CTLA4 and diabetes mellitus: Further analysis of the Idd3/5 region showed that removal of protective alleles at a subcongenic region from the Idd3/5 region as in the Idd3/5.2/5.3 strain results in a 15% incidence of disease upon anti PDL1 treatment in contrast to no incidence of disease in the Idd3/5 group, which supports the role of Ctla4 at the Idd5.1 locus in preventing diabetes in a concerted interplay with Idd3. Although Idd3/5.2/5.3 mice do not develop diabetes, an increase of insulitis in Idd3/5.2/5.3 mice as compared to Idd3/5 has been reported [33].