title: Possible involvement of the T4 molecule in T cell recognition of class II HLA antigens: evidence from studies of proliferative responses to SB antigens.
abstract: The T4 molecule has been identified as a marker of human T cell differentiation, but the function of this molecule remains to be defined. We have investigated its possible functional involvement in T cell proliferative responses to class II HLA antigens encoded by the recently described SB locus. The responses of SB-primed cells (specific for each of four different SB antigens) were studied with the use of two proliferation-inducing stimuli, SB antigen or TCGF. The proliferative responses to both stimuli were found to be mediated by T4+, T8- cells. Monoclonal antibodies against some epitopes on the T4 molecule (OKT4A and OKT4B) substantially blocked antigen-stimulated proliferative responses; antibodies against other epitopes of the T4 molecule (OKT4, T4C, T4D) blocked less well. Inhibition of SB-specific proliferation by antibodies to the T4 molecule was maximal only when the antibodies were incubated with the responder cells before the addition of stimulator cells. Proliferative responses of SB-primed cells stimulated with TCGF alone were not inhibited by any of the OKT4-related antibodies, but were completely inhibited by the anti-Tac monoclonal antibody, which reacts with the TCGF receptor. These results lend further support for the hypothesis that the T4 molecule is involved in T cell recognition of and/or activation by class II HLA antigens. We suggest that 1) the T4 molecule binds a nonpolymorphic epitope on class II HLA molecules, and 2) this interaction may facilitate, but not be an obligate requirement for, T cell activation by class II antigens.
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology; D001667:Binding, Competitive; D000939:Epitopes; D006682:HLA-DP Antigens; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology; D007700:Kinetics; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D006682:HLA-DP Antigens; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2