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Urinary C3dg and C5b-9 indicate active immune disease in human membranous nephropathy
P E Brenchley1, B Coupes, C D Short
1Department of Renal Medicine, Manchester Royal Infirmary, England, United Kingdom.
Insights
High urinary C5b-9 levels indicate active immune components in membranous nephropathy, predicting a worse clinical course. Plasma C3dg is elevated in IgA nephropathy, while urinary markers are higher in membranous nephropathy.
Area of Science:
- Nephrology
- Immunology
- Clinical Chemistry
Background:
- Idiopathic membranous nephropathy (IMN) and IgA nephropathy (IgAN) are common causes of glomerular damage.
- Complement system activation is implicated in the pathogenesis of various kidney diseases.
- Specific complement activation markers may help differentiate disease activity and prognosis.
Purpose of the Study:
- To measure complement activation markers (C3dg, C5b-9) in plasma and urine of patients with IMN and IgAN.
- To assess the association of these markers with specific nephropathies and clinical outcomes.
- To determine the utility of urinary C5b-9 in predicting the clinical course of IMN.
Main Methods:
- Plasma and urine samples were collected from patients diagnosed with IMN and IgAN.
- Levels of C3dg and C5b-9 were quantified using immunoassays.
- Statistical analyses were performed to compare marker levels between groups and correlate with clinical data.
Main Results:
- Plasma C5b-9 levels did not differ significantly between IMN and IgAN patients.
- Elevated plasma C3dg was significantly associated with IgAN (45% > 25 U/ml).
- High urinary C3dg and C5b-9 were significantly associated with IMN (43% each) compared to IgAN (10% and 0%).
- In IMN patients, high initial urinary C5b-9 predicted an unstable clinical course (66%) versus low/absent levels (18%).
Conclusions:
- Urinary C3dg and C5b-9 are elevated in membranous nephropathy, suggesting complement system involvement.
- High urinary C5b-9 levels in IMN patients may identify active immunological components driving progressive glomerular damage.
- These markers could aid in predicting disease activity and prognosis in nephropathy patients.
Abstract:
We have measured complement activation markers, C3dg and C5b-9 in plasma and urine from patients with idiopathic membranous nephropathy and IgA nephropathy. There was no significant difference in levels of plasma C5b-9 between the patient groups. However, high plasma concentrations of C3dg were associated significantly with IgA nephropathy with 45% of patients having levels over 25 U/ml (P less than 0.001). High concentrations of urinary C3dg and C5b-9 were associated significantly with membranous nephropathy (43% and 43% of the patient group, respectively) compared to patients with IgA nephropathy (10% and 0%, respectively, P less than 0.001). In a retrospective analysis of 31 patients with membranous nephropathy, 66% of patients with high initial urinary C5b-9 showed an unstable clinical course compared to 18% of patients with initially absent or low C5b-9 (P less than 0.001). We suggest that high urinary C5b-9 identifies those patients with a membranous lesion which retains an active immunological component contributing to the pathology of progressive glomerular damage.