Lineage-specific requirement for signal transducer and activator of transcription (Stat)4 in interferon gamma production from CD4(+) versus CD8(+) T cells

CD4(+) and CD8(+) T cells exhibit important differences in their major effe ctor functions. CD8(+) T cells provide protection against pathogens through cytolytic activity, whereas CD4(+) T cells exert important regulatory acti vity through production of cytokines. However, both lineages can produce in terferon (IFN)-gamma, which can contribute to protective immunity. Here we show that CD4(+) and CD8(+) T cells differ in their regulation of IFN-gamma production. Both lineages require signal transducer and activator of trans cription (Stat)4 activation for IFN-gamma induced by interleukin (IL)-12/IL -18 signaling, but only CD4(+) T cells require Stat4 for IFN-gamma inductio n via the TCR pathway. In response to antigen, CD8(+) T cells can produce I FN-gamma independently of IL-12, whereas CD4(+) T cells require IL-12 and S tat4 activation. Thus, there is a lineage-specific requirement for Statil a ctivation in antigen-induced IFN-gamma production based on differences in T CR signaling between CD4(+) and CD8(+) T cells.