Antibody directed at a surface structure inhibits cytolytic but not suppressor function of human T lymphocytes

Abstract

Experiments using conventional antisera^1,2 and monoclonal antibodies^3–5 have shown that there are two functionally distinct human T-cell subsets which express unique cell-surface glycoproteins^6–9. The inducer population expresses a 62,000-molecular weight (M_r) antigen termed T4 (ref. 6) whereas the cytotoxic/suppressor population lacks T4 but expresses T5 antigen. This antigen is a 76,000-M_r molecule in nonreducing conditions and a 33,000-M_r glycoprotein occasionally appearing as a doublet in reducing conditions. As the functions of subset-specific T-cell surface glycoproteins have not been elucidated, we have now examined the effect on T-cell function of three monoclonal antibodies reactive with the cytotoxic/suppressor subset; anti-T8_A antibody markedly inhibited cell-mediated lympholysis (CML) and anti-T8 partially affected CML, whereas anti-T5 had no effect. In contrast, there was no effect on suppressor cell function. Immunoprecipitation studies and competitive binding experiments indicated that anti-T8 and anti-T8_A, like anti-T5, defined a 33,000-M_r antigen. Taken together, our results suggest that of a possible family of 33,000-M_r glycoproteins on the human cytotoxic/suppressor T-lymphocyte subset, that which is reactive with anti-T8_A has some effect on the cytolytic mechanism.