Hepatitis-associated antigen (HAA). II. A survey of antisera from different sources and species.

Thirty-two antisera against the hepatitis-associated antigen (HAA) were studied for titer and specificity. Titers were expressed in milligrams of the antigen precipitated by one milliliter of the antiserum. Specificity was investigated by Ouchterlony double diffusion against 40 HAA-positive sera and a serum pool consisting of about 200 HAA-positive specimens. Antiserum titers ranged from 0.04 mg/mI to 4.52 mg/mI. With some antisera, titers of 0.11 mg/mI or lower gave questionable or falsely negative results for specimens with high antigen concentrations, with use of counter-electrophoresis. By the classic criterion of spur formation in Ouchterlony double diffusion, antibody specificities were not different among the antisera studied. A relatively high number of falsely negative reactions was obtained with some antisera in double diffusion, which could not be explained by excess of either antigen or antibody. Several of our observations and those of others are cited to offer tentative explanations.