This article will examine the mechanism of the formation of immunity, that is, the body’s properties to protect its cells from foreign substances (antigens) or pathogens (bacteria and viruses). Immunity can be formed in two ways. The first is called humoral and is characterized by the production of special protective proteins - gamma globulins, and the second - cellular, which is based on the phenomenon of phagocytosis. It is caused by the formation in the organs related to the endocrine and immune system of special cells: lymphocytes, monocytes, basophils, macrophages.
Macrophage cells: what is it?
Macrophages along with other protective cells (monocytes) are the main structures of phagocytosis - the process of capture and digestion of foreign substances or pathogenic pathogens that threaten the normal functioning of the body. The described protective mechanism was discovered and studied by the Russian physiologist I. Mechnikov in 1883. He also found that phagocytosis, a protective reaction that protects the cell genome from the damaging effects of foreign agents called antigens, belongs to cellular immunity.
You should understand the question: macrophages - what kind of cells are these? Recall their cytogenesis. These cells are derivatives of monocytes that have left the bloodstream and penetrated into the tissues. This process is called diapedesis. Its result is the formation of macrophages in the parenchyma of the liver, lungs, in the lymph nodes and in the spleen.
For example, alveolar macrophages are first contacted with foreign substances that enter the pulmonary parenchyma through special receptors. Then these immune cells absorb and digest antigens and pathogenic organisms, thereby protecting the respiratory organs from pathogens and their toxins, as well as destroying particles of toxic chemicals that enter the lungs with a portion of air during inhalation. In addition, it was proved that the level of immune activity of alveolar macrophages is similar to protective blood cells - monocytes.
Features of the structure and functions of immune cells
Phagocytic cells have a specific cytological structure, which determines the function of macrophages. Their cell membrane is capable of forming pseudopodia, which serve to capture and envelop foreign particles. In the cytoplasm there are many digestive organelles - lysosomes, which ensure the lysis of toxins, viruses or bacteria. There are also mitochondria synthesizing adenosine triphosphoric acid molecules, which are the main energy substance of macrophages. There is a system of tubules and tubules - the endoplasmic reticulum with protein synthesizing organelles - ribosomes. One or more cores, often of irregular shape, are mandatory. Multinucleated macrophages are called symplasts. They are formed as a result of intracellular karyokinesis, without separation of the cytoplasm itself.
Types of macrophages
It is necessary to consider the following, using the term “macrophages”, that this is not one type of immune structures, but a heterogeneous cytosystem. For example, fixed and free protective cells are distinguished. The first group includes alveolar macrophages, phagocytes of the parenchyma and cavities of internal organs. Fixed immune cells are also present in osteoblasts and lymph nodes. The depositing and blood-forming organs - the liver, spleen and red bone marrow - also contain fixed macrophages.
What is cellular immunity?
The above types of phagocytes are combined into a highly effective macrophage system, which directly provides the ability to resist pathogenic and toxic agents, as well as destroy them by capture and digestion. Moreover, the system of antibodies produced by T- and B-lymphocytes, which bind to surface antigens of viruses, bacteria, and intracellular parasites: rickettsia and chlamydia, belongs to cellular immunity.
Peripheral immune hemopoietic organs, represented by tonsils, spleen and lymph nodes, form a functionally unified system responsible for both blood formation and immunogenesis.
The role of macrophages in the formation of immune memory
After contact of the antigen with cells capable of phagocytosis, the latter are able to “remember” the biochemical profile of the pathogen and respond by the production of antibodies to its repeated penetration into a living cell. There are two forms of immunological memory: positive and negative. Both of them are the result of the activity of lymphocytes formed in the thymus, spleen, in plaques of the intestinal walls and lymph nodes. These include derivatives of lymphocytes - monocytes and cells - macrophages.
Positive immunological memory is essentially the physiological rationale for the use of vaccination as a method of preventing infectious diseases. Since memory cells quickly recognize the antigens present in the vaccine, they immediately respond with the rapid formation of protective antibodies. The phenomenon of negative immune memory is taken into account in transplantology to reduce the level of rejection of transplanted organs and tissues.
The relationship of the hematopoietic and immune systems
All cells used by the body to protect it from pathogenic pathogens and toxic substances are formed in the red bone marrow, which is also a blood-forming organ. The thymus gland, or thymus, belonging to the endocrine system, performs the function of the basic structure of the immune system. In the human body, both red bone marrow and thymus are, in essence, the main organs of immunogenesis.
Phagocytic cells destroy pathogens, which is usually accompanied by inflammation in infected organs and tissues. They produce a special substance - platelet activating factor (FAT), which increases the permeability of blood vessels. Thus, a large number of macrophages from the blood get to the location of the pathogenic pathogen and destroy it.
After studying the macrophages - what kind of cells they are, in what organs they are produced and what functions they perform - we made sure that along with other types of lymphocytes (basophils, monocytes, eosinophils), they are the main cells of the immune system.