Health Byte
Can catching a cold give you asthma?
Researchers have been wondering if contracting respiratory illnesses
like the common cold can lead to a person developing a chronic lung
disease. A study from Washington University, St. Louis, found that
immune cells that are sent to the lungs to fight infection can
accumulate and cause inflammatory problems.
Eventually, this inflammation can lead to long-term lung problems
such as asthma. These findings came about from research involving immune
cells known as macrophages.
According to MedicineNet.com, a macrophage is defined as "a type of
white blood cell that ingests foreign material. Macrophages are key
players in the immune response to foreign invaders of the body, such as
infectious microorganisms."
Large accumulations of macrophages
"In general, scientists thought this type of macrophage was involved
in the repair of the lung," explains senior study author Michael J.
Holtzman, a professor of medicine at Washington University's School of
Medicine. "That may be true in some cases. But like many things in
nature, too much of a good thing can become a bad thing."
As the macrophages accumulate in number, at some point they appear to
stop responding as they should to acute viral infections and begin to
respond as they would for invasions by parasites or allergens.
In their study, Holtzman and his team discovered that these
macrophages also expressed high levels of a protein called TREM-2.
This protein performs an important service to the macrophages by
clinging to their surface as they fight off infection. After the
infection has been destroyed, the TREM-2 is removed from the macrophage
surface. In the past, it was thought that the removed TREM-2 was
inactive.
"We were surprised to find that this cleaved form of TREM-2 is
actually quite active," Holtzman says. "It potently prevents the
programmed death of macrophages, promoting their survival. So this form
of TREM-2 allows for macrophages to hang around longer than they
should."
The cleaved TREM-2 encourages macrophage accumulation and increases
the development of inflammatory disease. By discovering the role of
TREM-2 in this inflammatory process, scientists hope to narrow down
successful methods of treatment.
"We don't yet have a specific drug to interrupt the TREM-2 process,"
Holtzman says. "But we now understand the controls for the process, so
our drug discovery program is already screening for compounds that might
keep TREM-2 at normal levels."
TREM-2 may be linked to other inflammatory conditions
Researchers discovered that the cleaved TREM-2 did not appear to be
important in the beginning immune system response to infection. So they
don't think blocking it will interfere with the body's ability to fight
off infections in the respiratory system.
Lead study author Holtzman also hypothesizes that TREM-2 might play a
role in the development of inflammatory diseases in other areas of the
body. For example, increased risk for inflammation in the brain related
to Alzheimer's and Parkinson's have been linked with TREM-2.
-The Alternative Daily
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