FOXP3 and Autoimmunity: In this context, it has been shown that defects in IL-2/IL-2R signaling in Treg cells profoundly contribute to the development of autoimmunity since IL-2 has a key role in the control of Foxp3 expression in CD4+CD25+ cells, through the phosphorylation of STAT3 and STAT5 proteins (244–246).