title: Development of the anti-citrullinated protein antibody repertoire prior to the onset of rheumatoid arthritis.
abstract: OBJECTIVE
  To examine how anti-citrullinated protein antibody (ACPA) epitope spreading takes place prior to the onset of clinical rheumatoid arthritis (RA), and to analyze the pattern of autoantigen reactivity at the beginning of the immune response.
  
  
  METHODS
  Multiple consecutive serum samples from 79 RA patients who had donated blood before disease onset were available for analysis. Fifty-three patients tested positive for ACPAs prior to the onset of clinical RA. For these patients, a median of 6 (interquartile range 4-9) sequential pre-RA serum samples obtained 1-2 years apart were tested. Reactivity to 5 distinct citrullinated peptides was measured by enzyme-linked immunosorbent assay. Two peptides were derived from fibrinogen, 1 from vimentin, 1 from α-enolase, and 1 from filaggrin.
  
  
  RESULTS
  In 25 of 53 ACPA-positive patients, seroconversion from ACPA absence to ACPA presence was observed. In 72% of these patients, the immune response started with reactivity to 1 peptide, without preference for a particular peptide. The number of peptides recognized increased over time, without a dominant epitope-spreading pattern. ACPAs appeared in low levels several years prior to the diagnosis of RA. Antibody titers increased markedly ∼2-4 years before diagnosis.
  
  
  CONCLUSIONS
  Our findings indicate that ACPA epitope spreading occurs over several years prior to the onset of clinical RA. The initial autoimmune response is mostly directed toward only 1 autoantigen, but this is not always the same antigen. The marked increase in ACPA titers a few years prior to the diagnosis of RA suggests a second stage in disease development, which might be due to a variety of factors.
authors.affiliation: Jan van Breemen Research Institute/Reade, Sanquin Research, and Landsteiner Laboratorium, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. l.vandestadt@sanquin.nl
authors.forename: Lotte A
authors.initials: LA
authors.lastname: van de Stadt
authors.forename: Margret H M T
authors.initials: MH
authors.lastname: de Koning
authors.forename: Rob J
authors.initials: RJ
authors.lastname: van de Stadt
authors.forename: Gertjan
authors.initials: G
authors.lastname: Wolbink
authors.forename: Ben A C
authors.initials: BA
authors.lastname: Dijkmans
authors.forename: Dörte
authors.initials: D
authors.lastname: Hamann
authors.forename: Dirkjan
authors.initials: D
authors.lastname: van Schaardenburg
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D005260:Female; D000091344:Filaggrin Proteins; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D010456:Peptides, Cyclic