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[Circulating immune complexes and complement breakdown products in childhood IgA nephropathy]
C Tanaka1, Y Suhara, Y Kikkawa
1Department of Pediatrics, Nihon University School of Medicine, Tokyo, Japan.
Insights
In IgA nephropathy, elevated IgA-circulating immune complexes (CIC) correlate with complement C3 activation. These findings link CIC levels to disease activity and potential kidney damage in children.
Area of Science:
- Immunology
- Nephrology
Context:
- IgA nephropathy (IgAN) is a common glomerular disease.
- Elevated circulating immune complexes (CIC), particularly IgA-CIC, are observed in IgAN.
- The relationship between CIC and complement system activation in IgAN remains unclear.
Purpose:
- To investigate the association between CIC and complement activation in pediatric IgA nephropathy.
- To determine if CIC levels correlate with clinical and histological findings in IgAN patients.
Summary:
- IgA-CIC were detected in 78% of children with IgA nephropathy, at significantly higher levels than in other glomerular diseases.
- IgA-CIC levels correlated positively with proteinuria and with markers of complement C3 activation (C3d/C3 ratio).
- No strong correlation was found between CIC levels and histological severity, likely due to the intermittent nature of CIC.
Impact:
- This study highlights the role of IgA-CIC and complement activation in IgA nephropathy pathogenesis.
- Findings suggest that IgA-CIC may serve as a biomarker for disease activity in pediatric IgAN.
- Further research could explore therapeutic strategies targeting CIC or complement activation in IgAN.
Abstract:
Circulating immune complexes (CIC), mainly IgA-CIC have been frequently detected in IgA nephropathy and recently increased levels of C3 fragments which indicate C3 activation have been reported. However, little is known about the relationship between CIC and complement activation. We determined CIC by the solid-phase anti-C3 Facb enzyme immunoassay in 37 children with IgA nephropathy to investigate the relationship between CIC and clinical and/or histological findings, and also determined C3 fragments whether CIC correlate with complement activation. IgA-CIC were detected in 78% (27/37) with a mean level of 11.9 +/- 3.9 micrograms/ml, which was significantly higher than other glomerular diseases (P less than 0.05). IgA-CIC levels were also found significantly higher in 27 cases with proteinuria than in 10 cases without proteinuria (P less than 0.05). IgG-CIC were detected in 67% (12/18) with a mean level of 4.1 +/- 2.6 micrograms/ml, which was not significantly different from other glomerular diseases. No striking correlation was noted to exist between CIC levels at renal biopsy and the histological severity, because CIC are often present intermittently. C3d was quantitated by the rocket immunoelectrophoresis and C3 by the single radial immunodiffusion to determine the C3d/C3 ratio. The mean value of C3d/C3 was 0.63 +/- 0.19 which was significantly higher than a corresponding value for 15 healthy controls of 0.27 +/- 0.06 (P less than 0.05). Levels of IgA-CIC were found to have a significant positive correlation between C3d/C3 determined simultaneously in 33 cases (r = 0.43, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)