Precpitation of a substance in salivas from A1 and A2 secretors.

Abstract

SummaryA‐substance molecules were precipitated from salivas from A1 and A2 secretors with a Dolichos biflorus seed extract. The amounts of precipitate formed were shown to be proportional to the agglutination inhibition titres with the extract. It is concluded that both precipitating ability and inhibition titre can be taken as quantitative measures of antigen present in saliva.The decrease in Ulex europaeus (anti‐H) and Dolichos biflorus (anti‐A) inhibition titres of the salivas during the precipitation procedure was determined. The ratio of these values was calculated for the individual salivas, and was found to be higher for the A2 than for the A1 salivas. It is proposed that individual A‐substance molecules from A1 secretors have a higher ratio of A : H antigenic determinants than have those from A2 secretors, and that one difference between the A antigens of A1 and A2 individuals, thus, has a quantitative basis. This conclusion forms part of the evidence leading to the proposal that the gene IA1 is basically a duplication of the gene IA2.