Immunity varies with rhythm of body clock

It has been found that immune system & the body’s internal clock are intimately tied.

Blood cells that fight disease ebb & flow with the body’s daily circadian rhythms. Levels of circulating T-cells peak at night time, for e.g., & then gradually subside. Studies have also shown that the immune system reacts to certain infections by manipulating circadian clock genes, promoting sleep & causing fatigue that often accompanies illness.

Now, new research helps solidify the idea that our susceptibility to infection depends on the time of the day.  A study showed that even the success of vaccination may hinge on circadian fluctuations. The researchers found that circadian rhythms influenced levels of an immune protein called Toll-like receptor 9 or TLR9, causing a daily peak & nadir. A study showed that when mice were infected at the low point of TLR9 activity developed severe sepsis & died much earlier than those exposed when TLR9 was high.

In another study, mice vaccinated near the daily TLR9 peak had stronger immune responses than those vaccinated at the circadian low point. The researchers pointed out that these fluctuations may have evolved as a way to maximize protection against disease like malaria- carried by mosquitoes that typically exhibit daily feeding patterns.

The research might also explain why jet lag, which throws off circadian rhythms has been shown to affect immunity.