Dendritic cell (DC)-dependent activation of liver NKT cells triggered by a single i.v. injection of a low dose (10-100 ng/mouse) of alpha-galactosyl ceramide (alphaGalCer) into mice induces liver injury. This response is particularly evident in HBs-tg B6 mice that express a transgene-encoded hepatitis B surface Ag in the liver. Liver injury following alphaGalCer injection is suppressed in mice depleted of NK cells, indicating that NK cells play a role in NK T cell-initiated liver injury. In vitro, liver NKT cells provide a CD80/86-dependent signal to alphaGalCer-pulsed liver DC to release IL-12 p70 that stimulates the IFN-gamma response of NKT and NK cells. Adoptive transfer of NKT cell-activated liver DC into the liver of nontreated, normal (immunocompetent), or immunodeficient (RAG(-/-) or HBs-tg/RAG(-/-)) hosts via the portal vein elicited IFN-gamma responses of liver NK cells in situ. IFN-beta down-regulates the pathogenic IL-12/IFN-gamma cytokine cascade triggered by NKT cell/DC/NK cell interactions in the liver. Pretreating liver DC in vitro with IFN-beta suppressed their IL-12 (but not IL-10) release in response to CD40 ligation or specific (alphaGalCer-dependent) interaction with liver NKT cells and down-regulated the IFN-gamma response of the specifically activated liver NKT cells. In vivo, IFN-beta attenuated the NKT cell-triggered induction of liver immunopathology. This study identifies interacting subsets of the hepatic innate immune system (and cytokines that up- and down-regulate these interactions) activated early in immune-mediated liver pathology.