I. Mechnikov was the first to put forward the theory of phagocytosis. The scientist concluded that he appeared as a result of evolution, was attached to the cells, and now acts as a protective mechanism. Thus, Ilya Ilyich proposed combining such cells into a single system - macrophagic. This system is a strong defense mechanism involved in general and local defense reactions of the body. Its activity regulates the nervous and endocrine systems.
Histiocytes are a type of macrophage - cells that capture and process foreign and toxic particles in humans and animals. They act as immune defenses against pathogenic microbes.
Description and description of the problem
Histiocytes are dormant connective tissue cells with a basophilic cytoplasm with inclusions whose shape changes, since the cells have the ability to move like an amoeba. These cells are macrophages, they play an important role in the body, as they support tissue homeostasis, capture and digest foreign particles, the remains of dead cells, pathogenic bacteria.
With the development of an inflammatory reaction, histiocytes are activated. In the adult body, they develop from connective tissue, as well as from monocytes and lymphocytes.
Varieties of histiocytes
Characteristic cells (histiocytes) are divided into two groups that have a common origin:
- Antigen-processing histiocytes are macrophages that form in the bone marrow from a common precursor with granulocytes. This group includes blood monocytes, as well as all types of tissue macrophages. These cells capture antigens, start and coordinate the initial stages of the immune response, and perform effector functions.
- Antigen-presenting histiocytes are dendritic cells. This group includes alveolar, pleural, peritoneal macrophages and others. They have the ability to adapt to the functions of certain organs. These cells play a major role in the activation of the primary immune response.
Histiocyte formation
Histiocytes are a type of macrophage. In the body of animals and humans, there is a separate group of leukocytes - monocytes. They form in the bone marrow and have a high ability to phagocytosis. They ripen in the blood for several days, and then move to the tissues, where they become macrophages. In tissues, they grow and mature, and then form into histiocytes (these are tissue macrophages).
When an inflammation center provoked by an infection appears in the body, these cells begin to multiply actively. They form around pathogenic microbes that cannot be destroyed, a huge rampart that delimits the focus of inflammation from healthy tissues. They also process the remains of dead red blood cells, cell debris.
Macrophage activity
The cells of the immune system of animals and humans produce antibodies that are in the blood. They enter into contact with pathogens, forming a shell on their surface, which is recognized by macrophage receptors. Macrophages form outgrowths on the membrane - pseudopod legs, which grow around the pathogen, envelop it, merge with it, forming a phagosome. Thus, pathogenic particles are completely located inside the phagosome. Then, the destruction of a foreign microorganism occurs as a result of exposure to an acidic medium with bactericidal properties. Some of the dead cells are excreted by lymph and blood, another part remains in the phagosomes, forming residual bodies.
Cytology
In medical practice, there is a need for differentiation of macrophages, including histiocytes, with dendritic cells. This problem is quite complex, it is solved using histochemical, cytomorphological and immunophenotypic methods. Histiocytes in cytology play an important role, since they make it possible to determine the presence of a focus of inflammation in the body. They may also indicate the presence of cancer.
Histiocytes in a smear for cytology are detected with inflammation, the presence of HPV and other diseases. If they were discovered in the early stages, they can be successfully cured.
Also, histiocytes in a smear from the vagina of women are often detected at the stage of menstruation.
A laboratory technician who studies samples taken from patients should not only identify, but also study the structure of the macrophages found, including histiocytes. They often have many residues of pathogens digested by them. If it is possible to identify what exactly is in them, this helps to establish what they were fighting against, as well as identify the disease in humans.
Conclusion
Histiocytes are tissue macrophages that are stationary. When the inflammatory process begins in the body, they are activated and begin to multiply by division. Histiocytes play a decisive role in the body's immune response, since there are much more of them than white blood cells. They are the most active cells of the connective tissue, the main component of the reticuloendothelial system.
With a decrease in the activity of leukocytes and a decrease in their number, histiocytes “attack” pathogenic microbes and try to eliminate them. Histiocytes are the second line of defense that connects to the first line when its ranks begin to thin.
These cells have the ability to receive a signal from pathogenic particles, as they have a mechanism comparable to a radar receiver. Such a cell releases pseudopod legs, which envelop an alien particle, and destroys it, thus protecting the body.