Primary biliary cirrhosis (PBC) is a slowly progressive autoimmune disease of the liver.Studies on the pathphysiology of this disease have demonstrated the immune-mediated destruction of the intrahepatic bile ducts and portal infammation seem to be the result of an intense autoimmune response directed against the autoantigens located in the biliary epithelium.Immunologically,PBC is characterized by the presense of antimitochodrial antibodies,elevated serum IgM and lymphoid infiltration in the portal tract.Indeed,the relationships between IgM and PBC have been a major focus of research on its pathphysiology,which lead to an increased understanding of the abnormal immune responses involved in PBC.This review summarizes data on the biological and clinical significance of Hyper-IgM in PBC,and highlights the potential role of IgM for the diagnosis and treatment of PBC.