title: Local Joint inflammation and histone citrullination in a murine model of the transition from preclinical autoimmunity to inflammatory arthritis.
abstract: OBJECTIVE
  Anti-citrullinated protein antibodies (ACPAs) are characteristic of rheumatoid arthritis (RA). However, their presence years before the onset of clinical RA is perplexing. Although multiple putative citrullinated antigens have been identified, no studies have demonstrated the specific capacity of these antigens to initiate inflammatory arthritis. This study was undertaken to recapitulate the transition from preclinical to clinical RA and to demonstrate the capacity of local citrullination to facilitate this transition.
  
  
  METHODS
  We performed proteomic analysis of activated human neutrophils to identify citrullinated proteins, including those targeted as part of the RA immune response. Using enzyme-linked immunosorbent assay, we compared RA and osteoarthritis synovial fluid for levels of citrullinated histone H2B and its immune complex. Using macrophage activation assays, we assessed the effect of histone citrullination on immunostimulatory capacity and evaluated the stimulatory capacity of native and citrullinated H2B immune complexes. Finally, we assessed the potential for anti-citrullinated H2B antibodies to mediate arthritis in vivo.
  
  
  RESULTS
  We identified robust targeting of neutrophil-derived citrullinated histones by the ACPA immune response. More than 90% of the RA patients had anti-citrullinated H2B antibodies. Histone citrullination increased innate immunostimulatory capacity, and immune complexes containing citrullinated histones activated macrophage cytokine production and propagated neutrophil activation. Finally, we demonstrated that immunization with H2B was arthritogenic, but only in the setting of underlying articular inflammation.
  
  
  CONCLUSIONS
  Our findings indicate that citrullinated histones, specifically citrullinated H2B, are an antigenic target of the ACPA immune response. Furthermore, local generation of citrullinated antigen during low-grade articular inflammation provides a mechanistic model for the conversion from preclinical autoimmunity to inflammatory arthritis.
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Dong Hyun
authors.initials: DH
authors.lastname: Sohn
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Christopher
authors.initials: C
authors.lastname: Rhodes
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Onuma
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhao
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Orr
authors.initials: O
authors.lastname: Sharpe
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Tal
authors.initials: T
authors.lastname: Gazitt
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Rani
authors.initials: R
authors.lastname: Shiao
authors.affiliation: Cedars Sinai Medical Center, Los Angeles, California).
authors.forename: Justyna
authors.initials: J
authors.lastname: Fert-Bober
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Danye
authors.initials: D
authors.lastname: Cheng
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Lahey
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Heidi H
authors.initials: HH
authors.lastname: Wong
authors.affiliation: Cedars Sinai Medical Center, Los Angeles, California).
authors.forename: Jennifer
authors.initials: J
authors.lastname: Van Eyk
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
authors.affiliation: VA Palo Alto Healthcare System, Palo Alto, California, and Stanford University School of Medicine, Stanford, California.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sokolove
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology*; D001323:Autoantibodies; D015551:Autoimmunity / Q000502:physiology*; D002956:Citrulline / Q000378:metabolism; D004195:Disease Models, Animal; D018450:Disease Progression; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology*; D007596:Joints / Q000378:metabolism / Q000473:pathology*; D040901:Proteomics
chemical_list: D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D006657:Histones; D002956:Citrulline