title: Identification of anticitrullinated protein antibody reactivities in a subset of anti-CCP-negative rheumatoid arthritis: association with cigarette smoking and HLA-DRB1 'shared epitope' alleles.
abstract: BACKGROUND
  A hallmark of rheumatoid arthritis (RA) is the development of autoantibodies targeting proteins that contain citrulline. Anticitrullinated protein antibodies (ACPAs) are currently detected by the commercial cyclic citrullinated peptide (CCP) assay, which uses a mix of cyclised citrullinated peptides as an artificial mimic of the true antigen(s). To increase the sensitivity of ACPA detection and dissect ACPA specificities, we developed a multiplex assay that profiles ACPAs by measuring their reactivity to the citrullinated peptides and proteins derived from RA joint tissue.
  
  
  METHODS
  We created a bead-based, citrullinated antigen array to profile ACPAs. This custom array contains 16 citrullinated peptides and proteins detected in RA synovial tissues. We used the array to profile ACPAs in sera from a cohort of patients with RA and other non-inflammatory arthritides, as well as sera from an independent cohort of RA patients for whom data were available on carriage of HLA-DRB1 'shared epitope' (SE) alleles and history of cigarette smoking.
  
  
  RESULTS
  Our multiplex assay showed that at least 10% of RA patients who tested negative in the commercial CCP assay possessed ACPAs. Carriage of HLA-DRB1 SE alleles and a history of cigarette smoking were associated with an increase in ACPA reactivity-in anti-CCP(+) RA and in a subset of anti-CCP(-) RA.
  
  
  CONCLUSIONS
  Our multiplex assay can identify ACPA-positive RA patients missed by the commercial CCP assay, thus enabling greater diagnostic sensitivity. Further, our findings suggest that cigarette smoking and possession of HLA-DRB1 SE alleles contribute to the development of ACPAs in anti-CCP(-) RA.
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Catriona A
authors.initials: CA
authors.lastname: Wagner
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sokolove
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Lahey
authors.affiliation: Institute for Environmental Medicine, Karolinska Institutet, Stockhoom, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Bengtsson
authors.affiliation: Rheumatology Unit, Department of Medicine and Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Saedis
authors.initials: S
authors.lastname: Saevarsdottir
authors.affiliation: Rheumatology Unit, Department of Medicine and Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.affiliation: Bio-Rad Laboratories, Hercules, California, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Delanoy
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Tamsin M
authors.initials: TM
authors.lastname: Lindstrom
authors.affiliation: Bio-Rad Laboratories, Hercules, California, USA.
authors.forename: Roger P
authors.initials: RP
authors.lastname: Walker
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Reuven
authors.initials: R
authors.lastname: Bromberg
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: Piyanka E
authors.initials: PE
authors.lastname: Chandra
authors.affiliation: Bio-Rad Laboratories, Hercules, California, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Binder
authors.affiliation: Rheumatology Unit, Department of Medicine and Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Klareskog
authors.affiliation: Geriatric Research Education and Clinical Center (GRECC), Palo Alto, California, USA Division of Immunology and Rheumatology, Stanford University, Stanford, California, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D015535:Arthritis, Psoriatic / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D016022:Case-Control Studies; D002956:Citrulline / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000235:genetics; D005260:Female; D006073:Gout / Q000276:immunology; D059811:HLA-DRB1 Chains / Q000235:genetics*; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000276:immunology*; D010456:Peptides, Cyclic / Q000276:immunology*; D012907:Smoking / Q000276:immunology*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D059811:HLA-DRB1 Chains; D010455:Peptides; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D002956:Citrulline
keywords: Autoantibodies; Rheumatoid Arthritis; Smoking