Involvement of T11 molecules in antigen receptormediated T lymphocyte functions: effect of anti-T11 monoclonal antibody on functional capabilities of alloreactive T cell clones

Abstract

As shown by previous studies, the sheep erythrocyte‐binding T11 molecule is involved in T cell activation, as well as in mechanisms of specific allogeneic target cell lysis. In this study, we utilized two anti‐T11 monoclonal antibodies (mAb) that inhibited the specific cytolytic activity of mixed lymphocyte culture (MLC)‐activated T cells to analyze, at the clonal level, the involvement of T11 molecules in (a) antigen‐specific vs. nonspecific mechanisms of target cell lysis, and (b) antigen‐driven T cell proliferation and interleukin 2 (IL2) production vs. IL2‐induced cell proliferation. In contrast to anti‐T3 or anti‐T8 mAb, antibodies to T11 molecules inhibited the cytolytic activity of MLC‐derived allospecific clones in a uniform manner. In addition, anti‐T11 antibodies inhibited the specific activity of cytotoxic T lymphocyte clones resistant to anti‐T3 antibodies, even after antibody‐induced modulation of T3 molecules (while anti‐T3 mAb had no effect). Similarly, anti‐T11 antibodies inhibited the alloantigen‐induced proliferation and IL2 release of alloreactive clones independent of their T4⁺ or T8⁺ phenotype. The inhibitory activity of anti‐T11 antibodies appears to be confined to antigen‐specific T cell functions since neither natural killer‐like activity of cytotoxic T lymphocyte clones nor the IL 2‐induced clonal proliferation was affected. Thus, our results indicate that T11 molecules are functionally involved in antigen recognition by T cell regardless of their function and T4/T8 phenotype. The possible mechanisms of anti‐T11 antibody‐mediated inhibition are discussed.