The defense reaction is also called immune response and corresponds to the body's own processes for the elimination of alien substances. When the organism recognizes a foreign substance as threatening, it extinguishes it with the help of plasma proteins and killer cells. In autoimmune diseases, the defense reaction is not directed against pathogens, but falsely against the body's own tissue.

What is the defense reaction?

The defense reaction is also called immune response and corresponds to the body's own processes for the elimination of alien substances.

With an immune response, the human body responds to a known or unknown antigen. This natural reaction is also known as a defense reaction and forms the basis of the body's defense against bacteria and other pathogens.

Most immune responses correspond to a congenital and nonspecific immune response. That is, they are not geared to specific pathogens, but generally turn against foreign stimuli in the organism. There are also specific, later acquired immune reactions. An example of this is the learned immune response to specific antigens that are already known to the organism from the past.

In addition to cellular immune responses by T-killer cells, antigen-presenting cells and T-helper cells, humoral immune reactions also take place in the body. The term humoral defense reaction refers to antibodies and antigens in human body fluids.

In the context of any defense reaction, the body fights against foreign or bodily altered cells. Thus, the immune system protects the organism from diseases and ultimately even from death.

Function & Task

The defense system is responsible for eliminating threatening foreign substances from the body. An immune response specifically targets pathogens, such as viruses or bacteria. On the other hand, an immune response can also refer to abnormally altered cells of one's own organism. This mechanism plays an important role, for example, in cancer cells.

The innate immune response proceeds via heir structures and reacts mechanically to foreign stimuli. In contrast, the specific defense reaction uses acquired receptors in the body for stimulus identification. These receptors form in almost unlimited numbers to specific pathogens. Based on his experience, the organism uses the receptors to assess the threat of a foreign stimulus.

If the stimulus is classified as non-threatening, there will be no immune response in the future. This phenomenon is also referred to as immune tolerance. It ensures that the immune system does not react to all substances in the environment.

Non-body substances penetrate permanently into the body. If the immune system reacted to any of these, it would do more harm to the organism than to protect it. The differentiation via the receptors is therefore an important component for the functioning of the defense system.

Only when a stimulus is actually recognized as threatening, a productive immune response is triggered. This immune response is intended to eliminate the threat. The mechanisms on which this defense reaction is based are of great diversity.

On numerous surfaces of the organism are, for example, complement systems of plasma proteins. The purpose of these proteins is to cover and destroy the surface of pathogens. They trigger inflammatory reactions that fight infection. In addition to the killing of pathogens, the complement system also takes over the marking of these pathogens. That makes them discoverable for the killer cells of the body.

The immune response also includes microbicidal substances that are released by cells outside the defense system to activate feeding and killer cells. Meanwhile, the B lymphocytes are constantly producing antibodies. These antibodies bind to foreign structures in a highly specific manner as part of the defense reaction. In interaction, these individual reactions eliminate the threatening substances from the organism.

Immunological overreactions are avoided by the body's own regulatory mechanisms. They would damage the body's own tissue too much and could trigger a septic shock and, in the worst case, death. Without the regulatory units, the immune system could no longer maintain the balance between protective and injurious responses.

Diseases & complaints

The defense system is a highly complex apparatus that can cause many and very different discomforts. Hypersensitivity reactions are conceivable, for example.

Such overreactions usually correspond to septic or anaphylactic shocks. Anaphylactic shock can occur, for example, in the context of contact with chemical substances. Often the organism reacts in this connection with circulatory failure or organ failure.

In contrast, septic shock can occur when the immune system triggers inflammatory reactions throughout the body. Such a reaction is usually due to infectious causes. However, immunological septic shocks may also be associated with actual illness, such as toxic shock syndrome.

Further examples of diseases of the immune system are the so-called autoimmune diseases. In these diseases, the body's own and completely healthy cells trigger defense reactions. The receptors of the immune system incorrectly recognize their own tissue as threatening foreign bodies and attack healthy tissue structures.

Examples of such diseases are the inflammatory disease multiple sclerosis, which permanently attacks the central nervous system, and the systemic lupus, which is directed against the skin, joints and kidneys.

Allergies are also defective defense reactions. In the context of this disease group harmless substances from the environment falsely trigger an immune response.

Complaints related to the body's defense reaction may also be related to immune tolerance. On the one hand, this tolerance is important, so that the immune system is not overloaded and unnecessarily burden the organism with inflammatory reactions. However, if the immune system develops immune tolerance to threatening substances, it can endanger the organism.

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