Immunity: Types And Methods Of Maintenance

The biological meaning of immunity is protection. The immune system is critical to the survival of the body. Constantly we are faced with various alien microorganisms that are not averse to "capture" us and take advantage of our resources. But a whole army of immune cells opposes this every second.

The main role of immunity is to recognize alien genetic information and eliminate its carriers, thereby maintaining the constancy of the internal environment. The organization of the immune system is complex and multilevel, and consists of interrelated elements. Immune cells need to distinguish between their structures and foreign antigens.

An antigen is a macromolecule that is genetically alien to the body; it can be proteins, polysaccharides, nucleic acids, and their complexes. In addition, the immune system must control internal processes, preventing the spread of cells with mutations, such as degenerate cells of malignant tumors. Representatives of the friendly intestinal microflora should also remain intact. And of course, your cells should not be attacked by your own immune system.

Evolutionarily, the mammalian immune system is the most complex. Because bacteria, getting into a warm body, multiply very easily. And they need protection.

There are several groups of pathogenic agents to which the immune system responds:

1. Pathogen-associated molecular patterns (PAMP). These are molecular groups characteristic of viruses, protozoa, fungi and parasites. They are not found in the host organism and are considered as markers of the danger of penetration into the body of a foreign agent with biological aggression. This is innate immunity.

2. Antigens. These are high molecular weight molecules that are able to stimulate specialized lymphoid cells, activating the immune response. Antigen recognition is an individual process and belongs to adaptive immunity.

3. stress molecules. These are special molecules that are synthesized during cellular stress and indicate the danger of endogenous origin. They are recognized by the receptors of some lymphocytes.

Types of immunity

Immunity can be divided into natural immunity and artificial immunity. Natural immunity, in turn, is divided into innate and acquired immunity.

An innate type of immunity, it is also hereditary, constitutional or genetic. This is an unchanging, hereditary innate protection. It does not depend on previous contact with pathogens and foreign substances. Innate immunity depends on non-specific mechanisms, molecular protection and the activity of phagocytic cells.

Innate immunity can be non-specific when it indicates the degree of resistance to infection in general or specific when it comes to resistance to a particular pathogen.

The innate type of immunity can be considered at the level of species, race and individual. In species immunity, all members of a species are born with resistance to an infectious agent that causes disease in another species. For example, humans are immune to most infectious agents that cause disease in domestic animals (such as rinderpest or horse pox). Similarly, animals show innate immunity to many human diseases. The mechanisms of species immunity are not clearly understood, but it is possible that this is due to physiological and biochemical differences between the tissues of different host species, which determine whether an infectious agent can multiply or not.

Within the same species, different races show differences in susceptibility to infections. This is known as racial immunity. An example of racial immunity is anthrax resistance in Algerian sheep, while sheep in general are not immune to anthrax. An interesting example of genetic resistance to Plasmodium falciparum malaria occurs in parts of Africa where sickle cell anemia is common. A hereditary red blood cell anomaly gives immunity to infection with malarial plasmodium.

Natural immunity also depends on age. The increased susceptibility of the fetus to infections is associated with the immaturity of the immune system. The fetus in the uterus is usually protected by maternal antibodies, but some pathogens (toxoplasma, rubella virus, cytomegalovirus, herpes viruses, hepatitis B virus, human immunodeficiency virus, etc.) cross the placental barrier and cause corresponding diseases. The vaginal epithelium of prepubertal girls is more susceptible to gonococcal infection. And polio and chickenpox tend to be more severe in adults. Older people are susceptible to infections due to a weakened immune system.

The first line of defense is the physical barriers of the skin and mucous membranes.

Intact skin is virtually impervious to bacteria. The low pH and fatty acids make it an uncomfortable environment for most bacteria, excluding the friendly micro-organisms that protect our skin. And the constantly flaking top layer of skin also reduces the bacterial load.

Mucous membranes are a less durable barrier. Bacteria that enter the mucous membranes are either swallowed and rendered harmless in the stomach, or “expelled” out by coughing or with fluid flow.

Strengthen the protection of skin cells and mucous membranes antibacterial substances:

1. Lysozyme. Hydrolytic enzyme found in mucous secretions and tears. Able to break down the wall of bacterial cells.

2. Hydrogen peroxide in saliva - causes the destruction of bacteria.

3. Normal acidity of gastric juice.

There are other means of non-specific type of immunity:

• Interferon. This molecule is produced by cells during a viral infection. Interferon itself does not affect the virus, but it signals neighboring cells about infection, and they do not allow the virus to spread. It also attracts the attention of cells of the immune system.
• Immunoglobulins. All types of immunoglobulins are present on the mucous membranes, but most of all immunoglobulin A. It prevents the attachment of bacterial cells, which is the first step in the spread of infection.
• complement system. This is a group of whey proteins that circulate in the blood in an inactive state. A variety of specific and non-specific immunological mechanisms can convert the inactive form of these proteins to the active form, resulting in the destruction of bacteria, cells, and viruses; stimulation of a non-specific type of immunity; triggering inflammation; the release of various regulatory molecules and the removal of associated pathogens from the body.

• Cytokines and Chemokines: Cytokines are secreted by leukocytes and other cells and are involved in innate, adaptive immunity, and inflammation. Cytokines act non-specifically against pathogens, causing a wide range of biological activity. Chemokines are subgroups of low molecular weight cytokines involved in chemotaxis (migration caused by chemicals).
• Symbiotic flora: It prevents the spread of infection in the body. Altering friendly flora can allow foreign microbes to invade, causing serious illnesses such as staphylococcal and clostridial enterocolitis after taking antibiotics.

  Our flora, if it is represented by “good” bacteria, does not allow pathogens to “capture” the body. Good flora needs to be grown and properly fed. You need to eat varied: the more varied your diet, the more diverse the flora will be! Good bacteria love complex carbohydrates (whole grains), fiber from vegetables, fruits, berries, nuts, seeds. And pathogens like simple sugars. Therefore, if your diet has a lot of simple carbohydrates, this is an occasion to think about your diet. Pathogenic bacteria and fungi use glucose (sugar) molecules as food. We feed not only ourselves, we must remember this.

It is also necessary to minimize the use of antibiotics, use them strictly as prescribed by the doctor.

Friendly bacteria protect the host through a variety of mechanisms:

1. Competition for available food and tissue receptors.

2. Production of toxic substances that act on pathogens: fatty acids and bacteriocins.

3. Stimulation of antibody production.

If the first line of defense fails, other mechanisms come into play.

If that doesn't work, and the pathogen causes tissue damage, then an inflammatory response occurs. It includes:

• blood flow to the affected area;
• the amount of intercellular fluid (edema) increases, while enzymes and toxins are diluted;
• chemotactic factors are released that attract immune cells;
• the formation of a fibrin barrier occurs, which limits inflammation;
• complement activation and adaptive immunity.

Activation of innate immunity provides a rapid response to an invasion. If for some reason it did not work, the action of adaptive immunity is activated.

Specific or adaptive immunity is able to recognize and selectively destroy foreign microorganisms or molecules (tumor antigens, transplanted antigens, etc.). This is due to humoral or cellular immunity.

Activation of adaptive immunity does not occur immediately; it is not able to quickly respond when it first “gets acquainted” with a pathogen. But after the immune system has “recognized” a foreign microorganism, the next time it encounters it, it will very quickly deploy protection. This is due to memory cells that remember pathogens and how to deal with them.

Adaptive immunity works in concert with innate immunity. Phagocytic cells, which are the main weapons of nonspecific immunity, are actively involved in the deployment of adaptive immunity. And vice versa: humoral factors that are produced by immunocompetent cells enhance the actions of phagocytes, that is, they affect nonspecific immunity.

Specific immunity can be natural or artificial.

Natural specific human immunity is a type of acquired immunity when the body encounters a pathogen in daily life. Sometimes this acquired immunity persists for life, such as with measles or chicken pox. In other cases, it is short-lived - seasonal SARS, intestinal infections.

Artificial specific immunity occurs during vaccination.

This is a type of acquired immunity, when ready-made humoral protective factors, or even immune cells, are introduced into the human body.

Naturally acquired passive immunity occurs when protective antibodies are passed from mother to fetus and then to the infant. Maternal antibodies are transmitted with breast milk, especially in colostrum. Immunity in infants often persists as long as the child is breastfed. During pregnancy, some maternal antibodies are also passed across the placenta to the fetus. If the mother is immune to diphtheria, rubella, or polio, then the newborn will be temporarily immune to these diseases.

Human adaptive immunity is built on the cooperation of various cells. This requires a concentration of cells of certain types in a certain place. This is impossible without the formation of an organ structure. There are central organs of the immune system and peripheral.

The central organs of the immune system include the bone marrow and thymus. This is where cell maturation and differentiation occurs. The bone marrow is a hematopoietic organ. It is also a place where cells that produce antibodies - plasma cells are concentrated. In general, lymphocytes are divided into 3 types:

• T-cells are responsible for cellular immunity (T-killers), there is also a subpopulation of immunoregulatory cells (T-suppressors) and helper cells (T-helpers).
• B cells are responsible for humoral immunity (antibody synthesis).
• NK cells are "natural killer" cells of the innate immune system. Carry out the destruction of foreign cells.

Peripheral lymphoid tissues consist of well-organized encapsulated organs such as the spleen and lymph nodes and various collections of lymphatic cells that are located throughout the body. Especially a lot of them on the mucous membranes. After maturation in the primary lymphoid organs (thymus and bone marrow), lymphocytes migrate through the blood and lymph flow, accumulating in the appropriate places in the lymph nodes and spleen. After an antigenic stimulus, they participate in the immune response. Lymphocytes from the spleen respond to antigens circulating in the blood. And the lymph nodes protect the body from antigens coming from the surface of the skin or internal organs. The mucosal system protects against antigens entering the body directly through the mucosal epithelial surfaces lining the intestinal tract, respiratory tract and urinary tract. The main effector mechanism is secretory immunoglobulin A (sIgA), secreted directly to the mucosa.

All lymphocytes have a unique receptor that allows them to recognize various antigens. Tens of thousands of different lymphocytes circulate in our body. Activation of human adaptive immunity requires signals from innate immunity — antigen-presenting cells. These are macrophages and dendritic cells. They “represent” a site of a foreign microorganism, and if a lymphocyte is able to recognize it, then a chain reaction occurs. Depending on the type of pathogen, cellular or humoral immunity is activated.

Cellular immunity is aimed at the physical destruction of the cell. Killer cells work, which literally "perforate" the shell of the pathogen, causing its death. Humoral immunity produces antibodies specific to the pathogen. Antibodies have different properties. They can both block the pathogen themselves (neutralization, pathogen decay, enzymatic destruction), and indirectly affect the destruction by activating a non-specific type of immunity or enhancing human cellular immunity.

After encountering a pathogen and activating a person's specific immunity, an explosive growth of the necessary clone of lymphocytes occurs. After the pathogen is removed, memory cells remain, which again divide if the pathogen enters the body again.

Is immunity hereditary?

Of course, we inherit all genetic information. And immunity is no exception. We may inherit a predisposition to certain diseases, but whether we get sick or not depends on environmental factors. Therefore, it is so important to create the most healthy environment for yourself. There are diseases of the immune system that are associated with genetic abnormalities. These diseases are called Primary Immunodeficiencies. These include Wiskott-Aldrich syndrome, Gitlin syndrome, naked lymphocyte syndrome, and others. The defeat of the immune system at the level of genetics is always very difficult to tolerate.

We also inherit our friendly flora. And here it matters how the child was born. If through the natural birth canal, then the microbiota of his intestines will be populated by mom's lactobacilli. If through a Cesarean section, then its microbiome in the first weeks will resemble the microbiome of the skin. In this case, support with probiotic preparations is necessary.

Immunity and nutrition

The skin and mucous membranes are the first barrier and an important part of the immune defense. Therefore, everything that affects the skin also affects the immune system:

• integrity of the skin and mucous membranes;
• speed of wound healing;
• permeability of mucous barriers;
• the thickness of the mucosal layer in the intestine.

Maybe it's not so obvious, but nutrition plays a very important role in immune defense. Humoral factors of human specific immunity, immunoglobulins, are glycoproteins. It is a combination of protein and carbohydrate. This means that the level of protection against pathogens depends on an adequate intake of protein from food, as well as on the presence of enzymes and protein metabolism cofactors.

The entire immune system has neuroendocrine regulation. This means that it is regulated simultaneously by the nervous system and endocrine glands. And the nutritional status affects the functioning of this system.

For example, the hormone leptin, which is produced by fat cells, regulates appetite, T-cell activity, and stimulates innate immune cells.

The bone marrow is an organ that consumes a lot of energy and nutrients because it produces billions of blood cells every day, including immune system cells. This process depends on the presence of all the necessary components that must come from food.

Consider the role of individual food components that affect human immunity.

Protein is the main building material. Many hormones are proteins, immunoglobulins also have a protein nature. Studies have shown that with insufficient intake of protein, the number of T-helpers decreases. The composition of the protein is also important. Essential amino acids must be supplied in sufficient quantities. With a shortage of any of the essential amino acids, the function of humoral immunity decreases. In inflammatory diseases, sulfur-containing (methionine and cysteine) amino acids, which are involved in the synthesis of glutathione, one of the most important antioxidants, will be especially in demand. Arginine is a conditionally essential amino acid, but its use in patients after surgery has reduced the length of stay in the hospital. Arginine is a nitrogen donor for the synthesis of nitric oxide. Nitric oxide is toxic to some pathogens, it is produced by macrophages. Therefore, arginine affects the non-specific type of immunity. Strengthening human immunity is also attributed to glutamine and taurine.

The correct ratio of saturated and unsaturated acids in the body ensures adequate immune function. So, for example, omega-3 polyunsaturated acid is part of the membranes of all immune cells. Clinical studies of the effect of omega-3 on immunity have shown that the inclusion of fish oil in the diet of preschoolers, containing mainly omega-3, helps to reduce the incidence of acute respiratory viral infections, as well as increase the concentration of immunoglobulins IgA, IgM, IgG in the blood.

This vitamin is often drunk during seasonal SARS, trying to boost immunity. However, studies have shown that vitamin C is not able to prevent infection with the virus, but its intake can reduce the time of illness due to its antioxidant activity. Enhances the production of immunoglobulins and the activity of macrophages.

With a deficiency of this vitamin, the integrity of the skin and mucous membranes is disrupted, which violates the first line of defense. Often, recurrent chalazion, a formation in the thickness of the eyelid, correlates with low serum vitamin A levels. Also, this vitamin enhances the growth of T-cells. Is an antioxidant.

Vitamin E is the collective name for several forms of tocopherols and tocotrienols. It is an antioxidant and a component of cell membranes. In the membranes of immune cells, there is a relatively greater amount of it, since these cells are at risk of damage by free radicals. Randomized Trial of Vitamin E Supplementation for 4 Months in Healthy Older Adults Demonstrates Improvement in Clinically Relevant Measures of T-Cell Function

Responsible for the formation of bone tissue, and also regulates many reactions in the immune system. Many immune cells contain enzymes that activate vitamin D. These reactions provide local activation of human immunity. Numerous epidemiological reports have associated vitamin D deficiency with an increased risk of chronic infections, in particular Mycobacterium tuberculosis, and autoimmune disorders. Recent studies have shown that active vitamin D has multiple effects on the immune system, including increased phagocytosis and T cell activation. Supplementation has been associated with a reduced risk of autoimmune disease.

Zinc deficiency is considered one of the most common nutritional deficiencies worldwide. This is due to both its low content in foods and the presence of phytic acid in food (found in wheat bran, whole grains, and many raw vegetables). Phytic acid binds zinc and interferes with its absorption. Zinc is an important cofactor in over 90 metabolic reactions. Zinc deficiency leads to a halt in the maturation of T cells. Studies have shown that inadequate zinc stores are a risk factor for pneumonia in the elderly. Replenishment of zinc reserves is able to restore normal immunity in just 2 weeks.

The impact of physical activity and healthy sleep on immunity

Regular physical activity promotes weight control, improves vascular health, and generally supports the immune system. Intensive training, on the contrary, has a short-term inhibitory effect on a person's immunity.

Subject to circadian rhythms and going to bed between 22.00-23.00, an important hormone, melatonin, is produced, which can protect us from viral infections. In parallel, the level of the stress hormone - cortisol, which in excess has a destructive effect on the mucous membranes and the body's immune system, decreases.

The immune system is very complex. All types of immunity are involved in protection: natural and acquired immunity, active, passive. Our body is like a finely tuned instrument. He knows exactly what note to play in any situation - whom to miss, and against whom to unleash a battle. Billions of cells are always ready to protect our borders and perform their main function every second - maintaining the constancy of the internal environment for our lives.