The first cross in the leukocyte formula. Leukocyte formula in children. Age-related features in the number of leukocytes. Double crossover in the ratio of neutrophils and lymphocytes in children

Leukocyte formula crossover, blood formula crossover... This definition can be heard quite often when it comes to blood tests in children. What can “cross” the results of the study, how do laboratory technicians determine this, and what does this even 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 technician writes in the results absolute number each of these groups of cells. For example, on average there are 4-5 × 1012 red blood cells per 1 liter of blood, 3-9 × 109 leukocytes per the same volume.

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

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

Instead of counting the exact number of cells of a given shape, researchers report 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 is the leukocyte formula. In an adult, it is relatively stable and changes only during diseases, when the content of different cells changes. However, in young children, quite large changes occur in it, which are called decussation of the formula. The crossover is observed normally and is not a sign of pathology.

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

The crossover of the formula occurs due to the fact that small child formation and maturation of immunity occurs. Different shapes cells are formed in larger or smaller quantities, all this changes over time... This is where the natural changes in blood tests come from.

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

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, by the age of one week, changes occur: the indicators “approach” each other. As a result, it turns out that segmented cells are decreased and lymphocytes are increased relative to the values ​​that the little man had quite recently. Both parameters “occur” at a value of 45% - by the age of 4-7 days in the child’s blood they become equal.

Then each of them continues to change in the same direction, but at 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 subsequent months and years do not bring such dramatic changes in the composition of the blood as the first days of life. However, gradually segmented neutrophils increase, and lymphocytes decrease again. At 5-6 years old, their number becomes equal again. This is the second and last crossover of the leukocyte formula. Then some more changes occur, and everything turns out in such a way that, as a result, neutrophils are increased, and lymphocytes are decreased relative to that “average” 45%.

At approximately 10 years of age, the leukocyte formula stops changing, and all values ​​approach the norms that were described at the beginning of the article.

Biological role of the cross:

For a person who does not plan to connect his life with medicine, it is quite boring to understand which indicator is increased and which is decreased and when. If this is of interest to you, you can study in detail and remember the contents of the previous section. However, if we are talking about your child's blood tests, and you just want to know if everything is in order, 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.

Crossing the formula is a normal, physiological phenomenon. The immunity of a child who has recently been born experiences a big shake-up, as it immediately begins to be affected by a large number of irritants. 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,
ensure that he grows up without stress: chronic and acute diseases, sudden climate change, long journeys, etc. In addition, immune support would be very useful, with which childhood will pass without lingering colds and frequent illness.

Reception Transfer Factor drug, created on the basis of information molecules, can help with this. These molecules teach lymphocytes proper operation, which allows the child’s immune system to mature faster and acquire high resistance to all possible diseases by creating a pledge good health for the future.

Leukocytes - cells white, along with platelets and red blood cells, make up the cellular structure of human blood. Heterogeneous in their composition, they perform a single function: they vigilantly guard health, protecting the body from any external and internal threats, be it viral or bacterial infection, mechanical injury or cancer. Leukocyte formula blood, or leukogram - an indicator that evaluates the amount individual species white blood cells relative to them total number and is usually expressed as a percentage. The study of the white formula is an element of the UAC ( general analysis blood) and is prescribed:

• during routine preventive examinations
• if an infectious disease is suspected
• in case of exacerbations of chronic diseases
• for unidentified diseases with vague symptoms
• to monitor the effectiveness of certain medications

In all of the above cases clinical analysis blood with leukocyte formula helps to recognize the disease on early stages or make the correct diagnosis in complex cases.

Types and role of leukocytes

All leukocytes are, to one degree or another, capable of phagocytosis and amoeboid movement. White blood cells differ in the presence of special granules in their contents, susceptible to specific staining, and are divided into granulocytes and agranulocytes.

• Granulocytes:
  • Neutrophils are classic phagocytes, eaters of foreign cells. Depending on their maturity, cells are divided into young (rod) and mature (segmented) forms.
  • Eosinophils are also capable of phagocytosis, but primarily trigger the mechanisms of inflammatory and allergic reactions at the local level.
  • Basophils - perform a transport function, instantly directing other types of leukocytes to the lesion.
• Agranulocytes:
  • Lymphocytes. These cells have two subtypes: B and T. B lymphocytes provide cellular memory to pathogenic external agents and play important role in the formation of immunity. T-lymphocytes are divided into T-killers (destroy foreign cells), T-helpers (support T-killers for biochemical level) and T-suppressors (suppress the immune response so as not to harm the cells of one’s own body).
  • Monocytes - provide phagocytosis, and also contribute to the restoration of damaged tissues and trigger an immune response.

Venous blood is better suited for studying the white formula, since that taken from a finger often contains particles of soft tissue, which complicates diagnosis. On the eve of blood sampling for analysis, experts recommend giving up smoking, hardening procedures and baths, and avoiding physical activity, and also not eat food at least 8 hours before the procedure: all these factors can distort the objective picture.

After the obtained blood is prepared for examination in a special way and stained with reagents, laboratory assistants begin to decipher the leukocyte formula of the blood. Specialists examine smears under a microscope, visually determining the number of leukocytes per 100-200 cells in a certain area, or use special equipment. Machine counting of leukocytes using an automatic hemoanalyzer is considered more reliable, since the calculation is based on a larger amount of initial data (minimum 2000 cells).

Normal values ​​and features of the leukogram

The following leukoformula parameters are considered normal:

• neutrophils:
  • stab: 1-6
  • segmented: 47-72
• lymphocytes: 20-39
• eosinophils: 0-5
• basophils: 1-6
• monocytes: 3-12

A discrepancy between these indicators is allowed: no more than one or two units, up or down. In general, the parameters of the leukocyte formula are normally identical in men and women. However, in the latter, the absolute number of leukocytes in the blood is lower: (3.2 - 10.2)*109/l versus (4.3 - 11.3)*109/l in representatives of the stronger sex. A significant increase in the number of white blood cells occurs in women during pregnancy. This is a physiological phenomenon associated with the active production of fetal blood cells and does not require treatment. Here another nuance of reading a leukogram is revealed: not only relative, but also absolute values ​​of the number of white cells are important for diagnosis. A change in these indicators indicates the presence in the body pathological processes.

Leukocyte formula in children

When deciphering the leukocyte blood formula in children, it is necessary to take into account that it normal values vary depending on the age of the child. In a newborn, up to 30% of lymphocytes and up to 70% of neutrophils are determined in the blood, but by the fifth day of life the first “crossover” occurs: the relative number of these cells becomes approximately the same. By the end of the first month and throughout the first year of life, the picture stabilizes: now there are an average of 65 lymphocytes and 30 neutrophils per 100 white cells. By 3-5 years, the number of neutrophils gradually increases, and lymphocytes decrease. During this period of life, a second “crossover” occurs, after which the values ​​of the leukocyte formula begin to tend to the normal leukogram of an adult. At the age of 14-15 years, the white formula practically repeats the leukoformula of a mature person. At the same time, the relative number of other types of leukocytes changes slightly throughout life.

The general picture of leukogram in children early age very flexible and can change not only depending on diseases, but also with emotional disorders and changes in nutritional patterns.

Changes in leukocyte formula

For diseases and pathological conditions ratio different types leukocytes changes, and in some cases the picture is so indicative that it allows an accurate diagnosis to be made accurately. Conditions associated with changes in the number of white blood cells are usually denoted by terms with the endings “-iya” or “-ez” (“-oz”) in case of their increase (neutrophilia, eosinophilia) and “-singing” in case of decrease (basopenia). Here are just some of the reasons why the leukogram deviates from the norm.

Special cases of neutrophilia are a shift in the leukocyte formula to the left and to the right.

The essence of these changes becomes clearer if you imagine the process of development of neutrophils from in the form of a scale, where young cells are on the left and mature cells on the right: myeloblast - promyelocyte - myelocyte - metamyelocyte - band neutrophil - segmented neutrophil. The normal ratio of young and mature cell forms is 0.05 - 0.1.

A shift of the leukogram to the left, towards an increase in the number of young cells, indicates the occurrence of acute inflammatory and infectious processes, acute bleeding and poisoning, but can be considered as normal during pregnancy. Special case This phenomenon is a shift to the left with rejuvenation, when the youngest forms of neutrophils enter the bloodstream. This is a sign of acute and chronic leukemia. A shift in the leukocyte formula to the right is, on the contrary, an increase in the level of mature forms of neutrophils. This condition develops with liver and kidney diseases, deficiency of certain vitamins, and radiation sickness. Applications of the leukogram method and its correct interpretation - important element timely diagnosis and treatment of a number of diseases that are accompanied by quantitative and qualitative changes in the cellular composition of the blood.

Leukocyte formula is an indicator of the condition of peripheral blood, reflecting the percentage of leukocyte cells different types. Normally, the ratio of cells of the lekopoietic series is characteristics depending on the age of the child.

The situation with the formula in healthy children

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

• band neutrophils – 1-6%,
• segmented neutrophils 47-72%
• lymphocytes 19-37%,
• monocytes 6-8%,
• eosinophils 0.5-5%,
• basophils0-1%.

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 until 5-6 years of age is a physiological compensatory mechanism associated with pronounced stimulation child's body antigens and formation immune system child. According to a number of authors, currently there is an earlier crossover in the leukocyte formula, a tendency to eosinophilia, relative neutropenia and an increase in the number of lymphocytes.

Changes in lymphocytes

When assessing the number of lymphocytes in a blood test in children, they first take into account the age-related characteristics of the leukocyte formula. Thus, in children under the age of 5-6 years, lymphocytosis is considered to be an increase in the relative 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 leukocyte blood count demonstrates a lymphocyte content of 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 organism. For example, a tendency to lymphocytosis is observed in children whose diet is dominated by carbohydrate foods, in residents of high mountains, and during menstruation in women. Children with constitutional abnormalities in the form of lymphatic diathesis also have a tendency to increase the content of lymphocytes in the blood.

The main function of lymphocytes is to participate in the formation of the immune response. Therefore, most often in pediatric practice there are secondary lymphocytic blood reactions that accompany:

• 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, thymic hypoplasia);
• allergic pathology ( bronchial asthma, serum sickness);
• immunocomplex and inflammatory diseases(Crohn's disease, nonspecific ulcerative colitis, vasculitis);
• taking certain medications (analgesics, nicotinamide, haloperidol).

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

Familial benign eosinophilias have been described, occurring asymptomatically and inherited in an autosomal dominant manner.

Change in the number of basophils

Basophilic granulocytes are involved in the formation of the immune (usually allergic) and inflammatory response in the human body. For basophilia leukocyte blood count demonstrates a basophilic cell content of over 0.5-1%. Basophilia is a rare phenomenon. An increase in basophilic cells up to 2-3% often occurs when chronic myeloid leukemia, lymphogranulomatosis, hemophilia, tuberculosis lymph nodes, for allergic reactions.

Conclusion

The tactics of a practicing physician for various cellular blood reactions in children primarily depend on clinical picture diseases. If changes in the blood are a symptom of a disease, then, first of all, it is treated. If, after the patient’s clinical recovery, blood tests still show pathological changes, then additional diagnostic measures for the purpose of diagnosing complications or concomitant disease. In some cases, it may be necessary to consult a pediatric hematologist or oncologist.

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

Classification of leukocytes

Development timeframe:

I. Newborns:

· neutrophils 65-75%;

· lymphocytes 20-35%;

II. 4th day - first physiological crossover:

· neutrophils 45%;

· lymphocytes 45%;

III. 2 years:

· neutrophils 25%;

· lymphocytes 65%;

IV. 4 years - second physiological crossover:

· neutrophils 45%;

· lymphocytes 45%;

V. 14-17 years:

· 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 is formed through the penetration (drainage) of tissue fluid into the lymphatic capillaries, and then is drained through lymphatic vessels of various sizes and flows into 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.

Based on its qualitative composition, lymph is divided into:

· peripheral lymph - to the lymph nodes;

· intermediate lymph - after the lymph nodes;

· central lymph - thoracic duct lymph.

In the area of ​​the lymph nodes, not only the formation of lymphocytes occurs, but also the migration of lymphocytes from the blood into the lymph, and then with the flow of lymph they again enter the blood, and so on. These lymphocytes make up recirculating pool of lymphocytes.

Functions of lymph:

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;

thrombocytopoiesis;

· monocytopoiesis.

lymphoid hematopoiesis:

· T-lymphocytopoiesis;

· B-lymphocytopoiesis.

In addition, hematopoiesis is divided into two periods:

· embryonic;

· postembryonic.

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

The embryonic period of hematopoiesis occurs 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 carried out in the mesenchyme yolk sac, starting from the 2-3rd 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 branched mesenchymal cells. Then differentiation of these cells occurs in two directions ( divergent differentiation):

The peripheral cells of the islet flatten, connect with each other and form the endothelial lining blood vessel;

· the central cells round up and turn into stem cells.

From these cells in the vessels, that is, intravascularly the process of formation of primary erythrocytes (erythroblasts, megaloblasts) begins. However, some stem cells end up outside the blood vessels ( extravascular) and granular leukocytes begin to develop from them, which then migrate into the vessels.

Most important points yolk stage are:

formation of blood stem cells;

· formation of primary blood vessels.

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

Hepato-thymus-splenic the stage of hematopoiesis occurs initially in the liver, somewhat later in the thymus (thymus gland), and then in the spleen. In the liver, mainly myeloid hematopoiesis occurs (extravascularly only), starting from the 5th week until the end of the 5th month, and then gradually decreases and completely stops by the end of embryogenesis. The thymus is formed at 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 formed in the 4th week, from 7-8 weeks it is populated with stem cells and universal hematopoiesis begins in it, that is, myelolymphopoiesis. Hematopoiesis in the spleen is especially active from the 5th to 7th months of intrauterine development of the fetus, and then myeloid hematopoiesis is gradually suppressed and by the end of embryogenesis (in humans) it completely stops. Lymphoid hematopoiesis remains in the spleen until the end of embryogenesis, and then in the postembryonic period.

Consequently, hematopoiesis at the second stage in the named organs occurs almost simultaneously, only extravascularly, but its intensity and qualitative composition are in different organs are different.

Medullo-thymus-lymphoid stage of hematopoiesis. The formation of red bone marrow begins from the 2nd month, hematopoiesis in it begins 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 occurs in the thymus, spleen and lymph nodes. If the red bone marrow is not able to satisfy the increased need for formed elements of blood (during bleeding), then the hematopoietic activity of the liver and spleen may become more active - extramedullary hematopoiesis.

Postembryonic period of hematopoiesis - carried out in red bone marrow and lymphoid organs (thymus, spleen, lymph nodes, tonsils, lymphoid follicles).

The essence of the process of hematopoiesis is the proliferation and step-by-step differentiation of stem cells into mature blood cells.

2. Theories of hematopoiesis:

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

· the dualistic theory provides for two sources of hematopoiesis, myeloid and lymphoid;

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

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

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

· Class 1 - stem cells;

· Class 2 - semi-stem cells;

· Class 3 - unipotent cells;

· 4th class - blast cells;

· Class 5 - maturing cells;

· 6th grade - mature shaped elements.

Morphological and functional characteristic cells of different classes of hematopoiesis.

1 class- a pluripotent stem cell capable of maintaining its population. Its morphology corresponds to a small lymphocyte and is pluripotent, that is, capable of differentiating into any formed element of blood. 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 size of the stem cell population 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 on the morphology of a small lymphocyte and is a stem cell. Stem cells rarely divide (once every six months), 80% of stem cells are in a state of 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 called colony-forming units- CFU.

2nd grade- semi-stem, limited pluripotent (or partially committed) precursor cells of myelopoiesis and lymphopoiesis. They have the morphology of a small lymphocyte. Each of them produces a clone of cells, but only myeloid or lymphoid. They divide more often (every 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 the descendants of these cells some enter the path of differentiation, while others maintain the population size 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 developmental potencies are different.

4th grade- blast (young) cells or blasts (erythroblasts, lymphoblasts, etc.). 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 large number free ribosomes. They divide frequently, but the daughter cells all embark on the path of further differentiation. Based on their cytochemical properties, blasts of different hematopoietic series can be identified.

5th grade- a class of maturing cells characteristic of their hematopoietic series. In this class there can be several varieties of transitional cells - from one (prolymphocyte, promonocyte) to five in the erythrocyte series. Some maturing cells in small quantity can enter the peripheral blood (for example, reticulocytes, young and band granulocytes).

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

The totality 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, the erythrocyte differential is composed of: stem cell, semi-stem myelopoiesis precursor cell, unipotent erythropoietin-sensitive cell, erythroblast, maturing pronormocyte cells, basophilic normocyte, polychromatophilic normocyte, oxyphilic normocyte, reticulocyte, erythrocyte. In the process of maturation of erythrocytes in class 5, the following occurs: synthesis and accumulation of hemoglobin, reduction of organelles, 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. In case of severe blood loss, the replenishment of red blood cells is ensured not only by the increased division of maturing cells, but also by cells of classes 4, 3, 2 and even class 1, a heteroplastic type of hematopoiesis that 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 there are three stages:

· bone marrow stage;

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

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

At the first stage of differentiation, stem cells form precursor cells of T- and B-lymphocytopoiesis, 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 classes of cells are formed:

· Class 1 - 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 the blood.

Second phase- the stage of antigen-independent differentiation occurs in the thymus cortex. Here the further process of T-lymphocytopoiesis continues. Biologically influenced 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, three cells develop independently from unipotent cells subpopulations T-lymphocytes: killers, helpers and suppressors. In the thymus cortex, all of 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 of a special blood-thymus barrier in the thymus;

· lack 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. In the thymus, T-lymphocytes are formed that have receptors for their own antigens, but such cells are destroyed here by macrophages. T-receptor lymphocytes (killers, helpers and suppressors) formed in the cortex, without entering the medulla, penetrate into the vascular bed and are carried by the bloodstream into the peripheral lymphoid organs.

Third stage- the stage of antigen-dependent 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 a T-lymphocyte (killer, helper or suppressor) that has a receptor for this antigen. However, in most cases, the antigen does not act directly on the lymphocyte, but indirectly - through macrophage, that is, first the macrophage phagocytizes the antigen, partially breaks it down 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 are these determinants transmitted 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 arising from a lymphocyte under the influence of an antigen.

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

· T-memory (killers);

· Killer T-cells or cytotoxic lymphocytes, which are effector cells that provide cellular immunity, that is, the body’s protection 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, formation of killer T-cells and their destruction of the foreign cell. Memory T cells, when encountering the same antigen again, provide a secondary immune response using the same mechanism, which is faster and stronger than the primary one.

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

Thus, as a result of the third stage of T-lymphocytopoiesis, effector cells of cellular immunity (T-killers), regulatory cells humoral immunity(T-helpers and T-suppressors), as well as T-memories of all populations of T-lymphocytes, which, upon repeated encounter with the same antigen, will again provide immune protection the body in the form of a secondary immune response. Providing cellular immunity is considered two destruction mechanisms killer antigenic cells:

· contact interaction - “the kiss of death”, with the destruction of a section of the cytolemma of the target cell;

· distant interaction - through the release of cytotoxic factors that act on the target cell gradually and for a long time.

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

· Class 1 - stem cells;

· Class 2 - semi-stem precursor cells 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 lack such an organ, and its analogue has not been precisely established. Most researchers believe that the second stage also takes place in the red bone marrow, where B-lymphoblasts (class 4) are formed from unipotent B cells, then B-prolymphocytes (class 5) and lymphocytes (class 6) (receptor or B0). During the second stage, B lymphocytes acquire a variety of antigen receptors. It has been established 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 is what 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 occurs only with the participation of additional cells - macrophage, T-helper, and possibly T-suppressor, that is, to activate the B-lymphocyte, cooperation of the following cells is necessary: ​​B-receptor lymphocyte, macrophage, T-helper (T-suppressor), as well as humoral antigen (bacteria, virus, protein, polysaccharide and others). The interaction process takes place in following sequence:

· macrophage phagocytoses the antigen and brings determinants to the surface;

· influences B-lymphocyte receptors with antigenic determinants;

· affects the T-helper and T-suppressor receptors with the same determinants.

The influence of an antigenic stimulus on a B lymphocyte is not enough for its blast transformation. This occurs only after the activation of the T helper cell and the release of 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 proliferation of the immunoblast, a clone of cells is formed, among which are distinguished:

· In mind;

Plasmocytes, which are effector cells of humoral immunity.

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

However, antigen-activated B lymphocytes are capable of synthesizing small amounts of nonspecific immunoglobulins themselves. Under the influence of T-helper lymphokines, firstly, the transformation of B-lymphocytes into plasmacytes occurs, secondly, the synthesis of nonspecific immunoglobulins is replaced by specific ones, and thirdly, the synthesis and release of immunoglobulins by plasmacytes is stimulated. T-suppressors are activated by the same antigens and secrete lymphokine, which inhibits the formation of plasma cells and their synthesis of immunoglobulins until they completely stop. 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 immune reaction for antigen. It can be caused by both preferential stimulation of T-suppressor antigens and inhibition of T-helper function or death of T-helper cells (for example, in AIDS).

Human blood consists of different elements, each of which performs its own function. Its composition changes depending on a person’s age and health status, so doctors often prescribe a blood test to assess the body’s functioning and make a diagnosis. Leukocyte blood count is a highly informative indicator laboratory research liquid connective tissue.

Leukocytes are white blood cells that protect the child’s body from infections and viruses

What is the leukocyte formula and what indicators are studied in it?

Leukocytes are white blood bodies, which are involved in the process of protecting the body from pathogenic factors and microorganisms. There are several types of leukocytes. The number of blood cells changes as a person grows older and as their health changes. The leukocyte formula (leukogram) is the ratio of various white blood particles to their total number in percentage terms.

A change in one of the indicators (types of white cells) of the leukocyte formula indicates the activation of pathological processes or disruption of the body systems. In this case, it is possible to increase the number of one type of leukocyte and decrease the content of another. Only a comprehensive analysis of the elements shows a reliable picture of a person’s health status.

In what cases is analysis prescribed?

Leukogram is widely used in medical practice. The quantitative content of various leukocytes in the blood allows you to clarify the preliminary diagnosis, determine the causative agent of the disease, assess the severity of the disease, check the effectiveness of prescribed therapy, and monitor the general condition of the body. Testing is prescribed for children in the following situations:

• preventive examination of the child;
• at birth and 1 year of age;
• before vaccination;
• in case of contacting medical institution with complaints;
• exacerbation of chronic diseases;
• before surgery;
• upon admission to hospital.

Blood sampling for a baby's leukogram

Leukogram norms for children of different ages in the table

Quantitative content of leukocytes in the blood of children of different ages is different. For example, in newborns the number of neutrophils is greater than lymphocytes (we recommend reading:). During the year, their ratio constantly changes. There is such a thing as a cross-section of the leukocyte formula in children - an equal number of lymphocytes and neutrophils.

The reason for this phenomenon is the formation of immunity. A sharp change in the content of white cells in the blood occurs on the seventh day of the baby’s life, at 4 and 6 years. At six years of age, the quantitative content of all types of leukocytes in children is approximately the same as in adults. Deviation from the norm in adolescents is possible during the period of hormonal changes.

Table of leukogram norms in children:

Age	Index, %
	Neutrophils		Basophils	Eosinophils	Lymphocytes	Monocytes
	P*	WITH**
Newborn	3-12	47-70	up to 0.5	1-6	15-35	3-12
1-7 days	5-10	30-55	up to 1	1-3	20-45	3-5
up to 1 month	1-5	20-25	up to 1	0,5-3	65-70	3-6
1-12 months	2-4	20-28	up to 0.5	1-5	45-70	4-10
1-3 years	1-4	32-52	0-1	1-4	35-50	10-12
4-6 years	1-4	36-52	0-1	1-4	33-50	10-12
Over 6 years old	1-6	50-72	0-1	0,5-5	20-37	3-11

P* - rod-nuclear, C** - segmented.

Explanation: shift the formula to the right or left

Only a specialist can correctly decipher the leukocyte formula of blood in children, since when describing the results of the analysis, not only the content of individual types of leukocytes is taken into account, but also the shift of the formula to the right or left.

A shift in the leukocyte formula indicates the predominance of one group of neutrophils over others. Interpretation of indicators is based on the leukogram and calculation of the shift index (SI) using the formula: SI = (myelocytes + band neutrophils) / segmented neutrophils. With a shift to the left, there is an increase in band neutrophils and the appearance of myelocytes. The predominance of the number of segmented leukocytes indicates a shift to the right. A shift to the left indicates the following pathologies:

• inflammatory processes;
• poisoning by toxins;
• purulent lesions;
• oncological diseases;
• internal bleeding;
• acidosis;
• physical stress.

Rightward shift may occur in 20% healthy people, but sometimes it indicates pathologies of the liver and kidneys, acute shortage vitamin B12 and folic acid, benign tumors. Such deviations are also observed during radiation sickness and after blood transfusion.

Possible reasons for deviations from the norm

A blood test with leukemia is performed in the laboratory. A specialist studies the composition of blood using a microscope. In order to get a reliable result, you need to donate blood on an empty stomach. When studying the leukogram, both excess and decrease in the number of leukocytes are taken into account.

If the leukocyte blood count deviates from the norm, the doctor may prescribe a number of additional tests

A breakdown of the indicators is provided in the table:

If deviations from the norm are detected, the specialist may prescribe additional tests. In some cases, the leukocyte formula is rechecked. Decoding of children's indicators is carried out taking into account the patient's age and the possibility of crossover of the formula.