CUTTING EDGE - CRITICAL ROLE OF NK1(-CELLS IN IL-12-INDUCED IMMUNE-RESPONSES IN-VIVO() T)

CD1-dependent NK1(+) T cells rapidly produce IL-4 upon stimulation thr ough the TCR, These cells may therefore play an important role in the initiation of Th2 responses, Here, we show that NK1(+) T cells constit utively express receptors for IL-12 and lFN-gamma, and that IL-12 indu ces production of perforin in these cells, Moreover, while IL-12 induc es high levels of IFN-gamma and cytotoxic activity of hepatic or splen ic mononuclear cells against tumor cells, this effect of IL-12 is sign ificantly reduced in CD1-deficient mice with impaired NK1(+) T cells d evelopment, These results indicate that NK1(+) T cells play a critical role in IL-12-induced production of IFN-gamma to initiate Th1 immune responses and as IL-12-induced cytotoxic effector cells to initiate an titumor immunity.