FOXP3 and Autoimmunity: Furthermore, the overexpression of Foxp3 helps to increase the absolute number of Treg cells and CD4+CD25−Foxp3− T cells transfected with Foxp3 show immune suppressive properties and prevent autoimmunity in a mouse model This evidence indicates that the transcriptional factor Foxp3 is crucial for maintaining the suppressive activity of Treg cells, both in human and mice.