Blood-group antigens NN and Me-Vg were obtained as homogeneous substances from human red cells and meconium, respectively, and fully characterized chemically and biologically. For the first time a homogeneous erythrocyte membrane component of such high blood-group activity is described. Both substances induce anti-N specific antibodies in rabbits. They are also highly potent myxovirus receptors. The N and myxovirus specificities of the erythrocyte antigen are destroyed by sialidases and by proteases. Human N specificity is also destroyed by galactose oxidase. Specificities are carried by sialyl, sialylgalactopyranosyl, and P-galactopyranosyl structures. Both antigens are glycoproteins containing sialic acid, galactose, galactosamine, glucosamine, and mannose as the main carbohydrates. The Me-Vg antigen in addition contains a T here are at least 14 human blood-group systems with over 60 blood-group antigens (cf. Race and Sanger, 1962; Wiener, 1963) whose mosaic structures are believed to be the products of one or more genes and their allelomorphs. Until recently chemical knowledge was confined to members of the two closely related ABH(0) and Lewis systems (Kabat, 1956;Morgan, 1960; Watkins, 1966). Most of this chemical information is based on studies, not of red cells, but of the abundant water-soluble substances in secretions which are similar in serological specificity to the ABH(0) and Lewis structures on human erythrocytes.The first conclusive chemical evidence on the second human blood-group system to be discovered, the M N system (Landsteiner and Levine, 1928; cf. Wiener, 1%3), was provided by Springer and Ansell (1958) and independently, shortly thereafter, by Makela and ~ __.________ ment is maintained by the Susan Rebecca Stone Fund for Immunochemistry. t On leave from Fukushima Medical College, Fukushimashi, 3254 Japan.large amount of fucose. Components migrating on paper chromatograms like N,O-diacetylneuraminic acid have been identified in these antigens. This is the first account of these substances in products of human origin. The peptide part amounts to 44% in the NN antigen and to 13 % in the Me-Vg antigen. Threonine and serine are prominent in both glycoproteins; the concentration of aromatic amino acids is low. Tryptophan and cystine are absent. Alkali degradation studies show that the threonine and serine are involved in the peptide-carbohydrate linkage; galactosamine and galactose are the carbohydrates destroyed by alkali in the NN antigen and glucosamine in addition in the antigen from meconium. Haptenic structures in which sialic acid and galactose predominate have been isolated by enzymatic and mild acid hydrolysis.Cantell (1958), who showed that strains of type A and B influenza viruses inactivated the M and N antigens of human erythrocytes. Since then glycoproteins of varying purity and with different degrees of blood-group M and N activity together with ABH(0) activity isolated from human erythrocyte stroma have been described (Baranowski et a[. Klenk and Uhlenbruck, 1960; Stalder and ...
