PERFORIN AND FAS KILLING BY CD8(-CELLS LIMITS THEIR CYTOKINE SYNTHESIS AND PROLIFERATION() T)

During an immune response, effector CD8(+) T cells can kill infected c ells by the perforin-dependent pathway. In comparison to CD4(+) T cell s, which are major sources of cytokines, normal CD8(+) T cells produce d less interleukin 2 and interferon gamma, and proliferated less vigor ously after antigenic stimulation. Killing of target cells was a major cause of these reduced responses, since perforin-deficient CD8(+) T c ells showed substantially increased cytokine synthesis and proliferati on. Cytotoxicity by the alternate Fas pathway also resulted in self-li mitation of CD8(+) T cell cytokine synthesis. This relationship betwee n cytotoxicity and cytokine synthesis may regulate CD8(+) T function i n different phases of an immune response.