EXPRESSION OF LEWIS HISTO-BLOOD GROUP GLYCOLIPIDS IN THE PLASMA OF INDIVIDUALS OF LE(A+B+) AND PARTIAL SECRETOR PHENOTYPES

Red cell Lewis antigens are carried by glycosphingolipids passively ab sorbed from plasma. Plasma was collected from a spectrum of individual s with normal and unusual Lewis/secretor phenotypes in order to invest igate the glycolipid basis for the unusual phenotypes. Samples were ob tained from: a Le(a+b-) ABH nonsecretor who secreted Lewis substances; a Le(a+b-) partial secretor; Le(a+b+) partial secretors; Le(a+b+) sec retors; and a full range of normal Lewis/secretor phenotypes as contro ls. The Le(a+b+) samples represented Polynesian, Asian and Reunion Isl and ethnic backgrounds. Nonacid glycolipids were prepared, separated b y thin-layer chromatography, and then immunostained with potent monocl onal antibodies of known specificity. Despite different serological pr ofiles of the Le(a+b-) and Le(a+b+) Polynesian samples, their plasma g lycolipid expressions were very similar, with both Le(3) and Le(b) co- expressed. The copresence of Le(3) and Le(b) in Le(a+b+) samples is in marked contrast to Caucasians with normal Lewis phenotypes, who have predominantly either Le(3) or Le(b). These results suggest that there is a range of the secretor transferases in different individuals, poss ibly due to different penetrance or to several weak variants. We also show that Lewis epitopes on longer and/or more complex core chains app ear to be predominant in the Polynesian Le(a+b+) samples. The formatio n of these extended glycolipids is compatible with the concept that in the presence of reduced secretor fucosyltransferase activity, increas ed elongation of the precursor chain occurs, which supports the postul ate that fucosylation of the precursor prevents or at least markedly r educes chain elongation.