FOXP3 and diabetes mellitus: Lastly, Foxp3-deficient NOD mice with a polyclonal CD4+ T cell repertoire fail to present with insulitis and overt diabetes before they succumb at 3 weeks to severe inflammatory infiltration in multiple organs (33), precluding NOD.Foxp3-deficient mice as an experimental model to study the role of Treg cells in the autoimmune β cell protection.