Journal Article

An increased polymeric IgA level is not a prognostic marker for progressive IgA nephropathy

Paul J. M. van der Boog, Cees van Kooten, Anneke van Seggelen, Marko Mallat, Ngaisah Klar-Mohamad, Johan W. de Fijter and Mohamed R. Daha

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 19, issue 10, pages 2487-2493
Published in print October 2004 | ISSN: 0931-0509
Published online July 2004 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfh394
An increased polymeric IgA level is not a prognostic marker for progressive IgA nephropathy

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Background. Elution of IgA from renal biopsies of patients with primary IgA nephropathy (IgAN) has suggested that mesangial IgA deposits are mainly multimeric in nature. This macromolecular IgA consists of dimeric and polymeric IgA and may be derived from the circulation. In children with IgAN, circulating macromolecular IgA levels correlate with bouts of macroscopic haematuria, but in adults a correlation with disease activity is less clear. Therefore, we have designed a novel method to assess the levels of polymeric IgA (pIgA) in sera from patients and controls.

Methods. A novel precipitation assay using recombinant CD89 was developed to measure pIgA. Polymeric IgA levels were measured in serum samples obtained from healthy volunteers (n = 21) and patients with IgAN (n = 51). Subsequently, serum pIgA levels were correlated with clinical parameters of disease.

Results. Serum pIgA levels were significantly increased in patients with IgAN. However, pIgA concentrations relative to total IgA were significantly lower in sera of patients with IgAN. No correlation was found between serum pIgA levels and clinical parameters of IgAN, such as decline of glomerular filtration rate, haematuria or proteinuria.

Conclusions. Although absolute levels of serum pIgA are increased in patients with IgAN as compared with controls, levels of pIgA relative to total serum IgA are lower. No significant correlation was found between serum concentrations of pIgA and clinical parameters of disease. These data support the notion that it is not the size alone, but the physicochemical composition of the macromolecular IgA that is the key factor leading to mesangial deposition.

Keywords: CD89; IgA nephropathy; immunoglobulin A; macromolecular IgA; polymeric IgA

Journal Article.  4011 words.  Illustrated.

Subjects: Nephrology

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