CD4 and rheumatoid arthritis: The frequency and numbers of Foxp3+ T cells in the periphery and thymus of dnRara mice were similar to control mice (Figures S1A and S1B), indicating that the increase in Th17 cells was not a consequence of reciprocal regulation by RA of Foxp3+CD4+ T cells and Th17 cells (Mucida et al., 2007).