CD4 and type 1 diabetes mellitus: There is increasing evidence from patients with T1D that CD8+ T cells play a crucial role in the development of disease.25, 26, 27, 28, 29, 30 At least in NOD mice, ppins or insulin is the primary beta cell autoantigen targeted by autoreactive CD4+ and CD8+ T cells31 and thereby triggers the initial steps of beta cell destruction and inflammation.32