Leukocytes perform the following function. Types of blood leukocytes and their functions
Leukocytes, their classification, properties and functions.
Leukocytes or white blood cells, unlike erythrocytes, have a nucleus and other structural elements characteristic of cells. Size from 7.5 to 20 microns.
Leukocytes are characterized by amoeboid movement. They are able to leave the bloodstream (their movement speed is 40 µm/min). The release of leukocytes through the capillary endothelium is called diapedesis. After leaving the vessel, they are sent to the site of the introduction of a foreign factor, the focus of inflammation, and the products of tissue decay ( positive chemotaxis). Negative chemotaxis- this is the direction of movement of leukocytes from the place of introduction of the pathogenic factor.
Functions of leukocytes:
· Protective(participation in ensuring nonspecific resistance and creating humoral and cellular immunity).
· metabolic(exit to the light digestive tract, capture there nutrients and transfer them to the blood. This is especially important in maintaining immunity in newborns during the period breastfeeding due to the transfer into the blood in unchanged form of immunoglobulins from mother's milk).
· Histolytic- lysis (dissolution) of damaged tissues;
· Morphogenetic- the destruction of various bookmarks during the period of embryonic development.
Functions certain types leukocytes:
1. Non-granular (agranulocytes):
a) monocytes- 2-10% of all leukocytes (macrophages). The largest blood cells. They have bactericidal activity. Appear in the lesion after neutrophils. The maximum of their activity is manifested in acidic environment. In tissues, monocytes, having reached maturity, turn into immobile cells - histiocytes (tissue macrophages).
In the focus of inflammation phagocytose:
Microorganisms.
dead leukocytes.
· Damaged tissue cells.
They thus clean the lesion. This is a kind of "wipers of the body."
b) lymphocytes- 20-40% of all leukocytes.
Unlike other forms of leukocytes, they do not return after leaving the vessel and do not live for several days, like other leukocytes, but for 20 or more years.
Lymphocytes are the central link of the body's immune system. Provide genetic constancy internal environment, recognize "their" and "foreign".
They carry out:
Synthesis of antibodies.
Lysis of foreign cells.
· Provide reaction of rejection of a transplant.
· Immune memory.
Destruction of own mutant cells.
The state of sensitization.
Distinguish:
T - lymphocytes(provide cellular immunity):
a) T - helpers.
b) T - suppressors.
c) T - killers.
d) T - amplifiers (accelerators).
e) Immunological memory.
B-lymphocytes(provide humoral immunity). There is information about the existence of populations of B-lymphocytes:
a) Plasma cells;
b) B-killers;
c) B-helpers;
d) B-suppressors;
e) Immunological memory cells.
Lymphocytes are formed from a common stem cell. Differentiation of T-lymphocytes occurs in the thymus, and B-lymphocytes - in the red bone marrow, Peyer's patches of the intestine, tonsils, lymph nodes, appendix.
Null lymphocytes(neither T- nor B-lymphocytes) They account for 10 - 20% of lymphoid cells. It is believed that they are able to transform into B- or T-lymphocytes. These include 0-lymphocytes (null), referred to as natural killers or NK-lymphocytes. They are producers of proteins capable of “drilling” pores in the membrane of foreign cells, for which they received the name perforins. Under the influence of enzymes penetrating through such pores into the cell, its destruction occurs.
Granulocytes:
a) neutrophils- the most large group leukocytes (50-70% of all leukocytes). Their granules contain substances with high bactericidal activity (lysozyme, myeloperoxidase, collagenase, cationic proteins, defensins, lactoferrin, etc.). They are carriers of receptors for IgG, complement proteins, cytokines. Approximately 1% of all neutrophils circulate in the blood. The rest are in fabrics. They are the first to appear in the focus of inflammation, phagocytize and destroy harmful agents. 1 neutrophil is able to phagocytose 20-30 bacteria. They produce interferon, IL-6, chemotaxis factors. Their action is enhanced by complement (a system of proteins that have a lytic effect and enhance phagocytosis).
b) Eosinophils- 1-5% of all leukocytes (stained with eosin). They stay in the bloodstream for several hours, after which they migrate to the tissues, where they are destroyed.
Functions of eosinophils:
Phagocytosis.
Neutralization of toxins of the proteinaceous nature.
Destruction of foreign proteins and antigen-antibody complexes.
Produce histaminase.
in) Basophils- 0-1% of all leukocytes. They produce histamine and heparin (together with mast cells they are called heparinocytes). Heparin prevents blood clotting, histamine dilates capillaries, promotes resorption and healing of wounds. They contain platelet activating factor (PAF), thromboxanes, prostaglandins, leukotrienes, eosinophil chemotaxis factor. Basophils are carriers of IgE receptors, which play an essential role in cell degranulation, histamine release and manifestation allergic reactions(hives, bronchial asthma, anaphylactic shock, etc.).
Granulocytes are able to receive energy due to anaerobic glycolysis, and therefore they can carry out their functions in tissues poor in O 2 (inflamed, edematous, poorly supplied with blood).
Lysosomal enzymes that release upon destruction of neutrophils cause softening of tissues and the formation purulent focus(abscess). Pus is dead neutrophils and their remnants.
Metamyelocytes ( young ) - 0-1% of all leukocytes. They live from several days to a week.
Myelocytes-(0%).
Leukocyte formula - the percentage of all forms of leukocytes (Table 3).
Table 3
Leukocyte formula (%)
Increase in young forms (non-segmented neutrophils) - shift to the left. It is noted in leukemia, infectious and inflammatory diseases. A decrease in the number of non-segmented forms is called a shift leukocyte formula right, which indicates the appearance in the blood of old forms of leukocytes and the weakening of leukopoiesis.
To assess the intensity of leukopoiesis, calculate regeneration index(IR).
It is calculated:
Normal IR = 0.05 - 0.1. With severe inflammatory processes it rises to 1 - 2. It is an indicator of the severity of the disease and the body's response to a pathogenic factor, as well as the effectiveness of treatment.
In addition to the leukocyte formula, the absolute content of each type of leukocyte is sometimes determined ( leukocyte profile).
The number of leukocytes is normal: 4-9 x 10 9 / l (Giga / l).
Approximately 40 - 50 years ago, the lower limit was considered to be 6 x 10 9 /l. Now this border is 4 x 10 9 /l. This is due to urbanization, with an increase in background radioactivity and wide application various medicines.
An increase in the number of white blood cells is called leukocytosis. Distinguish the following types leukocytosis:
Physiological or redistributive. Caused by the redistribution of leukocytes between the vessels various bodies. To physiological species leukocytosis include:
· Digestive. After a meal, as a result of the entry of leukocytes into the circulation from the blood depot. They are especially abundant in the submucosal layer of the intestine, where they perform a protective function.
· Myogenic. Under the influence of severe muscle work the number of leukocytes increases by 3-5 times. It can be both redistributive and true due to increased leukopoiesis.
· pregnant. Leukocytosis is predominantly local in nature (in the submucosa of the uterus). Its value is to prevent infection from entering the body of the woman in labor, as well as to stimulate the contractile function of the uterus.
· newborns(metabolic function).
· In case of pain.
· With emotional influences.
Pathological(reactive)- response (reactive) hyperplasia caused by infection, purulent, inflammatory, septic and allergic processes.
For acute infectious diseases neutrophilic leukocytosis occurs first. Then the stage of monocytosis (a sign of the victory of the organism), after which the stage of purification (lymphocytes, eosinophils). chronic infection accompanied by lymphocytosis.
Leukemia - uncontrolled malignant proliferation of leukocytes. Leukocytes in these cases are poorly differentiated and do not perform their physiological functions.
Leukopenia(the number of leukocytes is below 4 x 10 9 /l). There may be a uniform decrease in all forms or predominantly individual forms. It arises as a result various reasons:
The accumulation of leukocytes in the dilated capillaries of the lungs, liver, intestines during blood transfusion or anaphylactic shock(redistributive leukopenia).
Intensive destruction of leukocytes (with extensive purulent-inflammatory processes). The decay products of leukocytes stimulate leukopoiesis, but over time it becomes insufficient to make up for the loss of leukocytes.
Inhibition of leukopoiesis - ( acute leukemia, irradiation, autoallergy, metastases malignant formations in Bone marrow).
Non-infectious leukopenia. Under the influence of the radiation factor (at radiation sickness the number of leukocytes decreases to 0.5 x 10 9 / l), with the use of a number of medicinal substances.
Lifespan various forms leukocyte count is different (from 2-3 days to 2-3 weeks). Long-lived lymphocytes (immunological memory cells) live for decades.
The materials are published for review and are not a prescription for treatment! We recommend that you contact a hematologist at your healthcare facility!
Leukocytes are round-shaped cells 7-20 microns in size, consisting of a nucleus, homogeneous or granular protoplasm. They are called white blood cells for their lack of color. As well as granulocytes due to the presence of granules in the cytoplasm or agranulocytes due to the absence of granularity. AT calm state leukocytes penetrate the walls of blood vessels and exit the bloodstream.
Due to the colorless cytoplasm, unstable shape and amoeboid movement, leukocytes are called white cells (or amoebae), "floating" in the lymph or blood plasma. The rate of leukocytes is within 40 microns / min.
Important! An adult in the morning in the blood on an empty stomach has a leukocyte ratio of 1 mm - 6000-8000. Their number changes during the day due to a different functional state. A sharp increase in the level of leukocytes in the blood is leukocytosis, a decrease in concentration is leukopenia.
Main functions of leukocytes
The spleen, lymph nodes, red marrow in the bones are the organs where leukocytes are formed. Chemical elements irritate and cause leukocytes to leave the bloodstream, penetrate the capillary endothelium in order to quickly reach the source of irritation. These can be the remains of the vital activity of microbes, decaying cells, everything that can be called foreign bodies or complexes of antigens-antibodies. White cells apply positive chemotaxis towards stimuli, i.e. they have a motor response.
- immunity is formed: specific and nonspecific;
- nonspecific immunity is formed with the participation of the resulting antitoxic substances and interferon;
- production of specific antibodies begins.
Leukocytes with the help of their own cytoplasm surround and digest with special enzymes foreign body what is called phagocytosis.
Important! One leukocyte digests 15-20 bacteria. Leukocytes are able to secrete important protective agents, wound healing and with a phagocytic reaction, as well as antibodies with antibacterial and antitoxic properties.
In addition to the protective function of leukocytes, they also have other important functional responsibilities. Namely:
- Transport. Amoeba-like white cells adsorb protease with peptidase, diastase, lipase, deoxyribronuclease from the lysosome and carry these enzymes on themselves to problem areas.
- Synthetic. With a lack of cells active substances: heparin, histamine and others, white cells synthesize the biological substances missing for the life and activity of all systems and organs.
- Hemostatic. Leukocytes help the blood clot quickly with the leukocyte thromboplastins they secrete.
- Sanitary. White blood cells contribute to the resorption of cells in tissues that died during injuries, due to those enzymes that they carry on themselves from lysosomes.
How long is life
Leukocytes live - 2-4 days, and the processes of their destruction occur in the spleen. The short lifespan of leukocytes is explained by the ingestion of many bodies into the body, taken by the immune system as foreign. They are quickly absorbed by phagocytes. Therefore, their sizes increase. This leads to the destruction and release of the substance that causes local inflammation accompanied by edema, elevated temperature and hyperemia in the affected area.
These substances that caused inflammatory response, begin to attract active fresh leukocytes to the epicenter. They continue to destroy substances and damaged cells, grow and also die. The place where dead white cells have accumulated begins to fester. Then lysosomal enzymes are connected, and the leukocyte sanitary function is turned on.
The structure of leukocytes
Agranulocyte cells
Lymphocytes
The lymphoblast in the bone marrow produces a rounded and different sizes, with a large round nucleus lymphocytes. They belong to immunocompetent cells, therefore they mature according to a special process. They are responsible for creating immunity with a variety of immune responses. If their final maturation occurred in the thymus, then the cells are called T-lymphocytes, if in the lymph nodes or spleen - B-lymphocytes. The size of the first (their 80%) smaller size the second cells (their 20%).
Cell life span is 90 days. They are actively involved in immune reactions and protect the body, using phagocytosis at the same time. To all pathogenic viruses and pathological bacteria, cells show nonspecific resistance- the same impact.
The general functions of leukocytes are:
1. Protective. It lies in the fact that they take part in the formation of specific and nonspecific immunities. The main mechanisms underlying immunity are:
1.1. phagocytosis, i.e., the ability of white cells to capture into the cytoplasm, hydrolyze or deprive microorganisms of vital conditions. The doctrine of the phagocytic activity of leukocytes, which is of great importance for protecting the body from the introduction pathogenic microorganisms, was expressed by the outstanding Russian scientist I. I. Mechnikov;
1.2. production of specific antibodies;
1.3. the formation of antitoxic substances, including interferon, involved in the formation of nonspecific immunity.
2. Transport. It lies in the fact that leukocytes are able to adsorb on their surface some substances contained in the blood plasma, for example, amino acids, enzymes, etc., and transport them to the places of use.
3. Synthetic. It manifests itself in the fact that some white cells synthesize biologically active substances necessary for life (heparin, histamine, etc.).
4. Hemostatic. Leukocytes take part in blood coagulation by secreting leukocyte thromboplastins.
5. Sanitary. Leukocytes take part in the resorption of dead tissues during various injuries due to the fact that they contain a large number of various enzymes, capable of hydrolyzing many substances (proteases, nucleases, glycosidases, lipases, phosphorylases localized in lysosomes). The ability of lysosomal enzymes to hydrolyze all classes of macromolecules was the basis for the conclusion that these organelles are the site of intracellular digestion.
Types of leukocytes
Depending on the structure (the presence of granularity in the cytoplasm), leukocytes are divided into two groups: granular (granulocytes) and non-granular (agranulocytes).
To grainy There are three groups of leukocytes:
1. Neutrophilic leukocytes or neutrophils. The granularity of the cytoplasm of the leukocytes of this group is stained not with basic, but with acidic colors. The grain is very soft and fine. These are round cells with a diameter of 10-12 microns. By age, three groups of leukocytes are distinguished: young, stab and segmented, having 3-5 segments. Neutrophilic leukocytes perform the following functions:
1.1. Protective, which consists in the fact that neutrophils are microphages capable of capturing microorganisms. In addition, neutrophils produce substances such as interferon (a protein is produced when microbes enter the body, including viruses that have a detrimental effect on them), antitoxic factors, substances that enhance phagocytic activity, etc. The fate of microorganisms that enter neutrophils depends on bactericidal systems that can be of two types: a) enzymatic - these include lysozyme, including the enzyme lysozyme, which can have a detrimental effect on microorganisms; lactoferrin - capable of splitting iron from the enzymes of microorganisms and depriving them of the possibility of living conditions; peroxidase, capable of causing oxidation, as a result of which the microorganism dies; b) a non-enzymatic bactericidal system, represented by cationic proteins, which are able to increase the permeability of the membranes of microorganisms, being adsorbed on its surface, as a result of which their contents are poured into environment and they die. However, it must be remembered that not all microorganisms are susceptible to the action of bactericidal systems (for example, pathogens of tuberculosis, anthrax).
1.2. Neutrophils also have a transport function, which consists in the fact that neutrophils are able to adsorb certain substances contained in the blood plasma on their surface and transport them to the places of use (amino acids, enzymes, etc.).
2. Basophilic leukocytes or basophils. The polymorphic granularity of their cytoplasm is stained with basic colors in Blue colour. The sizes of basophils range from 8 to 10 microns. The basophil nucleus is bean-shaped. Basophils perform the following functions:
2.1. Protective. They are phagocytes and produce some antitoxic substances.
2.2. Transport. Numerous specific receptors are located on their surface, binding certain proteins, as a result of which immune complexes are formed there.
2.3. Synthetic, associated with the production of active substances: histamine, heparin, etc.
3. Eosinophilic leukocytes or eosinophils having a large monomorphic granularity in the cytoplasm, capable of staining red with acid dyes (mulberry). These are rounded cells, 10-12 microns in diameter, the nucleus, as a rule, consists of two segments. Eosinophils have the following functions:
3.1. Protective: production of antitoxic substances and phagocytic ability.
3.2. Synthetic - the production of biologically active substances (histaminases, etc.).
3.3. Transport.
The lifespan of granular leukocytes is from 5 to 12 days; they are formed in the red bone marrow. The process of their formation is called granulopoiesis, which takes place in the cells of the red bone marrow and begins with the mother (stem) cell. This is followed by a precursor cell followed by a leukopoietin-sensitive cell, which is acted upon by a specific hormone, the inducer-leukopoetin, and directs the development of the cell along the white row (leukocyte). next cell is a myeloblast, then a promyelocyte, then a myelocyte, a young form of leukocytes (metamyelocyte), stab and segmented leukocytes.
Non-granular leukocytes (agranulocytes). These include lymphocytes and monocytes.
Monocytes- round large cells, the diameter of which reaches 20 microns, with a large loose bean-shaped nucleus. The life span of monocytes is from several hours to 2 days. Monocytes perform protective and transport functions. Protective function manifested in the fact that monocytes are capable of phagocytosis (macrophages) and the production of antibodies.
Spending many hours in the intercellular space, monocytes increase in size and become macrophages, which acquire the ability to move faster and increase phagocytic activity (capture 100 or more microorganisms). It has been shown that if neutrophils play a primary role in the resistance acute infections, then monocytes acquire great importance in chronic infectious diseases. In addition to the production of antibodies, monocytes are also involved in the synthesis of nonspecific immunity substances such as interferon, lysozyme, etc. Monocytes are formed in red bone marrow cells from a stem cell (monopoiesis), which proceeds as follows: stem cell, a leukopoietin-sensitive cell that is affected by a hormone-inducer, a monoblast, a promonocyte, a monocyte.
Lymphocytes. They have a rounded shape, a diameter of 8-10 microns, but can be large. Lymphocytes have a compact rounded nucleus, there is practically no cytoplasm, so there is no phagocytic activity. The main function of lymphocytes is protective. These are immunocompetent cells that take part in the formation of specific immunity, which are often called "soldiers" of the immunological front. There are 3 types of lymphocytes: T-lymphocytes (60%), B-lymphocytes (30%), O-lymphocytes (10%). The existence of two protective systems of lymphocytes, which carry different immunological functions depending on the nature of membrane receptors, has been established. The B-lymphocyte system is represented by B-lymphocytes, which are formed in the bursa in animals, and in the red bone marrow in humans. These cells leave the bone marrow and colonize the peripheral lymphoid tissue (Peyer's patches of the intestine, tonsils), undergoing further differentiation. The B-lymphocyte system specializes in the production of antibodies and forms the humoral immunity of the blood. Antibodies or immunoglobulins are proteins synthesized in the body in response to foreign substances- antigens, which can be proteins, polysaccharides and nucleic acids. Antibodies show specificity for a specific part of the antigen molecule, which is called antigen-determinant.
A human produces several tons of white blood cells. It is difficult to imagine how exactly the experts were able to calculate this, but it is quite easy to believe in the veracity of such a statement. The level of leukocytes throughout life is maintained at a more or less constant level, however, this apparent stability is maintained due to the simultaneous occurrence of two very intensive processes: the formation of white blood cells and their death.
What kind of tasks are facing leukocytes, if they “wear out” so quickly?
The main functions of leukocytes:
1. Leukocytes are the basis of immunity, they form all organs of the immune system, they are found in all tissues and in the blood. Wherever they are, tissues have the ability to defend themselves against infections, their own diseased cells, and other threats. In addition, many white blood cells can move to places where the "enemy" has entered the body. They also multiply intensively when conditions are created when their functions are most in demand. It is worth starting some kind of disease - and the corresponding leukocytes in the blood increase.
2. Some varieties of leukocytes have the ability to phagocytosis (monocytes, macrophages, neutrophils). This is a special ancient defense mechanism, during which the cells attack the offender who has entered the body, capture him, absorb and "digest". They work on the principle “whoever comes to us with a sword will die from it”: they themselves realize the goals that microbes and other aggressors set regarding healthy cells.
3. Other leukocytes, namely lymphocytes, also destroy microorganisms, as well as damaged, diseased, old cells of their own body, but they do it differently and are not phagocytes. So-called T-cells "kill by touch". They come into contact with the object, and at the place of this contact a hole is formed in the cytoplasm of the attacked cell, due to which it dies. B-lymphocytes act differently. They secrete antibodies: soluble substances that also have a detrimental effect on "outsiders".
4. Leukocytes have a memory function. They remember all the harmful objects that have affected the human body throughout his life. Accordingly, the older we are, the richer the memory of our immunity. Some "knowledge" of leukocytes is also inherited, because immune protection can be transmitted with the help of special substances (information molecules) from mother to child.
Due to the presence of memory in the immune system, leukocytes can quickly respond to some of the "offenders" they know, that is, to those whose memory the immunity has retained from the last meeting.
5. Some of the white blood cells, such as basophils and eosinophils, are involved in the body's defense against allergens.
6. Leukocytes control, direct, increase or decrease each other's activity. This contributes to the normal course of immune defense processes.
7. White blood cells have the ability to self-repair. This is very useful when harmful factors that disrupt their formation act on the body. For example, in oncological diseases, after chemotherapy, leukocytes decrease, as it suppresses the bone marrow. However, over time with successful treatment tumors, their quantity and properties are restored again, and they again begin to fully perform their other functions.
For harm, not for good
Unfortunately, sometimes the natural alertness of leukocytes towards harmful particles does not play into our hands at all. For example, white blood cells in a woman can harm the baby if the woman is pregnant.
The fact is that in fact the fetus is a foreign object for the body future mother, because it contains not only her genes, but also the genes of the father of the child. For this reason, white blood cells tend to attack the embryo, destroy it, expel it from the mother's body.
In some cases, with violations of the health of a woman, this can really happen. But this does not happen in healthy people. If this mechanism were realized, it is unlikely that humanity would still exist. Fortunately, along with the “intention” of white blood cells to destroy the fetus, a restructuring of the immune system occurs, which leads to a decrease in the activity of white blood cells. The level of leukocytes (according to at least, some of their species) decreases, and the degree of their aggression drops noticeably, which allows the pregnancy to end on time with the birth of a live and healthy child.
Another case when the functions of leukocytes are harmful instead of beneficial, transplant surgeons will remember. When transplanting organs from other people, and even when transplanting one's own tissues from one place to another, such a phenomenon as a rejection reaction is possible.
Leukocytes (mainly lymphocytes) recognize transplanted tissues as foreign, regard the operation as a powerful attack of harmful antigens, and start the process of inflammation and destruction of "foreign" tissues. As a result, the organ does not take root, the body begins to reject it, and it may be necessary to urgently remove it in order to save a person's life.
All patients who have survived transplantation are given special drugs that reduce the formation and activity of immunity - immunosuppressants. With this kind of chemotherapy, leukocytes are in a “half-asleep” state and do not react so strongly to the “threat” in the form of a new organ. This gives a chance for new tissues to become a full-fledged part of the body.
The functions of leukocytes are extremely complex; different cells perform certain tasks, each type of these cells has many varieties, each of these varieties carries out its own goals. Regulation of the activity of the multi-stage system of white blood cells is a very difficult mission for the body, so failures often occur in the immune system. Their results are an increased incidence of infections, autoimmune, allergic processes, even oncological diseases.
To strengthen the immune system, avoid health troubles and help it recover from problems that have already arisen, it is recommended to use immunomodulators. The Transfer Factor drug has a positive effect on the state of phagocyte cells, lymphocytic link, monocytes and macrophages. In addition, being a source of informational molecules, the agent contributes to the enrichment of immune memory. The Transfer Factor technique lays the foundation for a harmonious and correct operation immunity, and therefore, for the impeccable implementation of their complex functions by leukocytes.