title: Systemic levels of IL-23 are strongly associated with disease activity in rheumatoid arthritis but not spondyloarthritis.
abstract: OBJECTIVE
  Th17 cells are an effector T-cell population that plays a role in chronic inflammatory conditions and is dependent on IL-23 for their survival and expansion. More recently, a genetic association was discovered between polymorphisms in the gene coding for the IL-23 receptor and spondyloarthritis. This study aimed to evaluate the role of Th17-associated cytokines in spondyloarthritis pathogenesis by measuring their levels in the joints and circulation as well as correlating them with disease activity parameters.
  
  
  METHODS
  Paired synovial fluid (SF), serum and synovial biopsies were obtained from 30 non-PsA (psoriatic arthritis) spondyloarthritis, 22 PsA and 22 rheumatoid arthritis (RA) patients. IL-17, IL-23 and CCL20 were measured by ELISA in the SF and serum of patients and correlated with systemic and local parameters of disease activity.
  
  
  RESULTS
  Concentrations of CCL20, a major Th17-attracting chemokine, tended to be higher in the joints of RA than in spondyloarthritis patients. Interestingly, levels of CCL20 were markedly higher in SF as opposed to serum. In addition, there was a remarkable association between the expression of the Th17 cytokine system and the presence of intimal lining layer hyperplasia in RA. Also in the serum, there was a tendency for higher IL-23 levels in RA, which correlated strongly with disease activity parameters.
  
  
  CONCLUSIONS
  Th17-related cytokines are expressed in joints of spondyloarthritis as well as RA patients. IL-23 levels, however, correlate with disease activity parameters in RA only. These results point towards a differential regulation of the Th17 cytokine system in spondyloarthritis compared with RA.
authors.affiliation: Department of Rheumatology, Ghent University Hospital, Belgium.
authors.forename: Lode
authors.initials: L
authors.lastname: Melis
authors.forename: Bernard
authors.initials: B
authors.lastname: Vandooren
authors.forename: Elli
authors.initials: E
authors.lastname: Kruithof
authors.forename: Peggy
authors.initials: P
authors.lastname: Jacques
authors.forename: Martine
authors.initials: M
authors.lastname: De Vos
authors.forename: Herman
authors.initials: H
authors.lastname: Mielants
authors.forename: Gust
authors.initials: G
authors.lastname: Verbruggen
authors.forename: Filip
authors.initials: F
authors.lastname: De Keyser
authors.forename: Dirk
authors.initials: D
authors.lastname: Elewaut
mesh_terms: D000328:Adult; D015535:Arthritis, Psoriatic / Q000276:immunology / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism*; D054418:Chemokine CCL20 / Q000276:immunology / Q000378:metabolism*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D020381:Interleukin-17 / Q000378:metabolism*; D053759:Interleukin-23 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D025241:Spondylarthritis / Q000276:immunology / Q000378:metabolism*; D013582:Synovial Fluid / Q000276:immunology / Q000378:metabolism*
chemical_list: C108355:CCL20 protein, human; D054418:Chemokine CCL20; D020381:Interleukin-17; D053759:Interleukin-23