Mononuclear phagocytic system. Mononuclear phagocyte system
Mononuclear phagocytes (macrophages) constitute the most important group of long-lived cells capable of phagocytosis.
Tissue macrophages and their precursors - monocytes, promonocytes and monoblasts - form a system of mononuclear phagocytes.
Macrophages are long-lived phagocytes that have many general functions with neutrophils. In addition, macrophages as secretory cells participate in many complex immune and inflammatory reactions, in which neutrophils do not participate.
Monocytes, like neutrophils, leave vascular bed by diapedesis, but circulate in the blood longer: their half-circulation period ranges from 12 to 24 hours. After monocytes enter the tissue, they turn into macrophages, which perform specific functions depending on the anatomical location. Particularly rich in these cells are the spleen, liver, bone marrow and lungs, where the function of macrophages is to remove microorganisms and other harmful particles from the blood.
Alveolar macrophages, Kupffer cells, microglial cells, dendritic cells, macrophages of the spleen, peritoneum, bone marrow and lymph nodes - they all perform specific functions.
Mononuclear phagocytes perform two main functions, carried out by two different types of cells of bone marrow origin:
- “professional” macrophages, whose main role is the elimination of corpuscular antigens, and
- antigen presenting cells (APC), whose role is to absorb, process and present antigen to T cells.
Macrophages are formed from bone marrow promonocytes, which, after differentiation into blood monocytes, are retained in tissues in the form of mature macrophages, where they form a system of mononuclear phagocytes. Their content is especially high in the liver of the medullary sinuses. lymph nodes.
Macrophages are long-lived cells with well-developed mitochondria and a rough endoplasmic reticulum.
The role of macrophages in immunity is extremely important - they provide phagocytosis, processing and presentation of antigen to T cells. Macrophages produce enzymes, some serum proteins, oxygen radicals, prostaglandins and leukotrienes, cytokines (interleukins, tumor necrosis factor and others). Macrophages secrete lysozyme, neutral proteases, acid hydrolases, arginase, many complement components, enzyme inhibitors (plasminogen antiactivator, alpha2-macroglobulin), transport proteins (transferrin, fibronectin, transcobalamin II), nucleosides and cytokines (TNF alpha, IL-1, IL -8, IL-12). IL-1 does a lot important functions: acting on the hypothalamus, causing fever; stimulates the release of neutrophils from the bone marrow;
Activates lymphocytes and neutrophils.
TNFalpha (also called cachectin) is a pyrogen. In many ways, it duplicates the action of IL-1, but in addition, it plays important role in the pathogenesis of septic shock caused by gram-negative bacteria. Under the influence of TNF-alpha, the formation of hydrogen peroxide and other free radicals by macrophages and neutrophils sharply increases. In chronic inflammation, TNF-alpha activates catabolic processes and thereby contributes to the development of cachexia, a symptom of many chronic diseases.
The main function of macrophages is to combat those bacteria, viruses and protozoa that can exist inside the host cell, using the powerful bactericidal mechanisms that macrophages possess.
Thus, macrophages are one of the weapons of innate immunity. In addition, macrophages, along with B and T lymphocytes, also participate in the acquired immune response, being an “additional” type of immune response cell: macrophages are phagocytic cells, whose function is to “swallow” immunogens and process them for presentation to T lymphocytes in the form suitable for an immune response.
Unlike lymphocytes, macrophages do not have specific recognition abilities. In addition, macrophages appear to be responsible for the induction of tolerance (see T lymphocytes: tolerance).
At autoimmune diseases macrophages remove immune complexes and other immunologically from the blood active substances. Macrophages are involved in wound healing, removal of dead cells and the formation of atherosclerotic plaques.
Discover
Letki-prev gred bone marrow
[romonocytes That same
onocytes. IN peripheral blood G,
acrophages (possessing large phage-
(tarnoi activity): , ;
Kupffer cells in the liver
alveolar macrophages in the lungs
free and fixed macrophages In lymph nodes, spleen
pleural and peritoneal macrophages in serous cavities
osteoclasts B bone tissue
cells Microglia B nervous fabrics
The immune system distinguishes between central and peripheral organs; these same organs perform a hematopoietic function. In mammals, the central organs include the red bone marrow and thymus; in birds, the bursa of Fabricius; to the peripheral - lymph nodes, spleen, lymphoid formations of the digestive tract and respiratory organs, blood, lymph, microphage system and system of mononuclear phagocytes (macrophages).
Red bone marrow. IN red bone marrow continuously matures red blood cells, leukocytes, and blood platelets. Bone marrow appears in the mesenchyme in the third month of embryonic development and begins to function at a very early age.
The composition of the red bone marrow includes the main myeloid tissue, the skeleton, adipose tissue, blood vessels, nerves. Hematopoietic tissue fills the cells of the spongy bones, their medullary areas and large Haversian canals. With age, red bone marrow degenerates and is replaced by yellow bone marrow, which fills the bone marrow areas tubular bones and part of the cells of spongy bone substance. Until the end of life, islands of hematopoietic cells remain in the yellow bone marrow in the tubular bones. Red bone marrow, as an active hematopoietic organ, is preserved in the flat and short bones of the body (sternum, vertebrae, cranial bones) and only partially in the epiphyses of long bones. As we age, mucous (gelatinous) bone marrow appears due to degeneration and atrophy of the adipose tissue of the bone marrow. The volume of bone marrow is approximately equal to the volume of the liver.
Thymus. Central authority immune system(thymus, or thymus gland). It is well developed in embryos and young animals in the first years of life, with age it is reduced, but not completely, starting from the cervical part, and the thoracic lobes remain. In the developed state, there is an unpaired thoracic lobe, which lies in front of the heart, and a paired cervical lobe, which is located on the sides of the trachea and can reach the larynx. The thymus is an endocrine gland, since its hormone thymosin affects the differentiation of lymphocytes.
Spleen. An organ with multiple functions. Before the birth of the animal, erythrocytes and leukocytes are formed in it, through the splenic vein they enter the portal vein and then into the caudal vena cava.
The spleen is located to the left of the stomach. Its shape is varied, often elongated (Fig. 83). The surface of the organ is covered serosa, which fuses with the capsule and passes to the greater curvature of the stomach, where it forms the gastrosplenic ligament. On the visceral surface of the organ in the area of attachment of the ligament there is a hilum of the spleen. Trabeculae (crossbars) extend from the capsule, forming the skeleton of the spleen in the form
Rice. 83. Spleen:
large cattle; b di; V - pigs
sponge filled with parenchyma - white and red splenic pulp (Fig. 84).
White pulp is constructed from lymphoid tissue, collected around the arteries in the form of balls called lymphatic follicles of the spleen or splenic corpuscles. The number of follicles varies in different animals: in cattle there are many of them and are clearly demarcated from the red pulp; Pigs and horses have fewer follicles.
In the follicles, four poorly demarcated zones are distinguished: periarterial; breeding center (light center); mantle and marginal, or marginal. The periarterial zone occupies a small area of the follicle near the artery and is formed mainly from T-lymphocytes that enter here through capillaries from the arteries of the lymph node, and interdigitating cells. It is believed that these cells adsorb antigens that come here with the blood and transmit information about the state of the microenvironment to T-lymphocytes; they subsequently migrate to the sinuses of the marginal zone through the capillaries. The periarterial zone is analogous to the thymus-dependent zone of the lymph nodes.
The reproductive center, or light center, reflects the functional state of the follicle and can change significantly during infections and intoxications. In structure and functional purpose it corresponds to the follicles of the lymph node and is a thymus-independent area. Consists of reticular cells and a cluster of phagocytes. Plasmocytes are found at the border with the mantle zone.
contains plasma cells and macrophages. Adjacent tightly to each other, the cells form a kind of crown, stratified by circularly directed reticular fibers.
The marginal, or marginal, zone is a transitional area between the white and red pulp, consists mainly of T- and B-lymphocytes and single macrophages, surrounded by marginal, or marginal, sinusoidal vessels with slit-like pores in the wall.
The red pulp of the spleen consists of reticular tissue with blood cellular elements located in it, giving it a red color, and numerous blood vessels, mainly of the sinusoidal type. Number of venous sinuses in the spleen of animals different types not the same. There are many of them in rabbits, dogs, guinea pigs, less in cats, large and small livestock. The part of the red pulp located between the sinuses is called the splenic, or pulp-paired, cords.
The red pulp contains macrophages - splenocytes, which carry out phagocytosis of damaged red blood cells. As a result of the breakdown of hemoglobin in erythrocytes absorbed by macrophages, bilirubin and iron-containing transferrin are formed and released into the blood. Bilirubin is transported to the liver, where it becomes part of the bile. Transferrin from the bloodstream is taken up by bone marrow macrophages, which supply iron to newly developing red blood cells. Blood is deposited in the spleen (up to 16%) and platelets accumulate.
Features of the blood circulation of the spleen: the splenic artery enters through the hilum of the spleen, which branches into trabecular arteries, which pass into the pulpal arteries, which branch in the red pulp. The artery passing through the white pulp is called the central artery. It gives off several capillaries and, emerging into the red pulp, branches in the form of a brush into brush arterioles, at the end of which there is a thickening - an arterial sleeve, clearly expressed in pigs. The sleeves perform the function of sphincters that block the flow of blood, since contractile filaments are found in the endothelium of the ellipsoidal, or sleeve, arterioles. This is followed by short arterial capillaries, most of which flow into venous sinuses(closed circulation), but some may directly open into the reticular tissue of the red pulp (open circulation) and then into the venous capillaries. From them, blood is delivered to the trabecular veins, and then to the splenic vein.
Sinuses are the beginning venous system spleen. Their diameter ranges from 12 to 40 microns depending on the blood circulation. In the wall of the sinuses, at the place where they pass into the veins, there are similarities of muscle sphincters. With open arterial and ve-
Nose sphincters blood passes freely through the sinuses into the veins. Contraction of the venous sphincter leads to the accumulation of blood in the sinus. Blood plasma penetrates the wall of the sinus, which contributes to the concentration in it cellular elements. When the venous and arterial sphincters close, blood is deposited in the spleen. When the sinuses stretch, gaps form between the endothelial cells through which blood can pass into the reticular tissue. Relaxation of the arterial and venous sphincters, as well as contraction of smooth muscle cells capsules and trabeculae lead to the emptying of the sinuses and the release of blood into the venous bed. Outflow venous blood from the pulp of the spleen is carried out through the venous system. The splenic vein exits through the hilum of the spleen and drains into the portal vein.
The lymph nodes(palatine, lingual, pharyngeal, tubar, peri-epiglottic in pigs), tonsils, Peyer's patches of the mucous membrane small intestine and single solitary follicles of the large intestine produce lymphocytes and macrophages and perform protective and immunological functions.
The liver performs a hematopoietic function in embryonic period until the red bone marrow has developed (in connection with the formation of the bony skeleton), which occurs shortly before the animal is born.
Control questions and tasks,
" 1. What organs belong to the circulatory system? ■}
2. Explain the structure and work cycle of the heart. f
3.How does blood move through big circle blood circulation?
4. How does the pulmonary circulation work? ,.".
5.What shaped elements blood do you know? What is plasma? »
6. Describe the scheme of the blood coagulation process.
7.How is blood used in industry? i
8. Describe arteries, capillaries and veins.
9.What are the general patterns of progress and branching? circulatory vessels?
10.What arterial lines are present on the head, torso, thoracic and pelvic limbs, what are their main branches?
11.How it is formed lymphatic system What is lymph?
12.What structure do they have? lymphatic vessels and lymph nodes?
13.What are the main lymph nodes and lymphatic ducts are there in animals?
14.What organs are classified as hematopoietic organs, where are they located, how are they structured and what are their functions?
15.What organs vascular system perform a protective immunological function?
Mononuclear phagocyte system(Greek monox one + lat. nucleos nucleus: Greek phagos devouring, absorbing + histol. sutus cell; synonym: macrophage system, monocyte-macrophage system) - a physiological protective system of cells with the ability to absorb and digest foreign material. The cells that make up this system have a common origin, are characterized by morphological and functional similarity and are present in all tissues of the body.
basis modern presentation about S.m.f. is the phagocytic theory developed by I.I. Mechnikov at the end of the 19th century, and the teaching of the German pathologist Aschoff (K. A. L. Aschoff) about the reticuloendothelial system (RES). Initially, the RES was identified morphologically as a system of body cells capable of accumulating the vital dye carmine. Based on this feature, histiocytes were classified as RES. connective tissue, blood monocytes, liver Kupffer cells, as well as reticular cells hematopoietic organs, endothelial cells of capillaries, bone marrow sinuses and lymph nodes. As new knowledge accumulates and improves morphological methods research, it became clear that ideas about the reticuloendothelial system are vague, not specific, and in a number of positions are simply erroneous. For example, reticular cells and the endothelium of the sinuses of the bone marrow and lymph nodes were for a long time assigned the role of a source of phagocytic cells, which turned out to be incorrect. It has now been established that mononuclear phagocytes originate from circulating blood monocytes. Monocytes mature in the bone marrow, then enter the bloodstream, from where they migrate into tissues and serous cavities, becoming macrophages. Reticular cells perform a supporting function and create the so-called microenvironment for hematopoietic and lymphoid cells. Endothelial cells transport substances through the walls of capillaries. Directly related to protective system reticular cells and vascular endothelium do not have cells. In 1969, at a conference in Leiden dedicated to the problem of RES, the concept of “reticuloendothelial system” was considered obsolete. Instead, the concept of “mononuclear phagocyte system” has been adopted. This system includes connective tissue histiocytes, liver Kupffer cells (stellate reticuloendotheliocytes), alveolar macrophages of the lungs, macrophages of the lymph nodes, spleen, bone marrow, pleural and peritoneal macrophages, osteoclasts of bone tissue, microglia nerve tissue, synoviocytes synovial membranes, Langerhais cells of the skin, pigmentless granular dendrocytes. There are free ones, i.e. moving through tissues, and fixed (resident) macrophages, having a relatively constant place.
Macrophages of tissues and serous cavities, according to scanning electron microscopy, have a shape close to spherical, with an uneven folded surface formed by the plasma membrane (cytolemma).
Under cultivation conditions, macrophages spread out on the surface of the substrate and acquire a flattened shape, and when moving, they form multiple polymorphic pseudopodia. A characteristic ultrastructural feature of a macrophage is the presence in its cytoplasm of numerous lysosomes and phagolysosomes, or digestive vacuoles (rice. 1 ). Lysosomes contain various hydrolytic enzymes that ensure the digestion of absorbed material. Macrophages are active secretory cells that release enzymes, inhibitors, and complement components into the environment. The main secretory product of macrophages is lysozyme. Activated macrophages secrete neutral proteinases (elastase, collagenase), plasminogen activators, complement factors such as C2, C3, C4, C5, and interferon.Cells S. m. f. have a number of functions, which are based on their ability to endocytosis, i.e. absorption and digestion of foreign particles and colloidal liquids. Thanks to this ability they perform protective function. Through chemotaxis, macrophages migrate to foci of infection and inflammation, where they carry out phagocytosis of microorganisms, killing and digesting them. In conditions chronic inflammation may appear special forms phagocytes - epithelioid cells (for example, in infectious granuloma) giant multinucleated cells of the Pirogov-Langhans cell type and cell type foreign bodies. which are formed by the fusion of individual phagocytes into a polykaryon - a multinucleated cell ( rice. 2 ). In granulomas, macrophages produce the glycoprotein fibronectin, which attracts fibroblasts and promotes the development of a.
Cells S. m. f. take part in immune processes. Thus, a prerequisite for the development of a directed immune response is the primary interaction of the macrophage with the antigen. In this case, the antigen is absorbed and processed by the macrophage into an immunogenic form. Immune stimulation of lymphocytes occurs through direct contact with a macrophage carrying a converted antigen. The immune response as a whole is carried out as a complex multi-stage interaction of G- and B-lymphocytes with macrophages.
Macrophages have antitumor activity and exhibit cytotoxic properties against tumor cells. This activity is especially pronounced in the so-called immune macrophages, which lyse target tumor cells upon contact with sensitized T-lymphocytes carrying cytophilic antibodies (lymphokines).
Cells S. m. f. take part in the regulation of myeloid and lymphoid hematopoiesis. Thus, hematopoietic islands in the red bone marrow, spleen, liver and yolk sac embryos are formed around a special cell - the central macrophage, which organizes erythropoiesis of the erythroblastic islet. Kupffer cells of the liver are involved in the regulation of hematopoiesis by producing erythropoietin.
7 System of mononuclear phagocytes unites, based on the unity of origin, morphology and function, peripheral blood monocytes and tissue macrophages various localizations. Peripheral blood monocytes, in the presence of certain factors, can differentiate not only into tissue macrophages but also into dendritic cells (DCs). Such factors are GM-CSF and IL-4. As a result of the action of these cytokines, a monomorphic population of DCs is formed, having the characteristics of immature DCs of peripheral tissues. The maturation, differentiation and activation of macrophages depend on growth factors (IL-3, GM-CSF, M-CSF) and on activating cytokines (IFN-y). Among the functions of IFN-y, one of the most important is the activation of the effector functions of macrophages: their intracellular microbicidal and cytotoxicity, their production of cytokines, superoxide and nitroxide radicals, prostaglandins.
Basic Functions of macrophages: 1) Phagocytosis and pinocytosis - absorption of particles or cells due to flow around them by pseudopodia. Thanks to phagacytosis, macrophages participate in the removal from the body immune complexes and cells undergoing apoptosis. 2) participation in the processes of repair and healing of wounds - macrophages secrete several growth factors that stimulate angiogenesis and induce the formation of granulation tissue and re-epithelialization: basic fibroblast growth factor (bFGF), growth transforming factors GTF-a, GTF-b, insulin-like growth factor (IGF) ). 3) Secretory - secrete more than 100 various types molecules. A) enzymes of nonspecific anti-infective defense (peroxidase, active forms oxygen, nitric oxide, cationic proteins, lysozyme and interferon) B) enzymes active against extracellular proteins - collagenase, elastase, plasminogen activators, lysosomal enzymes. C) BAS, which are mediators and modulators of various physiological processes, primarily inflammation: prostaglandins, leukotrienes, cyclic nucleotides. D) substances that activate or regulate immune reactions. 4) regulation of the immune response - blood monocytes and tissue macrophages synthesize a number of factors that influence differentiation, proliferation and functional activity other participants in the immune response - certain subpopulations of T- and B-lymphocytes 5) effector functions of macrophages during a specific immune response - manifest themselves in HRT reactions, when they are found in infiltrates, mainly. Monocytes. Macrophage receptors - on the surface of macrophages there is a large set of receptors that ensure the participation of macophages in a wide range of physiological reactions, incl. and participation in a specific immune response. Thus, on the membrane of macrophages various receptors are expressed for capturing microorganisms: the mannose receptor (MMR). Receptors for bacterial lipopolysaccharides (CD14), receptors for capturing opsonized microorganisms are expressed on the membrane of macrophages: FcR for immunoglobulins, as well as CR1, CR3, CR4 for fragments of activated complement. Glycoprotein receptors for many cytokines are expressed on the macrophage membrane. The binding of a cytokine to its receptor serves as the first link in the chain of transmission of the activation signal to the cell nucleus.
Nonspecific defense mechanisms. Characteristic macro and microphages.
Nonspecific (innate) cellular defense mechanisms are provided by phagocytes: 1. macrophages (mononuclear cells). 2. microphages (polynuclear cells).
Phagocytes:
macrophages (mononuclear cells) (neutro-, zoeino-, basophils)
Monocytes
Phagocytes were discovered in 1882 by Mechnikov.
Macrophages are mononuclear cells and are formerly grouped into the mononuclear phagocytic system - red bone marrow monocytes, free tissue macrophages and fixed tissue macrophages. Red bone marrow monocytes are located in the center of the erythroblastic islet (undifferentiated cells) and give rise to all macrophages: red bone marrow monocytes exit the blood and exist there as blood monocytes (6-8% of blood lymphocytes). Blood monocytes are able to pass through the epithelium blood vessels tissues, where it turns into a macrophage. Macrophages do not return to the blood. If blood monocytes have a diameter of 11-20 nm. then tissue macrophages have sizes of 40-50 microns. That is, macrophages increase in size and are called prostrate macrophages, which can interact with lymphocytes. Receptors for interaction with IgG and complement are also formed on their surface. This interaction of macrophages with lo G and complements promotes phagocytosis.
Macrophages are divided into: 1. lung macrophages (alveolar). 2. connective tissue macrophages (histiocytes) 3. macrophages of serous cavities. 4. macrophages of inflammatory exudates.
Free macrophages are diffusely scattered throughout the body and move freely, which helps rid the body of foreign material. Spread out macrophages are able to stick together, creating congiamerates that create conditions (mechanical obstacles) for the spread of microorganisms. In addition, macrophages are APCs.
Tissue (associated) macrophages are part of identical organs: 1. liver macrophages (Kupffer cells) - with big amount processes, cleanse the blood flowing through portal vein from the intestines. Participate in the exchange of Hb and bile pigments. 2. macrophages of the spleen (located in the cortex and medulla) - have many processes, have phagocytic power, destroy old red blood cells. 3. macrophages of lymph nodes - located in the cortical and medulla, neutralize lymph microorganisms. 4. placental macrophages - protect the placenta from bacteria. 5. macrophages microgpy - phagocytose the breakdown products of nervous tissue and store fat.
All macrophages produce biologically active substances - cytokines that link the functions of macrophages together.
Microphages are polynuclear phagocytes, originating from red bone marrow stem cells, 2/3 consist of eutrophils, eosinophils up to 5%, basophils up to 1%. i
Neutrophils, eosinophils. basophils leave the bloodstream; into tissues and turn into microphages and do not return. The strongest neutrophils can destroy up to 30 bacteria. Their strength is assessed by phagocytic and bacterial activity and chemotactic properties. During infection, microphages rush from the bloodstream into the tissues, as the permeability of blood vessels for them increases. This is due to an increase in histamine during inflammatory processes. The second peak of permeability is 6-8 hours after penetration and is associated with action.
Monocyte-macrophage system) physiological defense system of cells that have the ability to absorb and digest foreign material. The cells that make up this system have a common origin, are characterized by morphological and functional similarity and are present in all tissues of the body. The basis of the modern idea of S. m. f. is the phagocytic theory developed by I.I. Mechnikov at the end of the 19th century, and the teaching of the German pathologist Aschoff (K. A. L. Aschoff) about the reticuloendothelial system (). Initially, the RES was identified morphologically as a system of body cells capable of accumulating the carmine dye. According to this criterion, connective tissue histiocytes, blood monocytes, liver Kupffer cells, as well as reticular cells of hematopoietic organs, endothelial cells of capillaries, bone marrow sinuses and lymph nodes were classified as RES. With the accumulation of new knowledge and the improvement of morphological research methods, it became clear that ideas about the reticuloendothelial system are vague, not specific, and in a number of positions are simply erroneous. For example, reticular cells and endothelium of the bone marrow sinuses and lymph nodes long time was attributed to the role of a source of phagocytic cells, which turned out to be incorrect. It has now been established that mononuclear phagocytes originate from circulating blood monocytes. Monocytes mature in the bone marrow, then enter the bloodstream, from where they migrate into tissues and serous cavities, becoming macrophages. Reticular cells perform a supporting function and create the so-called microenvironment for hematopoietic and lymphoid cells. Endothelial cells transport substances through the walls of capillaries. Reticular cells and blood vessels are not directly related to the protective system of cells. In 1969, at a conference in Leiden dedicated to the problem of RES, the concept of “” was declared obsolete. Instead, the concept “” has been adopted. This system includes connective tissue histiocytes, liver Kupffer cells (stellate reticuloendotheliocytes), alveolar macrophages of the lungs, macrophages of the lymph nodes, spleen, bone marrow, pleural and peritoneal macrophages, osteoclasts of bone tissue, microglia of nervous tissue, synoviocytes of synovial membranes, Langergais cells of the skin, pigmentless granular dendrocytes. There are free ones, i.e. moving through tissues, and fixed (resident) macrophages, having a relatively constant place. Macrophages of tissues and serous cavities, according to scanning electron microscopy, have a shape close to spherical, with an uneven folded surface formed plasma membrane(cytolemma). Under cultivation conditions, macrophages spread out on the surface of the substrate and acquire a flattened shape, and when moving, they form multiple polymorphic ones. A characteristic ultrastructural feature of a macrophage is the presence in its cytoplasm of numerous lysosomes and phagolysosomes, or digestive vacuoles ( rice. 1
). Lysosomes contain various hydrolytic substances that ensure the digestion of absorbed material. Macrophages are active secretory cells that release environment enzymes, inhibitors, complement components. The main secretory product of macrophages is. Activated macrophages secrete neutral (elastase, collagenase), plasminogen activators, complement factors such as C2, C3, C4, C5, as well as. Cells S. m. f. have a number of functions, which are based on their ability to endocytosis, i.e. absorption and digestion of foreign particles and colloidal liquids. Thanks to this, they perform a protective function. Through chemotaxis, macrophages migrate to sites of infection and inflammation, where they kill and digest microorganisms. In conditions of chronic inflammation, special forms of phagocytes can appear - epithelioid cells (for example, in an infectious granuloma), giant multinucleated cells of the Pirogov-Langhans cell type and the foreign cell type. which are formed by the fusion of individual phagocytes into a polykaryon - a multinucleated cell ( rice. 2
). In granulomas, macrophages produce the glycoprotein fibronectin, which attracts fibroblasts and promotes the development of sclerosis. Cells S. m. f. take part in immune processes. Thus, a prerequisite for the development of a directed immune response is the primary interaction of the macrophage with the antigen. At the same time, it is absorbed and processed by the macrophage into an immunogenic form. Immune lymphocytes occurs when they come into direct contact with a macrophage carrying the converted antigen. The immune response is carried out as a complex multi-stage interaction of G- and B-lymphocytes with macrophages. Macrophages have antitumor activity and exhibit cytotoxic properties against tumor cells. This is especially pronounced in the so-called immune macrophages, which target tumor cells upon contact with sensitized T-lymphocytes carrying cytophilic (). Cells S. m. f. take part in the regulation of myeloid and lymphoid hematopoiesis. Thus, hematopoietic islands in the red bone marrow, spleen, liver and yolk sac of the embryo are formed around a special cell - the central macrophage, which organizes the erythroblastic island. Kupffer cells of the liver are involved in the regulation of hematopoiesis by producing erythropoietin. Monocytes and macrophages produce factors that stimulate the production of monocytes, neutrophils and eosinophils. IN thymus gland(thymus) and thymus-dependent zones of lymphoid organs, so-called interdigitating cells were found - specific stromal elements, also related to S. m. f., responsible for the migration and differentiation of T lymphocytes. The metabolism of macrophages lies in their participation in the exchange. In the spleen and bone marrow, macrophages carry out iron accumulation in the form of hemosiderin and ferritin, which can then be reutilized by erythroblasts. Bibliography: Carr Ian. Macrophages: a review of ultrastructure and function. from English, M., 1978; Persina I.S. Langerhans cells - structure, function, role in pathology, . pathol., vol. 47, no. 2, p. 86, 1985.
1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First health care. - M.: Great Russian Encyclopedia. 1994 3. encyclopedic Dictionary medical terms. - M.: Soviet Encyclopedia. - 1982-1984.
See what the “mononuclear phagocyte system” is in other dictionaries:
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