IL21 and rheumatoid arthritis: Synovial fibroblasts were isolated from RA patients and cultured with Th17 cytokines including interleukin (IL)-17, IL-21, and IL-22 and SKI306X, and tumor necrosis factor (TNF)-α, IL-1β, and receptor activator of nuclear factor kappa-Β ligand (RANKL) expression and production were investigated using real-time PCR and ELISA of culture media.