CD4 and diabetes mellitus: Once CD4+ and CD8+ T cells are stimulated, these cells then secrete the cytokines IL-1β, TNF-α and IFN-γ, which induce the migration of CD8+ cytotoxic T cells to the islets, activating a final common pathway of β-cell apoptosis through the NF-κB and Fas pathways, resulting in progressive β-cell loss in diabetes [9].