Interaction of lymphocytes with hepatocytes containing hepatitis B antigen: ultrastructural demonstration of target antigen and T-cell subsets by the peroxidase antibody technique.

Hepatitis B virus associated antigens and subsets of lymphocytes in liver tissue were studied using immune electron microscopy to clarify the immune mechanism of hepatocyte lysis in type B chronic hepatitis. Using conventional electron microscopy, infiltrating lymphocytes were observed in direct contact with hepatocytes in areas of piecemeal necrosis and focal necrosis; they showed various types of surface adherence with a contact gap of approximately 20 nm in width. The majority of the hepatocytes that were in contact with lymphocytes could be shown to contain HBsAg and/or HBcAg by immune electron microscopy: HBsAg was localized in the endoplasmic reticulum membranes, in tubular structures, and on the outer coat of Dane particles; HBcAg was observed in the nuclei and in the cytoplasmic matrix of hepatocytes. In some cases HBsAg was observed on the plasma membrane of hepatocyte in contact with lymphocytes. Immune electron microscopy using monoclonal antibodies to subsets of human T-lymphocytes revealed that the lymphocytes in areas of piecemeal necrosis and focal necrosis were predominantly CD 5 or CD 8 positive. In contrast, CD 4 positive cells were infrequently observed in necro-inflammatory regions and Leu 7 positive cells were randomly scattered in the sinusoids away from areas of hepatocyte necrosis. These data suggest that HBsAg is at least one of the target antigens expressed on the hepatocyte membrane possibly enabling cytolytic interaction by cytotoxic T cells in chronic type B hepatitis.