An immunochemical study on anti-N antibodies from dialysis patients

The specificity of anti-N antibodies from dialysis patients was investigated by hemagglutination in-hibition tests, using various fractionation, fragmentation and modification products of human erythrocytic membrane sialoglycoproteins. The antibodies were found to react with the N and "N' antigens on the MN and Ss glycoprotein, respectively. The NH2-terminal leucine and the side chain(s) of sialic acid(s) in oligosaccharide(s) linked to the second, third and/or fourth position(s) of the glycoproteins represent parts of the binding site for the anti-N antibodies. Formaldehyde reacts with the amino group of the NH2-terminal leucine, presumably leading to the formation of the hydroxy-methylene-derivative. These modified N antigens represent the structures triggering the formation of anti-N antibodies in dialysis patients, which cross-react with the native N receptors.