IL-17 is a pro-inflammatory mediator that is expressed in rheumatoid arthritis (RA) joint tissue and joint fluid. IL-17 is produced by subset of white blood cells called TH-17 cells. TH-17 cells play an important role in initiation and progression of animal models of arthritis. Additionally, IL-27 is shown to suppress maturation of IL-17 producing cells. Therefore, in this proposal, Dr. Shahrara plans to inhibit maturation of TH-17 cells by over producing IL-27 in an animal model of arthritis and determining whether they can reduce inflammation, bone erosion and inflammatory mediators. Completion of this proposal will determine whether IL-27 can be utilized as a new therapeutic option for patients with RA.