Summary Self-tolerance requires that auto-reactive T cells either be physically eliminated, sequestered away from self- antigen and/or incapacitated in their response to normal tissues. There have been many studies on deletional tolerance and “ignorance” of self-antigens among CD8+ T cells, but much less is understood about how anergy regulates that response T cell response. Studies on this issue are especially urgent, since recent data suggest that anergy is the prevalent mechanism of CD8+ T cell self-tolerance in humans – but we lack appropriate mouse models to investigate this critical mechanism. We address this issue with studies on mouse CD8+ T cells that recognize the normal melanocyte antigens, which we demonstrate are tolerant through a form of cell- intrinsic anergy. In Aim 1, we explore the basis for this anergy, building on preliminary studies to investigate whether self-reactive CD8+ T cells are prone to apoptotic cell death following activation and using RNA-seq and ATAC-seq approaches to define the gene expression and chromatin accessibility status of anergic versus functional CD8+ T cells. In Aim 2, we test the reversibility of anergy, evaluating the role of continued self- antigen exposure in maintaining this state, and we formally explore the potential role of Treg, as a cell-extrinsic mechanism of inducing or perpetuating CD8+ T cell anergy. Finally, in Aim 3, we examine how the lack of physiological exposure to normal skin infections and inflammation may compromise the value of current mouse models for induction of autoimmune vitiligo (destruction of normal melanocytes following breakdown of CD8+ T cell self-tolerance to melanocyte antigens). Our studies utilize models of acute skin inflammation and infection, and also inbred mice that have been naturally infected with normal mouse microbes (“normal microbial experience” mice, also called “dirty” mice) – a model which we developed at the University of Minnesota to enhance mouse studies with improved relevance to humans.