Studies in T1D patients and non-obese diabetic (NOD) mice, an animal model that mirrors many features of human T1D, have shown that CD4+ and CD8+ T cells play an important role in β-cell destruction, and that islet-specific autoreactive CD8+ T cells are the ultimate effector in β-cell attack [2]. The gene discussed is CD4; the disease is type 1 diabetes mellitus.