Off to the dirt!

There is no denying it: We live in a world where we are constantly exposed to viruses, bacteria, fungi and parasites. Many of them are unable to harm us, while others cause considerable damage if they enter our bodies and multiply there. Our immune system has the task of protecting us from potentially pathogenic germs. At the same time, however, and this is a particular challenge, it must regulate itself and keep itself in balance. And it has to do this in such a way that the defence function, which is intended against external intruders, is not also directed against our own cells. A third function of the immune system is to eliminate the body's own cells that are old or malignant.

«Many parts of our body are constantly busy protecting us, so much so that we are not even aware of it,» says Jana Pachlopnik Schmid, Assistant Professor of Paediatric Immunology at the Children's Hospital Zurich. We usually notice that our immune system is working when there are problems: Inflammation, for example, is a clear signal that our body is trying to fight something at the site where it occurs.

A complex system

Because our immune system consists of several organs and cell systems, it is highly complex. «Each part of the entire structure has its own very specialised task,» says Pachlopnik. Mucous membranes, for example, bind foreign bodies and transport them away. In the blood, it is mainly antibodies and white blood cells - including granulocytes and lymphocytes - that defend against the enemy.

A subgroup of lymphocytes plays an important role in the defence against viruses. «It is important that each component functions well on its own, but also fulfils its role in the larger system,» says Pachlopnik. A disruption at one level can quickly cause the whole system to falter.

When your little one starts nursery, a cold is suddenly part of everyday life. Fortunately, because this is how the immune system trains itself.

If a component does not function from birth, doctors refer to it as a congenital immunodeficiency. There are more than 400 different such defects, «but they are very rare,» says Pachlopnik, «about one in 10,000 newborns suffers from them.» In the vast majority of children, the immune system is intact when they are born. However, it is somewhat immature. This is because it has two different mechanisms: the so-called innate and the so-called adaptive immune defence. The innate part of the immune system is designed to quickly recognise and attack foreign substances and organisms. It is very efficient and reacts after just a few minutes. The intruder is eliminated after a few hours at the latest. The innate immune defence functions for a lifetime and automatically intercepts the majority of infections. It is a kind of life insurance, without which we would quickly get into trouble.

The trained immune defence

The adaptive immune defence, on the other hand, only develops in the course of our lives as our immune system learns. It categorises all germs that somehow find their way to and into our body: are they harmless? Or do we need to react urgently? Learning works in two ways: through vaccinations and through surviving infections. Parents experience this particularly when their children start nursery and the number of germs that their son or daughter comes into contact with increases dramatically: Suddenly, the common cold is part of everyday life. Fortunately, because this is how the immune system trains itself. «We observe that children who go to daycare earlier have significantly fewer infections later at school than those who have been kept at home for longer,» says Pachlopnik. Special hygiene measures such as disinfecting toys are unnecessary. «A child with a healthy immune system can and should also play in the dirt,» says Pachlopnik. A young body has to deal with every foreign pathogen that arrives. The more familiar the pathogen is, the easier this is. «Vaccinations are therefore one of the most important preventative measures,» says Volker Schuster, Head of the University Polyclinic for Paediatrics and Adolescent Medicine in Leipzig. «They train the child's immune system in case it comes into contact with these germs later on.» The course of the disease is then milder or even completely symptom-free.

It all starts with nest protection

Like humans, the immune system develops. In the first six months after birth, we benefit from antibodies given to us by our mother, which create what is known as nest protection. Their number gradually decreases as the newborn's immune system ramps up its own production of antibodies and begins to learn.

«As we get older, this mechanism slowly depletes,» explains Schuster. «This means that we suddenly become more susceptible again in areas where we were previously protected and infections can occur more frequently.»

This fatigue is also one reason why cancer occurs more frequently in old age: the immune system is less fit and finds it increasingly difficult to locate and destroy all malignant cells. This is why doctors are considering, for example, re-vaccinating older people and refreshing vaccinations that they received as children or young adults.

Hygiene measures such as sanitising toys are unnecessary. «A child can and should also play in the dirt,» says immunologist Jana Pachlopnik.

A healthy immune system must be in balance in order to function. This constant balancing of all those involved is difficult and makes it susceptible to external changes. Which is smart, because only then can it react quickly enough to its environment.

«If you want to strengthen your immune system, you should therefore do so carefully and with common sense, always bearing in mind that you are intervening in a network that should not be thrown out of balance,» says Pachlopnik.

A balanced diet, sufficient sleep

Within these limits, the immune system can certainly benefit. The most important thing is a regular lifestyle. «The immune system works cyclically, and the more regular this cycle is, the better it can function,» explains Pachlopnik. A regular sleep pattern is therefore particularly important, even for schoolchildren. A balanced diet is necessary so that the immune system can access all the nutrients it needs for the various processes. Vaccinations protect against potentially life-threatening illnesses and plenty of exercise in the fresh air ensures that the body can produce vitamin D, which is important for the immune system.

The following applies to young people in particular: smoking, alcohol and drugs weaken the immune system. It has to take care of eliminating the toxins it has absorbed and is therefore unable to fulfil its actual task. «In addition, the toxins can destroy cells in the mucous membrane and cause excessive inflammation, while at the same time hindering the defence against viruses by white blood cells,» says Pachlopnik. The good news is that because our immune system is so flexible, it recovers even if we treat it rather neglectfully for a while.

Is that still normal?

Your child seems to have one infection after another and you ask yourself: How much sickness is still normal? When should I start to worry? Doctors use certain standard values to assess the state of a child's immune system. For example, ten to twelve respiratory infections per year are considered «normal» up to the 1st grade. By comparison, the figure for adults is four. Indications of excessive susceptibility to infections, which could be caused by a defect in the immune system, can be: more than two cases of pneumonia per year, more than eight middle ear infections per year or more than two severe sinus infections per year. If you have the feeling that your child is constantly ill, talk to your paediatrician about it. He will help you to categorise and clarify this.

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