Immune electron microscopic demonstration of hepatitis B core antigen (HBcAg) in liver cell plasma membranes.

Immune light and electron microscopic examinations were carried out to investigate the localization of HBcAg in biopsies from patients with persistent HBs antigenemia. In biopsies with severe intralobular inflammation HBcAg was mainly observed in the cytoplasm of hepatocytes in contrast to nuclear localization in specimens with less severe histological changes. Immune electron microscopic examination demonstrated two different appearances of HBcAg, according to whether it was or was not associated with core particles. In biopsies with more severe parenchymal damage, an increased amount of non-particulate HBcAg was observed in the cytoplasmic matrix; four such biopsies with intracytoplasmic HBcAg also revealed HBcAg on the plasma membrane of the hepatocytes. These findings support the concept that HBcAg may function as a viral target antigen for the immune response in type B hepatitis.