Role of Ly-1:Qa1- and Ly-1:Qa1+ inducer T cells in activation of Ly-23 effectors of suppression of antibody production in mice.

Ly-2+ effectors of T cell-mediated suppression require inducing signals from antigen and a helper cell bearing the Ly-1+:Qa1+ surface phenotype. In this report, we have further examined the helper cell requirements for suppressor cell induction of antibody production in mice. By using the T cell subset education procedure in vitro, we have activated T cells to sheep red blood cells (SRBC) antigens and then purified Ly-2 cells before testing for suppressor activity in assay cultures of defined T and B cell subsets. We have confirmed our previous observations that Ly-1+:Qa1+ cells are required for activation of T suppressors, but have found that under the appropriate conditions, there is not a strict requirement for the Ly-123 subset of T cells. Furthermore, if Ly-23 cells are stimulated in the presence of Ly-1+:Qa1- T cells, effective suppressors can be obtained only if a source of Ly-1:Qa1+ inducers is added to the assay culture. If Ly-23 cells are activated by antigen in the absence of Ly-1 cells, subsequent exposure to the Ly-1+:Qa1+ subset under the conditions tested here is not sufficient to activate suppressors. These results show that effectors of suppression, like B cells and cytotoxic T lymphocytes, may respond to two helper cells.