Biosynthesis of human blood group T-, N- and M-specific immunodeterminants on human erythrocyte antigens.

We synthesized on Tn erythrocytes with human sera, UDP-Gal, and activators T-specific haptenic structures in satisfactory yield. The specificity of this biosynthesis was ascertained by agglutination with human and animal anti-T, by specific absorption of human anti-T as well as by agglutination inhibition assays. With isolated human erythrocyte T antigen as substrate we synthesized N- and M-specific structures with sera from individual human donors in presence of CMP-sialic acid by incubation for 24 hr at 37 degrees C. Serology on the recovered product was carried out with nineteen monospecific human and animal sera under strictly standardized and controlled conditions with the mandatory tube assay. All M- as well as N-derived T antigens tested acquired N specificity with all transferase sera of all MN types. In contrast, M-activation of M- and N-drived T antigens tested acquired N specificity with all transferase sera of all MN types. In contrast, M-activation of M- and N-derived T antigens occurred only if the transferase donor had the M gene. The nine M transferase sera used all gave M-activation of MM- and NN-derived T antigens. None of twelve transferase sera from NN donors M-activated any T antigen. NN antigen was transformed to a M-specific one by all transferase sera from MM donors but by none from NN donors. We have not yet established the biochemical-genetic relation of M to N; N may be the immediate precursor of M or M may originate directly from T. The sialyltransferase responsible for M activation may be a N transferase 'modified' by the M gene product or an entirely different sialyltransferase.