title: Follow-up of avidity and titre of anti-myeloperoxidase antibodies in sera from patients with propylthiouracil-induced vasculitis.
abstract: OBJECTIVE
  Propylthiouracil (PTU) has been known to induce myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) positive vasculitis. Our previous study indicated that the increase of avidity of MPO-ANCA might be associated with the occurrence of clinical vasculitis in patients with PTU-induced ANCA. The current study aimed to follow-up the avidity and titre of anti-MPO antibodies in sequential sera from patients with PTU-induced ANCA-associated systemic vasculitis (AASV).
  
  
  METHODS
  Six patients with PTU-induced vasculitis were enrolled in the current study. Serial sera in both active phase and in remission were collected. MPO-ANCA avidity was assessed by antigen-inhibition enzyme-linked immunosorbent assays (ELISAs), and avidity constant (aK) was determined as the reciprocal value of the MPO molar concentration in the liquid phase resulting in 50% inhibition of anti-MPO antibody binding to MPO in solid phase ELISA. Titres of MPO-ANCA were determined by using serial serum dilutions in MPO-ELISA.
  
  
  RESULTS
  After cessation of PTU and initiation of immunosuppressive therapy, the avidity and titre of MPO-ANCA decreased significantly during follow-up in sera from all the patients, and the avidity decreased much more quickly than the titres.
  
  
  CONCLUSIONS
  Our study indicates that avidity of anti-MPO antibodies might be more closely associated with clinical vasculitis than titre.
authors: Department of Nephrology, Peking University first Hospital, Beijing, China.
authors: Ying
authors: Y
authors: Gao
authors: Min
authors: M
authors: Chen
authors: Hua
authors: H
authors: Ye
authors: Xiao-Hui
authors: XH
authors: Guo
authors: Ming-Hui
authors: MH
authors: Zhao
authors: Hai-Yan
authors: HY
authors: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D013956:Antithyroid Agents / Q000009:adverse effects* / Q000627:therapeutic use; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D005921:Glomerulonephritis / Q000150:complications / Q000188:drug therapy / Q000276:immunology; D006111:Graves Disease / Q000150:complications / Q000188:drug therapy / Q000276:immunology; D006801:Humans; D009195:Peroxidase / Q000276:immunology*; D011441:Propylthiouracil / Q000009:adverse effects* / Q000627:therapeutic use; D014657:Vasculitis / Q000139:chemically induced* / Q000276:immunology; D028761:Withholding Treatment
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D013956:Antithyroid Agents; D011441:Propylthiouracil; D009195:Peroxidase