Leukocyte decussation in children. Leukocyte formula of blood. What is a leukocyte formula and what indicators are studied in it

Cross of the leukocyte formula, cross of the blood formula ... This definition can often be heard when it comes to blood tests in children. What can "cross" in the results of the study, how do laboratory assistants determine this, and what does it all mean?

What is the leukocyte formula:

As everyone knows, blood contains three types of blood cells: red (erythrocytes), white (leukocytes) and platelets. When a person is given a blood test, the laboratory assistant writes in the results the absolute number of each of these groups of cells. For example, erythrocytes on average 4-5 × 1012 per 1 liter of blood, leukocytes 3-9 × 109 per the same volume.

Among leukocytes there are several forms. Rather, there are several dozen of them, since each form includes a number of varieties of cells of an intermediate degree of maturity. However, there are not so many main types of leukocytes. These are neutrophils, lymphocytes, monocytes, eosinophils, basophils.

Neutrophil (purple, right) and
lymphocyte (purple, left) -
main participants of the cross

Instead of counting the exact number of cells of one form or another, researchers write their content as a percentage. For example, neutrophils can be 45-70%, lymphocytes - 20-40%, monocytes 6-8%, basophils 0-1%, eosinophils 1-3% of all leukocytes. The total is 100%.

The number of leukocytes and their varieties - this is the leukocyte formula. In an adult, it is relatively stable and changes only in diseases, when the content of different cells changes. However, in young children, rather large changes occur in it, which are called the crossover of the formula. The cross is observed in the norm and is not a sign of pathology.

Segmented neutrophils, lymphocytes: how do they change during decussation?

The cross of the formula occurs due to the fact that in a small child, the formation, maturation of immunity takes place. Different forms of cells are formed in greater or lesser quantities, all this changes over time ... This is where regular changes in blood tests come from.

Now about why this phenomenon is called a crossover. The thing is that with it, the indicators of neutrophils and lymphocytes “cross” with each other. First, neutrophils (segmented) are lowered, neutrophils are increased. Then everything changes: segmented neutrophils are increased, lymphocytes are lowered. In more detail, it goes like this...

A newly born child has “normal” lymphocytes and neutrophils, there is no increase or decrease, and the indicators of these cells resemble those in adults: the first 30-35%, the second 60-65%.

However, already by the age of a week, changes occur: the indicators “approach” each other. As a result, it turns out that the segmented nuclei are lowered, and the lymphocytes are increased relative to the values that the little man had just recently. Both parameters "meet" at a value of 45% - by the age of the child 4-7 days in the blood they become equal.

Further, each of them continues to change in the same direction, but with a different "speed". By 10-14 days, a person has rather low segmented neutrophils, while lymphocytes increase and reach a content of 55-60%. In addition, at the same time, the level of monocytes in the blood increases slightly, up to 10%.

The following months and years do not bring as dramatic changes in the composition of the blood as the first days of life. However, segmented neutrophils gradually increase, and lymphocytes decrease again. In 5-6 years, their number is again compared. This is the second and last crossing of the leukocyte formula. Further, some more changes occur, and everything develops in such a way that, as a result, neutrophils are increased, and lymphocytes are lowered relative to those “average” 45%.

Approximately by the age of 10, the leukocyte formula ceases to change, and all values approach the norms that were described at the beginning of the article.

The biological role of the cross:

It is quite boring for a person who does not plan to connect his life with medicine to figure out which indicator and when is increased and which is lowered. If this is of interest to you, you can study and memorize the contents of the previous section in detail. However, if we are talking about your child's blood tests, and you just want to know if everything is in order with them, it is better to entrust their interpretation to a knowledgeable specialist who has been dealing with this for a long time. You just need to understand a few simple things.

The cross of the formula is a normal, physiological phenomenon. The immunity of a child who has recently been born is experiencing a big shake-up, as a large number of irritants immediately begin to act on him. Gradually, all these processes "settle down", and the immune system comes to a stable state.

The main thing that is needed while the child is growing is, if possible,
to ensure that he grows up without stress: chronic and acute diseases, abrupt climate change, long journeys, etc. In addition, immunity support would be very useful, with which childhood will pass without prolonged colds and frequent morbidity.

Reception drug Transfer Factor, created on the basis of information molecules, can help with this. These molecules train lymphocytes to work properly, which allows the child's immune system to mature faster and become highly resistant to all possible diseases, creating a guarantee of good health for the future.

In a newborn, the percentage of lymphocytes, gradually increasing, reaches 50-60 by the 5th day, and the percentage of neutrophils by the same time gradually decreases to 35-47.

The number of neutrophils and lymphocytes in different periods of childhood (in percent): a - first decussation; b - the second cross.

If you depict the changes in the number of neutrophils and lymphocytes in the form of curves (Fig.), then approximately between the 3rd-5th day there is an intersection of the curves - the so-called first crossover. By the end of the first month of life, the child's leukocyte formula is established, which is characteristic of the entire first year of life. The leukocyte formula of infants differs in some lability; it is relatively easily disturbed by strong crying and restlessness of the child, sudden changes in diet, cooling and overheating, and especially in various diseases.

In the future, at the 3-6th year of life, the number of lymphocytes significantly decreases and the number of neutrophils increases. Corresponding curves of neutrophils and lymphocytes cross again - the second cross. At the age of 14-15 years, the leukocyte formula of children almost completely approaches the leukocyte formula of adults.

The leukocyte formula in children naturally changes with age. The relative number of neutrophils at birth ranges from 51 to 72%, increases during the first hours of life, then decreases rather quickly (Table 2). The number of lymphocytes at birth ranges from 16 to 34%, reaching an average of 55% by the end of the second week of life. At the age of about 5-6 days, the curves of neutrophils and lymphocytes intersect - this is the so-called first crossing (Fig. 2), which occurs during the first week of life from 2-3 to 6-7 days. Basophilic leukocytes in newborns are often completely absent. The number of monocytes at birth ranges from 6.5 to 11%, and at the end of the neonatal period - from 8.5 to 14%. The number of plasma cells does not exceed 0.26-0.5%. In children of the first days of life, a distinct shift of neutrophils to the left according to Schilling is noted, almost leveling off by the end of the first week of life. In newborns and throughout the first year of life, an unequal size of lymphocytes is noted: the main mass is made up of medium lymphocytes, small ones are somewhat smaller and there are always 2-5% of large lymphocytes.

Table 2. Leukocyte formula of a newborn (according to A.F. Tur, in%)

Rice. 2. The first and second crosses of curves of neutrophils and lymphocytes (according to A.F. Tour). Roman numerals indicate options for crossings: 1 - according to Lippman; II - according to Zebordi; III - according to Karstanien; IV - according to N.P. Gundobin; V - according to Rabinovich.

By the end of the first month of life, the child's leukocyte formula is established, which is characteristic of the first year of life (Table 3). It is dominated by lymphocytes; there is always a moderate shift of neutrophils to the left, moderate monocytosis and an almost constant presence of plasma cells in the peripheral blood. The percentages between the individual forms of white blood cells in infants can vary over a very wide range.

Leukocyte formula of children aged from 1 month to 15 years (according to A. F. Tur, in%)

The leukocyte formula of infants differs in some lability; it is relatively easily disturbed by strong crying and restlessness of the child, sudden changes in diet, cooling and overheating, and especially in various diseases.

Sometimes by the end of the first year of life, but more often in the second year there is a certain tendency towards a relative and absolute decrease in the number of lymphocytes and an increase in the number of neutrophils; in the next years of life, this change in the ratio between lymphocytes and neutrophils comes to light more sharply, and, according to A.F. Tur, at the age of 5-7 years, their number becomes the same (“second cross” of the curve of neutrophils and lymphocytes).

During school years, the number of neutrophils continues to increase, while the number of lymphocytes decreases, the number of monocytes decreases slightly, and plasma cells almost completely disappear. At the age of 14-15 years, the leukocyte count in children is almost completely similar to that in adults (Table 3).

The correct assessment of the leukocyte formula in diseases is of great importance and is possible when taking into account its features, due to the age of the child.

LEUKOCYTE CROSS

(RULE OF FOUR FOURS)

65% lymphocytic blood profile

4 days 1 year 4 years of age

Figure 12. Leukocyte decussation.

In a newborn, the percentage of neutrophils and lymphocytes is the same as in an adult. Subsequently, the content of neutrophils falls, and lymphocytes - increases, so that on the 3rd-4th day their number is equalized (44%). This phenomenon has been named the first physiological (leukocytic) decussation. In the future, the number of neutrophils continues to decrease and reaches 25% by the age of 1-2 years. At the same age, the number of lymphocytes is 65%, that is, at this age, a lymphocytic blood profile is observed. Over the following years, the number of neutrophils gradually increases, and the number of lymphocytes decreases, so that in 4-year-old children these figures equalize again (44%) - second physiological (leukocytic) decussation. The number of neutrophils continues to increase, and lymphocytes - to decrease, and by the age of 14 these figures correspond to those in an adult, that is, a neutrophilic blood profile is observed.

Lymph(from Greek lympha - pure moisture, spring water) - a biological fluid formed from interstitial (tissue) fluid passing through the system of lymphatic vessels through a chain of lymph nodes (in which it is cleansed and enriched with formed elements) and through the thoracic duct into the blood.

Mechanism of lymph formation associated with the filtration of plasma from the blood capillaries into the interstitial space, resulting in the formation of interstitial (tissue) fluid. In a young man weighing 70 kg, the interstitial space contains about 10.5 liters of fluid. This fluid is partly reabsorbed into the blood, partly enters the lymphatic capillaries, forming lymph. The formation of lymph is promoted by increased hydrostatic pressure in the interstitial space and differences in oncotic pressure between blood vessels and interstitial fluid (providing a daily flow of proteins from the blood into the tissue fluid). These proteins are completely returned to the blood through the lymphatic system.

Lymph volume in the human body is, on average, 1-2 liters.

· peripheral lymph(flowing from tissues);

· intermediate lymph(passed through the lymph nodes);

· central lymph(located in the thoracic duct).

1. Homeostatic - maintaining the constancy of the cell microenvironment by regulating the volume and composition of the interstitial fluid.

2. Metabolic - participation in the regulation of metabolism through the transport of metabolites, proteins, enzymes, water, minerals, molecules of biologically active substances.

3. Trophic - transport of nutrients (mainly lipids) from the digestive tract into the blood.

4. Protective - participation in immune reactions (transport of antigens, antibodies, lymphocytes, macrophages and APCs).

Lymph consists of a liquid part ( plasma) And shaped elements. The closer the lymphatic vessel to the thoracic duct, the higher the content of formed elements in its lymph. However, even in the central lymph, shaped elements make up less than 1% of its volume.

Lymph plasma in terms of concentration and composition of salts, it is close to blood plasma, has an alkaline reaction (pH 8.4-9.2), contains less proteins and differs from blood plasma in their composition.

Formed elements of lymph.

The concentration of formed elements varies within 2-20 thousand/µl (2-20´10 9 /l), changing significantly during the day or as a result of various influences.

The cellular composition of the lymph: 90% lymphocytes, 5% monocytes, 2% eosinophils, 1% segmented neutrophils, and 2% other cells. Normally, erythrocytes are absent in the lymph, getting into it only with an increase in the permeability of the blood vessels of the microvasculature. Due to the presence of platelets, fibrinogen, and other clotting factors, lymph is able to clot, forming a clot.

1. Almazov V.A. Physiology of leukocytes. - L., Nauka, 1979.

2. Bykov V.L. Cytology and general histology (functional morphology of human cells and tissues). - St. Petersburg: SOTIS, 1998.

3. Vashkinel V.K., Petrov M.N. Ultrastructure and functions of human platelets. - L., Nauka, 1982.

4. Volkova O.V., Yeletsky Yu.K. and others. Histology, Cytology and Embryology: Atlas: Textbook. – M.: Medicine, 1996.

5. Histology (introduction to pathology) / Ed. E.G.Ulumbekova, Yu.A.Chelysheva. – M.: GEOTAR, 1997.

7. Protsenko V.A., Shpak S.I., Dotsenko S.M. Tissue basophils and basophilic blood granulocytes. - M., Medicine, 1987.

8. Reusch A. Fundamentals of immunology. Per. from English. - M., Mir, 1991.

9. Sapin M.R., Etingen L.E. The human immune system. - M., Medicine, 1996.

10. Semchenko V.V., Samusev R.P., Moiseev M.V., Kolosova Z.L. International histological nomenclature. - Omsk: OGMA, 1999.

11. Willoughby M. Pediatric hematology. Per. from English. - M., Medicine, 1981.

V. AGE CHARACTERISTICS OF BLOOD ……….………………23 – 24

Features of the leukocyte formula in childhood

The leukocyte formula is an indicator of the state of peripheral blood, reflecting the percentage of leukocyte cells of various types. Normally, the ratio of cells of the lecopoietic series has characteristic features depending on the age of the child.

The situation with the formula in healthy children

In healthy newborns, there is a shift in the leukocyte formula with a shift index of 0.2 (at a rate of 0.06 in adults). At the birth of a child in the formula, 60-65% of the leukogram is represented by neutrophils and 30-35% by lymphocytes. By the end of the first week of life, the number of these cells is equalized

45% each and the “first crossover” of the leukocyte formula occurs, and physiological lymphocytosis is formed in the blood of the newborn by the day. The content of lymphocytes in the leukocyte formula is 55-60%. In addition, an increase in the number of monocytes up to 10% is characteristic. The second crossover in the leukocyte formula occurs at the age of 5-6, after which, by the age of 10, the blood leukogram acquires the features of an adult:

stab neutrophils - 1-6%,
segmented neutrophils 47-72%
lymphocytes 19-37%,
monocytes 6-8%,
eosinophils 0.5-5%,
basophils 0-1%.

A sharp increase in the number of lymphocytes in the blood in the first week after birth and their predominance in the "white" blood formula up to 5-6 years of age is a physiological compensatory mechanism associated with a pronounced stimulation of the child's body with antigens and the formation of the child's immune system. According to a number of authors, there is currently an earlier crossover in the leukocyte formula, a tendency to eosinophilia, relative neutropenia, and an increase in the number of lymphocytes.

Lymphocyte changes

Estimating the number of lymphocytes in a blood test in children, first of all, take into account the age characteristics of the leukocyte formula. So, in children under the age of 5-6 years, lymphocytosis is considered to be an increase in the number of lymphocytes over 60% and their absolute number over 5.5-6.0 x10 9 /l. In children over 6 years of age with lymphocytosis, the leukocyte blood count shows the content of lymphocytes is more than 35%, and their absolute number exceeds 4 thousand. in 1 µl.

Functions of lymphocytes

The number of lymphocyte cells in the blood can be influenced by various physiological processes in the body. For example, a tendency to lymphocytosis is noted in children whose diet is dominated by carbohydrate foods, among residents of the highlands, during menstruation in women. In children with constitutional anomalies in the form of lymphatic diathesis, there is also a tendency to increase the content of lymphocytes in the blood.

The main function of lymphocytes is participation in the formation of the immune response. Therefore, secondary blood lymphocytic reactions are most often encountered in pediatric practice, accompanying:

viral infections (measles, influenza, rubella, adenovirus, acute viral hepatitis);
bacterial infections (tuberculosis, whooping cough, scarlet fever, syphilis)
endocrine diseases (hyperthyroidism, panhypopituitarism, Addison's disease, ovarian hypofunction, thymus hypoplasia);
allergic pathology (bronchial asthma, serum sickness);
immunocomplex and inflammatory diseases (Crohn's disease, ulcerative colitis, vasculitis);
taking certain medications (analgesics, nicotinamide, haloperidol).

Lymphocytosis in viral infections is recorded, as a rule, in the stage of convalescence - the so-called lymphocytosis of recovery.

Only among children (adults get sick extremely rarely) there is a disease of viral etiology - infectious lymphocytosis. The disease has a flu-like benign course, may occur with no clinical symptoms. In a blood test against the background of leukocytosis, the leukocyte blood formula demonstrates lymphocytosis.

Primary lymphocytosis in childhood is diagnosed with lymphoblastic leukemia.

lipopenia

Lymphopenia is stated with a decrease in the relative number of lymphocytes in children of the first days of life - below 30%, at the age of 5-6 years - below 50%, in children older than 6 years - below 20%. A decrease in the number of lymphocytes occurs as a result of:

failure of the development of lymphoid tissue,
inhibition of lymphocytopoiesis,
accelerated destruction of lymphocytes.

Relative lymphopenia is characteristic of infectious and inflammatory diseases accompanied by significant granulocytosis due to increased granulocytopoiesis. Absolute lymphocytopenia (the number of lymphocytes in children older than 6 years is less than 1.2–1.5 × 109/l) indicates immunodeficiency. Observed in tuberculosis, syphilis. In patients with these infections, in most cases, an increase in lymphocytic agranulocytes is a favorable sign. Lymphopenic reaction accompanies AIDS, sarcoidosis, disseminated lupus erythematosus, lymphogranulomatosis. Against the background of radiation and cytostatic therapy, drug-induced lymphocytopenia develops.

Change from monocytes

Monocytes are the largest leukocyte blood cells and are representatives of the macrophage system of the body. The main function of monocytes is phagocytic. A leukocyte blood formula with a monocyte count of more than 10% indicates blood monocytosis (their absolute number is over 0.4 × 109/l). Monocytosis has diagnostic value:

during the period of convalescence after acute infections;
with granulomatosis (sarcoidosis, tuberculosis, ulcerative colitis, syphilis);
with protozoal, fungal and viral infections;
with collagenoses;
blood diseases (monoblastic leukemia).

Mention should be made of the lymphotropic viral disease (caused by the herpes-like Epstein-Barr virus) that is quite common in children (more often) - infectious mononucleosis. The main symptoms of the disease are fever, inflammatory changes in the pharynx, lymphadenopathy, enlargement of the spleen and liver, typical changes in the blood test in the form of an increased number of atypical mononuclear cells (over 10%) against the background of moderate leukocytosis and lymphocytosis.

A decrease in the number of monocytes in the blood formula below 4% indicates monocytopenia. More often this condition occurs with vitamin B12 folic deficiency anemia, aplastic anemia, leukemia, and may accompany systemic lupus erythematosus. In severe septic processes, the disappearance of monocytes is an unfavorable sign.

Changes in eosinophils

Leukocyte blood count registering eosinophilia is not uncommon in pediatric practice. It is most often caused by allergies in children, which tends to increase at the present time, and helminthic infestations. An increase in the absolute number of eosinophilic granulocytes over 0.4x10 9 /l is considered eosinophilia. Eosinophils are normal in children, as well as adults, make up 0.5-5% of the total number of leukocytes. An increase in the percentage from 5% to 15% is called "small" eosinophilia, more than 15% - "large". In the latter case, the absolute content of eosinophilic cells in the peripheral blood may exceed 1.5? 10 9 / l. Eosinophilia against the background of significant leukocytosis is regarded as a leukemoid reaction of the eosinophilic type.

Eosinophilia can accompany systemic diseases of the connective tissue, occur as a result of drug allergies. In some infectious conditions during the recovery period, the leukocyte blood formula can register an increase in the number of eosinophils, the so-called “pink dawn of recovery” (eosinophils are pink when stained with a smear).

The eosinophilic reaction of the blood may accompany oncological diseases, more often with the localization of the primary tumor process in the nasopharynx, bronchi, stomach,. May accompany various forms of leukemia, malignant neoplasms of lymphoid tissue. A characteristic feature of tumor eosinophilia is the absence of an increase in the concentration of JgE in the blood serum.

Familial benign eosinophilias that are asymptomatic and inherited in an autosomal dominant manner have been described.

Change in the number of basophils

Basophilic granulocytes are involved in the formation of the immune (often allergic) and inflammatory response in the human body. With basophilia, the leukocytic blood formula shows the content of basophilic cells over 0.5-1%. Basophilia is rare. An increase in basophilic cells up to 2-3% often occurs with chronic myelogenous leukemia, lymphogranulomatosis, hemophilia, tuberculosis of the lymph nodes, with allergic reactions.

Conclusion

The tactics of the practitioner in various cellular reactions of the blood in children primarily depend on the clinical picture of the disease. If changes in the blood are a symptom of the disease, then, first of all, its treatment is carried out. If, after the patient's clinical recovery, pathological changes persist in the blood test, then additional diagnostic measures are necessary to diagnose complications or concomitant diseases. In some cases, it may be necessary to consult a pediatric hematologist or oncologist.

Leukocyte formula in children. Norm, decoding. Crossroads, what is it?

The general blood test in children, and in particular the leukocyte formula, differs from that in an adult. What are the norms and features of the formula in children? What is the crossover of blood formulas?

The leukocyte formula is the percentage of all types of leukocytes (granulocytes: neutrophils, including stab and segmented, eosinophils, basophils, agranulocytes: monocytes and lymphocytes). Those. in a stained blood smear, 100 leukocytes that fell into the field of view are counted in a row and the percentage of each type is calculated.

Newborns.

At birth, children have leukocytosis up to (10 to 9 per liter). Of these, neutrophils are predominant (60-70%). In this case, the formula shifts to the left, i.e. the number of sticks is increased up to 10-15%, sometimes there are single metamyelocytes. Lymphocytes about 30%. There is a conditional rule: neutrophils + lymphocytes are equal to about 90%. Other types of leukocytes are the same as in adults (basophils 0-1%, eosinophils 0.5-5%, monocytes 3-10%).

first 5 days of life.

On average, on the 5th day, the first cross of the formula occurs, i.e. the number of neutrophils and lymphocytes levels out, becoming an average of 45%.

From 10 days to 4-5 years.

Lymphocytes about 60%, neutrophils-30%

4-5 years.

On average, at the age of 4.5-5 years, the second cross of the formula occurs, i.e. again the number of neutrophils and lymphocytes levels off at 45%.

School age.

By school age, the leukocyte formula in children corresponds to that in adults.

The lymphocyte formula - the ratio of leukocytes (stab, segmented, eosinophils, lymphocytes, basophils and monocytes) in a stained blood smear - in children differs from that in adults up to about 4-5 years. In newborns, up to a week of age, it is approximately the same as in adults, and then comes the first cross. The leukocyte formula changes: the ratio of lymphocytes to neutrophils changes from approximately 20%/60% to 60%/20%. At 4-5 years old, there is a reverse crossover and no longer changes.

Cross leukocyte formula

What is the leukocyte formula:

Neutrophil (purple, right) and

lymphocyte (purple, left) -

main participants of the cross

The number of leukocytes and their varieties is the leukocyte formula. In an adult, it is relatively stable and changes only in diseases, when the content of different cells changes. However, in young children, rather large changes occur in it, which are called the crossover of the formula. The cross is observed in the norm and is not a sign of pathology.

Segmented neutrophils, lymphocytes: how do they change during decussation?

The crossover of the formula occurs due to the fact that in a small child, the formation and maturation of immunity takes place. Different forms of cells are formed in greater or lesser quantities, all this changes over time ... This is where regular changes in blood tests come from.

Approximately by the age of 10, the leukocyte formula ceases to change, and all values approach the norms that were described at the beginning of the article.

The biological role of the cross:

It is rather boring for a person who does not plan to connect his life with medicine to figure out which indicator and when is increased and which is lowered. If this is of interest to you, you can study and memorize the contents of the previous section in detail. However, if we are talking about your child's blood tests, and you just want to know if everything is in order with them, it is better to entrust their interpretation to a knowledgeable specialist who has been dealing with this for a long time. You just need to understand a few simple things.

The main thing that is needed while the child is growing is, if possible, to ensure that he grows up without stress: chronic and acute diseases, sudden climate change, long journeys, etc. In addition, immunity support would be very useful, with which childhood will pass without prolonged colds and frequent morbidity.

Moscow, st. Verkhnyaya Radishchevskaya, 7 building 1 of. 205

Moscow, st. Verkhnyaya Radishchevskaya, 7 building 1 of. 205 Tel:

24. Age features in the number of leukocytes. Double cross in the ratio of neutrophils and lymphocytes in children.

The number of leukocytes in newborns is increased and is equal to * 10 9 /l. The number of neutrophils is -60.5%, eosinophils - 2%, basophils -02%, monocytes -1.8%, lymphocytes - 24%. During the first 2 weeks, the number of leukocytes is reduced to 9 - 15 * 10 9 / l, by 4 years it decreases to 7-13 * 10 9 / l, and by 14 years it reaches the level characteristic of an adult. The ratio of neutrophils and lymphocytes changes, which causes the appearance of physiological crossovers.

First cross. In a newborn, the ratio of the content of these cells is the same as in an adult. In the subsequent sod. Nf falls, and Lmf increases, so that on the 3rd-4th day their number is equalized. In the future, the amount of NF continues to decrease and reaches 25% by the age of 1-2 years. At the same age, the amount of LMF is 65%.

Second cross. Over the next years, the number of Hf gradually increases, and Lmf decreases, so that in children at the age of 4 these indicators are equalized again and make up 35% of the total number of leukocytes. The amount of Nf continues to increase, while the amount of LMF decreases, and by the age of 14 these figures correspond to those in an adult (4-9 * 10 9 /l).

25. Genesis, structure, general and special. Properties and functions of neutophils

In the bone marrow, six successive morphological stages of neutrophil maturation can be observed: myeloblast, promyelocyte, myelocyte, metamyelocyte, stab and segmented cell:

In addition, there are also earlier, morphologically unidentifiable, committed neutrophil precursors: CFU-GM and CFU-G.

Neutrophil maturation is accompanied by a progressive decrease in nuclear size due to chromatin condensation and loss of nucleoli. As the neutrophil matures, the nucleus becomes serrated and finally acquires a characteristic segmentation. At the same time, changes occur in the cytoplasm of the neutrophil, where granules containing biological compounds accumulate, which will subsequently play such an important role in protecting the body. Primary (azurophilic) granules are blue inclusions approximately 0.3 µm in size containing elastase and myeloperoxidase. They first appear in the promyelocytic stage; when ripe, their number and intensity of staining decrease. Secondary (specific) granules, which contain lysozyme and other proteases, appear at the myelocyte stage. The coloration of these secondary granules determines the characteristic neutrophilic appearance of the cytoplasm.

Kinetics of neutrophils. According to the ability to divide, myeloblasts, promyelocytes and myelocytes belong to the mitotic group, i.e. have the ability to divide, the intensity of which falls from myeloblast to myelocyte. The subsequent stages of maturation of neutrophils are not associated with division. In the bone marrow, proliferating cells among neutrophils make up about 1/3, and the same amount is accounted for by granulocytic mitoses among all proliferating cells in the bone marrow. During the day, up to 4.0×10 9 neutrophils are produced per kilogram of body weight.

Structure. Neutrophil cytoplasm. At the stage of metamyelocyte and subsequent stages of maturation, the structures that ensure the synthesis of cytoplasmic proteins are reduced, the structure of lysosomes that provide the function of neutrophils is improved, and the ability for amoeboid mobility and deformation, which ensures the mobility and invasiveness of granulocytes, is enhanced.

neutrophil membrane. On the precursors of the granulocytic germ, CD34+CD33+ are determined, as well as receptors for G M - C S F, G - C S F, IL-1, IL-3, IL-6, IL-11, IL-12. The membrane also contains various molecules that are receptors for chemotactic signals, which include CCF, N-formyl-peptide.

Properties and functions. The function of neutrophils is to protect the body from infection. This process includes chemotaxis, phagocytosis and destruction of microorganisms. Chemotaxis involves the ability to detect and purposefully move towards microorganisms and foci of inflammation. Neutrophils have specific receptors for the C5a component of the complement system (produced in the classical or alternative pathways of complement activation) and for proteases released during tissue damage or direct bacterial exposure. In addition, neutrophils have receptors for N-formyl peptides secreted by bacteria and affected mitochondria. They also react to such products of inflammation, leukotriene LTB-4 and fibrinopeptides.

Neutrophils recognize foreign organisms using opsonin receptors. Fixation of serum IgG and complement on bacteria makes them recognizable to granulocytes. The neutrophil has receptors for the Fc fragment of the immunoglobulin molecule and the products of the complement cascade. These receptors initiate the processes of capture, absorption and adhesion of foreign objects.

Neutrophils engulf opsonized microorganisms with the help of cytoplasmic vesicles, called phagosomes. These vesicles move from the folded pseudopodia and fuse with the primary and secondary granules in an energy-dependent process during which explosive activation of glycolysis and glycogenolysis occurs in phagocytes. During cell degranulation, the contents of the granules are released into the phagosome and degradation enzymes are released: lysozyme, acid and alkaline phosphatases, elastazailactoferrin.

Finally, neutrophils destroy bacteria by metabolizing oxygen into products that are toxic to the ingested microorganisms. The oxidase complex generating these products consists of flavin- and heme-containing cytochrome b558-.

These reactions use the reducing agent NADPH and are stimulated by glucose-6-phosphate dehydrogenase and other hexose monophosphate shunt enzymes. As a result, the cell generates superoxide (O2) and hydrogen peroxide (H2O2), which are released into the phagosome to kill bacteria. Lactoferrin is involved in the formation of free hydroxyl radicals, and myeloperoxidase, using halides as cofactors, in the production of hypochloric acid (HOC1) and toxic chloramines.

To continue downloading, you need to collect the picture.

The leukocyte formula is an indicator of the state of peripheral blood, reflecting the percentage of leukocyte cells of various types. Normally, the ratio of cells of the lecopoietic series has characteristic features depending on the age of the child.

The situation with the formula in healthy children

Healthy newborns have shift of the leukocyte formula with a shift index of 0.2 (at a rate of 0.06 in adults). At the birth of a child in the formula, 60-65% of the leukogram is represented by neutrophils and 30-35% by lymphocytes. By the end of the first week of life, the number of these cells equalizes to ~ 45% and the “first crossover” of the leukocyte formula occurs, and by the 10-14th day, physiological lymphocytosis is formed in the blood of the newborn. The content of lymphocytes in the leukocyte formula is 55-60%. In addition, an increase in the number of monocytes up to 10% is characteristic. The second crossover in the leukocyte formula occurs at the age of 5-6, after which, by the age of 10, the blood leukogram acquires the features of an adult:

stab neutrophils - 1-6%,
segmented neutrophils 47-72%
lymphocytes 19-37%,
monocytes 6-8%,
eosinophils 0.5-5%,
basophils 0-1%.

Lymphocyte changes

Estimating the number of lymphocytes in a blood test in children, first of all, take into account the age characteristics of the leukocyte formula. So, in children under the age of 5-6 years, lymphocytosis is considered to be an increase in the number of lymphocytes over 60% and their absolute number over 5.5-6.0 x10 9 /l. In children older than 6 years with lymphocytosis leukocyte blood count demonstrates the content of lymphocytes more than 35%, and their absolute number exceeds 4 thousand. in 1 µl.

Functions of lymphocytes

The number of lymphocyte cells in the blood can be influenced by various physiological processes in the body. For example, a tendency to lymphocytosis is noted in children whose diet is dominated by carbohydrate foods, among residents of the highlands, during menstruation in women. In children with constitutional anomalies in the form of lymphatic diathesis, there is also a tendency to increase the content of lymphocytes in the blood.

viral infections (measles, influenza, rubella, adenovirus, acute viral hepatitis);
bacterial infections (tuberculosis, whooping cough, scarlet fever, syphilis)
endocrine diseases (hyperthyroidism, panhypopituitarism, Addison's disease, ovarian hypofunction, thymus hypoplasia);
allergic pathology (bronchial asthma, serum sickness);
immunocomplex and inflammatory diseases (Crohn's disease, ulcerative colitis, vasculitis);
taking certain medications (analgesics, nicotinamide, haloperidol).

Lymphocytosis in viral infections is recorded, as a rule, in the stage of convalescence - the so-called lymphocytosis of recovery.

Familial benign eosinophilias that are asymptomatic and inherited in an autosomal dominant manner have been described.

Change in the number of basophils

Basophilic granulocytes are involved in the formation of the immune (often allergic) and inflammatory response in the human body. With basophilia leukocyte formula of blood demonstrates the content of basophilic cells over 0.5-1%. Basophilia is rare. An increase in basophilic cells up to 2-3% often occurs with chronic myelogenous leukemia, lymphogranulomatosis, hemophilia, tuberculosis of the lymph nodes, with allergic reactions.

Conclusion

(with the exception of the first days of life, when neutrophilia is noted), persistent lymphocytosis, both relative and absolute, is characteristic (Table 2). In a newborn, the percentage of lymphocytes, gradually increasing, reaches 50-60 by the 5th day, and the percentage of neutrophils by the same time gradually decreases to 35-47.

The number of neutrophils and lymphocytes in different periods of childhood (in percent): a - first decussation; b - the second cross.

If you depict the changes in the number of neutrophils and lymphocytes in the form of curves (Fig.), then approximately between the 3rd-5th day there is an intersection of the curves - the so-called first crossover. By the end of the first month of life, the child's leukocyte formula is established, which is characteristic of the entire first year of life. The leukocyte formula of infants differs in some lability; it is relatively easily disturbed by strong crying and restlessness of the child, sudden changes in diet, cooling and overheating, and especially in various diseases.

Table 2. Leukocyte formula of a newborn (according to A.F. Tur, in%)

Leukocyte formula of children aged from 1 month to 15 years (according to A. F. Tur, in%)

The correct assessment of the leukocyte formula in diseases is of great importance and is possible when taking into account its features, due to the age of the child.

The greatest changes in the leukocyte formula are noted in the content of neutrophils and lymphocytes. The rest of the indicators do not differ significantly from those of adults.

Leukocyte classification

Development timeline:

I. Newborns:

Neutrophils 65-75%;

· lymphocytes 20-35%;

II. 4th day - the first physiological crossover:

neutrophils 45%;

lymphocytes 45%;

III. 2 years:

neutrophils 25%;

lymphocytes 65%;

IV. 4 years - the second physiological crossover:

neutrophils 45%;

lymphocytes 45%;

V. 14-17 years old:

Neutrophils 65-75%;

· lymphocytes 20-35%.

6. Lymph consists of lymphoplasm and formed elements, mainly lymphocytes (98%), as well as monocytes, neutrophils, and sometimes erythrocytes. Lymphoplasma It is formed by the penetration (drainage) of tissue fluid into the lymphatic capillaries, and then it is discharged through the lymphatic vessels of various calibers and flows into the venous system. Along the way, lymph passes through The lymph nodes, in which it is cleared of exogenous and endogenous particles, and is also enriched with lymphocytes.

According to the qualitative composition, lymph is divided into:

Peripheral lymph - up to the lymph nodes;

Intermediate lymph - after the lymph nodes;

Central lymph - lymph of the thoracic duct.

In the region of the lymph nodes, not only the formation of lymphocytes occurs, but also the migration of lymphocytes from the blood to the lymph, and then with the lymph flow they again enter the blood, and so on. These lymphocytes are recirculating pool of lymphocytes.

Lymph functions:

tissue drainage;

Enrichment with lymphocytes;

Cleansing the lymph from exogenous and endogenous substances.

LECTURE 7. Hematopoiesis

1. Types of hematopoiesis

2. Theories of hematopoiesis

3. T-lymphocytopoiesis

4. B-lymphocytopoiesis

1. Hematopoiesis(hemocytopoiesis) the process of formation of blood cells.

There are two types of hematopoiesis:

myeloid hematopoiesis:

erythropoiesis;

· granulocytopoiesis;

thrombopoiesis;

monocytopoiesis.

lymphoid hematopoiesis:

T-lymphocytopoiesis;

B-lymphocytopoiesis.

In addition, hematopoiesis is divided into two periods:

· embryonic;

post-embryonic.

Embryonic period of hematopoiesis leads to the formation of blood as a tissue and therefore is blood histogenesis. Postembryonic hematopoiesis is a process physiological regeneration blood like tissue.

The embryonic period of hematopoiesis is carried out in stages, replacing different hematopoietic organs. According to this embryonic hematopoiesis is divided into three stages:

yolk;

hepato-thymus-lienal;

medullo-thymus-lymphoid.

Yolk stage is carried out in the mesenchyme of the yolk sac, starting from the 2nd-3rd week of embryogenesis, from the 4th week it decreases and by the end of the 3rd month it completely stops. The process of hematopoiesis at this stage is carried out as follows, first in the mesenchyme of the yolk sac, as a result of the proliferation of mesenchymal cells, " blood islands, representing focal accumulations of process mesenchymal cells. Then there is a differentiation of these cells in two directions ( divergent differentiation):

Peripheral cells of the islet are flattened, interconnected and form the endothelial lining of the blood vessel;

The central cells round out and turn into stem cells.

Of these cells in the vessels, that is intravascular the process of formation of primary erythrocytes (erythroblasts, megaloblasts) begins. However, part of the stem cells is outside the vessels ( extravascular) and granular leukocytes begin to develop from them, which then migrate into the vessels.

The most important moments of the yolk stage are:

formation of blood stem cells;

formation of primary blood vessels.

Somewhat later (on the 3rd week), vessels begin to form in the mesenchyme of the body of the embryo, but they are empty slit-like formations. Pretty soon, the vessels of the yolk sac connect with the vessels of the body of the embryo, through these vessels the stem cells migrate into the body of the embryo and populate the anlage of future hematopoietic organs (primarily the liver), in which hematopoiesis is then carried out.

Hepato-thymus-splenic the stage of hematopoiesis is carried out at the beginning in the liver, a little later in the thymus (thymus gland), and then in the spleen. In the liver, mainly myeloid hematopoiesis occurs (only extravascularly), starting from the 5th week and until the end of the 5th month, and then gradually decreases and completely stops by the end of embryogenesis. The thymus is laid down on the 7-8th week, and a little later, T-lymphocytopoiesis begins in it, which continues until the end of embryogenesis, and then in the postnatal period until its involution (at 25-30 years). The process of formation of T-lymphocytes at this moment is called antigen independent differentiation. The spleen is laid on the 4th week, from 7-8 weeks it is populated with stem cells and universal hematopoiesis begins in it, that is, myeloilimphopoiesis. Hematopoiesis in the spleen is especially active from the 5th to the 7th months of intrauterine development of the fetus, and then myeloid hematopoiesis is gradually inhibited and by the end of embryogenesis (in humans) it completely stops. Lymphoid hematopoiesis is preserved in the spleen until the end of embryogenesis, and then in the postembryonic period.

Consequently, hematopoiesis at the second stage in these organs is carried out almost simultaneously, only extravascularly, but its intensity and qualitative composition in different organs are different.

Medullo-thymus-lymphoid stage of hematopoiesis. The laying of the red bone marrow begins from the 2nd month, hematopoiesis begins in it from the 4th month, and from the 6th month it is the main organ of myeloid and partially lymphoid hematopoiesis, that is, it is universal hematopoietic organ. At the same time, lymphoid hematopoiesis is carried out in the thymus, in the spleen and in the lymph nodes. If the red bone marrow is not able to satisfy the increased need for blood cells (in case of bleeding), then the hematopoietic activity of the liver and spleen can be activated - extramedullary hematopoiesis.

The postembryonic period of hematopoiesis is carried out in the red bone marrow and lymphoid organs (thymus, spleen, lymph nodes, tonsils, lymphoid follicles).

The essence of the process of hematopoiesis lies in the proliferation and gradual differentiation of stem cells into mature blood cells.

2. Theories of hematopoiesis:

unitary theory (A. A. Maksimov, 1909) - all blood cells develop from a single stem cell precursor;

Dualistic theory provides for two sources of hematopoiesis, for myeloid and lymphoid;

The polyphyletic theory provides for each shaped element its own source of development.

At present, the unitary theory of hematopoiesis is generally accepted, on the basis of which a scheme of hematopoiesis has been developed (I. L. Chertkov and A. I. Vorobyov, 1973).

In the process of gradual differentiation of stem cells into mature blood cells, intermediate cell types are formed in each row of hematopoiesis, which form classes of cells in the hematopoiesis scheme. In total, 6 classes of cells are distinguished in the hematopoietic scheme:

1st class - stem cells;

Grade 2 - semi-stem cells;

Grade 3 - unipotent cells;

Grade 4 - blast cells;

Grade 5 - maturing cells;

Grade 6 - mature shaped elements.

Morphological and functional characteristics of cells of various classes of the hematopoietic scheme.

1 class- stem pluripotent cell capable of maintaining its population. In morphology, it corresponds to a small lymphocyte, is pluripotent, that is, capable of differentiating into any blood cell. The direction of stem cell differentiation is determined by the level of this formed element in the blood, as well as the influence of the microenvironment of stem cells - the inductive influence of stromal cells of the bone marrow or other hematopoietic organ. Maintaining the population of stem cells is ensured by the fact that after mitosis of the stem cell, one of the daughter cells takes the path of differentiation, and the other takes the morphology of a small lymphocyte and is a stem cell. Stem cells divide rarely (once every six months), 80% of stem cells are at rest and only 20% are in mitosis and subsequent differentiation. In the process of proliferation, each stem cell forms a group or clone of cells, and therefore stem cells in the literature are often referred to as colony forming units- CFU.

Grade 2- semi-stem, limitedly pluripotent (or partially committed) precursor cells of myelopoiesis and lymphopoiesis. They have the morphology of a small lymphocyte. Each of them gives a clone of cells, but only myeloid or lymphoid. They divide more often (after 3-4 weeks) and also maintain the size of their population.

3rd grade- unipotent poetin-sensitive precursor cells of their hematopoietic series. Their morphology also corresponds to a small lymphocyte. Able to differentiate into only one type of shaped element. They divide frequently, but some of the descendants of these cells enter the path of differentiation, while others retain the size of the population of this class. The frequency of division of these cells and the ability to differentiate further depends on the content of special biologically active substances in the blood - poetins specific for each series of hematopoiesis (erythropoietins, thrombopoietins, and others).

The first three classes of cells are combined into a class of morphologically unidentifiable cells, since they all have the morphology of a small lymphocyte, but their potential for development is different.

4th grade- blast (young) cells or blasts (erythroblasts, lymphoblasts, and so on). They differ in morphology from both the three preceding and subsequent classes of cells. These cells are large, have a large loose (euchromatin) nucleus with 2-4 nucleoli, the cytoplasm is basophilic due to the large number of free ribosomes. They often divide, but the daughter cells all take the path of further differentiation. According to cytochemical properties, blasts of different hematopoietic lines can be identified.

5th grade- a class of maturing cells characteristic of their hematopoietic series. In this class, there may be several varieties of transitional cells - from one (prolymphocyte, promonocyte), to five in the erythrocyte row. Some maturing cells may enter the peripheral blood in small numbers (eg, reticulocytes, juvenile and stab granulocytes).

6th grade- mature blood cells. However, it should be noted that only erythrocytes, platelets and segmented granulocytes are mature end differentiated cells or their fragments. Monocytes are not terminally differentiated cells. Leaving the bloodstream, they differentiate into end cells - macrophages. Lymphocytes, when they encounter antigens, turn into blasts and divide again.

The set of cells that make up the line of differentiation of a stem cell into a certain shaped element form it differon or histological series. For example, erythrocyte differon is: stem cell, semi-stem cell, myelopoiesis precursor, unipotent erythropoietin-sensitive cell, erythroblast, maturing pronormocyte cells, basophilic normocyte, polychromatophilic normocyte, oxyphilic normocyte, reticulocyte, erythrocyte. In the process of maturation of erythrocytes in the 5th grade, the following occurs: the synthesis and accumulation of hemoglobin, the reduction of organelles, and the reduction of the nucleus. Normally, the replenishment of erythrocytes is carried out mainly due to the division and differentiation of maturing cells of pronormocytes, basophilic and polychromatophilic normocytes. This type of hematopoiesis is called homoplastic hematopoiesis. With severe blood loss, the replenishment of erythrocytes is ensured not only by increased division of maturing cells, but also by cells of 4, 3, 2, and even 1 classes - a heteroplastic type of hematopoiesis, which already precedes reparative blood regeneration.

3. Unlike myelopoiesis, lymphocytopoiesis in the embryonic and postembryonic periods, it is carried out in stages, replacing different lymphoid organs. In T- and B-lymphocytopoiesis, three stages:

bone marrow stage

stage of antigen-independent differentiation, carried out in the central immune organs;

stage of antigen-dependent differentiation, carried out in peripheral lymphoid organs.

At the first stage of differentiation, the precursor cells of T- and B-lymphocytopoiesis are formed from stem cells, respectively. At the second stage, lymphocytes are formed that can only recognize antigens. At the third stage, effector cells are formed from the cells of the second stage, capable of destroying and neutralizing the antigen.

The process of development of T- and B-lymphocytes has both general patterns and significant features and therefore is subject to separate consideration.

The first stage of T-lymphocytopoiesis carried out in the lymphoid tissue of the red bone marrow, where the following cell classes are formed:

1st class - stem cells;

Class 2 - semi-stem precursor cells of lymphocytopoiesis;

Class 3 - unipotent T-poietin-sensitive precursor cells of T-lymphocytopoiesis, these cells migrate into the bloodstream and reach the thymus with blood.

Second phase- the stage of antigen-independent differentiation is carried out in the thymus cortex. Here the further process of T-lymphocytopoiesis continues. Under the influence of a biologically active substance thymosin secreted by stromal cells, unipotent cells turn into T-lymphoblasts - class 4, then into T-prolymphocytes - class 5, and the latter into T-lymphocytes - class 6. In the thymus, unipotent cells develop independently three subpopulations T-lymphocytes: killers, helpers and suppressors. In the thymus cortex, all the listed subpopulations of T-lymphocytes acquire different receptors for various antigenic substances (the mechanism of formation of T-receptors remains unclear), but the antigens themselves do not enter the thymus. Protection of T-lymphocytopoiesis from foreign antigenic substances is achieved two mechanisms:

The presence in the thymus of a special hemato-thymic barrier;

lack of lymphatic vessels in the thymus.

As a result of the second stage, receptor(afferent or T0-) T-lymphocytes - killers, helpers, suppressors. At the same time, lymphocytes in each of the subpopulations differ from each other by different receptors, however, there are also cell clones that have the same receptors. T-lymphocytes are formed in the thymus, which also have receptors for their own antigens, but such cells are destroyed here by macrophages. Formed in the cortex, T-receptor lymphocytes (killers, helpers and suppressors), without entering the medulla, penetrate into the vascular bed and are carried by blood flow to the peripheral lymphoid organs.

Third stage- the stage of antigen-independent differentiation is carried out in the T-zones of peripheral lymphoid organs - lymph nodes, spleen and others, where conditions are created for the antigen to meet with a T-lymphocyte (killer, helper or suppressor) that has a receptor for this antigen. However, in most cases, the antigen acts on the lymphocyte not directly, but indirectly - through macrophage, that is, at first, the macrophage phagocytizes the antigen, partially cleaves it intracellularly, and then the active chemical groups of the antigen - antigenic determinants are brought to the surface of the cytolemma, contributing to their concentration and activation. Only then these determinants are transferred by macrophages to the corresponding receptors of different subpopulations of lymphocytes. Under the influence of the corresponding antigen, the T-lymphocyte is activated, changes its morphology and turns into a T-lymphoblast, or rather into T-immunoblast, since this is no longer a class 4 cell (formed in the thymus), but a cell that arose from a lymphocyte under the influence of an antigen.

The process of transformation of a T-lymphocyte into a T-immunoblast is called the reaction blast transformation. After that, the T-immunoblast, which arose from the T-receptor killer, helper or suppressor, proliferates and forms a cell clone. T-killer immunoblast produces a clone of cells, among which are:

T-memory (killers);

T-killers or cytotoxic lymphocytes, which are effector cells that provide cellular immunity, that is, the protection of the body from foreign and genetically modified own cells.

After the first meeting of a foreign cell with a receptor T-lymphocyte, a primary immune response develops - blast transformation, proliferation, the formation of T-killers and the destruction of the foreign cell by them. Memory T-cells, upon repeated encounter with the same antigen, provide a secondary immune response by the same mechanism, which proceeds faster and stronger than the primary one.

T-helper immunoblast gives a clone of cells, among which there are T-memory, T-helpers, secreting a mediator - lymphokine, stimulating humoral immunity - an inducer of immunopoiesis. The mechanism of formation of T-suppressors, the lymphokine of which inhibits the humoral response, is similar.

Thus, as a result of the third stage of T-lymphocytopoiesis, effector cells of cellular immunity (T-killers), regulatory cells of humoral immunity (T-helpers and T-suppressors), as well as T-memory of all populations of T-lymphocytes are formed, which, when they meet again with the same antigen again provide the body's immune defense in the form of a secondary immune response. In providing cellular immunity, consider two destruction mechanisms killer antigenic cells:

contact interaction - "kiss of death", with the destruction of the cytolemma of the target cell;

· distant interaction - by means of allocation of the cytotoxic factors acting on a cell-target gradually and for a long time.

4. The first stage of B-lymphocytopoiesis carried out in the red bone marrow, where the following cell classes:

1st class - stem cells;

Class 2 - semi-stem cells-precursors of lymphopoiesis;

Class 3 - unipotent B-poietin-sensitive precursor cells of B-lymphocytopoiesis.

Second phase antigen-independent differentiation in birds is carried out in a special central lymphoid organ - the bursa of Fabricius. Mammals and humans do not have such an organ, and its analogue has not been precisely established. Most researchers believe that the second stage is also carried out in the red bone marrow, where B-lymphoblasts are formed from unipotent B cells - class 4, then B-prolymphocytes - class 5 and lymphocytes - class 6 (receptor or B0). During the second stage, B-lymphocytes acquire a variety of receptors for antigens. At the same time, it was found that the receptors are represented by immunoglobulin proteins, which are synthesized in the maturing B-lymphocytes themselves, and then brought to the surface and integrated into the plasmalemma. The terminal chemical groups of these receptors are different and this explains the specificity of their perception of certain antigenic determinants of different antigens.

Third stage- antigen-dependent differentiation is carried out in the B-zones of peripheral lymphoid organs (lymph nodes, spleen and others) where the antigen meets the corresponding B-receptor lymphocyte, its subsequent activation and transformation into an immunoblast. However, this happens only with the participation of additional cells - a macrophage, a T-helper, and possibly a T-suppressor, that is, the activation of a B-lymphocyte requires the cooperation of the following cells: B-receptor lymphocyte, macrophage, T-helper (T-suppressor), as well as a humoral antigen (bacteria, virus, protein, polysaccharide, and others). The process of interaction takes place in following sequence:

macrophage phagocytizes the antigen and brings determinants to the surface;

influences antigenic determinants on B-lymphocyte receptors;

influences the same determinants on T-helper and T-suppressor receptors.

The influence of the antigenic stimulus on the B-lymphocyte is insufficient for its blast transformation. This occurs only after the T-helper is activated and releases an activating lymphokine. After such an additional stimulus, a blast transformation reaction occurs, that is, the transformation of a B-lymphocyte into an immunoblast, which is called plasmablast, since as a result of the proliferation of the immunoblast, a clone of cells is formed, among which there are:

· In mind;

Plasma cells, which are the effector cells of humoral immunity.

These cells synthesize and secrete into the blood or lymph immunoglobulins(antibodies) of different classes that interact with antigens and antigen-antibody complexes (immune complexes) are formed and thereby neutralize antigens. The immune complexes are then phagocytosed by neutrophils or macrophages.

However, antigen-activated B-lymphocytes are capable of synthesizing non-specific immunoglobulins in a small amount. Under the influence of T-helper lymphokines, firstly, the transformation of B-lymphocytes into plasma cells occurs, secondly, the synthesis of non-specific immunoglobulins is replaced by specific ones, and thirdly, the synthesis and release of immunoglobulins by plasma cells is stimulated. T-suppressors are activated by the same antigens and secrete a lymphokine that inhibits the formation of plasma cells and the synthesis of immunoglobulins by them until complete cessation. The combined effect of T-helper and T-suppressor lymphokines on the activated B-lymphocyte regulates the intensity of humoral immunity. Complete suppression of the immune system is called tolerance or unresponsiveness, that is, the absence of an immune response to the antigen. It can be caused both by the predominant stimulation of the T-suppressor antigens, and by the inhibition of the function of T-helpers or the death of T-helpers (for example, in AIDS).