Can you really “catch a cold”?
Several known factors favor common respiratory infections in cold weather, such as indoor gatherings, which are more numerous than in summer, and the fact that viruses tolerate low temperatures better.
As to whether the cold actually weakens our immune system, there is less certainty.
However, American researchers have made a discovery that would support this thesis.
The study, published on December 6 in the Journal of Allergy and Clinical Immunology, explains that a biological mechanism used by our body to attack these intruders works best when it is hot.
It all starts with a previous study, conducted in 2018 by three of the co-authors of the one published yesterday.
They had discovered that when bacteria are inhaled, the cells of the nose detect them and release extracellular vesicles (EVs) in the nasal mucus which attack the microbes, like a swarm of hornets defending its nest against invaders.
Scientists then asked themselves two questions: can this cloud of tiny particles also repel viruses?
And if so, is its response affected by the outside temperature?
Read alsoThe cold, we wash our hands of it!
Nasal mucosa less protective
For their test, the researchers took nasal mucosa from volunteers and then analyzed how it reacted to three types of cold-causing viruses - two rhinoviruses and a (non-Covid) coronavirus.
Verdict: EVs are well produced against viruses.
In detail, these vesicles present viruses with "decoys" to which they cling, instead of the cell receptors they would normally have targeted.
The more decoys, the more EVs block the infection.
Furthermore, EVs also contain a microRNA with an antiviral effect.
To answer the second question, the researchers divided the nasal mucous membranes into two groups, with the cells cultured in the lab at either 37°C or 32°C.
These temperatures were chosen based on tests showing that the temperature inside the nose drops about 5°C when the outside air drops from 23°C to 4°C.
Under normal body temperature conditions, EVs were good at fighting viruses.
But with a reduced temperature, the production of vesicles was less abundant and they were less efficient.
The study authors now believe that their discovery could lead to the development of treatments for colds, and even the flu, by stimulating the natural production of EVs.
