Human blood-group MN and precursor specificities: structural and biological aspects

• Published in: Carbohydrate research 1975-03, Vol.40 (1), p.183-192
• Main Authors: Springer, Georg F., Desai, Parimal R.
• Format: Article
• Language: English
• Subjects: ABO Blood-Group System; Animals; Antigens; Blood Group Antigens; Carbohydrates - analysis; Erythrocytes - immunology; Escherichia coli - enzymology; Galactosidases; Hemagglutination Inhibition Tests; Hemagglutination Tests; Humans; Neuraminidase; Rabbits - immunology
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/S0008-6215(00)82680-4

The human blood-group MM and NN antigens carry 2 to 4 immunodominant groupings per repeating subunit and differ only by one sialic acid residue per immunodominant group. This residue covers in the MM antigen the β- D-galactopyranosyl group that is terminal in the N immunodominant structure and that, together with a terminal α-linked N-acetylneuraminic acid residue, is responsible for N specificity. M specificity was readily converted into N specificity by mild acid treatment. N structure is the immediate biochemical precursor of M structure, and M and N antigenic specificities are not determined by two allelic genes as believed hitherto. The NN antigen was inactivated by β- D-galactosidase as well as by removal of N-acetylneuraminic acid. Some of the reactivities of the NN antigen, lost upon β- D-galactosidase treatment, reappeared on subsequent partial N-acetylneuraminic acid removal. The structure uncovered by complete sialic acid depletion of MN antigens is the Thomsen—Friedenreich T antigen, the specificity of which is determined by β- D-galactopyranosyl groups. β- D-Galactosidase treatment transformed the T antigen into one possessing Tn activity. The significance of blood-group MN active substances extends to human breast cancer, where MN antigens were found in benign and malignant glands, but some of their precursors in cancerous tissue only.