title: A pro-inflammatory role of C5L2 in C5a-primed neutrophils for ANCA-induced activation.
abstract: BACKGROUND
  The complement system is crucial for the development of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In particular, C5a and its receptor on neutrophils, CD88, play a central role. The functional role of the second receptor of C5a, C5L2, remains unclear. In the current study, we investigated the role of C5L2 in C5a-primed neutrophils for ANCA-induced activation.
  
  
  METHODS
  The effect of blocking C5L2 by anti-human C5L2 blocking antibody were tested on respiratory burst and degranulation of C5a-primed neutrophils activated with ANCA, as well as on membrane-bound proteinase 3 (mPR3) and concentration of myeloperoxidase (MPO) in supernatant of C5a-primed neutrophils. An antagonist for CD88 was also employed.
  
  
  RESULTS
  Blocking C5L2 resulted in a significantly decreased MPO concentration in the supernatant of C5a-primed neutrophils. mPR3 expression increased from 209.0±43.0 in untreated cells to 444.3±60.8 after C5a treatment (P<0.001), and decreased to 375.8±65.44, 342.2±54.3 and 313.7±43.6 by pre-incubating blocking C5L2 antibody at 2.5 µg/ml, 5 µg/ml or 10 µg/ml (compared with C5a-priming group, P<0.001, P<0.001, and P<0.001), respectively. In C5a-primed neutrophils, subsequently activating with MPO-ANCA-positive IgG, the MFI value was 425.8±160.6, which decreased to 292.8±141.2, 289.7±130.0 and 280.3±136.4 upon pre-incubation with mouse anti-human C5L2 blocking antibody at 2.5 µg/ml, 5 µg/ml or 10 µg/ml (compared with C5a-primed neutrophils, for MPO-ANCA-positive IgG-induced activation, P<0.05, P<0.05, and P<0.05), respectively. Blocking C5L2 also resulted in significantly decreased C5a-primed neutrophils for PR3-ANCA-positive IgG-induced activation. Moreover, the lactoferrin concentration in the supernant significantly decreased in pre-incubation with anti-human C5L2 blocking antibody, compared with C5a-primed neutrophils induced by PR3- or MPO-ANCA-positive IgG.
  
  
  CONCLUSIONS
  C5L2 may be implicated in the pro-inflammatory role in C5a-primed neutrophils for ANCA-induced activation.
authors.affiliation: Renal Division, Department of Medicine, Peking University, First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Hao
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Yuan
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology* / Q000378:metabolism; D019138:Antibodies, Blocking / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology; D002462:Cell Membrane / Q000378:metabolism; D015936:Complement C5a / Q000276:immunology*; D017077:Culture Media, Conditioned / Q000378:metabolism; D006801:Humans; D018375:Neutrophil Activation / Q000187:drug effects / Q000276:immunology*; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D021381:Protein Transport; D044087:Receptor, Anaphylatoxin C5a / Q000037:antagonists & inhibitors / Q000378:metabolism; D019707:Receptors, Chemokine / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D016897:Respiratory Burst / Q000187:drug effects / Q000276:immunology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; C417003:C5aR2 protein, human; D017077:Culture Media, Conditioned; D044087:Receptor, Anaphylatoxin C5a; D019707:Receptors, Chemokine; D015936:Complement C5a; D009195:Peroxidase; D010447:Peptide Hydrolases