The human immune system is an early riser

Circadian clocks, which regulate most of the physiological processes of living beings over a rhythm of about 24 hours, are one of the most fundamental biological mechanisms. By deciphering the cell migration mechanisms underlying the immune response, scientists have shown that the activation of the immune system is modulated according to the time of day. Indeed, the migration of immune cells from the skin to the lymph nodes oscillates over a 24-hours period. Immune function is highest in the resting phase, just before activity resumes -- in the afternoon for mice, which are nocturnal animals, and early morning for humans. These results suggest that the time of day should possibly be taken into account when administering vaccines or immunotherapies against cancer, in order to increase their effectiveness.