Researchers found the secret behind why the common cold is most common in colder weather.
Past studies have found the common cold virus can reproduce more efficiently inside the cooler temperatures of the nose than it can at the body's core temperature, but these studies failed to look at how the human immune system responded to temperature changes, Yale University reported.
To gain insight into how the body responds to colder temperatures a team of researchers examined cells taken from the airways of mice and compared the immune response to the rhinovirus (common cold) when cells were incubated at 37 degrees Celsius (core body temperature) and at a cooler 33 degrees Celsius.
"We found that the innate immune response to the rhinovirus is impaired at the lower body temperature compared to the core body temperature," said Yale professor of immunobiology Akiko Iwasaki.
The observations suggest varying temperatures do have an influence on immune responses as opposed to the virus itself. The team noticed viral replication in airway cells from mice with genetic deficiencies in immune system sensors that detect invasive viruses. When these immune deficiencies were present the virus was able to replicate at higher temperatures.
"That proves it's not just virus intrinsic, but it's the host's response, that's the major contributor," Iwasaki said. "In general, the lower the temperature, it seems the lower the innate immune response to viruses."
In the future the researchers hope to apply these findings to other conditions such as asthma because the usually-harmless common cold can cause severe breathing problems in children suffering from this condition. Upcoming research could include investigations into immune responses to rhinovirus-induced asthma.
The study was published in a recent edition of the Proceedings of the National Academy of Sciences and was supported in part by the NIH/National Institute of Allergy and Infectious Diseases.
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