They showed that NOD mice carry the protective alleles of T1DM susceptibility loci, namely, major histocompatibility complex (MHC) and Idd3 and Idd5, in which Idd3 and Idd5 improves the regulatory T cells (Tregs) function and immune tolerance along with the distinct gut microbial composition with an increased abundance of Akkermansia. Here, HLA-C is linked to type 1 diabetes mellitus.