Primary Biliary Cirrhosis and the Complement System

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Abstract
Primary biliary cirrhosis is a disease characterized by slowly progressive intrahepatic cholestasis, destructive lesions of the septal and larger interlobular bile ducts and granulomas. It is associated with defects of both humoral and cellular immune function. As part of the detailed evaluation of these defects, the status of the complement system was evaluated. Striking abnormalities of serum complement levels are found but are difficult to interpret. The demonstration of marked hypercatabolism of C3 the C3 component of complement, but not albumin, suggests that the complement system may be in a chronically activated state. An unequivocal defect in the clearance of sensitized erythrocytes by receptors of C3b on Kupffer cells has been found. A large proportion of these receptors may be occupied either by immune complexes containing C3b or excess free C3b that is generated by complement activation. Major defects of C3 catabolism and C3b-receptor-mediated clearance are not found in patients with HBsAg[hepatitis B surface antigen]-negative chronic active hepatitis. The complement system may play a role in the pathophysiology of primary biliary cirrhosis.