FOXP3 and rheumatoid arthritis: Interestingly, Forkhead box P3+ cells (FOXP3+), which are immunosuppressive cells that maintain immune homeostasis, were found to undergo conversion into TH17 cells in the synovia of rheumatoid arthritis (RA) patients and arthritic DBA1 mice, pointing to a transition of FOXP3+ T cells into TH17 cells [7,8].