Abstract
Hepatitis B surface antigen (HBsAg) bound to immunoglobulin M (IgM) was detected in sera of HBsAg carriers by a radioimmunoassay based on selective absorption of the immunoglobulin on a solid phase coated with antiserum to human IgM. Isopycnic banding and rate-zonal sedimentation have shown that the reaction is related to particulate forms of the HBsAg complexed with IgM. The binding of IgM possibly occurred because of a selective affinity of these molecules to the surface of HBsAg particles. HBsAg/IgM was found transiently in 24 of 25 (96%) patients with acute self-limited hepatitis B and persistently in 6 of 25 patients whose acute hepatitis B progressed to chronicity. It was also found in 20 of 39 (51%) chronic HBsAg carriers with inactive and asymptomatic infection. The HBsAg/IgM phenomenon is not dependent on replication of hepatitis B virions; its persistence in patients with acute hepatitis B may provide complementary evidence of transition of the infection to chronicity.