Blood group ABH antigens on human cord red cells. Number of H antigenic sites and their distribution among different classes of membrane constituents.

When the blood group H sites of cord erythrocytes obtained from newborn infants of groups O, A, B and AB were labelled specifically by incubation of the whole cells with the A1 gene dependent alpha-N-acetylgalactosaminyl transferase in the presence of UDP-N-acetyl [14C]-galactosamine, the incorporation of radioactivity was considerably lower than that found for cells from adults. Based on the amount of label recovered in the membranes, average values of 326,000 H sites per single O cell and 68,000 H sites per single A, B and AB cell were calculated. Following fractionation of the stromal blood group substances thus labelled, it was found that, on the average, 66% of the radioactivity was bound to glycoprotein material, 2.7% to glycosphingolipids with short carbohydrate chains, and about 24% to polyglycosylceramides. As these values are similar to those previously determined for O cells from adults, this result shows that there are probably no substantial differences between erythrocytes from adults and newborn infants concerning the overall membrane disposition, but rather provides evidence for variations in the carbohydrate chains of the stromal glycoconjugates.