FOXP3 and diabetes mellitus: However, independent lines of evidence in mice have pointed towards a diabetogenic role of PD-1 expression on Foxp3+ Treg cells, which included diabetes amelioration in congenic B10.Idd5+ and Idd5.1+ NOD mice (69, 99), diabetes protection of NOD mice with Foxp3+ Treg cell-specific PD-1 deletion (100), and an inverse correlation of PD-1 expression with the expression of Foxp3 and Foxp3+ Treg cell function (100, 101).