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 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.
If you want 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 Tubingen, Germany.
Dimitrov and colleagues suspected that certain hormones (such as
epinephrine, norepinephrine, adenosine and prostaglandins) might
hinder the activation of the sticky proteins by turning down the
master switch.
To test that hypothesis, 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.
Next, the researchers looked at what happened in people. Knowing
that levels of these hormones naturally drop during sleep, they
rounded up 10 healthy volunteers who were willing to spend one night
snoozing in a sleep lab and another night, approximately two weeks
later, awake in the same the same lab.
All of the volunteers had been infected with CMV, a mostly benign
virus. "We recruited healthy humans seropositive for CMV because
(they usually have) a high number of antigen-specific T cells,"
Dimitrov said in an email. That meant the researchers would have no
trouble finding CMV-targeted T cells to study in the volunteers'
blood, his team explained in the Journal of Experimental Medicine.
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During the nights designated for sleeping, volunteers were hooked up
to intravenous catheters, so researchers could draw blood samples
without disturbing anyone's slumber.
The researchers compared T cells collected on slumber-filled nights
to T cells from waking nights and found, as expected, 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.
Scientists have long known that lack of sleep can impact the immune
system, said Dr. Louis DePalo, a professor of medicine, pulmonary,
critical care and sleep medicine at the Icahn School of Medicine at
Mount Sinai in New York City.
"Multiple clinical studies have demonstrated that people who do not
get quality or sufficient sleep are more likely to get sick after
being exposed to viruses," DePalo said in an email. "This (new)
study demonstrates yet another molecular pathway where good quality
and quantity sleep may lead to immune supportive effects via immune
cells, called T cells."
DePalo, who was not involved with the new study, added that it
"therefore presents another uniquely described mechanism underlying
some of the immune supportive effects of sleep."
SOURCE: http://bit.ly/2I8OOAl Journal of Experimental Medicine,
online February 12, 2019.
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