title: Rheumatoid Fibroblast-like Synoviocytes Downregulate Foxp3 Expression by Regulatory T Cells Via GITRL/GITR Interaction.
abstract: Fibroblast-like synoviocytes (FLS) colocalize with leukocyte infiltrates in rheumatoid synovia. Proinflammatory leukocytes are known to amplify inflammation by signaling to FLS, but crosstalk between FLS and regulatory T cells (Tregs) remains uncharacterized. To address this possibility, we cocultured FLS lines derived from arthritic mice with Tregs. FLS that expressed the ligand for glucocorticoid-induced TNF receptor family-related gene (GITR) decreased expression of Foxp3 and GITR in Tregs in a contact-dependent manner. This effect was abolished by blocking antibody to GITR. On the other hand, the Tregs caused the FLS to increase IL-6 production. These results demonstrate that inflamed FLS license Tregs to downregulate Foxp3 expression via the GITRL/GITR interaction while the Tregs induce the FLS to increase their production of IL-6. Our findings suggest that the interaction between FLS and Tregs dampens the anti-inflammatory activity of Tregs and amplifies the proinflammatory activity of FLS, thereby exacerbating inflammatory arthritis.
authors.affiliation: Department of Anatomy & Cell Biology, College of Medicine, Hanyang University, Seoul 133-791, Korea.
authors.forename: Sung Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Jeehee
authors.initials: J
authors.lastname: Youn