Abnormalities in the oligosaccharide moieties of immunoglobulin G in patients with myotonic dystrophy

Changes were identified in the glycosylation profiles of immunoglobulin G (IgG) from 15 patients with myotonic dystrophy (MyD). IgG oligosaccharides released by glycoamidase A were labeled with the fluorescent compound 2-aminopyridine and separated by HPLC. The structural changes in the oligosaccharide moieties of IgG in these patients were characterized by marked increases in agalactosyl oligosaccharides and decreases in digalactosyl oligosaccharides. Furthermore, the ratio of the level of Galβ4GlcNAcβ2Manα6(GlcNAcβ2Manα3)Manβ4GlcNAcβ4(Fucα6)GlcNAc to the level of GlcNAcβ2Manα6(Galβ4GlcNAcβ2Manα3)Manβ4GlcNAcβ4(Fucα6)GlcNAc was 1.3 in patients with MyD, while it was 2.3 in controls. These data suggest that increases in agalactosyl oligosaccharides of IgG occur in patients with MyD and it is supposed to be resulted from functional disturbance in the activity of β1, 4-galactosyltransferase.