Feedback suppression: an immunoregulatory circuit.

The basic elements of the feedback suppression circuit of T cell interactions are summarized. Ly1 T cells can be stimulated directly to become inducers of Ly2+ T suppressor cells or helper cells for B cells that produce antibody to erythrocyte antigens. Ly2 cells can be activated to become suppressors only in the presence of Ly1 cells. An Ly1,2,3, cell is the acceptor of the Ly1 inducer signal. Using an intermediate culture technique, it can be shown that Ly1 inducers are a target of suppressor T cell activity.