Determination of t-lymphocytes, what it is, application in diagnosis and treatment. How T-cells of the immune system work What is the biological significance of different types of T-lymphocytes

agammaglobulinemia(agammaglobulinemia; a- + gamma globulins + gr. haima blood; synonym: hypogammaglobulinemia, antibody deficiency syndrome) - the general name of a group of diseases characterized by the absence or a sharp decrease in the level of immunoglobulins in the blood serum;

autoantigens(auto- + antigens) - the body's own normal antigens, as well as antigens that arise under the influence of various biological and physico-chemical factors, in relation to which autoantibodies are formed;

autoimmune reaction- the body's immune response to autoantigens;

allergy (allergies; Greek allos other, different + Ergon action) - a state of altered reactivity of the organism in the form of an increase in its sensitivity to repeated exposure to any substances or to components of its own tissues; Allergy is based on an immune response that occurs with tissue damage;

active immunity immunity resulting from the body's immune response to the introduction of an antigen;

The main cells that carry out immune reactions are T- and B-lymphocytes (and derivatives of the latter - plasma cells), macrophages, as well as a number of cells interacting with them (mast cells, eosinophils, etc.).

Lymphocytes

The population of lymphocytes is functionally heterogeneous. There are three main types of lymphocytes: T-lymphocytes, B-lymphocytes and the so-called zero lymphocytes (0-cells). Lymphocytes develop from undifferentiated lymphoid bone marrow progenitors and, upon differentiation, acquire functional and morphological features (presence of markers, surface receptors) detected by immunological methods. 0-lymphocytes (null) are devoid of surface markers and are considered as a reserve population of undifferentiated lymphocytes.

T-lymphocytes- the most numerous population of lymphocytes, constituting 70-90% of blood lymphocytes. They differentiate in the thymus gland - thymus (hence their name), enter the blood and lymph and populate T-zones in the peripheral organs of the immune system - lymph nodes (deep part of the cortical substance), spleen (periarterial sheaths of lymphoid nodules), in single and multiple follicles of various organs, in which T-immunocytes (effector) and T-memory cells are formed under the influence of antigens. T-lymphocytes are characterized by the presence on the plasmalemma of special receptors that can specifically recognize and bind antigens. These receptors are products of immune response genes. T-lymphocytes provide cellular immunity, participate in the regulation of humoral immunity, carry out the production of cytokines under the action of antigens.

In the population of T-lymphocytes, several functional groups of cells are distinguished: cytotoxic lymphocytes (Tc), or T-killers(TK), T-helpers(Tx), T-suppressors(Ts). TK are involved in cellular immunity reactions, ensuring the destruction (lysis) of foreign cells and their own altered cells (for example, tumor cells). The receptors allow them to recognize the proteins of viruses and tumor cells on their surface. At the same time, the activation of Tc (killers) occurs under the influence of histocompatibility antigens on the surface of foreign cells.

In addition, T-lymphocytes are involved in the regulation of humoral immunity with the help of Tx and Tc. Tx stimulate the differentiation of B-lymphocytes, the formation of plasma cells from them and the production of immunoglobulins (Ig). Tx have surface receptors that bind to proteins on the plasmolemma of B cells and macrophages, stimulating Tx and macrophages to proliferate, produce interleukins (peptide hormones), and B cells to produce antibodies.

Thus, the main function of Tx is the recognition of foreign antigens (presented by macrophages), the secretion of interleukins that stimulate B-lymphocytes and other cells to participate in immune responses.

A decrease in the number of Tx in the blood leads to a weakening of the body's defense reactions (these individuals are more susceptible to infections). A sharp decrease in the number of Tx in persons infected with the AIDS virus was noted.

Tc are able to inhibit the activity of Tx, B-lymphocytes and plasma cells. They are involved in allergic reactions, hypersensitivity reactions. Tc suppress the differentiation of B-lymphocytes.

One of the main functions of T-lymphocytes is the production cytokines, which have a stimulating or inhibitory effect on the cells involved in the immune response (chemotactic factors, macrophage inhibitory factor - MIF, non-specific cytotoxic substances, etc.).

natural killers. Among the lymphocytes in the blood, in addition to the above-described Tc, which perform the function of killers, there are so-called natural killers (Hk, NK), which are also involved in cellular immunity. They form the first line of defense against foreign cells, act immediately, quickly destroying cells. NK in their own body destroy tumor cells and cells infected with the virus. Tc form a second line of defense, since it takes time for them to develop from inactive T-lymphocytes, so they come into action later than Hc. NK are large lymphocytes with a diameter of 12-15 microns, have a lobed nucleus and azurophilic granules (lysosomes) in the cytoplasm.

Development of t- and b-lymphocytes

The ancestor of all cells of the immune system is the hematopoietic stem cell (HSC). HSCs are localized in the embryonic period in the yolk sac, liver, and spleen. In the later period of embryogenesis, they appear in the bone marrow and continue to proliferate in postnatal life. HSCs in the bone marrow produce a lymphopoietic progenitor cell (lymphoid multipotent progenitor cell) that generates two types of cells: pre-T cells (progenitors of T cells) and pre-B cells (progenitors of B cells).

T-lymphocyte differentiation

Pre-T cells migrate from the bone marrow through the blood to the central organ of the immune system, the thymus gland. Even during the period of embryonic development, a microenvironment is created in the thymus gland, which is important for the differentiation of T-lymphocytes. In the formation of the microenvironment, a special role is assigned to the reticuloepithelial cells of this gland, which are capable of producing a number of biologically active substances. Pre-T cells migrating to the thymus acquire the ability to respond to microenvironmental stimuli. Pre-T cells in the thymus proliferate, transform into T-lymphocytes carrying characteristic membrane antigens (CD4+, CD8+). T-lymphocytes generate and “deliver” into the blood circulation and thymus-dependent zones of peripheral lymphoid organs of 3 types of lymphocytes: Tc, Tx and Tc. The "virgin" T-lymphocytes migrating from the thymus (virgile T-lymphocytes) are short-lived. Specific interaction with an antigen in peripheral lymphoid organs initiates the processes of their proliferation and differentiation into mature and long-lived cells (T-effector and T-memory cells), which make up the majority of recirculating T-lymphocytes.

Not all cells migrate from the thymus gland. Part of T-lymphocytes dies. There is an opinion that the cause of their death is the attachment of an antigen to an antigen-specific receptor. There are no foreign antigens in the thymus, so this mechanism can serve to remove T-lymphocytes that can react with the body's own structures, i.e. perform the function of protection against autoimmune reactions. The death of some lymphocytes is genetically programmed (apoptosis).

T cell differentiation antigens. In the process of differentiation of lymphocytes, specific membrane molecules of glycoproteins appear on their surface. Such molecules (antigens) can be detected using specific monoclonal antibodies. Monoclonal antibodies have been obtained that react with only one cell membrane antigen. Using a set of monoclonal antibodies, subpopulations of lymphocytes can be identified. There are sets of antibodies to differentiation antigens of human lymphocytes. Antibodies form relatively few groups (or "clusters"), each of which recognizes a single cell surface protein. A nomenclature of differentiation antigens of human leukocytes, detected by monoclonal antibodies, has been created. This CD nomenclature ( CD - cluster of differentiation- differentiation cluster) is based on groups of monoclonal antibodies that react with the same differentiation antigens.

Polyclonal antibodies to a number of differentiating antigens of human T-lymphocytes have been obtained. When determining the total population of T cells, monoclonal antibodies of CD specificities (CD2, CD3, CDS, CD6, CD7) can be used.

Differentiating antigens of T cells are known, which are characteristic either for certain stages of ontogeny or for subpopulations that differ in functional activity. So, CD1 is a marker of the early phase of T-cell maturation in the thymus. During the differentiation of thymocytes, CD4 and CD8 markers are simultaneously expressed on their surface. However, subsequently, the CD4 marker disappears from a part of the cells and remains only on the subpopulation that has ceased to express the CD8 antigen. Mature CD4+ cells are Th. The CD8 antigen is expressed on about ⅓ of peripheral T cells that mature from CD4+/CD8+ T lymphocytes. The subpopulation of CD8+ T cells includes cytotoxic and suppressor T lymphocytes. Antibodies to the CD4 and CD8 glycoproteins are widely used to distinguish and separate T cells into Tx and Tc, respectively.

In addition to differentiation antigens, specific markers of T-lymphocytes are known.

T-cell receptors for antigens are antibody-like heterodimers consisting of polypeptide α- and β-chains. Each of the chains is 280 amino acids long, and the large extracellular portion of each chain is folded into two Ig-like domains: one variable (V) and one constant (C). The antibody-like heterodimer is encoded by genes that are assembled from several gene segments during the development of T cells in the thymus.

There are antigen-independent and antigen-dependent differentiation and specialization of B- and T-lymphocytes.

Antigen-independent proliferation and differentiation are genetically programmed for the formation of cells capable of giving a specific type of immune response when they encounter a specific antigen due to the appearance of special “receptors” on the plasmolemma of lymphocytes. It takes place in the central organs of immunity (thymus, bone marrow or bursa of Fabricius in birds) under the influence of specific factors produced by cells that form the microenvironment (reticular stroma or reticuloepithelial cells in the thymus).

antigen dependent proliferation and differentiation of T- and B-lymphocytes occur when they encounter antigens in peripheral lymphoid organs, with the formation of effector cells and memory cells (retaining information about the acting antigen).

The resulting T-lymphocytes form a pool long-lived, recirculating lymphocytes, and B-lymphocytes - short lived cells.

66. Characteristics of B-lymphocytes.

B-lymphocytes are the main cells involved in humoral immunity. In humans, they are formed from the SCM of the red bone marrow, then enter the bloodstream and then populate the B-zones of peripheral lymphoid organs - the spleen, lymph nodes, lymphoid follicles of many internal organs. Their blood contains 10-30% of the entire population of lymphocytes.

B-lymphocytes are characterized by the presence of surface immunoglobulin receptors (SIg or MIg) for antigens on the plasmalemma. Each B cell contains 50,000-150,000 antigen-specific SIg molecules. In the population of B-lymphocytes there are cells with various SIg: the majority (⅔) contain IgM, a smaller number (⅓) contain IgG, and about 1-5% contain IgA, IgD, IgE. In the plasma membrane of B-lymphocytes, there are also receptors for complement (C3) and Fc receptors.

Under the action of the antigen, B-lymphocytes in peripheral lymphoid organs are activated, proliferate, differentiate into plasma cells, actively synthesizing antibodies of various classes that enter the blood, lymph and tissue fluid.

Differentiation of B-lymphocytes

The precursors of B cells (pre-B cells) develop further in birds in the bursa of Fabricius (bursa), whence the name B-lymphocytes came from, in humans and mammals - in the bone marrow.

Bag of Fabricius (bursa Fabricii) - the central organ of immunopoiesis in birds, where the development of B-lymphocytes occurs, is located in the cloaca. Its microscopic structure is characterized by the presence of numerous folds covered with epithelium, in which lymphoid nodules are located, bounded by a membrane. The nodules contain epitheliocytes and lymphocytes at various stages of differentiation. During embryogenesis, a brain zone is formed in the center of the follicle, and on the periphery (outside the membrane) a cortical zone, into which lymphocytes from the brain zone probably migrate. Due to the fact that only B-lymphocytes are formed in the bursa of Fabricius in birds, it is a convenient object for studying the structure and immunological characteristics of this type of lymphocytes. The ultramicroscopic structure of B-lymphocytes is characterized by the presence of groups of ribosomes in the form of rosettes in the cytoplasm. These cells have larger nuclei and less dense chromatin than T-lymphocytes due to the increased euchromatin content.

B-lymphocytes differ from other cell types in their ability to synthesize immunoglobulins. Mature B-lymphocytes express Ig on the cell membrane. Such membrane immunoglobulins (MIg) function as antigen-specific receptors.

Pre-B cells synthesize intracellular cytoplasmic IgM but lack surface immunoglobulin receptors. Bone marrow virgil B lymphocytes have IgM receptors on their surface. Mature B-lymphocytes carry on their surface immunoglobulin receptors of various classes - IgM, IgG, etc.

Differentiated B-lymphocytes enter the peripheral lymphoid organs, where, under the action of antigens, proliferation and further specialization of B-lymphocytes occur with the formation of plasma cells and memory B-cells (VP).

During their development, many B cells switch from producing antibodies of one class to producing antibodies of other classes. This process is called class switching. All B cells begin their antibody synthesis activity by producing IgM molecules, which are incorporated into the plasma membrane and serve as antigen receptors. Then, even before interacting with the antigen, most of the B cells proceed to the simultaneous synthesis of IgM and IgD molecules. When a virgil B cell switches from producing membrane-bound IgM alone to simultaneously producing membrane-bound IgM and IgD, the switch is likely due to a change in RNA processing.

When stimulated with an antigen, some of these cells become activated and begin to secrete IgM antibodies, which predominate in the primary humoral response.

Other antigen-stimulated cells switch to producing IgG, IgE, or IgA antibodies; Memory B cells carry these antibodies on their surface, and active B cells secrete them. IgG, IgE, and IgA molecules are collectively referred to as secondary class antibodies because they appear to be formed only after antigen challenge and predominate in secondary humoral responses.

With the help of monoclonal antibodies, it was possible to identify certain differentiation antigens, which, even before the appearance of cytoplasmic µ-chains, make it possible to attribute the lymphocyte carrying them to the B-cell line. Thus, the CD19 antigen is the earliest marker that allows one to attribute a lymphocyte to the B-cell series. It is present on pre-B cells in the bone marrow, on all peripheral B cells.

The antigen detected by monoclonal antibodies of the CD20 group is specific for B-lymphocytes and characterizes the later stages of differentiation.

On histological sections, the CD20 antigen is detected on B-cells of the germinal centers of lymphoid nodules, in the cortical substance of the lymph nodes. B-lymphocytes also carry a number of other (eg, CD24, CD37) markers.

67. Macrophages play an important role in both natural and acquired immunity of the body. The participation of macrophages in natural immunity is manifested in their ability to phagocytosis and in the synthesis of a number of active substances - digestive enzymes, components of the complement system, phagocytin, lysozyme, interferon, endogenous pyrogen, etc., which are the main factors of natural immunity. Their role in acquired immunity consists in the passive transfer of antigen to immunocompetent cells (T- and B-lymphocytes), in the induction of a specific response to antigens. Macrophages are also involved in providing immune homeostasis by controlling the reproduction of cells characterized by a number of abnormalities (tumor cells).

For the optimal development of immune responses under the action of most antigens, the participation of macrophages is necessary both in the first inductive phase of immunity, when they stimulate lymphocytes, and in its final phase (productive), when they participate in the production of antibodies and destruction of the antigen. Antigens phagocytosed by macrophages elicit a stronger immune response than those not phagocytosed by them. Blockade of macrophages by introducing a suspension of inert particles (for example, carcasses) into the body of animals significantly weakens the immune response. Macrophages are capable of phagocytizing both soluble (for example, proteins) and particulate antigens. Corpuscular antigens elicit a stronger immune response.

Some types of antigens, such as pneumococci, containing a carbohydrate component on the surface, can be phagocytized only after preliminary opsonization. Phagocytosis is greatly facilitated if the antigenic determinants of foreign cells are opsonized, i.e. linked to an antibody or an antibody-complement complex. The opsonization process is provided by the presence of receptors on the macrophage membrane that bind part of the antibody molecule (Fc fragment) or part of the complement (C3). Only antibodies of the IgG class can directly bind to the macrophage membrane in humans when they are in combination with the corresponding antigen. IgM can bind to the macrophage membrane in the presence of complement. Macrophages are able to "recognize" soluble antigens, such as hemoglobin.

In the mechanism of antigen recognition, two stages are closely related to each other. The first step is phagocytosis and digestion of the antigen. In the second stage, macrophage phagolysosomes accumulate polypeptides, soluble antigens (serum albumins), and corpuscular bacterial antigens. Several introduced antigens can be found in the same phagolysosomes. The study of the immunogenicity of various subcellular fractions revealed that the most active antibody formation is caused by the introduction of lysosomes into the body. The antigen is also found in cell membranes. Most of the processed antigen material secreted by macrophages has a stimulating effect on the proliferation and differentiation of T- and B-lymphocyte clones. A small amount of antigenic material can be stored in macrophages for a long time in the form of chemical compounds consisting of at least 5 peptides (possibly in connection with RNA).

In the B-zones of the lymph nodes and spleen, there are specialized macrophages (dendritic cells), on the surface of numerous processes of which many antigens are stored that enter the body and are transmitted to the corresponding clones of B-lymphocytes. In the T-zones of lymphatic follicles, interdigitating cells are located that affect the differentiation of T-lymphocyte clones.

Thus, macrophages are directly involved in the cooperative interaction of cells (T- and B-lymphocytes) in the body's immune responses.

Lymphocytes are special cells in the body of a living being. They are responsible for its protection from external irritants, infections, viruses. But the very concept of "lymphocytes" is quite extensive and general. Within themselves, these cells will be divided into several more groups. In the article we will get acquainted in detail with one of them - T-lymphocytes. Functions, types of cells, their normal parameters, deviations from the norm in human blood - all these topics will be discussed further.

Origin of cells

Where are T-lymphocyte cells formed? Although the main place of their "residence" is the bloodstream (lymphocytes also live in other tissues), they are formed far from there. The place of their "birth" is the bone red marrow. It is known as the body's hematopoietic tissue. That is, in addition to lymphocytes, erythrocytes, white blood cells (neutrophils, leukocytes, monocytes) will also form here.

The structure of lymphocytes

The "anatomical" features are as follows:

Large core round or oval.
There will be no granularity in the cytoplasm (the contents of the cell itself).
If there is little cytoplasm in the cell, it is called narrow plasma, if there is a lot - wide plasma.

In their structure, the lymphocytes that inhabit the blood will differ slightly from their counterparts that have settled in other tissues. And that's okay. Moreover, cells "living" in one place will also have some external differences between themselves.

Types of lymphocytes

In addition to types of T-lymphocytes, there are various groupings of these cells in general. Let's take a look at them.

The first classification is by size:

Small.
Large.

The second classification is according to the functions performed:

B-lymphocytes. They can recognize foreign particles and produce deadly antibodies against them. In other words, they are responsible for humoral immunity.
T-lymphocytes. The main function is responsibility for cellular immunity. They come into contact with foreign bodies and destroy them.
NK cells. Natural killers that can recognize cancerous, defective cells and destroy them. They are responsible for maintaining the normal cellular composition of the whole organism.

Varieties of T-lymphocytes

This group of lymphocytes within itself will be divided into several types:

T-killers.
T-helpers.
T-suppressors.
Memory T cells.
Amplifier-lymphocytes.

T-killers: what kind

These are the most famous representatives of the T-lymphocyte group. Their main task is the destruction of defective, defective cells of the body. Another name for the group is cytotoxic T-lymphocytes. In other words, they are responsible for the elimination of cells ("cyto") that have a toxic effect on the entire body.

The main function of T-killers is immune surveillance. Cells aggressively act on a foreign protein. It is this useful function that can be harmful when transplanting organs to a person. T-killers seek to quickly destroy the "alien", not realizing that it is he who is able to save the body. Therefore, the patient takes medication for some time after organ transplantation, which depresses the immune system. The drugs reduce the percentage of T-killers in the blood, disrupt their interaction. Thanks to this, the transplanted organ takes root, and the patient is not threatened with complications and death.

The mechanism of action of this type of lymphocytes on a foreign element is very interesting. Phagocytes, for example, aggressively "attack" the "stranger" for its subsequent devouring and digestion. T-killers in their background are "noble killers". They touch the object with their processes, then break contact and move away. Only after such a "death kiss" does the foreign microorganism die. Why?

When touched, T-killers leave a piece of their membrane on the surface of the body. It has properties that allow it to corrode the surface of the object of attack - up to the formation of through holes. Through these holes, potassium ions leave the microorganism, and water and sodium ions take their place. The cell barrier is broken, there is no longer a boundary between the internal and external environment. The microorganism inflates the water that has entered it, the proteins of the cytoplasm and organelles are destroyed. The remains of the "stranger" are then devoured by phagocytes.

Helpers

The main function of these T-lymphocyte cells is to help. Hence their name, derived from the English word, translated in the same way.

But to whom or what do these T-lymphocytes come to the rescue? They are designed to induce and stimulate an immune response. It is under the influence of T-helpers that T-killers, with whom we have already met, will activate their work.

Helpers will transmit data about the presence of a foreign protein in the body. And this is valuable information for B-lymphocytes - they, in turn, begin to secrete certain protective antibodies against it.

Also, T-helpers stimulate the work of another type of "guard" cells - phagocytes. In particular, they tightly interact with monocytes.

Suppressors

The term itself means "suppression". From here, the function of T-suppressors becomes clear to us. Helpers in our body will activate the protective, immune function, and these T-lymphocytes, on the contrary, will suppress it.

Do not think that this has any negative impact on the system. T-suppressors are responsible for the regulation of the immune response. After all, somewhere it is necessary to react to a certain stimulus with restraint and moderation, and somewhere - to accumulate all available forces against it.

Amplifiers

Let us now turn to the functions of T-lymphocytes of this group. After one or another aggressor enters the body, the content of lymphocytes immediately increases in the blood and tissues of a living being. For example, in just a few hours, their volume can double!

What is the reason for such a rapid growth of the army of defender cells? Maybe the fact is that in the body somewhere for the time being they are "hidden" in reserve?

It really is. Some mass of mature full-fledged lymphocytes lives in the thymus and spleen. Only up to some point these cells are "not determined" with their purpose, function. They will be called amplifiers. If necessary, these cells turn into one or another type of T-lymphocytes.

memory cells

Experience, as you know, is the main weapon. Therefore, having coped with any threat, our T-lymphocytes remember it. In turn, the body produces special cells that will store this information until a new "battle" with this foreign element. These elements will be memory T-cells.

A secondary aggressor (of the kind that the immune system has already resisted) enters the body. The memory T cell recognizes it. Then this particle begins to actively multiply in order to give a decent secondary immune response to a foreign organism.

Normal values of T-lymphocytes in human blood

In this category, it is impossible to imagine any specific figure - normal values \u200b\u200bwill vary depending on the age of the person. This is due to the peculiarities of the development of his immune system. With age, the volume of the thymus gland will decrease. Therefore, if in childhood lymphocytes predominate in the blood, then with adulthood they transfer the leading position to neutrophils.

The level of T-lymphocytes in the blood helps to determine the general clinical analysis of blood. The normal numbers are:

(50.4±3.14)*0.6-2.5 thousand
50-70%.
The ratio of "helpers / suppressors" - 1.5-2.

What do high and low readings mean?

An increased content of T-lymphocytes in the blood may indicate the following:

Chronic or acute lymphocytic leukemia.
Hyperactive immunity.
Cesari syndrome.

On the contrary, a low content of T-elements indicates the following pathologies and diseases:

Chronic infections - purulent processes, HIV, tuberculosis.
Decreased production of lymphocytes.
Genetic diseases that cause immunodeficiency.
Tumors of the lymphoid tissue.
Renal and heart failure observed in the last stage.
T-cell lymphoma.
The patient is taking medications that destroy lymphocytes.
A consequence of radiation therapy.

We got acquainted with T-lymphocytes - the cells-defenders of our body. Each type performs its own specific function.

What is the norm of lymphocytes in the blood? Is there a difference in their number in men and women, children and adults? Now we'll tell you everything. The level of lymphocytes in the blood is determined during general clinical tests for the purpose of primary diagnosis of the presence of infectious diseases, allergic reactions, and, if necessary, to assess the side effects of drugs and the effectiveness of the chosen treatment.

Determining the amount of activated lymphocytes is not a routine laboratory test and is carried out only when indicated.

This analysis is not performed separately from the general immunological examination of the patient or the determination of other leukocyte cells (eosinophils, monocytes, lymphocytes in the blood, etc.) since it has no diagnostic value in isolation.

lymphocytes- These are white blood cells (a type of leukocytes), through which the protective function of the human body from foreign infectious agents and its own mutant cells is realized.

Abs lymphocytes- this is the absolute number of this type of cells, determined by the formula:

Total white blood cell count * Lymphocyte count (%)/100

Activated lymphocytes are divided into 3 subpopulations:

T-lymphocytes - mature in the thymus, are responsible for the implementation of the cellular type of the immune response (direct interaction of immune cells with pathogens). They are divided into T-helpers (they take part in antigen presentation of cells, the severity of the immune response and in the synthesis of cytokines) and cytotoxic T-lymphocytes (recognize foreign antigens and destroy them due to the release of toxins or the introduction of perforins that damage the integrity of the cytoplasmic membrane);
B-lymphocytes - provide humoral immunity through the production of specific protein molecules - antibodies;
NK-lymphocytes (natural killers) - dissolve cells infected with viruses or undergone malignant transformation.

It is known that lymphocytes in the blood are capable of synthesizing a number of antigens on their surface, and each of them is unique for its subpopulation and stage of cell formation. The functional activity of such cells is different. In most cases, they are a target for other leukocytes at the stage of immunophenotyping.

Cluster of differentiation and its types

Cluster designation - an artificially created nomenclature with the assignment of a number of various antigens that are produced on the surface of lymphocytes in the blood. Synonyms for the term: CD, CD antigen or CD marker.

During laboratory diagnosis, the presence of labeled cells in the general subpopulation of white blood cells is determined using monoclonal (same) antibodies with labels (based on fluorochrome). When antibodies interact with strictly specific CD antigens, a stable “antigen-antibody” complex is formed, while it is possible to count the remaining free labeled antibodies and determine the number of lymphocytes in the blood.

There are 6 types of CD antigen clusters:

3 - characteristic of T-lymphocytes, takes part in the formation of the signal transduction complex along the membrane;
4 - is identified on several types of leukocytes, helps to facilitate the process of recognition of foreign antigens when interacting with MHC (major histocompatibility complex) class 2;
8 - presented on the surface of cytotoxic T-, NK-cells, the functionality is similar to the previous type of clusters, only antigens associated with MHC class 1 are recognized;
16 - present on various types of white blood cells, is part of the receptors responsible for the activation of phagocytosis and cytotoxic response;
19 - component of B-lymphocytes, necessary for their proper differentiation and activation;
56 - is produced on the surface of NK- and some T-cells, it is necessary to ensure their attachment to tissues affected by malignant tumors.

Indications for research

Activated lymphocytes in the blood of a child and adults are determined when:

diagnostics of autoimmune diseases, oncopathologies, allergic reactions and their severity;
diagnostics and control of treatment of acute infectious pathologies;
differential diagnosis of viral and bacterial infections;
assessment of the state of the immune system (including in the presence of immunodeficiencies);
assessment of the intensity of the immune response in case of severe infections that have become chronic;
comprehensive examination before and after major surgery;
suspicion of suppression of the immune status caused by a genetic mutation;
control of the degree of immunity tension against the background of taking immunosuppressants or immunostimulants.

The norm of lymphocytes in the blood

The number of lymphocytes in the blood is determined using flow cytometry, the study period is 2-3 days, excluding the day of taking the biomaterial. It is important to correctly interpret the results obtained, it is desirable to attach the opinion of an immunologist to the immunogram. The final diagnosis is established by the totality of data from laboratory and instrumental examination methods, as well as the clinical picture of the patient.

It is noted that the diagnostic value increases significantly when assessing the intensity of immunity in a person in dynamics with regular repeated analyzes.

Activated lymphocytes in a blood test in a child and an adult are different, therefore, when deciphering the results, normal (reference) values should be selected, taking into account the age of the patient.

Table of normal range of lymphocytes by age

The table shows the values of acceptable norms of lymphocytes (individual subpopulations) in the blood in children and adults.

Age	Share of the total number of lymphocytes, %	*Absolute number of cells, 10 6 /l**
CD 3 + (T-lymphocytes)
Up to 3 months	50 – 75	2065 – 6530
Up to 1 year	40 – 80	2275 – 6455
1 – 2 years	52 – 83	1455 – 5435
25 years	61 – 82	1600 – 4220
5 – 15 years	64 – 77	1410 – 2020
Over 15 years old	63 – 88	875 – 2410
CD3+CD4+ (T-helpers)
Up to 3 months	38 – 61	1450 – 5110
Up to 1 year	35 – 60	1695 – 4620
1 – 2 years	30 – 57	1010 – 3630
25 years	33 – 53	910- 2850
5 – 15 years	34 – 40	720 – 1110
Over 15 years old	30 – 62	540 – 1450
CD3+CD8+ (T-cytotoxic lymphocytes)
Up to 3 months	17 – 36	660 – 2460
Up to 1 year	16 – 31	710 – 2400
1 – 2 years	16 – 39	555 – 2240
25 years	23 – 37	620 – 1900
5 – 15 years	26 – 34	610 – 930
Over 15 years old	14 – 38	230 – 1230
CD19+ (B-lymphocytes)
Up to 2 years	17 – 29	490 — 1510
25 years	20 – 30	720 – 1310
5 – 15 years	10 – 23	290 – 455
Over 15 years old	5 – 17	100 – 475
CD3-CD16+CD56+ (NK cells)
Up to 1 year	2 – 15	40 – 910
1 – 2 years	4 – 18	40 – 915
25 years	4 – 23	95 – 1325
5 – 15 years	4 – 25	95 – 1330
Over 15 years old	4 – 27	75 – 450
Over 15 years old	1 – 15	20-910

Deviation from reference values

Patients ask themselves: what does it mean if the lymphocytes in the blood are higher or lower than normal? It should be noted that a slight deviation from the reference values may be the result of improper preparation for analysis. In this case, it is recommended to repeat the study.

The presence of a large number of atypical lymphocytes in a blood test in a child or adult indicates a pathological process. It is important to determine which type of the general subpopulation of white blood cells deviates from the norm.

T-lymphocytes

An increase in T-lymphocytes (CD3 + CD19-) is observed against the background of leukemia, acute or chronic stages of the infectious process, hormonal failure, prolonged use of drugs and biological additives, as well as high physical exertion and pregnancy. If the criterion is lowered, an assumption is made about liver damage (cirrhosis, cancer), autoimmune pathologies, immunodeficiencies, or suppression of immunity by drugs.

T-helpers

The concentration of T-helpers (CD3 + CD4 + CD45 +) significantly increases with beryllium intoxication, a number of autoimmune diseases and some infectious infections. A decrease in value is the main laboratory sign of secondary immunodeficiency, and can also be observed when taking steroid drugs and cirrhosis of the liver.

Increase in T-cytotoxic lymphocytes

The reasons for the increase in T-cytotoxic lymphocytes (CD3 + CD8 + CD45 +) are:

allergic reaction of immediate type;
autoimmune pathologies;
lymphosis;
viral infection.

Deviation from the norm to a smaller side indicates the suppression of the natural immunity of a person.

B-lymphocytes (CD19 + CD3 -) increase with severe emotional or physical stress, lymphoma, autoimmune diseases, as well as in case of prolonged formaldehyde vapor intoxication. Reactive B lymphocytes decrease if they migrate to the focus of the inflammatory process.

Two types of natural killers: CD3 - CD56 + CD45 + and CD3 - CD16 + CD45 + reach their maximum values in the regeneration phase of the human body after hepatitis and pregnancy, as well as in some onco-, autoimmune and hepatic pathologies. Their reduction is facilitated by the abuse of tobacco smoking and steroid drugs, as well as some infections.

How to prepare for the analysis?

In order to obtain the most reliable results, it is necessary to strictly follow the rules of preparation before donating the biomaterial, since lymphocytes in the blood are sensitive to many external factors (stress, drugs). The biomaterial for the study is venous blood serum from the cubital vein.

1 day before donating blood, the patient should stop drinking alcohol and any alcohol-containing products, as well as all medications. If it is impossible to cancel vital drugs, you need to report their intake to honey. staff. In addition, physical and emotional stress is excluded, which can cause an increase in the studied criteria.

Blood is donated on an empty stomach, the minimum interval between the procedure for taking the biomaterial and the last meal is 12 hours. For half an hour you need to stop smoking.

conclusions

Summing up, it is necessary to highlight the important aspects:

the study is the main component in the diagnosis of lesions of the immune system;
normal values are selected according to the age of the examined patient;
the accuracy of the data obtained depends not only on the correct implementation of the analysis methodology, but also on compliance with all the rules for preparing the person himself;
it is unacceptable to use an immunogram separately for making a final diagnosis, since the deviation from the norm of various subpopulations of cells of the immune system may indicate a number of similar pathologies. In this case, an additional examination is prescribed, including a set of tests: C3 and C4 complement components, circulating immune complexes, as well as total immunoglobulins of classes A, G and M.

The total number of T-lymphocytes in the blood of adults is normal - 58-76%, the absolute number is 1.1-1.7-10 "/L.

Mature T-lymphocytes are "responsible" for the reactions of cellular immunity and carry out immunological supervision of antigenic homeostasis in the body. They are formed in the bone marrow, and receive differentiation in the thymus, where they are divided into effector (T-killer lymphocytes, T-lymphocytes of delayed-type hypersensitivity) and regulatory (T-lymphocytes-helpers, T-lymphocytes-suppressors) cells. In accordance with this, T-lymphocytes perform two important functions in the body: effector and regulatory. The effector function of T-lymphocytes is specific cytotoxicity towards foreign cells. The regulatory function (system T-helpers - T-suppressors) is to control the intensity of the development of a specific reaction of the immune system to foreign antigens. A decrease in the absolute number of T-lymphocytes in the blood indicates a lack of cellular immunity, an increase indicates an overactive immune system and the presence of immunoproliferative diseases.

The development of any inflammatory process is accompanied by a decrease in the content of T-lymphocytes almost throughout its entire length. This is observed in inflammations of a wide variety of etiologies: various infections, non-specific inflammatory processes, destruction of damaged tissues and cells after surgery, trauma, burns, heart attack, destruction of malignant tumor cells, trophic destruction, etc. The decrease in the number of T-lymphocytes is determined by the intensity of the inflammatory process, but this pattern is not always observed. T-lymphocytes most rapidly of all immunocompetent cells respond to the onset of the inflammatory process. This reaction manifests itself even before the development of the clinical picture of the disease. An increase in the number of T-lymphocytes during the inflammatory process is a favorable sign, and a high level of T-lymphocytes with pronounced clinical manifestations of such a process, on the contrary, is an unfavorable sign indicating a sluggish course of the inflammatory process with a tendency to become chronic. The complete completion of the inflammatory process is accompanied by the normalization of the number of T-lymphocytes. An increase in the relative number of T-lymphocytes is not of great importance for the clinic. However, an increase in the absolute number of T-lymphocytes in the blood is very important for the diagnosis of leukemia. Diseases and conditions leading to a change in the number of T-lymphocytes in the blood are presented in Table. 7.19.

Table 7.19. Diseases and conditions leading to a change in the number

T-lymphocytes (CD3) in the blood

Continuation of Table 7.19

T-lymphocytes-helpers (CD4) in the blood

The number of T-lymphocytes-helpers in the blood in adults is normal - 36-55%, absolute

Quantity - 0,4-1,110"/l-

T-lymphocytes are helpers (inducers) of the immune response, cells that regulate the strength of the body's immune response to a foreign antigen, control the constancy of the body's internal environment (antigenic homeostasis) and cause increased production of antibodies. An increase in the number of T-lymphocytes-helpers indicates an overactive immune system, a decrease indicates an immunological deficiency.

The ratio of T-helpers and T-suppressors in the peripheral blood plays a leading role in assessing the state of the immune system, since the intensity of the immune response depends on this. Normally, cytotoxic cells and antibodies should be produced as much as they are necessary to remove one or another antigen. Insufficient activity of T-suppressors leads to the predominance of the influence of T-helpers, which contributes to a stronger immune response (pronounced antibody production and / or prolonged activation of T-effectors). Excessive activity of T-suppressors, on the contrary, leads to a rapid suppression and abortive course of the immune response and even the phenomena of immunological tolerance (immunological response to the antigen does not develop). With a strong immune response, the development of autoimmune and allergic processes is possible. The high functional activity of T-suppressors in such a response does not allow the development of an adequate immune response, and therefore infections and a predisposition to malignant growth predominate in the clinical picture of immunodeficiencies. CD4/CD8 index 1.5-2.5 corresponds to a normal state, more than 2.5 - hyperactivity, less than 1.0 - immunodeficiency. In a severe course of the inflammatory process, the CD4/CD8 ratio may be less than 1. This ratio is of fundamental importance in assessing the immune system in AIDS patients. In this disease, the human immunodeficiency virus selectively infects and destroys CO4 lymphocytes, resulting in a decrease in the CD4/CD8 ratio. before values much less than 1.

An increase in the CD4/CD8 ratio (up to 3) is often observed in the acute phase of various inflammatory diseases due to an increase in the level of T-helpers and a decrease in T-suppressors. In the middle of an inflammatory disease, there is a slow decrease in T-helpers and an increase in T-suppressors. When the inflammatory process subsides, these indicators and their ratio are normalized. An increase in the CD4 / CD8 ratio is characteristic of almost all autoimmune diseases: hemolytic anemia, immune thrombocytopenia, Hashimoto's thyroiditis, pernicious anemia, Goodpasture's syndrome, systemic lupus erythematosus, rheumatoid arthritis. An increase in the CD4/CD8 ratio due to a decrease in the level of CD8 in these diseases is usually detected at the height of an exacerbation with a high activity of the process. A decrease in the CD4/CD8 ratio due to an increase in the level of CD8 is characteristic of a number of tumors, in particular Kaposi's sarcoma. Diseases and conditions leading to a change in the number of CD4 in the blood are presented in Table. 7.20.

Table 7.20. Diseases and conditions that lead to a change in the number of CD4 in the blood

Continuation of the table. 7.20

In the process of evolution, a person has formed two systems of immunity - cellular and humoral. They arose as a means of combating substances that are perceived as foreign. These substances are called antigens. In response to the introduction of an antigen into the body, depending on the chemical composition, dose and form of administration, the immune response will be different: humoral or cellular. The division of immunity functions into cellular and humoral is associated with the existence of T- and B-lymphocytes. Both lines of lymphocytes develop from lymphatic stem cells in the bone marrow.

T-lymphocytes. Cellular immunity. Thanks to T-lymphocytes, the cellular immune system of the body occurs. T-lymphocytes are formed from hematopoietic stem cells that migrate from the bone marrow to the thymus gland.

The formation of T-lymphocytes is divided into two periods: antigen-independent and antigen-dependent. The antigen-independent period ends with the formation of antigen-reactive T-lymphocytes. During the antigen-dependent period, the cell prepares to meet the antigen and multiplies under its influence, resulting in the formation of various types of T cells. Antigen recognition occurs due to the fact that on the membrane of these cells there are receptors that recognize antigens. As a result of recognition, cells multiply. These cells fight antigen-bearing microorganisms or cause rejection of foreign tissue. T cells regularly move from lymphoid elements into the blood, the interstitial environment, which increases the likelihood of their encounter with antigens. There are various subpopulations of T-lymphocytes: T-killers (i.e. fighters), destroying cells with an antigen; T-helpers that help T- and B-lymphocytes respond to antigen, etc.

T-lymphocytes, upon contact with the antigen, produce lymphokines, which are biologically active substances. With the help of lymphokines, T-lymphocytes control the function of other leukocytes. Various groups of lymphokines have been identified. They can both stimulate and inhibit the migration of macrophagocytes, etc. Interferon, produced by T-lymphocytes, inhibits the synthesis of nucleic acids and protects the cell from viral infections.

B-lymphocytes. humoral immunity. During the antigezavisimy period, B-lymphocytes are stimulated by the antigen and settle in the spleen and lymph nodes, follicles and reproduction centers. Here they are converted to plasma cells. Plasma cells synthesize antibodies - immunoglobulins. Humans produce five classes of immunoglobulins. B-lymphocytes take an active part in the immune processes of antigen recognition. Antibodies interact with antigens located on the surface of cells or with bacterial toxins and accelerate the uptake of antigens by phagocytes. The antigen-antibody reaction underlies humoral immunity.

During the immune response, the mechanisms of both humoral and cellular immunity usually operate, but to varying degrees. So, with measles, humoral mechanisms predominate, and with contact allergies or rejection reactions, cellular immunity.