Does OKT3 monoclonal antibody react with an antigen-recognition structure on human T cells?

Abstract

OKT3 [mouse] 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; 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. 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. OKT3 antibody probably reacts with the human T cell antigen-recognition structure.