Regulation of Cytotoxic CD8+ T Cells by the Circadian Clock

Most aspects of physiology, including immunity, present 24-h variations called circadian rhythms. In this review, we examine the literature on the circadian regulation of CD8(+) T cells, which are important to fight intracellular infections and tumors. CD8(+) T cells express circadian clock genes, and similar to 6% of their transcriptome presents circadian oscillations. CD8(+) T cell counts present 24-h rhythms in the blood and in secondary lymphoid organs, which depend on the clock in these cells as well as on hormonal rhythms. Moreover, the strength of the response of these cells to Ag presentation varies according to time of day, a rhythm dependent on the CD8(+) T cell clock. The relevance of CD8(+) T cell circadian rhythms is shown by the daily variations in the fight of intracellular infections. Such a circadian regulation also has implications for cancer, as well as the optimization of vaccination and immunotherapy.

Automated summary

Most aspects of physiology, including immunity, exhibit 24-hour variations called circadian rhythms. CD8(+) T cells express circadian clock genes and present circadian oscillations in their transcriptome. CD8(+) T cell counts in blood and lymphoid organs show 24-hour rhythms, dependent on the cell's clock and hormonal rhythms. The circadian rhythms of CD8(+) T cells play an important role in fighting intracellular infections and have implications for cancer treatment and immunotherapy optimization.