Antigen-specific suppressor T cells respond to recombinant interleukin-2 and other lymphokines

Previous studies have shown that transfer of whole spleen cell populations obtained from primed donors or transfer of purified T cells enriched for suppressor activity (Ts) to recipient mice decreased the antibody response to pneumococcal polysaccharide type III (SSS-III) when the animals were simultaneously immunized with SSS-III. In the present studies, such suppression of the antibody response was transferred with 10- to 100-fold fewer primed spleen cells when the cells were treated in vitro with recombinant interleukin-2 (rIL-2) before transfer; spleen cells from naive mice or mice primed with an unrelated antigen (dextran) and then treated with rIL-2 did not cause suppression of the antibody response to SSS-III, thereby eliminating the possibility of nonspecific carryover effects induced by rIL-2. In vivo administration of rIL-2 at the time of immunization with an optimally immunogenic dose of SSS-III resulted in significant (P less than 0.05) suppression of the antibody response relative to that of control animals, suggesting that IL-2 augments the clonal expansion of Ts cells in vivo. Further, the ability of passively administered anti-IL-2 receptor antibody to inhibit generation of Ts cells in vivo is consistent with such a view. Spleen cells from primed animals treated with rIL-4, rIL-5, or gamma interferon--but not those from primed animals treated with rIL-6--likewise were able to transfer suppression of the antibody response with fewer cells than those required when primed cells not treated with lymphokines were used. Thus, these studies indicate that Ts cell activity is greatly influenced by lymphokines produced by helper T cells. The studies also suggest that these lymphokines are required during activation and/or clonal expansion of Ts cells.