Leukocytes

Leukocytes are the foundation of the immune system's protective function, since these are the cells that are the first to respond to the invasion of antigens into the human body. Leukocyte defense is the process of phagocytosis: active recognition of foreign elements, their capture and digestion. This property of leukocytes was discovered by the outstanding microbiologist and immunologist Ilya Ilyich Mechnikov at the beginning of the last century. The discovery was so revolutionary for that time that the scientist was awarded the Nobel Prize.

The quantitative indicator of leukocytes directly depends on the speed at which the bone marrow forms these white blood cells, and the rate of release and decay is also a very important criterion. Leukocytes are utilized and excreted after they have fulfilled their purpose - phagocytosis. All these parameters are influenced by many factors, so the leukocyte indicator can fluctuate within the normal range. At the end of the working day, leukocytes can increase slightly, as well as during intense stress - both physical and emotional. Even a passion for protein foods, a meat diet or a sharp change in climatic conditions can affect the number of leukocytes in the blood. The norm for an adult is considered to be a fluctuation from 4 to 9 thousand in 1 μl of blood.

Leukocytes are formed in the red bone marrow and in the lymph nodes. The number of leukocytes (WBC) in the circulating blood is an important diagnostic indicator.

Leukocytes have one main function - protecting the body from foreign agents. Thanks to their phagocytic activity, participation in cellular and humoral immunity, histamine exchange, antimicrobial, antitoxic, antibody-forming and other important components of immunological reactions are realized.

Leukocytes include cells of the granulocyte, monocytic and lymphoid series (see also “Leukocyte formula ”).

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ]

Leukocytes: changes in morphology

In severe infections, toxogenic granularity, cytoplasmic vacuolization, and Knyazkov-Dele bodies appear in blood granulocytes, which has serious prognostic significance. The presence of one or more of the above changes indicates the development of bacteremia and generalization of the infection.

Toxigenic granularity of neutrophils is a coarse dark red granularity that appears as a result of physicochemical changes in the cytoplasm under the influence of an infectious agent. It is believed that this pathology either reflects a violation of the maturation processes of neutrophils, as a result of which coarse granularity is preserved in mature cells, or is a result of the absorption of toxic substances. Leukocytes have these changes in purulent-septic diseases (often appear before the nuclear shift and is an unfavorable prognostic sign), lobar pneumonia, scarlet fever, and the disintegration of tumor tissue after radiation therapy.

Vacuolization of cytoplasm is detected less frequently, but it has no less diagnostic value. Leukocytes have these changes in sepsis (especially caused by anaerobic infection), abscesses, acute liver dystrophy.

Knyazkov-Dele bodies are large white-blue areas of cytoplasm of various shapes, free of specific granules. Leukocytes have these changes in inflammatory diseases, infections (measles, scarlet fever), sepsis, burns.

Hypersegmentation of neutrophil nuclei is the presence of more than 5 segments in the nuclei of neutrophils. Leukocytes have these changes with a hereditary constitutional feature, as well as a deficiency of vitamin B ₁₂ and folic acid. Congenital hypersegmentation is not accompanied by any clinical symptoms.

Pelger's leukocyte anomaly is a dominantly inherited disorder of granulocyte maturation characterized by decreased segmentation of neutrophil nuclei. Most often, mature neutrophils contain a two-segmented or unsegmented nucleus, rarely a three-segmented nucleus. In their physiological properties, such cells do not differ from normal, mature neutrophils.

Pseudo-Pelger's anomaly - a decrease in the segmentation of granulocyte nuclei - is possible in myeloproliferative diseases, agranulocytosis, multiple myeloma, tuberculosis. It is temporary, transient. After the patient recovers, pseudo-Pelger's leukocytes disappear. The basis of the anomaly of nuclear maturation is a violation of the metabolism of nucleic acids.

Leukolysis cells (Botkin-Gumprecht shadows) - half-destroyed lymphocyte nuclei with remnants of nucleoli - are found in chronic lymphocytic leukemia.

Leukocytes can vary in structure, cytoplasm structure and are divided into two main groups:

• Granulocytes (granular), in which the nucleus has a granular structure;
• Agranulocytes (non-granular), the cytoplasm of which does not contain granules.

In turn, granulocytes have subtypes that are differentiated by histological shades:

• Eosinophils, which are stained by acidic environments;
• Basophils that stain with primary dyes;
• Neutrophils that can be stained with all types of media.

Next comes the division of neutrophils:

• Young, new metamyelocytes;
• Band-shaped, not fully mature;
• Segmented, mature, with segmented nuclei.

Neutrophilic leukocytes play an important role – phagocytic. Phagocytic activity depends on age; in elderly people, protective activity is reduced. Neutrophils are also capable of secreting lysozyme and interferon. Lysozyme is an important enzyme with an antibacterial effect, which hydrolyzes the cell walls of pathogens (bacteria, viruses) and destroys them. Interferon is the general name for a group of proteins with antiviral, immunomodulatory and oncoprotective effects.

Eosinophils are granulocyte cells with a segmented nucleus. These cells participate in phagocytosis and protect the body from allergies. Basophils are poorly studied cells because they are rarely encountered in analytical studies. Basophils participate in many immune processes, including antiallergic reactions.

Leukocytes of the agranulocytic type have two subtypes - monocytes and lymphocytes. Lymphocytes are the main link in the protective function of the immune system, which "patrols" the body and detects harmful antigens. Lymphocytes also monitor all internal, natural cells in order to detect mutations and atypical division, which is typical for the onset of oncological processes. The functioning of lymphocytes is impossible without the activity of "allies" - macrophages, which circulate through the bloodstream and tissues in order to recognize harmful elements. Lymphocytes occupy almost a third of all blood leukocytes, in young children their number is slightly higher, and with age the percentage level off. An increased number of lymphocytes indicates infectious diseases such as tuberculosis, cytomegalovirus, hepatitis, infectious mononucleosis. Lymphocytes also increase in malignant blood diseases - leukemia. A reduced number of lymphocytes signals a possible oncological process, immunodeficiency. Lymphocytopenia can also be caused by drug intoxication when the dosage of glucocorticoids is exceeded.

Leukocytes of the lymphocytic subtype are divided according to their functions into the following cells:

• B-lymphocytes are cells that work in the bone marrow, producing immunoglobulins. B-lymphocytes also have two subtypes - B-1 and B-2;
• T-lymphocytes, which control the production of antibodies by B-lymphocytes. These cells are named after the first letter of the important organ, the thymus, where they grow and mature;
• T-helpers, named for their main role – help. Helpers help synthesize antibodies;
• T-suppressors are a subtype of T-lymphocytes that suppress – inhibit excessive synthesis of immunoglobulins (suppress – to restrain);

Natural killers are cyto-like cells that try to contain and destroy viruses, as well as the oncological process.

Monocytes are the largest leukocytes, having a loose large nucleus and capable of transforming into macrophages. Macrophages actively participate in the humoral immune process, destroying bacteria and viruses.

Leukocytes, with their quantitative and structural indicators, can indicate the following diseases:

Elevated white blood cells

• Leukocytes are elevated in leukemia (the excess reaches hundreds of thousands);
• Leukocytes are elevated in leukocytosis (up to several tens of thousands);
• A neutrophil shift to the left side of the normal range indicates infectious diseases;
• Eosinophilia (exceeding the normal threshold) indicates an allergic reaction, chronic helminthic infestations;
• Lymphocytosis indicates several types of diseases – infectious mononucleosis, hematopoietic pathologies, tuberculosis, brucellosis, syphilis;

[ 8 ], [ 9 ], [ 10 ], [ 11 ]

Low white blood cells

Leukopenia, when leukocytes are low, may indicate rheumatoid arthritis, SLE - systemic lupus erythematosus, drug intoxication, pathology of the hematopoietic system, salmonellosis. Alcohol dependence, as well as diabetes, can be accompanied by a condition when leukocytes are low.

Leukocytes are an important indicator of the mandatory research minimum - laboratory tests. Determining the number of leukocytes helps to specify the diagnosis of the underlying disease and is important information for doctors of any specialization.