CD4 and rheumatoid arthritis: Although Tr1 cells can generate IL-10 (but not IFN-γ) in the presence of Dex and Vit D3 when adoptively transferred in a CIA model, these cells prevent RA by slightly decreasing the expression of IL-17 (no statistical significance) via production of CD4+IFN-γ+ T cells compared to Treg-treated CIA mice (Fig. 1E).