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Concanavalin A (Con A)-induced hepatitis is a T-cell-mediated murine experimental model of autoimmune hepatitis. Mice lacking Vα14 NKT cells were found to be less sensitive to this hepatitis and the MRL/Mp- Fas lpr/lpr (MRL/lpr; i.e. Fas deficient) mice were also less sensitive. We report herein that MRL/Mp- Fas lpr/lpr- Sap rpl/− (MRL/lpr/rpl) mice lack Vα14 NKT cells and are deficient in the Fas antigen but sensitive to Con A-induced hepatitis. The signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) is an adaptor molecule containing a Src homology 2 (SH2) domain. We previously reported new mutant mice found among MRL/lpr mice and revealed that SAP deficiency led to the regression of autoimmune phenotypes in mutant MRL/lpr/rpl mice. It was also revealed that CD4+ and CD8+ T cells were effector cells and that blockade of 2B4, one of the SLAM family receptors, inhibited the induction of hepatitis in MRL/lpr/rpl mice. These data suggest that signals mediated by molecules other than SAP from 2B4 in T cells played important roles in the induction of hepatitis in MRL/lpr/rpl mice. [ABSTRACT FROM AUTHOR]