Cellular and humoral immunity in viral hepatitis.

Cellular and humoral immunity combine to determine the outcome following exposure to hepatitis virus and are implicated in the proposed pathogenetic mechanism for acute and chronic hepatitis. Although antibody to HBsAg is found in virtually all following recovery from hepatitis B, a cell-mediated response to HBsAg can be detected in most patients during the acute phase, and it has been suggested that this may cause the acute hepatic damage by an attack on virus-infected cells. Patients who have chronic active hepatitis also frequently have cell-mediated immunity to HBsAg, regardless of whether the antigen can be detected in their sera; thus, previous exposure to hepatitis B may be important in initiating the disease even in antigen-negative cases. Cell-mediated responses to liver-specific lipoprotein, a membrane antigen, occur transiently in many patients who have acute hepatitis and are persistent in virtually all with untreated chronic active hepatitis. The relative importances and precise mechanisms of these immune responses in the pathogenesis of acute and chronic hepatitis remain to be determined.