We have recently demonstrated that the function of NKT cells was enhanced in the absence of NK cells (Uchida et al. in submission). In the present study, we have demonstrated that IFN-γ levels produced by CpG-ODN-stimulated liver MNCs were significantly higher in the α-GalCer group. Moreover, because we have previously reported that NK cells produced IFN-γ after CpG-ODN stimulation24, we proposed a compensatory augmentation in the function of NK cells. Although the precise mechanisms remain to be elucidated, complementary roles may be shared between NKT and NK cells to avoid immunosuppressive states.