NK cell)-antibody complex Example 7-1 Cultivation of NK cells CellXVivo ＴＭAn NK cell medium and an NK cell culture plate were prepared using a Human NK Cell Expansion Kit (R&D Systems, Inc.). NK cells (Lonza Co., Ltd.) were cultured on an NK cell culture plate using an NK cell medium (hereinafter referred to as NK activation medium) supplemented with IL-2, Human, Recombinant (PeproTech, Inc.) at a final concentration of 10002 U / mL and recombinant human IL-15 (PeproTech, Inc.) at a final concentration of 2.50 ng / mL. Example 7-2 Preparation of Linker-Modified Antibody Example 7-2-1 Synthesis of Trastuzumab (T-6) with One Molecule of Thiol Group Introduced According to Reference Example (3-1) and Reference Example (3-2), Trastuzumab (T-6) with one molecule of thiol group introduced was synthesized. Example 7-2-2 Synthesis of Trastuzumab (T-7) with One Molecule of Cy5 Introduced To a 3 mg / mL PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) solution of Trastuzumab (T-6) with one molecule of thiol group introduced obtained in Example 7-2-1, a dimethylformamide solution of N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 (BroadPharm) (2.5 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain an antibody (T-5) with one molecule of Cy5 introduced. HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of Cy5. Example 7-2-3 Synthesis of Trastuzumab (T-8) with One Molecule of Cy5 and One Molecule of Peptide Reagent Introduced Using Trastuzumab (T-7) with one molecule of Cy5 introduced as obtained in Example 7-2-2 and reagent P1 described in the prior report (WO2019 / 240287A1), by following the method of WO2019 / 240287A1, Trastuzumab with one thiol group introduced (T-8) was obtained for T-7. Example 7-2-4 Synthesis of Trastuzumab (T-9) with one molecule of Cy5 and one molecule of PEG4-benzocyclooctyne (DBCO) introduced To a 3 mg / mL PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) solution of Trastuzumab (T-8) with one molecule of Cy5 and one molecule of thiol introduced as obtained in Example 7-2-3, a dimethylformamide solution of DBCO-PEG4-Maleimide (BroadPharm) (2.5 equivalents to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain Trastuzumab (T-9) with one molecule of Cy5 and one molecule of PEG4-DBCO introduced. HIC-HPLC analysis was performed according to the prior report (Anal. Chem., 2019, 91, 20, 12724-12732), and it was confirmed that PEG4-DBCO was introduced. Example 7-2-5 Synthesis of Trastuzumab (T-10) with one molecule of Cy5 and one molecule of PEG12-benzocyclooctyne (DBCO) introduced To a 3 mg / mL solution of Trastuzumab (T-8) in PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) with one molecule of Cy5 and one molecule of thiol introduced as obtained in Example 7-2-3, a dimethylformamide solution of DBCO-PEG12-Maleimide (BroadPharm) (2.5 equivalents relative to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain Trastuzumab (T-10) with one molecule of Cy5 and one molecule of PEG12-DBCO introduced. HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of PEG12-DBCO. Example 7-2-6 Synthesis of Trastuzumab (T-11) with One Molecule of Cy5 and One Molecule of PEG24-Benzocyclooctyne (DBCO) Introduced To a 3 mg / mL solution of Trastuzumab (T-8) in PBSE buffer (10 mM Phosphate Buffered Saline (PBS), 10 mM EDTA, pH 7.4) with one molecule of Cy5 and one molecule of thiol introduced as obtained in Example 7-2-3, a dimethylformamide solution of DBCO-PEG24-Maleimide (BroadPharm) (2.5 equivalents relative to the antibody, dimethylformamide (DMF) (8% v / v) solution) was added, and the mixture was shaken at room temperature for 1 hour. The reaction solution was purified using a NAP-25 desalting column (manufactured by Cytiva) to obtain Trastuzumab (T-11) with one molecule of Cy5 and one molecule of PEG24-DBCO introduced. HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of PEG24-DBCO. Example 7-3 Preparation of Antibody-NK Cell Conjugates Using Amine-Reactive Reagents 7-3-1 Peptide Synthesis The peptides consisting of the amino acid sequences of SEQ ID NOs: 41 and 42 were synthesized by solid-phase synthesis according to the method described in International Publication No. 2018 / 199337 (the same applies to the peptide synthesis hereinafter). The N-terminus was modified with 4-Azidobenzoic Acid (Az, Tokyo Chemical Industry Co., Ltd.) to introduce an azide group. SEQ ID NO: 41: Az-EEEE-C-NH ２ SEQ ID NO: 42: Az-EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEC-NH ２ 7-3-2 Preparation of amine-reactive reagents As amine-reactive reagents having a bioorthogonal reactive group, Azido-PEG4-NHS ester (BroadPharm), Azido-PEG12-NHS ester (BroadPharm), Azido-PEG24-NHS ester (BroadPharm), DBCO-PEG12-NHS ester (BroadPharm), DBCO-Sulfo-NHS ester (Click Chemistry Tools), and Sulfo DBCO-PEG4-TFP ester (BroadPharm) were used. Also, Az-EEEE-C-NH ２ (SEQ ID 41), Az-EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEC-NH ２ (SEQ ID NO: 42) were dissolved in DMSO. To this, NHS-PEG6-Maleimide (Funakoshi Co., Ltd.) was added at a molar equivalent of 0.77 and reacted at 37 °C for 8 hours to synthesize a peptide reagent having an amine-reactive group and a bioorthogonal reactive group at the end. 7-3-3 Preparation of NK cells having an azide group on the cell surface The number of NK cells cultured according to Example 7-1 was quantified using NucleoCounter (registered trademark) NC-200 (trademark) (ChemoMetec). 1.0×10 ６NK cells were sorted from the cells and centrifuged (at 4000 rpm for 5 minutes), and then the supernatant was removed. After adding 1 mL or more of PBS, centrifugation (at 4000 rpm for 5 minutes) and removal of the supernatant (hereinafter referred to as the washing step) were repeated twice, and then 1 mL of 250 μM (PBS solution) of Azido-PEG24-NHS ester (BroadPharm) was added. After repeating inversion mixing using a rotary mixer for 30 minutes, centrifugation (at 4000 rpm for 5 minutes) was performed, and then the supernatant was removed. Subsequently, the above washing step was repeated twice again, and by adding 200 μL of NK activation medium, NK cells having an azide group on the cell surface were prepared. 7-3-4 Preparation of NK cells having a bioorthogonal reaction group on various cell surfaces Similar to Example 7-3-3, NK cells having a bioorthogonal reaction group on the cell surface were prepared using the amine-reactive reagent prepared in Example 7-3-2. 7-3-5 Preparation of antibody-NK cell conjugates 7-3-5-1 Preparation of antibody-NK cell conjugate (ACC-1) with a PEG28 linker To the NK cells having azide on the cell surface obtained in Example 7-3-3, Trastuzumab in which one molecule each of Cy5 and PEG4-DBCO synthesized in Example (7-2-4) was introduced so as to have a final concentration of 2 μL was added, and the mixture was allowed to stand in a 37 °C incubator for 1 hour. After centrifugation (at 4000 rpm for 5 minutes) and removal of the supernatant, the washing step was repeated twice, and finally, by adding NK activation medium, an antibody-NK cell conjugate (ACC-1) with a PEG28 linker was synthesized. 7-3-5-2 Preparation of antibody-NK cell conjugate (ACC-2) with a PEG48 linker To the NK cells having azide on the cell surface obtained in Example 7-3-3, Trastuzumab in which one molecule each of Cy5 and PEG24-DBCO synthesized in Example (7-2-6) was introduced was added to a final concentration of 2 μL, and the mixture was allowed to stand in a 37°C incubator for 1 hour. After centrifugation (5 minutes at 4000 rpm) and removal of the supernatant, the washing step was repeated twice, and finally an NK activation medium was added to synthesize an antibody-NK cell conjugate (ACC-2) having a PEG48 linker. 7-3-6 Evaluation of Antibody-NK Cell Conjugates Flow cytometry analysis using an Attune NxT Flow Cytometer (Thermo Fisher Scientific) was performed on ACC-1, and it was observed that the antibody was bound to the cells. By using the maximum autofluorescence value of NK cells without surface modification as a threshold, as shown in Figure 15, strong fluorescence derived from Cy5 was observed in the antibody-NK cell conjugate. From this, it was confirmed that the antibody was bound to NK cells with high efficiency. Example 7-4 Preparation of Antibody-NK Cell Conjugates Using the Metabolic Labeling Method 7-4-1 Preparation of NK Cells Having Azide Groups on the Cell Surface To the NK cells cultured according to Example 7-1, N-azidoacetylmannosamine tetraacylated (Tokyo Chemical Industry Co., Ltd.) was added to final concentrations of 25 μM, 50 μM, and 100 μM. After incubation overnight at 37°C, the cells were centrifuged (5 minutes at 4000 rpm) and the supernatant was removed. After washing twice with PBS (after adding 1 mL or more of PBS and removing the supernatant by centrifugation), an NK activation medium was added to prepare NK cells having azide groups on the cell surface. 7-4-2 Preparation of Antibody-NK Cell Conjugates 7-4-2-1 Preparation of Antibody-NK Cell Conjugate (ACC-3) Having a PEG4 Linker To the NK cells having azide on the cell surface obtained in Example 7-4-1, Trastuzumab in which one molecule each of Cy5 and PEG4-DBCO synthesized in Example (7-2-4) was introduced so as to have a final concentration of 2 μL was added, and the mixture was allowed to stand in a 37°C incubator for 1 hour. After centrifugation (4000 rpm for 5 minutes) and removal of the supernatant, the washing step was repeated twice, and finally, an NK activation medium was added to synthesize an antibody-NK cell conjugate (ACC-3) having a PEG4 linker. 7-4-2-2 Preparation of Antibody-NK Cell Conjugate (ACC-4) with PEG12 Linker To the NK cells having azide on the cell surface obtained in Example 7-4-1, Trastuzumab in which one molecule each of Cy5 and PEG12-DBCO synthesized in Example 7-2-5 was introduced so as to have a final concentration of 2 μL was added, and the mixture was allowed to stand in a 37°C incubator for 1 hour. After centrifugation (4000 rpm for 5 minutes) and removal of the supernatant, the washing step was repeated twice, and finally, an NK activation medium was added to synthesize an antibody-NK cell conjugate (ACC-4) having a PEG12 linker. 7-4-2-3 Preparation of Antibody-NK Cell Conjugate (ACC-5) with PEG24 Linker To the NK cells having azide on the cell surface obtained in Example 7-4-1, Trastuzumab in which one molecule each of Cy5 and PEG24-DBCO synthesized in Example 7-2-6 was introduced so as to have a final concentration of 2 μL was added, and the mixture was allowed to stand in a 37°C incubator for 1 hour. After centrifugation (4000 rpm for 5 minutes) and removal of the supernatant, the washing step was repeated twice, and finally, an NK activation medium was added to synthesize an antibody-NK cell conjugate (ACC-5) having a PEG24 linker. 7-4-3 Evaluation of Antibody-NK Cell Conjugate The antibody-NK cell conjugate obtained in Example 7-4-2 was subjected to the same operation as in Example 7-3-6, and it was confirmed that the antibody was bound to the cell surface with higher efficiency (Figure 16). Example 8 Cytotoxicity Evaluation of Antibody-NK Cell Conjugate 8-1 Culture of SK-BR-3 Cells SK-BR-3 (ATCC) was selected as the HER2-positive target cell. SK-BR-3 was cultured in RPMI 1640 Medium, GlutaMAX (trademark) Supplement medium (Thermo Fisher Scientific) supplemented with 10% FBS (Thermo Fisher Scientific). The above SK-BR-3 culture medium is hereinafter referred to as RPMI medium. 8-2 Cytotoxicity Evaluation Assay As a cytotoxicity evaluation system, an assay system using the DELFIA EuTDA Cytotoxicity Detection kit (Revvity) (hereinafter referred to as the DELFIA assay) was used. The SK-BR-3 cells cultured according to Example 8-1 were washed twice with PBS, and then TrypLE (trademark) Select Enzyme (1X), no phenol red (Thermo Fisher Scientific) was added. After incubating at 37°C for 3 minutes to suspend the cells, centrifugation (120 g for 5 minutes) was performed, and after removing the supernatant, 1 mL of RPMI medium (see Example 8-1) was added. After measuring the number of cells and viability in the obtained cell suspension with a Countess Automated Cell Counter (Thermo Fisher Scientific), 2.5×10 ６RPMI medium was added until the concentration reached cells / mL. 1 mL of the obtained cell suspension was aliquoted, and 5 μL of DELFIA BATDA labeling reagent (attached to the DELFIA EuTDA Cytotoxicity Detection kit) was added thereto, followed by incubation at 37 °C for 1 hour. After centrifugation to remove the supernatant, 1 mL of PBS was added for washing, and the steps of centrifuging to remove the supernatant were repeated twice, and then 500 μL of NK activation medium was added. The number of cells and the viability in the obtained cell suspension were measured with a Countess Automated Cell Counter (Thermo Fisher Scientific), and NK activation medium was added until the concentration reached 50000 cells / mL. The obtained cell suspension was dispensed into a 96-well plate at 100 μL per well to prepare target cells for the assay. Thereto, NK cells prepared according to Example 7-1 and antibody-NK cell conjugates prepared according to Examples 7-3-5 and 7-4-2 were added such that the ratio of NK cells or antibody-NK cell conjugates to SK-BR-3 cells was 6:1, 3:1, 1:1, 0:1, and adjusted to a final volume of 200 μL / well. At this time, the number of cells of NK cells and antibody NK conjugates was measured using a NucleoCounter (registered trademark) NC-200 (trademark) (Chemometec). Also, instead of effector cells, wells to which 90 μL of NK activation medium and 10 μL of Lysis buffer (attached to the DELFIA EuTDA Cytotoxicity Detection kit) were added (hereinafter referred to as 100% kill wells) and wells to which 100 μL of NK activation medium was added (hereinafter referred to as control wells) were also prepared. After incubating the above 96-well plate at 37 °C for 4 hours, it was centrifuged (500 g, 5 minutes), and 20 μL of the supernatant was added to a 96-well plate for DELFIA assay (attached to the DELFIA EuTDA Cytotoxicity Detection kit) prepared separately. 200 μL of DELFIA Eu-Solution was added thereto, and after shaking at room temperature for 15 minutes, time-resolved fluorescence measurement of each well was performed using a Revvity Nivo multimode plate reader (Revvity). Based on the obtained intensity, cytotoxicity was calculated using the following formula. As a result, as shown in Fig. 17, the antibody-NK cell conjugates synthesized by the modification method using the NHS reagent and the metabolic labeling method showed higher cytotoxicity than NK cells. Comparative Example 1 Preparation of antibody-cell conjugate prepared based on prior literature 1-1 Synthesis of Trastuzumab (T-13) into which single-stranded DNA was introduced Using Trastuzumab (Chugai Pharmaceutical) and single-stranded DNA (hereinafter referred to as DNA1, SEQ ID NO: 43), Trastuzumab (T-13) into which single-stranded DNA was introduced was synthesized according to prior literature (WO2023 / 114719Al, Cytotherapy 22 (2020) 135-143). HIC-HPLC analysis was performed according to a previously reported method (Anal. Chem., 2019, 91, 20, 12724-12732) to confirm the introduction of DNA. SEQ ID NO: 43: s_ccctagagtgagtcgtatga (s=Thiol C6) 1-2 Synthesis of NK cells (C-1) into which single-stranded DNA was introduced Using NK cells and single-stranded DNA (hereinafter referred to as DNA2, SEQ ID NO: 44), NK cells (C-1) modified with single-stranded DNA2 on the surface were prepared according to prior literature (WO2023 / 114719Al, Langmuir. 2009 June 16; 25(12):6985-6991). Array number 44: s_tcatacgactcactctaggg (s = Thiol C6) 1-3 Preparation of antibody-NK cell conjugate (ACC-6) with DNA linker Using Comparative Examples (1-1) and (1-2), an antibody-NK cell conjugate (ACC-6) was synthesized according to prior literature (WO2023 / 114719Al, Cytotherapy 22 (2020) 135-143, Langmuir. 2009 June 16; 25(12): 6985-6991). Comparative Example 2 Cytotoxicity comparison with antibody-NK cell conjugate prepared based on prior literature The cytotoxicities of the antibody-NK cell conjugate (ACC-6) synthesized based on Comparative Example 1-3 and the antibody-NK cell conjugates (ACC-3, 4, 5) synthesized in Example 7-4-2 were confirmed according to the method of Example 8-2. As a result, as shown in Fig. 18, ACC-3 and 4, 5 showed higher activities than ACC-6. From this, it was shown that the antibody-NK cell conjugates (ACC-3, 4, 5) synthesized in Example 7-4-2 exhibited higher cytotoxicity than the antibody-NK cell conjugate (ACC-6) synthesized in Comparative Example 1-3. Comparative Example 3 Antigen binding ability comparison with antibody-NK cell conjugate prepared based on prior literature After preparing the antibody-NK cell conjugate (ACC-6) synthesized based on Comparative Example 1-3 and the NK cell conjugate (ACC-5) synthesized based on Example 7-4-2, they were cultured for one day and the HER2 binding ability was evaluated based on Example 5-2. As a result, as shown in Fig. 19, ACC-5 showed higher antigen binding ability than ACC-6.

Claims

1. An Fc-cell complex comprising a cell and an antibody Fc region bound to the surface of the cell, wherein the antibody Fc region is formed by disulfide bonding of two Fc constituent polypeptides, and the antibody Fc region is chemically bound to the cell surface via a linker introduced to a functional group in the side chain of a specific amino acid residue present at one or more positions in one of the two antibody Fc constituent polypeptides.

2. The Fc-cell complex according to claim 1, wherein the specific amino acid residue is any one or more of 14 types of amino acid residues consisting of asparagine, glutamine, methionine, proline, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, arginine, histidine, and lysine.

3. The Fc-cell complex of claim 1, wherein the specific amino acid residue is a lysine residue.

4. The Fc-cell complex of claim 3, wherein the lysine residue is any one or more of the lysine residues at positions 246, 248, 274, 288, 290, 317, 320, 322, 360, 414, and 439.

5. The Fc-cell complex according to claim 1, wherein the antibody Fc region has a functional substance introduced therein via a linker introduced into a functional group in the side chain of a specific amino acid residue present at one or more positions in the other of the two Fc constituent polypeptides.

6. The Fc-cell complex according to claim 5, wherein the functional substance is a drug, a labeling substance, an affinity substance, a transport substance, or a stabilizer.

7. The Fc-cell complex of claim 1, wherein the antibody Fc region comprises an antibody variable region.

8. The Fc-cell complex of claim 1, wherein the antibody Fc region comprises a fusion protein of an antibody Fc constituent polypeptide and a functional polypeptide.

9. The Fc-cell complex according to claim 1, wherein the antibody Fc region is introduced onto the cell surface by reaction between a bioorthogonal functional group introduced via a linker into a functional group in the side chain of a specific amino acid residue present at one or more positions of one of the two Fc constituent polypeptides and a group present or introduced onto the cell surface that reacts with the bioorthogonal functional group.

10. A method for producing a cell-Fc region complex, comprising: (I) preparing an antibody Fc region in which two antibody Fc constituent polypeptides are disulfide-bonded; and (II) reacting the antibody Fc region with a compound represented by the following formula (Ia) or formula (Ib) to form an Fc-compound (Ia) complex or an Fc-compound (Ib) complex. [wherein R represents a group reactive to the Fc region, and L １ represents the first linker, L ２ represents a second linker, CLE(B) represents a cleavable moiety that can generate a bioorthogonal functional group on the reactive group side upon cleavage, and A represents an affinity substance containing an affinity peptide. [In the formula, R represents the reactive group, and L ５ represents the fifth linker, L ６ represents a sixth linker, B represents a group containing a bioorthogonal functional group, CLE represents a cleavable moiety, and A represents the affinity substance.] (III) a step of cleaving an Fc-compound (Ia) complex or an Fc-compound (Ib) complex with the cleavable moiety to form an Fc region that does not contain the affinity substance and has a bioorthogonal functional group introduced therein, (IV) a step of preparing a cell having a functional group on its surface that reacts with the bioorthogonal functional group, and (V) a step of reacting the Fc region having the bioorthogonal functional group introduced therein with the cell, with the bioorthogonal functional group of the Fc region and the functional group of the cell that reacts with the bioorthogonal functional group, thereby introducing the Fc region onto the cell surface.

11. A is AP1-L Ａ -AP2 (wherein AP1 represents a first affinity peptide having affinity for the constant region of the heavy chain of an antibody, AP2 represents a second affinity peptide having affinity for the constant region of the heavy chain of an antibody, and L Ａ The method according to claim 10 , wherein:

12. Compound (Ia) is represented by the following formula (Ia-1): [wherein X represents a leaving group, W １ , W ２ and W. ３ each independently represents an oxygen atom or a sulfur atom; L ３ represents a third linker, L ４ represents a fourth linker, S represents a sulfur atom, and A represents the affinity substance.

13. Compound (Ib) is represented by the following formula (Ib-1): [wherein X represents a leaving group, W １ , W ２ and W. ３ each independently represents an oxygen atom or a sulfur atom; L ７ represents the seventh linker, L ８ represents an eighth linker, B represents a group containing a bioorthogonal functional group, V represents an oxygen atom or a sulfur atom, and A represents the affinity substance.

14. The method for producing a cell-Fc region complex described in claim 10, wherein the bioorthogonal functional group is an azide group, an alkyne residue, a tetrazine residue, an alkene residue, a thiol group, a maleimide residue, a furan residue, or a halocarbonyl residue.

15. A method for producing a cell-Fc region complex according to claim 10, wherein the cell-Fc region complex is an Fc-cell complex according to any one of claims 1 to 9.

16. A method for producing a cell-Fc region complex according to claim 10, wherein the cell-Fc region complex is the Fc-cell complex according to claim 5, and the method comprises the step of introducing a functional substance into a functional group in the side chain of a specific amino acid residue present at one or more positions in the other of the two Fc constituent polypeptides in the antibody Fc region.

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