Genetics of anti-A and anti-B levels

Hemolysins and agglutinins anti-A and anti-B were measured in 401 blood group O individuals belonging to 74 families. Levels of hemolysins and saline agglutinins reached a peak during childhood and decreased thereafter. Incomplete agglutinins showed a relative increase after childhood. Hemolysins and agglutinins were higher in blacks than in whites. Whites had higher anti-A than anti-B levels and the levels were higher in females than in males. In blacks the anti-B levels were almost as high as were the levels of anti-A and little sex difference was found. Levels of hemolytic anti-A and saline anti-A were closely correlated as were hemolytic anti-B and saline anti-B but low correlations were found between anti-A and anti-B levels. Anti-A and anti-B hemolysin and agglutinin levels were positively correlated with serum IgM levels but anti-A levels were not. Isoantibody levels were not correlated with IgA, IgD, and IgE levels. Correlation and regression analysis among relatives disclosed that from 20 to 30 per cent of the total phenotypic variation in isoantibody levels was accounted for by genetic variation. Age of the individual also contributed markedly to the variation in hemolysins and saline agglutinins, but about one-half of the total variation remained unaccounted for.