Animal study suggests body's defense system doesn't seem to work as well at cooler temperatures
WebMD News from HealthDay
By Alan Mozes
HealthDay Reporter
TUESDAY, Jan. 6, 2015 (HealthDay News) -- Though it's never been scientifically confirmed, conventional wisdom has it that winter is the season of sniffles.
Now, new animal research seems to back up that idea. It suggests that as internal body temperatures fall after exposure to cold air, so too does the immune system's ability to beat back the rhinovirus that causes the common cold.
"It has been long known that the rhinovirus replicates better at the cooler temperature, around 33 Celsius (91 Fahrenheit), compared to the core body temperature of 37 Celsius (99 Fahrenheit)," said study co-author Akiko Iwasaki, a professor of immunobiology at Yale University School of Medicine.
"[But] the reason for this cold temperature preference for virus replication was unknown. Much of the focus on this question has been on the virus itself. However, virus replication machinery itself works well at both temperatures, leaving the question unanswered," Iwasaki said.
"We used mouse airway cells as a model to study this question [and found that] at the cooler temperature found in the nose, the host immune system was unable to induce defense signals to block virus replication," Iwasaki explained.
The researchers discuss their findings in the current issue of the Proceedings of the National Academy of Sciences.
To explore the potential relationship between internal body temperatures and the ability to fend off a virus, the research team incubated mouse cells in two different temperature settings. One group of cells was incubated at 37 C (99 F) to mimic the core temperature found in the lungs, and the other at 33 C (91 F) to mimic the temperature of the nose.
Then they watched how cells raised in each environment reacted following exposure to the rhinovirus.
The result? Fluctuations in internal body temperatures had no direct impact on the virus itself. Rather, it was the body's indirect immune response to the virus that differed, with a stronger response observed among the warmer lung cells and a weaker response observed among the colder nasal cells.
And how might outdoor temperatures affect this dynamic?
source : Researchers Probe Why Colds Are More Likely in Winter
