Antibodies against monomorphic determinants of the α chain of class I human leukocyte antigens inhibit the reaction of human lymphocytes to mitogen and tetanus toxoid

Monoclonal antibodies directed against the α chain of Class I Major Histocompatibility Complex (MHC) antigens inhibtt the reactivity of human T lymphocytes to mitogen or antigen. In contrast, monoclonal antibodies to β₂ microglobulin do not suppress human T cell proliferation to these same stimuli. As antigen presentation by accessory cells involves Class II and not Class I MHC antigens, the inhibition of human T cell proliferation in response to mitogen or antigen may occur at the level of the responder cell. The differential effect seen between monoclonal antibodies directed against the α chain of Class I MHC framework determinants and antibodies reactive with the polymorphic determinants suggests functionally separate components of the Class I MHC molecules.