The discovery of the first cell of the immune system (1887) - the phagocyte (macrophage) - belongs to I.I. Mechnikov. Phagocytosis (the process of absorption by some cells of others) has already been known since 1862. However, Mechnikov first established a connection between this process and the protective function that the immune system has. According to many researchers, it was from this moment that a new branch of medicine began to exist - immunology.
The immune system of the human body is a combination of anatomical structures. Its functions include providing protection against the penetration of various infectious agents, products from their vital functions, substances and tissues endowed with foreign antigenic properties.
The immune system is able to recognize a huge number of pathogens - from microbes to worms, distinguishing them from the biological molecules of their own cells. In many cases, the definition of an infectious agent is very difficult due to its ability to adapt, developing new methods of penetration and infection.
Antigens are molecules that provoke specific reactions. Not necessarily the pathogen enters the body from the outside. For example, in autoimmune pathologies, the body's own cells act as antigens.
The ultimate goal of the protective structure is to destroy the harmful pathogen. The immune system is endowed with various methods and tools for detecting and eliminating foreign agents. This whole process is called the “answer.” The immune response may be acquired or innate.
The acquired reaction differs from the existing congenital reaction by high specificity with respect to a certain type of foreign agent. This allows for repeated penetration of the pathogen to identify and eliminate it as soon as possible.
In some cases, a person develops a lifelong protection against the penetration of certain antigens, for example, after chickenpox, diphtheria, measles.
From an anatomical point of view, the immune system looks somewhat fragmented. Despite some dispersal throughout the body, all its structures are closely interconnected through the lymphatic and blood vessels. The organs of the protective structure are divided into central and peripheral. There are also immunocompetent cells.
The thymus gland (thymus), the lymphoid formations in the colon and the appendix, the embryonic liver, and bone marrow are referred to the central lymphoid organs of the protective structure .
Immunocompetent cells are polynuclear leukocytes, monocytes, lymphocytes, Langerhans cells (white process skin epidermocytes) and others.
Peripheral lymphoid defense organs include the spleen, lymph nodes.
The total mass of all cells and organs that the immune system includes in an adult is about one kilogram.
In peripheral structures, differentiation occurs (the appearance of differences between homogeneous cells) and the multiplication of antigens. In the central organs and structures, meanwhile, immunocompetent cells mature. The latter (for the most part) are constantly circulating. So, part of the immunocompetent cells moves from the vascular bed to the side of any part of the protective structure and vice versa. All components of the protective structure are interconnected. Cells interact with each other constantly, directly contacting or releasing cytokines and immunoglobulins (antibodies) into the environment. The cytokines that are formed by monocytes and macrophages are called monokines, and those formed by lymphocytes are called lymphokines.
Thus, the interconnection of all structures of the immune system and the antibodies secreted by its cells forms a complex internal defense mechanism.