Immunity and metabolism are closely linked. The liver is an important metabolic organ in the body. However, the interactions between hepatocytes and the immune system are poorly understood. In mice developing concanavalin A (ConA)-induced hepatitis (CIH), we found extensive lipid accumulation in hepatocytes. Critical enzyme involved in fat synthesis such as stearoyl-CoA desaturase 1 (SCD1) was upregulated. When we injected ConA to SCD1-deficient mice, we found these mice to be highly resistant to CIH. The mechanisms of the protective effect of SCD1 deficiency might be attributed to the reduced leptin levels in those mice, which modulated critical cytokines and signaling pathways in CIH pathogenesis. In conclusion, our study suggests that SCD1 deficiency protects mice from liver injury in a leptin-dependent manner. © 2009 USCAP, Inc All rights reserved.