In a general blood test, the leukocyte formula is necessarily calculated , that is, the percentage of different classes of leukocytes in the blood. Most of the white blood cells in an adult in the formula are segmented neutrophils (about 70%). They are their main part.
White blood cells are divided into two main series: granulocytes (granular) and agranulocytes (not having granularity). Granulocytes, in turn, are divided into neutrophils, eosinophils and basophils. Each type of cell has a specific granularity in the cytoplasm and performs its special functions.
All cells of the granulocyte series in their development go through developmental stages from myeloblast, through a series of intermediate immature cells, to stab and segmented white blood cells. This applies to all three types of granulocytes - neutrophils, eosinophils and basophils. In peripheral blood, normally only neutrophils can be found stab and segmented. Younger cells enter the bloodstream from the bone marrow only in severe diseases.
Band and segmented neutrophils differ in the shape of the cell nucleus. The first has an even core, similar to a curved stick. In the second, the core is divided by special constrictions into several (2-4) segments. The cytoplasm of the cells is pink. It has fine brown granularity. In infectious diseases, neutrophil granularity becomes larger and bluer (the so-called toxigenic granularity). This is one of the signs of the inflammatory process.
The function that band and segmented neutrophils perform in the body is to protect against foreign particles, viruses, fungi and bacteria. Granulocytes have phagocytic activity. Their granules contain a specific enzyme, myeloperoxidase, which enhances the action of antibacterial substances. Neutrophils can actively move to the site of inflammation.
The ratio of segmented neutrophils and other cells in the leukocyte formula corresponds to age norms. So, in children under 5 years old, lymphocytes predominate, and neutrophils do not exceed 30%. The number of stab neutrophils is normally 1-6%. An increase in the number of neutrophils accompanies various diseases and is called neutrophilia.
Neutrophilia usually accompanies a general increase in white blood cell count. At the same time, stab neutrophils are also elevated . Sometimes immature cells appear in the bloodstream in severe diseases - metamyelocytes (young) and myelocytes. An increase in the number of stab cells, the appearance of metamyelocytes and myelocytes is called a shift of the leukocyte formula to the left. Often, a shift in the formula is combined with the appearance of toxigenic granularity in stab and segmented neutrophils and basophilia of their cytoplasm.
Such changes in neutrophils are accompanied by acute inflammatory diseases, shock conditions, heart attack, various intoxications. The shift of the formula to the left is especially pronounced in chronic myelocytic leukemia. With this disease, segmented neutrophils are sharply reduced both in percentage and in absolute terms. The formula is dominated by stab and immature cells. A decrease in the number of segmented neutrophils leads to a decrease in the protective function of leukocytes . This threatens the accession of various infections.
A decrease in segmented as well as stab neutrophils is called neutropenia. It is usually observed against a background of a general decrease in white blood cells. This condition occurs in chronic and viral infections, often after taking cytostatics, after radiation therapy, with blood diseases such as agranulocytosis or aplastic anemia.
Thus, the role of segmented neutrophils is to protect a person from infections. In diseases, their number is compensatingly increasing. This is expressed in a change in the ratio of cells in the blood formula.