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In which human organ are immune cells located? Good and weak immunity. The immune system of the human body - video

The immune system necessary for a person to protect the body from external alien invasions, control the physiological reactions of the body and ensure the normal functioning of the circulatory system. Our immune system quickly recognizes foreign agents that invade the human body and immediately turns on an adequate defensive response, the so-called immune response.

Foreign elements are called "antigens", and by their nature they can have a very different origin and structure: viruses, fungi, bacteria, plant pollen, house dust, chemicals, transplanted tissues and organs - the list is very long. If the immune system works with disorders, then antigens can provoke serious human diseases and threaten his life.

In order to form an adequate immune response to the invasion of antigens, the immune (lymphatic) system includes 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 its complexity nervous system person.

The main organ of the human immune system is Bone marrow, which is responsible for hematopoiesis - produces red blood cells, platelets and white blood cells in exchange for dying and dying cells. There are yellow and red bone marrow, the total weight of 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, etc.).

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 that come to it from the bone marrow. In the thymus, maturation, differentiation of cells and the formation of T-lymphocytes, which are responsible for the reactions of cellular immunity, take place. 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 back wall nasopharynx in its upper part. The tonsils are composed of diffuse lymphoid tissue, which contains small, dense lymphoid nodules.

Spleen, one of the central organs of the immune system, is located in the abdominal cavity in the zone of the left hypochondrium, which is projected at the level of the IX-XI ribs. The spleen has the appearance of a slightly flattened elongated hemisphere. Arterial blood flows to the spleen through the splenic artery to purify the blood of foreign elements and remove old and dead cells.

Peripheral immune (lymphatic) system It is represented in human organs and tissues by an extensive system of lymphatic capillaries, vessels, and ducts. The lymphatic system works in close relationship with the circulatory system and is constantly in contact with the tissue fluid through which 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 structure of the peripheral lymphatic system includes specific formations - The lymph nodes, which are maximally located in the human body, for example, in the inguinal region, in the area of ​​\u200b\u200bthe armpit, at the base of the mesentery of the small intestine, and others. Lymph nodes are assigned the protective role of "filters", which boils down to the production of lymphocytes, immune bodies, and the destruction of pathogenic bacteria. Lymph nodes are the custodians of lymphocytes and phagocytes. They are responsible for the immune response and form an 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) produced and stored in the bone marrow. It is they who form specific antibodies, which are a "counterweight" to only one type of antigen. How many antigens enter the body, so many types of antibodies are formed to neutralize foreign agents during the immune response. B cells show their activity 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 cells, in turn, is divided into T-helpers (T-helper cells) and T-suppressors. T-helpers play a leading role in the protective reaction of the body, 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 response in time if the antigen is already neutralized and it is necessary active work the immune system no longer exists.

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

plays an important role in the development of the immune response phagocytes, which actively attack and destroy antigens. Among phagocytes, macrophage, which is called the "big destroyer", is of particular interest. It envelops and absorbs antigens or damaged cells, so that, having “digested” them, it finally breaks them down into their constituent parts.

Immune responses are based on 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 the processes of tissue regeneration 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. Cellular immune response develops due to T-lymphocytes, which eventually form cell-mediated immunity. These two types of immune reactions are involved in the destruction of foreign proteins that have invaded the body or formed by the tissues and organs themselves.

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

Basically, antibodies are proteins. Y-shape, which are able to attach to foreign proteins by a kind of "key-lock" mechanism. The top of the antibody, which has the shape of "V", is fixed on a foreign protein, and the lower part in the form of "I" in the form of a bridge is connected to the phagocyte. The phagocyte, in turn, removes the antigen-antibody complex from the body, 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 response that has its own characteristics. In some cases, B-lymphocytes, when they encounter an antigen, do not turn into plasma cells, but instead they send a signal to T-lymphocytes for help to fight foreign proteins. The T-lymphocytes that came to the rescue, when confronted with "strangers", begin to produce specific chemicals called "lymphokines", which serve as a catalyst for the activation of a large number of different immune cells. All cells, in turn, begin to actively divide and capture a foreign cell for its destruction. A feature of the cellular immune response is that antibodies do not take part in it.

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

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

This system is an obstacle to infections (bacterial, viral, fungal). When the immune system fails, the likelihood of developing infections increases, this 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). Plays the main role a complex system circulation, which consists of lymphatic ducts connecting the lymph nodes.

A lymph node is an oval-shaped formation of soft tissues, 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 looks like a large lymph node. The spleen has a variety of functions, including a blood filter, storage for blood cells, and production of lymphocytes. It is in the spleen that old and defective blood cells are destroyed. The spleen is located in the abdomen under the left hypochondrium near the stomach.

Thymus gland (thymus) - this organ is located behind the sternum. Lymphoid cells in the thymus proliferate and "learn". In children and people young age the thymus is active, the older the person, the less active the thymus becomes and decreases in size.

Bone marrow is a 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 circulatory system, consisting of lymphatic ducts that connect the lymph nodes and transport the lymphatic fluid.

Lymph fluid (lymph) is a colorless fluid that flows through the lymphatic vessels, it contains many lymphocytes - white blood cells that are 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.). Most important species lymphocytes (B-lymphocytes and T-lymphocytes), they work together with other immune cells and do not allow foreign substances (infections, foreign proteins, etc.) to invade the body. At the first stage, the body "teaches" T-lymphocytes to distinguish foreign proteins from normal (self) 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 the person reaches adolescence, and the thymus decreases in size and loses its activity.

An interesting fact is that in many autoimmune diseases, and in multiple sclerosis also, the immune system does not recognize healthy cells and tissues of the body, but treats them as foreign, 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 connects organs and tissues that guarantee the protection of the body from genetically alien cells and substances that come from environment. In terms of organization and mechanisms of functioning, it is similar to the nervous system.

Both 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, while the peripheral organs include the lymph nodes, spleen, tonsils, and appendix.

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

Research History

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

The word immunity comes from the Latin immunis, which means "clean of something." Initially, it was believed that immunity protects the body only from infectious diseases. However, the studies of the English scientist P. Medawar in the middle of the twentieth century proved that immunity provides protection in general from any alien and harmful interference in the human body.

At present, 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 and threatening to it. It is clear that if people did not have immunity, they simply could not exist, and its presence makes it possible to successfully fight diseases and live to old age.

The work of the immune system

The immune system has developed long years human evolution and acts as a well-oiled mechanism, and helps fight disease and harmful environmental influences. Its tasks include recognizing, destroying and removing from the body both foreign agents penetrating from the outside, and 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 "aliens". Among them are viruses, bacteria, poisonous substances of plant or animal origin, protozoa, fungi, allergens. Among them, she includes the cells of her own body that have turned into cancerous and therefore become “enemies”. Its main goal is to provide protection from all these "outsiders" and maintain integrity internal environment organism, its biological identity.

How is the recognition of "enemies"? This process takes place at the genetic level. The fact is that each cell carries its own, inherent only this person genetic information (you can call it a label). Her immune system analyzes when it detects penetration into the body or changes in it. If the information matches (the label is available), then it's your own, if it doesn't match (the label is missing), it's someone else's.

In immunology, foreign agents are called antigens. When the immune system detects them, defense mechanisms immediately turn on, and a fight 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 - this is how the body fights the disease.

allergic reactions

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

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

Internal allergens are the body's own tissues, usually with altered properties. For example, during burns, the body perceives dead tissues 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 acts on the body for the first time, antibodies with increased sensitivity to it are produced and accumulated. When this allergen enters the body again, it turns out allergic reaction, for example, skin rashes, various tumors appear.

The environment around us - air, water, soil, objects contain a lot of microorganisms that can harm human health. But due to the fact that the immune system stands guard over our well-being, in most cases this still does not happen. The immune system every minute "fights" with the army of bacteria and viruses, safely "beating off" all these malicious "attacks".

The human immune system is very complex. It includes several organs interconnected by a continuous network of lymphatic ducts.

The structure of the human immune system

The organs of the immune system include:

• Bone marrow;
• thymus (thymus gland);
• spleen;
• lymph nodes and islets of lymphatic tissue.

Bone marrow

The bone marrow is located in the spongy substance of the bone tissue. Total weight of this organ is 2.5–3 kg. The bone marrow is a concentration of stem cells, which are the ancestors of all the blood cells we need.

Approximately 50% of the main weight of the bone marrow is the accumulation of hematopoietic vessels, which provide the delivery of oxygen and necessary tissues to the tissues. chemical compounds. The porous structure of the vascular wall creates the conditions for the penetration of nutrients.

There are two different types of bone marrow - red and yellow, between which there is no clearly defined border. The basis of the red bone marrow is hematopoietic tissue, and the yellow one is fatty. The red brain produces blood cells, monocytes and B-lymphocytes. The yellow brain is not involved in the formation of blood cells, but in some situations (for example, with blood loss), small foci of hematopoiesis may appear in it.

Over the years, the volume of red bone marrow in bone tissue decreases, and yellow, on the contrary, increases. This is due to the fact that from the moment of puberty to old age, the processes of hematopoiesis begin to steadily fade away.

thymus

The thymus (thymus gland) is located in the middle chest, in the retrosternal space. The shape of the thymus is a bit like a fork with two prongs (hence the name - the thymus gland). At the time of birth, the weight of the thymus is 10-15 grams. In the first three years of life, the thymus gland grows extremely rapidly.

From the age of three to twenty years, the thymus mass remains the same and is about 26-29 grams. Then the involution (reverse development) of the organ begins. In older people, the mass of the thymus does not exceed 15 grams. With age, the structure of the thymus also changes - the thymus parenchyma is replaced by adipose tissue. In the elderly, this organ is 90% fatty.

The thymus gland has a bipartite structure. The upper and lower lobes of the gland are different size and form. Outside, it is covered with a connective tissue capsule. The connective tissue also penetrates into the thymus, thereby dividing it into lobules. In the gland, a cortical layer is isolated, in which growth and “inoculation of working skills” take place in lymphocytes “born” in the bone marrow, and a medulla, the bulk of which is made up of glandular cells.

The process of "achieving maturity" by lymphocytes, which occurs in the thymus gland, is extremely significant for immunity and the human immune system. In infants with congenital defects of the thymus - underdevelopment or complete absence of this organ, the functional development of the entire lymphatic system is disrupted, therefore life expectancy with this pathology rarely exceeds 12 months.

Spleen

The spleen is located on the left under the ribs and has the shape of a flattened and elongated hemisphere. In adults, the length of the spleen is 10-14 cm, the width is 6-10 cm, and the thickness is 3-4 cm. The weight of the organ in a man aged 20-40 is 192 grams, in a woman - 153 grams. Scientists have found that from 750 to 800 ml of blood passes through the spleen every day. Here, the formation of class M and J immunoglobulins occurs as a reaction to the intake of antigens, and the synthesis of factors that stimulate phagocytosis by leukocytes and macrophages. In addition, the spleen is a biological filter for xenobiotics, dead blood cells, bacteria and microflora.

The lymph nodes

Lymph nodes act as biological filters in the body for the lymphatic fluid flowing through them. They are located along the flow of lymph through the lymphatic vessels from organs and tissues.

As a rule, lymph nodes lie in groups of two to several dozen nodes. Outside, the lymph nodes are protected by a capsule, inside which there is a stroma, consisting of reticular cells and fibers. Each lymph node includes from 1-2 to 10 small arteries that supply it with blood.

Islands of lymphatic tissue

Accumulations of lymphatic tissue located in the mucous membrane are also called lymphoid formations. Lymphoid formations are found in the pharynx, esophagus, stomach, intestines, respiratory organs, urinary tract.

Islets of lymphatic tissue in the pharynx are represented by 6 tonsils of the lymphoid pharyngeal ring. The tonsils are a powerful accumulation of lymphoid tissue. From above, they are uneven, which contributes to the retention of food and creates a breeding ground for the reproduction of bacteria, which, in turn, serves as a trigger for triggering immunological processes.

Lymphoid formations of the esophagus are lymph nodes deep in the folds of the esophagus. The task of the lymphoid formations of the esophagus is to protect the walls of this organ from foreign tissue and antigens that enter the body with food.

Lymphoid formations of the stomach are represented by B- and T-lymphocytes, macrophages and plasma cells. The lymphatic network of the stomach begins with lymphatic capillaries located in the mucous membrane of the organ. Lymphatic vessels depart from the lymphatic network, passing through the thickness of the muscle layer. Vessels from the plexuses lying between the muscle layers flow into them.

Islets of the lymphatic tissue of the intestine are represented by Peyer's patches - group lymph nodes, single lymph nodes, diffusely located lymphocytes and the lymphatic apparatus of the appendix.

The appendix or appendix is ​​an appendage of the caecum and extends from its posterolateral wall. The thickness of the appendix contains a large amount of lymphoid tissue. It is believed that the lymphoid tissue of the appendix is ​​from 1% of all human lymphoid tissue. The cells produced here protect the body from foreign substances that enter the digestive tract along with food.

Lymphoid formations of the respiratory system are accumulations of lymphatic tissue in the mucous membrane of the larynx, trachea and bronchi, as well as diffusely located in the mucous membrane of the respiratory apparatus, lymphoid cells, called bronchial-associated lymphoid tissue. Lymphoid formations of the respiratory system protect the body from foreign particles that enter the respiratory system along with the air flow.

Lymphoid formations of the urinary tract are located in the walls of the ureters and bladder. According to scientists, in infancy, the number of lymph nodes in the ureters ranges from 2 to 11, and then increases to 11-14. In old age, the number of lymph nodes again decreases to 6-8. Lymph nodes in the urinary tract protect us from foreign substances that enter the body from the outside in an ascending way.

How the immune system works

Immunity and the immune system of the human body is a highly accurate, well-coordinated mechanism that fights bacteria and xenobiotics. All organs of the human immune system work together, complementing each other. The main task of immunity and the immune system is the recognition, destruction and removal from the body of harmful infectious agents and foreign substances, as well as the resulting mutated cells and decay products.

All substances unknown to the body that penetrate into it are called antigens. After the immune system detects the antigen and recognizes it, it begins to produce special cells - antibodies that bind the antigen and destroy it.

In humans, there are two types of immune defense - innate and acquired immunity. Innate resistance is a very ancient defense system that all living beings have. Innate immunity is aimed at destroying the cell membrane of an intruder that has entered the body.

If the destruction of the foreign cell did not occur, another line of defense comes into play - acquired immunity. The principle of its operation is as follows: when a bacterium or a foreign substance enters the human body, leukocytes begin to produce antibodies. These antibodies are strictly specific, that is, they correspond to the substance that has entered the body as two neighboring puzzles to each other. Antibodies bind and destroy the antigen, thereby protecting our body from disease.

Allergy

In some situations, the immune system of the human body reacts violently to safe environmental factors. This condition is called an allergy. Substances that provoke the manifestation of allergies are called allergens.

Allergens are divided into external and internal. External allergens are those that enter the body from the environment. It can be certain types of food, mold, wool, pollen, etc. An internal allergen is our own tissue, usually with altered properties. This happens, for example, with bee stings, when the affected tissues begin to be identified as foreign.

When an allergen first enters the human body, it usually does not cause any external changes, however, the processes of production and accumulation of antibodies occur. If the allergen enters the body again, an allergic reaction begins, which can proceed in different ways: in the form of skin rashes, tissue swelling, or an asthma attack.

Why doesn't everyone get allergies? There are several reasons for this. First, heredity. Scientists have proven that the tendency to develop allergies is passed from generation to generation. At the same time, if the mother is ill with allergies, then the child will develop an allergy with a probability of 20-70%, and if the father - only 12-40%.

The likelihood of an allergy in a child is especially high if both parents suffer from this disease. In this case, the allergy will be inherited with a probability of 80%. In addition, allergic reactions are more likely to occur in people who have been sick a lot in childhood.

Another factor contributing to the occurrence of allergies in a person is the unfavorable environmental situation in the area of ​​​​residence. Scientists have proven that in areas with polluted air, the number of allergic children is significantly greater than in areas with favorable ecology. This is especially true for allergic diseases such as bronchial asthma and allergic rhinitis (hay fever).

And this is scientific explanation: microscopic particles suspended in polluted air irritate mucosal epithelial cells respiratory tract, thereby activating them and promoting the release of anti-inflammatory cytokines.

Thus, allergic reactions are another manifestation of the immune system, the very case when, taking care of our safety, the immune system, like a loving parent, shows excessive zeal.

The human body is a cumulative system, thought out by nature to the smallest detail. Failure of any mechanism violates the integrity of the structure and the disease develops. Preventing change requires not only healthy lifestyle life, but also to properly strengthen the working capacity internal organs which is responsible for immunity.

What is human immunity made of?

Resistance is a protective system that contributes to maintaining the constancy of processes in homeostatic mechanisms, the production of antibodies to pathogens and the suppression of mutations in one's own cells.

Homeostasis - internal environment, liquid components: blood, lymph, salts, spinal, tissue, protein fractions, fat-like compounds and other substances that form metabolic processes necessary for the normal course of physiological and chemical reactions leading to a full and healthy life. By maintaining the relative constancy of processes, a person is protected from pathogenic and dangerous microorganisms. A change in homeostatic indicators indicates the presence of a malfunction in the functioning of resistance and a violation of the full performance of the whole organism.

The immune system consists of an innate, genetically inherent resistance status, as well as acquired types of immunity to foreign agents.

The non-specific type is responsible for 60% protection. Appearing in the prenatal state, after birth, resistance in a child is capable of:

• Distinguish cellular structure according to the principle of one's own or someone else's;
• Activate phagocytosis;
• Compliment system: globulins that cause a specific immune response sequence;
• Cytokines;
• glycoprotein bonds.

Thanks to well-established mechanisms and reactions in the body, in the presence of a threat, processes are triggered to detect, absorb and destroy foreign agents.

A specific type of resistance is developed by direct contact with the antigen. Improves mechanisms throughout life. Implemented:

• Humoral reactions - the formation of protein antibodies immunoglobulins. They are distinguished by structure and functionality: A, E, M, G, D;
• Cellular - involves active participation in the destruction of a disease-causing object by the bodies of the T-type lymphocytic system - thymus dependent, these include suppressors, killers, helpers, cytotoxic.

All structures, both specific and non-specific, work together and provide strong protection, forming an increase in the immune response from local, that is, local resistance, to the activation of all resistance mechanisms as the infection spreads.

Classified into:

• Congenital - an individual genetic feature that prevents or causes a disease of a certain type. For example, a person is not susceptible to severe pathologies that affect animal organisms;
• Acquired - a manifestation of the function of remembering a foreign object and enhancing the action of defense mechanisms against the re-invasion of infection, since immunity has developed in the form of an antibody.

It is also considered in the types of resistance:

• Natural, produced by direct contact with the antigen;
• Artificial - obtained by introducing vaccines, sera, immunoglobulins.

The body's resistance, like any other system, is subject to diseases classified by the presence and activity of the course of reactions:

• Allergy;
• Inadequate effect on native cells;
• Lack of immunity abilities.

To provide reliable protection methods of prevention and strengthening of resistance are used:

• Vaccination;
• Taking vitamins and minerals;
• Proper nutrition;
• Healthy mobile lifestyle.

Where is

What is included in the human immune system - each part carries a certain functionality and is conditionally divided into:

• Central;
• Peripheral.

Which organ is responsible for human immunity - a full-fledged resistant aggregate connects all tissues and central anatomical structures between its parts.

The location of the main elements of immunity is clearly shown by the diagrams of the human structure:

• Adenoids, tonsils;
• Jugular vein;
• Thymus;
• Lymph nodes and ducts: cervical, axillary, inguinal, intestinal, afferent;
• Spleen;
• Red marrow.

Also in the human body, a network of lymph nodes is common, providing control over every part of the body.

Competent cells of the resistant system are constantly circulating in the blood and other fluids, providing instant recognition, dissemination of information about the discovery of a stranger and the selection of attack mechanisms to destroy the pathogen.

How is it produced

In the human body, which organ is responsible for immunity? great importance, since the mechanism of the onset and course of the immune response consists of cumulative sequential reactions and functions of nonspecific resistance, humoral and cellular protection.

The primary line of defense is to prevent infection from entering internal structures. These include: healthy skin, mucous membranes, natural secretory fluids, blood-brain barriers. As well as special protein compounds - interferon.

The second direction of the protective elements activates the activity when the infection has directly entered the body. There are systems:

• Antigen recognition - monocytes;
• Execution and destruction - lymphocytes of type T, B;
• Immunoglobulins.

Also, an allergic reaction of a delayed or rapid type to an irritant is considered part of the resistant response.

In the human body, protective immunocompetent cells are formed:

• In the first case in the spleen: phagocytes, soluble bodies: cytokines, complement system, interleukins, glycoprotein;
• In the second - the elements go through the process of formation from stem cells getting into the thymus. Ripened, they spread throughout the body and accumulate in the lymphoid tissue, nodes.

Mechanism of the immune response:

• Upon penetration, a chemokine is formed that causes inflammation and attracts resistant bodies;
• Increased activity of phagocytes and macrophages;
• Formation of immunoglobulins;
• Selection of the reaction to ensure the connection of the antibody-antigen.

Functions

The main features of the internal structures included in the resistance system are best viewed in the form of a table.

organs of immunity	characteristic
Red bone marrow	Semi-liquid substance of a spongy consistency with a dark burgundy tint. It is located depending on age: a child - all bones, adolescents and the older generation - cranial bones, pelvis, ribs, sternum, spine.	Provides hematopoiesis: leukocytes, platelets. erythrocytes, full resistance: lymphocytes (Supports the maturation process of type B, communication with type T cells), macrophages, stem elements.
Thymus	Appears in utero. Decreases with age. It is located in the upper part of the sternum in the form of lobes covering the trachea.	Formation of immune hormones, development of protective antibodies. Participates in metabolic processes, including regulating the mineralization of the bone structure. Provides neuromuscular communication.
Spleen	Oval organ in the form of a gland. It is located at the top of the peritoneum behind the stomach.	Stores a supply of blood, protects against the destruction of bodies. Contains a stock of mature lymphocytes. Forms the ability to produce antibodies and immunoglobulins. Activates humoral reactions. The main functions are: recognition of pathogenic objects, as well as the processing and disposal of old and defective heme bodies.
Types of lymphoid tissue:
tonsils	Located in the throat.	Provides local border immunity of the upper respiratory tract. Supports the microflora of the mucous membranes in the mouth.
Peyer's patches	Distributed in the intestine.	form a resistant response. They prevent the growth of opportunistic and pathogenic fauna. Normalize and respond to the process of maturation of lymphocytes.
	They are located in the armpits, groin, and in other places along the path of lymph flow. There are about 500 of them in the body. They have the most varied form.. is a capsule covered with connective tissue with internal system sinuses. On the one hand - an entrance for arteries and nerves, on the other - vessels and venous channels.	Contribute to the delay of pathogens that have penetrated into the lymph. Actively takes part in the formation of immune and plasma cells.
immunocompetent cells	Lymphocytes of the type: B - antibody producers; T - stem cells of the red bone marrow, maturing in the thymus,	They provide a resistant response, determine the strength of reactive processes, form humoral mechanisms. Capable of remembering an antigen.

For the implementation of a specific function of supervision over the genetic constancy of the internal environment, the preservation of biological and species individuality in the human body, there is the immune system. This system is quite ancient, its beginnings were found in cyclostomes.

How the immune system works based on recognition "friend or foe" as well as the constant recycling, reproduction and interaction of its cellular elements.

Structural-functionalelements of the immune system

The immune system is a specialized, anatomically distinct lymphoid tissue.

She scattered throughout the body in the form of various lymphoid formations and individual cells. The total mass of this tissue is 1-2% of body weight.

IN anatomically the immune system underdivided intocentral Andperipheral organs.

to the central authorities immunity include

Bone marrow

thymus (thymus gland),

To the peripheral- lymph nodes, accumulations of lymphoid tissue (group follicles, tonsils), as well as the spleen, liver, blood and lymph.

From a functional point of view The following organs of the immune system can be distinguished:

reproduction and selection of cells of the immune system (bone marrow, thymus);

control of the external environment or exogenous intervention (lymphoid systems of the skin and mucous membranes);

control of the genetic constancy of the internal environment (spleen, lymph nodes, liver, blood, lymph).

main functional cells are 1) lymphocytes. Their number in the body reaches 10 12 . In addition to lymphocytes, among the functional cells in the lymphoid tissue include

2) mononuclear and granularleukocytes, mast and dendritic cells. Some cells are concentrated in individual organs of the immune system. systems, others- free move throughout the body.

Central organs of the immune system

The central organs of the immune system are Bone marrow Andthymus (thymus). This reproduction organs andlectures cells of the immune system. It's happening here lymphopoiesis - birth, reproduction(proliferation) and lymph differentiationquotes to the stage of precursors or mature non-immune (naive) cells, as well as their

"education". Inside the human body, these organs seem to have a central location.

In birds, the bursa of Fabricius is one of the central organs of the immune system. (bursa Fabricii), localized in the area of ​​the cloaca. In this organ, the maturation and reproduction of a population of lymphocytes - antibody producers, occurs, as a result of which they received the name B-lymphocytes Mammals do not have this anatomical formation, and its function is fully performed by the bone marrow. However, the traditional name "B-lymphocytes" has been preserved.

Bone marrow localized in the spongy bone (epiphyses of tubular bones, sternum, ribs, etc.). The bone marrow contains pluripotent stem cells, which are rodochiefs of all formed elements of blood and, accordingly, immunocompetent cells. In the stroma of the bone marrow, differentiation and reproduction occurs B-lymphocyte populationstov, which are then carried throughout the body by the bloodstream. Here are formed precedednicknames of lymphocytes, which subsequently migrate to the thymus, is a population of T-lymphocytes. Phagocytes and some dendritic cells also form in the bone marrow. It can be found and plasma cells. They are formed in the periphery as a result of the terminal differentiation of B-lymphocytes, and then migrate back to the bone marrow.

Thymus,orthymus, or goiterclimb, located in the upper part of the retrosternal space. This organ is distinguished by a special dynamics of morphogenesis. The thymus appears during fetal development. By the time a person is born, his mass is 10-15 g, he finally matures by the age of five, and maximum size reaches 10-12 years of age (weight 30-40 g). After the period of puberty, the involution of the organ begins - the lymphoid tissue is replaced by adipose and connective tissue.

The thymus has a lobular structure. In its structure distinguish between cerebral and corticallayers.

In the stroma of the cortex there is a large number of epithelial cells of the cortex, called "nurse cells", which, with their processes, form a fine-meshed network where "ripening" lymphocytes are located. In the borderline, cortical-medulla layer, there are dendritic cells of the type musa, and in the brain - epithelial cells Precursors of T-lymphocytes, which were formed from a stem cell in the bone marrow, enter the cortical layer of the thymus. Here, under the influence of thymic factors, they actively multiply and differentiate (turn) into mature T-lymphocytes, A also "learn" to recognize foreign antigenic determinants.

P The learning process consists of two stages, separated by place and time, and Ivyochaet"positive" And"negative » selection.

positive selection. Its essence lies in the "support" of clones T-lymphocytes, whose receptors effectively bound to self-MHC molecules expressed on epithelial cells, regardless of the structure of the incorporated self-oligopeptides. Cells activated as a result of contact receive a signal for survival and reproduction (thymus growth factors) from cortical epitheliocytes, and non-viable or non-reactive cells die.

"Negative" selection carry out dendritic cells in the border, cortical-medulla zone of the thymus. Its main goal is the "culling" of autoreactive clones of T-lymphocytes. Cells that respond positively to the MHC-autologous peptide complex are destroyed by inducing apoptosis in them.

The results of selection work in the thymus are very dramatic: more than 99% of T-lymphocytes do not withstand the test and die. Only less than 1% of cells turn into mature non-immune forms capable of recognizing only foreign biopolymers in combination with autologous MHC. Every day, about 10 6 mature "trained" T-lymphocytes leave the thymus with blood and lymph flow and migrate to various organs and tissues.

The maturation and "training" of T-lymphocytes in the thymus is essential for the formation of immunity. It was noted that the essential absence or underdevelopment of the thymus leads to a sharp decrease in the effectiveness of the immune defense of the macroorganism. This phenomenon is observed with a congenital defect in the development of the thymus - aplasia or hypoplasia.