title: Does OKT3 monoclonal antibody react with an antigen-recognition structure on human T cells?
abstract: OKT3 monoclonal antibody to human T cells inhibits the target cell lysis mediated by allogeneic cytotoxic T cells and the generation of these effector cells in mixed lymphocyte culture. This marked inhibition of cell-mediated lysis is not found with other monoclonal antibodies also reactive with cell surface antigens of human T cells (OKT1, OKT4, OKT5, OKT6, OKT8, and OKT11). OKT3 antibody is mitogenic and this effect appears to require receptor activation in that it occurs at low concentrations (10(-12) M range) of OKT3 antibody, requires intact OKT3 IgG, and is inhibited by a factor(s) in human plasma. By contrast, the inhibition of allogeneic cell-mediated lysis by OKT3 antibody appears to be due to steric hindrance in that it requires higher concentrations of OKT3 antibody (10(-8) M range), Fab fragments retain approximately 10% activity, and inhibition is demonstrable in the presence of human plasma. These findings are consistent with the suggestion that OKT3 antibody reacts with the human T-cell antigen-recognition structure.
mesh_terms: D000328:Adult; D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000936:Antigen-Antibody Complex; D000954:Antigens, Surface / Q000276:immunology*; D000939:Epitopes; D006801:Humans; D006822:Hybrid Cells / Q000276:immunology; D007118:Immunoassay; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex; D000954:Antigens, Surface; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G