Galactose-deficient IgA1 in sera of IgA nephropathy patients is present in complexes with IgG.
IgA1 proteins from sera of patients with IgA nephropathy (IgAN) are galactosylated to a lesser degree than those from healthy controls. The increased reactivity of intact or de-sialylated serum IgA1 with N-acetylgalactosamine (GalNAc)-specific lectins, Helix aspersa (HAA) and Caragana arborescens (CAA) and de-sialylated IgA1 with Helix pomatia (HPA) and Bauhinia purpurea (BPA) indicated that the Gal deficiency is in glycans located in the hinge region of IgA1 molecules. De-sialylated IgA from sera of 81 IgAN patients bound biotin-labeled lectin HAA more effectively than did de-sialylated IgA from 56 healthy controls (P < 0.0001). Similar results were observed for 67 IgAN patients and 52 controls with second lectin, CAA (P < 0.001). The binding patterns for 9 patients with mesangial proliferative glomerulonephritis of non-IgA origin were similar to those for controls. Incompletely galactosylated IgA1 capable of binding GalNAc-specific lectins was detected in complexes with IgG as demonstrated by ELISA, size-exclusion chromatography and sucrose gradient ultracentrifugation. The formation of IgA1-IgG complexes may affect the serum level of IgA1 by reducing the rate of its elimination and catabolic degradation by the liver.
Tomana
M
M
Department of Medicine, University of Alabama at Birmingham, USA.
Matousovic
K
K
Julian
B A
BA
Radl
J
J
Konecny
K
K
Mestecky
J
J
D000328:Adult; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005690:Galactose / Q000737:chemistry / Q000172:deficiency*; D005922:Glomerulonephritis, IGA / Q000097:blood* / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood* / Q000737:chemistry / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism*; D007075:Immunoglobulin M / Q000378:metabolism; D037102:Lectins; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D037102:Lectins; D011509:Proteoglycans; D005690:Galactose