Using a spontaneous model of type 1 diabetes NOD mice, we have reported that splenic DCs expressing an active form of Stat5b transcription factor (Stat5b-CA.DCs) exhibit the signature of tolerogenic DCs such as expressing high levels of PD-L1 and PD-L2, producing a large amount of TGF-β and protecting NOD mice from the development of autoimmune diabetes [13, 14, 39]. This evidence concerns the gene PDCD1LG2 and type 1 diabetes mellitus.