Demonstration of secretory IgA in kidneys of patients with IgA nephropathy

Abstract

Background. Recently we reported a possible role for secretory IgA (SIgA) in IgA nephropathy (IgAN), as suggested by increased serum levels in patients with active disease and accumulation of SIgA in a glomerular eluate. Therefore, we attempted to find support for these findings by analysis of the presence of SIgA in biopsies of IgAN patients. Methods. Renal biopsies of 26 patients with biopsy-proven IgAN were analysed for the presence of SIgA and complement proteins. Results. In 15% mesangial deposition of SIgA was demonstrated, using a specific staining for secretory component (SC) and colocalization with IgA. The presence of SIgA in these biopsies showed a strong correlation with deposition of mannose-binding lectin (MBL) and C4d. Moreover, we observed a strong colocalization between SIgA and MBL or C4d. This local complement activation has previously been linked to more severe renal disease. Conclusions. Therefore, these data provide additional evidence for a pathogenic role for SIgA in IgA nephropathy. © The Author [2007]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.