The Epitope(s) Recognized by HNK‐1 Antibody and IgM Paraprotein in Neuropathy Is Present on Several N‐Linked Oligosaccharide Structures on Human P0 and Myelin‐Associated Glycoprotein

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Abstract
The mouse monoclonal antibody HNK-1 and the human monoclonal IgM antibody present in patients with polyneuropathy both recognize carbohydrate epitope(s) on human myelin-associated glycoprotein and P0. In the present study, the oligosaccharide structures that bear the antibody epitope(s) were investigated. The extracellular derivative of myelin-associated glycoprotein (dMAG) was purified by immunoaffinity chromatography. P0 was electroeluted from gel slices. Western blot analysis of whole glycoproteins demonstrated that the epitopes for HNK-1 and the human monoclonal IgM antibody were different. The glycopeptides obtained by proteolysis of purified dMAG and P0 were separated and characterized by affinity chromatography on concanavalin A-Sepharose. Both dMAG and P0 displayed heterogeneity in their oligosaccharide structures, i.e., they both contained mainly tri- and tetraantennary oligosaccharides (∼80%), although biantennary (10%) and high-mannose and/or hybrid (10%) oligosaccharides were present. The human monoclonal IgM antibody epitope was present on all types of isolated oligosaccharide structures from either dMAG and P0. The HNK-1 epitope was present on all types of oligosaccharide structures of dMAG, whereas it was present only on tri- and tetraantennary structures of P0.