Brief DetTnitive Report

Helper T cells play a crucial role in the induct ion and amplification of humoral and T cell-mediated immune responses in man. For example, helper T cells are absolutely required for the polyclonal immunoglobul in response triggered by pokeweed mitogen (PWM) (1) as well as for antigen-specific an t ibody responses to virus (2), soluble proteins (3), hapten (4), and heterologous erythrocytes (5). Moreover, helper T cells markedly facilitate the in vitro generation of allospecific (6) and altered self-reactive (7) cytotoxic T lymphocytes (CTL) from O K T 8 ÷ C T L precursors. Al though help for B cells and C T L precursors is mediated, predominant ly , by the T4 +, T 8 T cell subset, it is not established whether a single helper T cell pool regulates both arms of the immune response, or if functionally distinct h u m a n helper T cell subpopulat ions exist. To address this question we have analyzed the immunoregulatory activities of several HLA-DR-l-speci f ic , alloproliferative, h u m a n T cell lines (TCL) recently established in our laboratory (8). Our results demonstrate that helper T C L which trigger polyclonal ant ibody product ion by B cells are distinct from those which amplify the generation of allospecific CTL.