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There’s a chill in the air, and everyone knows what that means: It’s time for cold and flu season, when it seems like everyone you know is suddenly sneezing, whining, or worse. It’s almost as if those pesky cold and flu germs arrived with the first gust of winter weather.
However, the germs are present all year round; just think of your last summer cold. 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, the scientists behind a new study may have found the biological reason we have more respiratory illnesses in winter. It turns out that cold air itself damages the immune response that occurs in the nose.
“This is the first time that we have a biological and molecular explanation for a factor in our innate immune response that appears to be limited by colder temperatures,” said rhinologist Dr. Zara Patel, professor of otolaryngology and head and neck surgery. neck at Stanford. University of California School of Medicine. She was not involved in the new study.
In fact, lowering the temperature inside the nose by just 9 degrees Fahrenheit (5 degrees Celsius) kills nearly 50 percent 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 increased viral infection because you’ve essentially lost half your immunity just from that little drop in temperature,” said rhinologist Dr. Benjamin Bleier, director of translational otolaryngology research at Massachusetts Eye and Ear. and associate professor at Harvard Medical School in Boston.
“It’s important to remember that these are in vitro studies, which means that while human tissue is used in the lab to study this immune response, it’s not a study that takes place inside someone’s actual nose,” he said. Patel in an email. “Often, the findings of in vitro studies are confirmed in vivo, but not always.”
To understand why this occurs, Bleier and his team and co-author Mansoor Amiji, who chairs the department of pharmaceutical sciences at Northeastern University in Boston, has embarked on a manhunt for scientific detectives.
A respiratory virus or bacteria invades the nose, the main point of entry into the body. Immediately, the front of the nose detects the germ, long before the back of the nose notices the intruder, the team found.
At that point, the cells lining the nose immediately start creating billions of single copies of themselves called extracellular vesicles, or EVs.
“EVs can’t divide like cells do, but they are like little mini versions of cells designed specifically to kill these viruses,” Bleier said. “EVs act as decoys, so now when you inhale a virus, the virus attaches to these decoys instead of attaching to cells.”
Those “Mini Me” are then expelled by the cells into the nasal mucus (yes, snot), where they stop. invading germs before they can reach their destinations and multiply.
“This is one of the parts of the immune system, if not the only one, that leaves your body to fight bacteria and viruses before they enter your body,” Bleier said.
Once created and dispersed in nasal secretions, the billions of EVs begin to swarm the marauding germs, Bleier said.
“It’s like you kick a hornet’s nest, what happens? You might see a few hornets flying around, but when you kick it, they all fly out of the nest to attack before the animal can get into the nest,” she said. “That’s the way the body absorbs these inhaled viruses so they can never get into the cell in the first place.”
When under attack, the nose increases production of extracellular vesicles by 160%, the study found. There were additional differences: The EVs had many more receptors on their surface than the parent cells, increasing the virus-stopping ability of the billions of extracellular vesicles in the nose.
“Imagine the receptors as little arms sticking out, trying to grab the viral particles as you inhale them,” Bleier said. “And we found that each vesicle has up to 20 times more receptors on the surface, making them super sticky.”
The body’s cells also contain a viral killer called microRNA, which attacks invading germs. However, EVs in the nose contained 13 times more microRNA sequences than normal cells, the study found.
So the nose comes into battle armed with a few extra superpowers. But what happens to those advantages when the cold arrives?
To find out, Bleier and his team exposed four study participants to 15 minutes of temperatures of 40 degrees Fahrenheit (4.4 degrees Celsius) and then measured the conditions inside their nasal cavities.
“What we found is that when you are exposed to cold air, the temperature in your nose can drop as much as 9 degrees Fahrenheit. And that’s enough to essentially eliminate the three immunological advantages that the nose has,” Bleier said.
In fact, that little bit of coolness at the tip of the nose was enough to clear nearly 42% of the extracellular vesicles, Bleier said.
“Similarly, you have almost half the amount of those killer microRNAs inside each vesicle, and you can have up to a 70% drop in the number of receptors in each vesicle, making them much less sticky.” said.
What does that do to your ability to fight off colds, flu and covid-19? It halves the immune system’s ability to fight respiratory infections, Bleier said.
It turns out that the pandemic gave us exactly what we need to help combat cold air and keep our immunity high, Bleier said.
“Not only do masks, prrinologist Dr. Benjamin Bleiero, protect you from direct inhalation of viruses, but it’s also like wearing a sweater on your nose,” he said.
Patel agreed: “The warmer you can keep the intranasal environment, the better this innate immune defense mechanism can function. Perhaps yet another reason to wear masks!”
In the future, Bleier hopes to see the development of topical nasal medications that build on this scientific insight. These new pharmaceuticals will “basically trick your nose into thinking it just saw a virus,” she said.
“By having that exposure, you’ll have all these extra hornets flying around your mucus protecting you,” he added.
Source: news.google.com