Granulocytes are the most numerous group of white blood cells, or leukocytes, which are responsible for the immunity of our body. Granulocytes are divided into neutrophils, basophils and eosinophils. The basic test from which one can find out about the total number of leukocytes is the blood count, while the blood count with a smear is more detailed. What exactly is the function of granulocytes and as evidenced by changes in their number?
Granulocytes- bothneutrophils ,basophilsandeosinophils - they have a similar morphology: they are characterized by a multiplate cell nucleus (the number of lobes increases with the cell's age) and granularity in the cytoplasm, their reaction determines whether the granulocyte is eosinophilic, basophilic or neutrophilic. The aforementioned blood count with a smear informs about the number of individual groups of granulocytes and the structure of their nuclei, which proves the age of the cells.
Neutrophils or neutrophils
Among granulocytes, the most numerous group are neutrophils (neutrophils), they are from 1,800 to 8,000 in a microliter of blood, and they account for 60% to 70% of all white blood cells. They stay in circulation for a short time - about 6 hours, then they pass through the vessel wall (the process of transition is diapedesis) and go to other tissues and organs, mainly to the gastrointestinal tract. Bacterial infection of the body stimulates the bone marrow and increases the release of neutrophils, they have the ability to chemotaxis, i.e. they tend to the places where there is the highest concentration of substances secreted by bacteria and plasma factors, such as complement factor C5a, leukotrienes, or polypeptides of other leukocytes.
One of the tasks of neutrophils at the site of infection is a specific way of endocytosis - phagocytosis, that is, the absorption of microorganisms, for it to be possible, it is necessary to opsonize the bacteria first. It involves the attachment of immunoglobulin G and complement factors to the pathogen, thanks to which they are bound to the receptors on neutrophils, and then absorbed and combined with granules containing substances that neutralize microorganisms. Another task of neutrophils is exocytosis at the site of infection, in this process the content of cell granules is released outside in the degranulation process, enzymes such as:defensins, myeloperoxidase, proteases, NADPH oxidase, which produces oxygen free radicals, all of these substances help fight infection.
The increase in the number of neutrophils in laboratory tests may indicate, among others:
- inflammation (e.g. bacterial infections) including autoimmune processes (e.g. rheumatoid arthritis, gout)
- myeloid leukemia when the disease affects granulocyte precursors
A decrease in the number of neutrophils can be observed in the case of, for example :
- aplastic anemia
- acute leukemias, when other blood cells are overproduced, the production of neutrophils is reduced
- viral infections
- chemo- and radiotherapy
Of course, the diagnosis of these diseases is determined by the entire clinical picture and the results of other studies.
Eosinophils or eosinophils
Eosinophils (eosinophils) constitute a much smaller group, their number ranges from 50 to 400 cells / μl of blood, they constitute from 2% to 4% of all white blood cells. Like neutrophils, they are capable of chemotaxis, diapedesis and exocytosis. Their main task is to protect against parasites, therefore the greatest amount of them can be found in the digestive tract, respiratory system and urinary system. Their increased number may be evidence of:
- parasitic infections
- allergic reactions, including medication
- scarlet fever
- lymphomas and leukemias
- skin diseases (e.g. psoriasis)
- chronic inflammatory diseases (e.g. Churg-Strauss disease)
A reduced amount of eosinophilia has been exceptionally observed.
Basophils: basophils
Basophils (basophils) - physiologically it is below 300 / μl and they constitute only 1% of leukocytes. In terms of their functions, they are similar to mast cells that are outside the bloodstream. After stimulation by T lymphocytes, basophils secrete histamine and heparin, the first mediator is responsible for allergic reactions - immediate hypersensitivity reactions, urticaria or anaphylactic shock. We observe an increase in the amount of basophils, among others, in the course of leukemias.
Changes in the number of individual groups of granulocytes may indicate many abnormalities in our body, also dangerous. Variations in the blood smear cannot be underestimated, and knowledge of the functions of neutrophils, basophils and eosinophils makes it much easier to find the cause of incorrect results.