title: Increased expression of IL-15 in the synovium of patients with rheumatoid arthritis compared with patients with Yersinia-induced arthritis and osteoarthritis.
abstract: Recently, a new player in the cytokine network has been described that is produced by monocytes and can be detected in the rheumatoid synovium: interleukin-15 (IL-15). Since this cytokine may play a role in the accumulation and activation of T-cells, B-cells, and natural killer (NK) cells characteristic of synovial tissue (ST) from patients with rheumatoid arthritis (RA), the expression of IL-15 was studied in ST from RA patients in comparison with ST from patients with reactive arthritis (ReA) and osteoarthritis (OA) and the phenotype of IL-15-positive cells was determined. IL-15 expression was investigated by immunohistochemical analysis of ST from ten patients with RA, ten patients with Yersinia enterocolitica-induced ReA, and nine patients with OA. The immunohistological findings were quantified and the results obtained in the different patient groups were compared. To determine the phenotype of IL-15-expressing cells, double-labelling immunofluorescence was performed. The expression of IL-15 was significantly higher in ST from patients with RA than in ST from patients with ReA or OA. In double-label experiments, co-expression was observed with markers for macrophages, T-cells, and NK cells. The composition of the cellular infiltrate in the synovium of patients with RA might be partly explained by the specific increase in expression of IL-15 in rheumatoid ST. It can be speculated that IL-15 production by inflammatory cells other than macrophages may occur in the rheumatoid synovium.
authors.affiliation: Department of Rheumatology, Leiden University Hospital, The Netherlands.
authors.forename: E W
authors.initials: EW
authors.lastname: Thurkow
authors.forename: I M
authors.initials: IM
authors.lastname: van der Heijden
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
authors.forename: T J
authors.initials: TJ
authors.lastname: Smeets
authors.forename: M R
authors.initials: MR
authors.lastname: Daha
authors.forename: P M
authors.initials: PM
authors.lastname: Kluin
authors.forename: A E
authors.initials: AE
authors.lastname: Meinders
authors.forename: P P
authors.initials: PP
authors.lastname: Tak
mesh_terms: D000328:Adult; D000368:Aged; D016918:Arthritis, Reactive / Q000276:immunology / Q000378:metabolism*; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D019409:Interleukin-15 / Q000378:metabolism*; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000276:immunology / Q000378:metabolism; D000091402:Prohibitins; D013583:Synovial Membrane / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D015009:Yersinia Infections / Q000276:immunology / Q000378:metabolism; D015008:Yersinia enterocolitica
chemical_list: D019409:Interleukin-15; C000717331:PHB2 protein, human; D000091402:Prohibitins