What is called immunity and what are its basic mechanisms. Nonspecific and specific immunity: mechanisms, differences

Our health often depends on how correctly and responsibly we treat our body and lifestyle. Are we fighting bad habits, learning to control our psychological state, or giving 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 in 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

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. At the same time, the body's natural immunity 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 speak of passive immunity.

“Types of immunity” Table

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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.

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. This article will help you get acquainted with useful information 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 - chemicals, viruses, bacteria;
• Replacement of non-functioning, spent cells.

The mechanisms of the immune system are responsible for the formation of a protective reaction of the internal environment. The correct implementation of protective functions determines the state of health of the individual.

Mechanisms of immunity and their classification:

Allocate specific And nonspecific mechanisms. Impact of specific mechanisms are aimed at ensuring the protection of the individual against a 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 is a complex type of protection that affects pathogenic bacteria through lymphocytes, macrophages and other immune cells (skin cells, mucous membranes). It should be noted that cell type activity occurs 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 a negative effect 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 to 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 an 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.

The difference between the active type of immune system and the passive one is 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.

Immunity (lat. immunitas - liberation from something) is the body’s protection from genetically foreign organisms and substances, which include microorganisms, viruses, worms, various proteins, cells, including altered ones. It is especially important that the immune system also destroys its own cells that have changed genetically. And this happens all the time. It is known that during cell division, which constantly occurs in the human body, one out of a million resulting cells is mutant, that is, genetically foreign. In the human body, due to mutations, at any given moment there should be about 10-20 million mutant cells. Their joint malfunction would quickly lead to the death of the organism. Why doesn't this happen? The answer to this question was given by Nobel Prize laureates P. Medawar and F. Vernet. P. Medawar proved that the mechanisms of immunity are surprisingly precise. They are able to distinguish a foreign cell containing only one nucleotide that differs from the genome of their own organism. F. Vernet postulated the position (called Burnet's axiom) that the central biological mechanism of immunity is the recognition of oneself and another.

The founders of immunology - the science of immunity - are Louis Pasteur, Ilya Mechnikov and Paul Ehrlich. In 1881, L. Pasteur developed the principles of creating vaccines from weakened microorganisms in order to prevent the development of infectious diseases.

I. Mechnikov created the cellular (phagocytic) theory of immunity. P. Ehrlich discovered antibodies and created the humoral theory of immunity, establishing that antibodies are transmitted to the child through breast milk, creating passive immunity. Ehrlich developed a method for making diphtheria antitoxin, which saved millions of children's lives. In 1908, I. Mechnikov and P. Ehrlich were awarded the Nobel Prize for their work on the theory of immunity. Above we wrote about the discovery of blood groups by K. Landsteiner in 1900. He was the first to prove the existence of immunological differences between individuals within the same species.

It is known that the body rejects transplanted foreign tissue. In the 40s 20th century this process has been shown to be mediated by immunological mechanisms. However, rejection does not occur immediately and depends on another phenomenon - immunological tolerance, discovered in 1953 simultaneously and independently by P. Medawar and M. Hasek. Studying, together with surgeons, methods of skin grafting in the treatment of deep burns, P. Medawar proved that the mechanism by which foreign skin is eliminated belongs to the general category of actively acquired immune reactions. Immunological tolerance (lat. tolerantia - patience) is recognition and specific tolerance (remember that immune mechanisms, recognizing foreign things, are intolerant of them).

Specific protective factors include humoral and cellular immunity. Phagocytosis and complement-mediated cell destruction are nonspecific protective factors.

Despite the fundamental difference between specific protective factors and nonspecific ones, which lies in the ability to recognize antigens and retain memory of it, functionally they are closely related. Thus, the development of an immune response is impossible without the participation of macrophages, while at the same time the activity of macrophages is regulated by lymphocytes.

The organs of hematopoiesis and the immune system are closely related to each other by their common origin, structure and function. The lymphocyte is the main structural and functional unit of the immune system. One of the most important advances in the field of immunology is the discovery of two independent populations of lymphocytes: thymus-dependent (T-lymphocytes) and thymus-independent (B-lymphocytes), which function together. The ancestors of all blood cells and the immune (lymphoid) system are considered to be pluripotent bone marrow stem cells, from which, through division and differentiation, the formed elements that enter the blood are ultimately formed: red blood cells, leukocytes, platelets. Hematopoiesis changes its localization during embryogenesis in humans.

To implement an immune response, T- and B-lymphocytes alone are not enough. According to the modern three-cell cooperation scheme, the formation of antibodies is carried out due to the joint function of the macrophage, T- and B-lymphocytes. In this case, the macrophage transfers the antigen to the B-lymphocyte, but only after exposure to the T-helper factor does the lymphocyte begin to multiply and differentiate into a plasma cell. A single B lymphocyte produces hundreds of plasma cells that produce antibodies.

In addition, lymphocytes are produced that contribute to the development of the immune response.

So, the main function of the immune system. This is the neutralization, destruction or removal of genetically foreign substances, the entry of which into the body causes the development of an immune response. Immunity is specific. The lifespan of circulating T-lymphocytes reaches 4. 6 months. In contrast, B lymphocytes recycle more slowly, but their lifespan is several weeks.

The main property of immune system cells is their ability to interact with a huge number of antigens. The current generally accepted view is that each B lymphocyte is programmed in the hematopoietic myeloid tissue of the bone marrow, and each T lymphocyte is programmed in the thymic cortex. During the programming process, receptor proteins complementary to a specific antigen appear on the plasmalemma. The binding of a given antigen to a receptor causes a cascade of reactions that lead to the proliferation of a given cell and the formation of many descendants that react only with this antigen. One of the most important properties the immune system is