According to a study published on Tuesday, some people who have never been exposed to the new coronovirus may still have T cells that react to it. Scientists think this is because those cells first learned how to recognize and fight cornviruses that cause the common cold.
A type of white blood cell, T cells are an important part of the body’s defense against the virus: they recognize and destroy infected cells, while also exposing B cells to the craft of new antibodies. When you are infected, your immune system produces both antibodies and these white blood cells.
Antibody levels may drop in the months following an infection, but memory T cells cling on for years and can help mount another attack that should send the same virus back.
Recent research suggests that T cells that miss how to fight other coronaviruses may give people an immunological start against the new coronovirus.
“It may help explain why some people show signs of the disease while others become seriously ill,” Alessandro Sete, a co-author of the new study, said in a press release. He cautioned, however, that it is too soon to explain whether preexisting immunologist affects the outcomes of COVID-19 patients.
Some T cells recognize new coronoviruses before they are seen.
Sette’s team analyzed blood samples collected from 25 people between 2015 and 2018, which, of course, was never COVID-19. They found that those unpublished individuals had memory T cells that could recognize both new coronaviruses and four types of common cold coronaviruses.
Those findings, built on research Sette published in May, described 10 people who had never been exposed to new coronoviruses, yet were able to identify helper T cells and respond to them.
He also performed a large analysis of data from cohorts in the US, the Netherlands, Germany, Singapore and the UK and concluded that 20 percent to 50 percent of unexposed white blood cells react significantly to new coronoviruses.
“Permanent immune responses exist to some extent in the general population,” Sette wrote in the analysis.
Two other recent studies provide even more evidence for this conclusion.
The first, published last month, found that among 68 healthy German people who never had COVID-19, more than one-third of T cells responded to the virus. Second, published in the journal Nature, Found that more than half of a group of 37 healthy people who had never received COVID-19 were memory T cells that could recognize the new coronovirus.
Nature The study also examined 23 people who survived SARS – which is also a coronovirus – and found that they still had SARS-specific memory T cells 17 years after becoming ill. The same T cells can also recognize new coronoviruses.
People with cross-reactive T cells can rapidly mount an immune response
The most likely explanation for these observations is a phenomenon known as cross-reactivity: T cells that develop in response to a virus react to a similar, but previously unknown, pathogen.
He can give the immune system a leg up.
“You’re starting out with a small advantage – the arms race among the viruses starts with a head that wants to breed and to wipe out the immune system,” Sette quoted Business Insider.
In the absence of cross-reactive T cells, your body has to mount its defenses from scratch – which can affect how fast your immune system can react to the invading virus. The level of set-reactivity can vary so “translate to different degrees of safety,” Sette said.
“Having a stronger T cell response, or a better T cell response can give you the opportunity to mount a much faster and stronger response,” he said.
This article was originally published by Business Insider.
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