STRUCTURAL AND IMMUNOCHEMICAL IDENTIFICATION OF LE(A), LE(B), H-TYPE-1, AND RELATED GLYCOLIPIDS IN SMALL-INTESTINAL MUCOSA OF A GROUP-O LE(A-B-) NONSECRETOR

Total nonacid glycosphingolipids were isolated from small intestine mu cosal scrapings of a red cell blood group O Le(a-b-) nonsecretor cadav er. Glycolipids were extracted and fractionated into five fractions ba sed on chromatographic and immunostaining properties. These glycolipid fractions were then analysed by thin-layer chromatography for Lewis a ctivity with antibodies reactive to the type 1 precursor(Le(c)) H type 1 (Le(d)), Le(a) and Le(b) epitopes. Fractions were structurally char acterized by mass spectrometry (EI-MS and EI-MS/MS-TOF) and proton NMR spectroscopy. EI-MS/MS-TOF allowed for the identification of trace su bstances in fractions containing several other glycolipid species. Con sistent with the red cell phenotype, large amounts of lactotetraosylce ramide (Le(c)-4) were detected. Inconsistent with the red cell phenoty pe, small quantities of Le(a)-5, H-5-1 and Le(b)-6 glycolipids were im munochemically and structurally identified in the small intestine of t his individual. By EI-MS/MS-TOF several large glycolipids with 9 and 1 0 sugar residues were also identified. The extensive carbohydrate chai n elongation seen in this individual with a Lewis negative nonsecretor phenotype supports the concept that Lewis and Secretor blood group fu cosylation may be a mechanism to control type 1 glycoconjugate chain e xtension.