StemCell Therapy

The immune system has a vital role: It protects your body from harmful substances, germs and cell changes that could make you ill. It is made up of various organs, cells and proteins.

As long as your immune system is running smoothly, you dont notice that its there. But if it stops working properly because its weak or can't fight particularly aggressive germs you get ill. Germs that your body has never encountered before are also likely to make you ill. Some germs will only make you ill the first time you come into contact with them. These include childhood diseases like chickenpox.

Without an immune system, we would have no way to fight harmful things that enter our body from the outside or harmful changes that occur inside our body. The main tasks of the bodys immune system are

to recognize and neutralize harmful substances from the environment, and

to fight disease-causing changes in the body, such as cancer cells.

The immune system can be activated by a lot of different things that the body doesnt recognize as its own. These are called antigens. Examples of antigens include the proteins on the surfaces of bacteria, fungi and viruses. When these antigens attach to special receptors on the immune cells (immune system cells), a whole series of processes are triggered in the body. Once the body has come into contact with a disease-causing germ for the first time, it usually stores information about the germ and how to fight it. Then, if it comes into contact with the germ again, it recognizes the germ straight away and can start fighting it faster.

The bodys own cells have proteins on their surface, too. But those proteins dont usually trigger the immune system to fight the cells. Sometimes the immune system mistakenly thinks that the body's own cells are foreign cells. It then attacks healthy, harmless cells in the body. This is known as an autoimmune response.

There are two subsystems within the immune system, known as the innate (non-specific) immune system and the adaptive (specific) immune system. Both of these subsystems are closely linked and work together whenever a germ or harmful substance triggers an immune response.

The innate immune system provides a general defense against harmful germs and substances, so its also called the non-specific immune system. It mostly fights using immune cells such as natural killer cells and phagocytes (eating cells). The main job of the innate immune system is to fight harmful substances and germs that enter the body, for instance through the skin or digestive system.

The adaptive (specific) immune system makes antibodies and uses them to specifically fight certain germs that the body has previously come into contact with. This is also known as an acquired (learned) or specific immune response.

Because the adaptive immune system is constantly learning and adapting, the body can also fight bacteria or viruses that change over time.

Brandes R, Lang F, Schmidt R (Ed). Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2019.

Menche N (Ed). Biologie Anatomie Physiologie. Mnchen: Urban und Fischer; 2016.

Pschyrembel. Klinisches Wrterbuch. Berlin: De Gruyter; 2017.

IQWiG health information is written with the aim of helpingpeople understand the advantages and disadvantages of the main treatment options and healthcare services.

Because IQWiG is a German institute, some of the information provided here is specific to theGerman health care system. The suitability of any of the described options in an individualcase can be determined by talking to a doctor. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by ateam ofhealth care professionals, scientists and editors, and reviewed by external experts. You canfind a detailed description of how our health information is produced and updated inour methods.

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How does the immune system work? - InformedHealth.org ...

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