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Since the first cases of coronaviruses have been identified in December 2019 Wuhan, in China, researchers know that some people are more prone to catching the very contagious virus, are more likely to undergo serious infection, and are more likely to die at the after it, that others. For several months, they have tried to understand why it is the case. According to a new study, he might have to do with the fact that the immune system of some people have some familiarity with the pathogen - even if they have never been exposed.

Stimulate the immune system of cells play a role

In the study, published in the magazineNatureWednesday, researchers from Germany and the United Kingdom sampled 68 adults of health in Germany, none of which had ever been exposed to Coronavirus. However, more than a third of them - 35% - have T lymphocytes (immune cells that stimulate help protect your body from infection) that were reactive to the virus. This means that their immune system could have struggled against a similar infection - perhaps another type of coronavirus - and be able to use its memory to fight coronavirus. This is called "cross reactivity. They also analyzed 18 Covid-19 patient blood samples, 83% had to find T lymphocytes reacting to the virus.

"That was exactly what we had planned. The immune system in these patients was fighting against this new virus, and therefore showed the same in vitro reaction, "ExplainOne of the three main authors, Claudia Giesecke-Thiel, Ph.D., head of the study of the flow cytometry at the Max Planck Institute of Molecular Genetics.

"The fact that all patients with COVID-19 showed this auxiliary T lymphocytes response to viral fragments is probably due to the fact that T cells can not be activated outside the human body during acute or a particularly serious phase of a disease. »

Yet you could get infected

However, it is still unclear the impact that these cells may have on the overall result of a CIVID-19 infection.

"In general, the auxiliary T cells may have a protective effect, for example, by helping the speed of the immune system its production of antibodies against the new virus", explains the main co-author Leif Erik Sander, MD, the Medical Department of Charity, the Division of Infectious and Respiratory Diseases in Medicine.

"In this case, a recent cold fight would probably result in Covid-19 less severe symptoms. However, it is also possible that reactive cross immunity could lead to a poorly oriented immune response and the potentially negative effects on CVIV-19 clinical evolution. We know it can happen with dengue, for example. »