Our body has the ability to protect itself from pathogens, chemical agents, as well as from its own sick and substandard cells.
The biological meaning of immunity is to ensure the integrity and maintain the constancy of the composition of the body at the genetic and molecular level throughout its life.
Immunity is realized thanks to the immune system, which consists of central and peripheral organs. They form immunocompetent cells. TO central authorities include bone red marrow and thymus gland(thymus). Peripheral organs are the spleen, lymph nodes, as well as lymphoid tissue located in some organs. Immune defense is complex. Let's figure out what forms, types and mechanisms of immunity exist.
- Not specific immunity directed against all microorganisms, regardless of their nature. It is carried out various substances, which secrete glands of the skin, digestive and respiratory tract. For example, the environment in the stomach is highly acidic, due to which a number of microbes die. Saliva contains lysozyme, which has a strong antibacterial effect, etc. Nonspecific immunity also includes phagocytosis - the capture and digestion of microbial cells by leukocytes.
- Specific immunity is directed against a specific type of microorganism. Specific immunity is achieved through T-lymphocytes and antibodies. The body produces its own antibodies for each type of microbe.
There are also two types of immunity, each of them, in turn, is divided into two more groups.
- Natural immunity is inherited or acquired after illness. It is, accordingly, divided into congenital and acquired.
- A person acquires artificial immunity after vaccinations - the administration of vaccines, serums and immunoglobulins. Vaccination promotes the emergence of active artificial immunity, since either killed or weakened microbial cultures enter the body, and the body then itself develops immunity to them. This is how vaccines against polio, tuberculosis, diphtheria and some other infectious diseases work. Active immunity produced for years or for life.
When serums or immunoglobulins are administered, ready-made antibodies enter, which circulate in the body and protect it for several months. Since the body receives ready-made antibodies, this type of artificial immunity is called passive.
Finally, there are two main mechanisms by which immune reactions occur. These are humoral and cellular immunity. As the name suggests, humoral immunity is realized through the formation of certain substances, and cellular immunity is realized through the work of certain cells of the body.
Humoral immunity
This mechanism of immunity manifests itself in the formation of antibodies to antigens - foreign chemical substances, as well as microbial cells. B lymphocytes play a fundamental role in humoral immunity. They are the ones who recognize foreign structures in the body, and then produce antibodies against them - specific protein substances, which are also called immunoglobulins.
The antibodies that are produced are extremely specific, that is, they can only interact with those foreign particles that caused the formation of these antibodies.
Immunoglobulins (Ig) are found in the blood (serum), on the surface of immunocompetent cells (surface), and also in secretions gastrointestinal tract, tear fluid, breast milk (secretory immunoglobulins).
In addition to being highly specific, antigens also have other biological characteristics. They have one or more active centers that interact with antigens. More often there are two or more. The strength of the connection between the active center of the antibody and the antigen depends on spatial structure substances that come into contact (i.e., antibodies and antigens), as well as the number of active centers in one immunoglobulin. Several antibodies can bind to one antigen at once.
Immunoglobulins have their own classification using Latin letters. In accordance with it, immunoglobulins are divided into Ig G, Ig M, Ig A, Ig D and Ig E. They differ in structure and function. Some appear immediately after infection, while others appear later.
The antigen-antibody complex activates the complement system (protein substance), which promotes further absorption of microbial cells by phagocytes.
Due to antibodies, immunity is formed after previous infections, as well as after. They help neutralize toxins entering the body. Antibodies in viruses block receptors, preventing them from being absorbed by the body's cells. Antibodies are involved in opsonization (“wetting of microbes”), making antigens easier to ingest and digest by macrophages. 
Cellular immunity
As already mentioned, cellular immunity is carried out by immunocompetent cells. These are T-lymphocytes and phagocytes. And if the body’s protection against bacteria occurs mainly due to humoral mechanism, then antiviral, antifungal, as well as antitumor protection - due to cellular immunity mechanisms.
- T lymphocytes are divided into three classes:
- Killer T-cells (directly contact a foreign cell or damaged cells of one’s own body and destroy them)
- T helper cells (produce cytokines and interferon, which then activate macrophages)
- T-suppressors (control the strength of the immune response and its duration)
As you can see, cellular and humoral immunity are interconnected.
The second group of immunocompetent cells involved in cellular immune reactions are phagocytes. In fact, these are leukocytes of different types that are found either in the blood (circulating phagocytes) or in tissues (tissue phagocytes). Granulocytes (neutrophils, basophils, eosinophils) and monocytes circulate in the blood. Tissue phagocytes are found in connective tissue, spleen, lymph nodes, lungs, endocrine cells of the pancreas, etc.
The process of destruction of antigen by phagocytes is called phagocytosis. It is extremely important for ensuring the body's immune defense.
Phagocytosis occurs in stages:
- Chemotaxis. Phagocytes are directed to the antigen. This can be facilitated by certain complement components, some leukotrienes, as well as products secreted by pathogenic microbes.
- Adhesion (gluing) of phagocytes-macrophages to the vascular endothelium.
- Passage of phagocytes through the wall and exit beyond it
- Opsonization. Antibodies envelop the surface of a foreign particle and are assisted by complement components. This facilitates the uptake of antigen by phagocytes. The phagocyte then attaches to the antigen.
- Actually phagocytosis. The foreign particle is absorbed by the phagocyte: first, a phagosome is formed - a specific vacuole, which then connects with the lysosome, where lysosomal enzymes that digest the antigen are located).
- Activation of metabolic processes in the phagocyte, promoting phagocytosis.
- Antigen destruction.
The process of phagocytosis can be completed or incomplete. In the first case, the antigen is phagocytosed successfully and completely, in the second - not. Some pathogenic microorganisms take advantage of the incompleteness of phagocytosis for their own purposes (gonococci, mycobacterium tuberculosis).
Find out how you can support your body's immunity.
Immunity is the most important process in our body, helping to maintain its integrity, protecting it from harmful microorganisms and foreign agents. Cellular and humoral are two mechanisms that, acting harmoniously, complement each other and help maintain health and life. These mechanisms are quite complex, but our body as a whole is a very complex self-organizing system.
The cellular immune response is formed during organ and tissue transplantation, viral infection, and malignant tumor growth. Cellular immunity involves Tc (Tc), which reacts with antigen in complex with MHC class I glycoproteins in plasma membrane target cells. A cytotoxic T cell kills a cell infected with a virus if it recognizes, using its receptors, fragments of viral proteins associated with MHC class I molecules on the surface of the infected cell. Binding of TC to targets leads to the release by cytotoxic cells of pore-forming proteins called perforins, which polymerize in the plasma membrane of the target cell, turning into transmembrane channels. These channels are believed to permeabilize the membrane, which promotes cell death.
Mechanism of humoral immunity
The humoral immune response is provided by B lymphocytes with the participation of Tx and macrophages (antigen-presenting cells).
The antigen that enters the body is absorbed by the macrophage. The macrophage breaks it down into fragments, which, in combination with MHC class II molecules, appear on the cell surface. This processing of the antigen by the macrophage is called antigen processing.
For further development The immune response to antigen requires the participation of Th. But first, Tx must be activated themselves. This activation occurs when the antigen processed by the macrophage is recognized by Tx. “Recognition” by the Tx cell of the complex “antigen + MHC class II molecule” on the surface of the macrophage (i.e., the specific interaction of the receptor of this T lymphocyte with its ligand) stimulates the secretion of interleukin-1 (IL-1) by the macrophage. Under the influence of IL-1, the synthesis and secretion of IL-2 by the Th cell is activated. The release of IL-2 by the Tx cell stimulates its proliferation. Such a process can be regarded as autocrine stimulation, since the cell responds to the agent that it itself synthesizes and secretes. An increase in Th abundance is necessary for the implementation of an optimal immune response. Tx activate B cells by secreting IL-2.
Activation of the B lymphocyte also occurs through direct interaction of the antigen with the immunoglobulin receptor of the B cell. The B lymphocyte itself processes the antigen and presents its fragment in complex with an MHC class II molecule on the cell surface. This complex recognizes Tx already involved in the immune reaction. Recognition by the Tx cell receptor of the complex “AG + MHC class II molecule” on the surface of the B lymphocyte leads to the secretion of interleukins by the Tx cell, under the influence of which the B cell multiplies and differentiates with the formation of plasma cells and memory B cells. Thus, IL-4 initiates the activation of B cells, IL-5 stimulates the proliferation of activated B cells, and IL-6 causes the maturation of activated B cells and their transformation into plasma cells that secrete antibodies. Interferon attracts and activates macrophages, which begin to more actively phagocytose and destroy invading microorganisms.
Broadcast large quantity Antigens processed by macrophages ensure the proliferation and differentiation of B-lymphocytes towards the formation of plasma cells that produce specific antibodies to a specific type of antigen.
In order to begin producing antibodies, B cells must turn into plasma cells. The process of plasmacytogenesis is accompanied by a loss of cell division and movement and a decrease in the amount of surface immunoglobulins in the cytolemma. The lifespan of plasma cells is several weeks. Lymphoblasts and immature plasma cells from the lymph nodes where they are formed are able to penetrate into the efferent lymph nodes. lymphatic vessels and populate neighboring The lymph nodes. Some of the small cells formed from them, resembling lymphocytes in appearance, penetrate into blood vessels. They have a centrally located nucleus, surrounded by a narrow rim of cytoplasm, in which a developed granular endoplasmic reticulum is visible. These cells are called lymphoplasmocytes.
T-suppressors (Ts), suppress the ability of lymphocytes to participate in the production of antibodies and thus provide immunological tolerance, i.e. insensitivity to certain antigens. They regulate the number of plasma cells formed and the amount of antibodies synthesized by these cells. It turned out that a special subpopulation of B-lymphocytes, which are called B-suppressors, can also inhibit the production of antibodies. It has been shown that T- and B-suppressors can also act suppressively on cellular immune responses.
Our health often depends on how correctly and responsibly we treat our body and lifestyle. Are we fighting bad habits, are we learning to control our psychological condition or we give free rein to our emotions. It is these types of manifestations of our life that largely determine the state of our immunity.
Immunity is the body’s ability to be immune and resist foreign substances of various origins. This complex defense system was created and changed simultaneously with the development of evolution. These changes continue today, as conditions are constantly changing. environment, and therefore the living conditions of existing organisms. Thanks to immunity, our body is capable of recognizing and destroying pathogens, foreign bodies, poisons and internal degenerated cells of the body.
The concept of immunity is defined general condition organism, which depends on the metabolic process, heredity and changes under the influence of the external environment.
Naturally, the body will be different good health if the immune system is strong. Types of human immunity, based on their origin, are divided into congenital and acquired, natural and artificial.
Types of immunity
Scheme - classification of immunity Innate immunity is a genotypic trait of an organism that is inherited. The functioning of this type of immunity is ensured by many factors at different levels: cellular and non-cellular (or humoral). In some cases, the body's natural defense function may be reduced as a result of the development of foreign microorganisms. Wherein natural immunity the body decreases. This usually occurs during stressful situations or with hypovitaminosis. If a foreign agent enters the blood during a weakened state of the body, then acquired immunity begins its work. That is different types immunity replace each other.
Acquired immunity is a phenotypic trait, resistance to foreign agents, which is formed after vaccination or exposure to the body infectious disease. Therefore, it is worth getting sick from any disease, for example, smallpox, measles or chickenpox, and then special means of protection against these diseases are formed in the body. A person cannot get sick with them again.
Natural immunity can be either congenital or acquired after an infectious disease. Also, this immunity can be created with the help of maternal antibodies, which reach the fetus during pregnancy, and then during pregnancy. breastfeeding already to the child. Artificial immunity, unlike natural immunity, is acquired by the body after vaccination or as a result of the introduction of a special substance - a therapeutic serum.
If the body has long-term resistance to a repeated case of an infectious disease, then immunity can be called permanent. When the body is immune to diseases for some time, as a result of the administration of serum, immunity is called temporary.
Provided the body produces antibodies on its own, immunity is active. If the body receives antibodies in ready-made form (through the placenta, from therapeutic serum or through breast milk), then they talk about passive immunity.
“Types of immunity” Table
Useful video
It has now been proven that the guarantee of human health and vital activity largely depends on the state of the immune system. At the same time, not everyone knows what the presented concept is, what functions it performs and what types it is divided into. Acquainted with useful information This article will help you on this topic.
What is immunity?
Immunity represents the ability of the human body to provide protective functions, preventing the proliferation of bacteria and viruses. Peculiarity immune system is to maintain a constant internal environment.
Main functions:
- Elimination of the negative impact of pathogens - chemical substances, viruses, bacteria;
- Replacement of non-functioning, spent cells.
For the formation defensive reaction the internal environment is answered by the mechanisms of the immune system. The correct implementation of protective functions determines the state of health of the individual.
Mechanisms of immunity and their classification:
Highlight specific And nonspecific mechanisms. Impact of specific mechanisms aimed at ensuring the protection of the individual against specific antigen. Nonspecific mechanisms counteract any pathogens. In addition, they are responsible for the initial defense and vitality of the body.
In addition to the listed types, the following mechanisms are distinguished:
- Humoral - the action of this mechanism is aimed at preventing antigens from entering the blood or other body fluids;
- Cellular - a complex type of protection that affects pathogenic bacteria through lymphocytes, macrophages and others immune cells(skin cells, mucous membrane). It should be noted that the activities cell type carried out without antibodies.
Main classification
Currently, the main types of immunity are distinguished:
- The existing classification divides immunity into: natural or artificial;
- Depending on the location there are: General— provides general protection of the internal environment; Local- whose activities are aimed at local defensive reactions;
- Depending on origin: congenital or acquired;
- According to the direction of action there are: infectious or non-infectious;
- The immune system is also divided into: humoral, cellular, phagocytic.
Natural
Currently, humans have different types of immunity: natural and artificial.
The natural type is an inherited susceptibility to certain foreign bacteria and cells that have negative impact on the internal environment of the human body.
The noted types of the immune system are the main ones and each of them is divided into other types.
Concerning natural look, it is classified into congenital and acquired.
Acquired species
Acquired immunity is a specific immunity of the human body. Its formation occurs during the period of individual development of a person. When released into the internal environment of the human body this type helps counteract pathogenic bodies. This ensures that the disease progresses in a mild form.
Acquired immunity is divided into the following types of immunity:
- Natural (active and passive);
- Artificial (active and passive).
Natural active - produced after past illness(antimicrobial and antitoxic).
Natural passive - produced through the introduction of ready-made immunoglobulins.
Artificial acquired- this type of immune system appears after human intervention.
- Artificial active - formed after vaccination;
- Artificial passive - manifests itself after the administration of serum.
Difference active type The immune system from a passive one consists in the independent production of antibodies to maintain the viability of the individual.
Congenital
What type of immunity is inherited? An individual's innate susceptibility to diseases is inherited. It is a genetic trait of an individual that helps counteract certain types of diseases from birth. The activity of this type of immune system is carried out at several levels - cellular and humoral.
Innate susceptibility to diseases has the ability to decrease when the body is exposed to negative factors - stress, poor nutrition, serious illness. If the genetic species is in a weakened state, the acquired human defenses come into play and support the favorable development of the individual.
What type of immunity occurs as a result of the introduction of serum into the body?
A weakened immune system contributes to the development of diseases that undermine the human internal environment. If it is necessary to prevent the progression of diseases, artificial antibodies contained in the serum are introduced into the body. After vaccination, artificial passive immunity is developed. This variety is used to treat infectious diseases and remains in the body for a short time.
As stated, antibodies and RTKs to any arbitrary antigen preexist in the body. These antibodies and RTK are present on the surface of lymphocytes, forming antigen recognition receptors there. It is extremely important that one lymphocyte can synthesize antibodies (or RTKs) of only one specificity, which do not differ from each other in the structure of the active center. This is formulated as the principle of “one lymphocyte - one antibody”.
How does an antigen, when it enters the body, cause increased synthesis of precisely those antibodies that specifically react only with them? The answer to this question was given by the theory of clone selection of the Australian researcher F.M. Burnet. According to this theory, one cell synthesizes only one type of antibodies, which are localized on its surface. The antibody repertoire is formed before and independently of encountering an antigen. The role of the antigen is only to find a cell that carries an antibody on its membrane that reacts specifically with it, and to activate this cell. The activated lymphocyte begins to divide and differentiate. As a result, 500 - 1000 genetically identical cells (clone) arise from one cell. The clone synthesizes the same type of antibodies that can specifically recognize the antigen and bind to it (Fig. 16). This is the essence of the immune response: the selection of the desired clones and their stimulation to divide.
The formation of killer lymphocytes is based on the same principle: selection of antigens of the T-lymphocyte, which carries a RTK of the required specificity on its surface, and stimulation of its division and differentiation. As a result, a clone of killer T-cells of the same type is formed. They carry large amounts of RTK on their surface. The latter interact with the antigen that is part of the foreign cell and are capable of killing these cells.
The killer cannot do anything with the soluble antigen - neither neutralize it nor remove it from the body. But the killer lymphocyte very actively kills cells containing foreign antigen. Therefore, it passes by the soluble antigen, but does not allow the antigen located on the surface of the “foreign” cell to pass through.
A detailed study of the immune response has shown that for the formation of a clone of cells producing antibodies, or a clone of T-killers, the participation of special helper lymphocytes (T-helpers) is necessary. By themselves, they are not capable of producing antibodies or killing target cells. But, recognizing a foreign antigen, they react to it by producing growth and differentiation factors. These factors are necessary for the reproduction and maturation of antibody-forming and killer lymphocytes. In this regard, it is interesting to recall the AIDS virus, which causes severe damage to the immune system. The HIV virus infects T-helper cells, making the immune system incapable of either producing antibodies or forming T-killer cells.
11. Effector mechanisms of immunity
How do antibodies or killer T cells remove foreign substances or cells from the body? In the case of killers, RTKs perform only the function of a “gunner” - they recognize the appropriate targets and attach a killer cell to them. This is how cells infected with a virus are recognized. RTK itself is not dangerous for the target cell, but the T cells that “follow it” have enormous destructive potential. In the case of antibodies, we encounter a similar situation. Antibodies themselves are harmless to cells carrying the antigen, but when they encounter antigens circulating or included in the cell wall of a microorganism, the complement system is connected to the antibodies. It dramatically enhances the effect of antibodies. Complement imparts biological activity to the resulting antigen-antibody complex: toxicity, affinity for phagocytic cells and the ability to cause inflammation.
The first component of this system (C3) recognizes the antigen-antibody complex. Recognition leads to the appearance of enzymatic activity in it towards the subsequent component. The sequential activation of all components of the complement system has a number of consequences. Firstly, a cascade intensification of the reaction occurs. In this case, incomparably more reaction products are formed than the initial reactants. Secondly, complement components (C9) are fixed on the surface of the bacterium, sharply enhancing the phagocytosis of these cells. Third, during the enzymatic breakdown of proteins of the complement system, fragments are formed that have powerful inflammatory activity. AND, finally, when the last complement component is included in the antigen-antibody complex, this complex acquires the ability to “perforate” the cell membrane and thereby kill foreign cells. Thus, the complement system is the most important link in the body’s defense reactions.
However, complement is activated by any antigen-antibody complex, harmful or harmless to the body. An inflammatory reaction to harmless antigens that regularly enter the body can lead to allergic, that is, perverted, immune reactions. An allergy develops when an antigen enters the body again. For example, with repeated injections of antitoxic serums, or with flour millers on flour proteins, or with repeated injections of pharmaceuticals (particularly some antibiotics). The fight against allergic diseases consists of suppressing either the immune response itself or neutralizing substances produced during allergies that cause inflammation.
