Monomeric (7S) IgM in primary biliary cirrhosis.

Monomeric (7S) IgM was measured in 25 patients with primary biliary cirrhosis and 25 age- and sex-matched controls by simple double immunodiffusion in the polyacrylamide gel. 7S IgM was detected in a quarter of the patients and in none of the controls. The presence of 7S IgM was related to the elevation of total IgM as measured by radial immunodiffusion techniques. Patients with 7S IgM had significantly higher levels of cryoglobulins and immune complexes in their sera than 7S IgM-negative patients. In addition, serum alkaline phosphatase concentrations were more elevated in the 7S IgM-positive patients than in the 7S IgM-negative patients, reflecting more extensive bile duct damage. The presence of monomeric (7S) IgM and other differences in the IgM molecule may be significant for the pathogenesis of primary biliary cirrhosis.