Schematic of the NFAT interaction partners in iTreg cells. iTregs are induced by high TGF-β concentrations via the TGF-βR in combination with low TCR signals. IL-2 via the IL-2R induces STAT5 that, in combination with NFAT, the Smad2/3 complex, Sp1, CREB, and AP-1, binds to the Foxp3 promoter region. Foxp3, the master transcription factor of regulatory T cells, subsequently inhibits I-Smad7 and RORγt and, together with NFAT and Runx1, induces the expression of CTLA4, CD25, and GITR.