How Your Immune System Works

Every single day you are facing potential death. Cancer cells, harmful bacteria and viruses and other dangers could potentially kill you. Yet, several times a day, your life is saved by your innate army, an elite team of various specialised cells that are collectively called the immune system.

The gut

The vast majority of your immune system is located in the gut and for a good reason. The big parade of foreign invaders regularly takes place there and any cell that is serious about providing protective service must be there. The bacteria are confined to the gut mucus membrane of the gut. This allows the defender cells to poke around and get familiar with the unknown species without letting them too close to the cells of the gut wall and harming the body. If the immune cells later come across that same species somewhere else in the body, their reaction can be much quicker and more precise.

It is a fine balance to not suppress all the foreign cells and allow the necessary equilibrium of gut flora to exist. The immune system must be not only able to ‘greet’ every cell and identify whether it is a friend or foe, but also distinguish the bacteria from your own human cells, which is often much easier said than done. Many bacteria have developed structures on the surface that highly resemble the surface of your own cells.

Boot camp training

The cells of the immune system originate in the bone marrow, where many of them also mature. They then migrate to guard the peripheral tissues, circulating in the blood and in a specialized system of vessels called the lymphatic system.

But before they ‘graduate’ they must complete the toughest boot camp of any cells. Cells in training must cover vast distances while being confronted by various structures of the body. If a young cell cannot decide whether something belongs to the body or comes from outside it stops and pokes at it a little. This cell will never graduate into the bloodstream and is eliminated. This way, the cells that might incorrectly identify other cells are weeded out before they leave training.

One particularly tricky skill to acquire is to easily identify cells that aren’t bacteria but look very much like them, your red blood cells for example. They have a protein structure on their surface that is remarkably similar to bacteria. Your immune system cells would attack them if they didn’t learn in boot camp that the blood is a no-go area. This classification is the reason why it is important to receive a blood transfusion from the same blood group as you own. Since the immune system knows that bacteria have no business being in the bloodstream, it would recognise the donated blood as bacteria and consider it an enemy.

However, in newborn babies that don’t yet have many bacteria in the system, this differentiation hasn’t been formed and they can receive a blood transfusion from any blood group without the incompatibility effects. As a precaution, babies normally get blood transfusions from their own mothers.

The difference between the sexes

Generally, women have better immune systems than men because they have two X chromosomes, compared to XY chromosomes in men. Many genes that encode for the immune system are on the X chromosome. This is one of the reasons men die younger especially of cancer because the immune system is better able to kill off the immature cancer cells.

And yes, men-flu is a real thing! The single X chromosome encodes for only certain amounts of the immune system so men cop it much harder than women. However, a stronger immune system causes women to have more autoimmune diseases than men. The only time women’s immune system becomes weaker is when they are pregnant due to the spike in the hormone progesterone.

Rhinovirus and cold temperatures

Rhinovirus is another name for the common cold. The illness usually starts with a runny nose, sore throat, and sneezing and may go on to include headache, cough, and muscle aches.

You don’t miraculously catch the virus when you go out in the cold. You catch the virus somewhere else and it lives in your nose. Humans constantly live with many viruses that are kept in check by our immune system. When you breathe in the cold winter air, the temperature in your airways and your lungs temporarily drops, and this weakens the immune system. It is the change in temperature that causes that, not the cold weather itself. Thus constantly jumping from hot to cold in winter (or in summer with heavily air-conditioned spaces for that matter) will exacerbate the situation.

The immune system circulates in your blood. The temperature drop causes vasoconstriction (constriction of the blood vessels) which prevents the immune system from functioning properly and allows the virus to get a foothold. So if your immune system is not strong, you should take your mom’s advice and rug up to minimise the difference in temperature, and always breathe slowly and through your nose. Nose breathing will reduce the amount of airflow and warm up and moisturise it much better than breathing through your mouth. However, a strong immune system should be able to tolerate this change.

Stress

Exercise is one of the most potent tools to strengthen your immune system. However, rigorous exercise will leave you a bit vulnerable for a while during the recovery. For example, if you just finished a marathon, you don’t want to challenge your immune system but rather pamper yourself a bit and let the body recover for a day or two. This is due to stress. Stress always reduces the function of the immune system.

When we are stressed, our sympathetic branch of the autonomic nervous system (our fight or flight response) kicks in and cortisol levels go up. In history, this was a normal and healthy response that in the long term built us stronger as the stressful events were intense but short. It wasn’t a big deal if the immune system dropped for those few minutes. But staying in a state of chronic stress is really harmful.

When we are in this stressful state the body releases the stored sugars so it allows us to use that energy to run away from danger. If it needs to, the body even breaks down muscle tissue to form sugars.

Stress is a very subjective experience and there are many techniques to combat it in modern life. This is beyond the scope of this article. Let’s shine a spotlight on why the circulating sugar is bad for the immune system.

Glucose

We have heard so many times that eating sugar is bad for you, yeah yeah, boooring! But every time you have sugar, your immune system drops, and high amounts of glucose in your system have harmful effects on the immune system. So, when you feel ill, don’t go for your sweet comfort foods, they will exacerbate the situation. This entails a high carbohydrate diet as well. All carbs turn into the simple form of sugar - glucose, which then the body either uses or stores.

Vitamin C and glucose are very similar in structure and they fight for the same receptors in the cell. If you overload your system with sugar it will occupy all the immune system receptors but leave it inefficient. So while processed carbohydrates will definitely dampen your immune system response, eating a lot of fruits and vegetables that do contain sugar but also contain plenty of fibre and vitamin C will help fuel your immune system. Grains, for example, as healthy as they might be don’t contain much vitamin C, and will only be converted to sugar.

You don’t need that much vitamin C

Animals, like your dog or a cat, for example, don’t need fresh fruits or vegetables because they convert glucose into vitamin C in a very simple process. All mammals except humans, monkeys and guinea pigs have this ability, so we have to ingest it with food. This is why guinea pigs have been used for certain immune system research.

Now, if you have been told you need plenty of vitamin C for your immune system to amplify it you might have been misled. Your body can only utilise about 150-200 mg of vitamin C, which is a lot less than the 1,000 mg or more that some people tend to take. You can get the required amount from one orange a day.

Conclusion

The immune system is a complex network of organs, cells and proteins that defend the body against infection, whilst protecting the body's own cells. As the saying goes, ‘fix the roof while it’s sunny’, you don’t want to wait until you’re sick to start working on strengthening your immune system.

It is your daily lifestyle choices that will enable it to be strong and ready. Exercise, sleep and a good diet are the most potent factors. Only after they have been prioritised you should think about adding supplements if needed.

Surprising to many, when considering the most effective compounds you can take to improve your immune system, vitamin C is not one of them. In the next week’s article, we will explore what they are.

Resources:

https://www.youtube.com/watch?v=Ak6kSiSosn4

https://www.ncbi.nlm.nih.gov/books/NBK27092/

Gut by Dr Giuilia Enders