Effects of Lyt antibodies on T-cell functions: augmentation by anti-Lyt-1 as opposed to inhibition by anti-Lyt-2.

Abstract

Monoclonal [mouse] anti-Lyt-1 (.alpha.Lyt-1) and .alpha.Lyt-2 [antibody] manifest inverse effects on allogeneic mixed lymphocyte reactions when added to the reaction mixtures without complement. .alpha.Lyt-1 augments cell proliferation and generation of cytotoxic cells but has no effect on cell-mediated cytolysis; .alpha.Lyt-2 blocks cell proliferation, generation of killer cells and cytolytic activity of killer cells. The augmenting effect of .alpha.Lyt-1 cannot be attributed to a direct mitogenic effect on T cells. Inhibition by .alpha.Lyt-2 and potentiation by .alpha.Lyt-1 require interaction of responder cells with the antibodies during the first 24 h of the mixed lymphocyte reaction, indicating that early stages of the reaction are sensitive to Lyt antibodies. The enhancing effect of .alpha.Lyt-1 on alloantigen-induced T cell proliferation is associated with augmented production of T cell growth factors. When .alpha.Lyt-1 is present in mixed lymphocyte cultures, the supernatant media collected after 24 or 48 h of culture induce higher proliferation of activated T cells compared to media of mixed lymphocyte cultures incubated in the absence of antibodies or in the presence of .alpha.Lyt-2 which has no effect on secretion of growth factors. The differences in the effects of .alpha.Lyt-1 and .alpha.Lyt-2 could not be attributed to differences in H chain constant region functions because both were of the same .gamma.2a Ig class and were used at the same concentration. A possible role for Lyt-1 molecules in early activation and mitogenesis processes such as production of growth factors was suggested.