THE LE(X) CARBOHYDRATE SEQUENCE IS RECOGNIZED BY ANTIBODY TO L5, A FUNCTIONAL ANTIGEN IN EARLY NEURAL DEVELOPMENT

The L5 antigenic determinant was previously suggested to be a carbohyd rate epitope present on murine cell recognition molecules in the devel oping brain and to be an early neural marker in the chick embryo. Here , we show that L5 immunoreactivity is associated with complex-type N-g lycosidic oligosaccharides. To identify the carbohydrate structure rec ognized by the L5 antibody, we investigate its binding to N-linked oli gosaccharides derived from L5 glycoproteins and to known glycans. Resu lts of mass spectrometric analyses of L5-positive neoglycolipids prepa red from L5 glycoproteins are consistent with those for N-glycans cont aining a 3-fucosyl N-acetyllactosamine sequence, We also investigate L 5 binding to structurally defined, lipid-linked oligosaccharides based on the blood group type I and II backbones. Chromatogram binding assa ys, ELISA, and inhibition studies show that the antibody reacts strong ly with carbohydrate chains presenting the 3-fucosyl N-acetyllactosami ne sequence [Lewis(x) (Le(x)) or X-hapten] also recognized by anti-SSE A-1 and anti-CD15. Histochemical studies with different antibodies rec ognizing the Le(x) sequence show partially overlapping patterns of imm unoreactivity during early neural development in the chick embryo. The refore, we suggest that the epitope recognized by L5 antibody is close ly related to those for anti-SSEA-1 and anti-CD15.