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Get to know your immune system

Your immune system is a powerful, extremely important defense system that protects and defends your body. But how exactly does the immune defense system work? What are the tasks of the immune system? And how are the immune system and the intestine connected? Here you will learn, simply explained, how exactly your immune system works for you every day.


  1. The immune system: a definition
  2. What are the functions of the immune system?
  3. The function of the immune system simply explained
  4. How exactly is the immune defense set in motion?
  5. How are the intestine and the immune system connected?
  6. Weakness and diseases of the immune system

The immune system: a definition

On the one hand, the immune system fulfills a barrier function: it protects the organism from the penetration of foreign substances and living beings. On the other hand, it intervenes if pathogens should ever enter the body and ensures that bacteria, viruses, fungi, germs and parasites are fought and an infection is prevented.

The components of the immune system are diverse: Among others, organs such as the skin, the spleen and the intestine belong to it. Together with other endogenous systems (for example, the lymphatic system and bone marrow), they protect the organism – i.e. your body – from diseases. The immune system is also called “immune defense” or “body’s own defense”.

What are the tasks of the immune system?

The most important tasks of the immune system are:

  1. Detect pathogens and render them harmless.
  2. Neutralize harmful substances that enter the body from the outside.
  3. Detect undesirable changes in the body (for example, cancer cells) and act against them.

The immune system is the body’s most important defense mechanism. Without it, we would be defenceless against our environment and would not be able to react appropriately to pathological changes in the body. In short: without a functioning immune defense, we would die.

The function of the immune system simply explained

In order for the body to show an immune response to pathogens such as bacteria, viruses or fungi, diverse body systems and organs must work together. These each have a specific function within the immune system:

  • The skin and mucous membranes form the first barrier against pathogens and protect the body as best as possible against their penetration.
  • At the palatine and pharyngeal tonsils, bacteria that have reached the oral cavity come into contact with immune cells for the first time.
  • The thymus (a gland above the heart) plays a key role in the development of immune cells. It ensures, for example, that the lymphocytes (white blood cells) can distinguish between cells that are endogenous and those that are foreign to the body
  • The lymphatic system enables the removal of pathogens.
  • The spleen is responsible for the breakdown of old red blood cells and stores the scavenger cells of the non-specific defense system, which we will discuss in more detail in a moment. In addition, the spleen contributes to the proliferation of lymphocytes, which subsequently mature in the thymus.
  • The bone marrow is also important for the function of the immune system: red and white blood cells are formed there, as well as platelets (thrombocytes), which are crucial for hemostasis and clotting. From there, the corresponding cells travel to other organs responsible for proliferation and maturation, resulting in a strong immune system.

The intestine and the intestinal flora are also important components of the immune system. Around two thirds of all antibody-forming immune cells are located there and enable effective defense against foreign invaders. The defense cells of the intestine mark and destroy the pathogens and store information about foreign cells so that they can react more quickly to them in the future. In addition, bacteria in the intestinal flora help to prevent pathogens from colonizing so easily. A healthy intestine is therefore necessary for a functioning defense system.

All these components of the immune system work together to protect the body. In doing so, the immune system fights pathogens in two different ways: with the innate (non-specific) immune defense and with the acquired (specific) immune defense. These complement each other and thus provide comprehensive protection.

1. Innate (non-specific) immune defense

The non-specific immune system is active from birth and is able to render harmless a wide range of pathogens in the body. Both physical barriers (such as the skin) and chemical barriers (such as the hydrochloric acid in gastric juice) are used in this process. A distinction is also made between cellular and non-cellular (humoral) mechanisms.

The cellular mechanisms of innate immune defense include the so-called phagocytes, which take up foreign bodies and pests, break them down inside and thereby destroy them. The humoral defense (from the Latin “humor” for “fluid”), on the other hand, uses the body’s own dissolved substances such as enzymes, which are found in body fluids and have an antibacterial effect. In addition, the so-called complement system is part of the non-specific defense. This is an enzymatic system of the liver that can dissolve invading foreign cells.

The non-specific immune defense is innate. It is not pathogen-specific and defends the body against a large number of completely different pathogens. Unlike the specific immune defense, it does not form an immunological memory. On the other hand, it works extremely quickly and begins seconds or minutes after the first contact with a pathogen.

The function of the innate immune defense is not always sufficient. In addition, we have specific immune defenses for such cases, which are capable of learning and continue to develop in the course of our lives.

2. The acquired (specific) immune defense

If the body’s first defense attempt by the innate immune system fails, the acquired immune system, i.e. the specific immune defense, must intervene. However, between four and seven days can pass before it gets going. Thus, although the specific immune defense takes longer than the nonspecific one, the wait pays off. After all, the acquired defense has a higher accuracy than the innate one. However, this specific defense system is not active from birth, but is only developing.

And this is how it works:

  1. When the body first comes into contact with a pathogen against which the specific defense can specifically develop defense cells, the organism produces immune cells, namely the so-called B and T lymphocytes.
  2. These antibodies are always “tailor-made” for one type of pathogen. They can bind to the pathogens and thus destroy them directly.
  3. Sometimes, however, the binding of the antibodies also makes it easier for the non-specific defense system to render the pathogens harmless.

At the same time, the organism forms memory cells for this specific pathogen and stores the information. If a new infection occurs, the body can immediately recognize the type of pathogen and produce the specific antibodies much faster. This is because the specific immune defense system remembers attackers – and it is precisely this ability to remember that makes it so effective. It specifically fights a particular invader. While the non-specific defenses do not know the identity of the pathogen and merely set in motion general protective mechanisms, the acquired immune defense knows exactly what to do and initiates the appropriate defensive response.

This is how the specific immune defense helps you to fight diseases

At the first contact with a previously unknown pathogen, the symptoms of the disease are still pronounced. Our body needs a few days to initiate an appropriate defense reaction. When we come into contact with the same pathogen again, the situation is different: either the symptoms do not set in at all or they are much weaker than the first time. This also explains why you get certain diseases only once in your life. Once you have overcome them, you are immune to them. However, this does not happen overnight, because the development of specific immune defenses is a lifelong learning process.

What belongs to the specific immune defense?

The specific defense sends out various helpers to render the pathogens harmless. They take over different functions in your immune system:

The T lymphocytes

The T lymphocytes, which belong to the group of white blood cells, are responsible for the cellular immune defense in the tissue. They register infected cells and banish them from the body.

They are formed in the bone marrow. While they develop into finished cells in the thymus gland, they learn their trade: distinguishing the body’s own cells from foreign cells. On their surface, they are equipped with special recognition features to which pathogens can dock according to the lock-and-key principle.

When this happens, the affected T cells multiply rapidly. In the process, they trigger strong defense reactions that drive the pathogens out of the body.

The B lymphocytes

The B lymphocytes also participate in the specific immune defense. They build up antibodies that are mixed into the blood as soluble proteins and are targeted at precisely one pathogen.

However, the two types of lymphocytes do not stand alone; they work closely together. Either they communicate directly while binding to the defense cells or via soluble messengers such as cytokines (which are specific proteins).


How exactly is the immune defense set in motion?

The immune system can be activated by many foreign substances and agents – so-called antigens. These include the proteins on the surface of bacteria, fungi and viruses. When these antigens dock onto special receptors of defense cells, the cell processes described above are set in motion – the immune system begins to work.

The cells of the body also have such surface proteins. However, the immune system does not normally act against them. If it mistakenly classifies cells of the body as foreign, this is called an autoimmune reaction. In this case, the immune system acts against the body’s own healthy cells. Typical autoimmune diseases include type 1 diabetes, multiple sclerosis, psoriasis and rheumatism.

How are the intestine and the immune system connected?

80 percent of the defense cells are located in the intestine. The intestine and its bacterial strains thus play an essential role in immune defense and directly influence general health and well-being. Intestinal flora, intestinal mucosa and the intestinal-associated immune system together form the intestinal barrier, an effective protection against invading pathogens.

Dr. Tewodros Debebe
Head of Science & Co-Founder von BIOMES

Perhaps you have heard the phrase: “The immune system is located in the intestine”. This is not entirely correct, but in fact the intestine and the immune system are connected in several ways.

The colon plays an even greater role in immune defense: it houses the intestinal flora with its many effective bacterial strains. Its mucosa also contains numerous lymph follicles that can recognize and eliminate viruses and bacteria.

The intestinal flora is so important for the immune system

The intestinal flora is home to countless bacteria, many of which are extremely important for the function of the immune system: They produce vital enzymes, support nutrient absorption and neutralize harmful substances and germs that enter the body with food. They also stimulate the formation of the body’s own defense substances.

Some intestinal bacteria produce antibacterial substances that inhibit the growth of foreign bacteria. Lactobacilli and bifidobacteria are particularly effective in this respect: They strengthen the intestinal mucosa and form lactic acid. The resulting acidic environment is friendly to the intestines, but is a hostile environment for harmful bacteria. Lactic acid bacteria can also activate a receptor of human cells and thus directly influence the function of the immune system.

How to support your gut bacteria and immune system

A balanced diet rich in fiber that promotes intestinal health helps your body maintain vital functions. Dietary fiber is not absorbed in the small intestine, but is transported further into the large intestine, where it serves as an energy source for beneficial intestinal bacteria. The more diverse the bacterial population in your intestine, the more effectively the intestinal flora can fulfill its functions for your health.

A varied diet rich in vital substances with whole grains, fruits and vegetables, nuts and legumes also promotes the diversity of species in the intestine. You can also support general intestinal health in this way and thus also strengthen your immune system in the long term.

Weakness and diseases of the immune system

The immune system is a highly complex network. In addition to the intestinal barrier and its interplay of intestinal cells and intestinal flora, the hormone system, the bone marrow, the nervous system, the lymph nodes and many other immune organs, cell types and molecules are also involved. Accordingly, the immune system can react sensitively to stress, an unbalanced diet or hormone fluctuations.

Sometimes a weakness of the immune system is due to congenital immunodeficiencies, diseases such as diabetes or an infection with HIV, medications (such as antibiotics) or allergies. Then you definitely need medical support and care to find the right therapy for your immune system. In many cases, however, you can also do things yourself to strengthen your immune system:

  1. Reduce stress, for example with yoga, Pilates or meditation.
  2. Integrate a balanced diet into your daily routine.
  3. Get fresh air and vitamin D.
  4. Get plenty of exercise (the WHO recommends that adults 18 and older get at least 150 minutes of moderate-intensity exercise or 75 minutes of high-intensity exercise per week)
  5. Go to the sauna regularly.
  6. Sleep at least seven hours a day.

As you already know, a strong intestinal flora is also important, because it is a crucial part of our immune system. If it weakens, the defense against pathogens no longer functions optimally. With the INTEST.pro self-test from BIOMES you can find out whether your intestinal flora is in balance or whether it needs a little “help” so that it can fulfill its functions optimally and make its contribution to the immune defense.

And this is how it works: Simply take a stool sample with the test kit at home, send it to BIOMES and have the sample analyzed by the scientists. You will then receive the analysis, which you can view in a password-protected online dashboard. Based on the results, BIOMES experts will provide you with personal recommendations for optimizing your intestinal flora.

With the evaluation of your INTEST.pro you get information about your intestinal flora and learn how to improve your quality of life.

Learn more about INTEST.pro The intestinal test from BIOMES

Wie analysieren wir deine Darmflora? Was beinhaltet der Test genau? Wo kannst du INTEST.pro kaufen?
Und wie schützen wir deine Daten?

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