HETEROGENEITY OF CARBOHYDRATE MOIETIES OF IGA1 MOLECULES FROM IGA NEPHROPATHY PATIENTS AND NORMAL INDIVIDUALS

IgA nephropathy (IgAN) is characterized by the deposition of IgA1 in k idney mesangia and the presence of IgA1-containing immune complexes in the circulation. Structural studies of IgA1 isolated from sera of IgA N patients indicated a statistically significant decrease in the conte nt of galactose (Gal). Using a combination of lectins specific for gly cans in O- or N-linked glycan side chains, this Gal deficiency was res tricted to O-linked glycans present in the hinge region of IgA1 molecu les. Gal-deficient IgA1 displayed a significantly higher binding to me sangial cells through a putative non-internalizing receptor specific f or N-acetyl galactosamine (GalNAc) in O-linked glycans. These data sug gest that Gal deficiency results in diversion of IgA1 molecules from t he usual degradative pathway and deposition of altered IgA1 in the mes angium.