The bacterial cell is capable of phagocytosis. Phagocytosis is the body's defender

17.05.2020

The protective role of mobile blood and tissue cells was first discovered by II Mechnikov in 1883. He called these cells phagocytes and formulated the main provisions of the phagocytic theory of immunity. Phagocytosis - absorption by phagocytes of large macromolecular complexes or corpuscles, bacteria. Phagocytic cells: neutrophils and monocytes / macrophages. Eosinophils can also phagocytose (most effective for anthelmintic immunity). The process of phagocytosis is enhanced by opsonins that envelop the phagocytosis object. Monocytes make up 5-10%, and neutrophils 60-70% of blood leukocytes. Entering the tissue, monocytes form a population of tissue macrophages: Kupffer's cells (or stellate reticuloendothelial cells of the liver), microglia of the central nervous system, osteoclasts of bone tissue, alveolar and interstitial macrophages).

Phagocytosis process... Phagocytes move in a directed direction to the phagocytosis object, reacting to chemoattractants: microbial substances, activated complement components (C5a, C3a) and cytokines.
The plasmalemma of the phagocyte encircles bacteria or other corpuscles and its own damaged cells. Then the object of phagocytosis is surrounded by a plasmalemma and the membrane vesicle (phagosome) is immersed in the cytoplasm of the phagocyte. The phagosome membrane fuses with the lysosome and the phagocytosed microbe is destroyed, pH is acidified to 4.5; enzymes of the lysosome are activated. The phagocytosed microbe is destroyed by the action of lysosomal enzymes, cationic defensin proteins, cathepsin G, lysozyme, and other factors. During an oxidative (respiratory) explosion in a phagocyte, toxic antimicrobial forms of oxygen are formed - hydrogen peroxide H 2 O 2, superosidanion O 2 -, hydroxyl radical OH -, singlet oxygen. In addition, nitric oxide and the NO - radical have an antimicrobial effect.
Macrophages perform a protective function even before interacting with other immunocompetent cells (non-specific resistance). Macrophage activation occurs after the destruction of the phagocytosed microbe, its processing (processing) and presentation (presentation) of the antigen to T-lymphocytes. In the final stage of the immune response, T-lymphocytes release cytokines that activate macrophages (acquired immunity). Activated macrophages, together with antibodies and activated complement (C3b), carry out more effective phagocytosis (immune phagocytosis), destroying phagocytosed microbes.

Phagocytosis can be complete, resulting in the death of the captured microbe, and incomplete, in which microbes do not die. An example of incomplete phagocytosis is phagocytosis of gonococci, tubercle bacilli and leishmanias.

All phagocytic cells of the body, according to II Mechnikov, are subdivided into macrophages and microphages. Microphages include polymorphonuclear granulocytes of blood: neutrophils, eosinophils, and basophils. Macrophages of various body tissues (connective tissue, liver, lungs, etc.), together with blood monocytes and their bone marrow precursors (promonocytes and monoblasts), are combined into a special system of mononuclear phagocytes (SMP). SMF is phylogenetically older than the immune system. It is formed in ontogeny early enough and has certain age characteristics.

Microphages and macrophages have a common myeloid origin - from a pluripotent stem cell, which is a single precursor of granulo- and monocytopoiesis. The peripheral blood contains more granulocytes (from 60 to 70% of all blood leukocytes) than monocytes (from 1 to 6%). At the same time, the duration of circulation of monocytes in the blood is much longer (half-period 22 hours) than that of short-lived granulocytes (half-period 6.5 hours). In contrast to blood granulocytes, which are mature cells, monocytes, leaving the bloodstream, mature into tissue macrophages in the corresponding microenvironment. The extravascular pool of mononuclear phagocytes is tens of times higher than their number in the blood. The liver, spleen, and lungs are especially rich in them.

All phagocytic cells are characterized by common basic functions, similarity of structures and metabolic processes. The outer plasma membrane of all phagocytes is an actively functioning structure. It is characterized by pronounced folding and carries many specific receptors and antigenic markers, which are constantly updated. Phagocytes are equipped with a highly developed lysosomal apparatus, which contains a rich arsenal of enzymes. The active participation of lysosomes in the functions of phagocytes is provided by the ability of their membranes to merge with the membranes of phagosomes or with the outer membrane. In the latter case, cell degranulation occurs and the concomitant secretion of lysosomal enzymes into the extracellular space occurs.

Phagocytes have three functions:

1 - protective, associated with cleaning the body from infectious agents, tissue decay products, etc.;

2 - representing, consisting in the presentation of antigenic epitopes on the membrane of a phagocyte;

3 - secretory, associated with the secretion of lysosomal enzymes and other biologically active substances - monokines that play an important role in immunogenesis.

Fig 1. Functions of the macrophage.

In accordance with the listed functions, the following sequential stages of phagocytosis are distinguished.

1. Chemotaxis - the targeted movement of phagocytes in the direction of the chemical gradient of chemoattractants in the environment. The ability to chemotaxis is associated with the presence on the membrane of specific receptors for chemoattractants, which can be bacterial components, degradation products of body tissues, activated fractions of the complement system - C5a, C3a, lymphocyte products - lymphokines.

2. Adhesion (attachment) is also mediated by the corresponding receptors, but can proceed in accordance with the laws of nonspecific physical and chemical interaction. Adhesion immediately precedes endocytosis (capture).

3. Endocytosis is the main physiological function of the so-called professional phagocytes. Distinguish phagocytosis - in relation to particles with a diameter of at least 0.1 microns and pinocytosis - in relation to smaller particles and molecules. Phagocytic cells are able to capture inert particles of coal, carmine, latex, flowing around them with pseudopodia without the participation of specific receptors. At the same time, phagocytosis of many bacteria, yeast-like fungi of the genus Candida and other microorganisms is mediated by special mannosofucose receptors of phagocytes, which recognize the carbohydrate components of the surface structures of microorganisms. The most effective is receptor-mediated phagocytosis for the Fc-fragment of immunoglobulins and for the C3-complement fraction. Such phagocytosis is called immune, since it proceeds with the participation of specific antibodies and an activated complement system, which opsonize the microorganism. This makes the cell highly sensitive to capture by phagocytes and leads to subsequent intracellular death and degradation. As a result of endocytosis, a phagocytic vacuole is formed - a phagosome. It should be emphasized that endocytosis of microorganisms largely depends on their pathogenicity. Only avirulent or low-virulent bacteria (capsule-free pneumococcal strains, streptococcal strains devoid of hyaluronic acid and M-protein) are phagocytosed directly. Most bacteria endowed with aggressive factors (staphylococci - A-protein, Escherichia coli - a pronounced capsular antigen, Salmonella - Vi-antigen, etc.), phagocytose, only after their opsonization with complement and / or antibodies.

The presentational, or representing, function of macrophages is to fix antigenic epitopes of microorganisms on the outer membrane. In this form, they are represented by macrophages for their specific recognition by cells of the immune system - T-lymphocytes.

The secretory function is the secretion of biologically active substances - monokines by mononuclear phagocytes. These include substances that have a regulatory effect on the proliferation, differentiation and function of phagocytes, lymphocytes, fibroblasts and other cells. A special place among them is occupied by interleukin-1 (IL-1), which is secreted by macrophages. It activates many functions of T-lymphocytes, including the production of lymphokine - interleukin-2 (IL-2). IL-1 and IL-2 are cellular mediators involved in the regulation of immunogenesis and various forms of the immune response. At the same time, IL-1 has the properties of an endogenous pyrogen, since it induces fever by acting on the nuclei of the anterior hypothalamus. Macrophages produce and secrete such important regulatory factors as prostaglandins, leukotrienes, cyclic nucleotides with wide range biological activity.

Along with this, phagocytes synthesize and secrete a number of products with predominantly effector activity: antibacterial, antiviral and cytotoxic. These include oxygen radicals (O 2, H 2 O 2), complement components, lysozyme and other lysosomal enzymes, interferon. Due to these factors, phagocytes can kill bacteria not only in phagolysosomes, but also outside the cells, in the immediate microenvironment. These secretory products can also be mediated by the cytotoxic effect of phagocytes on various target cells in cell-mediated immune responses, for example, in delayed-type hypersensitivity (HRT) reactions, in the rejection of homografts, in antitumor immunity.

The considered functions of phagocytic cells ensure their active participation in maintaining the body's homeostasis, in the processes of inflammation and regeneration, in nonspecific anti-infectious defense, as well as in immunogenesis and reactions of specific cellular immunity (HRT). The early involvement of phagocytic cells (first - granulocytes, then - macrophages) in response to any infection or any damage is explained by the fact that microorganisms, their components, tissue necrosis products, blood serum proteins, substances secreted by other cells are chemoattractants for phagocytes. In the focus of inflammation, activation of the functions of phagocytes occurs. Macrophages are replacing microphages. In cases where the inflammatory reaction involving phagocytes is not enough to cleanse the body of pathogens, then the secretory products of macrophages ensure the involvement of lymphocytes and the induction of a specific immune response.

Complement system.The complement system is a multicomponent self-assembling system of serum proteins, which plays an important role in maintaining homeostasis. It is capable of being activated in the process of self-assembly, that is, the sequential attachment of individual proteins to the resulting complex, which are called components, or complement fractions. There are nine such factions. They are produced by liver cells, mononuclear phagocytes and are contained in the blood serum in an inactive state. The complement activation process can be triggered (initiated) in two different ways, called the classic and alternative.

When complement is activated in the classical way, the initiating factor is the antigen-antibody complex (immune complex). Moreover, antibodies of only two classes IgG and IgM in the composition of immune complexes can initiate the activation of complement due to the presence in the structure of their Fc-fragments of sites that bind the C1-complement fraction. When C1 attaches to the antigen-antibody complex, an enzyme (C1-esterase) is formed, under the action of which an enzymatically active complex (C4b, C2a), called C3-convertase, is formed. This enzyme cleaves C3 into C3a and C3b. When the C3b subfraction interacts with C4 and C2, a peptidase is formed that acts on C5. If the initiating immune complex is associated with the cell membrane, then the self-assembling complex C1, C4, C2, C3 ensures the fixation of the activated fraction C5, and then C6 and C7 on it. The last three components together contribute to the fixation of C8 and C9. In this case, two sets of complement fractions - C5a, C6, C7, C8, and C9 - constitute a membrane-attacking complex, after which it is attached to the cell membrane, the cell is lysed due to irreversible damage to the structure of its membrane. In the event that the activation of complement along the classical pathway occurs with the participation of the immune complex erythrocyte - anti-erythrocyte Ig, hemolysis of erythrocytes occurs; if the immune complex consists of bacteria and antibacterial Ig, bacterial lysis occurs (bacteriolysis).

Thus, upon activation of complement in the classical way, the key components are C1 and C3, the cleavage product of which C3b activates the terminal components of the membrane attack complex (C5 - C9).

There is a possibility of C3 activation with the formation of C3b with the participation of C3-convertase of the alternative pathway, i.e., bypassing the first three components: C1, C4, and C2. A feature of the alternative pathway of complement activation is that initiation can occur without the participation of an antigen-antibody complex due to polysaccharides of bacterial origin - lipopolysaccharide (LPS) of the cell wall of gram-negative bacteria, surface structures of viruses, immune complexes, including IgA and IgE.

Phagocytosis (Phago - devour and cytos - cell) is a process in which special cells of the blood and body tissues (phagocytes) capture and digest infectious agents and dead cells.

It is carried out by two types of cells: granular leukocytes (granulocytes) circulating in the blood and tissue macrophages. The discovery of phagocytosis belongs to II Mechnikov, who revealed this process by doing experiments with starfish and daphnia, introducing foreign bodies into their organisms. For example, when Mechnikov placed a spore of a fungus in the body of a daphnia, he noticed that it was attacked by special mobile cells. When he introduced too many spores, the cells did not have time to digest them all, and the animal died. The cells that protect the body from bacteria, viruses, fungal spores, etc. Mechnikov called phagocytes.

Phagocytosis, the process of active capture and absorption of living and non-living particles by unicellular organisms or special cells (phagocytes) of multicellular animal organisms. The phenomenon of F. was discovered by I. I. Mechnikov, who traced its evolution and clarified the role of this process in the protective reactions of the organism of higher animals and humans, mainly in inflammation and immunity. F. plays an important role in wound healing. The ability to capture and digest particles is at the core of the nutrition of primitive organisms. In the course of evolution, this ability gradually passed to individual specialized cells, first digestive, and then to special cells of the connective tissue. In humans and mammals, active phagocytes are neutrophils (microphages, or special leukocytes) of the blood and cells of the reticuloendothelial system, which are capable of transforming into active macrophages. Neutrophils phagocytose small particles (bacteria, etc.), macrophages are able to absorb larger particles (dead cells, their nuclei or fragments, etc.). Macrophages are also capable of accumulating negatively charged particles of dyes and colloidal substances. The absorption of small colloidal particles is called ultraphagocytosis, or colloidopexy.

The greatest ability to phagocytosis is possessed by neutrophils and monocytes

1. Neutrophils are the first to enter the inflammation focus and phagocytose microbes. In addition, lysosomal enzymes of disintegrating neutrophils soften the surrounding tissues and form a purulent focus.

2.Monocytes, migrating to tissues, turn into macrophages and phagocytose everything that is in the focus of inflammation: microbes, destroyed leukocytes, damaged cells and tissues of the body, etc. In addition, they enhance the synthesis of enzymes that promote the formation of fibrous tissue at the site of inflammation, and thus promote wound healing.

The phagocyte picks up individual signals (chemotaxis) and migrates towards them (chemokinesis). The mobility of leukocytes is manifested in the presence of special substances (chemoattractants). Chemoattractants interact with specific neutrophil receptors. As a result of the interaction of actin myosin, the pseudopodia are advanced and the phagocyte moves. Moving in this way, the leukocyte penetrates the capillary wall, leaves the tissue and contacts the phagocytosed object. As soon as the ligand interacts with the receptor, the conformation of the latter (this receptor) sets in and the signal is transmitted to the enzyme associated with the receptor into a single complex. Due to this, the phagocytosed object is absorbed and merged with the lysosome. In this case, the phagocytosed object either dies ( complete phagocytosis), or continues to live and develop in the phagocyte ( incomplete phagocytosis).

The last stage of phagocytosis is the destruction of the ligand. At the moment of contact with the phagocytosed object, activation of membrane enzymes (oxidases) occurs, oxidative processes inside the phagolysosomes are sharply increased, as a result of which the death of bacteria occurs.

Neutrophil function. Neutrophils are in the blood for only a few hours (in transit from the bone marrow into the tissue), and their functions are performed outside the vascular bed (exit from the vascular bed occurs as a result of chemotaxis) and only after the activation of neutrophils. The main function is phagocytosis of tissue debris and the destruction of opsonized microorganisms (opsonization is the attachment of antibodies or complement proteins to the wall of a bacterial cell, which makes it possible to recognize this bacterium and phagocytose). Phagocytosis is carried out in several stages. After preliminary specific recognition of the material subject to phagocytosis, invagination of the neutrophil membrane around the particle and the formation of a phagosome occurs. Further, as a result of the fusion of the phagosome with lysosomes, a phagolysosome is formed, after which the bacteria are destroyed and the captured material is destroyed. To do this, the phagolysosome receives: lysozyme, cathepsin, elastase, lactoferrin, defensins, cationic proteins; myeloperoxidase; superoxide О 2 - and hydroxyl radical ОН -, formed (along with Н 2 О 2) during respiratory explosion. Respiratory burst: Neutrophils sharply increase oxygen uptake during the first seconds after stimulation and quickly consume a significant amount of it. This phenomenon is known as respiratory (oxygen) explosion... In this case, H 2 O 2, toxic to microorganisms, are formed, superoxide O 2 - and hydroxyl radical OH -. After a single outbreak of activity, the neutrophil dies. Such neutrophils make up the main component of pus ("purulent" cells).

Basophil function. The activated basophils leave the bloodstream and are involved in allergic reactions in tissues. Basophils have highly sensitive surface receptors for IgE fragments that plasma cells synthesize when antigens enter the body. After interaction with immunoglobulin, degranulation of basophils occurs. The release of histamine and other vasoactive factors during degranulation and oxidation of arachidonic acid cause the development of an immediate allergic reaction (such reactions are characteristic of allergic rhinitis, some forms of bronchial asthma, anaphylactic shock).

Macrophage is a differentiated form of monocytes - large (about 20 microns), mobile cell of the mononuclear phagocyte system. Macrophages - professional phagocytes, they are found in all tissues and organs, it is a mobile population of cells. The life span of macrophages is months. Macrophages are subdivided into resident and motile ones. Resident macrophages are normally present in tissues in the absence of inflammation. Macrophages capture denatured proteins from the blood, aged red blood cells (fixed macrophages of the liver, spleen, bone marrow). Macrophages phagocytose debris of cells and tissue matrix. Nonspecific phagocytosis characteristic of alveolar macrophages, capturing dust particles of various nature, soot, etc. Specific phagocytosis occurs when macrophages interact with opsonized bacteria.

The macrophage, in addition to phagocytosis, performs an extremely important function: it is an antigen-presenting cell. Antigen-presenting cells, in addition to macrophages, include dendritic cells of the lymph nodes and spleen, Langerhans cells of the epidermis, M cells in lymphatic follicles digestive tract, dendritic epithelial cells of the thymus. These cells capture, process (process) and present Ag on their surface to helper T lymphocytes, which leads to the stimulation of lymphocytes and the launch of immune reactions. IL1 from macrophages activates T-lymphocytes and, to a lesser extent, B-lymphocytes.

Phagocytosis

In 1882-1883. the famous Russian zoologist I. I. Mechnikov conducted his research in Italy, on the shores of the Strait of Messina. The scientist was interested in whether individual cells of multicellular organisms retained the ability to capture and digest food, as unicellular organisms, such as amoeba, do. Indeed, as a rule, in multicellular organisms, food is digested in the alimentary canal and the cells absorb ready-made nutrient solutions. Mechnikov observed the larvae of sea stars. They are transparent and their contents are clearly visible. These larvae do not have circulating blood, but there are cells wandering throughout the larva. They captured particles of the red carmine dye introduced into the larva. But if these cells absorb paint, then maybe they capture any foreign particles? Indeed, the thorns of the rose inserted into the larva turned out to be surrounded by cells stained with carmine.

The cells were able to capture and digest any foreign particles, including pathogenic microbes. Mechnikov called the wandering cells phagocytes (from the Greek words phages - devourer and kytos - container, here - cell). And the very process of capture and digestion of different particles by them is phagocytosis. Later, Mechnikov observed phagocytosis in crustaceans, frogs, turtles, lizards, as well as in mammals - guinea pigs, rabbits, rats and humans.

Phagocytes are special cells. They need to digest the captured particles not for nutrition, like amoeba and other unicellular organisms, but to protect the body. In the larvae of sea stars, phagocytes wander throughout the body, and in higher animals and in humans, they circulate in the vessels. This is a type of white blood cell, or leukocyte, called neutrophils. It is they, attracted by the toxic substances of microbes, that move to the place of infection (see Taxis). Coming out of the vessels, such leukocytes have outgrowths - pseudopods, or pseudopodia, with the help of which they move in the same way as the amoeba and the wandering cells of the larvae of starfish. Such leukocytes capable of phagocytosis were called microphages by Mechnikov.

However, not only constantly moving leukocytes, but also some sedentary cells can become phagocytes (now they are all combined into unified system phagocytic mononuclear cells). Some of them rush to dangerous areas, for example, to the site of inflammation, while others remain in their usual places. Both those and others are united by the ability to phagocytosis. These tissue cells (histocytes, monocytes, reticular and endothelial cells) are almost twice as large as microphages - their diameter is 12–20 µm. Therefore, Mechnikov called them macrophages. There are especially many of them in the spleen, liver, lymph nodes, bone marrow and in the walls of blood vessels.

Microphages and wandering macrophages themselves actively attack "enemies", and immobile macrophages wait for the "enemy" to swim past them in the blood or lymph flow. Phagocytes "hunt" for microbes in the body. It happens that in an unequal struggle with them, they are defeated. Pus is the accumulation of dead phagocytes. Other phagocytes will approach it and begin to engage in its elimination, as they do with all sorts of foreign particles.

Phagocytes cleanse tissues of constantly dying cells and participate in various restructuring of the body. For example, when a tadpole transforms into a frog, when, along with other changes, the tail gradually disappears, whole hordes of phagocytes destroy the tissues of the tadpole's tail.

How do particles get inside the phagocyte? It turns out, with the help of pseudopodia, which grab them, like an excavator bucket. Gradually, the pseudopodia lengthen and then close over the foreign body. Sometimes it seems to be pressed into the phagocyte.

Mechnikov assumed that phagocytes should contain special substances that digest the microbes and other particles captured by them. Indeed, such particles - lysosomes - were discovered 70 years after the discovery of phagocytosis. They contain enzymes that can break down large organic molecules.

It has now been found that, in addition to phagocytosis, antibodies are predominantly involved in the neutralization of foreign substances (see Antigen and Antibody). But for the process of their production to begin, the participation of macrophages is necessary. They grab foreign proteins (antigens), cut them into pieces, and expose pieces of them (called antigenic determinants) on their surface. Here, those lymphocytes that are capable of producing antibodies (immunoglobulin proteins) that bind these determinants come into contact with them. After that, such lymphocytes multiply and secrete many antibodies into the blood, which inactivate (bind) foreign proteins - antigens (see Immunity). These issues are dealt with by the science of immunology, one of the founders of which was II Mechnikov.

ability to phagocytosis

Russian-English dictionary of biological terms. - Novosibirsk: Institute of Clinical Immunology. IN AND. Seledtsov. 1993-1999.

See what the "ability to phagocytosis" is in other dictionaries:

Immunity - I Immunity (lat. Immunitas release, getting rid of something) the body's immunity to various infectious agents (viruses, bacteria, fungi, protozoa, helminths) and their metabolic products, as well as to tissues and substances ... ... Medical encyclopedia

Hemopoiesis - I Hemopoiesis (synonymous with hematopoiesis) is a process that consists of a series of cell differentiations, as a result of which mature blood cells are formed. In the adult body, there are ancestral hematopoietic, or stem, cells. Supposed ... ... Medical Encyclopedia

Primary immunodeficiencies are immunodeficiency states hereditary or acquired in the prenatal period. They usually appear either immediately after birth or during the first two years of life (congenital immunodeficiencies). However, less pronounced genetic defects ... ... Wikipedia

INFECTION - INFECTION. Contents: History. 633 Characteristics of infections. 634 Sources I. 635 Methods of transmission of I. 636 Congenital I. 640 Various degrees of virulence of microbes. ... ... Great Medical Encyclopedia

MACROPHAGES - (from the Greek. Makros: big and phago eat), vulture. megalophages, macrophagocytes, large phagocytes. M.'s term is offered by Mechnikov, who divided all cells capable of phagocytosis into small phagocytes, microphages (see), and large phagocytes, macrophages. Under ... ... Great Medical Encyclopedia

TUMORS - TUMORS. Contents: I. Distribution of O. in the animal kingdom. ... .44 6 II. Statistics 0.44 7 III. Structural and fnkts. characteristic. 449 IV. Pathogenesis and etiology. 469 V. Classification and nomenclature. 478 VІ. ... ... Great Medical Encyclopedia

LEUKOCYTES - (from the Greek. Leukos white and kytos cell), white, or colorless little bodies, one of the types of blood cells along with erythrocytes and platelets. The term "leukocyte" is used in a double sense: 1) to refer to all ... ... Great Medical Encyclopedia

Monocyte - (from the Greek μονος "one" and κύτος "receptacle", "cell") a large mature mononuclear leukocyte of a group of agranulocytes with a diameter of ... Wikipedia

A CELL is an elementary living unit. A cell is separated from other cells or from the external environment by a special membrane and has a nucleus or its equivalent, in which the bulk of the chemical information that controls heredity is concentrated. Studying ... ... Collier's Encyclopedia

Antigen Presentation - Antigen Presentation. Above: a foreign antigen (1) captures and absorbs the antigen by a presenting cell (2), which cleaves it and partially exposes it on its surface in a complex with MHC II molecules (... Wikipedia

Endothelium - (from Endo. And Greek thele nipple) specialized cells of animals and humans, lining the inner surface of blood and lymphatic vessels, as well as heart cavities. E. is formed from the mesenchyme (See Mesenchyme). Presented by ... ... Great Soviet Encyclopedia

We use cookies to give you the best experience on our website. By continuing to use this site, you agree to this. Good

Phagocytosis

One of the most important functions of leukocytes released from the vessels into the focus of inflammation is phagocytosis, during which leukocytes recognize, absorb and destroy microorganisms that have entered the body, various foreign particles, as well as their own non-viable cells and tissues.

Not all leukocytes released into the focus of inflammation are capable of phagocytosis. This ability is characteristic of neutrophils, monocytes, macrophages and eosinophils, which are referred to as the so-called professional, or obligatory (obligatory) phagocytes.

In the process of phagocytosis, several stages are distinguished:

1) the stage of adhesion (or attachment) of the phagocyte to the object,

2) the stage of absorption of the object and

3) the stage of intracellular destruction of the absorbed object. The adhesion of phagocytes to an object in some cases is due to

the existence of receptors on the phagocyte membrane for molecules that make up the microbial wall (for example, for the carbohydrate zymosan), or for molecules that appear on the surface of their own dying cells. However, in most cases, the adhesion of phagocytes to microorganisms that have entered the body is carried out with the participation of so-called opsonins - serum factors that enter the focus of inflammation as part of the inflammatory exudate. Opsonins bind to the surface of the cell of the microorganism, after which the phagocyte membrane easily adheres to it. The main opsonins are immunoglobulins and a C3b complement fragment. Some plasma proteins (for example, C-reactive protein) and lysozyme also have the properties of opsonins.

The phenomenon of opsonization can be explained by the fact that the molecules of opsonins have at least two regions, one of which binds to the surface of the attacked particle, and the other to the membrane of the phagocyte, thus connecting both surfaces to each other. Immunoglobulins of class B, for example, bind with their Pab-fragments to the antigens of the microbial surface, while the Pc-fragments of these antibodies - with the surface membrane of phagocytes, on which there are receptors for the Pc-fragments of the danyon, "taking" an electron from the reduced pyridine nucleotide NADPH:

202 + NADPH -\u003e 202- + NADP + + H +.

The reserves of NADPH consumed during the "respiratory burst" begin to be immediately replenished by enhanced oxidation of glucose through the hexose-monophosphate shunt.

Most of the 02_ superoxide anions formed during the reduction of 02 undergo dismutation to H2O2:

Some of the H2O2 molecules interact in the presence of iron or copper with the superoxide anion to form an extremely active hydroxyl radical OH:

Cytoplasmic NADPH oxidase is activated at the site of contact between the phagocyte and the microbe, and the formation of superoxide anions occurs on the outer side of the leukocyte membrane, outside the inner cell environment. The process continues after the completion of the formation of the phagosome, as a result of which a high concentration of bactericidal radicals is created inside it. The radicals penetrating into the cytoplasm of the phagocyte are neutralized by the enzymes superoxide dismutase and catalase.

The system of formation of bactericidal oxygen metabolites operates in all professional phagocytes. In neutrophils, another powerful bactericidal system acts in conjunction with it - the myeloleroxidase system (eosinophils also have a similar neuleroxidase system, but monocytes and macrophages do not).

myeloperoxidase C1- + H202 * OC1

Hypochlorite has a pronounced bactericidal effect by itself. In addition, it can react with ammonium or amines to form bactericidal chloramines.

The bactericidal mechanism independent of oxygen is associated with degranulation - the entry of bactericidal substances into the phagosome, which are contained in the intracellular granules of phagocytes.

When the formation of a phagosome is completed, the granules of the cytoplasm of phagocytes come close to it. The granule membrane fuses with the phagosome membrane, and the contents of the granules are poured into the phagosome. It is believed that the stimulus to degranulation is an increase in cytosolic Ca2 +, the concentration of which increases especially strongly near the phagosome, where the organelles that accumulate calcium are located.

Cytoplasmic granules of all obligate phagocytes contain a large amount of biologically active substances capable of killing and digesting microorganisms and other objects absorbed by phagocytes. In neutrophils, for example, there are 3 types of granules:

Secondary (specific) granules.

The most easily mobilized secretory vesicles facilitate the release of neutrophils from the vessels, their migration in tissues. The absorbed particles of the substance of azurophilic and specific granules are destroyed and destroyed. In addition to the already mentioned myeloperoxidase, azurophilic granules contain low molecular weight bactericidal peptides defensins, weak bactericidal substance lysozyme, and many destructive enzymes acting independently of oxygen; in specific granules, lysozyme and proteins that stop the reproduction of microorganisms, in particular, lactoferrin, which binds iron necessary for the life of microorganisms.

The inner membrane of specific and azurophilic granules contains proton pump, which transfers hydrogen ions from the cytoplasm of the phagocyte into the phagosome. As a result, the pH of the medium in the phagosome drops to 4-5, which causes the death of many microorganisms inside the phagosome. After the microorganisms die, they are destroyed inside the phagosome using acid hydrolases of azurophilic granules.

Forming peroxynitrite, which breaks down into cytotoxic free radicals OH * and NO ".

Not all living microorganisms die inside phagocytes. Some, for example, the causative agents of tuberculosis persist, while being “fenced off” by the membrane and cytoplasm of phagocytes from antimicrobial drugs.

Phagocytes activated by chemoattractants are able to release the contents of their granules not only into the phagosome, but also into the extracellular space. This occurs during the so-called incomplete phagocytosis - in cases when, for some reason or other reasons, the phagocyte cannot absorb the attacked object, for example, if the size of the latter significantly exceeds the size of the phagocyte itself or if the object of phagocytosis is antigen-antibody complexes located on the flat surface of the vascular endothelium. In this case, the contents of the granules and the active oxygen metabolites produced by phagocytes affect both the target of attack and the tissues of the host organism.

Damage to host tissues by toxic products of phagocytes becomes possible not only as a result of incomplete phagocytosis, but also after the death of leukocytes or as a result of destruction of the phagosome membrane by the absorbed particles themselves, for example, silicon particles or uric acid crystals.

Phagocytosis is the body's defender

Phagocytosis is the body's defense mechanism that absorbs particulate matter. In the process of destruction of harmful substances, slags, toxins, decomposition waste are removed. Active cells are capable of calculating foreign tissue inclusions. They begin to quickly attack the aggressor, splitting it into the simplest particles.

The essence of the phenomenon

Phagocytosis is a defense against pathogens. Domestic scientist Mechnikov I.I. conducted experiments to study the phenomenon. He introduced into the body of starfish and daphnia foreign inclusions and recorded the results of observations.

Phagocytosis stages were recorded through microscopic examination of marine life. Spores of fungi were used as a causative agent. Placing them in the tissues of a starfish, the scientist noticed the movement of active cells. Moving particles attacked over and over again until they completely covered the foreign body.

However, after exceeding the amount of harmful components, the animal was unable to resist and died. Protective cells are given the name phagocytes, which consists of two Greek words: devour and cell.

Active particles of the defense mechanism

The action of leukocytes and macrophages is isolated as a result of phagocytosis. These are not the only cells that guard the health of the body; in animals, oocytes, placental "guards", act as active particles.

The phagocytosis phenomenon is carried out by two protective cells:

Neutrophils - created in the bone marrow. They belong to granulocytic blood particles, the structure of which is distinguished by its granularity.
Monocytes are a type of leukocytes that are released from the bone marrow. Young phagocytes are highly mobile and form the main protective barrier.

Selective protection

Phagocytosis is an active defense of the body, in which only pathogenic cells are destroyed, useful particles pass the barrier without complications. To analyze the state of human health, a quantitative assessment is used by laboratory blood tests. An increased concentration of leukocytes indicates an ongoing inflammatory process.

Phagocytosis is a protective barrier against a huge number of pathogens:

bacteria;
viruses;
blood clots;
tumor cells;
fungal spore;
toxins and slag inclusions.

The leukocyte counts periodically change, the correct conclusions are drawn after several general blood tests. So, in pregnant women, the amount is slightly overestimated, and this is a normal state of the body.

Low rates of phagocytosis are observed with long-term chronic diseases:

tuberculosis;
pyelonephritis;
respiratory tract infections;
rheumatism;
atopic dermatitis.

The activity of phagocytes changes under the influence of certain substances:

Avitominosis, the use of antibiotics, corticosteroids inhibit the defense mechanism. Phagocytosis acts as an assistant to the immune system. Forced activation occurs in three ways:

Classic - carried out according to the antigen-antibody principle. The activators are IgG, IgM immunoglobulins.
Alternative - polysaccharides, viral particles, tumor cells are used.
Lectin - a group of proteins that pass through the liver is used.

Particle Destruction Sequence

To understand the process of the protective mechanism, the stages of phagocytosis are determined:

Chemotaxis is the period of penetration of a foreign particle into the human body. It is characterized by an abundant release of a chemical reagent that serves as a signal for activity for macrophages, neutrophils, and monocytes. Human immunity directly depends on the activity of protective cells. All awakened cells attack the area of \u200b\u200bintroduction of a foreign body.
Adhesion - recognition foreign body due to receptors by phagocytes.
The preparatory process of defense cells to attack.
Absorption - particles gradually cover the foreign substance with their membrane.
Phagosome formation is the completion of the membrane surrounding the foreign body.
Phagolysosome creation - Digestive enzymes are released into the capsule.
Killing - killing harmful particles.
Removal of residues of particle splitting.

The stages of phagocytosis are considered by medicine to understand the internal processes of the development of any disease. The doctor must understand the basics of the phenomenon to diagnose inflammation.

The ability to phagocytosis

in English language.

in mathematics and Russian

from school 162 of the Kirovsky district of St. Petersburg.

Establish a correspondence between the type of cells and its ability to phagocytosis.

The ciliates are fed as follows. On one side of the body of the shoe there is a funnel-shaped depression leading to the mouth and tubular pharynx. With the help of the cilia lining the funnel, food particles (bacteria, unicellular algae, detritus) are driven into the mouth and then into the pharynx. From the pharynx, food enters the cytoplasm by phagocytosis. The resulting digestive vacuole is picked up by the circular flow of the cytoplasm. Within 1-1.5 hours, food is digested, absorbed into the cytoplasm, and undigested residues through the hole in the pellicle - powder - are removed to the outside.

Phagocytosis - active capture and absorption of foreign living objects (bacteria, cell fragments) and solid particles by unicellular organisms or cells of multicellular animals. Plants and fungi are not capable of this, since they have rigid cell walls in their cells. Chlorella and chlamydomonas are plants, they feed autotrophically, mucor is a fungus, and absorbs solutes.

According to your explanation, mushrooms are not capable of phagocytosis. But the task says that mucor is capable of phagocytosis, and mucor is a mushroom.

Where in the assignment does it say that mucor is capable of phagocytosis? It has a rigid cell wall. It cannot reshape to capture solid particles. Mucor feeds by absorption.

The ciliate cell is covered with a pellicle, it has a cell mouth. How is she capable of phagocytosis?

I understood correctly, the cell mouth of the ciliate, is this a site intended for phagocytosis?

The entry of water into the plant cell occurs in the process

Osmosis is the diffusion of a substance, usually a solvent, through a semipermeable membrane separating a solution and a pure solvent or two solutions of different concentrations.

Plant cells cannot have phagocytosis and pinocytosis due to the cell wall.

Phagocytosis is a process of active capture and absorption of living and non-living particles.

Active transport is the transfer of a substance through a cell or intracellular membrane or through a layer of cells flowing against a concentration gradient from a region of low concentration to a region of high

Phagocytosis is the absorption of solid food particles by the cell. An example of phagocytosis is the capture of bacteria and viruses by leukocytes.

The amoeba digestive vacuole is formed as a result

Phagocytosis, the process of active capture and absorption of living and non-living particles by unicellular organisms or special cells (phagocytes) of multicellular animal organisms.

In an amoeba, several pseudopods can form simultaneously, and then they surround food - bacteria, algae, other protozoa (phagocytosis).

Digestive juice is secreted from the cytoplasm surrounding the prey. A bubble is formed - a digestive vacuole.

and pinocytosis of an amoeba is not peculiar?

The digestive vacuole is a membrane vesicle with a particle inside - i.e. phagocytosis

The supply of nutrients by phagocytosis occurs in the cells

Phagocytosis is the capture of solid food particles by a cell. Typical for animal cells, they do not have cell walls, the membrane is plastic and capable of capturing particles.

The ability of the plasma membrane to surround a solid food particle and move it inside the cell is at the heart of the process

The ability of the plasma membrane to surround liquid droplets and move it inside the cell underlies the process

Phagocytosis is the capture of a solid particle, diffusion is a directed process of transfer of substance molecules in solution along a concentration gradient through the membrane, osmosis is the selective permeability of water molecules through the membrane until the concentration is equalized on both sides of the membrane. Pinocytosis is the capture of a liquid particle.

As a result of what process lipids are oxidized?

Phagocytosis is the capture of solid particles by a cell. In the process of photosynthesis and chemosynthesis, organic matter is formed. Oxidation of organic substances occurs in the energy process.

Find errors in the text provided, correct them, and explain your corrections.

1) In 1883, IP Pavlov reported about the phenomenon of phagocytosis, which he discovered, which underlies cellular immunity.

2) Immunity is the body's immunity to infections and foreign substances - antibodies.

3) Immunity can be specific and non-specific.

4) Specific immunity is the body's response to the action of unknown foreign agents.

5) Non-specific immunity provides the body with protection only against antigens known to the body.

1) 1 - the phenomenon of phagocytosis was discovered by II Mechnikov;

2) 2 - foreign substances are not antibodies, but antigens;

3) 4 - specific immunity is developed in response to the penetration of a known, specific antigen;

4) 5 - nonspecific immunity can occur in response to the penetration of any antigen.

there should be 3 answers, not 4.

Read the explanations carefully before assignments.

“Find three mistakes in the above text. Indicate the numbers of the proposals in which they are made, correct them. »Then you are right.

If “Find mistakes in the text provided, correct them and explain your corrections” (without specifying the number), then there may be several mistakes in one sentence, or more than three mistakes.

Establish a correspondence between the characteristics of human blood cells and their type.

A) transport oxygen and carbon dioxide

B) provide the body's immunity

C) determine the blood group

D) form pseudopods

D) are capable of phagocytosis

E) in 1 μl 5 million cells

Leukocytes are capable of amoeboid movement, with the help of pseudopods, they capture bacteria, that is, they are capable of phagocytosis, and provide immune protection. The rest of the signs are characteristic of erythrocytes.

do erythrocytes provide the body's immunity?

Not. Immunity is the function of leukocytes. The answer says so.

Phagocytosis is a process in which specially designed cells in the blood and body tissues (leukocytes \u003d phagocytes) capture and digest particulate matter.

The process of absorption of liquid by a cell is

Phagocytosis is a process of active capture and absorption of living and non-living particles by unicellular organisms or special cells (phagocytes) of multicellular animal organisms.

Cytokinesis is the division of the body of a eukaryotic cell. Cytokinesis usually occurs after a cell has undergone nuclear division (karyokinesis) during mitosis or meiosis.

Pinocytosis is the capture by the cell surface of the fluid containing the substances it contains.

Autolysis - self-digestion of tissues of animals, plants and microorganisms.

Establish a correspondence between the sign of blood cells and their type.

A) participate in the formation of fibrin

B) provide the process of phagocytosis

D) transport carbon dioxide

E) play an important role in immune responses

Write down the numbers in the answer, arranging them in the order corresponding to the letters:

Erythrocytes, red biconcave non-nuclear blood cells containing hemoglobin; transport oxygen from the respiratory system to the tissues and participate in the transfer of carbon dioxide in the opposite direction. Determines the red color of the blood.

Leukocytes (colorless cells, shapeless with a nucleus) are very diverse in size and function; participate in the protective function of the blood.

Platelets and the platelets corresponding to them in mammals and humans provide blood clotting.

Erythrocytes: contain hemoglobin, transport carbon dioxide. Leukocytes: provide the process of phagocytosis, play an important role in immune responses. Platelets: are involved in the formation of fibrin.

The destruction of bacteria, viruses and foreign substances that have entered the human body through their capture by leukocytes is a process

Phagocytosis is a process in which specially designed cells of the blood and body tissues (phagocytes) capture and digest particulate matter.

The inflammatory process when pathogenic bacteria enter the human skin is accompanied by

1) an increase in the number of leukocytes in the blood

2) blood clotting

3) expansion blood vessels

4) active phagocytosis

5) the formation of oxyhemoglobin

6) increased blood pressure

The inflammatory process when pathogenic bacteria enter the human skin is accompanied by an increase in the number of leukocytes in the blood, dilation of blood vessels (redness of the site of inflammation), active phagocytosis (leukocytes destroy bacteria by devouring).

Signs typical for mushrooms -

1) the presence of chitin in the cell wall

2) storage of glycogen in cells

3) absorption of food by phagocytosis

4) the ability to chemosynthesis

5) heterotrophic nutrition

6) limited growth

Signs characteristic of fungi: chitin in the cell wall, storage of glycogen in cells, heterotrophic nutrition. They are not capable of phagocytosis, since they have a cell wall; chemosynthesis is a sign of bacteria; limited growth is a sign of animals.

mushrooms are able to absorb nutrients the entire surface of the body, does this not apply to phagocytosis?

Phagocytosis is the active capture and absorption of microscopic foreign living objects (bacteria, cell fragments) and solid particles by unicellular organisms or specialized cells (phagocytes) of humans and animals.

Microbiology: glossary of terms, Firsov N.N. - M: Bustard, 2006

Aren't mushrooms classified as heterotrophs?

They relate, therefore option 5 is the correct answer

I believe that 125 and 6 are true, as mushrooms have limited growth.

No, mushrooms grow all their life, they are similar to plants.

the storage of glycogen is a characteristic feature of the animal cell.

This is a sign of the similarity between Mushrooms and Animals.

Establish a correspondence between the characteristics of human blood cells and their type.

BLOOD CELL TYPE

A) life expectancy - three to four months

B) move to places where bacteria accumulate

C) participate in phagocytosis and the production of antibodies

D) non-nuclear, have the form of a biconcave disc

D) participate in the transport of oxygen and carbon dioxide

Write down the numbers in the answer, arranging them in the order corresponding to the letters:

Leukocytes: move to places where bacteria accumulate, participate in phagocytosis and the production of antibodies. Erythrocytes: life expectancy - three to four months, non-nuclear, have the form of a biconcave disc, are involved in the transport of oxygen and carbon dioxide.

erythrocytes live for days, and lymphocytes (20-40% of all leukocytes) can live for a very long time, because have immune memory. According to the explanation, it turns out that erythrocytes live longer, and why?

since 20-40% of lymphocytes from the total number of leukocytes, this is not 100% of erythrocytes

Establish a correspondence between life processes and animals in which these processes occur.

A) movement occurs with the help of pseudopods (overflow)

B) food capture by phagocytosis

C) excretion occurs through one contractile vacuole

D) exchange of nuclei during the sexual process

E) excretion occurs through two contractile vacuoles with channels

E) movement occurs with the help of cilia

1) common amoeba

Write down the numbers in the answer, arranging them in the order corresponding to the letters:

Amoeba ordinary: movement occurs with the help of pseudopods (overflow); food capture by phagocytosis; excretion occurs through one contractile vacuole. Infusoria-shoe: exchange of nuclei during sexual intercourse; excretion occurs through two contractile vacuoles with channels; movement occurs with the help of cilia.

Why in the same catalog 29 in task 8 (16141) ciliates are capable of phagocytosis and amoeba too, but here only amoeba. How to understand?

Infusoria is capable of phagocytosis:

Nutrition is as follows. On one side of the body of the shoe there is a funnel-shaped depression leading to the mouth and tubular pharynx. With the help of the cilia lining the funnel, food particles (bacteria, unicellular algae, detritus) are driven into the mouth and then into the pharynx. From the pharynx, food enters the cytoplasm by phagocytosis.

But ciliates do not capture food by phagocytosis, like amoeba.

Which of the following functions does the cell plasma membrane perform? Write down the numbers in ascending order in the answer.

1) participates in the synthesis of lipids

2) carries out active transport of substances

3) participates in the process of phagocytosis

4) participates in the process of pinocytosis

5) is the site of synthesis of membrane proteins

6) coordinates the process of cell division

Plasma membrane of the cell: carries out active transport of substances, participates in the process of phagocytosis and pinocytosis. Under the numbers 1 - functions of smooth EPS; 5 - ribosomes; 6 - cores.

Establish a correspondence between the characteristics of the organism and the organism to which this characteristic belongs.

A) a parasitic organism

B) is capable of phagocytosis

C) forms spores outside the body

D) in unfavorable conditions forms a cyst

E) the hereditary apparatus is contained in the ring chromosome

E) energy is stored in mitochondria in the form of ATP

1) Anthrax stick

2) Common amoeba

Write down the numbers in the answer, arranging them in the order corresponding to the letters:

Anthrax bacillus: a parasitic organism; outside the body forms spores; the hereditary apparatus is contained in the circular chromosome. Common amoeba: capable of phagocytosis; forms a cyst in unfavorable conditions; energy is stored in mitochondria in the form of ATP.

Doesn't the anthrax bacillus form a cyst?

no, bacteria form spores under unfavorable conditions

So, phagocytosis - what is it? Let's try to understand the definition of this term. The word "phagocytosis" originated from two Greek morphemes - phagos (devouring) and kytos (cell). The international medical term phagokytosis, in contrast to the Russified one, has the ending osis, which is translated from Greek as "process" or "phenomenon".

Thus, literally this definition means the process of recognition by specific cells of a foreign agent, purposeful movement towards it, capture and absorption, followed by splitting. In this article, we will talk about what the essence of phagocytosis is. We will also talk about what phagocytes are, consider the stages and find the difference between completed and incomplete phagocytosis.

The history of the discovery of special mobile cells

Outstanding Russian natural scientist - I. I. Mechnikov in 1882 - 1883. conducted experiments on intracellular digestion, studying transparent larvae of sea stars. The scientist was interested in whether he still had the opportunity to capture food by isolated cells. And also to digest it the way the simplest unicellular organisms do, such as amoeba. II Mechnikov conducted the experiment: he injected carmine powder into the bodies of the larvae and observed how a wall of cells grew around these small blood-red grains. They captured and swallowed paint. Then the scientist came up with a hypothesis that any organism must have special protective cells that can absorb and digest other particles that harm the body. To confirm his hypothesis, the scientist used pink thorns, which he introduced into the body of the larva. Some time later, the scientist saw that the cells were surrounded by thorns, trying to resist the "pests" and push them out. The scientist named these specific protective particles found in the body of the larva phagocytes. Thanks to this experience, II Mechnikov revealed phagocytosis. In 1883 he reported on his discovery at the Seventh Congress of Russian Naturalists. Later, the scientist continued to work in this direction, created a comparative pathology of inflammation, as well as the phagocytic theory of immunity. In 1908, together with the scientist P. Ehrlich, he received the Nobel Prize for his most important biological research.

Phagocytosis phenomenon - what is it?

II Mechnikov traced and clarified the role of phagocytosis in the defense reactions of the human body and higher animals. The scientist found that this process plays a significant role in the healing of various wounds. Biological Encyclopedic Dictionary gives the following definition.

Phagocytosis is the active uptake as well as the absorption of foreign objects such as bacteria, micro-fungi and cell fragments by unicellular organisms or specific cells (phagocytes) found in any multicellular organism. What is the essence of phagocytosis? It is believed to be the oldest form of defense in a multicellular organism. Phagocytosis also plays an important role in the functioning of the human immune system. It is the first reaction to the introduction of various viruses, bacteria and other foreign agents. Phagocytes are constantly circulating throughout the body, looking for "pests". When a foreign agent is recognized, it binds with the help of receptors. Then the phagocyte absorbs the pest and destroys it.

Two main groups of mobile cells - "defenders"

Phagocytes are constantly in an active state and are ready to fight the source of infection at any time. They have a certain autonomy, since they can carry out their functions not only inside, but also outside the body: on the surface of mucous membranes and in areas of damaged tissue. From the point of view of their effectiveness, scientists divide human phagocytes into two groups - "professional" and "non-professional". The first group includes monocytes, neutrophils, macrophages, mast cells and tissue

The most important motile phagocytes are white blood cells - leukocytes. They emigrate to the site of inflammation and exercise protective functions. Phagocytosis of leukocytes involves the detection, absorption and destruction of foreign objects, as well as their own dead or damaged cells. After performing their functions, part of the leukocytes moves into the vascular bed and continues to circulate in the blood, while the other undergoes apoptosis or dystrophic changes... The “non-professional” group consists of fibroblasts, reticular and endothelial cells, which have low phagocytic activity.

Phagocytosis process: first stage

Let's consider how the process of fighting harmful organisms takes place. Scientists distinguish four stages of phagocytosis. The first is a rapprochement: a phagocyte approaches a foreign object. This happens either as a result of an accidental collision, or as a result of active directional movement - chemotaxis. There are two types of chemotaxis - positive (movement towards the phagocyte) and negative (movement from the phagocyte). Typically, positive chemotaxis is carried out to the site of tissue damage and is also caused by microbes and their products.

Adhesion of phagocytes to a foreign agent

After the "protector" cell approaches the harmful particle, the second stage begins. It lies in sticking. The phagocyte reaches the object, touches it and attaches itself. For example, leukocytes arriving at the site of inflammation and adhering to the vessel wall do not detach from it even despite the high blood flow rate. The adhesion mechanism is due to the surface charge of the phagocyte. As a rule, it is negative, and the surface of phagocyte objects is positively charged. In this case, the best adhesion is observed. Negatively charged particles, for example, tumor ones, are captured by phagocytes much worse. However, there is adhesion to such particles. It is carried out due to the action of mucopolysaccharides present on the surface of phagocyte membranes, as well as by reducing the viscosity of the cytoplasm and enveloping a foreign agent with serum proteins.

The third stage of phagocytosis

After adhering to a foreign object, the phagocyte begins to absorb it, which can occur in two ways. At the point of contact, the shell of a foreign object, and then the object itself, is drawn into the cell. In this case, the free edges of the membrane close over the object, and as a result, a separate vacuole is formed, containing a harmful particle inside. The second way of absorption is the emergence of pseudopodia, enveloping foreign particles and closing on them. As a result, they are trapped in vacuoles inside the cells. As a rule, phagocytes use pseudopodia to consume micro-fungi. Pulling in or enveloping a harmful object becomes possible due to the fact that the phagocyte membrane is endowed with contractile properties.

Intracellular cleavage of the "pest"

The fourth stage of phagocytosis involves intracellular digestion. It happens as follows. The vacuole containing a foreign particle includes lysosomes, which have a complex of digestive enzymes that are activated and poured out. This creates an environment in which the cleavage of biological macromolecules of ribonuclease, amylase, protease and lipase easily occurs. Thanks to the activated enzymes, destruction and digestion occurs, and then the release of decay products from the vacuole. Now you know what are all four stages of phagocytosis. The protection of the organism is carried out in stages: first, the phagocyte and the object converge, then attraction, that is, the location of the harmful particle on the surface of the "defender", and then the absorption and digestion of the pest.

Incomplete and completed phagocytosis. What are their differences?

Depending on what will be the result of intracellular digestion of foreign particles, there are two types - complete and incomplete phagocytosis. The first ends with the complete destruction of the object and the removal of decay products into the environment. Incomplete phagocytosis - what is it? The term means that foreign cells absorbed by phagocytes remain viable. They can destroy the vacuole or use it as "soil" for reproduction. An example of incomplete phagocytosis is the absorption of gonococci in an organism that does not have immunity to them. With the incomplete process of phagocytosis, pathogens are stored inside phagocytes, and also spread throughout the body. So, in the place of phagocytosis becomes a conductor of the disease, helping pests to spread and multiply.

Causes of disruption of the intracellular digestion process

Violation of phagocytosis occurs due to defects in the formation of phagocytes, as well as suppression of the activity of motile "defender" cells. In addition, a negative change in intracellular digestion is possible due to hereditary diseases such as Alder's and Chadyak-Higashi's diseases. Violation of the formation of phagocytes, including the regeneration of leukocytes, often occurs with radiation exposure or due to hereditary neutropenia. Suppression of the activity of phagocytes can occur due to a deficiency of certain hormones, electrolytes and vitamins. Also, glycolytic poisons and microbial toxins adversely affect the functioning of phagocytes. We hope, thanks to our article, you can easily answer the question: "Phagocytosis - what is it?" Good luck!

Actually, evolution followed the path that one unicellular gobbled up another. Who will eat whom faster. Single-celled organisms united in organized groups - as a result, this led to the formation of multicellular ones. It was safer that way. Each cell of such an organism acquired its own specialization. When multicellular organisms appeared, the concept of “who eats whom faster” has not lost its relevance. Among the organization of cells stood out those from which the primitive immune system was formed in the future. In more advanced multicellular organisms, specialized immune cells appeared.
Cells capable of phagocytosis are among the most important in the immune defense. One cell devours another. To destroy it, eat enough, or get information in this way ("read" the pathogen and warn the rest).

In general, the mechanism of phagocytosis is one of the most ancient mechanisms of the immune response. Phagocytosis was observed by Ilya Ilyich Mechnikov when he pricked a sea star larva with a rose thorn (invertebrates, the first invertebrate fossils lived 485 million years ago).
In the future, the immune system is supplemented with an "antibody" mechanism. When specific proteins (antibodies) are produced and the pathogen is inactivated.

Besides the fact that the word "" is one of the funniest words in biology, the process of phagocytosis itself is quite effective and cool. Remember the old Pacman game? A round yellow ball with a large mouth runs through the maze, dodges enemies, and eats small yellow dots.

I decided to write the article before the next devoted. It is staphylococcal infection that is dominant in purulent surgery. And what is pus? This is all that remains after the battle of the cells of the immune system and microorganisms ... Phagocytosis in the fight against staphylococcus plays a key role.

What is phagocytosis?

In biology, there is a term "endocytosis". The process of absorption by a cell of a particle, molecule, other cell or bacteria. If a large and solid particle is absorbed, then endocytosis is called phagocytosis.

Macrophage vs microbe. What is a macrophage?

The world we live in is a rather dirty place. As everything in nature tends to chaos, so in our life everything tends to get littered. We need to constantly monitor that everything in our house is always clean and things are in their place.
A similar situation occurs in our body. The birth and death of new cells is constantly occurring, every day and hour in our body a genetic malfunction occurs in one of the cells - it becomes cancerous. The intestines are home to bacteria that constantly penetrate the liver through the portal vein. Viruses, bacteria, protozoa, trying to turn our body into a breeding ground ...
Our immune system works constantly to maintain order. An integral part of this system is the macrophage.

It is an amoeba-like organism (like the slimy good-natured man in Ghostbusters). The task of the macrophage is to cleanse the body of microscopic debris and bacteria. The birthplace of macrophages is bone marrow, the predecessor is white blood cell - monocyte.
Macrophages live for about one and a half months, during this time they patrol the body (in the blood test we look at segmented neutrophils, getting into the tissues, they become macrophages).

The tissue macrophage "communicates" with the lymphocyte by the helper. With pseudopodia (protrusions of the cytoplasm), he "probes" the external environment.

Phagocytosis stages

Let us consider this process using the example of leukocytes (neutrophils are the most numerous of them), as cells of the immune system that absorb harmful bacteria. Well, firstly, the leukocyte must clearly understand that it is a foreign organism. The recognition process is quite complicated.
The immune cell detects the molecules released by the bacteria as a signal for action. Then the leukocyte must catch on, adhere to the bacteria. To do this, there are special receptors on its surface, with the help of which it adheres to a foreign cell (this can be not only a bacterium, but also its own cell, which does not respond to commands - for example, a cancer one).

After adhesion, the membrane swells outward and, as it were, envelops the bacterial cell. As a result, the uninvited guest finds himself, as it were, in a soap bubble - a phagosome.
Inside the phagosome, the phagocyte cell secretes enzymes that unload the bacterial cell wall, destroying it.

Let's look at it in order.
1. Chemotaxis. A scent like a dog ... How does a macrophage find a foreign object? Is it really necessary to “touch” all cells (like a person in a room, at night, to the touch) with receptors?
Not. Chemotaxis is a directed movement relative to an object, depending on the chemicals that this very object emits. It was written about negative hemotaxis in the textbook of zoology: a crystal of salt was thrown into the water and the amoeba tried to crawl away from such a neighborhood. With macrophages, chemotaxis is positive. Crawls in response to chemicals released by foreign organisms. They also attract substances - cytokines secreted by their own cells: they call for help. Tuberculosis bacillus, for example, does not emit toxins ("does not smell"), so the immune system does not immediately detect them.

The first to migrate to the inflammation focus are neutrophils from the blood, much later the "big devourer" arrives. These cells are identical in the rate of chemotaxis, but macrophages are activated much later.

2. Adhesion of macrophages to the object. Or "sticking". On the surface of both healthy and pathological cells and microbes, there is a certain set of chemical molecules that signal the macrophage: "eat me" or "don't eat me."
Recognition is carried out by special receptors. And although macrophages are able to phagocytose non-living cells (pieces of coal, asbestos, glass), the phagocytic process is activated after the command of other cells - T-helpers.
It is T-helpers (a type of lymphocytes) that "highlight" what needs to be eaten: specific proteins - opsonins - stick to the "unprepared" object. The macrophage goes to the "smell" of opsonins.

3. In the place where contact with the microbe occurred, the cell membrane is activated. She seems to be pressed inside.

4. Formation of a phagosome. A phagosome is a cavity in which an object of absorption appears. A kind of "stomach" in which, under the action of enzymes, a foreign organism breaks down.
Lysis (splitting) involves hydrogen peroxide (stop constantly pouring peroxide on the wound, thus healthy cells are also damaged!), Nitrous oxide, lysozyme. Various kinds of enzymes - proteases, lipases.
The most striking enzyme in lysosomes is elastase.

5. Release of digestible residues.

Profit! Go to step # 1!

This is in ideal conditions. In reality, everything happens much more interesting. The very mechanism of the immune response of a macroorganism (you and me) and micro- (all that is alive that can be seen through a microscope) is the result of an arms race that has been going on for millions of years.
No ceasefire is planned in this confrontation, and no one will sign an arms limitation treaty. Who will outsmart whom.
The task of the microbe is to invade, multiply and spread. And evolution has tried to have something to implement these plans. Therefore, both on the part of micro- and macroorganisms, a rich arsenal of adaptations has accumulated.
There are pathogens (such as mycobacterium tuberculosis or gonococcus) for which being swallowed by a macrophage is an integral developmental stage.
Where is the best place to hide from the immune system? Of course, inside a representative of this immune system!

When not everything is so simple: incomplete phagocytosis

There are microorganisms for which an attack by macrophages is not a problem. On the contrary, this is an important stage in their development for them. As mentioned, the macrophage engulfs the microbe, forming a phagosome. And this is where it crashes. The enzymes participating in the breakdown of everything that the macrophage has absorbed are concentrated in another "soap bubble" - the lysosome.

Normally, the lysosome fuses with the phagosome. An acidic environment is created in the phagosome, the pH decreases. In an acidic environment, enzymes that break down the bacteria begin to act.
But listeria, for example, secretes substances that prevent the attachment of liposomes (containing enzymes) to the phagosome. Blockade of phagosomal-lysosomal fusion is also characteristic of influenza and Toxoplasma viruses. The macrophage cannot "digest" the causative agent of gonococcal infection. Gonococcus (staphylococcus, by the way, too) is quite resistant to lysosomal enzymes. Rickettsiae destroy the phagosome and can float freely with the cytoplasm of the phagocyte.

How can you cope with what you cannot digest and destroy?

Before continuing the story, it is worth talking about how the mechanism of phagocytosis itself was studied. More precisely from the one thanks to whom. Dictyostellium.
It is this microorganism that plays the most important role in the study of phagocytosis. Cellular slime mold. I wanted to write that it is a unicellular organism, but this is not entirely true ... But not a multicellular one either.
This amoeba-like organism was described in 1935. Due to the fact that it is very easy to grow in the laboratory, it has become the most studied microorganism. The mechanism of phagocytosis is very ancient, it is very similar in the slime mold and in our macrophages. It lives in wet leaf litter, feeds on slime mold bacteria. Another unique feature is that the dictyostelium has three "sexes", and two out of three in any combination are enough for sexual reproduction. For most of its life, Dictyostelium lives in the form of solitary amoebas, feeding on bacteria from the leaf litter.

Now comes the fun part. Remember the movie about transformers, when several robots gathered into one huge one?
So these amoebas, with a lack of food, form cell aggregates, and the size of such a cell formation for the microworld is enormous - up to 1 cm. This macroorganism is able to crawl and subsequently forms a "fruit body".

The "fruit body" of the dictyostelium, capable of movement

Slime molds, before forming a multicellular organism (pseudoplasmodium), absorb bacteria, but do not digest them. Moreover, in a new place, these bacteria are allowed to multiply. Such are the one-celled gardeners.

The macrophages of our body are also capable of creating such a multicellular formation. This "monster" is called the Pirogov-Langhans cage. Previously, these multinucleated cells were detected as an immune response to the introduction of the tubercle bacillus.

When a patient with a long-lasting cough is advised to take a sputum test, the conclusion is written "AFB not found." AFB are acid-fast mycobacteria. The cells of our immune system cannot fully phagocytose the tubercle bacillus.
When there is a contact of a macroorganism with mycobacterium tuberculosis, then neutrophils are the first to fight. And everyone perishes. Mycobacterium is too tough for them. Then the "elder brother" - the macrophage - goes into battle. The macrophage absorbs bacteria one by one, but cannot fully digest them. The bacterium is resistant to the acidic environment of the phagosome; it also affects the phagosomal-lysosomal fusion.

Macrophages will do this more efficiently when taught by T-helpers, or helpers. Each subsequent generation of macrophages becomes "more trained". By the way, about the initial contact with the tubercle bacillus. Everyone remembers Mantoux's reaction at school? With this test, it is determined whether our immune system is familiar with the tubercle bacillus or not. The turn of the tuberculin test is exactly the first contact with mycobacterium.

Fight the immune system with the causative agent of tuberculosis is extremely difficult (why the clinic largely depends on the number of bacteria that have entered the body). In order to limit the spread of infection, macrophages "fed" with mycobacteria begin to unite into a large multicellular structure - the Pirogov-Langhans cell. At first, such a microscopic finding was attributed to inflammation in tuberculosis, but then other diseases (for example, actinomycosis) were revealed.

The huge multinucleated cell of Pirogov-Langhans

It is about such an inflammatory process that they say: specific. Well, what should the body do with a tubercle bacillus, which doesn't want to die in any way? A kind of sarcophagus is formed around the zone of specific inflammation. First it consists of a fibrous protein - fibrin, then it is calcified. The focus of Gona in the lungs is a frequent finding on fluorography. You cannot fully recover from tuberculosis. The person remains permanently infected (but clinically completely healthy).
BCG - vaccination against tuberculosis. Contains killed bacteria to acquaint immune cells with pathogen antigens. The vaccine cannot guarantee protection (it is clear why), but the effectiveness of the immune response increases. Again, it all depends on the number of bacteria and the state of the body.

The Gon focus is most often detected subpleurally and in the upper lobes of the lungs better ventilated: mycobacteria are good in an oxygen environment

Some recent research on phagocytosis.

How sleep affects phagocytic activity

One sleepless night is certainly not good, but in most cases it does not cause any consequences.
Countless sleepless nights are another matter. One study, published in the journal Neuroscience, evaluated the biological effect of sleep deprivation in laboratory mice. It was found that the brain harms itself with prolonged sleep deprivation. The laboratory animals were divided into four groups. One group - "well rested", the mice of the second group were periodically awakened, in the third group the animals did not sleep for several days. Then the scientists studied the brain activity in each group. In mice that were sleep deprived for a long time, an increase in the activity of phagocytosis was revealed. Phagocytes are cleaning cells needed by the brain to cleanse the byproducts of neural activity throughout the day.
After a long period of sleep deprivation, the brain turns on "overdrive", which can be very harmful. Don't panic if your sleep and wake schedule isn't in perfect shape, but try to get enough sleep.

Phagocytosis and hyperglycemia

Why do surgeons often prescribe a blood test to determine glucose levels for purulent-inflammatory processes?
Why do patients with diabetes mellitus are infectious diseases more severe? One of the factors: fast carbohydrates affect the activity of macrophages.
People were given 100-gram portions of carbohydrates from glucose, fructose, sucrose, honey. Then, venous blood was taken at 1, 2, 3 and 5 hours after eating. A suspension containing (Staphylococcus epidermidis) was added to the blood.
Later, a study of the activity of macrophages was conducted. It was found that rapidly assimilated carbohydrates inhibit the phagocytic activity of macrophages.
So it is very important to monitor the glucose level, especially in patients with diabetes mellitus undergoing treatment for purulent-inflammatory processes.

Finally

And although phagocytosis is the most ancient way protection from foreign organisms, it has not lost its importance. This mechanism is key in the fight against staphylococcal infection.

Palamarchuk Viacheslav

If you find a typo in the text, please let me know. Highlight a piece of text and press Ctrl + Enter.

The essence of the phenomenon

Active particles of the defense mechanism

The phagocytosis phenomenon is carried out by two protective cells:

Neutrophils - created in the bone marrow. They belong to granulocytic blood particles, the structure of which is distinguished by its granularity.
Monocytes are a type of leukocytes that are released from the bone marrow. Young phagocytes are highly mobile and carry out the structure of the main protective barrier.

Selective protection

Phagocytosis is a protective barrier against a huge number of pathogens:

bacteria;
viruses;
blood clots;
tumor cells;
fungal spore;
toxins and slag inclusions.

Low rates of phagocytosis are observed with long-term chronic diseases:

tuberculosis;
pyelonephritis;
respiratory tract infections;
rheumatism;
atopic dermatitis.

The activity of phagocytes changes under the influence of certain substances:

cholesterol;
calcium salts;
antibodies;
histamine.

Avitominosis, the use of antibiotics, corticosteroids inhibit the defense mechanism. Phagocytosis acts as an assistant to the immune system. Forced activation occurs in three ways:

Classic - carried out according to the antigen-antibody principle. The activators are IgG, IgM immunoglobulins.
Alternative - polysaccharides, viral particles, tumor cells are used.
Lectin - a group of proteins that pass through the liver is used.

Particle Destruction Sequence

To understand the process of the protective mechanism, the stages of phagocytosis are determined:

Chemotaxis is the period of penetration of a foreign particle into the human body. It is characterized by an abundant release of a chemical reagent that serves as a signal for activity for macrophages, neutrophils, and monocytes. Human immunity directly depends on the activity of protective cells. All awakened cells attack the area of \u200b\u200bintroduction of a foreign body.
Adhesion - recognition of a foreign body due to receptors by phagocytes.
The preparatory process of defense cells to attack.
Absorption - particles gradually cover the foreign substance with their membrane.
Phagosome formation is the completion of the membrane surrounding the foreign body.
Phagolysosome creation - digestive enzymes are released into the capsule.
Killing - killing harmful particles.
Removal of residues of particle splitting.

The bacterial cell is capable of phagocytosis. Phagocytosis is the body's defender

The greatest ability to phagocytosis is possessed by neutrophils and monocytes

Phagocytosis

ability to phagocytosis

See what the "ability to phagocytosis" is in other dictionaries:

Phagocytosis

Phagocytosis is the body's defender

The essence of the phenomenon

Active particles of the defense mechanism

Selective protection

Particle Destruction Sequence

The ability to phagocytosis

The history of the discovery of special mobile cells

Phagocytosis phenomenon - what is it?

Two main groups of mobile cells - "defenders"

Phagocytosis process: first stage

Adhesion of phagocytes to a foreign agent

The third stage of phagocytosis

Intracellular cleavage of the "pest"

Incomplete and completed phagocytosis. What are their differences?

Causes of disruption of the intracellular digestion process

What is phagocytosis?

Macrophage vs microbe. What is a macrophage?

Phagocytosis stages

When not everything is so simple: incomplete phagocytosis

How can you cope with what you cannot digest and destroy?

Some recent research on phagocytosis.

How sleep affects phagocytic activity

Phagocytosis and hyperglycemia

Finally

The essence of the phenomenon

Active particles of the defense mechanism

Selective protection

Particle Destruction Sequence

Report a typo

Text to be sent to our editors:

Your comment (optional):