Abstract In response to chronic viral infection or in tumor microenvironment, antigen(Ag)-specific CD8 T cells undergo alternative activation processes, called exhaustion. Exhausted CD8 T cells lose their proliferation and effector gene expression, thus allowing viral infection or tumor growth to persist despite the initial expansion of antigen-specific clones. Although the precise mechanism driving T cell exhaustion is unknown, literature suggests that exposure of T cells to excessive oxidative stress contribution to the establishment of exhaustion. In this small grant, we propose to generate genetically modified mice that facilitate visualization of cells that are exposed to oxidative stress and use the tools for future studies for T cell exhaustion.