Leukocytes

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

The quantitative leukocyte count directly depends on the speed with which these white blood cells form the bone marrow, and the rate of excretion and decay is also a very important criterion. Leukocytes are recycled and removed after they have fulfilled their intended purpose - phagocytosis. All of these parameters are influenced by many factors, so the leukocyte index can fluctuate within the limits of the norm. At the end of the work day, the white blood cells can slightly increase, as well as with intense exercise - both physical and emotional. Even a hobby for protein food, a meat ration or a sharp change in climatic conditions can affect the number of leukocytes in the blood. The norm for an adult is considered to fluctuate 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 white blood cells (WBC) in circulating blood is an important diagnostic indicator.

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

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

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

Leukocytes: changes in morphology

In severe infections in granulocytes of blood, there are toxogenous granularity, vacuolation of the cytoplasm and the body of Knyazkova-Dele, which has a serious prognostic value. The presence of one or more of the above changes indicates the development of bacteremia and generalization of the infection.

The toxicogenic granularity of neutrophils is a coarse dark red 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 neutrophil maturation processes, as a result of which rough granularity is retained in mature cells, or is the 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), croupous pneumonia, scarlet fever, decay of tumor tissues after radiation therapy.

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

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

Hypersegmentation of neutrophil nuclei - 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 dominant inherited disruption of granulocyte maturation, characterized by a decrease in the segmentation of neutrophil nuclei. Most often, mature neutrophils contain a two-segment or non-segmented nucleus, rarely a three-segment nucleus. By their physiological properties, such cells do not differ from normal, mature neutrophils.

Pseudopelgerian anomaly - a decrease in the segmentation of granulocyte nuclei - is possible with myeloproliferative diseases, agranulocytosis, multiple myeloma, tuberculosis. It is temporary, transient. On recovery of the patient, pseudopelgerian leukocytes disappear. At the heart of the anomaly of maturation of nuclei is a violation of the metabolism of nucleic acids.

Cells of leukolysis (the shadow of Botkin-Humprecht) - dilapidated nuclei of lymphocytes with the remains of nucleoli - are found in chronic lymphocytic leukemia.

Leukocytes can be different in structure, structure of the cytoplasm and fall into two main groups: 

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

In turn, granulocytes have subspecies, which are differentiated according to histological shades: 

• Eosinophils, which are stained with acidic media; 
• Basophils stained with basic paints; 
• Neutrophils, which can be colored by all kinds of media.

Next comes the subdivision of neutrophils: 

• Young, new metamyelocytes; 
• Stabbed, not fully ripened; 
• Segmented, mature, with segmented nuclei.

Leukocytes of the neutrophilic series perform an important role - phagocytic. Phagocytic activity depends on age, in the elderly, the protective activity is reduced. Neutrophils can also release lysozyme and interferon. Lysozyme is an important enzyme that has an antibacterial action that hydrolyzes the cell walls of pathogenic agents (bacteria, viruses) and destroys them. Interferon is a general name for a group of proteins that have antiviral, immunomodulatory and oncoprotective effects.

Eosinophils are a granulocyte cell that has a segmented nucleus. These cells are involved in phagocytosis, protect the body from allergies. Basophils are poorly understood cells, because they are rarely found in analytical studies. Basophils take part in many immune processes, including in antiallergic reactions.

Leukocytes of the agranulocyte species have two subspecies - monocytes and lymphocytes. Lymphocytes - this is the main link of the protective function of immunity, which "patrols" the body and identifies harmful antigens. Also, lymphocytes control all internal, natural cells in order to detect mutation and atypical division, which is characteristic for the onset of oncological processes. The functioning of lymphocytes is impossible without the activity of "allies" - macrophages that run along the bloodstream and tissues in order to recognize harmful elements. Lymphocytes occupy almost a third of the composition of all blood leukocytes, in young children their number is somewhat larger, and with age, the percentage ratio is equalized. An increased number of lymphocytes is indicative of infectious diseases, such as tuberculosis, cytomegalovirus, hepatitis, infectious mononucleosis. Also, lymphocytes increase in malignant blood diseases - leukemia. A reduced number of lymphocytes signals a possible oncological process, immunodeficiency. Also, lymphocytopenia can be triggered by drug intoxication when the glucocorticoid dosage is exceeded.

The leukocytes of the lymphocyte subspecies are divided according to the 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 in B lymphocytes. These cells are named after the first letter of an important organ - the thymus, where they grow and mature; 
• T-helpers, received the name, which describes their main role - help. Helpers help synthesize antibodies; 
• T-suppressors - a subtype of T-lymphocytes that suppress - suppress excessive synthesis of immunoglobulins (suppress - restrain); 

Natural killer - Natural killer, cytotoxic cells that try to contain and destroy viruses, as well as oncoprocess.

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

Leukocytes with their quantitative and structural indicators may indicate such diseases: 

Elevated white blood cells

• Leukemia is elevated in leukemia (excess is hundreds of thousands); 
• Leukocytes are elevated in leukocytosis (up to several tens of thousands); 
• Neutrophil shift to the left side of the norm limits indicates infectious diseases; 
• Eosinophilia (exceeding the threshold of norms) indicates an allergic reaction, chronic helminthic invasions; 
• Lymphocytosis indicates several variants of diseases - infectious mononucleosis, hematopoietic pathologies, tuberculosis, brucellosis, syphilis; 

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Reduced leukocytes

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

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