As controls for disease resistance independent of the Il2 locus, we used NOR mice, which represent a major histocompatibility complex-matched diabetes-resistant control strain for NOD mice that share the Idd3NOD locus, but carry Idd5.2, Idd9/11 and Idd13 B6 protective loci, and NOD.Idd6C3H congenic mice, which share the Idd3 locus but are less susceptible to T1D development13. Here, IL2 is linked to type 1 diabetes mellitus.