title: Modulation of Tac antigen on activated human T cells by anti-Tac monoclonal antibody.
abstract: A monoclonal antibody termed anti-Tac antibody is reactive with activated and functionally mature human T cells, but not reactive with resting T cells or B cells. We found that the expression of Tac antigen on activated T cells was inhibited by the addition of anti-Tac antibody in the culture of T cells activated with Con A or alloantigen. In the mixed lymphocyte culture, the expression of Ia-like antigen on allo-activated T cells was also inhibited by anti-Tac antibody, although the antibody does not recognize Ia-like antigen. However, anti-Ia monoclonal antibody did not suppress the expression of either Tac or Ia-like antigen. In addition, Tac antigen expressed on activated T cells was modulated by anti-Tac antibody cultured with activated T cells at 37 degrees C for 48 hr. Antigenic modulation, which means a specific loss of Tac antigen from the cell surface of T cells, was detected by the indirect immunofluorescence method. Tac antigen was reexpressed on T cells after restimulation when the anti-Tac antibody was removed, whereas Ia-like antigen already expressed on allo-activated T cells was not modulated by anti-Tac antibody. These results suggest that Tac and Ia-like antigens are carried on different molecules, both of which are closely linked in expression on activated T cells. The expression of Tac antigen may be essential for the following expression of Ia-like antigen.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D003208:Concanavalin A / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D003208:Concanavalin A