Discrimination of Antibodies to Hepatitis B surface antigen from antibodies to inherited serum protein variants in immune sera of human and animal origin.

Antisera to hepatitis B surface (HBs) antigen, both of human and rabbit origin, have been examined. The anti-HBs serum derived from a multiply transfused patient did, in addition, contain antibodies directed against the inherited beta-lipoprotein antigen Ag(x), whereas one of the rabbit immune sera also contained antibody to the inherited Lp(a) antigen. Thus, in human, as well as in animal anti-HBs sera, antibodies to inherited normal serum antigens may cause false positive reactions. This problem may be overcome by absorption procedures if appropriate control systems are available. False positive reactions caused by the Ag(x) antigen may also be avoided by use of agarose as supporting medium for the test, as Ag(x) precipitin lines do not appear in this medium. An undialysable high molecular weight component may be obtained from Oxoid "Ionagar" by washing. When this is added to agarose the Ag(x) antigen reaction appears also in this medium.