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

Monoclonal antibodies directed against the alpha chain of Class I Major Histocompatibility Complex (MHC) antigens inhibit the reactivity of human T lymphocytes to mitogen or antigen. In contrast, monoclonal antibodies to beta 2 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 alpha chain of Class I MHC framework determinants and antibodies reactive with the polymorphic determinants suggests functionally separate components of the Class I MHC molecules.