title: Distinct roles for L3T4 in T cell activation.
abstract: The mutually exclusive expression of L3T4 and Lyt-2 on murine T cells and the correlation of their expression to the major histocompatibility complex (MHC) restriction of the T cell antigen receptor (Ti) have led to the hypothesis that these surface molecules are related to recognition of class II and class I MHC antigens, respectively. It has been suggested that these T cell surface molecules interact with nonpolymorphic determinants on MHC antigens. We have studied the role of L3T4 in activation of an H-2Dd-specific T cell hybridoma. This novel hybridoma allowed the separate evaluation of the specificities of Ti and L3T4 and the examination of their roles in T cell activation. Antibody-blocking experiments have demonstrated that L3T4 was involved in triggering this T cell hybridoma only if the antigen-bearing cell expressed Ia. The apparent requirement for an L3T4-Ia interaction reflected the amount of available H-2Dd antigen. It appears that the L3T4-Ia interaction influences T cell activation during suboptimal antigenic stimulation. We have begun to examine the role of L3T4 in lectin and anti-Ti monoclonal antibody stimulation of the same T cell hybridoma. These experiments have suggested a distinct role for L3T4 in the absence of Ia, as a mediator of a negative signal for activation.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D006183:H-2 Antigens / Q000276:immunology; D064532:Histocompatibility Antigen H-2D; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D051379:Mice; D011971:Receptors, Immunologic / Q000276:immunology; D013601:T-Lymphocytes / Q000145:classification* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; D011971:Receptors, Immunologic