I loooove to sleep. If I don’t get a solid eight hours of sleep, I wake up feeling sick. And, if I’m sleep deprived for several days in a row I’m apt to develop a sore throat and maybe even a cold. For a long time, I thought this was all in my head. But, as it turns out, our immune system is closely linked to our body’s internal time keeping system, known as our circadian clock.
I was also under the impression that our circadian clock consists mostly of melatonin, a hormone that we produce that makes us sleepy. However, our circadian clock is actually comprised of a variety of hormones, and other proteins, that regulate many different biological processes including development and metabolism. When light hits certain receptors in our eyes, it sends a signal to our brain, which then directs these many clock proteins to jump into action.
A recent study published in the journal Science shows that clock proteins regulate the development of a certain type of white blood cell called a Th17 cell. Th17 cells are named after the primary protein they produce called IL-17, which acts to recruit other immune cells. In normal numbers, Th17 cells work to help the body fight bacterial and fungal infections.
In this study, researchers gave mice jet lag by shifting their light/dark cycles by six hours every four days, and found that these mice had twice the numbers of Th17 cells in their gut and spleen as those mice with normal light/dark cycles. When there are too many Th17 cells, the immune system begins to cause illness rather than fight it. In fact, various studies have suggested that the predisposition, cause, and progression of cancer and autoimmune diseases, both of which can involve rogue Th17 cells, stem from disruptions in light/dark cycles.
Disruptions in circadian rhythms don’t just occur in people who constantly travel or work the night shift. All of us, who stay up late looking at bright TVs, laptops and phone screens, are inadvertently messing with our immune systems. I guess this means I should close my laptop so I can get more…ZZZZZZZZ.