TGFB1 and rheumatoid arthritis: In this study, we investigated the effect of inhibiting TGF-β1 signaling with the TGF-βRI inhibitor SB-505124 on murine Th17 differentiation in vitro, on cytokine production by human RA synovial explants ex vivo, and on the development of joint pathology in vivo during Th17-driven experimental arthritis.