In the nonobese diabetic mouse model of type 1 diabetes (T1D), KLRG1 is expressed on Foxp3+ Treg cells in the pancreatic islets and plays a role in inhibiting pancreatic autoimmunity, resulting in a decrease in the proliferative and inhibitory functions of Foxp3+ Treg cells. Here, KLRG1 is linked to type 1 diabetes mellitus.