Non-deletional CD8+ T cell tolerance

Summary Immunological tolerance prevents autoimmune disease by deleting self-reactive T cell clones or impairing their function. While there is much know about how CD4+ self-reactive T cells become anergic or acquire suppressive functions, there is less known about non-deletional forms of CD8+ tolerance. The proposed research builds on our previous findings regarding CD8+ T cell tolerance to the melanocyte antigen Trp2, where non-deletional tolerance is prominent. The paucity of CD8+ T cells that react to a given antigen like Trp2 has presented a challenge to acquiring deeper mechanistic understanding. Here we employ two new TCR single chain transgenic models where either deletion or non-deletional tolerance prevails, and the frequency of Trp2 reactive clones is sufficiently high to allow mechanistic studies. Our approach will employ single cell genomics analysis (scRNAseq and scATACseq) to define the gene-regulation that inhibits non- deleted self-reactive CD8+ T cells. Further experiments will use deep sequencing of the TCRα repertoire and generate TCRα retrogenic models to define how the repertoire is shaped by self-antigens and provide functional classification of different self- reactive clones into 4 types: imperfectly deleted high-avidity clones, low-avidity anergized clones, low avidity non-anergized clones and “dangerous” clones that evade tolerance mechanisms altogether. Finally, we will use an established model of vaccination-induced vitiligo to determine which types of tolerance put animals most at risk of autoimmune disease when provoked by inflammation. This work will test the central hypothesis that while self-reactive CD8+ T cell clones with the highest avidity for self are purged from the repertoire, other self- reactive cells survive and are epigenetically repressed to maintain tolerance.