EFFECTS OF SURAMIN ON THE IMMUNE-RESPONSES TO SHEEP RED BLOOD-CELLS IN MICE .1. INVIVO STUDIES

The effect of Suramin on the cell-mediated delayed-type hypersensitivity (DTH) and the humoral immune responses elicited in mice by sheep erythrocytes was studied. Administration of Suramin, at various times before or after antigenic sensitization, results in a profound inhibition of cell-mediated responses but has no adverse effect on antibody production. Suramin was particularly effective when given during the effector phase of DTH; mice which were treated with this drug, 4 days after immunization, at the time of skin testing, exhibit negative or low DTH responses compared to control mice. Evidence is presented that this short-term Suramin-induced suppressive effect on the expression of DTH is related to a defective recruitment, by sensitized T lymphocytes, of phagocytic cells at the site of the inflammatory reaction. In addition, when treatment with Suramin precedes by 8 days (Day-8) or by 1 h sensitization with sheep erythrocytes for DTH, decreased DTH reactions over controls were observed. The inhibitory effect exerted by Suramin administered on Day-8 can be reversed by increasing the dose, from 106 to 108 sheep erythrocytes, of the sensitizing antigen. In this case, Suramin may interfere with the generation of DTH-mediating cells through a rapid degradation of antigen related to the Suramin-induced hyperplasia of the mononuclear phagocyte system. In contrast, DTH anergy in mice treated with Suramin 1 h before sensitization is maintained regardless of the sensitizing antigen dose. Suramin does not prevent the induction of DTH-mediating cells and the expression of these latter is apparently inhibited by suppressive cells which are generated as a result of drug treatment.