Severe cases of Covid-19 are linked to an aging immune system, says Fiocruz

Severe cases of Covid-19 can be caused by an aging immune system. One study analyzed blood samples from hospitalized patients with the disease and found exhaustion and aging in defense cells.

The research was conducted by the Oswaldo Cruz Institute (IOC/Fiocruz) and by the Federal University of Rio de Janeiro (UFRJ). Scientists say that the data collected show a loss of responsiveness of defense cells known as T lymphocytes in cases of severe Covid-19, which could facilitate secondary infections and reinfections.


“In patients with severe Covid-19, we observed that CD4 T lymphocytes [auxiliares] they are in the final stages of differentiation, showing markers of exhaustion and senescence in the immune system. These are cells that have lost their capacity for clonal expansion, that is, they will not multiply when they come into contact with viral proteins and will not be able to command an efficient immune response”, says the immunologist”, says the researcher at the Instituto Oswaldo Cruz e Professor at the Faculty of Medicine at UFRJ, Alexandre Morrot, leader of the study.

aged immune system

According to research data, the picture of the aging of the immune system can be characterized as acute immunodeficiency. This makes the body more vulnerable to other infections, such as pneumonia, which aggravates Covid-19 cases. This could also explain reinfections.

“Reinfection occurs in a small fraction of cases, but it is more common than would be expected. CD4 T cell dysfunction [auxiliares] may explain the lack of long-term immunological memory in severe Covid-19,” adds Morrot.

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The Fiocruz study analyzed 22 patients hospitalized with Covid-19. They compared samples with those from healthy people and measured the degree of exhaustion of T lymphocytes, which undergo a process of inflammation. “All this reinforces the importance of anti-inflammatory therapies, aimed at controlling the exaggerated immune response, which is a villain at Covid-19”, completes the head of the research.

“Covid-19 is still a new disease and we don’t know how it will evolve. Scientific literature indicates that depleted cells can regain their function. Senescent cells can die and be replaced by young cells. It is possible that a few months after the disease, the patients no longer present these changes, but this will have to be monitored”, he concludes.

Via Fiocruz Agency

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