Immune electron microscopic study of hepatitis B virus associated antigens in hepatocytes

In order to elucidate the localization of HBV-associated antigens including nonstructural forms, immune electron microscopic study was carried out in liver tissues obtained from 96 cases of chronic liver diseases with persistent HBs antigenemia and asymptomatic HBsAg carriers. The results obtained were as follows. 1) HBsAg was localized in the cytoplasm with two different patterns: an intracytoplasmic localization and a diffuse membranous localization. 2) Most cases showing membranous localization of HBsAg were associated with HBeAg in serum and the existence of core and Dane particles in the hepatocytes. 3) Antigenicity of HBsAg was found on the outer coat of Dane particles and cisternal membrane of dilated endoplasmic reticulum (ER) in addition to the plasma membrane. Some of the antigen positive ER were detected close to the plasma membrane, suggesting that the membranous localization of HBsAg was presumably resulted from the exocytosis of the antigen positive ER. These findings suggest that HBsAg expressed on the plasma membrane is a very likely target antigen in the course of cytolysis mediated by immunological mechanism. 4) HBcAg and HBeAg were localized in the cytosol of the hepatocyte in addition to the nucleus, but never found on the plasma membrane.