Even at the beginning of the pandemic, scientists drew attention to the fact that patients with allergic asthma are significantly less susceptible to severe covid than the average population. Conversely, people with other respiratory diseases with active sputum production, such as chronic obstructive pulmonary disease or emphysema, are, on the contrary, very susceptible to severe covid.
Researchers from the University of North Carolina (USA), whose article published in the journal Proceedings of the National Academy of Sciences, are confident that they have solved this mystery. Scientists conducted a series of laboratory experiments, infecting human respiratory tract epithelium cells with the SARS-CoV-2 virus and observing what then happens at the cellular level.
Among other things, the researchers found that the MUC5AC protein plays a key role in the fight against invading coronavirus cells. Previously, it was found that in patients with asthma, when exposed to allergens overproduction of this protein in the cells of the mucous membrane of the respiratory tract begins. Moreover, this process is triggered by the cytokine IL-13, one of the molecules produced in the body in response to the invasion of pathogens in order to organize immune protection against them. In allergic asthma, the body mistakenly perceives allergens as pathogens: dust, pollen, mold, dandruff – and directs the immune system to fight them.
Scientists have suggested that IL-13 is not only responsible for the development of an allergic reaction in asthma, but also protects cells from the SARS-CoV-2 virus by stimulating the production of the MUC5AC protein.
The researchers tested this hypothesis by adding IL-13 to infected cells. As a result, there were fewer infected cells, and the number of viral particles in the remaining ones dropped sharply.
As a result, it was found that IL-13 prevents the penetration of the virus into cells, the reproduction of the virus inside the cells and the spread of the virus throughout the body, limiting its ability to reach the lungs and cause a severe infection. It is this phenomenon, the researchers believe, that explains the fact that patients with allergic asthma are protected from severe covid.
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