F-antigen: nature, liver specificity, and release in experimental liver injury.

F-antigen is a liver-specific antigen detected with antibody, raised in allogeneic (CBA) mice, to BALB/c mouse liver extract. The authors have confirmed the hepatic specificity of this antigen by showing it to be absent in extracts of extrahepatic organs of mouse and human origin. It is present in liver extracts of guinea pigs, rats, and rabbits, as well as in liver extracts from mouse and human sources. The antigen was present in the circulation of rabbits with acute carbon tetrachloride-induced hepatocellular injury. It was also demonstrated in the sera of 3 of 8 patients with acute hepatitis B antigen-positive hepatitis and in 1 of 4 patients with chronic active hepatitis. It was absent from the sera of 121 other patients with a variety of hepatic and nonhepatic diseases, and from the sera of 20 healthy subjects. The antigen is immunologically distinct from hepatitis B antigen, from the liver-specific lipoprotein antigen LP-2 of Meyer zum Buschenfeld, and from each of 15 individual human serum proteins tested.