Profiling transcriptomes, TCR repertoires, and antigenic specificities of islet-infiltrating T cells in Non Obese Diabetic mice

Type 1 Diabetes (T1D) is an autoimmune disease caused by progressive destruction of pancreatic β-cells, resulting in reduced insulin production. The role of islet-infiltrating CD4+ T cells in mediating β-cell destruction and autoantibody formation is well established. However, many of the antigen specificities of CD4+ T cells which initiate disease are undefined. In this project, we performed single cell RNA sequencing of pancreatic islet infiltrating T cells from 6-, 8- , and 10-week-old Non-Obese Diabetic (NOD) mice. NOD mice recapitulate many immunologic features of T1D and share many autoantigens with human T1D patients. Analysis of TCR repertoires revealed clonal expansion in activated and pre-exhausted effector CD4+ T cells as well as regulatory T cells. Despite subtle differences, expanded effector CD4+ T cells showed a well-defined cell state. We cloned 40 TCRs from the top expanded T cells and expressed them in Jurkat cells. We performed antigen discovery assays on these TCRs using our lab’s Signaling and Antigen-presenting Bifunctional Receptor (SABR) platform. We constructed a SABR library of 4,075 I-Ag7-restricted epitopes based on published datasets. We identified several previously reported and novel autoantigens. Surprisingly, antigenic specificities did not influence the shared phenotype dramatically. These results identify several potential autoantigens that will be valuable for diagnostic, preventative, and therapeutic purposes. Moreover, these results suggest that the islet microenvironment is a major determinant of infiltrating CD4+ T cell states. Similar studies focused on CD8+ T cells in NOD mice and CD4+ and CD8+ T cells in humans are underway. dkNET New investigator Pilot Program in Bioinformatics (PI: Joglekar) NIDDK New Investigator Gateway Award 1R03DK127447 (PI: Joglekar) PACER Innovative Discovery Award (PI: Joglekar)