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Neutrophils
Last reviewed: 05.07.2025
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Neutrophilic granulocytes (neutrophils) are characterized by the presence of two types of granules in the cytoplasm: azurophilic and specific, the contents of which allow these cells to perform their functions. Azurophilic granules, which appear at the myeloblast stage, contain myeloperoxidase, neutral and acid hydrolases, cationic proteins, and lysozyme. Specific granules, which appear at the myelocyte stage, contain lysozyme, lactoferrin, collagenase, and aminopeptidase. Approximately 60% of the total number of granulocytes are in the bone marrow, constituting the bone marrow reserve, 40% in other tissues, and only less than 1% in the peripheral blood.
Normally, the blood contains segmented neutrophils and a relatively small number of band neutrophils (1-5%). The main function of neutrophils is to protect the body from infections, which is carried out mainly through phagocytosis. The half-life of neutrophilic granulocytes in the blood is 6.5 hours, then they migrate to tissues. The lifespan of granulocytes in tissues depends on many factors and can range from several minutes to several days.
Leukocytosis (leukopenia) is not characterized by a proportional increase (decrease) in the number of leukocytes of all types; in most cases, an increase (decrease) in the number of one type of cells is detected, therefore the terms "neutrophilia", "neutropenia", "lymphocytosis", "lymphopenia", "eosinophilia", "eosinopenia", etc. are used.
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