Immunology and Allergology >>>> Immunity is the guardian of health

Immunity is the guardian of health.

A person would not have lived a day in an aggressive environment filled with viruses, bacteria and other microorganisms harmful to his health, if a special defense system had not been created during the evolution of the human body. This system is called the immune system (abbreviated as IP). Every second we are attacked by billions of different microbes, we practically live life in their environment. Some of these microorganisms have adapted to live with us in symbiosis and now they form an integral part of our body, forming a microbiocenosis. But the remaining countless hordes are constantly testing our body for strength, trying to colonize it. And it is the immune system that repels these attacks, often unnoticed by our senses.

On the other hand, the immune system also "scans" our own body, constantly checking it for the presence of modified own cells (tumor). Also the immune system analyzes the substances entering our body and identifies them as useful or harmful. Sometimes the immune system malfunctions (it's easier to say: "misses the blow" of the aggressors) and we get sick. How does the immune system work?

The immune system is formed by a set of specialized organs, tissues and cells, which are endowed with the ability to coordinate the connections of all body systems, and preserve our specific individuality. In fact, in addition to the protective function, the immune system controls the genetic constancy of the organism in the process of life and reproduction.

What the immune system can do:

Recognizes antigens and induces (promotes) the formation of antibodies in response to antigens, and for each antigen a unique antibody is produced (one antigen - one antibody). This property of IP is called high specificity and sensitivity of the immune system.
It is capable of responding in a high-speed mode and with increased force to the re-introduction of the antigen into the body (the vaccination system is built on this ). This property of IP is called immunological memory .
The immune system (IS) is adapted to a high degree of regeneration of its cells - homeostasis of leukocytes (disorders of this IS function lead to the development of many diseases, including immunodeficient ones).
Regulates the work of other systems by means of special groups of molecules - mediator molecules (molecules - intermediaries).
The immune system can make mistakes, as it is not always picky about the source of aggression and can direct immune actions on the body itself (this is how autoimmune diseases arise).

The body's defense capabilities.

The immune system is often called immunity. And when they talk about the nature of the immune system, they use phrases: innate immunity or adaptive immunity. These are types of immunity.

Congenital immunity (innate resistance of the body, nonspecific immunity ) - is considered a basic defense and is activated when the aggressor overcomes the external barriers of the body (physical, chemical).

Physical barriers: mucous membranes and skin (sweat and sebaceous glands, ciliated mucosal epithelium)

Chemical barriers: skin and mucous secretions, body acidity (pH), enzymes (lysozyme, fibronectin), lipids, peptide antibiotics, interferons, acute phase proteins, complement elements.

Innate immunity was formed during the evolution of organisms during their transition from unicellular to multicellular existence. This is our legacy. Almost all forms of organisms are endowed with it. Innate immunity always comes into play in the first few minutes or several hours after the penetration of pathogens. It builds cellular defense by recognizing and eliminating (destroying) pathogens using various groups of cells (eosinophils, neutrophils, basophils, monocytes, mast cells and many other elements) - nonspecific phagocytosis. These cells have special receptors for antigen recognition. Such receptors of innate immunity cells do not change evolutionarily and are inherited. A feature of innate immunityis the fact that its cells do not form clones, that is, each cell of innate immunity acts individually, and not together within the cloned cell community. We'll skip the details of this cloning for now. This is the specificity of the action of innate immunity.

Adaptive immunity (acquired resistance of the organism, specific immunity) is formed in the process of human life. Since the environment is evolutionarily changeable, over time, it became increasingly difficult for the immune system to maintain the genetic constancy of a highly organized organism with the help of a limited hereditary set of genes, reflecting the attacks of more and more new microorganisms. In this regard, a protection system with new structures and properties has been formed. New cellular defense and humoral defense have been created. (antigen-recognizing T-lymphocytes and B-lymphocytes, cytotoxic and other cellular components, molecules of specific proteins - antibodies, specific phagocytosis, immunoglobulins).

Adaptive immunity, as a more complex type of immunity, has several functions:

Forms antibodies
Starts the process of specific phagocytosis (immune phagocytosis, phagocytic immunity )
Responsible for the killer functions of lymphocytes
Responsible for allergic reactions
Possesses immunological memory
Endowed with immunological tolerance

Specific immunity is observed not in everyone, but only in complex forms of life.

The immune system consists of central and peripheral organs, each of which bears its share of responsibility for the birth, differentiation and further actions of cells of the immune system.

The central organs of the immune system: bone marrow and thymus, in them lymphocytes are produced from hematopoietic stem cells as mature non-immune lymphocytes, called native (from the English word "native" - primary).

The bone marrow is the cradle of all cells of the immune system and the site of the maturation of B-lymphocytes.

The thymus (thymus gland) is responsible for the further development and ranking of T-lymphocytes, and their final functional maturation, selecting and destroying cells highly active to their own antigens.

Peripheral organs of the immune system: lymph nodes, lymphostructures of the pharyngeal ring, lymphatic ducts and spleen.

In the lymphatic system, mature non-immune lymphocytes interact with antigen-presenting cells (APCs) and subsequently turn into antigen-dependent lymphocytes (that is, they are endowed with the ability to recognize antigens). This process is called "immunogenesis". This is how lymphoid tissue associated with the skin (represented by epidermotropic T-lymphocytes, keratinocytes, Langerhans cells) and lymphoid tissue associated with the mucous membranes of the respiratory (represented by follicles, tonsils), gastrointestinal (represented by Peyer's plaques, groups of follicles located on intestines) and urinary tract.

Nonspecific (innate) and specific immunity (acquired) have cellular and humoral defense factors .