Plasma complement factor H is associated with disease activity of patients with ANCA-associated vasculitis

Introduction: Increasing evidences have demonstrated that activation of alternative complement pathway plays an important role in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The current study aimed to investigate the association of complement factor H (CFH), a key regulator of the alternative complement pathway, with the disease activity of AAV. Methods: Plasma CFH levels were measured in 82 patients with myeloperoxidase (MPO)-AAV in active stage. Of the 82 patients, plasma CFH levels of 27 patients were longitudinally measured. Serum anti-CFH autoantibodies were screened in AAV patients. Circulating complement activation profiles including C4d, Bb, C3a, C5a and soluble C5b-9 of AAV patients in active stage were further detected. Associations between plasma CFH levels and clinicopathological parameters as well as the prognosis were analyzed. Results: Plasma CFH levels were significantly lower in active AAV patients compared with AAV patients in remission and normal controls. Correlation analysis showed that plasma CFH levels inversely correlated with initial serum creatinine, Birmingham Vasculitis Activity Score (BVAS), proportion of total crescents and cellular crescents in renal specimens, and circulating levels of C3a, C5a and Sc5b-9, meanwhile positively correlated with estimated glomerular filtration rate (eGFR), hemoglobin levels and circulating levels of C3. Moreover, multivariate survival analysis revealed that plasma CFH levels were independently associated with composite outcome of death or end stage renal disease (ESRD) in AAV patients, after adjusting for age, gender, hemoglobin level and urinary protein (P = 0.03, HR 0.85, 95 % CI 0.73-0.98) or adjusting for age, gender, total crescents (%) and urinary protein (P = 0.03, HR 0.85, 95 % CI 0.73-0.98), while not as an independent predictor after adjusting for age, gender, serum creatinine and urinary protein (P = 0.57, HR 0.96, 95 % CI 0.83-1.11). Conclusion: In conclusion, plasma CFH levels are associated with disease activity, and, to some extent, associated with composite outcomes of patients with MPO-ANCA-associated vasculitis.