A study, published in Science Immunology , revealed that a type of anti-bacterial T cell, mucosa-associated invariant T cells (MAIT cells), are strongly activated in patients with moderate to severe coronavirus disease.

According to the researchers at Karolinska Institutet, Sweden, the findings would help in better understanding the response of the immune system with respect to coronavirus.

The study’s corresponding author, Professor Johan Sandberg, said in a statement: “To find potential treatments against Covid-19, it is important to understand in detail how our immune system reacts and, in some cases, perhaps contribute to worsening the disease.”

Methodology

For the study, the team of researchers examined the presence and character of MAIT cells in blood samples from 24 patients admitted to Karolinska University Hospital with moderate to severe Covid-19.

They then compared the blood samples with the samples taken from 14 healthy controls and 45 individuals who had recovered from Covid-19.

The team wanted to explore the role MAIT cells play in Covid-19 disease pathogenesis.

Results

The results revealed that the number of MAIT cells in the blood declined sharply in patients with moderate or severe Covid-19. While the remaining cells in circulation were highly activated, suggesting their engagement in the immune response against SARS-CoV-2.

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Researchers stated that the pattern of reduced number and activation in the blood is stronger for MAIT cells than for other T cells.

The researchers also noted that pro-inflammatory MAIT cells accumulated in the airways of Covid-19 patients to a larger degree than in healthy people.

“Taken together, these analyses indicate that the reduced number of MAIT cells in the blood of Covid-19 patients is at least partly due to increased accumulation in the airways,” said Sandberg.

Researchers also said that In the patients who died of Covid-19 had extremely activated MAIT cells with lower expression of the receptor CXCR3 than in those who survived.

“The findings of our study show that the MAIT cells are highly engaged in the immunological response against Covid-19,” said Sandberg.

“A likely interpretation is that the characteristics of MAIT cells make them engaged early on in both the systemic immune response and in the local immune response in the airways to which they are recruited from the blood by inflammatory signals. There, they are likely to contribute to the fast, innate immune response against the virus,” authors of the study added.

In some people with Covid-19, the activation of MAIT cells becomes excessive and this correlates with severe disease, the study noted.

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