PTPRN and type 1 diabetes mellitus: T cell clones specific for β-cell antigens (e.g., G6Pase 2, insulin, pre-proinsulin, IA-2, GAD65, ZnT8 [37]) have been isolated from peripheral blood of living patients with T1D but can also be detected from control subjects [18, 23•, 24, 38•, 39–42].