Elucidating mechanisms of deletional and non-deletional CD8+ T cell tolerance 3250

Description CD8+ T cells encounter several checkpoints to enforce tolerance to self antigens. Thymic clonal deletion is incomplete; self-reactive CD8+ T cells can be found in healthy mice and humans. The mechanisms preventing these escapees from driving autoimmunity are not fully elucidated. We focused on T cells specific for melanocyte antigen Trp2 and sequenced T cell receptors (TCRs) from Trp2/Kb-tetramer+ cells from WT and Trp2-KO (KO) mice and chose two clones to study further. One clone (Non-DEL) was found in both WT and KO, and the other (DEL) was only seen in KO mice (in which Trp2 is non-self). Fixed TCRβ chain retrogenic mice expressing Non-DEL and DEL (with endogenously rearranged TCR?) had ∼5% Trp2/Kb+ CD8+ T cells in KO mice. There was strong but incomplete deletion of Trp2/Kb+ cells in DELβ WT retrogenic mice, while percent of Trp2/Kb+ cells in Non-DELβ retrogenic mice was the same in WT and KO hosts. Tetramer MFI was higher in KO DELβ vs Non-DELβ, suggesting an avidity threshold required for deletion. Trp2/Kb-specific T cells from both retrogenic TCRβ in WT hosts were tolerant to self antigen but could be coaxed to induce autoimmunity (melanocyte destruction/vitiligo) with peptide vaccination and skin irritation, demonstrating tolerance can be broken with inflammatory cues. Non-DELβ and DELβ are being generated as transgenic mice, which will aid in further characterization of central and peripheral tolerance mechanisms required to prevent CD8+ T cell-mediated autoimmunity.