How Does Covid-19 Affect Your Immune System?

Experts explain what you can do to give your immune system a helping hand.

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As we’ve learned more about coronavirus, we’ve also become aware of the many ways it can impact the human body – not only can it harm the lungs, but also the heart, the kidneys, the liver. It can cause digestive issues, increase the risk of blood clots. Some end up with skin rashes, others suffer relentless fatigue. And then there are those who didn’t even know they had it.

While we still don’t fully understand all the ways in which coronavirus interacts with our immune system – and why the immune system tends to go into overdrive in some cases, causing even greater problems – we can run through the basics in terms of how the body reacts to the virus when exposed.

How does your immune system fight Covid-19?

When Covid-19 enters the body, it attaches to our cells, hijacks them, and then creates copies of itself to invade even more cells. Our immune system kicks in to try and stop this. First up, it sends out its frontline defence – the ‘innate immune response’ – to deal with the intruder.

This is the default response to any virus entering the body. As part of this initial response, inflammatory proteins called “interferons” are released, which have antiviral functions. The aim is to stop the virus in its tracks – though we don’t actually know how well this first response works in fending off infection.

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The issue with Covid-19, which scientists are still learning about, is that it is proving to be quite sneaky. In a meeting of the government’s Science and Technology Committee, Professor Sir John Bell, Regius Professor of Medicine at University of Oxford, explained that coronavirus can go undetected by our body’s ‘innate’ immune response.

“They are quite cunning, these little guys,” he said of the virus. “They actually have a system for avoiding the interferon response and that means that the innate immune response is, from the beginning, rather disabled.”

While the innate immune system is trying (and sometimes failing) to fight off the virus, it also ‘talks’ to the more specific ‘adaptive’ immune response. This is your body’s tailor-made solution for dealing with Covid-19, and involves the release of B-cells, which produce antibodies, as well as T-cells, which kill infected cells. This can take a week to kick in.

In most people, the adaptive immune response does the trick. But in a small group, their condition will deteriorate and they will require hospitalisation. By this point, the virus may have wreaked havoc on the lungs. It’s at this fragile stage that the body’s immune system can also go into complete overdrive.

“For some reason the natural brakes of our immune system fail and the inflammatory reaction overshoots,” explains immunologist Dr Jenna Macciochi. When this happens, high levels of cytokine (chemical signalling molecules) are released, which usually tell the body to activate inflammation to try and contain the virus.

But the high levels can result in something called a “cytokine storm” – where inflammation occurs and fluid builds up in the body, and the immune system is attacking healthy tissues. This can result in blocked airways, overwhelmed organs, and can potentially lead to multi-organ failure and death.

As Professor Daniel Altmann, from the Department of Medicine at Imperial College London, explains: “It’s not so much a matter of some people are damaged by virus versus others damaged by excessive immunity – more a horrible cocktail of many elements.”

So, how can we boost our immune system?

Experts are now trying to figure out whether they can prevent a patient’s immune system from overreacting at this crucial point. There is also a focus on treatments which reduce inflammation, including dexamethasone, a cheap anti-inflammatory steroid which has been found to reduce deaths from the virus.

Experts caution against the claims of any wonder supplements. “Most immunologists would not necessarily adhere to some of the health food industry claims that there are supplements to enhance immunity,” says Prof Altmann.

“Healthy people with good nutrition tend to have a healthy, functioning immune system, and unhealthy people with poor nutrition tend to have a less functioning immune system,” he tells Huffpost UK.

“One aspect of this of relevance here is that people with high BMI do less well with Covid-19, and obesity is known to raise the set-point of pro-inflammatory immune responses which may contribute to enhanced disease.”

Dr Macciochi advises people to adopt a healthier lifestyle if they do want to help their immune system. “It’s all about the small, long term habits,” she says.

“Be a regular exerciser, eat a diverse plant-rich diet with lots of fibre and phytonutrients, and get adequate protein and healthy fats. Don’t over or under consume calories, make sure to get enough sleep (both quality and quantity is important), and don’t overuse antibiotics.”