It has been hypothesized that IL-2 is one of the two key candidate genes in the Idd3 locus, because the presence of an Idd3 susceptibility gene compared with the T1D resistant allele results in lower expression of IL-2 [37], and the lower expression of IL-2 can leads to T1D susceptibility due to impaired function of Tregs [38]. The gene discussed is IL2; the disease is type 1 diabetes mellitus.