A hypermorphic Nfkbid allele represents an Idd7 locus gene contributing 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 {beta}-cell peptides presented by often quite common MHC class I variants. Studies in NOD mice previously revealed the common H2-Kd and/or H2-Db class I molecules expressed by this strain acquire an aberrant ability to mediate pathogenic CD8+ T-cell responses through interactions with T1D susceptibility (Idd) genes outside the MHC. A gene(s) mapping to the Idd7 locus on 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 is likely an NOD Idd7 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 allelic variants of Nfkbid represent an Idd7 gene contributing to the efficiency of intrathymic deletion of diabetogenic CD8+ T-cells. However, while enhancing thymic deletion of pathogenic CD8+ T-cells, ablation of Nfkbid expression surprisingly accelerated T1D onset in NOD mice likely at least in part by numerically decreasing regulatory T- and B-lymphocytes (Tregs/Bregs), thereby reducing their peripheral immunosuppressive effects.