THE ESSENTIAL
- As of May 4, 2022, more than 53 million people were fully vaccinated against Covid-19 in France.
- Currently, the incidence rate is 450.47 cases per 100,000 population.
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Ebetween the 1is January 2020 and December 31, 2021, there were 14.9 million deaths linked to Covid-19 according to the latest figures published by l’World Health Organization May 5th. But why do some die of this disease when others are asymptomatic or have only mild symptoms? This is the question that researchers from Boston University, in the United States, wanted to answer. Their work has been published in the journal Cell Reports.
Macrophages with a hyper-inflammatory response
According to scientists, the answer comes from macrophages. These are cells that belong to the family of white blood cells. They play a role in the immune defense of the human body, in particular to heal wounds. In detail, they attack harmful foreign agents, bad bacteria or dead cells by destroying them. If this mode of defense usually helps humans stay healthy, it seems that this is not the case for Covid-19. The researchers discovered that in infected patients, macrophages had attacked the virus but also the organism of sick people, which had caused excessive inflammation and damaged heart and lung tissue. This is a hyper-inflammatory response of these macrophages.
More diverse immune systems resist better
To achieve this result, the researchers conducted their experiments on mice to which they transplanted lung tissue and a human immune system. Thus, they were able to determine that the rodents that were most severely affected by the disease had poorly diversified macrophages. In other words, the most present macrophage was pro-inflammatory. “They seem to drive this hyper-inflammatory responseexplains Devin Kenney, one of the authors. And this leads to a more serious disease state“In contrast, immune systems that had more diverse cells were more resistant to Covid-19 infection.
continue research
But how does this phenomenon occur? According to the researchers, there are eleven genes that define the immune protection that a patient will have. Whether or not they are present in the body also depends on the reaction of macrophages. “We now know that macrophages can help protect lung tissueexplains Florian Douam, one of the researchers. But we also know all the genes needed for macrophages to protect the lungs“. On the other hand, they still do not know why the immune system of certain patients may be more diversified at the macrophage level. They therefore intend to continue their work to discover it and perhaps, in the long term, be able to prevent severe forms of Covid-19. 19.
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