title: T-cell autoreactivity to citrullinated autoantigenic peptides in rheumatoid arthritis patients carrying HLA-DRB1 shared epitope alleles.
abstract: BACKGROUND
  Anti-citrullinated peptide antibodies are found in rheumatoid arthritis (RA) patients with HLA-DRβ chains encoding the shared epitope (SE) sequence. Citrullination increases self-antigen immunogenicity, through increased binding affinity to SE-containing HLA-DR molecules. To characterise T-cell autoreactivity towards citrullinated self-epitopes, we profiled responses of SE+ healthy controls and RA patients to citrullinated and unmodified epitopes of four autoantigens.
  
  
  METHODS
  We compared T-cell proliferative and cytokine responses to citrullinated and native type II collagen 1,237 to 1,249, vimentin 66 to 78, aggrecan 84 to 103 and fibrinogen 79 to 91 in six SE+ healthy controls and in 21 RA patients with varying disease duration. Cytokine-producing cells were stained after incubation with peptide in the presence of Brefeldin-A.
  
  
  RESULTS
  Although proliferative responses were low, IL-6, IL-17 and TNF were secreted by CD4+ T cells of SE+ RA patients and healthy controls, as well as IFNγ and IL-10 secreted by RA patients, in response to citrullinated peptides. Of the epitopes tested, citrullinated aggrecan was most immunogenic. Patients with early RA were more likely to produce IL-6 in response to no epitope or to citrullinated aggrecan, while patients with longstanding RA were more likely to produce IL-6 to more than one epitope. Cytokine-producing CD4+ T cells included the CD45RO+ and CD45RO- and the CD28+ and CD28- subsets in RA patients.
  
  
  CONCLUSIONS
  Proinflammatory cytokines were produced by CD4+ T cells in SE+ individuals in response to citrullinated self-epitopes, of which citrullinated aggrecan was most immunogenic. Our data suggest that the T-cell response to citrullinated self-epitopes matures and diversifies with development of RA.
authors.affiliation: The University of Queensland Diamantina Institute, Princess Alexandra Hospital, Brisbane, Qld 4102, Australia.
authors.forename: Soi Cheng
authors.initials: SC
authors.lastname: Law
authors.forename: Shayna
authors.initials: S
authors.lastname: Street
authors.forename: Chien-Hsiung Alan
authors.initials: CH
authors.lastname: Yu
authors.forename: Christelle
authors.initials: C
authors.lastname: Capini
authors.forename: Sakoontalla
authors.initials: S
authors.lastname: Ramnoruth
authors.forename: Hendrik J
authors.initials: HJ
authors.lastname: Nel
authors.forename: Eline
authors.initials: E
authors.lastname: van Gorp
authors.forename: Claire
authors.initials: C
authors.lastname: Hyde
authors.forename: Kim
authors.initials: K
authors.lastname: Lau
authors.forename: Helen
authors.initials: H
authors.lastname: Pahau
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Purcell
authors.forename: Ranjeny
authors.initials: R
authors.lastname: Thomas
mesh_terms: D000483:Alleles; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D015551:Autoimmunity / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002956:Citrulline; D016207:Cytokines / Q000096:biosynthesis; D000939:Epitopes; D005434:Flow Cytometry; D059811:HLA-DRB1 Chains / Q000235:genetics* / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D010455:Peptides / Q000276:immunology
chemical_list: D001324:Autoantigens; D016207:Cytokines; D000939:Epitopes; D059811:HLA-DRB1 Chains; D010455:Peptides; D002956:Citrulline