As CD25−/low FOXP3+ Tregs also represent a subset of functional Tregs, we defined Tregs as FOXP3+CD127−/low and examined circulating Helios+ and Helios− Treg subpopulations in 68 autoantibody-positive T1D individuals and 68 age-matched healthy controls. This evidence concerns the gene FOXP3 and type 1 diabetes mellitus.