Feedback suppression: phenotypes of T cell subsets involved in the Ly1 T cell-induced immunoregulatory circuit.

Ly1 inducer t cells (Ly1:SI) activate resting T cells to generate potent suppressor activity. Primed Ly1:SI generated in vitro were assayed for suppression induction in cultures containing B cells and various Lyt T cell sets that had been positively and/or negatively selected using alpha Lyt sera. These experiments both reaffirm the previously reported requirement for an Ly123 T cell in suppression by Ly1:SI and implicate a third T cell subset, which is absolutely required for the full expression of Ly1:SI-induced feedback suppression. This subset of T cells has the cell surface phenotype, Ly1- Ly23+ 1J+ Qa-1-.