title: 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.
authors.affiliation: Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Beatrijs D
authors.initials: BD
authors.lastname: Oortwijn
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Rastaldi
authors.forename: Anja
authors.initials: A
authors.lastname: Roos
authors.forename: Deborah
authors.initials: D
authors.lastname: Mattinzoli
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Daha
authors.forename: Cees
authors.initials: C
authors.lastname: van Kooten
mesh_terms: D001706:Biopsy; D005920:Glomerular Mesangium / Q000473:pathology; D005922:Glomerulonephritis, IGA / Q000276:immunology* / Q000473:pathology; D007071:Immunoglobulin A, Secretory / Q000032:analysis*; D007668:Kidney / Q000276:immunology* / Q000473:pathology; D012079:Renal Circulation
chemical_list: D007071:Immunoglobulin A, Secretory