Antigen specific suppressor T cells respond to cytokines released by T cells

These studies were conducted to examine the cytokine requirement for clonal expansion of regulatory T cells. It was observed that the in vivo administration of recombinant IL2 (rIL2), rIL5 or interferon (IFN) gamma at the time of immunization with pneumococcal polysaccharide Type III (SSS-III) resulted in substantial suppression of the antibody response in each case. Using our well established cell transfer system we found that such suppression of the antibody response could be transferred using 10-100-fold fewer primed spleen cells providing these cells were treated in vitro with rIL2 before cell transfer; spleen cells from unimmunized mice or from mice primed with an unrelated antigen and then treated with rIL2 did not cause suppression of the antibody response to SSS-III, thereby eliminating the possibility of non-specific carry-over effects induced by rIL2. We also found that the in vivo administration of anti-IL2 receptor antibody inhibited the generation of Ts cells in vivo. Spleen cells from SSS-III primed animals treated with rIL4, rIL5 and IFN gamma--but not rIL6--likewise are able to transfer suppression of the antibody response with fewer cells than that required using primed cells not treated with cytokines. Thus, these studies indicate that Ts cell activity is greatly influenced by cytokines. The studies also suggest that these cytokines may be required during the activation and/or clonal expansion of Ts cells.