IgA-antigliadin antibodies in patients with IgA nephropathy: the secondary phenomenon?

Circulating IgA-antigliadin antibodies (IgA-AGA) are often found in patients with IgA nephropathy (NP). IgA-AGA are sensitive markers of an abnormal immune system reaction to gluten, seen particularly in patients with celiac disease. However, a lack of IgA-antireticulin and IgA-antiendomysium antibodies and often jejunal mucosal atrophy of patients with IgA NP suggest that most patients do not have latent celiac disease. To examine the relationship between IgA-AGA and clinical data, enzyme-linked immunosorbent assays for IgA-AGA were performed in 28 patients with IgA NP and in 50 healthy persons. The results were calculated in arbitrary units (AU). The cutoff level for a negative or a positive test was found to be 60 AU, calculated according to the AGA test result (mean + 3 SD) in 50 healthy persons. The following clinical data were assessed: age, gender, disease duration, daily proteinuria, blood pressure, serum creatinine, and creatinine clearance. Control sera were negative for IgA-AGA. Positive IgA-AGA tests were observed in 14 of the 28 patients (p < 0.0001 vs. controls) and high levels of IgA-AGA (AU >90) in 6 of the 28 patients (p < 0.001 vs. controls). The mean duration of the disease of the patients with positive IgA-AGA was significantly longer as compared with the patients who had a negative antibody test. IgA-AGA correlated with age (p < 0.05, r = 0. 56), disease duration (p < 0.05, r = 0.40), and blood pressure (p < 0.05, r = 0.48). Antireticulin and antiendomysium antibody tests were negative in all patient and control sera. We conclude that IgA-AGA are associated with the progression of IgA NP. Our findings support the current concept about the pathogenesis of IgA NP, where the defective IgA production itself may be the primary and intestinal lesions as well as the production of IgA-AGA the secondary phenomenon.