Renal cortical complement C3 gene expression in IgA nephropathy

J Am Soc Nephrol. 1997 Mar;8(3):415-25. doi: 10.1681/ASN.V83415.


Glomerular C3 deposits are commonly found in immunoglobulin A (IgA) nephropathy. Renal gene expression and protein synthesis of complement components have been shown in settings of tissue inflammation. In this study, the pathogenetic involvement of locally produced C3 in IgA nephropathy was analyzed. C3 gene expression was analyzed by reverse transcription, polymerase chain reaction, and in situ hybridization techniques. C3 mRNA was detected in 56% of cases, with a significantly higher percentage in patients with moderate-to-severe lesions than in those with mild lesions (P < 0.01). By in situ hybridization, C3 transcript was predominantly expressed by tubular cells and some interstitial cells. C3 mRNA was also observed on glomerular parietal epithelial cells. Immunoreactive native C3 was detected on cortical tubuli by an anti-C3c immunoalkaline-phosphatase technique. A significant correlation was found between renal C3 transcription and glomerulosclerosis, intracapillary proliferation (both P < 0.005) and markers of interstitial damage, including tubular atrophy (P < 0.05), interstitial infiltration (P < 0.05), and fibrosis (P < 0.005). Proteinuria (P < 0.05), but not serum creatinine, at the time of renal biopsy correlated with C3 mRNA. In conclusion, it was demonstrated that the C3 gene was expressed primarily in proximal tubular cells and occasionally in glomerular crescents, and that its expression correlated with clinical and histologic markers of severity and poor outcome of IgA nephropathy. Thus, a pathogenetic involvement of the local transcription and translation of the C3 gene in IgA nephropathy was suggested.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Complement C3 / genetics*
  • Disease Progression
  • Female
  • Fluorescent Antibody Technique
  • Gene Expression*
  • Glomerulonephritis, IGA / genetics*
  • Glomerulonephritis, IGA / metabolism
  • Glomerulonephritis, IGA / pathology
  • Humans
  • Immunoglobulins / metabolism
  • Immunohistochemistry
  • In Situ Hybridization
  • Kidney / pathology
  • Kidney Cortex / physiopathology*
  • Kidney Glomerulus / metabolism
  • Male
  • Middle Aged
  • Polymerase Chain Reaction
  • RNA, Messenger / metabolism


  • Complement C3
  • Immunoglobulins
  • RNA, Messenger