title: Human anti-neutrophil cytoplasm autoantibodies to proteinase 3 (PR3-ANCA) bind to neutrophils.
abstract: BACKGROUND
  Recently, the in vivo pathogenic role of anti-neutrophil cytoplasm autoantibodies (ANCA) in ANCA-associated vasculitis has been challenged by Abdel-Salam et al. In their report, they observed that ANCA directed against proteinase 3 (PR3) cannot bind to their target autoantigen PR3 on circulating neutrophils (PMN). Here we present evidence that human PR3-ANCA do specifically bind to PMN that express PR3 on their membrane.
  
  
  METHODS
  PMN were isolated from donors showing bimodal membrane PR3 expression on their PMN (N= 3). TNFalpha-primed PMN or PMA-stimulated PMN were incubated with serum or plasma from PR3-ANCA-positive patients with Wegener's granulomatosis (WG) (N= 8) or healthy controls (N= 8). Binding of IgG in serum or plasma samples to PMN was assessed by indirect immunofluorescence.
  
  
  RESULTS
  Binding of IgG in undiluted plasma or serum from PR3-ANCA-positive WG-patients to PMN was significantly increased compared to plasma or serum from healthy controls. Dilution of plasma and serum showed concentration-dependent binding of IgG. Double staining for PR3 and IgG demonstrated that IgG in plasma or serum from PR3-ANCA-positive patients only bound to those PMN that expressed PR3, and not to PMN that lacked PR3 expression on their membrane.
  
  
  CONCLUSIONS
  PR3-ANCA in undiluted serum or plasma from PR3-ANCA-positive WG patients bind to TNFalpha- primed and PMA-stimulated PMN that express PR3 on their membrane. Therefore, the hypothesis that PR3-ANCA can bind and activate primed PMN is still the most attractive explanation for the contribution of PR3-ANCA to the pathogenesis of Wegener's granulomatosis.
authors: Department of Rheumatology and Clinical Immunology, Groningen University Medical Centre, Groningen, The Netherlands.
authors: André P
authors: AP
authors: Van Rossum
authors: Ymke M
authors: YM
authors: van der Geld
authors: Pieter C
authors: PC
authors: Limburg
authors: Cees G M
authors: CG
authors: Kallenberg
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood / Q000276:immunology*; D000918:Antibody Specificity; D014890:Granulomatosis with Polyangiitis / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D053146:Myeloblastin; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D012697:Serine Endopeptidases / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D007074:Immunoglobulin G; D014409:Tumor Necrosis Factor-alpha; D012697:Serine Endopeptidases; D053146:Myeloblastin