The role of T cell differentiation markers in antigen-specific and lectin-dependent cellular cytotoxicity mediated by T8+ and T4+ human cytotoxic T cell clones directed at class I and class II MHC antigens.

Abstract The role of T cell differentiation antigens T3, T4, and T8 in the cytotoxic activity of four human cytotoxic lymphocyte (CTL) clones was investigated by using monoclonal antibodies specific for these antigens. Four CTL clones with different specificities and phenotypes were used. The clones HG-31 (T3+, T4–, T8+) and HG-38 (T3+, T4+, T8–) recognized HLA B7 and a yet unknown non-HLA A, B, C specificity, respectively. The T3+, T4–, T8+ clone JR-2-16 and the T3+, T4+, 8– clone JR-2-19 specificially recognized HLA A2 and an antigen associated with HLA DR2 and HLA DRw6, respectively. The monoclonal antibodies OKT8 and Leu 2a both inhibited only the activity of the T8+ clones HG-31 and JR-2-16, whereas the monoclonal antibodies OKT3 and Leu 4 blocked the activity of all four CTL clones. The blocking effect of the monoclonal antibodies was not due to non-specific inactivation of the CTL clones, because the inhibitory effect was neutralized in the presence of concanavalin A (Con A). The monoclonal antibodies OKT1 and OKT4 did not affect the cytotoxic activity of any of the CTL clones. The T3 antigens from the T3+, T4–, T8+ clones HG-31 showed an identical pattern on two-dimensional gels as the T3 antigens from the T3+, T4+, T8– clone HG-38. Trypsin treatment of clones HG-31 and JR-2-16 resulted in abrogation of their cytotoxic activity, but had no effect on the activity of the clones HG-38 and JR-2-19. In addition it was found that the trypsin treatment removed the T1, T8, and Leu 2a antigenic determinants from the clones HG-31 and JR-2-16, but the expression of the T3, T4, HLA A, B, C, and HLA DR remained unaltered. The expression of T1, T8, and Leu 2a and the cytotoxic activity of the clones HG-31 and JR-2-16 were restored after overnight incubation at 37°C. These data indicate that the T8 and T3 antigens are involved in different stages of the lysis mediated by CTL. Target cells that were insensitive to the cytolytic activity of the CTL clones, including trypsin-treated clones HG-31 and JR-2-16, could be lysed perfectly in the presence of Con A. This indicates that these CTL clones are also able to mediate lectin-dependent cellular cytotoxicity (LDCC). The HLA B7 and HLA A2-specific clones HG-31 and JR-2-16, respectively, lysed the HLA A, B, C-negative Daudi cells when these target cells were pretreated with Con A. None of the monoclonal anti-T cell sera had an effect on the LDCC mediated by the CTL clones, suggesting the T cell differentiation antigens recognized by the monoclonal antibodies do not play a role in LDCC mediated by the clones. These experiments demonstrate that HLA A, B, C antigens are not involved in the target structure in LDCC and that the T cell recognition structures involved in antigen-specific cell-mediated cytotoxicity and LDCC are different.