CD8~+ T cells are crucial for major histocompatibility complex (MHC) class I-restricted antiviral and antitumor immunity. A major unsolved question in T cell biology is how the size of the pool of antigen-inexperienced naive T cells is regulated. To stay alive, naive T cells seem to manage intracellular signals induced by tonic environmental stimulants, including self antigens and survival cytokines. In addition, T cells must maintain their quiescent state while preserving the ability to induce robust immune responses to foreign antigens. Maintenance of the size of the pool of naive CD8~+ T cells is dependent on the recognition of self peptide in the context of MHC class I by the T cell antigen receptor (TCR), as well as interleukin 7 (IL-7).
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