An increase in circulating IgA antibodies to gliadin in IgA mesangial glomerulonephritis

In IgA glomerulonephritis (GN), the pathogenic role of IgA is well documented, but the specificity of these IgA is unknown. Cases of celiac disease associated with IgA GN have been reported and led us to investigate the role of gliadin sensitivity. We measured IgA, IgG and IgM antibodies to gliadin, beta-lactoglobulin and ovalbumin by ELISA (results expressed as optical density; OD) in 27 patients with primary IgA GN, 14 with membranous GN (MGN), 21 with idiopathic nephrotic syndrome (INS) and 21 healthy controls. The normal value for antigliadin IgA was less than 0.650 OD. 19/27 patients with IgA GN had a raised level versus 2/14 in MGN and 2/21 INS (p less than 0.001: IgA GN vs. MGN, INS and controls). Antibodies to beta-lactoglobulin were rarely found and were not more frequent in IgA GN. Cross-reactivity with reticulin was investigated in 16 patients who were serum-positive for IgA antigliadin: no reticulin antibodies were detected by immunofluorescence. Antigliadin IgA are of diagnostic value for distinguishing IgA GN from other GN, with a sensitivity of 70%, a specificity of 89%, a positive predictive value of 83% and a negative one of 79%.