A Hypermorphic Nfkbid Allele Contributes to Impaired Thymic Deletion of Autoreactive Diabetogenic CD8+ T Cells in NOD Mice

Abstract

In both NOD mice and humans, the development of type 1 diabetes (T1D) is dependent in part on autoreactive CD8⁺ T cells recognizing pancreatic β cell peptides presented by often quite common MHC class I variants. Studies in NOD mice previously revealed that the common H2-K^d and/or H2-D^b class I molecules expressed by this strain aberrantly lose the ability to mediate the thymic deletion of pathogenic CD8⁺ T cell responses through interactions with T1D susceptibility genes outside the MHC. A gene(s) mapping to proximal chromosome 7 was previously shown to be an important contributor to the failure of the common class I molecules expressed by NOD mice to mediate the normal thymic negative selection of diabetogenic CD8⁺ T cells. Using an inducible model of thymic negative selection and mRNA transcript analyses, we initially identified an elevated Nfkbid expression variant as a likely NOD-proximal chromosome 7 region gene contributing to impaired thymic deletion of diabetogenic CD8⁺ T cells. CRISPR/Cas9-mediated genetic attenuation of Nfkbid expression in NOD mice resulted in improved negative selection of autoreactive diabetogenic AI4 and NY8.3 CD8⁺ T cells. These results indicated that allelic variants of Nfkbid contribute to the efficiency of intrathymic deletion of diabetogenic CD8⁺ T cells. However, although enhancing thymic deletion of pathogenic CD8⁺ T cells, ablating Nfkbid expression surprisingly accelerated T1D onset that was associated with numeric decreases in both regulatory T and B lymphocytes in NOD mice.