STRUCTURAL CHARACTERIZATION OF THE OLIGOSACCHARIDES OF A HUMAN MONOCLONAL ANTILIPOPOLYSACCHARIDE IMMUNOGLOBULIN-M

The oligosaccharide side chains of a human anti-lipopolysaccharide IgM produced by a human-human-mouse heterohybridoma were analyzed at each of its five conserved N-glycosylation sites. This antibody also has a potential sixth N-glycosylation site in the variable region of its he avy chain which is not glycosylated, The oligosaccharides were release d by digestion with various endo-and exoglycosidases and analyzed by m atrix-assisted laser desorption/ionization-time of flight mass spectro metry and fluorophore-assisted carbohydrate electrophoresis, The antib ody has various complex-and hybrid-type oligosaccharide structures at Asn 171, various sialylated complex-type oligosaccharides at Asn 332 a nd 395, and high-mannose-type oligosaccharides at Asn 402 and 563, Of note is the presence in this human IgM of oligosaccharides containing N-glycolylneuraminic acid and N-acetylneuraminic acid in the ratio of 98:2 as determined using anion-exchange chromatography, Furthermore, w e observed oligosaccharide structures containing Gal alpha(1,3)Gal tha t have not been reported as components of human glycoproteins.