title: Anti-C1q autoantibodies from active lupus nephritis patients could inhibit the clearance of apoptotic cells and complement classical pathway activation mediated by C1q in vitro.
abstract: Anti-C1q antibodies are prevalent in patients with active lupus nephritis and were found to be closely associated with renal involvement and predictive for a flare of nephritis. However, the pathogenesis of anti-C1q antibodies involved in human lupus nephritis remains unclear. C1q, which plays a key role in apoptotic cell and immune complex removal, is a very important functional molecule in the pathogenesis of SLE. The aim of this study was to investigate the influence of anti-C1q autoantibodies from active lupus nephritis patients on the bio-functions of C1q in vitro. We purified IgG autoantibodies against C1q from lupus nephritis patients, and found that they could recognize C1q bound on early apoptotic cells at 30 μg/ml, and could significantly decrease the phagocytosis by macrophages of early apoptotic cells opsonized by 50 μg/ml C1q in comparison with normal IgG. Levels of circulating immune complexes of the ten patients were measured by a circulating immune complexes (CIC)-C1q Enzyme Immunoassay Kit. Anti-C1q autoantibodies affinity purified by microtiter plates could significantly inhibit the deposition of C3c on CIC-C1q in a dose dependent manner in comparison with IgG from 10 healthy blood donors. The binding of opsonized immune complexes to RBCs was significantly inhibited by anti-C1q autoantibodies purified by microtiter plates in a dose dependent manner. Our observations suggest that serum anti-C1q autoantibodies from active lupus nephritis patients could interfere with some biological function of C1q in vitro.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing 100034, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Pang
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing 100034, PR China.
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Yang
authors.affiliation: Department of Nephrology, the First Affiliated Hospital of Chinese PLA General Hospital, 51 Fucheng Road, Beijing 100048, PR China. Electronic address: songyan0209@163.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Song
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing 100034, PR China. Electronic address: yufengevert1@sina.com.
authors.forename: Feng
authors.initials: F
authors.lastname: Yu
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing 100034, PR China; Peking-Tsinghua Center for Life Sciences, Beijing, PR China.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000936:Antigen-Antibody Complex / Q000276:immunology / Q000378:metabolism; D017209:Apoptosis / Q000276:immunology / Q000528:radiation effects; D001323:Autoantibodies / Q000097:blood / Q000276:immunology* / Q000302:isolation & purification; D002460:Cell Line; D015922:Complement C1q / Q000276:immunology*; D003171:Complement Pathway, Classical; D057899:Cytophagocytosis / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology / Q000378:metabolism; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008181:Lupus Nephritis / Q000276:immunology* / Q000378:metabolism / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010951:Plasma Exchange; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D015922:Complement C1q
keywords: Anti-C1q autoantibodies; Apoptosis; Complements; Lupus nephritis; Systemic lupus erythematosus