Regulators of CD8+ T cell exhaustion.

T cell exhaustion is an adaptive and distinct cell fate that emerges in response to persistent antigen stimulation, primarily in chronic infections and cancer. It is characterized by a progressive loss of effector functions and sustained expression of multiple inhibitory receptors. Progression to T cell exhaustion is driven by persistent antigen stimulation through the T cell receptor and is modulated by signals from co-stimulatory and inhibitory molecules as well as by microenvironmental factors such as cytokines, metabolites and neuronal factors. These extrinsic cellular factors reshape the T cell transcriptome, epigenome and metabolism towards a state of exhaustion through critical intrinsic cell regulators. In this Review, we summarize our current understanding of the regulators involved in T cell exhaustion, highlighting their roles in directing the fates and functionalities of distinct exhausted T cell subsets and how they may be harnessed for the development of improved immunotherapies against cancer and chronic infections.