The invention provides an anti-CD3
monoclonal antibody, a
bispecific antibody and application of the anti-CD3
monoclonal antibody and the
bispecific antibody, and particularly provides an
antibody or an
antigen binding fragment which comprises at least one of the following CDRs: a
heavy chain variable region CDR in SEQ ID NO: 1-3 or a conservatively modified form thereof; sEQ ID NO: 4-6 or a light chain variable region CDR in a conservative modification form thereof. The antibody or the
antigen binding fragment has different affinity with CD3
protein at different pH values, has
weak binding capacity in animal tissues or
peripheral blood with normal pH values, has low
peripheral drug concentration, reduces off-target
toxicity risk, has strong affinity with CD3 at tumor tissues or around the tumor tissues, is beneficial to distribution to local tumor, increases local
drug concentration, and reduces the risk of off-target
toxicity of the antibody or the
antigen binding fragment in the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues or around the tumor tissues. The double antibodies prepared from the polypeptide can promote the combination of T cells and
tumor cells, are high in safety and specificity, and can effectively treat tumors, autoimmune diseases, inflammatory diseases and / or
transplant rejection.