Effects of cytotoxic monoclonal antibody specific for T200 glycoprotein on functional lymphoid cell populations

Abstract

A monoclonal antibody against T200 glycoprotein is selectively cytotoxic for thymocytes and mature thymus-dependent (T) lymphocytes. All T-cell functions assayed, cell-mediated cytotoxicity, helper cell activity, and proliferation in response to T-cell mitogens or allogeneic cells were abolished by prior treatment of spleen cells with anti-T200 antibodies and complement. In contrast, thymus-independent (B) cell responses to lipopolysaccharide (LPS) and other B-cell mitogens were unaffected. Although treatment of spleen cells with anti-T200 antibodies and complement markedly reduced their capacity to mount an in vitro antibody response to sheep red blood cells (SRBC), responsiveness could be restored by the addition of SRBC-primed T-helper cells. Treatment of bone marrow cells with anti-T200 antibodies and complement did not eliminate either in vivo colony-forming units-spleen (CFU-S) or prothymocytes. It is concluded that T lymphocytes become sensitive to complement-mediated lysis by anti-T200 antibodies as a consequence of cell-surface modifications occurring shortly before or just after their entry into the thymus. In contrast to Thy-1 antigen, the selective killing by antibody against T200 glycoprotein cannot be readily accounted for by quantitative differences in the expression of T200 glycoprotein on the cell surface. Fluorescence-activated cell analysis showed that T200 glycoprotein was expressed in similar amount on the majority of all thymocytes, spleen, and bone marrow cells.