Chemotaxis

By Chemotaxis the direction of movement of cells and living beings is influenced. Chemotaxis is based on a concentration gradient of substances that can be represented by a substance concentration gradient.

What is chemotaxis?

The term chemotaxis is understood to mean influencing the locomotion of living beings and cells. A distinction can be made between positive and negative chemotaxis. Chemotaxis is one of the most important and fundamental physiological responses of cells.

In positive chemotaxis, certain messenger substances are attracted to the body. With negative chemotaxis, however, there is rejection. Substances that cause positive chemotaxis are known as attractants. In contrast, substances that cause negative chemotaxis are repellents. For example, chemotactic bacteria react positively to sugar, oxygen and glucose and chemotactic bacteria react negatively to cell toxins. Chemotaxis also plays an important role in immune defense.

Function & task

When there is inflammation in the body, various messenger substances are formed and released. These are also known as chemokines. They attract the cells of the immune system to the site of the inflammatory response. Different groups of substances can act as chemokines. These include the components of the complement system, cytokines, components of the cell membrane of bacteria and leukotrienes.

On certain white blood cells (granulocytes and macrophages) there are receptors that are specially designed for the chemotactically active substances. When a chemokine docks to these receptors, the immune cells can develop so-called pseudopodia. Pseudopodia are thin cell processes that enable the cell to move amoeboid and active.

This allows the immune cells to approach the location as the concentration of chemokines increases. In this way, the cells quickly reach the site of inflammation from more distant parts of the body.

Conversely, there is also negative chemotaxis, in which the cells of the immune system are removed from the location of the pathological process. In this way, possible overreactions can be avoided.

Chemotaxis also plays an important role in the early phases of embryonic development (embryogenesis). Embryonic development is the phase from fertilization of the egg cell to organ anlage. During embryogenesis, the three cotyledons are controlled by a certain concentration gradient of different messenger substances and brought to the right place.

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Illnesses & ailments

But chemotaxis not only has positive effects on the body. Cancer cells also make use of this process. They use chemotaxis to approach blood vessels. Once they have reached a blood vessel, they can grow into it and distribute their cells in the body via the bloodstream. This chemotaxis-based process is known as metastasis.

Many infections and inflammations are also based on chemotaxis. There are several diseases in which impaired chemotaxis is the primary causative factor. An example of such a disease is Chediak-Higashi syndrome. This syndrome is a rare hereditary disease that negatively affects normal cell migration. As a result, recurrent purulent infections of the respiratory tract and skin develop.

Another disease with reduced chemotaxis is Kartagener's syndrome. This disease is also congenital. The cause of the disease is a missing subunit of the motor protein dynein. This is responsible for the chemotaxis of the microtubules in the cells. Due to the lack of mobility of the microtubules, the cilia in the epithelia of the respiratory organs are damaged. This impairs the transport of mucus and the respiratory organs cannot be adequately cleaned. This leads to chronic inflammation in the airways.

Chemotaxis is the cause of these two diseases. However, in many other diseases it plays an important role during the course of the disease. While the chemotaxis is increased in inflammation, the infectious diseases AIDS and brucellosis go hand in hand with a decreased chemotaxis. Brucellosis is an infectious disease caused by the aerobic rod bacterium Brucella. In diseases such as arteriosclerosis or arthritis, the chemotaxis is negatively influenced by the pathological processes.

Periodontitis, psoriasis and metastatic tumors are also associated with increased chemotaxis. In contrast, chemotaxis is rather reduced in multiple sclerosis. Multiple sclerosis is a chronic inflammatory disease of the nervous system. It is an autoimmune disease in which the body attacks the myelin sheaths of nerve cells. This leads to damage to the myelin layer. This is accompanied by symptoms such as paralysis or abnormal sensations.

Hodgkin's disease also shows decreased chemotaxis. Hodgkin's disease is a malignant disease of the lymphatic system that manifests itself as painless swelling of the lymph nodes and is characterized by the presence of Sternberg-Reed cells.

Reduced chemotaxis can also be demonstrated in male infertility. However, it has not yet been conclusively clarified why there is decreased chemotaxis here.

Chemotaxis is also impaired by intoxication and intoxication. Asbestos and benzopyrene intoxications lead to increased chemotaxis. Benzpyrene is found in automobile and industrial exhaust fumes. Benzopyrene is also produced when smoking cigarettes. Asbestosis develops due to inhaled asbestos dust. Lung fibrosis occurs first, and later, in most cases, lung cancer.

Ozone intoxication, on the other hand, is associated with reduced chemotaxis. Ozone has an oxidizing effect and irritates the respiratory tract in humans and leads to severe temple headaches. There is also increased chemotaxis in the case of intoxication with chromium and mercury salts.