title: Epitope analysis of autoantibodies to ADAMTS13 in patients with acquired thrombotic thrombocytopenic purpura.
abstract: BACKGROUND
  Autoantibodies to ADAMTS13 have a pivotal role in the pathogenesis of acquired thrombotic thrombocytopenic purpura (TTP). By decreasing the function of ADAMTS13, autoantibodies impair the cleavage of ultra-large von Willebrand factor (UL-VWF) multimers into smaller sizes, leading to lethal platelet-VWF thrombi in the microcirculation. We therefore aimed to determine the sites of autoantibody recognition on ADAMTS13.
  
  
  METHODS
  In this study, IgG purified from 13 acquired TTP patients were examined to determine their binding sites on ADAMTS13. Immobilized IgG on microtiter plate or proteinG beads was screened by phage library expressing various peptides of ADAMTS13.
  
  
  RESULTS
  In screening, diverse peptide sequences were obtained from almost all of the ADAMTS13 domains, including the spacer domain, which is considered a major binding site. In particular, we detected an identical amino-acid sequence in the C-terminus of the spacer domain from Gly662 to Val687 that was recognized by autoantibodies from 5 TTP patients. The specific autoantibody was expected to be associated with the plasma levels of the ADAMTS13 antigen or activity, and with the quantity of ADAMTS13 autoantibodies or the inhibitory autoantibody titer in TTP patient plasma. These measurements, however, did not seem to be related to the presence or absence of the specific autoantibody.
  
  
  CONCLUSIONS
  These findings indicate that the specific autoantibody might be a feature of acquired TTP, although its clinical significance remains to be elucidated.
authors.affiliation: Department of Laboratory Medicine, Keio University School of Medicine, Tokyo, Japan. yusukeyamaguchi@z8.keio.jp
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Takanori
authors.initials: T
authors.lastname: Moriki
authors.forename: Atsuko
authors.initials: A
authors.lastname: Igari
authors.forename: Terumichi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Wada
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fujimura
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Murata
mesh_terms: D051722:ADAM Proteins / Q000097:blood / Q000276:immunology*; D000071120:ADAMTS13 Protein; D000293:Adolescent; D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001666:Binding Sites, Antibody; D018604:Epitope Mapping / Q000379:methods; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood / Q000276:immunology* / Q000473:pathology; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human