title: IL-6-driven STAT signalling in circulating CD4+ lymphocytes is a marker for early anticitrullinated peptide antibody-negative rheumatoid arthritis.
abstract: OBJECTIVE
  A previously identified signal transduction and activator of transcription-3 (STAT3) target-enriched gene signature in circulating CD4+ T cells of patients with early rheumatoid arthritis (RA) was prominent in autoantibody-negative individuals. Here, interleukin (IL)-6-mediated STAT signalling was investigated in circulating lymphocytes of an independent early arthritis patient cohort, seeking further insight into RA pathogenesis and biomarkers of potential clinical utility.
  
  
  METHODS
  Constitutive and IL-6-induced expression of phosphorylated STAT1 (pSTAT1) and pSTAT3 was determined in T and B cells using Phosflow cytometric analysis in patients with RA and controls. Contemporaneous levels of serum cytokines were measured by immunoassay. Induced gene expression was measured in cultured CD4+T cells by quantitative real-time PCR.
  
  
  RESULTS
  Among circulating lymphocytes of 187 patients with early arthritis, constitutive pSTAT3 correlated with serum IL-6 levels maximally in CD4+ T cells. Increased constitutive pSTAT3, but not pSTAT1, was observed in circulating CD4+ T cells of patients with early anticitrullinated peptide autoantibody (ACPA)-negative RA compared with disease controls, and these levels decreased alongside markers of disease activity with IL-6R-targeted treatment. Among patients presenting with seronegative undifferentiated arthritis (UA) the ratio of constitutive pSTAT3:pSTAT1 in CD4+ T cells contributed substantially to an algorithm for predicting progression to classifiable RA during a median of 20 months follow-up (area under receiver operator characteristic curve=0.84; p<0.001).
  
  
  CONCLUSIONS
  Our findings support a particular role for IL-6-driven CD4+ T cell activation via STAT3 during the induction of RA, particularly as a feature of ACPA-negative disease. CD4+ T cell pSTAT measurements show promise as biomarkers of UA-RA progression and now require independent validation.
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: Amy E
authors: AE
authors: Anderson
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: Arthur G
authors: AG
authors: Pratt
authors: The University of Queensland Diamantina Institute, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors: Mamdouh A K
authors: MA
authors: Sedhom
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: John Paul
authors: JP
authors: Doran
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: Christine
authors: C
authors: Routledge
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: Ben
authors: B
authors: Hargreaves
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: Philip M
authors: PM
authors: Brown
authors: The University of Queensland Diamantina Institute, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors: Kim-Anh
authors: KA
authors: Lê Cao
authors: National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, UK.
authors: John D
authors: JD
authors: Isaacs
authors: The University of Queensland Diamantina Institute, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors: Ranjeny
authors: R
authors: Thomas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D001402:B-Lymphocytes / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D016207:Cytokines / Q000097:blood; D018450:Disease Progression; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D010766:Phosphorylation; D060888:Real-Time Polymerase Chain Reaction; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D016207:Cytokines; C508600:IL6 protein, human; D015850:Interleukin-6; D010456:Peptides, Cyclic; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C487763:cyclic citrullinated peptide
keywords: Cytokines; Early Rheumatoid Arthritis; T Cells
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