Chemotaxis influences the direction of locomotion of cells and living organisms. Chemotaxis is based on a concentration gradient of substances, which can be represented by a substance concentration gradient.
What is chemotaxis?
Chemotaxis affects the direction of locomotion of cells and living organisms. The term chemotaxis refers to the influence of the locomotion of living organisms and cells. A distinction can be made between positive and negative chemotaxis. Chemotaxis is one of the most important and basic physiological reactions of cells. In positive chemotaxis, attraction by certain messenger substances takes place. In negative chemotaxis, on the other hand, repulsion occurs. Substances that trigger positive chemotaxis are called attractors. In contrast, substances that trigger negative chemotaxis are repellents. For example, positive chemotactic bacteria respond to sugars, oxygen, and glucose, and negative chemotactic bacteria respond to cytotoxins. Chemotaxis also plays an important role in immune defense.
Function and role
When inflammation occurs in the body, various messenger substances are produced and secreted. These are also known as chemokines. They attract the cells of the immune system to the site of the inflammatory reaction. Various substance groups can act as chemokines in this process. 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 specifically designed for the chemotactically active substances. When a chemokine docks onto these receptors, the immune cells can form so-called pseudopodia. Pseudopodia are thin cell extensions that allow the cell to engage in amoeboid, active locomotion. This allows the immune cells to approach the site with the increasing concentration of chemokines. Thus, the cells quickly reach the site of inflammation even from more distant regions of the body. Conversely, there is also negative chemotaxis, in which the cells of the immune system are moved away from the site of the pathological event. In this way, possible overreactions can be avoided. Chemotaxis also plays an important role in the early stages of embryonic development (embryogenesis). Embryonic development is the phase from fertilization of the oocyte to organ formation. During embryogenesis, the three cotyledons are controlled by a certain concentration gradient of different messenger substances and are brought to the right place.
Diseases and disorders
But chemotaxis does not only have positive consequences for the body. Cancer cells also take advantage of this process. They use chemotaxis to approach blood vessels. Once they reach a blood vessel, they can grow into it and distribute their cells throughout the body via the bloodstream. This chemotaxis-based process is called 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 inherited disease that negatively affects normal cell migration. As a result, recurrent purulent infections of the respiratory tract and skin develop. Another disease with decreased chemotaxis is Kartagener 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. The lack of microtubule mobility damages the cilia in the epithelia of the respiratory organs. As a result, mucus transport is impaired and adequate cleansing of the respiratory organs cannot take place. As a result, chronic inflammation occurs in the respiratory tract. In both of these diseases, chemotaxis is causative. In many other diseases, however, it plays an important role during the course of the krnak disease. While chemotaxis is increased in inflammation, the infectious diseases AIDS and brucellosis are associated with decreased chemotaxis. Brucellosis is an infectious disease caused by the aerobic rod bacterium Brucella.In diseases such as arteriosclerosis or arthritis, chemotaxis is negatively influenced by the pathological processes. Periodontitis, psoriasis and metastatic tumors are also associated with increased chemotaxis. In contrast, chemotaxis tends to be decreased 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 the nerve cells. This results in damage to the myelin sheath. This is accompanied by symptoms such as paralysis or insensitivity. Hodgkin’s disease also shows decreased chemotaxis. Hodgkin’s disease is a malignant disease of the lymphatic system characterized by painless swelling of the lymph nodes and the presence of Sternberg-Reed cells. Decreased chemotaxis can also be detected in male infertility. However, the reason for this decreased chemotaxis has not yet been conclusively determined. Chemotaxis is also affected by intoxications and intoxication. Intoxications with asbestos and benzpyrene lead to increased chemotaxis. Benzpyrene is present in automobile and industrial exhaust. Benzpyrene is also produced during cigarette smoking. Asbestosis develops from inhaled asbestos dust. It first leads to pulmonary fibrosis and later, in most cases, to lung cancer. Intoxications with ozone, on the other hand, are associated with decreased chemotaxis. Ozone has an oxidizing effect and irritates the respiratory tract in humans, causing severe temporal headaches. Increased chemotaxis is further seen in intoxications with chromium and mercury salts.
