Events contributing to the destruction of bile ducts in cholangitic diseases may lead to chronic and end stage liver diseases. Studies over the last decade suggest that the progressive destruction of bile ducts at an early stage in many liver diseases, including primary sclerosing cholangitis, primary biliary cirrhosis, extrahepatic biliary atresia, and allogeneic immune injury in liver transplantation, appears to involve an inflammatory response with pro-inflammatory cytokine release, which eventually mediates the progressive damage of bile ducts. This study investigates if IL-10, a potent anti-inflammatory cytokine, modulates the release of pro-inflammatory cytokines (IL-1, IL-6 and TNF-alpha) by bile duct cells and if protects injury to bile duct cells induced by TNF-alpha using a bile duct cell line. This pure clone of the mouse biliary epithelial cell line was established by Dr. K. Paradis using the transgenic mouse harboring the SV40 thermosensitive immortalizing mutant gene TsA58 under the control of the MHC Class I promoter. The immortalized bile duct cells (IBDCs) were well characterized and behaves like normal bile duct epithelial cells in many aspects in a serum-free medium (Gastroenterology, 109:1308, 1995). We found that IL-10 at concentrations of 0.4, 4 and 40 ng/ml significantly reduces the release of IL-1 (from 170 pg/ml to 10-40 pg/ml), IL-6 (from 11000 pg/ml to 500-1000 pg/ml) and TNF-alpha (from 110 pg/ml to 30-40 pg/ml) by LPS-stimulated IBDCs, Exogenous TNF-alpha, but not IL-1alpha and IL-6, induces the cell necrosis and apoptosis. IL-10 significantly increases IBDC proliferation that is inhibited by LPS. IL-10 reduces the cell necrosis induced by TNF-alpha, as determined by measurement of lactate dehydrogenase release. IL-10 significantly reduces the cell apoptosis induced by TNF-alpha, as determined by measurement of CPP32(caspase-3) protease activity, a key early event in apoptosis. IL-10 also significantly decreased the release of nitric oxide, an important inducer of cell apoptosis, by LPS-stimulated IBDCs. We conclude that IL-10 may be of therapeutic value in preventing bile duct destruction by modulating the release of pro-inflammatory cytokines and protecting bile duct cells pro-inflammatory cytokines or agents that induce cellular apoptosis and necrosis.