German researchers have discovered that sleep in one way improves the body's ability to fight a cold. The dream seems to boost the power of certain immune cells by improving their chances of attachment and ultimately destroying cells infected with viruses.
Researchers have focused their attention on T-cells that fight infections. When T cells detect a viral infected cell, they activate a sticky protein known as integrin that allows them to adhere to this cell. Researchers have been able to prove that lack of sleep, as well as prolonged periods of stress, lead to higher levels of hormones that seem to block the main switch that activates sticky proteins.
If you want your immune system to be set to fight invaders, "get the right amount of sleep every night and avoid chronic stress," said study director Stoyan Dimitrov, a researcher at the University of Tübingen, Germany.
Dimitrov and colleagues suspect that some hormones (such as epinephrine, norepinephrine, adenosine, and prostaglandins) can prevent the activation of sticky proteins by dropping the main switch.
To test this hypothesis, they are studying cells of humans infected with cytomegalovirus (CMV). T-cells should seek for and kill cells infected with CMV, but when patients' T cells are mixed with suspicious hormones in the tubes, the ability of T cells to activate sticky proteins decreases.
The researchers then looked at what had happened in people. Knowing that levels of these hormones naturally fell during sleep, they surrounded 10 healthy volunteers who were willing to spend one night sleeping in a sleeping lab, and another night, approximately two weeks later, in the same lab .
All volunteers were infected with CMV, a predominantly benign virus. "We hired healthy people who are seropositive for CMV because (they usually have) a large number of antigen-specific T cells," Dimitrov said in an email. This means researchers will have no trouble finding CMV-targeted T cells to study in the blood of volunteers, his team said in the Journal of Experimental Medicine.
During the sleeping nights, the volunteers were hooked on intravenous catheters so that the researchers could take blood samples without disturbing anyone's sleep.
Researchers compared T-cells collected in the night full of sleep with T-cells from waking nights, and found that volunteers were expected to sleep lower levels of stress hormones than when volunteers stayed overnight . More importantly, night sleep T-cells have activated more sticky proteins that fight infections than waking nights, which means they are more powerful.
Scientists have long known that lack of sleep can affect the immune system, says Dr. Louis Depallo, Professor of Medicine, Pulmonary, Critical Care and Sleep Medicine at the Icahn School of Medicine in Mount Sinai, New York.
"Numerous clinical trials have shown that people who do not get quality or sufficient sleep are more likely to become ill after being exposed to viruses," Depalo said in an email. "This (new) study demonstrates another molecular pathway where good quality and quantity of sleep can lead to immune supportive effects through immune cells called T-cells."
DePalo, who was not involved in the new study, adds that "it is therefore another uniquely described mechanism that underlies some of the immune supportive effects of sleep."