Hepatitis B antigen - an incomplete history.

Hepatitis B virus still cannot be grown in an in vitro system; therefore, research into hepatitis B antigen (HB Ag) is limited to laboratory methods such as serology, electron microscopy, and biochemistry. These have established the presence of two distinct antigenic components of HB Ag, that associated with the small forms and the outer covering of the Dane particle (HBs Ag), and that of the Dane particle core (HBc Ag). Current findings make it almost certain that the Dane particle represents the hepatitis B virus (HBV), the smaller forms of the antigen representing excess viral lipoprotein. The group of individuals positive for the antigen are considered and the immunopathology of the disease is discussed. Present understanding of the antigen has made it possible to consider the use of HBs Ag as a means of vaccination. However, further information on the immune mechanisms associated with HB Ag are required before this can be accepted as a general means of protection. Finally, looking at currently available techniques, it would appear that passive hemagglutination and radioimmunoassay are both highly specific and sensitive methods of screening for HB Ag.