Genetic deficiency of PDCD1 in C57BL/6 and BALB/c mice leads to spontaneous lupus-like disease or autoimmune cardiomyopathy, respectively5,7, while non-obese diabetic (NOD) mice lacking either PD-1 or PD-L1 developed accelerated type 1 diabetes (T1D)4,6. This evidence concerns the gene PDCD1 and type 1 diabetes mellitus.