PDCD1 and diabetes mellitus: A primary role for cytotoxic CD8+ T cells in the pathogenesis of CPI-DM is suggested by finding CD8+ cells infiltrating the islets in a patient who succumbed with CPI-DM and in NOD mice with PD-L1–induced diabetes, consistent with the known role of PD-1 signaling in limiting the expansion of CD8+ T cells (59).