Some people have a stronger immune system due to their sex, genetics and previous exposure to pathogens David Garcia/Shutterstock
WE ALL know that person. The one who rarely gets ill. The covid-19 pandemic highlighted that when it comes to catching circulating viruses and bacteria, we aren’t all equal: some people can resist being infected by a pathogen even after heavy exposure. Finding out why could help keep the rest of us in better health.
A person may resist an illness because they have recently been exposed to the pathogen that causes it and their body knows how to fight it off. This wasn’t the case for covid-19, as no one had encountered the coronavirus behind it before the end of 2019. Some people did seem to have some resistance to it, though, due to past infections with other, similar viruses – there are at least four coronaviruses that cause ordinary colds. In 2021, a few healthcare workers who had never tested positive for covid-19 despite heavy exposure were found to have had “abortive infections”, when the virus briefly replicates inside the nose and airway before being wiped out. Their immune systems were found to as well as the cold-causing coronaviruses.
People may have resistance to infections because of their genetic make-up. For covid-19, this has been investigated in relation to people’s risk of dying from or needing respiratory support due to their infection. Earlier this year, Johnathan Cooper-Knock at the University of Sheffield, UK, and his colleagues found more than 1300 genetic variants that are responsible for raising or decreasing an individual’s risk of developing severe covid-19. Most affected the function of two types of immune cell: T-cells and natural killer cells.
This article is part of a special series on immunity, in which we explore:
The same gene variants may explain why some people avoid catching it at all, says Cooper-Knock. But now that most people have been vaccinated against covid-19, factors that affect how well people respond to those vaccines may be more important, he says.
Genetic variation
Other genes may be involved in our susceptibility to different pathogens. About 1 in 100 people with European ancestry are unlikely to be infected by HIV because of a genetic variant they have, which also affects T-cells. Another gene variant that affects a different kind of immune cell called a macrophage may alter the likelihood of developing tuberculosis, according to a .
Given their benefits, why doesn’t everyone have immune-boosting genes? The reason is that many genetic variants can have both beneficial and harmful effects. For instance, one gene variant became more common in the British population during the Middle Ages, probably because it boosted the immune response to the bacterium that caused the Black Death. But last year, it was discovered that this . As with other autoimmune conditions, this is caused by the immune system mistakenly attacking the cells of our own body – in this case, the cells lining the gut.
Take this as a warning that while it may seem a good thing to try to supercharge the immune system, it is really balance that matters when it comes to providing the greatest overall protection.
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