CHARACTERIZATION OF BLOOD-GROUP-ABO(H)-ACTIVE GLYCOSPHINGOLIPIDS IN TYPE-AB HUMAN ERYTHROCYTES

Neutral glycolipids in Folch's upper phase were isolated from human er ythrocyte membranes of 22 individuals with blood type AB. On immunosta ining by TLC with anti-A IgG, all reactive glycolipids in type A corre sponded to reactive glycolipids in type-AB erythrocytes. With anti-B I gM, all reactive glycolipids in type-B erythrocytes also corresponded to reactive glycolipids in type-AB erythrocytes. By comparison of the reactivity to that of the anti-A and anti-B antibodies, it was found t hat, in type-AB erythrocytes, all glycolipids reactive with either one of the anti-A of anti-B antibodies were detected in both type-A and t ype-B erythrocytes, and that A-active glycolipids had higher R(f) valu es than B-active glycolipids on TLC plates. A series of glycolipids re active with both antibodies were purified from the Folch's upper neutr al glycolipid fraction of erythrocyte membranes by column chromatograp hy, and was characterized by TLC-immunostaining and negative secondary -ion mass spectrometry. The results strongly suggested that A-active a nd B-active carbohydrate chain epitopes existed separately as glycolip id molecules in blood-type-AB erythrocytes. It was also confirmed that these phenotypes observed in erythrocyte membranes were exhibited by blood-group-active glycosphingolipids in the small intestine of blood- type-AB individuals. Furthermore, upon treatment of fractions obtained from silicic acid column chromatography with alpha-N-acetylhexosamini dase or alpha-galactosidase, a branched hybrid-type molecule with both A and B determinants was not detected.