We tested the following 14 NOD congenic strains to examine the genetic protection due to a range of genes and gene combinations which can possibly contribute to resisting the precipitation of type 1 diabetes following PDL1 blockade: Idd3, Idd10/18, Idd3/10/18, Idd5 (which includes the subcongenic regions of Idd5.1, Idd5.2, and Idd5.3), Idd5.1, Idd5.2, Idd5.3, Idd5.2/5.3, Idd3/5, Idd3/5.2/5.3, Idd9 (which includes the sub-congenic regions of Idd9.1, Idd9.2 and Idd9.3), Idd9.1, Idd9.2 and Idd9.3. This evidence concerns the gene CD274 and type 1 diabetes mellitus.