Introduction: NKT cells are mainly located in the liver in mice. The role of liver inherent NKT cells are still unclear.

Materials and Method: In this study, we employed mouse orthotopic liver transplantation and heterotopic heart transplantation models to critical examine the role of liver NKT cells in liver and peripheral tolerance induction.

Results: NKT cells were increased in the tolerated liver grafts which expressed higher levels of CD95L and PD-L1, while the CD4+CD25+Foxp3+ regulatory T cells (Treg) were markedly increased in the both liver and spleen at day 7 post transplantation. The heart allograft survival were prolonged significantly in the recipient which accepted donor spleen cells by portal vein (p.v.) injection in contract to the recipient which received the donor spleen cells by tail vein (i.v.) injection. In vitro immunological assay revealed that the number of NKT cells in the liver was increased and Treg were increased in both liver and spleen from the p.v. treated mice significantly. The IL-2 expression was decreased, IL-4 and IL-10 were increased. Further, significantly increased IL-4, IL-10, and IFN-γ production was detected from liver NPCs under y ”α-GalCer“/”alpha-GalCer“.

Conclusion: NKT cells are important to liver transplant tolerance induction，appear to play a key role in down regulation of peripheral immune responses and facilitate CD4+CD25+Foxp3+ Treg induction.