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Virus vs You - Your immune system and how SARS-CoV-2 works.

Updated: Jan 10

Episode 1 - part 1

This pandemic we're all experiencing has probably made you more aware of viruses and your immune system, but there are still a lot of questions you've been asking, such as: How does this virus infect my body? What does my body do to help fight it? Why are the elderly and those suffering from obesity at a higher risk of developing serious complications? In this video I’m going to give you a little insight into the general workings of your immune system and what we currently know about how this virus works.

So, how does the virus infect you? Well, Your respiratory airways are exposed to the outside, through your mouth, nose and eyes, so this makes it easy for respiratory viruses to enter your body. Once inside your nose, mouth or eyes, the virus encounters mucous which normally acts as a barrier against infections. But we've learned that this virus attaches to a specific protein on the surface of some cells in your airway. The problem is, that your lungs have even higher amounts of this protein which makes it the hotspot for this virus. This is different to the way the virus that causes the common cold works, as it tends to stay in your throat. Now, let's get back to the SARS-CoV-2 virus... so when this virus travels from your nose, mouth or eyes to your throat, it attaches to these specific proteins so it can enter the cells. Once it is inside, the virus hijacks the cell’s machinery so it can make millions of copies of itself. The virus then tries to kill the cell, which then ruptures and releases all the virus clones. Their mission? To invade even more of your cells.

Most infected people will experience symptoms 5-14 days after they catch the virus. These symptoms will be similar to those caused by the common cold virus like a sore throat, cough and fever. But, because this virus can travel further down your airways, a minority of people may develop inflamed lungs, which makes it hard for them to breathe, and this can develop into pneumonia. About a week after these symptoms, some of these people may go on to develop shortness of breath, followed by acute respiratory distress syndrome – this is when they need a ventilator to help them breathe.

What does your immune system do to try to eradicate this virus? Well, A specific set of cells drives your immune system’s response to a viral infection: we call them T-cells. The T stands for thymus. This is a small organ that sits behind your breastbone and in front of your heart. Most of your T-cells were created by your bone marrow when you were an infant, but the thymus is the central hub where T-cells come to mature into one of three types of T-cells: Killer, Helper or Regulatory T-cells. Once they’ve matured, they are released into your bloodstream where they keep an eye out for cells infected with the virus. Each Killer T-cell is only able to detect one kind of virus, so you can imagine the tens of millions of different specialised Killer T-cells you have to be able to fight a crazy number of different viruses! A cell that is infected with a virus will attempt to take a piece of this virus and transport it to the surface of the cell – so it’s like the cell is now tagged with a piece of the virus. If a Killer T-cell matches with this specific virus then it is able to detect this infected cell and kill it to stop the virus from spreading to other cells. To help win the fight, the Killer T-cell can make many copies of itself to create an army. Your immune system also memorises this virus so that your body can react faster and even more efficiently if you become infected a second time.

Episode 1 - part 2

Why are the elderly and obese more vulnerable to a viral infection? The thymus begins to shrink once you turn 20 years old and becomes a fraction of its original size when you hit 80 years old. So, although you are immune to the majority of viruses thanks to the repertoire of Killer T-cells you have developed, you become more susceptible to these infections. You are less efficient at mounting a response because your thymus isn't producing as many mature T-cells. This is especially an issue when you are exposed to a virus you have never been exposed to before. What doesn't help either is that ageing in general is also associated with more systemic inflammation, even when you are free of infection. This natural decline in your immune system can be worsened by lifestyle factors relating to nutrition, hydration, exercise and sleep. And it seems that being overweight or suffering from obesity is a predictor of reacting poorly to this virus - Three quarters of those in intensive care units are overweight or obese. This is down to numerous reasons. Firstly, you’re less able to breathe properly because of the extra weight you’re carrying. Since this is a respiratory virus, this increases your risk of respiratory failure. Secondly, by being overweight you’re already at a higher risk of suffering from hypertension, cardiovascular disease and diabetes - all of which come with a dysfunctional immune system, chronic low-level inflammation and an increased risk of forming blood clots. In one of my next videos I’ll be diving a little more into how this virus can also directly facilitate the formation of blood clots, and how the mere fact of being in intensive care contributes to this too. If a clot travels to your lungs, it can block the blood supply to them, and this can be fatal. If the clot travels towards your brain, then this can cause strokes. But there is a third reason, and it’s directly related to how the virus behaves. Fat, or what we call adipose tissue, can act as a reservoir for the virus. In this hideout, the virus is able to spread more easily by infecting more cells and increasing inflammation above and beyond what our body is capable of controlling, and this can also be fatal.

So, what does this all mean? Well, many of us are vulnerable – so the best thing we can do right now is to keep our physical distance, wash our hands and – well, you all know the drill by now. But, this is why it is so important for us to help support our immune system, especially now that lockdown is easing in most countries and we have to try our best to avoid a second or even third peak in infection rates. You can’t boost the function of your immune system (only vaccines do that), but you can support its normal function. In my next video I’ll dive into how we can do this with nutrition. But, until then, stay sane and sanitised! Written by Dr Elisabeth Thubron - Head of Science & Research

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