Effects of suramin on the immune responses to sheep red blood cells in mice. II. In vitro studies.

The effect of Suramin on the secondary in vitro response to sheep erythrocytes (SRBC) was studied. Spleen cells from mice which were treated with Suramin immediately prior to sensitization with SRBC failed to respond to an in vitro SRBC challenge. This Suramin-induced immunosuppression is not related to a defect in macrophage or B-cell function(s). Suramin does not interfere with the induction by SRBC of radioresistant and radiosensitive helper-T-cell subpopulations. Cell separation studies, using wheat germ agglutinin, showed radiosensitive helper-T-cell function in the nonagglutinated fraction while the radioresistant helper activities are carried out by the agglutinated subpopulation. Evidence is presented that Suramin administration results in a suppressive T-cell activity which can be demonstrated in the subpopulation agglutinated by wheat germ agglutinin. The role of such suppressive T cells in the inhibitory effect exerted by Suramin on the cell-mediated delayed-type hypersensitivity response to SRBC is discussed.