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The immune system

Christian P.
Gesundheits - Redakteur

Lesezeit 2 Minuten
Bildquelle: Shutterstock

What is the immune system?

The immune system is the human defense system against foreign substances and germs. Since the human body is an open system that is in constant exchange with the environment, our organism has a complex, multi-membered system for protection against unwanted intruders. Whether bacteria, fungi, viruses or pollutants from the air or in our food, all of these things can pose a threat to the body. Thanks to our immune system, most of these threats cause mild discomfort at most, but they can also become life-threatening, especially if our immune system is weakened.

But how does this complex apparatus actually work?

Even before the inner parts of our immune system come into play, the skin and mucous membranes form a barrier against external invaders. The real work begins when a pathogen or pollutant breaks through this protection, e.g. through skin injuries.

Nonspecific immune defense

The first line of defense is the non-specific immune defense. It is already present since birth and is therefore also called natural or innate immune system. Its great strength is the speed with which it can react to foreign substances. However, as the name suggests, this defense is very non-specific,it can hardly distinguish between different invaders and is often limited in its ability to prevent the spread of some pathogens in the body.


Components of the non-specific immune defense:

  • Skin and mucous membranes
  • Body fluids (e.g. saliva, mucus, urine, gastric acid)
  • local protective mechanisms (e.g. cilia of the bronchial tubes)
  • natural flora (e.g. bacteria on the skin or in the intestine)
  • Defense cells (e.g. monocytes, natural killer cells)
  • specific proteins


Specific immune defense

Since the nonspecific immune defense alone is often not sufficient to defend against an attack, the adaptive or acquired immune system is needed. It can be much more targeted against specific enemies in the body, but often takes hours or days to develop sufficient punch. That is why it also forms the so-called immune memory. If infection with the same pathogen occurs again, it can react more quickly. A central mechanism of this immune memory is the antigen-presenting cells. These cells virtually “present” parts of the structure of a pathogen on their surface. In this way, the immune system learns to distinguish these invaders from the body’s own structures

Other central components of the specific immune defense are:

  • T-cells
  • B-cells



When antigen-presenting cells present foreign structures on their surface, it is the T cells that memorize these structures to quickly recognize invaders. But even these cells are not infallible.

To prevent them from recognizing the body’s own antigens and thus being activated, T cells undergo negative selection in which cells that react incorrectly are destroyed. This is supposed to prevent autoimmune diseases. There are different types of T-cells. For example, there are T cells that can recognize and kill the body’s own cells that have been infected by viruses. Others activate B cells, which then produce antibodies. They are called T-cells because they mature in the thymus.



B-cells are able to recognize and bind foreign substances. If there is additional activation by the T cells, they begin to produce large amounts of antibodies. These special proteins “block” pathogens by binding to them and thus preventing them from exerting their toxic effect, or they “mark” them to make them easier for the immune system to recognize. The name B-cells originally comes from their site of formation in the buras fabriciiin birds. In humans and other mammals, B cells are produced in the bone marrow, which is why the letter B was subsequently given the meaning “bone marrow”.


weak immune system

A weakened immune system makes the body more susceptible to any type of infection. Lifestyle often plays a significant role in weakening the immune system. Sometimes, however, diseases such as AIDS or autoimmune diseases are responsible, and even the strongest immune system loses its punch with increasing age.


Reasons for a weakened immune system include:


  • High age
  • unhealthy or malnutrition
  • Stress
  • Lack of exercise
  • Sleep deprivation
  • Smoking and alcohol consumption
  • Chronic diseases (e.g. HIV/AIDS, diabetes mellitus, COPD)
  • Autoimmune diseases (e.g. inflammatory rheumatism)


Strengthen the immune system

In order for our defenses to work optimally,a healthy lifestyle is crucial. So you can strengthen your immune system naturally throughregular exercise. Another important factor is a balanced diet and the supply of vitamins and trace elements.


These include vitamins B6 and E as well as the trace elements selenium, iron, zinc and antioxidants such as beta-carotene and vitamin C.


Vitamine B6

It affects metabolism, hormones and nerves and contributes to normal functioning of the immune system and nervous system, as well as reducing fatigue. Vitamin B6 is found, among other things, in fish such as salmon or mackerel, as well as in meat and liver. Also in plant foods, such as nuts, whole grains, potatoes, tomatoes, red peppers and in legumes.


Vitamine E

It is present in every cell of the body as one of the most important protective vitamins. Among other things, vitamin E protects the blood vessels and makes a decisive contribution to the function of our immune system. Vitamin E is found mainly in oils such as wheat germ oil, rapeseed oil, sunflower oil, as well as in nuts, fruits, vegetables and bread.



It protects the body’s cells from attacks by so-called free radicals. In addition, the trace element is needed for the production of thyroid hormones and for the formation of sperm. A deficiency of selenium leads, for example, to disorders of the immune system as well as to restrictions in muscle function. You can get it from foods like meat, fish, sausage, eggs and seafood. Also about plant foods such as Brazil nuts (consume only in moderation), asparagus, mushrooms, cabbage vegetables and legumes.



The trace element iron performs many tasks in the body, including transporting oxygen from the lungs to the tissues, storing oxygen in the muscles and transferring electrons in energy metabolism. It is also important for the normal functioning of the immune system. In the diet, it can be obtained, for example, from dark meat, offal such as liver, and legumes.



Zinc is essential for the body’s defense system and protects against various diseases. The trace element is found in many foods. Particularly high-quality sources of zinc are meat (beef, poultry and pork), offal, fish and shellfish, hard cheese and eggs.



The body is constantly exposed to free radicals through its environment, this leads to oxidative stress. Oxidative stress promotes diseases and accelerates the aging of cells and thus of the entire body. Antioxidants neutralize these free radicals and restore the oxidative balance. Especially red fish and seafood like salmon and shrimps are rich in antioxidants like beta-carotene, furthermore “traffic light colored” fruits and vegetables like spinach or grapes (green), tomatoes and berries (red) as well as carrots, oranges and apples (yellow/orange) are recommended.