Inhibition of human anti-Gd cold agglutinins by sialyllactose

Two examples of IgM kappa-monotopic cold agglutinins occurring in patients with non-Hodgkin lymphomas, reacted with erythrocyte autoantigens, which were protease-resistant but were inactivated by neuraminidase. The cold agglutinins were inhibited by the trisaccharide sialyllactose [NeuNAc(alpha,2 leads to 3) Gal (beta, 1 leads to 4)Glc], which is not related to oligosaccharides known to inhibit anti-I/-i cold agglutinins, Anti-Pr cold agglutinins are not inhibited by sialyllactose, although N-acetylneuraminic acid (NeuNAc) is an essential component not only of Gd but also of Pr determinants. Gd determinants are not bound to erythrocyte membrane glycoproteins, but are apparently bound to membrane glycolipids (gangliosides).