HUMAN MEDICAL BIOLOGY, ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 4. THE BLOOD SYSTEM

DEFENSIVE FUNCTIONS OF BLOOD

4. IMMUNITY

Immunity is a mechanism of protecting the body against living entities and substances carrying traits of foreign Genetic information. Cellular and humoral mechanisms of immunity are distinguished.

Cellular immunity mediates the destruction of microorganisms and Viruses, as well as Cells that have become foreign to the body due to Mutations (disruption of heredity transmission). Cellular immune responses are carried out by various types of lymphocytes: killer cells, helper cells, and suppressor cells.

Humoral mechanisms of immunity are mediated through immune Antibodies (globulins), Lysozyme, interferon, The Complement System, etc., present in the Blood.

Lymphocytes participate in triggering humoral immune mechanisms. In response to the Introduction of a foreign protein (antigen) into the body, lymphocyte proliferation begins in Lymphoid Organs. The antigen interacts with monocytes-macrophages. Phagocytes destroy foreign substances.

Fragments of these substances remain on the monocyte membrane in combination with specific receptors. T-lymphocytes "recognize" foreign targets. Antibodies against these Antigens are synthesized by B-lymphocytes.

Immunity to infectious diseases can be induced artificially through vaccination. In this process, a minimal dose of toxin (a poison produced by Bacteria), which acts as an antigen, is injected into the body. In response to this administration, the body produces antibodies.

For therapeutic purposes, human blood serum obtained from individuals who have recovered from certain diseases is administered. Such serum contains antibodies that combat antigens.

Immune system dysfunction can manifest as hyper-, dys-, and hypofunction, as well as altered antigen tolerance.

Hyperfunction of the immune system develops when the system is overloaded with an antigen, particularly upon the introduction of Immune Response stimulators. A special place is occupied by hyperfunction during The formation of tumors from immunocompetent tissue cells. This is accompanied by an increase in the number of cells and IMMUNOGLOBULINS of a single type, reflecting the loss of control over synthesis and proliferation processes by tumor immunocytes. Hyperfunction can also be triggered by reduced intra-immune inhibition (decreased suppressor function) as well as external factors, specifically insufficient function of the hypothalamic-pituitary-adrenal axis. These conditions create a favorable Background for The Development of allergies.

Immune system dysfunction can develop, for instance, in the case of depressed T-lymphocyte function, leading to inadequate body resistance against infections, particularly viral and fungal ones. In such cases, B-lymphocyte reactivity and excessive antibody production may be elevated.

Immunodeficiency syndromes are characterized by defects in the humoral or cellular arms of immunity.

They can be primary (congenital and acquired), as well as secondary, which develop in the course of various diseases.

In recent years, Structure/149.html">The problem of Acquired Immunodeficiency Syndrome, or AIDS, has become highly relevant.

The state of immune tolerance is characterized by the absence of a visible Immune Response to an antigen.

Immune tolerance can be physiological, pathological, or artificial (therapeutic).

Physiological immune tolerance manifests as The Immune System's unresponsiveness to the body's own Proteins. This tolerance is based on the clonal Selection mechanism or the "memorization" of the body's protein composition by immune cells. A breakdown of physiological tolerance can occur As a result of mutations in immune cells and the suppression of so-called forbidden clones of immune cells, as well as due to damage to blood-tissue barriers of organs that normally do not induce immune tolerance (Brain tissue, Thyroid Gland, internal reproductive organs, eye lens). These disorders manifest as autoimmune diseases.

An example of pathological immune tolerance is the lack of an immune response to tumors. In this case, the immune system reacts weakly to Cancer cells that are foreign in their protein composition, which is associated not only with tumor growth but also with its origin.

Artificial (therapeutic) immune tolerance is induced using factors capable of suppressing The activity of immune system organs, such as immunosuppressants or ionizing radiation. The Study of artificial immune tolerance is of great practical importance for the development of transplantology, as it makes it possible to prevent the rejection of transplanted organs and Tissues.