[Past and present studies on ABO blood group system].

The author engaged himself in the studies of ABO blood group system for the last three decades, and reviewed the progresses in this period, which were classified into following 5 items. 1. H-, A- and B-active oligosaccharides were isolated from the globoside fractions from human erythrocytes by ozonolysis. One of the H-active oligosaccharide with short carbohydrate chain is a pentasaccharide: Fuc(alpha 1-->2)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc, and the other with long carbohydrate chain is a heptasaccharide: Fuc(alpha 1-->2)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc. Hexa- or octasaccharides with blood group A- or B-activity have an additional alpha-N-acetylgalactosaminyl residue or alpha-galactosyl residue, which joints with alpha 1-->3 linkage to subterminal beta-galactose of the both of H-active oligosaccharides, respectively. 2. A blood group A-gene specified alpha-N-acetyl-galactosaminyltransferase (A-enzyme) catalyzes the transfer of N-acetylgalactosamine from the UDP-sugar to the subterminal beta-galactosyl residue of blood group H-active carbohydrate chain, and a blood group B-gene specified alpha-galactosyltransferase (B-enzyme) catalyzes the transfer of galactose from the UDP-sugar to the subterminal beta-galactosyl residue of blood group H-active carbohydrate chain, respectively. Either the A- or B-enzyme can not transfer the substrate sugar to the carbohydrate chain lacking alpha-fucosyl residue of H-determinant, and it is the reason why the synthesis of blood group A- or B-antigenic structure in inhibited in the tissues of Bombay phenotype and in the secretory glands of the nonsecretor. 3. Specific antibody either to the A- or B-enzyme can be introduced in the serum of the rabbit which was immunized with the A- or B-enzyme preparation, respectively. And immunological cross reaction is also present between the A- and B-enzyme, but the immunologically cross reactive material can not be found in the blood group O individual. The absence of immunologically cross reactive material in the blood group O individual is supported by a fact that the cross reactive antibody similar to the antibody in rabbit serum was present in the serum of the chronic myeloid leukemia patient, who was belonged to blood group B and treated with blood group incompatible bone marrow transplantation from blood group O donor, because it is acceptable to speculate that the grafted lymphocytes react to the B-enzyme in the recipient and produce the anti-enzyme antibody. 4. The immunological profiles described above are compatible with the cDNA structures of human blood group ABO alleles presented by Yamamoto F. et al. Their gene model is that the cDNAs of blood group ABO alleles are highly homologous, but the cDNA of common O allele is non-functional due to a single nucleotide deletion close to the 5'end of the coding sequence, which causes a frame shift of the codon, and results in truncated peptide. 5. Transcription of the human blood group ABO gene can be enhanced by a CBF/NF-Y which binds the minisatellite on the 5'-upstream sequence of the gene.