In order to better understand the function of autoantigen-specific Treg from NOR mice, as well as their role in T1D development, we have isolated NOR mouse CD4+ T cells specific for an immunodominant p286 (a.a. p286–300) peptide of a major autoantigen, glutamic acid decarboxylase (GAD), involved in T1D. Here, CD4 is linked to type 1 diabetes mellitus.