Anti-T3 antibody both activates and inhibits the cytotoxic activity of human T cell clones.

The present report outlines results using several approaches to investigate the effects of antibodies against cell surface molecules on human cytotoxic T lymphocyte (CTL) recognition. First, when interactions between CTL and targets are perturbed by antibody immobilized on the surface of the incubation vessel, anti-T3 antibody was unique in its ability to inhibit at least 10 times more efficiently than when present in solution. Second, anti-T3 antibody at sufficiently high concentrations inhibits lectin-dependent cellular cytotoxicity as well as allospecific cytotoxicity. Third, murine hybridomas expressing anti-T3 antibody induce their own lysis by human CTL clones; but hybridomas bearing antibodies of other specificities are not lysed in a similar manner. We have exploited this anti-T3 triggered lysis of the OKT3 hybridoma as a model system in which to study T cell recognition. Such lysis is susceptible to inhibition not only by anti-T3 but also by anti-LFA-1 antibody; however, conjugate formation between the anti-T3 hybridoma and CTL is not easily inhibited by anti-LFA-1. These data, which are discussed in the context of results from other laboratories, are consistent with a model in which CTL triggering can be induced by interaction of the antigen specific receptor (Ti) with its physiologic ligand, antigen plus MHC, or interaction of the T3 complex with a surrogate ligand, anti-T3/anti-Ti. However, they raise questions regarding the role which LFA-1 plays in CTL recognition.