THE ESSENTIAL
- Some people who have never been exposed to SARS-CoV-2 have T lymphocytes, white blood cells that are responsible for cellular immunity, which can slow the epidemic.
- This explains why some people develop a severe form of the infection while others only have a mild form.
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The question of immunity around Covid-19 continues to be the subject of much research. A study published on August 4 in the journal Science by researchers from the La Jolla Institute of Immunology in California (United States) reveals that past exposure to colds has allowed many people to develop an immune system capable of recognizing Covid-19. “This could help explain why some people with Covid-19 have few symptoms while others get seriously ill”, Estimates Daniela Weiskopf, co-author of the study.
Good immune memory
Some people who have never been exposed to SARS-CoV-2 have T lymphocytes, white blood cells that are responsible for cellular immunity, which can slow the epidemic. “We have shown that, in some people, pre-existing T-cell memory for common colds can recognize SARS-CoV-2, right down to the exact molecular structures”, note Daniela Weiskopf.
This theory of cross immunity has already been studied previously and German researchers have shown that immune cells, developed after a simple cold, activate on contact with the coronavirus. This immune response would be long-lasting, compared to the antibodies that are developed by the body after a first infection with Covid-19 and which do not seem to last over time.
T lymphocytes, the key
This immune memory could explain why some people develop serious infections with Covid-19 when others have milder forms. It is possible that this “Immune reactivity results in varying degrees of protection against Covid-19, said the study’s other co-lead author Alessandro Sette. Further research is needed to confirm it. Having a strong T cell response, or better T cell response may give you the opportunity to have a much faster and stronger response. ” The exact role of T lymphocytes against Covid-19 must be clarified.
In this study, the researchers analyzed blood samples taken from people between 2015 and 2018. In these samples, T cells reacted at more than 100 specific sites on SARS-CoV-2. Researchers have shown that these T cells also respond to similar sites on four different coronaviruses that cause cold infections. ”This study provides very strong direct molecular evidence that T cells can see sequences that are very similar between common cold coronaviruses and SARS-CoV-2”, Added Alessandro Sette.
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