title: Residues Arg568 and Phe592 contribute to an antigenic surface for anti-ADAMTS13 antibodies in the spacer domain.
abstract: BACKGROUND
  The majority of patients diagnosed with thrombotic thrombocytopenic purpura have autoantibodies directed towards the spacer domain of ADAMTS13.
  
  
  METHODS
  In this study we explored the epitope specificity and immunoglobulin class and immunoglobulin G subclass distribution of anti-ADAMTS13 antibodies. The epitope specificity of anti-spacer domain antibodies was examined using plasma from 48 patients with acute acquired thrombotic thrombocytopenic purpura by means of immunoprecipitation of ADAMTS13 variants containing single or multiple alanine substitutions. Using similar methods, we also determined the presence of anti-TSP2-8 and CUB1-2 domain antibodies in this cohort of patients.
  
  
  RESULTS
  Antibody profiling revealed that anti-ADAMTS13 immunoglobulin G1 and immunoglobulin G4 predominate in plasma of patients with acquired thrombotic thrombocytopenic purpura. Analysis of anti-spacer domain antibodies revealed that Arg568 and Phe592, in addition to residues Arg660, Tyr661, and Tyr665, also contribute to an antigenic surface in the spacer domain. The majority of patients (90%) lost reactivity towards the spacer domain following introduction of multiple alanine substitutions at Arg568, Phe592, Arg660, Tyr661 and Tyr665. Anti-TSP2-8 and anti-CUB1-2 domain-directed antibodies were present in, respectively, 17% and 35% of the patients' samples analyzed.
  
  
  CONCLUSIONS
  Immunoglobulin G directed towards a single antigenic surface comprising residues Arg568, Phe592, Arg660, Tyr661 and Tyr665 predominates in the plasma of patients with acquired thrombotic thrombocytopenic purpura.
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Pos
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Sorvillo
authors.forename: Rob
authors.initials: R
authors.lastname: Fijnheer
authors.forename: Hendrik B
authors.initials: HB
authors.lastname: Feys
authors.forename: Paul H P
authors.initials: PH
authors.lastname: Kaijen
authors.forename: Gestur
authors.initials: G
authors.lastname: Vidarsson
authors.forename: Jan
authors.initials: J
authors.lastname: Voorberg
mesh_terms: D051722:ADAM Proteins / Q000097:blood / Q000276:immunology*; D000071120:ADAMTS13 Protein; D000918:Antibody Specificity / Q000276:immunology; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D015331:Cohort Studies; D000939:Epitopes / Q000097:blood / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D008297:Male; D017434:Protein Structure, Tertiary; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000175:diagnosis / Q000201:enzymology* / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human