Cloning the ABH genes

Cloning the ABH genesAfter the discovery of the ABO blood group system in 1900,' nearly a century passed before the molecular basis for this genetic polymorphism was elucidated.In a recent issue of Nature, wez described the nucleotide differences among the three major ABO alleles.Landsteiner' used agglutination reactions of red cells (RBCs) with serum to identify ABO blood group antigens as the first major alloantigens in humans.Early efforts to obtain any quantity of ABO-active material from RBCs encountered considerable difficulty.Later, water-soluble blood group substances, which are glycoproteins found in secretions such as saliva, were discovered and purified, and their chemical nature was determined.Immunodominant A, B, and H (0) antigens were found to be oligosaccharide structures on glycoproteins and glycolipids represented by Gal-NAcclll+3(Fucal+2)Gal, Galal+3(Fucal+2)Gal, and Fucal+2Gal, re~pectively.~.~On the basis of these structures, a hypothesis was proposed as to the pathways and genes involved in the synthesis of these antigens: A