FOXP3 and autoimmune disease: Whilst previous data has shown that forkhead box protein P3 (Foxp3) expressing Treg cells is key in suppressing immune responses and prevents the development of autoimmune diseases, Komatsu et al. have recently shown that Foxp3+ T-cells can actually convert into pathogenic Th17 cells (named, in the study, as exFoxp3 TH17 cells) with arthritogenic and autoreactive properties.