title: Ectopic lymphoid neogenesis is strongly associated with activation of the IL-23 pathway in rheumatoid synovitis.
abstract: BACKGROUND
  The functional relevance of synovial ectopic lymphoid neogenesis (ELN) in rheumatoid arthritis (RA) remains unknown. As ELN correlates with the degree of tissue inflammation, we investigated whether ELN was associated with specific cytokine profiles.
  
  
  METHODS
  Synovial ELN was determined by immunohistology and long CD21 isoform (CD21L) expression. Cytokine expression was determined by multiplex enzyme-linked immunosorbent assay (ELISA) and quantitative polymerase chain reaction (PCR) as well as immunohistology in synovial fluid (SF) (n = 44) and tissue (ST) (n = 108), respectively. Production of ELN-associated chemokines by fibroblast-like synoviocytes (FLS) was studied in vitro.
  
  
  RESULTS
  Screening analysis of SF by multiplex ELISA showed higher protein levels of interleukin (IL)-23 (p = 0.018) and IL-17F (p = 0.028) in ELN+ versus ELN- samples. Other cytokines, including IL-17A, IL-6, and tumor necrosis factor (TNF)-α, were not different. The association between IL-23 and ELN was not biased by disease activity or other clinical features and was confirmed by higher IL-23 mRNA expression in ELN+ versus ELN- ST samples (p = 0.030), a correlation between IL-23 and CD21L expression in the same samples (r = 0.70 p < 0.0001), and a similar correlation in two independent ST sample sets (r = 0.778 p < 0.0001 and r = 0.817 p = 0.011). IL-23 p19 staining was neither restricted nor enhanced in close proximity of ectopic lymphoid follicles, and neither IL-23 nor IL-17A stimulation induced expression of the ELN-associated CC chemokine ligand, CCL21 and CXC chemokine ligand CXCL13, by FLS. Downstream of IL-23, CD21L expression was significantly associated with IL-17F, IL-21, and IL-22, but not IL-17A in two independent ST sample sets.
  
  
  CONCLUSIONS
  Synovial ELN in RA is strongly associated with activation of the IL-23 pathway but not with IL-17A.
authors.affiliation: Arthritis Unit, Rheumatology Department, Hospital Clinic of Barcelona and IDIBAPS, c/ Villarroel, 170, 08036, Barcelona, Spain. jcanete@clinic.ub.es.
authors.forename: Juan D
authors.initials: JD
authors.lastname: Cañete
authors.affiliation: Arthritis Unit, Rheumatology Department, Hospital Clinic of Barcelona and IDIBAPS, c/ Villarroel, 170, 08036, Barcelona, Spain. rqlcelis@gmail.com.
authors.forename: Raquel
authors.initials: R
authors.lastname: Celis
authors.affiliation: Amsterdam Rheumatology and Immunology Center/Department of Clinical Immunology and Rheumatology, Academic Medical Center/University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. n.g.yeremenko@amc.uva.nl.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Yeremenko
authors.affiliation: Arthritis Unit, Rheumatology Department, Hospital Clinic of Barcelona and IDIBAPS, c/ Villarroel, 170, 08036, Barcelona, Spain. sanmarti@clinic.ub.es.
authors.forename: Raimon
authors.initials: R
authors.lastname: Sanmartí
authors.affiliation: Amsterdam Rheumatology and Immunology Center/Department of Clinical Immunology and Rheumatology, Academic Medical Center/University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. l.m.vandiuvenvoorde@amc.uva.nl.
authors.forename: Leonie
authors.initials: L
authors.lastname: van Duivenvoorde
authors.affiliation: Arthritis Unit, Rheumatology Department, Hospital Clinic of Barcelona and IDIBAPS, c/ Villarroel, 170, 08036, Barcelona, Spain. julramga@gmail.com.
authors.forename: Julio
authors.initials: J
authors.lastname: Ramírez
authors.affiliation: Amsterdam Rheumatology and Immunology Center/Department of Clinical Immunology and Rheumatology, Academic Medical Center/University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. i.c.blijdorp@amc.uva.nl.
authors.forename: Iris
authors.initials: I
authors.lastname: Blijdorp
authors.affiliation: Rheumatology Department, Instituto de Investigación Hospital 12 de Octubre (I + 12), Avda de Córdoba, s/n, 28041, Madrid, Spain. cmgarciaherrero@gmail.com.
authors.forename: Carmen M
authors.initials: CM
authors.lastname: García-Herrero
authors.affiliation: Rheumatology Department, Instituto de Investigación Hospital 12 de Octubre (I + 12), Avda de Córdoba, s/n, 28041, Madrid, Spain. jlpablos@h12o.es.
authors.forename: José L
authors.initials: JL
authors.lastname: Pablos
authors.affiliation: Amsterdam Rheumatology and Immunology Center/Department of Clinical Immunology and Rheumatology, Academic Medical Center/University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. d.l.baeten@amc.uva.nl.
authors.forename: Dominique L
authors.initials: DL
authors.lastname: Baeten
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000473:pathology*; D002828:Choristoma; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D020381:Interleukin-17 / Q000276:immunology; D053759:Interleukin-23 / Q000276:immunology*; D008221:Lymphoid Tissue; D008297:Male; D008875:Middle Aged; D060888:Real-Time Polymerase Chain Reaction; D013583:Synovial Membrane / Q000473:pathology*; D013585:Synovitis / Q000276:immunology / Q000473:pathology
chemical_list: C440021:IL17F protein, human; D020381:Interleukin-17; D053759:Interleukin-23