In ‘knock-in’ mice expressing a DTR/GFP fusion protein from an IRES down-stream of the endogenous Foxp3 gene (Foxp3IRES-DTR/GFP) on a non-autoimmune genetic background, DT-mediated Treg cell-ablation in young and adult Foxp3IRES-DTR/GFP mice resulted in an autoimmune disease similar to that observed in Foxp3-deficient mice (8). This evidence concerns the gene FOXP3 and autoimmune disease.