Nonspecific immunity: definition, mechanisms, factors and features

Immunity is a complex of protective factors that ensure the body's ability to resist the negative influence of external agents. The latter, for example, include bacteria, poisons, viruses, foreign bodies. In science, there are two types of immunity: specific and nonspecific. The latter will be discussed in the article.

general characteristics

направлен против любого антигена. Nonspecific immunity is directed against any antigen. The organism, when penetrating a foreign substance, forms an adequate response. The reaction can be at the humoral or cellular level. In the first case, the answer is formed by the development of bactericidal compounds. обеспечивает захват инородных веществ и цитотоксический эффект. Nonspecific cellular immunity provides for the trapping of foreign substances and a cytotoxic effect.

Elements

) представлены в виде анатомических барьеров, секреторных молекул и прочих компонентов. Nonspecific protective factors (immunity ) are presented in the form of anatomical barriers, secretory molecules and other components. The first include epithelial mucous layers, skin, fluctuations of bronchopulmonary cilia and intestinal contraction. считается врожденным. Nonspecific type of immunity is congenital.

Mechanical structures

формируют различные барьеры для инородных агентов. Physical factors of nonspecific cellular immunity form various barriers for foreign agents. As one of the most effective barriers are the epithelial surfaces. These barriers are practically impenetrable for most agents. The first obstacle is the skin. Desquamation (peeling) of the epithelium helps to remove bacteria and other infectious bodies. Peristalsis of the intestine, movement of the cilia ensure the release of the respiratory system and gastrointestinal tract from microorganisms. Saliva and tears, washing the mouth and eyes, contribute to the prevention of infections. Protection is also provided by the mucosa of the respiratory tract and the gastrointestinal tract.

Chemical compounds

Nonspecific immunity is provided in a variety of ways. Important in this case are the chemical compounds formed when penetrating agents. So, the development of bacteria slows down under the influence of fatty acids of sweat. The phospholipase and lysozyme present in nasal discharge, tears and saliva have a destabilizing effect on the membrane of pathogenic microorganisms. The growth of bacteria slows down and at a low pH of the gastric secretion and sweat. Antimicrobial activity is possessed by low-molecular proteins (defensins) present in the gastrointestinal tract and lungs. Normal skin flora and the gastrointestinal tract can prevent the colonization of pathogenic agents by producing toxic compounds or competing with bacteria for attachment to the surface or nutrients.

Nonspecific immunity: humoral level

Certainly, anatomical obstructions very effectively prevent the colonization of surfaces by pathogenic agents. However, if they are damaged, the barriers are violated. This allows harmful compounds to enter the body. In such cases, non-specific immunity is activated at the humoral level. Its elements are present in the serum or accumulate in the area of infection localization.

Systems

When penetrating the body of pathogenic agents, defense mechanisms are activated . One of them is complement system. Its activation is accompanied by the mobilization of phagocytes, lysosomes, an increase in vascular permeability. Another mechanism is the clotting system. It is activated depending on the severity of tissue damage. Some products of the system provide a nonspecific protective response by increasing the permeability of the vessels. They act as chemoattractants - substances that, when attached to agents, provoke their movement. In addition, some products have an antimicrobial effect. For example, they include beta-lysine. This protein is produced by platelets during clotting. It lyses a lot of gram-positive bacteria. Transferrin and lactoferrin bind the iron necessary for microbes, limiting their growth. Interferons have the ability to limit the replication of viruses. Lysozyme acts destructively on the membrane of bacteria.

Cells of nonspecific immunity

Part of the reaction to infection is the mobilization of polymorphonuclear eosinophils, neutrophils, macrophages. They move to the site of bacterial localization. These cells are considered the main line of protection of nonspecific immunity. Neutrophils - polymorphonuclear leukocytes are sent to the site of infection and capture bacteria. Immunity cells can destroy them intracellularly or move them into extracellular traps. In addition, neutrophils are involved in the repair of tissues after the elimination of infection.

Macrophages

These elements also have the ability to phagocyte (capture) pathogenic elements and destroy them. Deactivation of agents is performed at the intracellular level. Macrophages have some peculiarities. For example, they have the capacity for extracellular (extracellular) self-destruction. In addition, the elements are involved in tissue remodeling.

Additionally

In addition to the above cells in the nonspecific immune system, there are natural and lymphokine-activated killers. These elements are capable of destroying tumor agents infected with the infection. Killers are not considered part of the inflammatory response. However, in nonspecific immunity they play an essential role. Also in the system there are eosinophils. The proteins of their granules are effective against a number of parasites.

Inflammation

The main goal of this reaction is the separation of pathogenic organisms and their toxins that penetrated into tissues, and then their destruction. Of particular importance in the inflammatory process are histamine, serotonin and other biologically active components. They help increase the permeability of capillaries, providing the development of edema. In the fluid present at the site of the accumulation of agents, there are neutrophils, macrophages, antibodies, complement. They provide neutralization of bacteria and their toxins. Phagocytes concentrate in the focus of inflammation. They form a kind of fence, preventing the spread of infection. Here, too, fibrinogen begins to accumulate. Turning into fibrin, it provides thrombosis of small lymphatic and blood vessels. As a result, a barrier is created to spread the infection over them. In the inflammatory focus, blood supply is impaired. Due to this, acidic products of metabolic processes begin to accumulate and the pH decreases. This adversely affects the growth and reproduction of microorganisms.