Human C3a-mediated suppression of the immune response. I. Suppression of murine in vitro antibody responses occurs through the generation of nonspecific Lyt-2+ suppressor T cell.
C3a derived from the third component of human complement was found to suppress in vitro murine anti-SRBC responses. C3a-mediated suppression occurs through the generation of nonspecific Lyt-2+ suppressor T cells. The generation of suppressor cells occurs at an early phase in the response because incubation of naive T cells with C3a for as little as 30 min results in suppression of the anti-SRBC response. The generation of suppressor T cells requires the interaction of T cells, C3a, and a Sephadex G-10-adherent cell, presumably a macrophage. Although the mechanism of action of these suppressor cells has not been elucidated, several possibilities have been eliminated. C3a-suppressor T cells do not apparently release inhibitory lymphokines, nor is helper cell activity inhibited by a 2-day co-culture with these suppressor cells. The observation that interleukin 2 (IL 2)-containing lymphokine preparations could overcome C3a-induced suppression led us to investigate the interaction of the suppressors with IL 2 producer cells. However, neither C3a nor C3a-generated suppressor T cells can block the synthesis of IL 2.
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D000818:Animals; D000917:Antibody Formation; D000950:Antigens, Ly / Q000032:analysis*; D003176:Complement C3 / Q000276:immunology*; D015926:Complement C3a; D007165:Immunosuppression Therapy; D007376:Interleukin-2 / Q000032:analysis; D007700:Kinetics; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D000950:Antigens, Ly; D003176:Complement C3; D007376:Interleukin-2; D015926:Complement C3a