title: Interleukin-34 in rheumatoid arthritis: potential role in clinical therapy.
abstract: OBJECTIVE
  To investigate, whether interleukin (IL)-34 can be used as marker for treatment effectiveness in rheumatoid arthritis (RA).
  
  
  METHODS
  Serum samples were collected from 35 healthy participants and 83 patients with RA before as well as 4 weeks and 12 weeks after treatment initiation with the tumor necrosis factor α (TNF-α) inhibitor Etanercept. Related clinical data and hand radiograms of the patients were evaluated and serum IL-34, IL-6, IL-8, TNF-α, matrix metalloproteinase-3 (MMP-3) in addition to anti-cyclic citrullinated peptide (CCP) antibody concentrations were measured by ELISA.
  
  
  RESULTS
  Serum concentrations of IL-34, IL-6, IL-8, TNF-α, MMP-3 and anti-CCP antibodies were markedly elevated in RA patients compared with controls (P<0.001), significantly decreased during treatment and correlated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and RA disease activity (P<0.05). IL-34 correlated withIL-6, IL-8, TNF-α, MMP-3 and anti-CCP antibodies in RA patients at baseline (P<0.01) and also with IL-8, MMP-3, IL-6, and DAS28 changes during therapy. Patients in stage III of hand X-ray RA scores had higher IL-34 serum concentrations than in stage II (P<0.05). IL-34 level decreased significantly (P<0.01) starting from 4 weeks after therapy initiation.
  
  
  CONCLUSIONS
  IL-34 serum concentrations correlated with inflammatory cytokines before and during therapy and were significantly higher in stage III of hand X-ray score patients than in stage II participants. IL-34 might be used both as a biomarker for RA diagnosis and therapy efficiency.
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Fangze
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Ding
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Cuili
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Ding
authors.initials: D
authors.lastname: Song
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Xuetong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Tianjiao
authors.initials: T
authors.lastname: Ma
authors.affiliation: Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University Changchun 130033, China.
authors.forename: Liqi
authors.initials: L
authors.lastname: Bi
keywords: IL-34; IL-6; IL-8; MMP-3; Rheumatoid arthritis; TNF-α