Their main function is to ensure the body’s protective response to irritants (pathogenic microorganisms, histamines, parasites, etc.). Lymphocytes are also responsible for the “immune memory” of the body. Unlike other types of leukocytes, they no longer fight with external agents, but with internal ones, for example, with their own affected cells (mutating, cancerous, viral, etc.).

Types of lymphocytes and their function

Once in the blood, lymphocytes live in their “basic” form for a couple of days, then the body’s glands distribute them into various functional subtypes, which allows lymphocytes to more accurately respond to pathogenic microorganisms.

T lymphocytes

The thymus gland (thymus) is responsible for the creation of T-lymphocytes from 80% of the basic ones. After “training,” T-lymphocytes, in turn, are divided into subtypes:

• T-helpers (helpers);
• T-killers (killers);
• T-suppressors (limiters).

Assassins are naturally trained to attack foreign agents and eliminate them. Helpers produce special components that support and improve the function of killer cells. Suppressors literally limit the immune response to invasion to prevent the active breakdown of healthy cells in the body.

B lymphocytes

From the basic set, up to 15% of white cells become B lymphocytes. They are considered one of the most important immune cells. It is enough for them to encounter a foreign agent (bacterium, histamine, fungus, virus, etc.) once in order to forever remember it and the way to fight it, which makes the immune response in the future faster and more accurate. Thanks to the adaptation function of B lymphocytes, immune resistance appears for life and also increases the effectiveness of vaccination.

NK lymphocytes

Naturalkiller (NK) is translated from English as “natural killers,” which most accurately corresponds to the purpose of these agents. Only 5% of basic lymphocytes degenerate into NK lymphocytes. This subspecies is entirely responsible for eliminating its own cells if they form markers of viral or cancer damage.

Indications for analysis

Lymphocyte analysis is carried out as part of a clinical (general) blood test with a leukocyte formula. It is prescribed for the diagnosis of the following pathologies:

• general inflammatory processes in acute and chronic form;
• autoimmune diseases;
• infectious, viral or fungal infections;
• suppuration and sepsis;
• internal bleeding;
• oncology;
• allergic reaction;
• pathological course of pregnancy;
• diseases of the hematopoietic and circulatory system;
• pathologies of the lymphatic system;
• radiation sickness;
• monitoring the effectiveness of treatment.

Norm of lymphocytes

White cells are assessed in the same way as leukocytes, based on absolute (LYM#) and relative (LYM%) indicators.

If abnormal values ​​are detected, additional tests are prescribed that make it possible to accurately determine the number of lymphocyte subtypes. Typically, such a need arises to assess the activity of the immune process, response and memory.

Lymphocytes are increased (lymphocytosis)

As a result of the analysis, an excess of the norm of lymphocytes established by age and individual physiological indicators may be revealed. This deviation is called lymphocytosis and indicates the following:

• there are inflammatory or infectious processes, viral, bacterial pathologies in the body;
• in the pathogenesis of the disease there is a peak or transition to an early stage of recovery;
• the presence of a disease that, as a rule, occurs once in a lifetime and develops lasting immunity (chickenpox, mononucleosis, rubella, measles and others);
• poisoning of the body with heavy metals (lead), chemical components (arsenic, tetrachloroethane), and some medications. The level of lymphocytes in this case will allow us to assess the size and danger of the dose taken;
• oncological processes.

Lymphocytes are low (lymphopenia)

The number of lymphocytes can decrease in three cases:

The body released lymphocytes to eliminate the foreign agent, the white cells died, and the analysis was carried out precisely at this moment (even before the maturation of the new “defenders”). This could happen early in the disease process (before the peak). Sometimes low lymphocytes also cause “long-term” pathologies, such as AIDS, HIV and tuberculosis.

Treatment with certain groups of drugs, for example, corticosteroids, cytostatics, etc.

• The organs and systems responsible for hematopoiesis and specifically for the formation of lymphocytes were affected. In this case, the cause of low lymphocyte levels may be:

  • all types of anemia (iron deficiency, folate deficiency, aplastic);
  • blood diseases (leukemia);
  • lymphosarcoma, lymphogranulomatosis;
  • cancer tumors and methods of their treatment (chemo- and radiation therapy);
  • Itsenko-Cushing's disease.

A low level of lymphocytes often indicates serious and even incurable pathologies.

The analysis is deciphered by a hematologist, in consultation with a diagnostician, infectious disease specialist and oncologist. The sooner the analysis is carried out, the greater the likelihood of identifying the disease at an early stage and providing effective treatment for the patient.

Preparation for the procedure

Preparation for analysis involves the following steps:

• Before donating blood, you should not eat food for 10-12 hours. Therefore, the analysis is prescribed in the morning (usually before 12 o’clock), except in cases where the level of lymphocytes needs to be monitored regularly. In infants, the procedure is carried out 1.5-2 hours after feeding.
• You can drink water only without gas, and abstain from it 1-2 hours before the procedure. Juices, hot drinks, soda, etc. prohibited.
• 24 hours before the procedure, you must avoid alcohol, spicy and heavy foods, and 2 hours before you stop smoking or using nicotine substitutes.
• Before donating blood, you need to inform your doctor about taking medications and undergoing physiotherapeutic or other treatment courses. It is advisable to do the analysis before or 2 weeks after treatment.
• It is recommended to take a test (including a repeat test) in the laboratory of the hospital where further examination and treatment will take place.

For standard microscopic examination, capillary blood is taken from a finger or a vein. In newborns, blood can be collected from the heel.

If the laboratory uses modern counter-cytometers, then at least 5 ml of material is needed for the study. In this case, blood is drawn from a vein.

What can affect the result

• A nurse’s mistake during blood sampling, as well as violation of the rules for storing and transporting biomaterial;
• Laboratory assistant’s mistake when studying the material;
• Dishonesty of a patient who violated the rules for preparing for analysis;
• Any, even minor, stress or physical activity immediately before the test;
• Medical procedures performed on the eve of the procedure (radiography, physiotherapy, puncture, MRI, CT, massage, etc.);
• A sudden change in body position before donating blood can also give a false positive result;
• Menstruation in women. Doctors advise carrying out the test no earlier than 4 days after the end of menstrual bleeding;
• Pregnancy. The patient should warn the doctor about the early stages of pregnancy before taking blood.

T lymphocytes in the process of differentiation and proliferation, they form subpopulations that differ from each other in their functions: some perform regulatory, and others - effector functions. Regulators include T helper cells (Th)(from the English helper) or assistants. Among them the following subpopulations are distinguished:

Th1 secrete cytokines (IL-2, IL-12, -interferon) under the influence of which the formation of effector cells is activated - T-killers, lymphocytes that carry out cellular immune reactions and stimulate immunity against viruses and intracellular bacteria.

Th 2 secrete IL-4, IL-5, IL-6 and stimulate B-lymphocytes, promoting the transformation of B-lymphocytes into plasma cells, antibody-producing cells (activate humoral immunity reactions). Antibodies are involved in protecting the body from bacteria, bacterial toxins, viruses and other pathogens.

T h 3 belong to regulatory cells: they regulate the functions of Th1 and Th2, secrete IL-10 (suppressor factor), TGF- (transforming growth factor-), regulating the development of both cellular and humoral immune responses.

Also known:

T-reg(from the English T-regulator) or T regulatory cells –cells  CD4 + CD25 + . They contain Foxp3 protein, which suppresses the activity of other T cells;

T s (from the English T-suppressor) or T -suppressors inhibit too strong and too prolonged immunological reactions.

Effector T lymphocytes include:

Tk (from English T-killer) or T-killers (killers) – lymphocytes that destroy malignant, transplanted, mutant, modified, aging, virus- and bacteria-infected cells.

T-effectors of inflammation – carry out cellular immune reactions of inflammation.

From the general population of T-lymphocytes, they also isolate Immunological memory T cells are long-lived Th and Tk, descendants of cells that encountered Ag and retained receptors for them. These long-lived antigen-stimulated cells provide a faster and more pronounced immune response when encountering the same antigen again - secondary immune response.

29.6. BCR – B-lymphocyte receptor

B cell receptor- BCR (from EnglishB – cellularreceptor) capable of recognizing unprocessed antigen. B lymphocytes use immunoglobulin bound on the cell surface as a receptor. The specificity of this receptor is the same as the specificity of the immunoglobulin that lymphocytes secrete after their activation. B lymphocytes are capable of recognizing the following antigens, presented in soluble form:

proteins (both conformational determinants and determinants formed after

denaturation)

nucleic acids

polysaccharides

some lipids

small molecular weight compounds (haptens)

Mature B lymphocytes, which undergo all stages of maturation in the bone marrow, express so-called membrane immunoglobulins on the membrane: IgMAndIgD. The first cellular receptor to appear on a B lymphocyte is IgM. Unlike the pentameric IgM secreted by the plasma cell in the form of antibodies, receptor immunoglobulin is a monomer, so it is often referred to as mIgM. It is always found on the membrane of the B lymphocyte. The main function of the B-cell receptor is to bind to antigen and conduct an activation signal into the B-lymphocyte cell. To do this, the IgM receptor has a short cytoplasmic tail involved in interaction with the complex, which carries out the activation signal (signals about the appearance of the antigen and the need for an immune response to it) into the cell. The complex is represented by four transmembrane polypeptides (Fig. 29.6-1).

The cells of the immune system include lymphocytes, macrophages and other antigen-presenting cells(A - cells, from the English accessory - auxiliary), as well as the so-called third population of cells(i.e. cells that do not have the main surface markers of T- and B-lymphocytes, A-cells).

According to their functional properties, all immunocompetent cells are divided into effector and regulatory. The interaction of cells in the immune response is carried out with the help of humoral mediators - cytokines. The main cells of the immune system are T and B lymphocytes.

Lymphocytes.

In the body, lymphocytes constantly recirculate between areas of accumulation of lymphoid tissue. The location of lymphocytes in lymphoid organs and their migration along the bloodstream and lymphatic beds are strictly ordered and associated with the functions of various subpopulations.

Lymphocytes have common morphological characteristics, but their functions, surface CD (from cluster differentiation) markers, and individual (clonal) origin are different.

Based on the presence of surface CD markers, lymphocytes are divided into functionally different populations and subpopulations, primarily T- (thymus dependent, having undergone primary differentiation in the thymus) lymphocytes and B - (bursa-dependent, having undergone maturation in the bursa of Fabricius in birds or its analogues in mammals) lymphocytes.

T-lymphocytes.

Localization.

Usually localized in the so-called T-dependent zones of peripheral lymphoid organs (periarticular in the white pulp of the spleen and paracortical zones of the lymph nodes).

Functions.

T lymphocytes recognize the antigen processed and presented on the surface of antigen-presenting (A) cells. They are responsible for cellular immunity, cell-type immune reactions. Distinct subpopulations help B lymphocytes respond to T-dependent antigens production of antibodies.

Origin and maturation.

The ancestor of all blood cells, including lymphocytes, is a single bone marrow stem cell. It generates two types of progenitor cells - the lymphoid stem cell and the red blood cell precursor, from which the progenitor cells of leukocytes and macrophages also originate.

The formation and maturation of immunocompetent cells occurs in the central organs of the immune system (for T-lymphocytes, in the thymus). Precursor cells of T lymphocytes enter the thymus, where pre-T cells (thymocytes) mature, proliferate and differentiate into separate subclasses as a result of interaction with epithelial and dendritic cells of the stroma and the influence of hormone-like polypeptide factors secreted by epithelial cells of the thymus (alpha1- thymosin, thymopoietin, thymulin, etc.).

During differentiation, T lymphocytes acquire a specific set of membrane CD markers. T cells are divided into subpopulations according to their function and CD marker profile.

T lymphocytes recognize antigens using two types of membrane glycoproteins - T cell receptors(family of Ig-like molecules) and CD3, non-covalently linked to each other. Their receptors, unlike antibodies and B-lymphocyte receptors, do not recognize freely circulating antigens. They recognize peptide fragments presented to them by A-cells through a complex of foreign substances with the corresponding protein of the major histocompatibility system of classes 1 and 2.

There are three main groups of T-lymphocytes: helpers (activators), effectors, regulators.

The first group is assistants ( activators) , which include T-helpers1, T-helpers2, inducers of T-helpers, inducers of T-suppressors.

1. T-helpers1 carry receptors CD4 (as well as T-helper2) and CD44, are responsible for maturation T-cytotoxic lymphocytes (T-killers), activate T-helpers2 and the cytotoxic function of macrophages, secrete IL-2, IL-3 and other cytokines.

2. T-helpers2 have common CD4 and specific CD28 receptors for helpers, ensure proliferation and differentiation of B lymphocytes into antibody-producing (plasma) cells, antibody synthesis, inhibit the function of T helper1, secrete IL-4, IL-5 and IL-6.

3. T-helper inducers carry CD29 and are responsible for the expression of HLA class 2 antigens on macrophages and other A cells.

4. Inducers of T-suppressors carry a CD45 specific receptor, are responsible for the secretion of IL-1 by macrophages, activation of the differentiation of T-suppressor precursors.

The second group is T-effectors. It includes only one subpopulation.

5. T-cytotoxic lymphocytes (T-killers). They have a specific CD8 receptor and lyse target cells carrying foreign antigens or altered autoantigens (transplant, tumor, virus, etc.). CTLs recognize a foreign epitope of a viral or tumor antigen in complex with an HLA class 1 molecule in the plasma membrane of the target cell.

The third group is T-cells-regulators. Represented by two main subpopulations.

6. T-suppressors are important in the regulation of immunity, providing suppression of the functions of T-helper 1 and 2, B-lymphocytes. They have receptors CD11, CD8. The group is functionally heterogeneous. Their activation occurs as a result of direct stimulation by antigen without significant participation of the major histocompatibility system.

7. T-consupressors. They do not have CD4, CD8, they have a receptor for a special leukine. They help suppress the functions of T-suppressors, develop resistance of T-helpers to the effect of T-suppressors.

B lymphocytes.

There are several subtypes of B lymphocytes. The main function of B cells is effector participation in humoral immune reactions, differentiation as a result of antigenic stimulation into plasma cells that produce antibodies.

The formation of B cells in the fetus occurs in the liver, and subsequently in the bone marrow. The process of B cell maturation occurs in two stages - antigen - independent and antigen - dependent.

Antigen-independent phase. In the process of maturation, the B lymphocyte goes through the stage pre-B-lymphocyte- an actively proliferating cell having cytoplasmic H-chains of type C mu (i.e. IgM). Next stage- immature B lymphocyte characterized by the appearance of membrane (receptor) IgM on the surface. The final stage of antigen-independent differentiation is the formation mature B lymphocyte, which can have two membrane receptors with the same antigen specificity (isotype) - IgM and IgD. Mature B lymphocytes leave the bone marrow and populate the spleen, lymph nodes and other accumulations of lymphoid tissue, where their development is delayed until they meet “their” antigen, i.e. before antigen-dependent differentiation occurs.

Antigen-dependent differentiation involves the activation, proliferation, and differentiation of B cells into plasma cells and memory B cells. Activation occurs in various ways, depending on the properties of antigens and the participation of other cells (macrophages, T-helpers). Most antigens that induce antibody synthesis require the participation of T cells to induce an immune response. Thymus-dependent antigens. Thymus-independent antigens(LPS, high molecular weight synthetic polymers) are able to stimulate the synthesis of antibodies without the help of T lymphocytes.

The B lymphocyte, using its immunoglobulin receptors, recognizes and binds the antigen. Simultaneously with the B cell, the antigen, presented by the macrophage, is recognized by the T helper (T helper 2), which is activated and begins to synthesize growth and differentiation factors. Activated by these factors, the B lymphocyte undergoes a series of divisions and simultaneously differentiates into plasma cells that produce antibodies.

The pathways of B cell activation and cell cooperation in the immune response to various antigens and with the participation of B cell populations with and without the Lyb5 antigen differ. Activation of B lymphocytes can be carried out:

T-dependent antigen with the participation of MHC class 2 T-helper proteins;

T-independent antigen containing mitogenic components;

Polyclonal activator (LPS);

Anti-mu immunoglobulins;

T-independent antigen that does not have a mitogenic component.

Cooperation of cells in the immune response.

In the formation of the immune response, all parts of the immune system are included - the macrophage system, T- and B-lymphocytes, complement, interferons and the major histocompatibility system.

Briefly, the following stages can be distinguished.

1. Uptake and processing of antigen by a macrophage.

2. Presentation of the processed antigen by the macrophage using the major histocompatibility system class 2 protein to T helper cells.

3. Antigen recognition by T-helpers and their activation.

4. Antigen recognition and activation of B lymphocytes.

5. Differentiation of B lymphocytes into plasma cells, synthesis of antibodies.

6. Interaction of antibodies with antigen, activation of complement systems and macrophages, interferons.

7. Presentation of foreign antigens to T-killers with the participation of MHC class 1 proteins, destruction of cells infected with foreign antigens by T-killers.

8. Induction of T- and B-immune memory cells capable of specifically recognizing the antigen and participating in the secondary immune response (antigen-stimulated lymphocytes).

Immune memory cells. Maintaining long-lived and metabolically inactive memory cells recirculating in the body is the basis for the long-term preservation of acquired immunity. The state of immune memory is determined not only by the lifespan of T- and B-memory cells, but also by their antigenic stimulation. Long-term preservation of antigens in the body is ensured by dendritic cells (antigen depot), which store them on their surface.

Dendritic cells- a population of growing cells of lymphoid tissue of bone marrow (monocyte) origin, presenting antigenic peptides to T lymphocytes and retaining antigens on their surface. These include follicular process cells of the lymph nodes and spleen, Langerhans cells of the skin and respiratory tract, M-cells of the lymphatic follicles of the digestive tract, and dendritic epithelial cells of the thymus.

CD antigens.

Cluster differentiation of surface molecules (antigens) of cells, primarily leukocytes, is making great progress. To date, CD antigens are not abstract markers, but functionally significant receptors, domains and determinants for the cell, including those that are not initially specific for leukocytes.

The most important differentiation antigens of T lymphocytes people are as follows.

1. CD2 is an antigen characteristic of T-lymphocytes, thymocytes, NK cells. It is identical to the receptor of sheep erythrocytes and ensures the formation of rosettes with them (method for determining T cells).

2. CD3 - necessary for the functioning of any T-cell receptors (TCRs). All subclasses of T lymphocytes have CD3 molecules. The interaction of TCR-CD3 (it consists of 5 subunits) with the antigen-presenting MHC class 1 or 2 molecule determines the nature and implementation of the immune response.

3. CD4. These receptors have T-helpers 1 and 2 and T-inducers. They are a coreceptor (binding site) for the determinants of MHC class 2 protein molecules. It is a specific receptor for the envelope proteins of the human immunodeficiency virus HIV-1 (gp120) and HIV-2.

4. CD8. The population of CD8+ T lymphocytes includes cytotoxic and suppressor cells. Upon contact with a target cell, CD8 acts as a coreceptor for HLA class 1 proteins.

Differentiation receptors of B-lymphocytes.

There can be up to 150 thousand receptors on the surface of B lymphocytes, among which more than 40 types with different functions have been described. Among them are receptors for the Fc component of immunoglobulins, for the C3 component of complement, antigen-specific Ig receptors, receptors for various growth and differentiation factors.

Brief description of methods for assessing T- and B-lymphocytes.

To identify B-lymphocytes, the method of rosette formation with erythrocytes treated with antibodies and complement (EAC-ROC), spontaneous rosette formation with mouse erythrocytes, the method of fluorescent antibodies with monoclonal antibodies (MAbs) to B-cell receptors (CD78, CD79a,b, membrane Ig) are used ).

To quantify T-lymphocytes, the method of spontaneous rosette formation with sheep erythrocytes (E-ROC) is used, to identify subpopulations (for example, T-helpers and T-suppressors) - an immunofluorescent method with mAbs to CD receptors, to determine T-killers - cytotoxicity tests .

The functional activity of T and B cells can be assessed in the response of blast transformation of lymphocytes (RBTL) to various T and B mitogens.

Sensitized T-lymphocytes involved in delayed-type hypersensitivity reactions (DTH) can be determined by the release of one of the cytokines - MIF (migration inhibitory factor) in the reaction of inhibition of leukocyte (lymphocyte) migration - RTML. Read more about methods for assessing the immune system in lectures on clinical immunology.

One of the features of immunocompetent cells, especially T-lymphocytes, is the ability to produce large amounts of soluble substances - cytokines (interleukins) that perform regulatory functions. They ensure the coordinated operation of all systems and factors of the immune system; thanks to direct and feedback connections between various systems and subpopulations of cells, they ensure stable self-regulation of the immune system. Their determination provides additional insight into the state of the immune system.

Each “family” of leukocyte cells is interesting in its own way, but lymphocytes are difficult not to notice and not to take into account. These cells are heterogeneous within their species. Receiving specialization through “training” in the thymus gland (thymus, T-lymphocytes), they acquire high specificity for certain antigens, turn into killers, killing the enemy at the first stage, or assistants (helpers), commanding other populations of lymphocytes at all stages , accelerating or suppressing the immune response. T-lymphocytes remind B-cells, also lymphocytes, concentrated in lymphoid tissue and waiting for a command, that it is time to start producing antibodies, because the body cannot cope. Later, they themselves will take part in suppressing this reaction if the need for antibodies no longer exists.

Basic properties and functions, types of lymphocytes

Lymphocytes (LYM) are rightly called the main figure of the human immune system. They, maintaining the genetic constancy of homeostasis (internal environment), are able to recognize “theirs” and “theirs” by the signs known to them. In the human body they solve a number of important problems:

• Antibodies are synthesized.
• They lyse foreign cells.
• They play a major role in transplant rejection, although this role can hardly be called positive.
• Provides immune memory.
• They are engaged in the destruction of their own defective mutant cells.
• They provide sensitization (increased sensitivity, which is also not very beneficial for the body).

The lymphocyte community has two populations: T cells, which provide cellular immunity, and B cells, which are entrusted with the function of providing humoral immunity; they implement the immune response through the synthesis of immunoglobulins. Each population is divided into varieties depending on its purpose. All T lymphocytes within a species are morphologically uniform, but differ in the properties of surface receptors.

The T cell population includes:

1. T-helpers (helpers) - they are omnipresent.
2. T-suppressors (suppress the reaction).
3. T-killers (killer lymphocytes).
4. T-effectors (accelerators, amplifiers).
5. Immunological memory cells from T-lymphocytes, if the process ended at the level of cellular immunity.

The following types are distinguished in the B-population:

• Plasma cells that enter the peripheral blood only in extreme situations (irritation of lymphoid tissue).
• B-killers.
• B-helpers.
• B-suppressors.
• Memory cells from B-lymphocytes, if the process has passed the stage of antibody formation.

In addition, in parallel there is an interesting population of lymphocytes, which are called zero (neither T nor B). It is believed that they turn into T- or B-lymphocytes and become natural killers (NK, N-killers). These cells are produced by proteins that have the unique ability to “drill” pores located in the membranes of “enemy” cells, for which NK is called perforins. Natural killer cells, meanwhile, should not be confused with killer T cells; they have different markers (receptors). NKs, unlike T-killers, recognize and destroy foreign proteins without developing a specific immune reaction.

We can talk about them for a long time and a lot

The norm of lymphocytes in the blood is 18–40% of all leukocyte cells, which corresponds to absolute values ​​in the range of 1.2–3.5 x 10 9 /l.

As for the norm in women, they have more of these cells physiologically, therefore the increased content of lymphocytes in the blood (up to 50 - 55%) associated with menstruation or pregnancy is not considered a pathology. In addition to gender and age, the number of lymphocytes depends on the psycho-emotional state of a person, nutrition, environmental temperature, in a word, these cells respond to many external and internal factors, but a change in level of more than 15% is clinically significant.

The norm in children has a wider range of values ​​– 30-70%, this is explained by the fact that the child’s body is just getting acquainted with the outside world and forming its own immunity. The thymus gland, spleen, lymphatic system and other organs involved in the immune response function much more actively in children than in an adult (the thymus disappears altogether in old age, and its function is taken over by other organs consisting of lymphoid tissue).

Table: norms of lymphocytes and other leukocytes in children by age

It should be noted that the number of cells contained in the peripheral blood is a small fraction of the circulating fund, and the bulk of them are represented by T-lymphocytes, which, like all “relatives”, originated from a stem cell, separated from the community in the bone brain and went to the thymus for learning, in order to then carry out cellular immunity.

B cells also go through a considerable development path from a stem cell, through immature forms. Some of them die (apoptosis), and some of the immature forms, called “naive”, migrate to the lymphatic organs for differentiation, turning into plasma cells and mature full-fledged B-lymphocytes, which will permanently move through the bone marrow, lymphatic system, spleen and only a tiny fraction of them will go into the peripheral blood. Lymphocytes enter the lymphoid tissue through capillary venules, and enter the blood through the lymphatic tract.

There are few B-lymphocytes in the peripheral blood; they are antibody-formers, so in most cases they wait for the command to begin humoral immunity from those populations that are everywhere and know everything - lymphocytes called helpers or helpers.

Lymphocytes live differently: some live for about a month, others for about a year, and others persist for a very long time or even for life, along with the information received from an encounter with a foreign agent (memory cell). Memory cells are located in different places, they are widespread, very mobile and long-lived, which provides long-term immunization or lifelong immunity.

All the complex relationships within a species, interaction with antigens that have entered the body, the participation of other components of the immune system, without which the destruction of foreign substances would become impossible, is a complex multi-stage process that is practically incomprehensible to the average person, so we will simply omit it.

Don't panic

An increased level of lymphocytes in the blood is called. An increase in the number of cells above normal in percentage terms implies relative lymphocytosis, in absolute values, respectively, absolute. Thus:

Elevated lymphocytes in an adult are said to occur if their content exceeds the upper limit of normal ( 4.00 x 10 9 /l). In children, there is a certain (not very strict) gradation by age: in infants and preschoolers, “a lot of lymphocytes” is taken to mean from 9.00 x 10 9 /l and higher, and for older children the upper limit decreases to 8.00 x 10 9 / l.

Discovered in some An increase in lymphocytes in an adult healthy person should not be frightening with its numbers if:

Reaction or sign of a new pathology?

Lymphocytes are full-fledged diagnostic indicators in a general blood test, so their increase can also tell the doctor something, for example, a higher than normal number of lymphocytes is detected during inflammatory processes, and this does not happen at the initial stage of the disease and, especially, not during the incubation period . Lymphocytes are elevated during the transition phase of the acute process to subacute or chronic, and also when the inflammation subsides and the process begins to subside, which is to some extent an encouraging sign.

In the analyzes of some people, such phenomena may sometimes be observed when lymphocytes are increased and decreased. Similar changes are typical for:

• Connective tissue diseases (rheumatoid arthritis);
• Some viral (ARVI, hepatitis, HIV), bacterial and fungal infections;
• Endocrine disorders (myxedema, thyrotoxicosis, Addison's disease, etc.);
• Diseases of the central nervous system;
• Side effect of drugs.

Very high values ​​(severe lymphocytosis) are observed in quite serious diseases:

1. Chronic lymphocytic leukemia;
2. Hyperplastic processes of the lymphatic system (Waldenström's macroglobulinemia)

Obviously, many of these diseases are childhood infections that lymphocytes are required to remember. A similar situation occurs during vaccination; memory cells will store information about someone else’s antigenic structure for many years, so that in the event of a second encounter they will give a decisive rebuff.

Unfortunately, not all infections provide lasting lifelong immunity and not all diseases can be defeated with vaccination, for example, vaccines have not yet been found for syphilis and malaria, but the prevention of tuberculosis and diphtheria begins literally from birth, due to which these diseases are becoming less common and less often.

Reduced lymphocytes are more dangerous

This happens in the following pathological conditions:

1. Severe infectious diseases;
2. Secondary immunodeficiency;
3. Pancytopenia (decrease in all blood cells);
4. Severe pathological processes of viral origin;
5. Certain chronic liver diseases;
6. Radioactive exposure over a long period of time;
7. Use of corticosteroid drugs;
8. Terminal stage of malignant tumors;
9. Kidney diseases with insufficient function;
10. Insufficiency and circulatory disorders.

Obviously, if lymphocytes are low, then suspicion will quickly fall on a serious pathology.

Low lymphocytes in a child especially cause a lot of concern and questions. However, in such cases, the doctor will first of all think about the high allergic status of the small organism or a congenital form of immunodeficiency, and then he will look for the listed pathology if the first options are not confirmed.

The body's immune response to an antigenic stimulus, in addition to lymphocytes, is realized by other factors: various populations of cellular elements (macrophages, eosinophils and even representatives of the erythrocyte unit - the erythrocytes themselves), bone marrow mediators, and the complement system. The relationship between them is very complex and not fully understood, for example, lymphocytes are helped to produce antibodies by a certain “silent” population, which for the time being is blocked by the synthesis of its own antibodies, and only a special signal at the peak of the immune response forces the cells to start working... All this forces the extra Let us remember that sometimes we don’t even realize our abilities. Perhaps the presence of hidden potential sometimes allows one to survive in seemingly incredible conditions. And in an attempt to defeat some kind of infection (be it the flu, or something worse), we hardly think about some lymphocytes and the role that these small, invisible cells will play for a big victory.

Video: B and T lymphocytes - structure and functions

A well-functioning immune system of a healthy person is able to cope with most external and internal threats. Lymphocytes are blood cells that are the first to enter the battle for the purity of the body. Viruses, bacteria, fungus are the daily concern of the immune system. Moreover lymphocyte functions are not limited to detecting external enemies.

Any damaged or defective cells of one's own tissues must also be detected and destroyed.

Functions of lymphocytes in human blood

The main performers in the work of immunity in humans are colorless blood cells - leukocytes. Each variety fulfills its function, most important of which are allocated specifically to lymphocytes. Their number relative to other leukocytes in the blood sometimes exceeds 30% . Functions of lymphocytes are quite diverse and accompany the entire immune process from beginning to end.

In essence, lymphocytes detect any fragments that do not correspond to the body genetically, give a signal to start a battle with foreign objects, control its entire course, actively participate in the destruction of “enemies” and end the battle after victory. As conscientious guards, they remember each violator by sight, which gives the body the opportunity to act faster and more efficiently at the next meeting. This is how living beings manifest a property called immunity.

The most important lymphocyte functions:

1. Detection of viruses, bacteria, other harmful microorganisms, as well as any abnormal cells of one’s own body (old, damaged, infected, mutated).
2. A message to the immune system about the “invasion” and the type of antigen.
3. Direct destruction of pathogenic microbes, production of antibodies.
4. Management of the entire process using special “signal substances”.
5. Winding down the active phase of the “battle” and managing the cleanup after the battle.
6. Preservation of memory of each defeated microorganism for subsequent rapid recognition.

The production of such immune soldiers occurs in the red bone marrow; they have different structures and properties. It is most convenient to distinguish immune lymphocytes by their functions in defense mechanisms:

• B lymphocytes recognize harmful inclusions and synthesize antibodies;
• T-lymphocytes activate and inhibit immune processes, directly destroy antigens;
• NK lymphocytes perform a function control over the tissues of the native organism, are capable of killing mutated, old, degenerated cells.

Based on their size and structure, they are distinguished between large granular (NK) and small (T, B) lymphocytes. Each type of lymphocyte has its own characteristics and important functions, which are worth considering in more detail.

B lymphocytes

The distinctive features include the fact that for normal functioning the body requires not just young lymphocytes in large quantities, but hardened, mature soldiers.

Maturation and education of T cells take place in the intestines, appendix, and tonsils. In these "training camps" young bodies are trained to perform three important functions:

1. “Naive lymphocytes” are young, not activated blood cells that have no experience of encountering foreign substances, and therefore do not have strict specificity. They are able to show a limited reaction to several antigens. Activated after meeting an antigen, they are sent to the spleen or bone marrow for re-maturation and rapid cloning of their own kind. After ripening, plasma cells very quickly grow from them, producing antibodies exclusively to this type of pathogen.
2. Mature plasma cells, strictly speaking, are no longer lymphocytes, but factories for the production of specific soluble antibodies. They live only a few days, eliminating themselves as soon as the threat that caused the defensive reaction disappears. Some of them will later be “preserved” and will again become small lymphocytes with memory of the antigen.
3. Activated B-lymphocytes, with the assistance of T-lymphocytes, can become repositories of the memory of a defeated foreign agent; they live for decades, perform a function transmitting information to their “descendants”, providing long-term immunity, accelerating the body’s response to meeting the same type of aggressive influence.

B cells are very specific. Each of them is activated only when encountering a certain type of threat (a strain of a virus, a type of bacteria or protozoa, a protein, a chemical). The lymphocyte will not react to pathogens of a different nature. Thus, the main function of B lymphocytes is to provide humoral immunity and produce antibodies.

T lymphocytes

Young T-bodies are also produced by the bone marrow. This type of red blood cells undergoes the most stringent step-by-step selection, which rejects more than 90% of young cells. “Nurture” and selection occur in the thymus gland (thymus).

Note!The thymus is an organ that enters the phase of greatest development between 10 and 15 years, when its mass can reach 40 g. After 20 years, it begins to decrease. In old people, the thymus weighs the same as in babies, no more than 13 g. The working tissues of the gland after 50 years are replaced by fatty and connective tissue. Accordingly, the number of T cells decreases and the body’s defenses weaken.

As a result of the selection occurring in the thymus gland, T-lymphocytes are eliminated that are not capable of binding any foreign agent, as well as those that have detected a reaction to proteins of the native organism. The remaining ripened bodies are considered suitable and are scattered throughout the body. A huge number of T cells (about 70% of all lymphocytes) circulate in the bloodstream; their concentration is high in the lymph nodes and spleen.

Three types of mature T lymphocytes leave the thymus:

• T-helpers. They help perform functions B lymphocytes, other immune agents. They guide their actions during direct contact or give orders by releasing cytokines (signal substances).
• Killer T cells. Cytotoxic lymphocytes that directly destroy defective, infected, tumor, and any modified cells. Killer T cells are also responsible for the rejection of foreign tissue upon implantation.
• T-suppressors. Execute important function supervision of the activity of B lymphocytes. Slow down or stop the immune response, if necessary. Their immediate responsibility is to prevent autoimmune reactions, when protective bodies mistake their cells for hostile ones and begin to attack them.

T-lymphocytes have the main properties: regulate the speed of the protective reaction, its duration, serve as an obligatory participant in certain transformations and provide cellular immunity.

NK lymphocytes

Unlike small forms, NK cells (null lymphocytes) are larger and contain granules consisting of substances that destroy the membrane of the infected cell or destroy it entirely. The principle of defeating hostile inclusions is similar to the corresponding mechanism in T-killers, but is more powerful and does not have pronounced specificity.

NK lymphocytes do not undergo the ripening procedure in the lymphatic system; they are able to react to any antigens and kill formations that T lymphocytes are powerless against. For such unique qualities they are called “natural killers.” NK lymphocytes are the main killers of cancer cells. Increasing their number and increasing activity is one of the promising directions for the development of oncology.

Interesting! Lymphocytes carry large molecules that transmit genetic information throughout the body. The important function of these blood cells is not limited to protection, but extends to the regulation of tissue repair, growth, and differentiation.

When necessary, null lymphocytes can function as B or T cells, thus serving as universal soldiers of the immune system.

In the complex mechanism of immune processes, lymphocytes play a leading, regulatory role. Moreover, they carry out their work both through contact and at a distance, producing special chemicals. Recognizing these command signals, all links of the immune chain are coordinated into the process and ensure the purity and durability of the human body.