C-Type Lectins and Sialyl Lewis X Oligosaccharides: Versatile Roles in Cell–Cell Interaction

Carbohydrates are major components of the outer surface of mammalian cells and these carbohydrates are very often characteristic of cell-types and developmental stages (Feizi 1985; Hakomori 1985). One of such cell type–specific carbohydrates is sialyl Lewis X, NeuNAcα2→3Galβ1→4(Fucα1→3)GlcNAc→R. Sialyl Lewis X and Lewis X, Galβ1→4(Fucα1→3)GlcNAc, were originally discovered as differentiation antigens specific to granulocytes and monocytes (Fukuda et al. 1984; Mizoguchi et al. 1984). These oligosaccharides can be synthesized when α1,3-fucosyltransferase(s) is present (Maly et al. 1996). Erythroid cells, which lack the α1,3-fucosyltransferase, in contrast, express α1,2-fucosyltransferase. Resultant H-type oligosaccharides (O blood type), Fucα1→ 2Galβ1→4GlcNAcβ1→R, are converted to A and B blood group antigens by addition of α1,3-linked N-acetylgalactosamine or galactose through erythroid cell specific expression of two unique glycosyltransferases (Hakomori 1985). These results show a typical example...