White blood cells, or leukocytes, are cells of the immune system involved in protecting the body against both infectious disease and by various harmful substances. The process by which white blood cells destroy potentially harmful microorganisms, called phagocytosis. Redness of the skin, fever, pus formation are signs of active fighting white blood cells with pathogens and allergens. During these processes are killed so many white blood cells.
There are five different types of white blood cells; they are produced by bone marrow cells, which are called hematopoietic stem cells. Live leukocytes in humans, on average, three to four days. They are found throughout the body, including blood and lymphatic system. Diameter of leukocyte are from 7 to 21 micrometers.
The number of leukocytes in the blood may serve as an indicator of certain diseases. Leukocytes comprise about 1% of the blood volume of an adult. The excess of the normal level of white blood cells in the blood called leukocytosis; below normal levels of white blood cells is called leukopenia. The number of leukocytes in the blood may decrease due to a variety of chronic diseases, and because of strong and / or continuous stress
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. Physical properties of leukocytes, such as volume conductance and granularity may vary depending on the activity, presence of immature leukocytes or malignant cells, as in leukemia.
Types of white blood cells
White blood cells are divided into two main categories: granular white blood cells or granulocytes, and nezernistye leukocytes, or agranulocytes. These categories of lymphocytes characterized by the presence or absence of granules in the cytoplasm. The former include eosinophils, neutrophils and basophils, to the second - the lymphocytes and monocytes.
There are two types of lymphocytes: T cells and B cells. T-cells are formed in the thymus, lymph organs located behind the breastbone, and B cell - bone marrow. T cells produce proteins that are interpreted as a command phagocytes to destroy potentially harmful microorganisms. B-cells produce antibodies that help phagocytes recognize foreign elements. The size of cells is less than any of granulocytes; they account for about 25-30% of all white blood cells. Increasing the proportion of lymphocytes typical infectious mononucleosis and chronic infections.
Neutrophils protect the body from bacterial and fungal infections, as well as help in minor inflammatory processes that occur during the penetration into the body of microbes. As a result of the death of neutrophils formed pus. Neutrophils constitute 60-70% of the total number of leukocytes and live, on the average, 5, 4 days.
Eosinophils are involved mainly in combat parasitic infections. They are, moreover, are among the cells that cause inflammation in allergic reactions.
Basophils responsible mainly for allergic reactions. They cause the release of histamine and dilation of blood vessels.
Properties monocytes similar to those of neutrophils, but they have an additional function - they "show" pathogens to T cells, so that in the future they can recognize and destroy them. Monocytes were phased out blood and become macrophages, which are removed from the tissues of the body remains of dead cells, and struggling with various microorganisms. Furthermore, monocytes can remain active for much longer than neutrophils.
White blood cell types and their structure
White blood cells, or white blood cells - are cells that perform a protective function. The number of leukocytes in blood depends on the rate of their formation and their mobilization from the bone marrow, as well as their utilization (decay and excretion), and migration into tissue inflammatory foci. These processes are in turn influenced by a number of physiological factors, so the number of leukocytes in the blood of a healthy person is subject to fluctuations: it rises towards the end of the day, during physical exertion, emotional stress, taking protein foods (such as meat), a sharp change in the ambient temperature. Normally, the number is 4-9 thousand per 1 l of blood (4-9h109 / l).
White blood cells are divided into granules or granulocytes (their core has a granular structure) and nezernistye (agranulocytes), the core of which has nezernistuyu structure, these types of white blood cells perform different tasks.
Structure and function of granulocytes
Granulocytes are divided into three groups: Neutrophils, eosinophils and basophils. Neutrophils can be immature (young) - very few of them, and in the general analysis of blood can not be not fully mature or stab - they have a core in the form of rods and mature or segmented with nuclei, divided into 3-5 segments.
Neutrophils function operate in the body, or phagocytic cellular immunity: they absorb and dissolve pathogens. The younger the person, the greater the phagocytic activity of neutrophils, it falls with age. In addition, neutrophils secrete the enzyme lysozyme and antiviral substance interferon, which also help them cope with their task.
Eosinophils have a nucleus consisting of two segments and a round or oval beads which contain crystals. Eosinophils are also capable of phagocytosis, the function of protection against allergies, they absorb foreign proteins and neurotransmitters - biologically active substances which are released during allergic reactions such as histamine.
Structure basophils studied worse than that of other white blood cells, as these cells are rarely found in the blood. The main function of basophils - participate in immunological reactions (including inadequate, i.e. allergic) delayed type.
Agranulocytes
Agranulocytes nezernistye or leukocytes are divided into lymphocytes and monocytes.
Lymphocytes Human blood has a large core a spherical shape, which occupies nearly the entire cell. They are the basis of humoral immunity: when ingested foreign protein pathogens (antigens) they produce antibodies, which combine with antigens to form insoluble complexes, can be easily removed from the body.
Monocytes are the largest blood cells with a large nucleus loose. Monocytes eventually turns into macrophages - large cells, which are involved in cellular immunity (absorb bacteria and viruses) and produce factors that influence the formation of blood.
In general, the analysis of blood leucocytes decided to write everything in order, left to right: young - stab - segmented - cells - monocytes. Thus all leukocytes is taken as 100%, some kinds of them are expressed as a percentage. This analysis draws attention to the fact any longer granular leukocytes, and no less, respectively, talk about neutrophilic shift to the left or right.
Changing the number of white blood cells
A large increase in the number of leukocytes in blood to several hundred thousand points to malignant disease - leukemia. Increase in the number of white blood cells to tens of thousands called leukocytosis. Leukocytosis observed in acute inflammatory and infectious processes (other than influenza, measles
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and other infections). Increasing the number of cells in infections in most cases is accompanied by neutrophilic shift to the left, that is, an increase in the number of young palochkoyalernyh and neutrophils. In severe infections is clearly visible change in the structure of neutrophils.
Increasing the number of eosinophils (eosinophilia) occurs when allergies, helminths (worm infestations) and at the stage of recovery from infectious diseases.
Lymphocytosis is typical of pertussis infection mononuleoza, diseases of the blood system. Monocytosis occurs in tuberculosis, syphilis, brucellosis, viral infections.
Reducing the number of leukocytes in the blood is called leukopenia. Leukopenia may occur as a result of exposure to certain medications, diseases of the blood system, systemic lupus erythematosus, rheumatoid arthritis, salmonellosis
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and some other diseases. Contribute to the development of leukopenia alcoholism and diabetes
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.
White blood cells carry out the many and very complex function of immunity, some members of which have not been studied.
Galina Romanenko
