FOXP3 and rheumatoid arthritis: In these respects, it is striking that CD4+ Foxp3+ T cell development from naïve CD4+ T cells is strongly induced by co-treatment with TGFβ and retinoid, including RA and synthetic retinoids such as Am580, and is suppressed by the retinoid antagonist LE540 [94-102] (Fig. 1).