Scientists who conducted a new study may have found a biological reason for many respiratory diseases in the winter, and the cold air itself affects the immune response in the nose. (Caroline Heyer, The Dreamer)
Estimated reading time: 5-6 minutes
WASHINGTON — A chill is in the air, and you all know what that means — it’s cold and flu season, when everyone you know is suddenly sneezing, coughing, or worse. It’s almost as if those pesky cold and flu germs have arrived with the first blast of winter weather.
However, germs are available year-round – think back to your late summer chill. So why do people get more colds, flu and now covid-19 when it’s cold outside?
In what researchers are calling a scientific breakthrough, scientists behind a new study have discovered a biological reason why we get more respiratory illnesses during the winter months. The cold air itself affects the immune response in the nose.
“This is the first time we have a biological and molecular explanation for one of our innate immune responses,” said rhinologist Dr. Zara Patel, professor of otolaryngology and head and neck surgery at Stanford. University of California School of Medicine. She did not participate in the new study.
In fact, lowering the temperature in the nose by 9 degrees Fahrenheit kills about 50% of the billions of virus- and bacteria-fighting cells in the nasal passages, according to a study published Tuesday in The Journal of Allergy and Clinical Immunology.
“Cold air is associated with viral infections,” said Dr. Benjamin Blair, director of otolaryngology at Massachusetts Eye and Ear and an associate professor of Harvard Medicine, School in Boston.
“It’s important to remember that these are in vitro studies, which means that although human tissue is being used in the lab to study this immune response, it’s not a study taking place in a person’s actual nose,” Patel said in an email. “Often the findings of in vitro studies are confirmed in vivo, but not always.”
Hornet’s nest
To understand why this happened, Blair and his team and co-author Mansour Ameji, chair of the Department of Pharmaceutical Sciences at Northeastern University in Boston, began scientific investigations.
A respiratory virus or bacteria invades the nose, the main point of entry into the body. Immediately, the front of the nose will find the germ, before knowing the intervention behind the nose, the team found.
At that point, the cells lining the nose begin to make billions of copies of themselves called extracellular vesicles, or EVs.
“EVs can’t divide like cells, but they’re like smaller versions of cells that are designed to go and kill these viruses,” Blair said. “EVs act as decoys, so now when you breathe in a virus, the virus sticks to these decoys instead of sticking to the cells.”
Those “mini me” cells stop invading germs before they can reach their destination and reproduce.
“This is one of the only immune systems your body has to fight bacteria and viruses before they enter your body,” Blair said.
Once formed and dispersed into the nasal fluid, billions of EVs then begin swarming the invading germs, Blair said.
“What happens if you hit a hornet’s nest? You see a few hornets flying around, but when you hit them, they all fly out of the nest to attack before the animal enters the nest,” he said. “That’s how the body cleans up these inhaled viruses so they never get into the cell in the first place.”
Great increase in immune power
During an attack, the nose increases cellular stem cells by 160%, according to the study. There were additional differences: EVs had more receptors on them than the original cells, thus enhancing the ability of the billions of intracellular vesicles in the nose to stop the virus.
“Think of the receptors as little arms, trying to catch virus particles when you inhale them,” Blair said. “And we found that each vesicle has up to 20 times more receptors on the surface, so they’re super sticky.”
Cells in the body also have a virus-killer called microRNA that attacks invading germs. However, the study found that EVs in the nose contained 13 times more microRNA sequences than normal cells.
So the nose comes into battle armed with some extra powers. But what happens to these benefits when cold weather hits?
To find out, Blair and his team exposed four study participants to 40-degree Fahrenheit temperatures for 15 minutes and then measured conditions in their nasal passages.
“What we found is that when you’re exposed to cold air, the temperature in your nose can drop by 9 degrees Fahrenheit. And that’s enough to destroy all three of the immune benefits of the nose,” Blair said. he said.
In fact, that little bit of cooling on the tip of the nose was enough to knock out about 42% of the intracellular vesicles, Blair said.
“At the same time, you have half of those killer microRNAs in each vesicle, and you can reduce the number of receptors on each vesicle by up to 70%, making them much less sticky,” he said.
What does that do to your ability to fight off colds, flu and covid-19? It cuts your immune system in half to fight off respiratory infections, says Blair.
You don’t have to wear nose socks
As it turns out, the pandemic gave us exactly what we needed to fight the cold weather and boost our immunity, Blair said.
“Not only do masks prevent you from breathing in viruses directly, but it’s like wearing a scarf over your nose,” he said.
Patel agrees: “The warmer you can keep the area inside the nose, the better this natural defense mechanism can work. Another reason to wear a mask!”
In the future, Blair expects to see the development of topical nasal medications that build on this scientific discovery. These new pharmaceuticals “primarily fool me into thinking I saw a virus in the nose,” he said.
“By having that exposure, you’re going to have all these extra snails flying around in your mucous membrane,” he added.
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