title: Interleukin-15 up-regulates the expression of CD154 on synovial fluid T cells.
abstract: To investigate the role of the CD40-CD154 interaction in rheumatoid arthritis (RA), we analysed the expression of CD154 on CD3+ and CD4+ T cells in synovial fluid (SF) from patients with RA and in peripheral blood (PB) from patients and normal controls. As interleukin (IL)-15 is a potent activator of synovial T cells we wanted to study whether IL-15 also regulated the expression of CD154 on these T cells. Freshly isolated synovial T cells did not express significant levels of CD154, as evaluated using flow cytometry, whereas the expression of CD86 and human leucocyte antigen (HLA)-DR was significantly elevated on SF T cells when compared with PB T cells from patients or controls. Synovial T cells could up-regulate their CD154 expression following activation with phorbol 12-myristate 13-acetate (PMA) + ionomycin or anti-CD3 + anti-CD28 monoclonal antibodies (mAbs), but the maximal level of expression remained lower than in control T cells. IL-15 significantly increased the expression of CD154 on SF and PB T cells from patients, whereas IL-2 had minimal effects. Furthermore, IL-15 induced extensive proliferation in SF T cells. Our results show that SF T cells up-regulate the expression of CD154 in the presence of IL-15, a cytokine present in the synovium of patients with RA. These results further emphasize the role of IL-15 in the pathogenesis of RA.
authors.affiliation: Turku Graduate School of Biomedical Sciences and Turku Immunology Centre, Department of Medical Microbiology, Turku, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Möttönen
authors.forename: P
authors.initials: P
authors.lastname: Isomäki
authors.forename: R
authors.initials: R
authors.lastname: Luukkainen
authors.forename: P
authors.initials: P
authors.lastname: Toivanen
authors.forename: J
authors.initials: J
authors.lastname: Punnonen
authors.forename: O
authors.initials: O
authors.lastname: Lassila
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D023201:CD40 Ligand; D018929:Cell Culture Techniques; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology; D019409:Interleukin-15 / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008875:Middle Aged; D014066:Palatine Tonsil / Q000276:immunology; D013582:Synovial Fluid / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology*
chemical_list: D019409:Interleukin-15; D008562:Membrane Glycoproteins; D023201:CD40 Ligand