Functional deletion of different Ly-1 T-cell-inducer subset activities by Ly-2 suppressor T lymphocytes.

T-suppressor-cell activity was analyzed by use of an intermediate culture system that allows the study of T-cell interactions in the absence of concomitant inducer effects on B cells. Activated suppressor T cells were incubated with their potential target cells [immune Ly-1+,Ly-2- (Ly-1) cells] for 24-48 hr, and then the Ly-1 cells were reisolated by removing the suppressor cells with an appropriate antiserum (Ly-2). The functional consequences of the interactions that occurred during the incubation period were then assessed. Suppressor cells deleted the functional activity of two inducer-T-cell subsets; the helper T cell, which induces B-cell production of antibody, and the T cell that induces Ly2+ T suppressor cells. This latter activity is more sensitive to suppression than is the former. As suppressor T cells inactivate the cells that are responsible for their activity (i.e., their specialized Ly-1 inducer cells), a form of negative regulation of suppressor-T-cell activity, in which the down regulation of suppressor cells is effected by their removal of their own inducer cells, can be postulated. In addition, these findings show that clonal deletion and active suppression need not be mutually exclusive mechanisms of immune unresponsiveness. Suppressor cells can produce a functional deletion of immune activity that persists after they themselves are removed, for example, by antisera, or in physiological situations by the negative form of regulation postulated.