ABH and related blood group antigens

Abstract

Abstract Antigenic determinants are trisaccharide A, 16.1, trisaccharide B, 16.2, and disaccharide H, 16.3. The reader will recognize that trisaccharides A and B are glycosidation products of disaccharide H at position 3 of galactose by an N-acetylgalactosamine unit and a galactose unit, respectively, and in the two cases by an a-anomeric linkage. Thus the A and B determinants differ only by their substitution at position 2 on their D-galacto non-reducing terminal end, N-acetyl in the A substance, and hydroxyl in the B substance. Note as well the participation of the deoxygenated sugar fucose and finally the α-1,2-cis bonds, not as common as the β-1,2-trans bonds in glycoconjugates. These disaccharides and trisaccharides are located at the non-reducing terminal ends of the oligosaccharide chains of glycoproteins and glycolipids and possibly their branches. Blood group A individuals have the A determinant and a certain quantity of H, but not B, whereas those of blood group B have B and H but not A, in a symmetrical fashion. Blood group O individuals only have the H determinant. This immediately implies an incomplete biosynthesis due to the absence or the non-expression of genes which code for the A or B glycosyltransferases. Carrier molecules are found in the membrane of erythrocytes and determinants are exposed towards the outside. In blood group A individuals, the B molecule is recognized as a foreign substance and gives rise to the appearance of anti-B antibodies. For the same reason, anti-A antibodies are found in people with blood group B and and anti-A and anti-B antibodies in those with blood group 0. Problems observed during blood transfusions were due to the presence of these antibodies. Thus the donor of blood group A who has anti-B antibodies causes the agglutination of erythrocytes in a receiver of blood group B. ABH antigens are also present on cell surfaces in the majority of organs and in secretions. Their presence is one of the major causes of the failure of organ transplants between a donor and receiver of different blood groups. For this reason, they should also be named histo-blood group antigens.