The lack of T1D initiation in the presence of severe insulitis observed in the Idd3/Idd5.1/Idd5.3 and Idd3/Idd5.3 strains indicates that the interaction between Idd5.2/Nramp1 and Idd3 is not important for T1D protection, but does contribute to the marked reduction in insulitis (41, 54). Here, SLC11A1 is linked to type 1 diabetes mellitus.