Blood, its composition and role in the life of the animal organism. Alien chemicals Neutralizes foreign substances
2.4.7. Ways to remove foreign substances from the body
Ways and methods of natural removal of foreign compounds from the body are different. According to their practical significance, they are arranged as follows: kidneys - intestines - lungs - skin.
The excretion of toxic substances through the kidneys occurs through two main mechanisms - passive diffusion and active transport.
As a result of passive filtration in the renal glomeruli, an ultrafiltrate is formed, which contains many toxic substances, including non-electrolytes, in the same concentration as in plasma. The entire nephron can be viewed as a long, semi-permeable tube through whose walls diffuse exchange between flowing blood and forming urine takes place. Simultaneously with the convective flow along the nephron, toxic substances diffuse, obeying Fick's law, through the nephron wall back into the blood (since their concentration inside the nephron is 3–4 times higher than in plasma) along the concentration gradient. The amount of a substance that leaves the body with urine depends on the intensity of reverse reabsorption. If the permeability of the nephron wall for a given substance is high, then the concentrations in the urine and in the blood are equalized at the exit. This means that the rate of excretion will be directly proportional to the rate of urination, and the amount of excreted substance will be equal to the product of the concentration of the free form of the poison in plasma and the rate of diuresis.
l=kV m.
This is the minimum value of the excreted substance.
If the wall of the renal tubule is completely impermeable to a toxic substance, then the amount of excreted substance is maximum, does not depend on the rate of diuresis and is equal to the product of the filtration volume and the concentration of the free form of the toxic substance in plasma:
l=kV f.
The actual output is closer to the minimum values than the maximum. The permeability of the wall of the renal tubule for water-soluble electrolytes is determined by the mechanisms of "non-ionic diffusion", i.e., it is proportional, firstly, to the concentration of the undissociated form; secondly, the degree of solubility of the substance in lipids. These two circumstances make it possible not only to predict the efficiency of renal excretion, but also to control, albeit to a limited extent, the process of reabsorption. In the renal tubules, non-electrolytes, which are highly soluble in fats, can penetrate in two directions by passive diffusion: from the tubules into the blood and from the blood into the tubules. The determining factor in renal excretion is the concentration index (K):
K = C in urine / C in plasma,
where C is the concentration of the toxic substance. K value<1 свидетельствует о преимущественной диффузии веществ из плазмы в мочу, при значении К>1 is the opposite.
The direction of passive tubular diffusion of ionized organic electrolytes depends on the pH of the urine: if tubular urine is more alkaline than plasma, weak organic acids easily penetrate into the urine; if the urine reaction is more acidic, weak organic bases pass into it.
In addition, active transport of strong organic acids and bases of endogenous origin (for example, uric acid, choline, histamine, etc.), as well as foreign compounds of a similar structure with the participation of the same carriers (for example, foreign compounds containing amino group). The conjugates with glucuronic, sulfuric and other acids formed during the metabolism of many toxic substances are also concentrated in the urine due to active tubular transport.
Metals are excreted predominantly by the kidneys not only in the free state, if they circulate in the form of ions, but also in the bound state, in the form of organic complexes, which undergo glomerular ultrafiltration, and then pass through the tubules by active transport.
The release of orally toxic substances begins already in the oral cavity, where many electrolytes, heavy metals, etc. are found in saliva. However, swallowing saliva usually contributes to the return of these substances to the stomach.
Many organic poisons and their metabolites formed in the liver enter the intestines with bile, some of them are excreted from the body with feces, and some are reabsorbed into the blood and excreted in the urine. An even more complicated path is possible, found, for example, in morphine, when a foreign substance enters the blood from the intestines and returns to the liver again (intrahepatic circulation of the poison).
Most of the metals retained in the liver can bind to bile acids (manganese) and be excreted in the bile through the intestines. In this case, the form in which this metal is deposited in the tissues plays an important role. For example, metals in a colloidal state remain in the liver for a long time and are excreted mainly with feces.
Thus, the following are removed through the intestines with feces: 1) substances that are not absorbed into the blood when they are taken orally; 2) isolated with bile from the liver; 3) entered the intestine through the membranes of its wall. In the latter case, the main mode of transport of poisons is their passive diffusion along the concentration gradient.
Most volatile non-electrolytes are excreted from the body mainly unchanged with exhaled air. The initial rate of release of gases and vapors through the lungs is determined by their physicochemical properties: the lower the coefficient of solubility in water, the faster their release, especially the part that is in the circulating blood. The release of their fraction deposited in adipose tissue is delayed and occurs much more slowly, especially since this amount can be very significant, since adipose tissue can make up more than 20% of the total human mass. For example, about 50% of the inhaled chloroform is excreted during the first 8–12 hours, and the rest is in the second phase of excretion, which lasts several days.
Many non-electrolytes, undergoing slow biotransformation in the body, are excreted in the form of the main decay products: water and carbon dioxide, which is released with exhaled air. The latter is formed during the metabolism of many organic compounds, including benzene, styrene, carbon tetrachloride, methyl alcohol, ethylene glycol, acetone, etc.
Through the skin, in particular with sweat, many substances leave the body - non-electrolytes, namely: ethyl alcohol, acetone, phenols, chlorinated hydrocarbons, etc. However, with rare exceptions (for example, the concentration of carbon disulfide in sweat is several times higher than in urine), the total amount of toxic substance removed in this way is small and does not play a significant role.
When breastfeeding, there is a risk of some fat-soluble toxic substances entering the baby's body with milk, especially pesticides, organic solvents and their metabolites.
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The term "immunity" (from Latin immunitas - getting rid of something) means the body's immunity to infectious and non-infectious agents. Animal and human organisms very clearly differentiate between “own” and “foreign”, which ensures protection not only from the introduction of pathogenic microorganisms, but also from foreign proteins, polysaccharides, lipopolysaccharides and other substances.
The protective factors of the body against infectious agents and other foreign substances are divided into:
- nonspecific resistance- mechanical, physico-chemical, cellular, humoral, physiological protective reactions aimed at maintaining the constancy of the internal environment and restoring disturbed functions of the macroorganism.
- innate immunity- resistance of the organism to certain pathogenic agents, which is inherited and inherent in a particular species.
- acquired immunity- specific protection against genetically alien substances (antigens), carried out by the body's immune system in the form of antibody production.
The non-specific resistance of the organism is due to such protective factors that do not need special restructuring, but neutralize foreign bodies and substances mainly due to mechanical or physico-chemical influences. These include:
Skin - being a physical barrier to the path of microorganisms, it simultaneously has a bactericidal property against pathogens of the gastrointestinal and other diseases. The bactericidal action of the skin depends on its purity. On contaminated skin, germs persist longer than on clean skin.
The mucous membranes of the eyes, nose, mouth, stomach and other organs, like skin barriers, as a result of their impermeability to various microbes and the bactericidal action of secrets, carry out antimicrobial functions. In the lacrimal fluid, sputum, saliva is a specific protein lysozyme, which causes the "lysis" (dissolution) of many microbes.
Gastric juice (it contains hydrochloric acid) has very pronounced bactericidal properties against many pathogens, especially intestinal infections.
Lymph nodes - pathogenic microbes linger and neutralize in them. In the lymph nodes, inflammation develops, which has a detrimental effect on pathogens of infectious diseases.
Phagocytic reaction (phagocytosis) - discovered by I.I. Mechnikov. He proved that some blood cells (leukocytes) are able to capture and digest microbes, freeing the body from them. Such cells are called phagocytes.
Antibodies are special specific substances of a microbial nature that can inactivate microbes and their toxins. These protective substances are found in various tissues and organs (spleen, lymph nodes, bone marrow). They are produced when pathogenic microbes, foreign protein substances, blood serum of other animals, etc. are introduced into the body. All substances capable of inducing the formation of antibodies are antigens.
Acquired immunity can be natural, resulting from an infectious disease, and artificial, which is acquired as a result of the introduction into the body of specific biological products - vaccines and sera.
Vaccines are killed or weakened infectious agents or their toxins. Acquired immunity is active, ie. resulting from the active struggle of the body with the causative agent of the disease.
The versatility of the impact of food on the human body is due not only to the presence of energy and plastic materials, but also to a huge amount of food, including minor components, as well as non-alimentary compounds. The latter may have pharmacological activity or adverse effects.
The concept of biotransformation of foreign substances includes, on the one hand, the processes of their transport, metabolism, and toxicity, and, on the other hand, the possibility of the influence of individual nutrients and their complexes on these systems, which ultimately ensures the neutralization and elimination of xenobiotics. However, some of them are highly resistant to biotransformation and are detrimental to health. In this respect, the term should also be noted. detox - the process of neutralization within the biological system of harmful substances that have entered it. At present, a sufficiently large scientific material has been accumulated on the existence of general mechanisms of toxicity and biotransformation of foreign substances, taking into account their chemical nature and the state of the body. Most studied mechanism of two-phase detoxification of xenobiotics.
At the first stage, as a response of the body, their metabolic transformations into various intermediate compounds occur. This stage is associated with the implementation of enzymatic reactions of oxidation, reduction and hydrolysis, which usually occur in vital organs and tissues: liver, kidneys, lungs, blood, etc.
Oxidation xenobiotics catalyze microsomal liver enzymes with the participation of cytochrome P-450. The enzyme has a large number of specific isoforms, which explains the variety of toxicants undergoing oxidation.
Recovery carried out with the participation of NADON-dependent flavoprotein and cytochrome P-450. An example is the reduction reaction of nitro and azo compounds to amines, ketones to secondary alcohols.
hydrolytic decomposition as a rule, esters and amides are subjected to subsequent de-esterification and deamination.
The above ways of biotransformation lead to changes in the xenobiotic molecule - polarity, solubility, etc. increase. This contributes to their removal from the body, reduction or disappearance of the toxic effect.
However, primary metabolites may be highly reactive and more toxic than the parent toxic substances. This phenomenon is called metabolic activation. Reactive metabolites reach target cells, trigger a chain of secondary catabiochemical processes underlying the mechanism of hepatotoxic, nephrotoxic, carcinogenic, mutagenic, immunogenic effects and related diseases.
Of particular importance when considering the toxicity of xenobiotics is the formation of free radical intermediate oxidation products, which, along with the production of reactive oxygen metabolites, leads to the induction of lipid peroxidation (LPO) of biological membranes and damage to living cells. In this case, an important role is given to the state of the antioxidant system of the body.
The second phase of detoxification is associated with the so-called conjugation reactions. An example is the binding reactions of active -OH; -NH 2 ; -COOH; SH-groups of xenobiotic metabolites. The enzymes of the family of glutathione transferases, glucuronyl transferases, sulfotransferases, acyl transferases, etc. take the most active part in the neutralization reactions.
On fig. 6 is a general diagram of the metabolism and mechanism of toxicity of foreign substances.
Rice. 6.
The metabolism of xenobiotics can be influenced by many factors: genetic, physiological, environmental factors, etc.
It is of theoretical and practical interest to dwell on the role of individual food components in the regulation of metabolic processes and the implementation of the toxicity of foreign substances. Such participation can be carried out at the stages of absorption in the gastrointestinal tract, hepato-intestinal circulation, blood transport, localization in tissues and cells.
Among the main mechanisms of biotransformation of xenobiotics, processes of conjugation with reduced glutathione - T-y-glutamyl-B-cysteinyl glycine (TSH) - the main thiol component of most living cells, are of great importance. TSH has the ability to reduce hydroperoxides in the glutathione peroxidase reaction and is a cofactor in formaldehyde dehydrogenase and glyoxylase. Its concentration in the cell (cell pool) is largely dependent on the content of protein and sulfur-containing amino acids (cysteine and methionine) in the diet, so the deficiency of these nutrients increases the toxicity of a wide range of hazardous chemicals.
As noted above, an important role in maintaining the structure and functions of a living cell under the influence of active oxygen metabolites and free radical oxidation products of foreign substances is assigned to the antioxidant system of the body. It consists of the following main components: superoxide dismutase (SOD), reduced glutathione, some forms of glutathione-B-transferase, vitamins E, C, p-carotene, the trace element selenium - as a cofactor of glutathione peroxidase, as well as non-alimentary food components - a wide range of phytocompounds (bioflavonoids ).
Each of these compounds has a specific action in the overall metabolic pipeline that forms the body's antioxidant defense system:
- SOD, in its two forms - cytoplasmic Cu-Zn-SOD and mitochondrial-Mn-dependent, catalyzes the dismutation reaction of 0 2 _ into hydrogen peroxide and oxygen;
- ESH (taking into account its above functions) implements its action in several directions: it maintains the sulfhydryl groups of proteins in a reduced state, serves as a proton donor for glutathione peroxidase and glutathione-B-transferase, acts as a non-specific non-enzymatic quencher of free oxygen radicals, eventually turning , to oxidative glutathione (TSSr). Its reduction is catalyzed by soluble NADPH-dependent glutathione reductase, the coenzyme of which is vitamin B2, which determines the role of the latter in one of the xenobiotic biotransformation pathways.
Vitamin E (os-tocopherol). The most significant role in the LPO regulation system belongs to vitamin E, which neutralizes free radicals of fatty acids and reduced oxygen metabolites. The protective role of tocopherol is shown under the influence of a number of environmental pollutants that induce lipid peroxidation: ozone, NO 2 , CC1 4 , Cd, Pb, etc.
Along with antioxidant activity, vitamin E has anticarcinogenic properties - it inhibits N-nitrosation of secondary and tertiary amines in the gastrointestinal tract with the formation of carcinogenic N-nitrosamines, has the ability to block the mutagenicity of xenobiotics, and affects the activity of the monooxygenase system.
Vitamin C. The antioxidant effect of ascorbic acid under conditions of exposure to toxic substances that induce lipid peroxidation manifests itself in an increase in the level of cytochrome P-450, the activity of its reductase and the rate of hydroxylation of substrates in liver microsomes.
The most important properties of vitamin C associated with the metabolism of foreign compounds are also:
- the ability to inhibit covalent binding with macromolecules of active intermediate compounds of various xenobiotics - acetomioonophen, benzene, phenol, etc.;
- block (similar to vitamin E) nitrosation of amines and the formation of carcinogenic compounds under the influence of nitrite.
Many foreign substances, such as components of tobacco smoke, oxidize ascorbic acid to dehydroascorbate, thereby reducing its content in the body. This mechanism is the basis for determining the availability of vitamin C to smokers, organized groups, including industrial workers in contact with harmful foreign substances.
For the prevention of chemical carcinogenesis, Nobel Prize winner L. Pauling recommended the use of megadoses exceeding the daily requirement by 10 or more times. The feasibility and effectiveness of such amounts remains controversial, since the saturation of the tissues of the human body under these conditions is provided by a daily intake of 200 mg of ascorbic acid.
Non-alimentary food components that form the body's antioxidant system include dietary fiber and biologically active phytocompounds.
Alimentary fiber. These include cellulose, hemicellulose, pectins and lignin, which are of vegetable origin and are not affected by digestive enzymes.
Dietary fiber can affect the biotransformation of foreign substances in the following areas:
- affecting intestinal peristalsis, accelerate the passage of contents and thereby reduce the time of contact of toxic substances with the mucous membrane;
- change the composition of the microflora and the activity of microbial enzymes involved in the metabolism of xenobiotics or their conjugates;
- possess adsorption and cation-exchange properties, which makes it possible to bind chemical agents, delay their absorption and accelerate excretion from the body. These properties also affect the hepato-intestinal circulation and ensure the metabolism of xenobiotics that enter the body in various ways.
Experimental and clinical studies have established that the inclusion of cellulose, carrageenine, guar gum, pectin, wheat bran in the diet leads to inhibition of (3-glucuronidase and mucinase of intestinal microorganisms. This effect should be considered as another ability of dietary fiber to transform foreign substances by preventing the hydrolysis of conjugates of these substances, removing them from the hepato-intestinal circulation and increasing excretion from the body with metabolic products.
There is evidence of the ability of low methoxyl pectin to bind mercury, cobalt, lead, nickel, cadmium, manganese and strontium. However, this ability of individual pectins depends on their origin and requires study and selective application. So, for example, citrus pectin does not show a visible adsorption effect, slightly activates (3-glucuronidase of the intestinal microflora, is characterized by the absence of preventive properties in induced chemical carcinogenesis.
Biologically active phytocompounds. Neutralization of toxic substances with the participation of phytocompounds is associated with their main properties:
- affect metabolic processes and neutralize foreign substances;
- have the ability to bind free radicals and reactive metabolites of xenobiotics;
- inhibit enzymes that activate foreign substances and activate detoxification enzymes.
Many of the natural phytocompounds have specific properties as inducers or inhibitors of toxic agents. Organic compounds contained in zucchini, cauliflower and Brussels sprouts, broccoli are able to induce the metabolism of foreign substances, which is confirmed by the acceleration of the metabolism of phenacetin, the acceleration of the half-life of antipyrine in the blood plasma of the subjects who received cruciferous vegetables with the diet.
Particular attention is drawn to the properties of these compounds, as well as phytocompounds of tea and coffee - catechins and diterpenes (capheol and cafestol) to stimulate the activity of the monooxygenase system and glutathione-S-transferase of the liver and intestinal mucosa. The latter underlies their antioxidant effect when exposed to carcinogens and anticancer activity.
It seems appropriate to dwell on the biological role of other vitamins in the processes of biotransformation of foreign substances that are not associated with the antioxidant system.
Many vitamins perform the functions of coenzymes directly in the enzyme systems associated with the exchange of xenobiotics, as well as in the biosynthesis enzymes of the components of biotransformation systems.
Thiamine (vitamin Bt). It is known that thiamine deficiency causes an increase in the activity and content of the components of the monooxygenase system, which is considered as an unfavorable factor contributing to the metabolic activation of foreign substances. Therefore, the provision of the diet with vitamins can play a certain role in the mechanism of detoxification of xenobiotics, including industrial poisons.
Riboflavin (vitamin B 2). The functions of riboflavin in the processes of biotransformation of foreign substances are realized mainly through the following metabolic processes:
- participation in the metabolism of microsomal flavoproteins NADPH-cytochrome P-450 reductase, NADPH-cytochrome-b 5 - reductase;
- ensuring the work of aldehyde oxidases, as well as glutathione reductase through the coenzymatic role of FAD with the generation of TSH from oxidized glutathione.
Animal experiments have shown that vitamin deficiency leads to a decrease in the activity of UDP-glucuronyltransferase in liver microsomes, based on the decrease in the rate of glucuronide conjugation of /7-nitrophenol and o-aminophenol. There is evidence of an increase in the content of cytochrome P-450 and the rate of hydroxylation of aminopyrine and aniline in microsomes with alimentary insufficiency of riboflavin in mice.
Cobalamins (vitamin B 12) and folic acid. The synergistic effect of the considered vitamins on the processes of biotransformation of xenobiotics is explained by the lipotropic effect of the complex of these nutrients, the most important element of which is the activation of glutathione-B-transferase and organic induction of the monooxygenase system.
Clinical trials have shown the development of vitamin B 12 deficiency when exposed to nitrous oxide, which is explained by the oxidation of CO 2+ in the CO e+ corrin ring of cobalamin and its inactivation. The latter causes folic acid deficiency, which is based on the lack of regeneration of its metabolically active forms under these conditions.
Coenzymatic forms of tetrahydrofolic acid, along with vitamin B 12 and Z-methionine, are involved in the oxidation of formaldehyde, so a deficiency of these vitamins can lead to an increase in the toxicity of formaldehyde, other one-carbon compounds, including methanol.
In general, it can be concluded that the nutritional factor can play an important role in the processes of biotransformation of foreign substances and the prevention of their adverse effects on the body. A lot of theoretical material and factual data have been accumulated in this direction, however, many questions remain open and require further experimental studies and clinical confirmation.
It is necessary to emphasize the need for practical ways to implement the preventive role of the nutrition factor in the processes of metabolism of foreign substances. This includes the development of evidence-based diets for selected populations where there is a risk of exposure to various food xenobiotics and their complexes in the form of dietary supplements, specialized foods and diets.
A. phagocytes
B. platelets
C. enzymes
D. hormones
E. erythrocytes
371. AIDS can lead to:
A. to the complete destruction of the body's immune system
B. to blood incoagulability
C. to a decrease in platelet count
D. to a sharp increase in the content of platelets in the blood
E. to a decrease in hemoglobin in the blood and the development of anemia
372. Preventive vaccinations protect against:
A. most infectious diseases
B. any disease
C. HIV infection and AIDS
D. chronic diseases
E. autoimmune diseases
373. During preventive vaccination, the following is introduced into the body:
A. Killed or weakened microorganisms
B. ready-made antibodies
C. white blood cells
D. antibiotics
E. hormones
374 Group 3 blood can be transfused to people with:
A. 3 and 4 blood group
B. 1 and 3 blood group
C. 2 and 4 blood group
D. 1 and 2 blood groups
E. 1 and 4 blood group
375. What substances neutralize foreign bodies and their poisons in the human and animal organisms?
A. antibodies
B. enzymes
C. antibiotics
D. hormones
376. Passive artificial immunity arises in a person if he is injected into the blood:
A. phagocytes and lymphocytes
B. weakened pathogens
C. preformed antibodies
D. enzymes
E. erythrocytes and platelets
377. Who was the first to study in 1880-1885. received vaccines against chicken cholera, anthrax and rabies:
A. L. Paster
B.I.P. Pavlov
C.I.M. Sechenov
D.A.A. Ukhtomsky
E. N.K Koltsov
378. Biological preparations for making people immune to infectious diseases?
A. Vaccines
B. Enzymes
D. Hormones
E. Serums
379. Live vaccines contain:
A. Weakened bacteria or viruses
B. Enzymes
D. Antitoxins
E. Hormones
380. Anatoxins:
A. Little reactogenic, able to form intense immunity for 4–5 years.
381. Phages:
A. They are viruses capable of penetrating a bacterial cell, reproducing and causing its lysis.
B. They are chemical vaccines.
C. Used to prevent typhoid fever, paratyphoid A and B
D. Used to prevent typhoid, paratyphoid, whooping cough, cholera
E. More immunogenic, create high tension immunity
382. Used for phage prophylaxis and phage therapy of infectious diseases:
A. Bacteriophages
B. Antitoxins
C. Live vaccines
D. Complete antigens
E. Killed vaccines
383. Measure aimed at maintaining immunity developed by previous vaccinations:
A. Revaccination
B. Vaccination of the population
C. Bacterial contamination
D. Stabilization
E. Fermentation
384. The following factors, which depend on the vaccine itself, influence the development of post-vaccination immunity:
A. All answers are correct
B. the purity of the preparation;
C. lifetime of the antigen;
E. the presence of protective antigens;
Immunity: what is it.
The ultimate goal of the immune system is the destruction of a foreign agent, which may be a pathogen, a foreign body, a poisonous substance, or a degenerated cell of the body itself. In the immune system of developed organisms, there are many ways to detect and remove foreign agents, their combination is called the immune response.
All forms of the immune response can be divided into acquired and congenital reactions.
acquired immunity is formed after the "first meeting" with a specific antigen - memory cells (T-lymphocytes) are responsible for storing information about this "meeting". Acquired immunity is highly specific with respect to a particular type of antigens and allows them to be destroyed faster and more efficiently in the event of a second encounter.antigens molecules that cause specific reactions of the body and are perceived as foreign agents are called. For example, people who have had chickenpox (measles, diphtheria) often develop lifelong immunity to these diseases.
innate immunity is characterized by the body's ability to neutralize foreign and potentially dangerous biomaterial (microorganisms, transplant, toxins, tumor cells, virus-infected cells), which exists initially, before the first entry of this biomaterial into the body.
Morphology of the immune system
The immune system of humans and other vertebrates is a complex of organs and cells capable of performing immunological functions. First of all, the immune response is carried out by leukocytes. Most of the cells of the immune system come from hematopoietic tissues. In adults, the development of these cells begins in the bone marrow. Only T-lymphocytes differentiate inside the thymus (thymus gland). Mature cells settle in the lymphoid organs and at the boundaries with the environment, near the skin or on the mucous membranes.The body of animals with acquired immunity mechanisms produces many varieties of specific immune cells, each of which is responsible for a specific antigen. The presence of a large number of varieties of immune cells is necessary in order to repel the attacks of microorganisms that can mutate and change their antigenic composition. A significant part of these cells complete their life cycle without taking part in the body's defense, for example, without meeting suitable antigens.
The immune system protects the body from infection in several stages, with each stage increasing the specificity of protection. The simplest line of defense is the physical barriers (skin, mucous membranes) that prevent infection - bacteria and viruses - from entering the body. If the pathogen penetrates these barriers, the innate immune system performs an intermediate non-specific reaction to it. The innate immune system is found in all plants and animals. In the event that pathogens successfully overcome the impact of innate immune mechanisms, vertebrates have a third level of protection - acquired immune protection. This part of the immune system adapts its response during the infectious process to improve recognition of foreign biological material. This improved response persists after eradication of the pathogen in the form of immunological memory. It allows the adaptive immunity mechanisms to develop a faster and stronger response each time the same pathogen appears.
Both innate and adaptive immunity depend on the ability of the immune system to distinguish self from non-self molecules. In immunology, self molecules are understood as those components of the body that the immune system is able to distinguish from foreign ones. In contrast, molecules that are recognized as foreign are called foreign. Recognized molecules are called antigens, which are currently defined as substances bound by specific immune receptors of the adaptive immune system.
Surface barriers
Organisms are protected from infection by a number of mechanical, chemical and biological barriers.Examples mechanical barriers The waxy coating of many plant leaves, the exoskeleton of arthropods, egg shells, and skin can serve as the first line of defense against infection. However, the body cannot be completely separated from the external environment, so there are other systems that protect the external messages of the body - the respiratory, digestive and genitourinary systems. These systems can be divided into permanent and activated in response to an invasion.
An example of a constantly operating system is the tiny hairs on the walls of the trachea, called cilia, which make rapid upward movements, removing any dust, pollen, or other small foreign objects so that they cannot enter the lungs. Similarly, the expulsion of microorganisms is carried out by the washing action of tears and urine. Mucus secreted into the respiratory and digestive systems serves to bind and immobilize microorganisms.
If the constantly operating mechanisms are not enough, then the "emergency" cleansing mechanisms of the body, such as coughing, sneezing, vomiting and diarrhea, are turned on.In addition to this, there are chemical protective barriers. Skin and airways secrete antimicrobial peptides (proteins)
Enzymes such as lysozyme and phospholipase A are found in saliva, tears, and breast milk and also have antimicrobial activity. Vaginal discharge serves as a chemical barrier after the onset of menstruation, when it becomes slightly acidic. Sperm contains defensins and zinc to kill pathogens. In the stomach, hydrochloric acid and proteolytic enzymes serve as powerful chemical protective factors against ingested microorganisms.
In the genitourinary and gastrointestinal tracts there are biological barriers, represented by friendly microorganisms - commensals. The non-pathogenic microflora that has adapted to living in these conditions competes with pathogenic bacteria for food and space, thus forcing them out of their barrier areas. This reduces the likelihood of disease-causing microbes reaching sufficient numbers to cause infection.innate immunity
If the microorganism manages to penetrate the primary barriers, it collides with the cells and mechanisms of the innate immune system. Innate immune defense is nonspecific, that is, its links recognize and react to foreign bodies, regardless of their characteristics, according to generally accepted mechanisms. This system does not create long-term immunity to a particular infection.Non-specific immune responses include inflammatory responses, the complement system, as well as non-specific killing mechanisms and phagocytosis.
These mechanisms are discussed in the "Mechanisms" section, the complement system - in the "Molecules" section.acquired immunity
The acquired immune system appeared during the evolution of lower vertebrates. It provides a more intense immune response, as well as immunological memory, due to which each foreign microorganism is "remembered" by antigens unique to it. The acquired immune system is antigen-specific and requires the recognition of specific non-self antigens in a process called antigen presentation. The specificity of the antigen allows reactions to be carried out that are intended for specific microorganisms or cells infected by them. The ability to carry out such narrowly targeted reactions is maintained in the body by "memory cells". If a macroorganism is infected by a microorganism more than once, these specific memory cells are used to rapidly kill that microorganism.Cells-effectors of a specific immune response are discussed in the "Cells" section, mechanisms for the deployment of an immune response with their participation - in the "Mechanisms" section.
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