ConA-induced hepatitis observed in PKC-h2/2 mice. First, both the percentage of NKT cells and their absolute number were reduced in liver. This reduction in NKT cells is not restricted to liver, as reduced numbers of NKT cells were also observed in the spleen, bone marrow and thymus. That numbers of thymic NKT cells were significantly reduced suggests 7 February 2012 | Volume 7 | Issue 2 | e31174 PKC-h2/2 NKT up-regulate FasL, TRAIL and CD40L normally Upon activation, NKT cells up-regulate FasL, TRAIL and CD40L, which contributes to ConA-induced hepatitis by induction apoptosis. Therefore, we examined their expression after ConA stimulation. There were no obvious difference in FasL, Trail and CD40L levels on NKT cells between WT and PKC-h2/2 mice before or after ConA challenge, although stimulation up-regulated their levels as expected. In addition, examination of expression of DR5, the ligand for Trail, on hepatocytes were found no difference between WT and PKC-h2/2 mice. These results suggest that it is Ridaforolimus unlikely that FasL, Trail and CD40L contribute to the hepatitis-resistance exhibited by PKC-h2/2 mice. PKCtheta in Hepatitis 8 February 2012 | Volume 7 | Issue 2 | e31174 PKCtheta in Hepatitis that development of NKT cells requires PKC-h, which is also confirmed by other observations. However, it was not clear at which stages NKT cell development was blocked. Our results demonstrated a significant reduction in NKT cells starting from the earliest developmental stages, suggesting PKC-h has a critical function during early NKT development. Further analysis “1656303 of stages 13 showed that lack of PKC-h lead to block NKT cell development at stages 1 and 2 but not so much at stage 3, suggesting that PKC-h-mediated function is more important for stage 1 and 2 NKT cell development than that of stage 3. We have shown previously that PKC-h regulates NF-kB activation, and NF-kB is apparently required for NKT development. However, deletion of NF-kBp50 arrested NKT cell development at stage 2, which is a later stage than what we observed in PKC-h2/ 2 mice. In addition to the NF-kB pathway, we and others have shown that PKC-h also regulates signaling pathways such as AP1 and NFAT. It is likely that PKC-h-regulated AP1 or NFAT or both may play a role in early stages of NKT cell development. The critical role of PKC-h in NKT development is in contrast to conventional T cells, in which development is largely independent of PKC-h, and it remains to be determined why PKC-h is specifically required for the development of NKT cells. In addition to reduced NKT cell number, defective NKT cell activation also contributes to ameliorated hepatitis in PKC-h2/2 mice. Inflammatory cytokines such as IFNc, IL-4 and TNFa that are produced by activated NKT cells are essential mediators for induction of hepatitis. We found that NKT cells activated by OCH in the absence of PKC-h produced much less IFNc, IL-4 and TNFa. Consistent with this, fewer NKT cells from PKC-h2/2 
mice produced IFNc and IL-4 ” in vitro and in vivo, suggesting that reduced total number of NKT cells likely contributes to the reduced serum TNFa. Interestingly, upon ConA treatment, TNFa, which was lower in PKC-h2/2 mice 1 hr after stimulation, but has no obvious difference 2 hr and 6 hr after stimulation. It is important to emphasize here that other cells such as macrophages also produce TNFa upon activation. Therefore, it is possible that TNFa produced by other cells may contribute to the increased TNFa leve
