Because many chronic liver diseases are characterized by lymphocytic infiltration of the liver and several have increased immunoglobulin (Ig) production, the role of CD40-CD154 in hepatic Ig production was investigated in patients with primary biliary cirrhosis (PBC), primary sclerosing cholangitis, autoimmune hepatitis (AIH), hepatitis C, hepatitis B, alcoholic and non-alcoholic steatohepatitis, as well as normal controls.