Covid symptoms: A person’s T cells determine whether they suffer mild or severe symptoms


The vast majority of confirmed COVID-19 cases are considered mild, involving mostly cold-like symptoms to mild pneumonia, according to data. Researchers used blood samples to investigate the cause as to why some suffer with more severe symptoms than others in the hopes they can better predict which people are more likely to develop the most severe symptoms from the novel virus.

A new study has found why some people experience milder COVID-19 symptoms compared to others.

Scientists have uncovered the cause for this relating to T cells which “remember” previous encounters with seasonal coronaviruses.

For this, cells are better equipped to mobilise quicker to help protect the body against a COVID-19 infection.

The study found that the killer T cells which were taken from the COVID-19 patients who exhibited worse symptoms in fact exhibited fewer signs of having had previous run-ins with common cold-causing COVID-19.

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The findings may help explain why some individuals, particularly children, seem much more resilient than others when it comes to COVID-19 infection.

It may also help to better predict which people are more likely to develop the most severe symptoms from the novel virus.

The immune system has myriad of ways to fend off viral invaders and keep them from returning.

T cells patrol the body seeking out and destroying infected cells, to disrupt the virus’s ability to replicate. These immune cells can also endure for years.

Antibodies are easily fooled, said senior author Dr Mark Davis, a professor of microbiology and immunology at Stanford University and a Howard Hughes Medical Institute investigator.

He added: “Pathogens evolve quickly and ‘learn’ to hide their critical features from our antibodies.

“But T cells recognize pathogens in a different way, and they’re tough to fool.”

Antibody responses tended to be highest in people with the most severe infection.

Those with mild infections were found to produce small amounts of neutralising antibody.

This pattern is often seen with viruses: the longer, more severe infections are more likely to produce strong, durable responses, added Shane Crotty, a virologist at the La Jolla Institute for Immunology in California.

“This is one reason that common-cold coronaviruses sometimes don’t yield long-lasting immunity.”



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