Detection and quantitation of hepatitis B surface antigen immune complexes (HBsAg-ICs) by an antigen-specific method. II. Circulating immune complexes (CICs) in patients with hepatitis B and asymptomatic HBsAg carriers.

Using the PEG-trypsinisation assay, HBsAg-CICs were detected in 70% of patients with acute hepatitis B, in 5% of the asymptomatic HBsAg carriers and, in addition, in each of the 2 cases of chronic hepatitis B virus infection. In serial examinations, the complexed HBsAg levels in 77% of patients with acute hepatitis B decreased progressively in parallel with the free HBsAg levels, and persisted in the remaining 23%. In 19% of patients positive for HBsAg-CICs, the complexed HBsAg levels were higher than those of free HBsAg. No correlation was observed between results of PEG-trypsinisation and an anticomplementary assay. Artificial HBsAg-ICs in antigen excess were found to be poorly anticomplementary. C3 concentrations were normal or elevated in the majority (88%) of sera positive for HBsAg-CICs. These findings suggest that HBsAg-CICs in antigen excess are unlikely to be complement-activating. The method is useful for clinical investigation and for routine examination for HBsAg-CICs.