ISOAGGLUTININS ASSOCIATED WITH ABO ERYTHROBLASTOSIS*

Abstract
Placenta crossing ABO isoagglutinins were separated together with the bulk of 7S gamma2 globulins from other serum proteins by DEAE cellulose column chromatography (0.02M phosphate buffer, pH 6.3). ABO isoagglutinins which failed to cross the placenta, were eluted along with the other serum proteins by 1M NaCl. The isoagglutinin activity (acacia method) of cord blood serum occurred only in 0.02M fractions and appeared to be in equilibrium with maternal antibodies that were similarly obtained. In prenatal sera, ABO isoagglutinins in 0.02M fractions were not observed in type A, type B and 20 of 73 type 0 mothers. When the infant was incompatible, erythroblastosis was observed only when these placenta crossing isoagglutinins were resistant to inhibition by hog A or horse B blood group substances. Women with a history of offspring having erythroblastosis, and donors immunized with similar blood group substances, were all found to have this unique component of their isoimmune response. The future use of this method in prenatal tests was implied.