The process forces the immune system. Anatomy and physiology of the immune system

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Immunity(from Latin immunitas - to free from something) is physiological function, which causes the body's immunity to foreign antigens. Human immunity makes him immune to many bacteria, viruses, fungi, worms, protozoa, and various animal poisons. In addition, the immune system protects the body from cancer cells.

The task of the immune system is to recognize and destroy all foreign structures. Upon contact with a foreign structure, cells of the immune system trigger an immune response, which leads to the removal of the foreign antigen from the body.

The immune function is ensured by the work of the body's immune system, which includes Various types organs and cells. Below we will consider in more detail the structure of the immune system and the basic principles of its functioning.

Anatomy of the immune system
The anatomy of the immune system is extremely heterogeneous. In general, cells and humoral factors The immune system is present in almost all organs and tissues of the body. The exception is some parts of the eyes, testicles in men, thyroid gland, brain - these organs are protected from the immune system by a tissue barrier, which is necessary for their normal functioning.

In general, the functioning of the immune system is ensured by two types of factors: cellular and humoral (that is, liquid). Cells of the immune system ( different kinds leukocytes) circulate in the blood and pass into tissues, carrying out constant surveillance of the antigenic composition of tissues. In addition, a large number of different antibodies (humoral, fluid factors) circulate in the blood, which are also capable of recognizing and destroying foreign structures.

In the architecture of the immune system, we distinguish between central and peripheral structures. Central organs of the immune system are Bone marrow and thymus (thymus gland). In the bone marrow (red bone marrow), the formation of cells of the immune system occurs from the so-called stem cells, which give rise to all blood cells (erythrocytes, leukocytes, platelets). The thymus gland (thymus) is located in chest, just behind the sternum. The thymus is well developed in children, but with age it undergoes involution and is practically absent in adults. In the thymus, differentiation of lymphocytes - specific cells of the immune system - occurs. In the process of differentiation, lymphocytes “learn” to recognize “their” and “foreign” structures.

Peripheral organs of the immune system represented by lymph nodes, spleen and lymphoid tissue (such tissue is found, for example, in palatine tonsils, at the root of the tongue, at back wall nasopharynx, intestines).

The lymph nodes represent a cluster lymphoid tissue(actually a collection of immune system cells) surrounded by a membrane. A lymph node contains lymphatic vessels through which lymph flows. Inside the lymph node, the lymph is filtered and cleared of all foreign structures (viruses, bacteria, cancer cells). The vessels leaving the lymph node merge into common duct, which flows into a vein.

Spleen is nothing more than a large lymph node. In an adult, the mass of the spleen can reach several hundred grams, depending on the amount of blood accumulated in the organ. The spleen is located in abdominal cavity to the left of the stomach. A large amount of blood is pumped through the spleen per day, which, like lymph in the lymph nodes, undergoes filtration and purification. Also, a certain amount of blood is stored in the spleen, which the body does not currently need. During physical activity or stress, the spleen contracts and releases blood into blood vessels, in order to satisfy the body's need for oxygen.

Lymphoid tissue scattered throughout the body in the form of small nodules. The main function of lymphoid tissue is to provide local immunity, therefore, the largest accumulations of lymphoid tissue are located in the mouth, pharynx and intestines (these areas of the body are abundantly populated by a variety of bacteria).

Besides, in various organs there are so-called mesenchymal cells, which can perform immune function. There are many such cells in the skin, liver, and kidneys.

Immune system cells
Common name immune system cells leukocytes. However, the leukocyte family is very heterogeneous. We distinguish two main types of leukocytes: granular and non-granular.

Neutrophils- the most numerous representatives of leukocytes. These cells contain an elongated nucleus divided into several segments, so they are sometimes called segmented leukocytes. Like all cells of the immune system, neutrophils are formed in the red bone marrow and, after maturation, enter the blood. The circulation time of neutrophils in the blood is not long. Within a few hours, these cells penetrate the walls of blood vessels and move into the tissue. After spending some time in the tissues, neutrophils can return to the blood. Neutrophils are extremely sensitive to the presence of inflammation in the body and are able to migrate directionally into inflamed tissues. Once in the tissue, neutrophils change their shape - from round they turn into branched ones. The main function of neutrophils is the neutralization of various bacteria. To move through tissues, the neutrophil is equipped with peculiar legs, which are outgrowths of the cell cytoplasm. Moving towards the bacterium, the neutrophil surrounds it with its processes, and then “swallows” and digests it with the help of special enzymes. Dead neutrophils accumulate in areas of inflammation (for example, in wounds) in the form of pus. The number of blood neutrophils increases during various inflammatory diseases bacterial nature.

Basophils take an active part in the development of immediate allergic reactions. Once basophils enter tissues, they turn into mast cells containing large amounts of histamine - biologically active substance, which stimulates the development of allergies. Thanks to basophils, the poisons of insects or animals are immediately blocked in the tissues and do not spread throughout the body. Basophils also regulate blood clotting with the help of heparin.

Lymphocytes. There are several types of lymphocytes: B-lymphocytes (read “B-lymphocytes”), T-lymphocytes (read “T-lymphocytes”), K-lymphocytes (read “K-lymphocytes”), NK-lymphocytes (natural killer cells) and monocytes .

B lymphocytes recognize foreign structures (antigens) while producing specific antibodies (protein molecules directed against foreign structures).

T lymphocytes perform the function of regulating immunity. T-helpers stimulate the production of antibodies, and T-suppressors inhibit it.

K lymphocytes capable of destroying foreign structures labeled with antibodies. Under the influence of these cells, various bacteria can be destroyed, cancer cells or cells infected with viruses.

NK lymphocytes exercise control over the quality of body cells. At the same time, NK lymphocytes are capable of destroying cells that differ in their properties from normal cells, for example, cancer cells.

Monocytes These are the largest blood cells. Once in the tissue, they turn into macrophages. Macrophages are large cells that actively destroy bacteria. Macrophages accumulate in large quantities in areas of inflammation.

Compared to neutrophils (see above), some types of lymphocytes are more active against viruses than bacteria and are not destroyed during a reaction with a foreign antigen, therefore pus does not form in areas of inflammation caused by viruses. Lymphocytes also accumulate in areas of chronic inflammation.

The leukocyte population is constantly renewed. Millions of new immune cells are formed every second. Some immune system cells only live for a few hours, while others can persist for several years. This is the essence of immunity: once it encounters an antigen (virus or bacteria), the immune cell “remembers” it and reacts faster the next time it encounters it, blocking the infection immediately after it enters the body.

The total mass of organs and cells of the immune system of an adult human body is about 1 kilogram. The interactions between cells of the immune system are extremely complex. Overall, coordinated work various cells immune system, provides reliable protection the body from various infectious agents and its own mutated cells.

In addition to their protective function, immune cells control the growth and reproduction of body cells, as well as tissue restoration in areas of inflammation.

In addition to the cells of the immune system, there are a number of factors in the human body nonspecific protection, which constitute the so-called species immunity. These protective factors are represented by the complement system, lysozyme, transferrin, C-reactive protein, interferons.

Lysozyme is a specific enzyme that destroys the walls of bacteria. Lysozyme is found in saliva in large quantities, which explains its antibacterial properties.

Transferin is a protein that competes with bacteria for capture certain substances(for example, iron) necessary for their development. As a result, the growth and reproduction of bacteria slows down.

C-reactive protein is activated like a compliment when foreign structures enter the blood. The attachment of this protein to bacteria makes them vulnerable to cells of the immune system.

Interferons- These are complex molecular substances that are released by cells in response to the penetration of viruses into the body. Thanks to interferons, cells become immune to the virus.

Bibliography:

• Khaitov R.M. Immunogenetics and immunology, Ibn Sina, 1991
• Leskov, V.P. Clinical immunology for doctors, M., 1997
• Borisov L.B. Medical Microbiology, Virology, Immunology, M.: Medicine, 1994

Hello everyone, Olga Ryshkova is with you. Did you know that even when we feel absolutely healthy, our body fights disease? We live in an environment with a huge number of microbes, we inhale billions of microorganisms and do not get sick because it protects us the immune system.

The immune system never rests; its cells circulate throughout the body, looking not only for microbes, viruses and foreign substances, but also for damage in its own tissues. Everything foreign is an enemy, and the enemy must be destroyed.

Most people have a vague idea of ​​where the human immune system is located and how it works. Its foundation is the central organs. All immune cells come from there. It's bone marrow inside tubular bones and the thymus (thymus gland), which is located behind the breastbone. The thymus is the largest in children, because their immune system is intensively developing.

In an adult it is significantly less (in an elderly person 6 g or less).

The spleen is also one of the central organs of the immune system; in an adult it weighs about 200 g.

There are also many small structures - lymph nodes, which are located almost everywhere. Some are so small that they can only be seen under a microscope. There is no area in the body where the immune system does not exercise its control.

Cells of the immune system, lymphocytes, circulate freely throughout the body using blood, tissue and lymph fluids and regularly meet in the lymph nodes, where they exchange information about the presence of foreign agents in the body. This is a conversation at the molecular level.

In fact, immunity is represented by heterogeneous cells; they are united by one goal - to instantly move from reconnaissance to attack.

The first level is local protection. When a microbe penetrates mucous or damaged skin, the cells are activated and released chemical substances(chemokines), which attract other immune cells and increase vascular permeability to them. A huge number of immune cells accumulate in this area and a focus of inflammation is formed.

Phagos means to swallow; these are the cells that can “eat” the pathogen. The largest representatives of phagocytes are called macrophages; they are capable of absorbing and destroying thousands of microbes at the same time.

Smaller phagocytes include neutrophils; there are billions of them in our blood.

If for some reason a person produces few neutrophils, severe infections can develop against this background, and even with massive antibacterial or antifungal therapy, life is threatened. Neutrophils attack pathogens in large numbers in the first rows of protective cells and usually die along with them. The pus at the site of inflammation is dead neutrophils.

Antibodies then join the fight. The immune system is a self-learning structure; during evolution, it invented the antigen-antibody system. An antigen is a molecule on a foreign cell (bacteria, virus, or protein toxin) against which an antibody is formed. Against a specific antigen there is a specific antibody that can accurately recognize it, because it fits like a key to a lock. This is an accurate recognition system.

The bone marrow produces a group of lymphocytes called B lymphocytes. They appear immediately with ready-made antibodies on the surface, with a wide range of antibodies that can recognize wide range antigens. B lymphocytes travel throughout the body and when they encounter pathogens with antigen molecules on the surface, they bind to them and signal to the immune system that they have detected an enemy.

But B lymphocytes detect pathogens in the blood, and if they penetrate the cell, as viruses do, they become inaccessible to B lymphocytes. The work involves a group of lymphocytes called T-killers. Affected cells differ from normal ones in that there are small fragments of the viral protein on their surface. Through them, T-killers recognize cells with viruses and destroy them.

Killer cells receive their receptor, which recognizes the viral protein, in the thymus ( thymus gland).

The diversity of receptors makes it possible to detect all kinds of microorganisms. After their discovery, mass cloning of B-lymphocytes and T-killers begins. At the same time, special substances pyrogens are formed, which raise body temperature, and the lymph nodes in which lymphocytes are cloned enlarge.

If a person has immunity to the pathogen, the body will cope without treatment. The principle of vaccination is based on this. Memory cells are responsible for the formation of immunity after vaccination or after an infectious disease. These are lymphocytes that have encountered antigens. They enter the lymph nodes or spleen and wait there for a second encounter with the same antigen.

The immune system is a collection of organs, tissues and cells, the work of which is aimed directly at protecting the body from various diseases and at destroying foreign substances that have already entered the body.

It is this system that is an obstacle to infectious agents (bacterial, viral, fungal). When the immune system malfunctions, the likelihood of developing infections increases, which also leads to the occurrence of autoimmune diseases, including multiple sclerosis.

Organs included in the human immune system: lymph glands(nodes), tonsils, thymus gland (thymus), bone marrow, spleen and intestinal lymphoid formations (Peyer's patches). What unites them a complex system circulation, which consists of ducts connecting the lymph nodes.

Lymph node is a soft tissue formation that has oval shape, size 0.2 - 1.0 cm and contains a large number of lymphocytes.

Tonsils are small collections of lymphoid tissue located on either side of the throat.

The spleen is an organ that looks very similar to a large lymph node. The functions of the spleen are varied: it is a filter for the blood, a storage facility for its cells, and a site for the production of lymphocytes. It is in the spleen that old and defective blood cells are destroyed. This organ of the immune system is located in the abdomen under the left hypochondrium near the stomach.

Thymus gland (thymus) located behind the sternum. Lymphoid cells in the thymus multiply and “learn.” In children and people young The thymus is active; the older a person is, the more passive and smaller this organ becomes.

Bone marrow is soft, spongy tissue located inside tubular and flat bones. The main task of the bone marrow is the production of blood cells: leukocytes, erythrocytes, platelets.

Peyer's patches - these are concentrations of lymphoid tissue in the walls of the intestine, more specifically in the appendix ( vermiform appendix). However, the main role is played by the circulation system, consisting of ducts that connect the lymph nodes and transport lymph.

Lymph fluid(lymph) is a colorless liquid that flows through lymphatic vessels, it contains many lymphocytes - white blood cells involved in protecting the body from diseases.

Lymphocytes are, figuratively speaking, “soldiers” of the immune system; they are responsible for the destruction of foreign organisms or their own diseased cells (infected, tumor, etc.). The most important species lymphocytes – B-lymphocytes and T-lymphocytes. They work together with other immune cells and do not allow foreign substances (infectious agents, foreign proteins etc.). At the first stage of development of the human immune system, the body “teaches” T-lymphocytes to distinguish foreign proteins from normal (its own) body proteins. This learning process takes place in the thymus gland in early childhood, since at this age the thymus is most active. When the child reaches puberty, his thymus decreases in size and loses its activity.

Interesting fact: with many autoimmune diseases, for example, when multiple sclerosis, the patient’s immune system “does not recognize” the healthy tissues of his own body, treats them as foreign cells, and begins to attack and destroy them.

The role of the human immune system

The immune system appeared along with multicellular organisms and developed as an assistant to their survival. It unites organs and tissues that guarantee the body’s protection from genetically foreign cells and substances coming from environment. In terms of organization and functioning mechanisms, immunity is similar nervous system.

Both of these systems are represented by central and peripheral organs, capable of responding to different signals, have a large number of receptor structures and specific memory.

The central organs of the immune system include the red bone marrow and thymus, and the peripheral organs include the lymph nodes, spleen, tonsils, and appendix.

The leading place among the cells of the immune system is occupied by leukocytes. With their help, the body is able to provide different shapes immune response upon contact with foreign bodies, for example, the formation of specific antibodies.

History of immunity research

The very concept of “immunity” in modern science contributed by the Russian scientist I.I. Mechnikov and the German doctor P. Ehrlich, who studied the body’s defense reactions in the fight against various diseases, first of all, infectious. Their collaborations in this area were even noted in 1908 Nobel Prize. The work of the French scientist Louis Pasteur, who developed a vaccination method against a number of dangerous infections, also made a great contribution to the science of immunology.

The word "immunity" comes from the Latin "immunis", which means "free from anything". Initially, it was believed that the immune system only protects us from infectious diseases. However, research by the English scientist P. Medawar in the mid-twentieth century proved that immunity provides protection in general from any foreign and harmful interference in the human body.

Currently, immunity is understood, firstly, as resistance to infections, and secondly, as the body’s responses aimed at destroying and removing from it everything that is alien to it and poses a threat. It is clear that if people did not have immunity, they simply would not be able to exist, and it is its presence that allows us to successfully fight diseases and live to old age.

The work of the immune system

The immune system has developed over long years human evolution and operates like a well-oiled machine. It helps us fight diseases and harmful environmental influences. The tasks of the immune system include recognizing, destroying and removing both foreign agents penetrating from the outside and decay products formed in the body itself (during infectious and inflammatory processes), as well as destroying pathologically changed cells.

The immune system is able to recognize many “strangers”. Among them are viruses, bacteria, toxic substances of plant or animal origin, protozoa, fungi, and allergens. Among her enemies she includes those who have turned cancerous and therefore become dangerous. own cells. the main objective immunity - to provide protection from intrusion and maintain integrity internal environment organism, its biological individuality.

How is “strangers” recognized? This process occurs at the genetic level. The fact is that each cell carries its own genetic information, unique only to this particular organism (we can call it a mark). It is its immune system that analyzes when it detects penetration into the body or changes in it. If the information matches (the tag is present), then it’s yours; if it doesn’t match (the tag is missing), it means it’s someone else’s.

In immunology, foreign agents are usually called antigens. When the immune system detects them, they immediately turn on defense mechanisms, and the struggle begins against the “stranger.” Moreover, to destroy each specific antigen, the body produces specific cells, they are called antibodies. They fit antigens like a key to a lock. Antibodies bind to the antigen and eliminate it, which is how the body fights the disease.

Allergic reactions

One of the main immune reactions a person is a state of increased response of the body to allergens. Allergens are substances that contribute to the occurrence of a corresponding reaction. There are internal and external factors that provoke allergies.

External allergens include some food products(eggs, chocolate, citrus fruits), various chemicals (perfumes, deodorants), medications.

Internal allergens are your own cells, usually with altered properties. For example, with burns, the body perceives dead tissue as foreign and creates antibodies for them. The same reactions can occur with the bites of bees, bumblebees and other insects.

Allergies develop rapidly or sequentially. When an allergen acts on the body for the first time, the immune system produces and accumulates antibodies with hypersensitivity to him. When the same allergen enters the body again, an allergic reaction occurs, for example, skin rashes, swelling, redness and itching.

Education: Moscow medical school them. I. M. Sechenov, specialty - "General Medicine" in 1991, in 1993 " Occupational diseases", in 1996 "Therapy".

The immune system is necessary for humans to protect the body from external foreign invasions, control the physiological reactions of the body and provide normal functioning circulatory system. Our immune system quickly recognizes foreign agents that invade the human body and immediately initiates an adequate protective response, the so-called immune response.

Foreign elements are called “antigens”, and by their nature they can have very different origins and structures: viruses, fungi, bacteria, plant pollen, house dust, chemicals, transplanted tissues and organs - this list is very long. If the immune system does not work properly, then antigens can provoke serious illnesses person and will threaten his life.

To form an adequate immune response to invading antigens, the immune (lymphatic) system activates many organs and specific cells that are part of it and located throughout the body. The structure of the immune system is only slightly inferior in complexity to the human nervous system.

The main organ of the human immune system is considered Bone marrow, which is responsible for hematopoiesis - produces red blood cells, platelets and leukocytes to replace dying and dying cells. There are yellow and red bone marrow, total weight which in the body of an adult reaches 2.5-3 kg. The location of the bone marrow is the large bones of the human skeleton (spine, tibia, pelvic bones and others).

Thymus gland or thymus together with the bone marrow, it is the central organ of the immune system, consisting of immature and undifferentiated cells - stem cells, which come to it from the bone marrow. In the thymus, maturation, differentiation of cells and the eventual formation of T-lymphocytes, which are responsible for cellular immune responses, occur. The thymus gland is located behind the upper third of the sternum in the mediastinum between the right and left mediastinal pleura.

Produce lymphocytes and tonsils, which are located on the back wall of the nasopharynx in its upper part. The tonsils consist of diffuse lymphoid tissue, which contains small, dense lymphoid nodules.

Spleen, one of central authorities immune system, located in the abdominal cavity in the area of ​​the left hypochondrium, which is projected at the level of the IX-XI ribs. The spleen has appearance slightly flattened elongated hemisphere. Enters the spleen arterial blood along the splenic artery to cleanse the blood of foreign elements and remove old and dead cells.

Peripheral immune (lymphatic) system is represented in human organs and tissues by a branched system of lymphatic capillaries, vessels, and ducts. The lymphatic system works in close relationship with the circulatory system and is constantly in contact with tissue fluid, through which they enter nutrients to the cells. Transparent and colorless lymph transports metabolic products into the blood through the lymphatic system and is the carrier of protective cells - lymphocytes, which are in direct contact with antigens.

The peripheral lymphatic system includes specific formations - The lymph nodes, which are maximally located in the human body, for example, in groin area, near armpit, at the base of the mesentery small intestine and others. Lymph nodes play a protective role as “filters”, which boils down to the production of lymphocytes, immune bodies, destruction pathogenic bacteria. Lymph nodes are the guardians of lymphocytes and phagocytes. They are responsible for the immune response and form the immune response.

Lymph is actively involved in the elimination inflammatory process and, and active participants in immune reactions are lymph cells - lymphocytes, which are divided into T cells and B cells.

B cells (B lymphocytes) are produced and accumulated in the bone marrow. It is they who form specific antibodies, which are a “counterweight” to only one type of antigen. As many antigens enter the body, so many types of antibodies are formed to neutralize foreign agents during the immune response. B cells are active only against antigens that are located outside the cells and float freely in the blood.

Source T cells (T lymphocytes) serves as the thymus gland. This type of lymphatic cell, in turn, is divided into T-helper cells (T-helper cells) and T-suppressor cells. T-helpers play a leading role in the body’s defense response and coordinate the work of all immune cells. T-suppressors control the strength and duration of the immune response in order to slow down the immune reaction in time if the antigen has already been neutralized and is necessary active work the immune system no longer exists.

Lymphocytes are also released - Killer T cells, which attach to damaged or infected cells human body in order to subsequently destroy them.

A huge role in the formation of the immune response is played by phagocytes, which actively attack and destroy antigens. Among phagocytes, the macrophage, which is called the “great destroyer,” is of particular interest. It envelops and absorbs antigens or damaged cells, so that after “digesting” them, they are finally destroyed into their component parts.

The basis of immune reactions is the ability to recognize “self” and “foreign”. The immune reaction synthesizes specific antibody formations, which become the basis of humoral immunity, and sensitized lymphocytes provide cellular immunity. All immunocompetent cells necessarily participate in the inflammatory (immune) reaction and determine the nature and course of its course. In addition, immune cells control and regulate tissue regeneration processes after damage.

So, in response to the invasion of any antigen, the body responds with an immune response, which has two types of immune response, caused by two types of lymphocytes. Humoral immunity is formed by B lymphocytes due to the formation of free antibodies circulating in the blood. This type of immune response is called humoral. The cellular immune reaction develops due to T lymphocytes, which ultimately form cell-mediated immunity. These two types of immune reactions are involved in the destruction of foreign proteins that have entered the body or are formed by the human tissues and organs themselves.

The humoral immune reaction is designed to eliminate foreign proteins with the help of antibodies circulating freely in the blood. When B lymphocytes encounter an antigen, they instantly recognize it as a foreign substance and immediately turn into cells that produce antibodies, which are carried through the bloodstream and destroy “their” antigens along the way. Cells that produce antibodies are called plasma cells. Their main location is the spleen and bone marrow.

At their core, antibodies are Y-shaped protein formations that are capable of attaching to foreign proteins using a kind of “key-lock” mechanism. The “V” shaped tip of the antibody attaches to the foreign protein, and Bottom part in the form of an “I” in the form of a bridge connects to the phagocyte. The phagocyte, in turn, removes the antigen-antibody complex from the body by turning on the appropriate destruction mechanism.

But, on their own, B lymphocytes are not able to provide an adequate immune response. They come to the aid of T-lymphocytes, which trigger a cellular immune reaction that has its own characteristics. IN in some cases B lymphocytes do not turn into plasma cells when they encounter an antigen, but instead they send a signal to T lymphocytes to help them fight foreign proteins. T-lymphocytes that come to the rescue when confronted with “strangers” begin to produce specific chemicals called “lymphokines”, which serve as a catalyst for activation large quantity various immune cells. All cells, in turn, begin to actively divide and capture the foreign cell to destroy it. The peculiarity of the cellular immune reaction is that antibodies do not take part in it.

The immune system is multifunctional and unique; it is characterized by the phenomenon of “memory”, which provides an accelerated and stronger immune response when it encounters an antigen again. The secondary immune reaction is always more effective than the primary one. This effect is the basis for the formation of immunity and the meaning of vaccination.

Faculty Control

Department "Humanitarian and social disciplines"

by discipline Physical Culture

"The body's immune system

person"

Completed by: student Shundakova K.M.

Group ED20.1/B-12

Checked by Orlov A.N.

Moscow 2013

The immune system is a collection of organs, tissues and cells, the work of which is aimed directly at protecting the body from various diseases and at destroying foreign substances that have already entered the body.

This system is an obstacle to infections (bacterial, viral, fungal). When the immune system malfunctions, the likelihood of developing infections increases, which also leads to the development of autoimmune diseases, including multiple sclerosis.

Organs included in the human immune system: lymph glands (nodes), tonsils, thymus gland (thymus), bone marrow, spleen and lymphoid formations of the intestine (Peyer's patches). The main role is played by a complex circulation system, which consists of lymphatic ducts connecting the lymph nodes.

A lymph node is a soft tissue formation, oval in shape and 0.2 - 1.0 cm in size, which contains a large number of lymphocytes.

Tonsils are small collections of lymphoid tissue located on both sides of the pharynx. The spleen is very similar in appearance to a large lymph node. The functions of the spleen are varied, it is a filter for blood, a storage for blood cells, and the production of lymphocytes. It is in the spleen that old and defective blood cells are destroyed.

The thymus gland (thymus) is located behind the breastbone. Lymphoid cells in the thymus multiply and “learn.” In children and young people, the thymus is active; the older a person is, the less active the thymus becomes and decreases in size.

Bone marrow is soft, spongy tissue located inside tubular and flat bones. The main task of the bone marrow is the production of blood cells: leukocytes, erythrocytes, platelets.

Peyer's patches - This is a concentration of lymphoid tissue in the intestinal wall. The main role is played by the circulation system, consisting of lymphatic ducts that connect the lymph nodes and transport lymphatic fluid.

Lymphatic fluid (lymph) is a colorless liquid that flows through the lymphatic vessels; it contains many lymphocytes - white blood cells involved in protecting the body from disease.

Lymphocytes are figuratively speaking “soldiers” of the immune system; they are responsible for the destruction of foreign organisms or diseased cells (infected, tumor, etc.). The most important types of lymphocytes (B lymphocytes and T lymphocytes) work together with other immune cells and prevent foreign substances (infections, foreign proteins, etc.) from invading the body. At the first stage, the body “teaches” T-lymphocytes to distinguish foreign proteins from normal (its own) proteins of the body. This learning process takes place in the thymus gland in childhood, since at this age the thymus is most active. Then a person reaches adolescence, and the thymus decreases in size and loses its activity.

The immune system appeared along with multicellular organisms and evolved as an aid to their survival. It connects organs and tissues that guarantee the body’s protection from genetically foreign cells and substances that come from the environment. In terms of organization and functioning mechanisms, it is similar to the nervous system.

Both systems are represented by central and peripheral organs that are capable of responding to different signals, have a large number of receptor structures, and specific memory.

The central organs of the immune system include the red bone marrow, and the peripheral organs include the lymph nodes, spleen, tonsils, and appendix.

The central place among the cells of the immune system is occupied by various lymphocytes. When in contact with foreign bodies, with their help, the immune system is able to provide different forms of immune response: the formation of specific blood antibodies, the formation of different types of lymphocytes.

The very concept of immunity was introduced into modern science by the Russian scientist I.I. Mechnikov and the German - P. Ehrlich, who studied the body's defense reactions in the fight against various diseases, primarily infectious ones. Their joint work in this area was even awarded the Nobel Prize in 1908. The work of the French scientist Louis Pasteur, who developed a vaccination method against a number of dangerous infections, also made a great contribution to the science of immunology.

The word immunity comes from the Latin immunis, which means free from anything. At first it was believed that immunity protects the body only from infectious diseases. However, research by the English scientist P. Medawar in the mid-twentieth century proved that immunity provides protection in general from any foreign and harmful interference in the human body.

Currently, immunity is understood, firstly, as the body’s resistance to infections, and, secondly, as the body’s responses aimed at destroying and removing from it everything that is alien to it and poses a threat. It is clear that if people did not have immunity, they simply would not be able to exist, and its presence allows us to successfully fight diseases and live to old age.

The immune system has been formed over many years of human evolution and acts like a well-oiled mechanism and helps fight diseases and harmful environmental influences. Its tasks include recognizing, destroying and removing from the body both foreign agents penetrating from the outside, as well as decay products formed in the body itself (during infectious and inflammatory processes), as well as pathologically changed cells.

The immune system is able to recognize many “strangers”. Among them are viruses, bacteria, toxic substances of plant or animal origin, protozoa, fungi, and allergens. She includes among them the cells of one’s own body that have turned cancerous and therefore become “enemies.” Its main goal is to provide protection from all these “strangers” and preserve the integrity of the internal environment of the body, its biological individuality.

How is “enemies” recognized? This process occurs at the genetic level. The fact is that each cell carries its own genetic information, unique only to a given person (we can call it a mark). This is what the immune system analyzes when it detects penetration into the body or changes in it. If the information matches (the label is present), then it is yours; if it does not match (the label is missing), it means it is someone else’s.

In immunology, foreign agents are usually called antigens. When the immune system detects them, defense mechanisms immediately turn on, and the fight against the “stranger” begins. Moreover, to destroy each specific antigen, the body produces specific cells, they are called antibodies. They fit antigens like a key to a lock. Antibodies bind to the antigen and eliminate it - this is how the body fights the disease.

One of the immune reactions is allergy - a state of increased response of the body to allergens. Allergens are substances or objects that contribute to the appearance of allergic reaction in organism. They are divided into internal and external.

External allergens include some foods (eggs, chocolate, citrus fruits), various chemicals (perfumes, deodorants), and medications.

Internal allergens are the body’s own tissues, usually with altered properties. For example, with burns, the body perceives dead tissue as foreign and creates antibodies for them. The same reactions can occur with the bites of bees, bumblebees, and other insects. Allergic reactions develop rapidly or sequentially. When an allergen affects the body for the first time, antibodies with increased sensitivity to it are produced and accumulated. When this allergen enters the body again, an allergic reaction occurs, for example, skin rashes and various tumors appear.