People who often have colds would be less likely to develop a severe form of Covid-19 because their immune system is in regular contact with other strains of the coronavirus, which makes it more effective.
- Immune cells would be more effective in defeating Covid-19 if they have already been in contact with other coronaviruses, especially those linked to the common cold.
- Thus, the immune cells would be faster to respond to the virus. A saving time for some patients.
Having a cold often could become good news! Researchers have just published a study in the journal Science Immunology (https://immunology.sciencemag.org/content/6/61/eabg5669) proving that people who often have colds are less likely to develop a severe form of Covid-19. The reason is simple: certain so-called “killer” cells – or also called T lymphocytes – in these patients’ immune systems remember previous encounters with the seasonal coronaviruses, responsible for around a quarter of common colds in children. Thus, the cells of the immune system already know how to fight against this type of virus and are therefore more effective against SARS-CoV-2.
T cells locate and record pathogens
To achieve this result, the researchers took T lymphocytes from patients with Covid-19. “Pathogens evolve rapidly and learn to hide their characteristics from our antibodies“, develops Mark Davis, one of the authors. In other words, the researchers excluded working on antibodies and concentrated on T lymphocytes, which they consider more interesting. Indeed, the latter do not have the way of spotting pathogens as antibodies and are therefore harder to fool.In detail, when our cells encounter a pathogen, they signal it by displaying a sample of it on their surface. T cells check the state of the cells, they immediately see the sample and activate the immune system to kill this pathogen. In parallel, so-called memory killer cells are also working to “register” the pathogen. The purpose of this archiving is that the immune system knows immediately how to fight the virus the next time it encounters it.
T cells more effective against SARS-CoV-2 in cold patients
Another step in the scientists’ research was to analyze blood samples taken from healthy donors before the pandemic began, meaning they had never encountered SARS-CoV-2. Thus, they discovered that the T cells of individuals who had never been exposed to SARS-CoV-2 were sometimes more effective than those of patients who had been in contact with SARS-CoV-2 but had not had a colds the previous months. The researchers believe that those who had never been exposed to SARS-CoV-2 had probably already encountered less severe strains of the coronavirus. The cells remembered this and were thus able to better adapt their response thanks to their experience. “Memory cells are by far the most active in the defense against infectious diseases, points out Mark Davis. To fight a pathogen, that’s what it takes. That’s what vaccines are supposed to do.“.
Faster action when T cells experience other coronaviruses
Immune system cells take several days to adapt their response when they first encounter a virus. “This lost time can make the difference between a patient who will be asymptomatic and one who will die of the disease.“, continues the researcher. On the other hand, the patients who react best to the virus are also those with the greatest number of T lymphocytes, which therefore act both against SARS-CoV-2 but also against other In contrast, in sick patients, T cells fought exclusively against SARS-CoV-2, meaning they had started from scratch to respond to the Covid-19 pathogen, so they lost time. “Patients with a severe form of Covid-19 may not have been infected, or at least not recently, with milder strains of coronavirus, so they may not have retained memory killer cells. effective“, concludes Mark Davis.
In France, 111,164 people have died from Covid-19 since the start of the epidemic.
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