Characterization of blood group ABO(H)-active gangliosides in type AB erythrocytes and structural analysis of type A-active ganglioside variants in type A human erythrocytes

Several monosialogangliosides containing the type A-active epitope have bee n detected in type A erythrocytes on immunological analysis with a monoclon al antibody, and three of them were purified by repeated silica bead column chromatography and by scraping from the TLC plate. Two of these A-active g angliosides were characterized by methylation analysis by CC/MS, negative S IMS, MALDI-TOF/MS, proton nuclear magnetic resonance spectroscopy, and immu nological assays, and their structures were concluded to be as follows. A-a ctive ganglioside I: [GRAPHICS] A-active ganglioside II: [GRAPHICS] The reactivity of the purified gangliosides to the anti-A monoclonal antibo dies (mAbs) exhibited enhancement after removal of the sialic acid. Therefo re, the sialic residue has been shown to inhibit the binding to the termina l A-active epitope through the formation of an immune complex. To confirm t he presence of A- (including S-A-I, -II and -III) and B-active gangliosides , the reactivity of anti-A and -B mAbs were investigated using total gangli osides from type A, -B and -AB erythrocytes on TLC plate. The results were that the gangliosides from types A and AB showed positive reaction to anti- A mAbs, whereas in the anti-B mAbs binding the gangliosides from types B an d AB were positive. Thus, it revealed that A-active gangliosides were prese nt in type A and -AB, and B-active gangliosides in types B and AB. As there was no difference in respective gangliosides on type AB erythrocytes of 22 individuals, both A- and B-active gangliosides are equally present in type AB erythrocytes. The biological significance of these A- and B-active gang lioside variants remains vague at present. As these molecules exhibit diffe rent reactivities to the anti-A mAbs, it is very likely that they can regul ate the antigenicity of the A-epitope on the cell surface. (C) 2001 Elsevie r Science B.V. All rights reserved.