[Immune mechanisms in hepatitis B. New aspects and consequent practices]

The different types of immune responses occurring during hepatitis B virus infection are reviewed. The responses specific for HBsAg (hepatitis B surface antigen) are important in the pathogenesis of chronic liver disease. The cell-mediated immunity specific for this antigen seems to be responsible for cytolysis occurring when the antigen is located within the hepatocyte (acute and persistent hepatitis). It is also responsible for the subsequent elimination of the virus. Immune complexes in antibody excess probably provoke the lesion of fulminant hepatitis. Complexes in the zone of antigen excess, which are responsible for the extrahepatic lesions of the prodromic phase, may perhaps also play a pathogenetic role in some forms of chronic active hepatitis.