Say g’night, cold!

Researchers discover how sleep helps fight viruses

It looks like your mother was right: when you’ve got a cold, sleep may be the best medicine.

German researchers have discovered one way sleep improves the body’s ability to fight off a cold. Sleep, it seems, strengthens the potency of certain immune cells by improving their chances of attaching to — and eventually destroying — cells infected with viruses.

The researchers focused their attention on T cells, which battle infections. When T cells spot a virally infected cell, they activate a sticky protein known as an integrin that allows them to adhere to that cell. The researchers were able to prove that lack of sleep, as well as sustained periods of stress, lead to higher levels of hormones that appear to block the master switch that activates the sticky proteins.

To have your immune system tuned up to fight off invaders, “get the needed amount of sleep every night and avoid chronic stress,” said study leader Stoyan Dimitrov, a researcher at the University of TÜbingen, Germany.

Dimitrov and colleagues suspected that certain hormones might hinder the activation of the sticky proteins by turning down the master switch.

To test this, they studied cells from people infected with cytomegalovirus (CMV). T cells are supposed to seek out and destroy cells infected with CMV, but when patients’ T cells were mixed with the suspect hormones in test tubes, the T cells’ ability to activate the sticky proteins dropped.

Knowing that levels of these hormones naturally drop during sleep, they rounded up 10 healthy volunteers willing to spend one night snoozing in a sleep lab and another night awake in the same the same lab.

The volunteers had been infected with CMV, a mostly benign virus. That meant the researchers would have no trouble finding CMV-targeted T cells to study in the volunteers’ blood, Dimitrov’s team explained in the Journal of Experimental Medicine

During the nights designated for sleeping, volunteers were hooked up to intravenous catheters, so researchers could draw blood samples without disturbing anyone.

The researchers compared T cells collected on slumber-filled nights to T cells from waking nights and found that when volunteers were sleeping, levels of stress hormones were lower than when volunteers stayed up all night. More important, T cells from sleeping nights had more infection-fighting sticky proteins activated than those from waking nights, meaning they were more potent.