Serum complement factor I is associated with disease activity of systemic lupus erythematosus

// Min-Hua Tseng 1 , Shih-Hua Lin 2 , Chao-Yi Wu 3 , Hui-Ping Chien 4 , Huang-Yu Yang 5 , Yung-Chang Chen 5 , Yu-Ching Chou 6 and Jing-Long Huang 3 1 Division of Nephrology, Department of Pediatrics, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan 2 Division of Nephrology, Department of Medicine, Tri-Service General Hospital, Taipei, Taiwan 3 Division of Allergy, Asthma and Rheumatology, Department of Pediatrics, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan 4 Department of Pathology, Tri-Service General Hospital, Taipei, Taiwan 5 Department of Nephrology, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan 6 School of Public Health, National Defense Medical Center, Taipei, Taiwan Correspondence to: Jing-Long Huang, email: long@adm.cgmh.org Keywords: systemic lupus erythematosus; disease activity; complement regulatory proteins; lupus nephritis; biomarker Received: July 12, 2017      Accepted: October 30, 2017      Published: January 03, 2018 ABSTRACT Although aberrant complement activation is involved in the pathogenesis of systemic lupus erythematosus (SLE), the role of complement regulatory proteins in disease activity of SLE remains limited. We enrolled the pediatric-onset SLE patients from our cohort study over 10 years. The clinical and laboratory data including SLEDAI disease activity score, and serum complement factor H (CFH), CFI, CD46, C5a, and C5b-9 in the active and remission phases were determined. Glomerular C5b-9 deposition as a complement activity marker was also examined. Forty patients (35 female and 5 male, aged 13.9 ± 3.8 years) met the criteria of investigation were assessed. Fever and kidney were the most common symptom and organ involved, respectively. Mean SLEDAI in the active and remission phases were 12.6 vs 1.7, respectively. All patients exhibited lower serum C3, C4, CFH and CFI and higher serum anti-dsDNA and CD46 in the active pahse. There was a significant difference in serum CFH, CFI and CD46 between active and remissive phases. Serum CFI but not CFH and CD46 level was negatively correlated with SLEDAI score in active phase. Compared to classical activity markers, serum CFI was superior to C4 and anti-dsDNA in reflecting disease activity and also significantly correlated with white blood count and hemoglobin. Glomerular C5b-9 depositions were detected in patients with nephritis during active phase but not in disease controls. Serum CFI level may not only be a promising biomarker for disease activity of SLE, but also reflects the hematological features of SLE.