Body processes

Defense Response – Function, Task & Diseases

Defensive reaction

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

What is the defensive reaction?

The human body reacts to a known or unknown antigen with an immune response . This natural reaction is also known as the defense reaction and forms the basis of the body’s defense against bacteria and other pathogens.

Most immune responses correspond to an innate and non-specific immune response. This means that they are not aimed at specific pathogens, but generally turn against foreign stimuli in the organism. There are also specific immune reactions that are acquired later. An example of this is the learned immune response to specific antigens that the organism is already familiar with 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 the human body fluids.

As part of every defense reaction, the body fights cells that are foreign to the body or cells that have been modified in the body . The immune system thus protects the organism from diseases and ultimately even from death.

Function & task

The immune 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 relate to pathologically altered cells in one’s own organism. This mechanism plays an important role in cancer cells , for example .The innate immune response runs via hereditary structures and reacts mechanically to foreign stimuli. The specific defense reaction, on the other hand, uses acquired receptors in the body to identify stimuli. These receptors form in almost unlimited numbers for specific pathogens. The organism uses the receptors to assess the threat of an exogenous stimulus based on its experience.

If the stimulus is classified as harmless, there will be no immune reaction in the future. This phenomenon is also known as immune tolerance. It ensures that the immune system does not react to all substances in the environment.

Foreign substances constantly penetrate the body. If the defense system reacted to each of them, it would harm the organism rather than protect it. Differentiation via the receptors is therefore an important component for the functioning of the defense system.

A productive immune response is only triggered if a stimulus is actually recognized as threatening. This immune response is designed to eliminate the threat. The mechanisms on which this defense reaction is based are highly diverse.

For example, complement systems made of plasma proteins are found on numerous surfaces of the organism. The task of these proteins is to cover and destroy the surface of pathogens. They trigger inflammatory reactions that fight infections . In addition to killing pathogens, the complement system also labels these pathogens. This makes them detectable by the body’s killer cells.

The immune response also includes microbicidal substances that are released by cells outside the immune system to activate scavenger and killer cells. Meanwhile, the B- lymphocytes constantly produce antibodies . These antibodies bind to foreign structures in a highly specific manner as part of the defense reaction. In combination, 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 septic shock and, in the worst case, death. Without the regulatory units, the immune system could no longer keep the balance between protective and damaging reactions.

Diseases & Ailments

The immune system is a highly complex apparatus that can cause numerous and very different complaints. Hypersensitivity reactions are conceivable, for example.Such overreactions usually correspond to septic or anaphylactic shock . Anaphylactic shock can occur, for example, as part of contact with chemical substances. In this context, the organism often reacts with circulatory failure or organ failure .

Septic shock, on the other hand, 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 can also occur in connection with an actual illness, for example in the context of toxic shock syndrome .

Other 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 mistakenly recognize their own tissue as a threatening foreign body and attack the healthy tissue structures.

Examples of such diseases are the inflammatory disease multiple sclerosis , which constantly attacks the central nervous system , and systemic lupus , which affects the skin , joints and kidneys .

Allergies are also faulty defense reactions. In this group of diseases, harmless substances in the environment falsely trigger an immune response.

Complaints related to the body’s own defense reaction can also occur in connection with immune tolerance. On the one hand, this tolerance is important so that the immune system is not overloaded and the organism is not unnecessarily burdened with inflammatory reactions. However, if the defense system develops immune tolerance to threatening substances, this can put the organism in danger.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.