is a collection of lymphoid tissues and organs of the body that provide protection for the body from genetically foreign cells or substances coming from outside or formed in the body. The organs of the immune system containing lymphoid tissue perform the function of protecting the constancy of the internal environment (homeostasis) throughout the life of the individual. They produce immunocompetent cells primarily lymphatic and also plasma cells, include them in the immune process, ensure the recognition and destruction of cells and other foreign substances that have entered the body or formed in it, bearing signs of genetically foreign information. Genetic control is carried out by populations of T- and B-lymphocytes functioning together, which, with the participation of macrophages, provide the immune response in the body. The terms T- and B-lymphocytes were introduced in 1969. English immunologist A. Royt.
Immune system is an independent system, concept and term (Immune system) appeared in the 1970s.
The immune system has 3 morphofunctional features:
1) it is generalized throughout the body;
2) its cells constantly circulate through the bloodstream;
3) it has the unique ability to produce specific antibodies against each antigen.
The main “person”, the central “figure” of the immune system is lymphocyte.
Despite the fact that theoretical immunology has big story from the time of L. Pasteur (19th century) until the 1960s, and clinical immunology began to flourish from the 1960s, the anatomical side of the immune system until the mid-1970s. was completely unknown. For example, until recently, lymph nodes were classified as organs of the lymphatic system, the appendix was considered atavistic: an “unnecessary” organ, the spleen “migrated” from one system to another. Only in the last 20-25 years has the range of organs and structures included in the immune system been anatomically determined. This was facilitated by practical experience provided by life itself. Until the 1970s In some foreign countries, “prophylactic” removal of the tonsils and appendixes in children was widely practiced, and several years after the operation, the incidence of tumors of the head, neck and abdominal organs sharply increased in these people. Therefore, in the 1970s. There was an urgent ban on the removal of tonsils and appendixes without direct evidence. It turned out that both the palatine tonsils and the appendix are organs of the immune system that perform a protective function. In the mid-1980s. After the emergence of HIV infection, which selectively affects immunocompetent cells (T-lymphocytes) and leads to the development of immunodeficiency, it was possible to assemble the organs of the immune system into a single whole.
The immune system includes organs that have lymphoid tissue.
Lymphoid tissue has 2 components:
1) stroma - reticular supporting connective tissue, consisting of reticular cells and reticular fibers;
2)lymphoid cells : lymphocytes of varying degrees of maturity, plasma cells, macrophages, etc.
Thus, reticular tissue and lymphoid cells together make up the immune system. The organs of the immune system include: bone marrow, in which lymphoid tissue is closely related to the hematopoietic tissue, thymus (thymus gland), lymph nodes, spleen, accumulations of lymphoid tissue in the walls of the hollow organs of the digestive, respiratory systems and urinary tract (tonsils, group lymphoid plaques, single lymphoid nodules). These organs are often called lymphoid organs, or organs of immunogenesis.
Functionally, the organs of the immune system are divided into central and peripheral.
TO central authorities The immune system includes the bone marrow and thymus. IN bone marrow B-lymphocytes (burso-dependent) and precursors of T-lymphocytes (along with other blood cells) are formed from pluripotent stem cells. IN thymus differentiation occurs of T-lymphocytes (thymus-dependent), formed from the precursors of T-lymphocytes - prethymocytes - that enter this organ. Subsequently, both of these populations of lymphocytes enter the peripheral organs of the immune system through the bloodstream. Most of the lymphocytes present in the body are recirculating (circulating many times) between different environments: organs of the immune system where these cells are formed, lymphatic vessels, blood, again organs of the immune system, etc. It is believed that lymphocytes do not re-enter the bone marrow and thymus.
To peripheral organs immune system include:
1) tonsil ring N.I. Pirogova-V. Waldeyer;
2) numerous lymphoid nodules in the walls of the hollow organs of the respiratory (larynx, trachea, bronchi), digestive (esophagus, stomach, small and large intestines, appendix, gall bladder), urinary (ureter, bladder, urethra) systems;
3) lymphoid nodules of the greater omentum (“immune factory of the abdominal cavity”) and uterus;
4) somatic (parietal), splanchnic (visceral) and mixed lymph nodes inserted along the lymph flow in an amount from 500 to 1000 (biological filters);
5) the spleen is the only organ that controls the genetic “purity” of the blood;
6) numerous lymphocytes that are found in the blood, lymph, tissues and search for foreign substances.
Bone marrow is both a hematopoietic organ and a central organ of the immune system. The total mass of bone marrow in an adult is approximately 2.5-3 kg (4.5-4.7% of body weight). About half of it is red bone marrow, the rest is yellow. Red bone marrow is located in the cells of the spongy substance of flat and short bones, the epiphyses of long (tubular) bones. It consists of stroma (reticular tissue), hematopoietic (myeloid tissue) and lymphoid (lymphoid tissue) elements at different stages of development. It contains stem cells - the precursors of all blood cells and lymphocytes. The number of lymphocytes working to protect us is six trillion (6 x 10 12 cells). Of this number of lymphocytes, the mass of which in the body of an adult is on average 1500 g, the remaining lymphocytes are found in the lymphoid tissue of the immune system organs (100 g), in the red bone marrow (100 g) and in other tissues, including lymph (1300 g) . In 1 mm 3 of thoracic duct lymph there are from 2000 to 20,000 lymphocytes. 1 mm 3 of peripheral lymph (before passing through the lymph nodes) contains an average of 200 cells.
In a newborn, the total mass of lymphocytes is approximately 150 g; 0.3% of it comes from blood. Then the number of lymphocytes quickly increases, so that in a child from 6 months to 6 years their mass is already 650 g. By the age of 15, it increases to 1250 g. During all this time, the share of blood lymphocytes accounts for 0.2% of the total mass of these cells immune system.
Lymphocytes- these are mobile round cells, the sizes of which vary from 8 to 18 microns. Most circulating lymphocytes are small lymphocytes with a diameter of about 8 µm. Approximately 10% are medium lymphocytes with a diameter of 12 microns. Large lymphocytes (lymphoblasts) with a diameter of about 18 microns are found in the proliferation centers of the lymph nodes and spleen. Normally, they do not circulate in the blood and lymph. It is the small lymphocyte that is the main immunocompetent cell. The mid-lymphocyte represents the initial stage of differentiation of the B lymphocyte into a plasma cell.
Among lymphocytes there are 3 groups: T-lymphocytes (thymus-dependent), B-lymphocytes (bursal-dependent) and zero.
1) T lymphocytes arise in the bone marrow from stem cells that first differentiate into prethymocytes. The latter are transported through the bloodstream to the thymus gland (thymus), in which they mature and turn into T-lymphocytes, and then, bypassing the bone marrow, settle in the lymph nodes, spleen or circulate in the blood, where they account for 50-70% all lymphocytes. There are several forms (populations) of T-lymphocytes, each of which performs a specific function. One of them - T-helpers (helpers) interact with B-lymphocytes, turning them into plasma cells that produce antibodies. Another - T-suppressors (oppressors) block excessive reactions and activity of B-lymphocytes. Third - T-killers (killers) directly carry out cellular immune reactions. They interact with foreign cells and destroy them. In this way, T-killers destroy tumor cells, cells of foreign transplants, and mutant cells, which maintains genetic homeostasis.
2) B lymphocytes develop from stem cells in the bone marrow itself, which is currently considered as an analogue of the bursa of Fabricius (bursa) - a cellular accumulation in the wall of the cloacal intestine in birds. From the bone marrow, B lymphocytes enter the blood, where they account for 20-30% of circulating lymphocytes. Then, with the blood, they populate the bursa-dependent zones of the peripheral organs of the immune system (spleen, lymph nodes, lymphoid nodules of the walls of the hollow organs of the digestive, respiratory and other systems), where effector cells differentiate from them - memory B lymphocytes and antibody-forming cells - plasmacytes that synthesize immunoglobulins five different classes: IgA, IgG, IgM, IgE, IgD. The main function of B lymphocytes is to create humoral immunity by producing antibodies that enter body fluids: saliva, tears, blood, lymph, urine, etc. Antibodies bind to antigens, allowing phagocytes to engulf them.
3)Null lymphocytes do not undergo differentiation in the organs of the immune system, but, if necessary, are able to transform into B- and T-lymphocytes. They account for 10-20% of blood lymphocytes.
Morphologically, T and B lymphocytes are cells that are indistinguishable under a light microscope. However, a scanning electron microscope reveals microvilli (antigen recognition receptors) on B lymphocytes that are absent on T lymphocytes.
In the structure and development of the immune system organs in ontogenesis, there are 3 groups of patterns. Some of them are typical for all organs of the immune system, others - only for central organs, and others - only for peripheral organs of the immune system.
General patterns for all organs of the immune system.
1) The working tissue (parenchyma) of the organs of the immune system is lymphoid tissue.
2) All organs of the immune system are formed early in embryogenesis.
Thus, bone marrow and thymus begin to develop at 4-5 weeks of embryogenesis, lymph nodes and spleen - at 5-6 weeks, palatine and pharyngeal tonsils - at 9-14 weeks, lymphoid nodules of the appendix and lymphoid plaques of the small intestine - at 14-16 week, single lymphoid nodules in the mucous membrane of the internal hollow organs - at 16-18 weeks, etc.
3) The organs of the immune system at the time of birth are morphologically formed, functionally mature and ready to perform immune defense functions. Otherwise, it would be difficult to imagine that the child would survive. Thus, red bone marrow, containing stem cells, myeloid and lymphoid tissue, fills all bone marrow cavities by the time of birth. The thymus in a newborn has the same relative mass as in children and adolescents, accounting for 0.3% of body weight. In many peripheral organs of the immune system (tonsils, appendix, small and large intestines, etc.) the newborn already has lymphoid nodules, including those with reproductive centers. The presence of such nodules indicates the complete morphological and functional maturity of lymphoid tissue in the organs of the immune system.
4) The organs of the immune system reach their maximum development (weight, size, number of lymphoid nodules, presence of reproduction centers in them) in childhood and adolescence. All lymphoid organs reach the peak of their development by 16 years, and lymphoid nodules in the organs of immunogenesis - by 4-6 years. This is why the “prophylactic” removal of tonsils and appendixes in the 1960s. in children in some countries led to the appearance of organ tumors in the relevant areas several years after the operation.
5) In all organs of the immune system, early age-related involution (reverse development) of lymphoid tissue and its replacement by adipose and fibrous connective tissue is observed. By the age of 20-25, all lymphoid organs become the same as those of 50-60 year old people, i.e. The immune system must be protected from a young age and not destroy the existing immune defense system.
Thus, about half of the red bone marrow, starting from 10-15 years of age, gradually turns into fatty, inactive yellow bone marrow. Similarly, from the age of 10-15 years, the amount of lymphoid tissue in the thymus begins to decrease and is replaced by adipose tissue. The latter at 50 years of age makes up 88-89% of the mass of the thymus, and in newborns it is only 7%. In children and adolescents, there is a progressive decrease in the number of lymphoid nodules in the peripheral organs of the immune system. At the same time, the nodules themselves become smaller, and reproductive centers disappear in them. Due to the proliferation of connective tissue, the smallest lymph nodes become impassable for lymph and are excluded from the lymphatic bed. By the age of 60, very little lymphoid tissue remains in the appendix; it is filled with fat (out of 600-800 lymphoid nodules in children and adolescents, their number decreases to 100-150), which together leads to a decrease in the body’s defenses, as evidenced by the increase in the number of tumors and other diseases in older people. At the same time, as the total mass of lymphoid tissue in the body decreases, qualitative compensatory changes apparently occur in the organs of the immune system, providing immune protection at a fairly high level in most people.
Patterns (features) of the central organs of the immune system.
1) The central organs of the immune system are located in places well protected from external influences. For example, the bone marrow is located in the medullary cavities, the thymus is in the chest cavity behind the wide and strong sternum.
2) Both the bone marrow and the thymus are the site of differentiation of lymphocytes from stem cells. In the bone marrow, B-lymphocytes and prethymocytes (precursors of T-lymphocytes) are formed from pluripotent stem cells through complex differentiation, and in the thymus, T-lymphocytes (thymocytes) are formed from prethymocytes received from the bone marrow with the blood.
3) Lymphoid tissue in the central organs of the immune system is in a unique microenvironment and symbiosis with other tissues. In the bone marrow this environment is myeloid tissue, in the thymus it is epithelial tissue. Apparently, the presence of myeloid tissue or the substances secreted by it in a certain way influences the development of stem cells, as a result of which their differentiation is directed towards the formation of B lymphocytes and prethymocytes. In the thymus, where biologically active substances (hormones) are produced: thymosin, thymopoietin, thymic humoral factor, differentiation of prethymocytes follows the path of formation of T-lymphocytes. Probably, the epithelioreticulocytes and special flattened epithelial bodies (A. Hassal's bodies) present in the thymus, as well as the mentioned biologically active substances, are the factors due to which thymus-dependent lymphocytes are formed.
Patterns for peripheral organs of the immune system.
1) All peripheral organs of the immune system are located on the paths of possible introduction of foreign substances into the body or on the paths of their passage in the body. They form here a kind of border, security zones: “guard posts”, “filters” containing
lymphoid tissue. Thus, the tonsils form the lymphoid ring N.I. Pirogov - V. Waldeyer at the entrance to the digestive system and respiratory tract. Lymphoid nodules, lymphoid plaques, as well as diffuse lymphoid tissue in the mucous membrane of the digestive, respiratory and urinary tract organs are located under the epithelial cover of these organs at the border with the external environment (food masses, air with microbes contained in it, dust particles, urine).
Lymph nodes, being biological filters, lie on the paths of lymph flow from organs and tissues towards the lower parts of the neck, where lymph flows into the venous system. The spleen (the only organ that carries out immune control of the blood) is located on the paths of blood flow from the aorta through the splenic artery to the portal vein system. In addition to these organs of immunogenesis, a large army of lymphocytes, located in the blood, lymph, organs and tissues, performs the functions of searching, finding, recognizing and destroying genetically foreign substances that have entered the body or formed in it (particles of dead cells, mutant cells, tumor cells, microorganisms, etc.).
2) The lymphoid tissue of the peripheral organs of the immune system, depending on the magnitude and duration of the antigenic effect, complicates its structure and passes 4 stages(stages of) differentiation.
The first stage (diffuse lymphoid tissue) should be considered the appearance of hollow internal organs in the mucous membrane and in other anatomical formations (a kind of antigen-dangerous places) diffusely scattered lymphoid tissue. These are lymphocytes located in the lamina propria of the mucous membrane under the epithelial cover, forming several rows of cells. Plasma cells and macrophages are also found there. The presence of lymphoid cells in the mucous membrane can be considered as the body’s readiness to meet, recognize and neutralize foreign substances (antigens) that are in the external environment (in the digestive canal, respiratory and urinary tracts).
Second stage (prenodule formation) development of peripheral organs of the immune system is the formation accumulations of lymphoid cells. In the mucous membrane of hollow internal organs and other areas of the human body (in the pleura, peritoneum, near small blood vessels, in the thickness of the exocrine glands, etc.), in place of diffusely scattered cells of the lymphoid series, lymphocytes gather into small cell clusters. In the center of these clusters, the cells are located somewhat denser than at the periphery. Such a structure is considered as prenodular stage formation of peripheral organs of the immune system.
Third stage (nodule formation) development of lymphoid tissue in the peripheral organs of the immune system is the formation lymphoid nodules- dense clusters of cells of the lymphoid series, round or oval shape. The presence in the lymphoid tissue of such lymphoid nodules with fairly clear contours is considered as a state of high morphological maturity of the immune system organs, as their readiness to form reproduction centers for the local reproduction of lymphoid cells. Lymphoid nodules appear shortly before or shortly after birth.
The fourth final stage (establishment of own production of lymphocytes) development of lymphoid tissue, the highest degree of differentiation of the organs of the immune system should be considered the appearance in lymphoid nodules reproduction centers (germintative, light centers). Such centers appear in nodules during prolonged exposure to antigenic stimuli and indicate, on the one hand, the influence of strong and diverse factors on the body external environment, on the other hand, about the great activity of the body’s defenses. An intensive appearance of reproduction centers in lymphoid nodules is observed in children, starting from infancy. Thus, in children 1-3 years old, more than 70% of lymphoid nodules in the walls of the small intestine have reproduction centers. The lymphoid tissue of the immune system organs is characterized by the presence of lymphoid nodules both without a reproduction center and with such a center. Lymphoid nodules without a reproductive center were previously called primary lymphoid nodules, since they are formed directly in diffuse lymphoid tissue. Lymphoid nodules with a reproductive center are called secondary nodules, since the reproductive center appears as if for the second time, i.e. after the formation of the nodule itself. Reproduction centers, which are one of the places of formation of lymphocytes, contain significant quantities of lymphoblasts, lymphocytes, as well as mitotic dividing cells.
Starting from 8-18 years, the number and size of lymphoid nodules gradually decrease, and reproductive centers disappear. After 40-60 years, diffuse lymphoid tissue remains in place of the lymphoid nodules, which, as a person ages, is mostly replaced by adipose tissue.
>>anatomy and physiology
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 function of immunity is ensured by the work of the body's immune system, which includes various types of 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 of the immune system are present in almost all organs and tissues of the body. The exception is some parts of the eyes, testicles in men, and the 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 ( various types 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 the 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 located, for example, in the palatine tonsils, at the root of the tongue, on the posterior wall of the nasopharynx, in the intestines).
Lymph nodes They are a collection of lymphoid tissue (actually a collection of cells of the immune system) 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 (,). The vessels leaving the lymph node merge into a 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 the 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 the spleen contracts and releases blood into the 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).
In addition, in various organs there are so-called mesenchymal cells, which can perform an immune function. There are many such cells in the skin, liver,...
Immune system cells
The general name for cells of the immune system is 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 of a bacterial nature.
Basophils take an active part in the development of immediate allergic reactions. Once in the tissue, basophils turn into mast cells containing large amounts of histamine, a biologically active substance that 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, cancer cells or cells infected with viruses can be destroyed.
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. In general, the coordinated work of various cells of the immune system ensures reliable protection of the body from various infectious agents and its own mutated cells.
In addition to the function of protection, 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 in the human body, there are a number of nonspecific defense factors that 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 to capture certain substances (for example,) 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
What is the immune system of the human body, what is part of the organs of the immune system, what types of immunity exist, the principles of its operation, read more in this article
Immune system of the human body
From the very moment a person is born and throughout his entire life, he, unfortunately, is subjected to constant attacks and attacks of all kinds of bacteria, viruses, various infections and poisons.
The surprising thing is that a person does not get sick very often, in any case, this happens much less frequently than infection processes.
What is the reason for this?
And the reason is that a person has the so-called immunity.
In animals and humans there is an immune system, the so-called immunity, which functions thanks to the work of a number of internal organs.
These organs produce or store white blood cells, which in turn produce antibodies.
Immunity
(lat. immunitas- liberation, getting rid of something) is a set of defense mechanisms that help the body fight various foreign factors, bacteria, viruses, poisons, foreign bodies, etc.
Provides homeostasis of the body at the cellular and molecular level of organization. Implemented by the immune system. wiki
Immunity is the ability of living organisms to recognize antigens and destroy them.
Antigens are foreign bodies and substances that enter the body from the outside.
When they enter the body, the immune system immediately reacts to this and releases antibodies to fight. Antibodies suppress any activity of viruses, bacteria, toxins, etc.
The process of interaction between an antibody and an antigen is called the immune reaction (response) of the body.
When did the human immune system emerge?
This happened during the process of evolution in order to promote natural selection and the survival of the living organism.
The very essence of immunity in terms of biological meaning is to ensure the genetic integrity of the organism and preserve it throughout its individual life.
They are divided into two main types:
- central authorities;
- peripheral organs of the immune system.
The central organs are the red bone marrow and the thymus, also called the thymus gland.
Peripheral organs are the spleen, all lymph nodes in the body and Peyer's patches.
- Red bone marrow
It is liquid in structure and can be either active or inactive. This is the substance that fills everything interior space bone spongy tissue. The largest concentration of red bone marrow is found at the very ends of long bones.
In young children, active red bone marrow is located in almost all bones; in adolescents and adults, it is mainly located in the sternum, in the bones of the skull, bones of the ribs and pelvis.
The main functions of red bone marrow are hematopoiesis and the formation of immunity, the so-called immunogenesis. It always works in a constant mode and reproduces blood cells - leukocytes, erythrocytes and platelets.
- Thymus (thymus gland)
This is an endocrine gland that is located in the upper part of the chest, behind the sternum. It plays a critical role in the formation of immunity and stimulates the development of “thymus cells” in the tissue.
These cells recognize and attack foreign substances, viruses and bacteria that enter the body from outside, and they also control the production of antibodies.
Main functions of the thymus:
- participation in protecting the body from viral and bacterial invasions from the outside
- synthesis of biologically active substances and hormones
- implementation of careful selection of thymus cells (T-lymphocytes).
In a newborn baby, the thymus gland is two lobes that are connected to each other by the so-called isthmus. This isthmus contains the cortex and medulla.
The cortex is a whole network of epithelial cells containing clusters of lymphocytes.
The medulla contains a small number of lymphocytes.
The mass of the thymus increases with age and by the age of 15 reaches approximately 30 g.
- Spleen
This is an organ that is located in the abdominal cavity. It resembles the shape of an egg and has a red tint. Its weight is approximately 150-200 grams.
Main functions of the spleen:
- releasing accumulated blood, increasing the overall blood supply to the body and enriching body tissues with oxygen;
- destruction of obsolete red blood cells;
- serves as the main source of lymphocytes;
- is a filter for all kinds of dangerous bacteria, produces antibodies and provides the body with detoxification.
The spleen is in contact with the diaphragm, pancreas, colon and left kidney.
- Lymph nodes
These are numerous organs of the immune system. An adult has about five hundred of them. They are located along the path of lymph flow. These are round or oval-shaped formations, the size of which is from 2 to 20 mm. They are located at the confluence of lymphatic vessels - under the armpits, in the groin, in the neck, in the pelvic area.
The lymph node consists of a connective tissue capsule and lymphoid tissue. It serves as a barrier to the spread of infection and cancer cells throughout the body. Lymphocytes are formed in the lymph node, which actively participate in the destruction of foreign substances and cells.
Main functions of lymph nodes:
- retention of bacteria and viruses along the path of lymph flow;
- hematopoietic function.
Interesting to know!!!
Every day our body loses about 1 × 1011 blood cells, which, as they age and break down, are replaced by an equal number of new cells!
- Peyer's patches
These are nodular accumulations of oval or round shape, which are found in lymphoid tissue. They are located in the mucous membrane of the small intestine. Their diameter is from 0.5 to 3 mm.
Main functions of Peyer's patches:
- participation in the process of maturation of T- and B-lymphocytes;
- formation of the body's immune response.
Basic functions of the immune system
The ultimate goal of the immune system is the complete elimination of a foreign substance that has entered the body.
There are cellular and humoral immunity.
- Cellular immunity is the process of destroying foreign bodies with the help of cells.
- Humoral immunity is the process of removing foreign substances from the body using antibodies.
Moreover, the immune system ensures the replacement of spent cells of various organs with new ones and controls the process of regeneration of cells that are affected by infection.
Cells of the immune system (leukocytes) destroy foreign bodies and damaged cells of the body, after which they die.
The pus that forms in the tissues during any inflammation is dead leukocytes.
Leukocytes - cells of the immune system
These are blood cells white, or it would be more accurate to say that they are colorless. Their shape is round, resembling a kidney or many lobules.
The size of the leukocytes themselves is very small, and it varies - from 6 to 20 mmk. The number of leukocytes per cubic ml in the blood of an adult is approximately 5,000 to 10,000.
This process of recognition and destruction of bacteria is called phagocytosis.
What types of leukocytes are there?
1. Phagocytes (macrophages). They make up about 70% of the total number of all leukocytes in the body
Macrophages participate in the process of phagocytosis, engulfing and digesting pathogenic bacteria.
2. Lymphocytes. They are formed in the thymus and lymphoid tissue from cells of bone marrow origin.
The functions of thymic lymphocytes and lymphocytes of lymph nodes are somewhat different, complementing each other perfectly.
There are two main types of lymphocytes - T and B lymphocytes.
T lymphocytes recognize and destroy cells that carry foreign antigens, and they also form antibodies and mobilize all the body's leukocytes to fight the antigen.
There are 3 main subspecies:
- T helper cells - they recognize the antigen;
- T-killers - they destroy foreign cells;
- T-suppressors - they regulate the activity of lymphocytes, thereby preventing the excessive development of immune reactions.
b) B lymphocytes also have immune memory, they produce antibodies and destroy tumor cells.
How does the human body's immune system work?
It all depends, first of all, on what antigen has entered the body - a bacterium or a virus.
Bacteria are single-celled organisms that, depending on their shape, are divided into cocci (spherical), bacilli (rod-shaped), vibrios (comma-shaped) and spiral.
- What is the difficulty of fighting bacteria for the immune system?
Bacteria move using flagella, so they can quickly bypass clusters of phagocytes. In addition, the bacterial cell wall is very strong, and phagocytes are not able to digest it.
Moreover, bacteria release toxins that kill immune cells.
Viruses are tiny non-cellular particles that contain a single molecule of RNA or DNA.
There are several groups of viruses:
- spherical viruses;
- rod-shaped viruses;
- cuboidal;
- helical;
- 20-sided viruses.
- What is the difficulty of fighting viruses for the immune system?
Viruses, penetrating the cells of the body, multiply very quickly. In addition, phagocytes are not able to destroy them.
How T lymphocytes work:
- Bacteria are recognized by type.
- The presence of a bacteria of this type that has already entered the body is determined.
- The “answer” of T lymphocytes to B lymphocytes about what reagent needs to be prepared for destruction.
How do B lymphocytes work:
- Antibodies (immunoglobulins) are produced.
- Antibodies destroy bacteria.
- The final destruction of the foreign cell and the stopping of the immunological reaction process by T-suppressors.
How does the immune system fight the virus?
T lymphocytes, together with B lymphocytes, produce antibodies that recognize virus antigens and destroy all body cells infected by them.
Such T-lymphocytes are called cytotoxic. They stop the reproduction of any type of virus.
T lymphocytes have a “short memory”, so this process can be quite lengthy.
Types of immunity of the human body
The human body has quite a few different body defense systems. And this very diversity helps a person to be practically immune to the invasion of the body by various infections, bacteria, viruses and fungi.
At the moment, scientific medicine knows two types of immunity:
- natural immunity;
- artificial immunity.
Each of these two types is further divided into:
- active immunity;
- passive immunity.
What is natural immunity?
Active natural immunity is divided into:
- species,
- hereditary,
- acquired during a specific illness.
Species immunity is the absolute immunity of the body to infectious agents, which is due to certain biological reasons from the birth of a person or animal.
We can say about this type of immunity that it is hereditary and is inherited in the same way as a number of other genetic characteristics (features).
Hereditary immunity (also called nonspecific, constitutional, innate) is transmitted to the body along with other genetic hereditary material.
It is usually characterized by atomic, physiological, cellular, and molecular features that are hereditary.
This type of immunity, as a rule, does not have particularly strict specificity for antigens, and it does not have a memory of the very first contact with a specific foreign agent.
For example, research has already established that many people from birth are absolutely not susceptible to many types of infection, to many diseases, even to very strong pathogens. It has already been proven that some people are immune to even such terrible diseases as tuberculosis and AIDS!
What is acquired or passive immunity?
Acquired immunity is a type of immunity that develops throughout the life of a person or animal. It is not present from the moment of birth and can be inherited.
Acquired immunity is formed in the body during the course of the disease, during its course. When the body is sick, the body itself is able to produce antibodies to a certain type of infection from the outside, and also has the ability to retain a certain kind of memory of this antigen in its cells in case of repeated illness with the same disease or invasion of a foreign agent into the body.
The body then becomes immune to this type of harmful agent.
The body's immunity itself can last a lifetime, it can be short-term, or it can be quite long-term.
For example, after a person has suffered from a disease such as measles, immunity to this virus remains for the rest of his life.
If a person has had typhoid fever, then immunity will be quite long, but not lifelong.
But after suffering from any type of flu, immunity to this virus will be short-lived and short-lived.
Passive natural immunity occurs in the body when antibodies are transferred to the unborn child in the womb of a pregnant woman through the placenta. Also when a woman is breastfeeding a baby. Through mother's milk, he receives immunity to certain viruses and microbes.
This helps the baby to be immune to many pathogens in the future and to have strong immunity to them for about the first six months of his life.
Then passive natural immunity gradually weakens and disappears.
Immune system of the human body - video
What is artificial immunity?
Active artificial immunity develops after a certain type of vaccine has been introduced into the body.
After such manipulation, the body begins to actively develop immunity - its own immunity to a certain type of infection and produces its own antibodies to it.
Passive artificial immunity begins to form after a certain therapeutic serum is introduced into the body, which already contains antibodies that were previously produced in the donor’s body.
In this case, the immune defense reacts rather passively and does not take part in the development of the necessary immune response of the body.
This method of immunization is used only when the disease itself has already begun. Passive artificial immunity is acquired in a fairly short time, very quickly. As a rule, this only takes a few hours.
But, unfortunately, it also does not last long, often up to one month at most.
Other known types of immunity?
There are three more types of immunity depending on what they develop to:
- Anti-infective immunity;
- Antitoxic immunity;
- Antitumor immunity.
Anti-infective immunity – This is immunity to germs and viruses. It resists re-infection with this type of infection, for example, infection with chickenpox.
Antitoxic immunity develops immunity to the disease toxin after introducing the serum into the body. For example, after introducing anti-tetanus serum into the body, immunity to the tetanus toxin is developed. And not to the tetanus stick itself. That is, this serum does not affect the tetanus bacillus itself, nor do the antibodies produced with its help. These antibodies simply have the ability to bind tetanus toxin. Therefore, tetanus, like many other diseases, can occur more than once during a lifetime.
Antitumor immunity t is a kind of “supervision” over the work and condition of the cells of the whole body, or more precisely, the identification and destruction of detected modified cells (malignant), potentially dangerous to health in terms of the development of tumors from them.
What is local immunity?
When antigens enter the body through the respiratory tract, through the digestive tract, through mucous membranes, and skin, the body begins to develop local immunity to them.
These are all kinds of protective methods of the body, designed to preserve its health when interacting with the external environment.
Local immunity is capable of independently, without the inclusion of general immunity, protecting internal environments from invasions of potentially dangerous foreign agents, instantly neutralizing them at the very beginning of their “encroachment” on the body.
But, despite the fact that the reserves of strength in each organism are enormous, the resources of our body can gradually run out if we do not “recharge the batteries”, in other words, we need to learn how to properly maintain our immunity and strengthen it so that it can function in a powerful mode , protecting our health!!!
There are many techniques and ways to do this.
And here the most important thing that you need to understand for yourself is that self-medication can be dangerous, especially if you already have chronic diseases, especially in the acute stage!
Therefore, when you start strengthening and strengthening your immunity, consult with your doctor about the methods that you want to use for this purpose!
This is especially true for the elderly, children, pregnant women and those with chronic diseases.
We hope that this article was able to explain the basic concept of what the immune system of the human body is.
The immune system is a complex mechanism created by nature for many years evolution of the human body. It is designed to give tough and lightning-fast responses to external threats. Under the influence of poor ecology and stress, human immunity begins to decline. Therefore, a person should know as much as possible about his immunity. What the human immune system consists of and how it functions will be discussed in this article.
In recent years, doctors have noted a constant increase in the number of infectious and inflammatory diseases. The problem is urgent, diseases tend to become chronic with periodic relapses, basic therapy is ineffective. Increased number of allergic and autoimmune diseases, malignant neoplasms, viral infections leads to increased mortality and disability. Social, environmental and medical manipulations have a negative impact on human health, and first of all there is suppression of the immune system and the occurrence of secondary immunodeficiencies.
Definition of the immune system
The immune system is a “barrier” that organs create to jointly protect the body from diseases. The main task is to identify and destroy tumor cells and pathogenic microorganisms. The immune system is entrusted with the function of recognizing many different pathogens and separating them from the biopolymers of its own cells. The main functions of the human immune system are the destruction of pathogens, foreign bodies, toxic substances or degenerated cells of the body itself.
Immune system organs
Where the immune system is located and what work it does is quite difficult to understand. You can’t touch it with your hands, and you can’t see it in the picture.
The immune system is represented by organs that produce specific “defender cells” and cells that constantly move through the blood and lymphatic vessels. Lymph is the same blood, only it is devoid of red blood cells and is saturated with cells of the immune system.
The older a person gets, the more experience he gains and the wiser he becomes. So it is with the immune system, it changes with age, improves and becomes more experienced in protecting itself.
After receiving a blood test, you should carefully read the names of the cells, among them there are those that are designed to help the body fight various “intruders”: neutrophils, granulocyte cells, monocytes (macrophages) and dendritic cells. The latter can settle in different fabrics the body and wait for the appearance of pathogens, finding them, transporting them to the immune organs.
1) Bone marrow rightfully occupies a dominant position among the immune organs. It has a hematopoietic function and gives birth to all blood cells. Next to it on a pedestal is the thymus gland (thymus). T lymphocytes born in the bone marrow are still immature. They need to be trained and trained, this happens in the thymus.
All other immune organs will be of secondary importance.
2) Spleen – filters blood from old, dead cells.
3) Lymph nodes are “filters” and destroy pathogenic bacteria. Lymphocytes and phagocytes accumulate and store. Phagocytes participate in the immune response, attack and destroy antigens. If the lymph nodes are enlarged, this indicates the presence of inflammation.
4) In the nasopharynx there is a whole conglomerate: adenoids, mucous accumulations and tonsils, which produce lymphocytes.
5) The intestinal submucosa is completely covered with lymphoid tissue (Peyer's patches).
Functions of the human immune system
Protective. Activates immediately when a “stranger” is detected. Lymphocytes rush to the site of infection. They block and destroy the pest, and then remove it from the body.
Immune memory. Having identified pathogenic bacteria once, the protective cells mark them and the next time they immediately destroy them, without wasting time on identification.
Structure of the immune system
Innate immunity is an ancient and highly developed type of defense. Appeared and improved simultaneously with man. Accumulates information about pathogenic organisms throughout the evolution of mankind. Helps the body cope with many infections: runny nose and colds.
We are already born with immune cells. They do not change throughout our lives. As they grow up and interact with each other in the lymphoid organs, they gain experience and skills, thereby improving their quality. The more often the immune system comes into contact with antigens, the stronger it becomes and the better it protects us.
Acquired immunity is everything that the body receives and develops in the process of suffering from diseases and receiving vaccinations. Such immunity is more complex in structure; it needs time to develop an immune response to the invading antigen. He will be able to fight back not only a specific microbe, but also its subspecies.
We receive powerful protection, which, when we meet the microbe again, will make this meeting invisible to us. When a subsequent virus attack occurs, it starts immune memory and the disease progresses more easily.
Why is inflammation necessary?
As soon as an infectious agent enters the body, inflammation immediately occurs. For example, you cut your finger while cleaning fish. What's happening? Since foreign cells have entered the skin, macrophages immediately sense it. By releasing special chemicals, they signal the blood vessels to dilate the vessel walls and slow down blood flow. Swelling forms, which does not allow the microbe to penetrate deeper into the tissue.
When dilating, microscopic gaps form on the walls of blood vessels. Cells from the bloodstream can come out and destroy these antigens. This is how phagocytosis occurs. Neutrophils ingest microbes and then digest them. Often in this battle they die, forming a warrior cemetery - pus. Huge numbers of neutrophils are produced every minute. The body's temperature signals that the mechanism of fighting the virus has been launched.
Failure in defense - immunodeficiency
When a person becomes particularly susceptible to infections, it is immediately clear that the immune defense is reduced. Before a microbe meets the immune system, it needs to overcome all barriers that, for some reason, may fail in defense.
Immunodeficiency is a word that is often heard. This is the most difficult condition that the body experiences. If it is acquired, then it lasts for months and years. Congenital immunodeficiency can accompany a lifetime if very serious treatment is not undertaken. It is accompanied by severe infections, which are much more difficult than in other people.
We often get infections that are quite difficult to cure. Often it is our fault, we ourselves do not treat and eradicate the problem. Failure to comply with the antibiotic dosage regimen ends with the microbe hiding, but not disappearing from the body, but, on the contrary, becoming resistant to this antibiotic. Infection of the body receives new development.
- Components of the immune system
- How to boost immunity?
Components of the immune system
The structure of the organs of the immune system is quite complex and is only slightly inferior to how the nervous system is built. Its central bodies include:
- Red and yellow bone marrow. Its purpose is to be responsible for the hematopoietic process. The spongy substances of the short bones contain red marrow. It is also found in the spongy components of flat bones. Tubular bones contain yellow marrow in their cavities. Children's bones contain only red. This type contains stem cells.
- Thymus (thymus gland). Located behind the sternum. It consists of 2 lobes: on the right side and on the left. Both lobes are divided into smaller lobules containing the cortex at the edges and the medulla in the center. The basis of the thymus gland are epithelioreticulocytes. They are responsible for the formation of a network of T-lymphocytes, the production of thymosin and thymopoietin (bioactive components). Lymphocytes are produced by the cortex, then they enter the medulla, and from there into the blood.
The immune system also contains peripheral organs. Their total weight (both of them) is about 1 kilogram.
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What organs are peripheral?
The immune system has 6 tonsils: 
- Palatal steam room. Located on both sides of the throat. It is an organ covered with several layers of squamous epithelium.
- Tubal tonsil (also steam). Its basis is lymphoid tissue. Located in the area of the auditory tube. Surrounds the opening of the pharynx.
- Pharyngeal tonsil (unpaired organ). Its location is the wall of the pharynx from above.
- Lingual tonsil (also unpaired). The place of its localization is the region of the language root.
The following organs also belong to the peripheral part of the immune system:
- Lymphoid nodules. They are located in the following systems: digestion, respiration, urination. They form a ball shape consisting of a large number of lymphocytes. Protect the body from foreign substances entering it harmful substances. If an antigenic danger arises, the process of formation of lymphocytes starts, since the centers of their reproduction are located in the nodules.
- Lymphoid plaques. Their location is the small intestine. They consist of several nodes of the same name. These plaques prevent foreign substances from entering the bloodstream or lymph. It is in the small intestine that there are especially many foreigners, since this is where the process of digesting food takes place.
- Appendix (is a vermiform appendix). It contains a lot of lymphoid nodules. They lie close to each other. The process itself is located in the border zone between the small intestine and the large intestine. It is one of the main functions of the immune system.
- Lymph nodes. They are located in places where lymph flows. The lymph nodes retain foreign substances and dead cells of the body. There they are destroyed. Lymph nodes in the body are not located one at a time. Usually there are two or more.
- Spleen. Its location is the abdominal cavity. The task of this important organ is to control the blood and its composition. The spleen consists of a capsule with trabeculae extending from it. It also contains pulp, white and red pulp. The basis of white is lymph tissue, red is reticular stroma. 78% of the entire organ is given by nature to the red pulp, which contains many lymphocytes and leukocytes, as well as other cells.
All of them are located so that they surround the place where the oral and nasal cavities enter the pharynx. If foreign substances (from food or from inhaled air) try to enter the body, then it is in this place that lymphocytes await them.
The interaction of all organs presents a complex picture. Their coordinated work, as well as the structure and functions of the immune system, provide reliable protection for the body.
Long before the baby is born, even in mother's womb, the formation of the child’s immune system begins. In order for it to develop further, the baby needs mother's milk. For the same purpose, an antigenic load is needed - contact of the child’s body with various microorganisms.
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What is the immune system responsible for?
The functions of the human immune system can be represented as the following algorithm:
- recognize a foreign element;
- destroy a stranger;
- provide maximum protection to your body.
Nothing in the body passes without a trace, including the immune response. The immune system, when it first encounters any foreign substance (infection, microbe, etc.), will definitely remember its properties. The next time you meet him, she influences him more effectively.
Bacteria appear in a baby’s life almost immediately after he is born. Many parents believe that the child should be provided with maximum sterility. But this opinion is wrong. Basic hygiene rules are necessary, but you shouldn’t go to extremes. Excessive sterility can prevent the baby's immune system from developing its properties. If mother's milk contains a certain amount of bacteria, then you should not refuse it. The child's body must learn to fight harmful substances. The functions of the immune system include fighting various viruses and bacteria.
In most cases, she copes with them before they have time to manifest their negative impact on the human body, that is, the person does not even notice that not everything is in order in the body.
But if there are too many pathogenic substances, then not every immune system will be able to cope. There are also pathogens that are beyond your control even in small quantities. good immunity. For example, cholera or chicken pox. A decrease in the functions of the immune system is manifested by frequent colds, chronic infections, and a constant temperature of 37-38°C. There are some diseases, the peculiarity of which is that a person gets them only once in his life. For example, measles. This happens thanks to the immune system, which forms a stable immunity to the disease.
