Where do leukocytes come from? Lifespan of leukocytes: life cycle, formation and destruction. Complex chemical composition

Leukocytes are called white blood cells, which, together with platelets and red blood cells, belong to the formed particles of blood. These components play a significant role in protecting the body from dangerous infectious components. The human immune system protects itself by forming a barrier and detecting and destroying or eliminating foreign components from the body.

Formation of leukocytes

The shape of the cells resembles a sphere, inside of which there is a large nucleus and a small amount of cytoplasm. It is considered the most common type of white blood cell.

As a rule, they form in the bone marrow. This is explained by the fact that after the destruction of foreign harmful substances, leukocytes die along with them. However, in small quantities they are also formed in the thymus gland, spleen, lymph nodes and in the intestines and tonsils.

Leukocytes have very complex chemical pathways. They are capable of synthesizing protein and producing ribonucleic acid. However, they do not undergo mitosis in the blood, but there are some types that still retain this function. White cells are divided into three classes. They all perform their specific role and functions.

Life span of leukocytes

The lifespan of human blood cells is short. Their life can last from several days to several weeks. But this does not mean that they are fragile and unreliable. For example, from 7,000 to 25,000 white blood cells can simultaneously live in one drop of blood. If there is an infection in the body, then their number increases significantly.

The lifespan of leukocytes that circulate in the blood reaches from 3 to 9 hours. If they move through tissues, then on average 5 days. If a severe infection is detected in the human body, then their life cycle is significantly shortened. Then it only lasts a couple of hours. When exposed to an infection, leukocytes are immediately sent to their source. Then they destroy themselves.

Lymphocytes constantly circulate throughout the human body, entering the circulatory system and then reentering the tissue and lymph. As a result of this process, the lifespan of a group of cells changes. Depending on the need for these cells, leukocytes can live and circulate for a couple of weeks or several months.

Varieties of white cells

Leukocytes are divided into the following types:

Functions of leukocytes

The life of leukocytes in a person’s blood implies the performance of certain functions:

• informational;
• protection from the action of harmful cells that pose a danger;
• antibody production;
• hemostatic functionality;
• transport;
• synthetic;
• emigration of leukocytes.

Depending on how many leukocytes are in the blood, you can get information about the physical condition of a person and the possible development of pathology. The protective function involves a process called phagocytosis - when a pest enters the bloodstream, leukocytes attack the enemy and kill him.

The function of blood clotting is provided - hemostatic functionality. A function such as the production of antibodies characterizes the formation of active protein compounds to combat pathogens. Also, with the help of leukocytes, amino acids and active components are transported through blood vessels to organs.

Emigration of leukocytes occurs during the development of disease in the body. During this process, protected cells move through the walls of blood vessels and rush to the source of infection, destroying diseased tissue.

Normal blood levels and abnormalities

Depends on several factors. First of all, their numbers are affected by the age of a person. Young children will have more immune cells than adults. In addition, the number of leukocytes is influenced by both nutrition and time of day. On average, their number ranges from 3.5 to 10 units per liter.

When there is a quantity in the blood, this indicates improper functioning of the immune system and a possible disease. A disease characterized by a small amount of white cells in the blood is called leukopenia. It can occur as a result of a functional factor, such as improper and insufficient nutrition, a viral disease or x-ray.

There is another type of leukopenia – organic. Its appearance indicates that blood leukemia or aplastic anemia (a disorder of hematopoiesis) is developing in the body.

An increased number of white blood cells is called. There are three types of leukocytosis:

1. Redistributive. Occurs as a result of exposure to alcohol and drugs on the body, with increased physical activity, shock or other influences that are not associated with pathology.
2. Reactive. Occurs during a pathological process. Such processes include poisoning, intoxication, inflammation and exposure to bacteria.
3. Persistent. It speaks of cancer and is characterized by a high level of units in the blood.

However, indicators can change without illness. For example, jumps are typical during pregnancy, puberty, stress or depression.

Disorders and destruction of white blood cells

There are several pathological conditions that express a disorder of leukocytes. This is neutropenia - when the number of neutrophils in the body is very low. Also a disorder of white blood cells is an excessive number of neutrophils – neutrophil leukocytosis.

A low number of lymphocytes is called lymphocytopenia, and lymphocytic leukocytosis is a large number of lymphocytes. These two pathological conditions are also classified as leukocyte disorders.

The most common are disorders of leukocytes and neutrophils. Less – disorders of monocytes and eosinophils. A small percentage of the disorder is attributed to problems with basophils.

The life cycle of platelets, leukocytes and erythrocytes has been studied thoroughly. However, very little is said about their destruction. It has already been announced and proven that blood cells penetrate into the tissue structure after circulating in the blood. They do not return back to the blood. In tissues they perform their protective function and die.

Conclusion

With the help of leukocytes, a protective reaction occurs against damage by various infectious agents and other foreign substances. This type lives for a short time: some live only a few days, and some can live for several weeks.

Using leukocytes, you can determine a person’s condition. Their deficiency or excess indicates a possible illness in the body and problems in the functioning of the immune system. The number of units depends on the person’s age and nutrition.

Our body is an amazing thing. It is capable of producing all the substances necessary for life, coping with many viruses and bacteria, and finally providing us with a normal life.

Where are leukocytes formed in humans?

Human blood consists of formed elements and plasma. Leukocytes are one of these formed elements along with red blood cells and platelets. They are colorless, have a nucleus and can move independently. They can be seen under a microscope only after preliminary staining. From the organs where leukocytes are formed, they enter the bloodstream and body tissues. They can also freely pass from vessels to adjacent tissues.

Leukocytes move in the following way. Having secured itself on the wall of the vessel, the leukocyte forms a pseudopodia (pseudopod), which it pushes through this wall and clings to the tissue from the outside. Then it squeezes through the resulting gap and actively moves among other cells of the body that lead a “sedentary” lifestyle. Their movement resembles the movement of an amoeba (a microscopic single-celled organism from the category of protozoa).

Basic functions of leukocytes

Despite the similarity of leukocytes to amoebas, they perform complex functions. Their main tasks are to protect the body from various viruses and bacteria and destroy malignant cells. White blood cells chase bacteria, envelop them and destroy them. This process is called phagocytosis, which is Latin for “eating something by cells.” Destroying the virus is more difficult. During illness, viruses settle inside the cells of the human body. Therefore, in order to get to them, leukocytes need to destroy cells with viruses. Leukocytes also destroy malignant cells.

Where are leukocytes formed and how long do they live?

While performing their functions, many white blood cells die, so the body constantly reproduces them. Leukocytes are formed in organs that are part of the human immune system: in the bone marrow, lymph nodes, tonsils, spleen and in the lymphoid formations of the intestine (in Peyer's patches). These organs are located in different places in the body. It is also the place where leukocytes, platelets, and red blood cells are formed. It is believed that white blood cells live for about 12 days. However, some of them die very quickly, which happens when they fight with a large number of aggressive bacteria. Dead leukocytes can be seen if pus appears, which is a collection of them. They are replaced from organs related to the immune system, where leukocytes are formed, new cells emerge and continue to destroy bacteria.

Along with this, among T-lymphocytes there are immunological memory cells that live for decades. If a lymphocyte meets, for example, such a monster as the Ebola virus, it will remember it for the rest of its life. When they encounter this virus again, lymphocytes are transformed into large lymphoblasts, which have the ability to multiply quickly. Then they turn into killer lymphocytes (killer cells), which block the familiar dangerous virus from entering the body. This indicates existing immunity to this disease.

How do white blood cells know that a virus has entered the body?

Every human cell contains an interferon system, which is part of the innate immune system. When a virus enters the body, interferon is produced - a protein substance that protects uninfected cells from the penetration of viruses into them. At the same time, interferon is one of the types of leukocytes. From the bone marrow, where white blood cells are produced, they travel to infected cells and destroy them. In this case, some viruses and their fragments fall out of the destroyed cells. The dropped viruses try to penetrate into uninfected cells, but interferon protects these cells from their penetration. Viruses outside cells are not viable and die quickly.

The fight against viruses against the interferon system

In the process of evolution, viruses have learned to suppress the interferon system, which is too dangerous for them. Influenza viruses have a strong suppressive effect on it. This system is even more oppressed. However, all records were broken by the Ebola virus, which practically blocks the interferon system, leaving the body practically defenseless against a huge number of viruses and bacteria. More and more cells emerge from the spleen, lymph nodes and other organs related to the immune system, where white blood cells are formed. But, having not received a signal to destroy the virus, they remain inactive. In this case, the human body begins to decompose alive, many toxic substances are formed, blood vessels rupture, and the person bleeds to death. Death usually occurs in the second week of the disease.

When does immunity occur?

If a person has had one or another disease and recovered, then he develops a stable acquired immunity, which is provided by leukocytes belonging to the groups of T-lymphocytes and B-lymphocytes. These white blood cells are formed in the bone marrow from progenitor cells. Acquired immunity also develops after vaccination. These lymphocytes know well the virus that has entered the body, so their killing effect is targeted. The virus is practically unable to overcome this powerful barrier.

How do killer lymphocytes kill cells that have become dangerous?

Before you kill a dangerous cell, you need to find it. Killer lymphocytes tirelessly search for these cells. They focus on the so-called histocompatibility antigens (tissue compatibility antigens) located on cell membranes. The fact is that if a virus gets into a cell, then this cell, in order to save the body, dooms itself to death and, as it were, throws out a “black flag”, signaling the introduction of the virus into it. This “black flag” is information about the invading virus, which in the form of a group of molecules is located next to the histocompatibility antigens. This information is “seen” by the killer lymphocyte. He acquires this ability after training in the thymus gland. Control over learning outcomes is very strict. If a lymphocyte has not learned to distinguish a healthy cell from a diseased one, it itself will inevitably be destroyed. With this strict approach, only about 2% of killer lymphocytes survive, which subsequently leave the thymus gland to protect the body from dangerous cells. When the lymphocyte determines that the cell is infected, it gives it a “lethal injection” and the cell dies.

Thus, white blood cells play a huge role in protecting the body from pathogenic agents and malignant cells. These are small, tireless warriors of the body's main defenses - the interferon and immune systems. They die en masse in the fight, but from the spleen, lymph nodes, bone marrow, tonsils and other organs of the immune system, where leukocytes are formed in humans, they are replaced by many newly formed cells, ready, like their predecessors, to sacrifice their lives in the name of saving the human body. Leukocytes ensure our survival in an external environment filled with a huge number of different bacteria and viruses.

Blood is an extremely favorable environment: there is oxygen, there are nutrients - in a word, microorganisms that get there can feel very good and multiply rapidly (which the body does not need at all) - and they get there, because blood constantly passes through the lungs and intestines - the most “ dirty” places of the body (dirty because they receive substances from the outside world - and therefore foreign microorganisms)… that’s why the blood has acquired “armed forces”. How does this “army” work?

At dawn evolution- in the first multicellular organisms, all the cells that make up the organism had the ability to capture and digest nutrient particles. At the same time, not all cells “sat and waited” until the fluid circulating throughout the body (a prototype of blood) brought these same particles - some cells (a kind of “relic of a single-celled of the past") moved independently in the manner of amoebas in search of food. Along the way, they destroyed foreign objects that had entered the body.

In modern amphibians, such motile cells are still involved in the digestive processes, but in higher animals - including humans - they are completely focused on protecting the body from outside invasion.

« Leukocytes" means "white cells"... to be precise, they are transparent, larger red blood cells- and (unlike the latter) have a core. Nobody really knows what their life expectancy is (the terms range from 20 minutes to 15 days) - after all, leukocytes, as befits “soldiers,” rarely live to old age and much more often die in battle.

Leukocytes are not only found in the blood - they penetrate through the walls of capillaries into the tissues where microorganisms have entered in order to deal with them there. How do they do it? Yes, it’s very simple - by absorbing them and digesting them (remember what we said about the “evolutionary past” of these cells?), and each leukocyte can swallow up to 20 microorganisms. It is called phagocytosis , and our outstanding compatriot I.I. Mechnikov discovered such a phenomenon. In 1882, Ilya Ilyich lived in Italy on the Mediterranean coast - in a house with a garden where roses grew. Scientist observed moving cells in the transparent bodies of starfish larvae - and tried to understand their purpose. Mechnikov introduced rose thorns into the bodies of the larvae - and saw under a microscope how the moving cells attacked them, clinging to them from all sides... Subsequent long-term studies confirmed that the same thing happens in the human body. I.I. Mechnikov called this phenomenon phagocytosis, and motile cells - phagocytes (“devouring cells”).

By absorbing microorganisms, leukocytes die, releasing substances that kill microbes and attract new leukocytes to the affected area. The pus that then comes out is nothing more than an accumulation of dead leukocytes.

If, despite the efforts of phagocytes, the infection nevertheless breaks deep into the body, another type of leukocyte - lymphocytes - takes over. These cells recognize foreign substances (antigens) and produce special protein molecules - antibodies - against them. By the way, it is lymphocytes (more precisely, one of their varieties - T-lymphocytes) that are affected by HIV.

Leukocytes destroy not only foreign microorganisms, but also the body’s own damaged cells, clearing space for construction new, and young leukocytes also participate in the “construction” of certain tissues - bones, muscles, connective tissue.

But the story about leukocytes will be incomplete without mentioning one truly epoch-making discovery made with their help.

In 1869, the Swiss biochemist F. Miescher, who worked in Germany, studied the composition of leukocytes - he was especially interested in their nuclei (after all, science knew almost nothing about cell nuclei at that time). To obtain material for research, the scientist agreed with a local hospital, so that bandages stained with pus would be delivered to him from there - and Misher would wash the pus off the bandages with hydrochloric acid, after which only nuclei remained of the leukocytes. From the nuclei he isolated a mysterious substance that precipitated in the form of flakes or threads - and it was neither a protein nor a fatty substance. Miescher called the new substance nuclein (from the Latin nucleus - nucleus). Subsequently it was called nucleic acid...

Thus, from our protectors - leukocytes - the “holy of holies of life”, deoxyribonucleic acid (DNA), was first isolated.

In modern diagnostics, calculating the number of leukocytes is considered one of the most important laboratory tests. After all, the rapidity of increase in the concentration of white blood cells indicates how strong the immune system is and the body’s ability to protect itself from damage. It could be a simple cut on a finger at home, an infection, a fungus or a virus. How leukocyte cells help cope with foreign agents will be discussed in the article.

What are leukocytes?

Leukocytes are white blood cells; from a medical point of view, they are heterogeneous groups of cells, different in appearance and functional purpose. They form a reliable line of defense for the body from adverse external influences, bacteria, microbes, infections, fungi and other foreign agents. They are distinguished by the presence of a nucleus and the absence of their own color.

The structure of white cells

The structure and functions of cells differ, but they all have the ability to emigrate through capillary walls and move through the bloodstream to absorb and destroy foreign particles. During inflammation and diseases of an infectious or fungal nature, leukocytes increase in size, absorbing pathological cells. And over time, they self-destruct. But as a result, harmful microorganisms are released that cause the inflammatory process. In this case, swelling, increased body temperature and redness of the site of inflammation are observed.

Terms! Chemotaxis of leukocytes is their migration to the site of inflammation from the bloodstream.

The particles that cause an inflammatory reaction attract the right amount of white leukocytes to fight foreign bodies. And in the process of struggle they are destroyed. Pus is a collection of dead white blood cells.

Where are leukocytes produced?

In the process of providing a protective function, leukocytes produce protective antibodies, which will manifest themselves during inflammation. But most of them will die. Place of formation of white cells: bone marrow, spleen, lymph nodes and tonsils.

Terms! Leukopoiesis is the process of the appearance of leukocyte cells. Most often this occurs in the bone marrow.

How long do leukocyte cells live?

The lifespan of leukocytes is 12 days.

Leukocytes in the blood and their norm

To determine the level of leukocytes, it is necessary to conduct a general blood test. The units for measuring the concentration of leukocyte cells are 10*9/l. If tests show a volume of 4-10*9/l, you should be happy. For a healthy adult, this is a normative value. For children, the leukocyte level is different and is 5.5-10*9/l. A general blood test will determine the ratio of different types of leukocyte fractions.

Deviations from the normative white blood cell limit may be a laboratory error. Therefore, leukocytosis or leukocytopenia is not diagnosed by a single blood test. In this case, a referral is given for another analysis to confirm the result. And only then is the issue of a course of treatment for the pathology considered.

It is important to take responsibility for your health and ask your doctor what the tests show. Approaching the critical limit of leukocyte levels is an indicator that you need to change your lifestyle and diet. Without active actions, when people do not draw the right conclusions, illness occurs.

How is the number of leukocytes in plasma measured?

Leukocyte cells are measured during blood testing using a special optical device - the Goryaev camera. The counting is considered automatic and provides a high level of accuracy (with minimal error).

The optical device is a glass of special thickness in the form of a rectangle. A microscopic mesh is applied to it.

White blood cells are counted as follows:

1. Acetic acid, tinted with methylene blue, is poured into a glass test tube. This is a reagent into which you need to drop a little blood using a pipette for analysis. Afterwards everything is mixed well.
2. Wipe the glass and camera with gauze. Next, the glass is ground against the chamber until rings of different colors begin to form. The chamber is completely filled with plasma. You need to wait 60 seconds until the cell movement stops. The calculation is carried out using a special formula.

Functions of leukocytes

• First of all, mention should be made of the protective function. It involves the formation of the immune system in a specific and non-specific embodiment. The mechanism of operation of such defense involves phagocytosis.

Terms! Phagocytosis is the process of capturing hostile agents by blood cells or successfully destroying them.

• The transport function of leukocytes in an adult ensures the adsorption of amino acids, enzymes and other substances, their delivery to their destination (to the desired organ through the bloodstream).
• The hemostatic function in human blood is of particular importance in coagulation.
• The definition of sanitary function is the breakdown of tissues and cells that have died due to injury, infection, and damage.

• The synthetic function will provide the required number of leukocytes in the peripheral blood for the synthesis of biologically active components: heparin or histamine.

If we consider the properties of leukocytes and their functional purpose in more detail, it is worth mentioning that they have specific characteristics and capabilities due to their variety.

Leukocyte composition

To understand what leukocytes are, you need to consider their types.

Neutrophil cells

Neutrophils are a common type of white blood cell, making up 50-70 percent of the total. Leukocytes of this group are produced and move in the bone marrow and are classified as phagocytes. Molecules with segmented nuclei are called mature (segmented), and those with an elongated nucleus are called rod (immature). The production of the third type of young cells occurs in the smallest volume. While there are more mature leukocytes. By determining the ratio of the volume of mature and immature leukocytes, you can find out how intense the bleeding process is. This means that significant blood loss does not allow cells to mature. And the concentration of young forms will exceed their relatives.

Lymphocytes

Lymphocyte cells have a specific ability not only to distinguish relatives from a foreign agent, but also “remember” every microbe, fungus and infection that they have ever encountered. It is lymphocytes that are the first to rush to the site of inflammation to eliminate “uninvited guests.” They build a line of defense, launching a whole chain of immune reactions to localize inflammatory tissues.

Important! Lymphocyte cells in the blood are the central link of the body’s immune system, which instantly moves to the inflammatory focus.

Eosinophils

Eosinophilic blood cells are inferior in number to neutrophilic ones. But functionally they are similar. Their main task is to move in the direction of the lesion. They pass through blood vessels with ease and can absorb small foreign agents.

Monocyte cells, due to their functionality, are capable of absorbing larger particles. These are tissues affected by the inflammatory process, microorganisms and dead leukocytes that self-destructed in the process of fighting foreign agents. Monocytes do not die, but are engaged in preparing and cleaning tissues for regeneration and final recovery after an infection of an infectious, fungal or viral nature.

Basophils

This is the smallest group of leukocyte cells in terms of mass, which in relation to its relatives makes up one percent of the total number. These are the cells that appear as first aid where you need to instantly respond to intoxication or damage by harmful toxic substances or vapors. A striking example of such a lesion is the bite of a poisonous snake or spider.

Due to the fact that monocytes are rich in serotonin, histamine, prostaglandin and other mediators of the inflammatory and allergic process, the cells block poisons and their further spread in the body.

What does an increase in the concentration of leukocyte particles in the blood mean?

An increase in the number of white blood cells is called leukocytosis. The physiological form of this condition is observed even in a healthy person. And this is not a sign of pathology. This occurs after long-term exposure to direct sunlight, due to stress and negative emotions, and heavy physical exercise. In females, high white blood cells are observed during pregnancy and the menstrual cycle.

When the concentration of leukocyte cells exceeds the norm several times, you need to sound the alarm. This is a dangerous signal indicating the occurrence of a pathological process. After all, the body tries to protect itself from a foreign agent by producing more defenders - leukocytes.

After making a diagnosis, the attending physician should solve one more problem - to find the root cause of the condition. After all, it is not leukocytosis that is treated, but what caused it. Once the cause of the pathology is eliminated, after a couple of days the level of leukocyte cells in the blood will return to normal on its own.