Lex glycosphingolipids-mediated cell aggregation

Glycoconjugates bearing oligosaccharide Le(x), Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3R, are found on the surface of several cell types, Although recent studies have indicated that Le(x) on both glycosphingolipids (GSL) and polylactosaminoglycans can mediate under certain experimental conditions Le(x)-Le(x) interactions, cell-cell interactions based exclusively on Le(x) GSLs have not been demonstrated. In this study we show that preincubation of nonaggregating rat basophilic leukemia (RBL) cells with purified Le(x) GSLs resulted in incorporation of the GSLs into plasma membrane, as determined by immunostaining, and formation of aggregates in the presence of Ca2+; no aggregates were formed after preincubation of the cells with globoside or sphingomyelin. Le(x)-mediated aggregation was inhibited by removal of Ca2+ or by addition of lactofucopentaose III but not by lactose or lacto-N-fucopentaose II. In a mixture of Le(x)-positive and Le(x)-negative RBL cells most of the aggregates were composed exclusively of Le(x)-positive cells, The combined data suggest that interactions between Le(x) GSL on opposite cell surfaces are strong enough to allow formation of stable cell-cell contacts.