Modifications of N-Acetylneuraminic Acid and Their Influence on the Antigen Activity of Erythrocyte Glycoproteins

Abstract

The erythrocyte glycoprotein-bound N-acetylneuraminic acid which determines the blood groups MN and the autoantigens Pr1/Pr2 was modified and investigated with regard to antigen activities. We confirmed the results of Lisowska and Morawiecki, who inactivated MN antigenicity by acetylating the 6-amino group of lysine of erythrocyte glycoproteins, suggesting that electrostatic interactions between carboxyl groups of N-acetylneuraminic acid and side-chain lysyl amino groups ensure stable MN antigens. Further support for this concept was provided by our observation that amidation of the N-acetylneuraminic acid carboxyl groups also abolished MN antigenicity. A further differentiation between the autoantigens Pr1 and Pr2 was elucidated by oxidation of polyhydroxy side chains of N-acetylneuraminic acid.