Arthritis associated with chronic active hepatitis: complement activation and characterization of circulating immune complexes.

Circulating immune complexes were identified in cryoproteins isolated from serial serum samples from 6 to 10 patients with chronic active hepatitis (CAH) with frank arthritis and arthralgias. These immune complexes were not detectable in patients with uncomplicated CAH. Only cryoprecipitates from CAH patients with frank arthritis contained IgG, IgM, IgA, and complement components C3, C4, and C5. Hepatitis B surface antigen was concentrated several-fold in the cryoprotein immune complexes as compared with the serum concentration. The C3 activator fragment of the properdin complex was found in fresh serum in all patients with arthritis but was undetectable in patients with arthralagias and uncomplicated CAH. Thus, the presence of circulating complement-fixing immune complexes in patients with alternate complement pathways, and suggests that they play an important role in the pathogenesis of the arthritis.