Elevated urinary excretion of the C5b-9 complex in membranous nephropathy

Area of Science:

• Nephrology
• Immunology
• Complement System Biology

Background:

• Antibody binding to glomerular antigens in experimental membranous nephropathy activates the complement system, forming C5b-9 complexes.
• These C5b-9 complexes are shed into urine during active disease, suggesting a potential biomarker.

Purpose of the Study:

• To investigate if urinary C5b-9 excretion is elevated in human membranous nephropathy.
• To correlate urinary C5b-9 levels with disease activity and clinical parameters in proteinuric patients.

Main Methods:

• Measured urinary C5b-9 and C5 excretion in 146 proteinuric patients with biopsy-proven glomerular diseases.
• Compared urinary C5b-9/C5 ratios across different glomerulonephritis types using covariance analysis.

Main Results:

• Urinary C5b-9 excretion was significantly higher in membranous nephropathy patients compared to those with non-membranous glomerulonephritis (P < 0.0002).
• Elevated urinary C5b-9 was observed across various glomerulonephritis types, including lupus nephritis.
• In membranous nephropathy, higher urinary C5b-9 correlated with shorter disease duration, lower serum creatinine, and higher proteinuria.

Conclusions:

• Urinary C5b-9 excretion serves as a potential indicator of complement activation in human membranous nephropathy.
• Elevated urinary C5b-9 may reflect active disease and correlate with specific clinical and pathological features.