title: Anti-myeloperoxidase IgG subclass distribution and avidity in sera from patients with propylthiouracil-induced antineutrophil cytoplasmic antibodies associated vasculitis.
abstract: OBJECTIVE
  Propylthiouracil (PTU) could induce MPO-ANCA-positive vasculitis. The aim of this study was to compare the IgG subclass distribution and avidity of MPO-ANCA in sera from patients with primary ANCA-associated vasculitis (AASV) and PTU-induced vasculitis.
  
  
  METHODS
  Nineteen patients with primary AASV with MPO-ANCA and thirteen patients with PTU-induced vasculitis were enrolled in the current study. Sera in both active phase and remission were collected. Anti-MPO IgG subclasses were detected by antigen specific ELISAs using specific monoclonal antibodies as second antibodies, and MPO-ANCA avidity was assessed by antigen-inhibition ELISAs.
  
  
  RESULTS
  In primary AASV, all four anti-MPO IgG subclasses could be detected in active phase with IgG1 (100%), IgG2 (73.7%), IgG3 (63.2%) and IgG4 (94.7%), and in remission, IgG1 and IgG4 subclasses in most patients remained positive. However, in PTU-induced vasculitis, anti-MPO IgG3 subclass could not be detected, the anti-MPO IgG subclasses in active phase were IgG1 (100%), IgG2 (61.5%) and IgG4 (46.2%). Furthermore, five out of the six patients (88.8%) with PTU-induced vasculitis with positive IgG4 subclass in active phase turned to negative in remission, however, only eight out of the fourteen patients (57.1%) with primary AASV turned to negative. The median avidity constant of MPO-ANCA was 56 (8.96 to >140) x 10(7) mol/l for patients with primary AASV and 0.7 (<0.28 to >140) x 10(7) mol/l for patients with PTU-induced vasculitis respectively. Furthermore, the relative levels of MPO-ANCA avidity were associated with elevation of ESR in primary AASV and were associated with BVAS scores in patients with PTU-induced vasculitis, respectively.
  
  
  CONCLUSIONS
  MPO-ANCA IgG subclass distribution and avidity were different between patients with primary AASV and PTU-induced vasculitis. It was suggested that the mechanism of ANCA production in PTU-induced vasculitis was different from that in primary AASV, and the avidity of MPO-ANCA might be associated with disease activity.
authors: Department of Nephrology, Peking University First Hospital, Beijing, PR China.
authors: Ying
authors: Y
authors: Gao
authors: Hua
authors: H
authors: Ye
authors: Feng
authors: F
authors: Yu
authors: Xiao-Hui
authors: XH
authors: Guo
authors: Ming-Hui
authors: MH
authors: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood / Q000276:immunology*; D000915:Antibody Affinity; D015415:Biomarkers / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009195:Peroxidase / Q000276:immunology*; D011441:Propylthiouracil / Q000009:adverse effects*; D014657:Vasculitis / Q000209:etiology / Q000276:immunology*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; D007074:Immunoglobulin G; D011441:Propylthiouracil; D009195:Peroxidase