This article will consider the mechanism of immunity formation, 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 is cellular, which is based on the phenomenon of phagocytosis. It is caused by the formation of special cells in organs related to the endocrine and immune systems: lymphocytes, monocytes, basophils, macrophages.
Macrophage cells: what is it?
Macrophages, together with other protective cells (monocytes), are the main structures of phagocytosis - the process of capturing and digesting foreign substances or pathogenic pathogens that threaten the normal functioning of the body. The described defense mechanism was discovered and studied by the Russian physiologist I. Mechnikov in 1883. They also established thatcellular immunity includes phagocytosis - a protective reaction that protects the cell genome from the damaging effects of foreign agents called antigens.
It is necessary to understand the question: macrophages - what are these cells? Recall their cytogenesis. These cells are derived from monocytes that have left the bloodstream and invaded the tissues. This process is called diapedesis. Its result is the formation of macrophages in the parenchyma of the liver, lungs, lymph nodes and spleen.
For example, alveolar macrophages first contact foreign substances that have entered the lung parenchyma through special receptors. These immune cells then engulf and digest antigens and pathogens, thereby protecting the respiratory organs from pathogens and their toxins, as well as destroying particles of toxic chemicals that have entered the lungs with a portion of air during inhalation. In addition, it has been proven that alveolar macrophages are similar in terms of immune activity to protective blood cells - monocytes.
Features of the structure and functions of immune cells
Phagocytic cells have a specific cytological structure, which determines the functions 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. Mitochondria are also present, synthesizing molecules of adenosine triphosphoric acid,which is the main energy substance of macrophages. There is a system of tubules and tubules - an endoplasmic reticulum with protein-synthesizing organelles - ribosomes. Mandatory presence of one or more nuclei, often irregular in shape. 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 take into account the following, using the term "macrophages", that this is not one type of immune structures, but a heterogeneous cytosystem. For example, a distinction is made between fixed and free protective cells. 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. Depository and hematopoietic 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 efficient macrophage system, which directly provides the ability to resist pathogenic and toxic agents, as well as destroy them by capture and digestion. Moreover, cellular immunity includes a system of antibodies produced by T- and B-lymphocytes that bind to the surface antigens of viruses, bacteria and intracellular parasites: rickettsiae and chlamydia.
Peripheral immune hematopoietic organs represented by tonsils, spleenand lymph nodes form a functionally unified system responsible for both hematopoiesis 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 with the production of antibodies to its re-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, which are formed in the thymus, spleen, in the plaques of the intestinal walls and lymph nodes. These include derivatives of lymphocytes - monocytes and cells - macrophages.
Positive immunological memory is, in fact, the physiological rationale for the use of vaccination as a method of preventing infectious diseases. Since memory cells quickly recognize the antigens found 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 between the hematopoietic and immune systems
All cells used by the body to protect it from pathogenic agents and toxic substances are formed in the red bone marrow, which is also a hematopoietic organ. The thymus gland, or thymus, related to the endocrine system, performs the function of the main structure of immunity. In the human body, both the red bone marrow and the thymus are essentially the mainorgans 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 (PAF), which increases the permeability of blood vessels. Thus, a large number of macrophages from the blood get to the location of the pathogen and destroy it.
Having studied macrophages - what kind of cells they are, in what organs they are produced and what functions they perform - we were convinced that, along with other types of lymphocytes (basophils, monocytes, eosinophils), they are the main cells of the immune system.
