Neutrophils in Richter-stained blood smears have a colorless or very pale light red cytoplasm with many diffusely distributed fine (0, 2 to 0, 4 microns) light red or light purple characteristic granules. The nucleus is rod-shaped or 2-5 lobed, with thin filaments connecting the leaves to each other. Its granule surface is wrapped with a membrane and can be divided into 1 to 4 types. The granules contain myeloperoxidase, acid phosphatase, phagocytosis, lysozyme, β-glucosidase, alkaline phosphatase, etc. Neutrophils have chemotactic, phagocytic and bactericidal effects. 1. Causes of low neutrophils 1. Gram-negative bacillary infections, such as typhoid and paratyphoid fever. 2, some viral infections, such as influenza virus. 3. Chronic physical and chemical injuries, long-term exposure to lead, mercury, benzene, etc.; certain drugs such as chloramphenicol and heparin; patients receiving long-term radiation and radiotherapy. 4.Systemic lupus erythematosus and other autoimmune diseases. 5.Aplastic anemia (reblocking) and other blood diseases. 6, hypersplenism, hyperthyroidism (hyperthyroidism). 7.Some parasitic diseases such as malaria and black fever. Low neutrophils can lead to bone marrow hypoplasia, bone marrow invasion (leukocyte hyperplasia of oligodendrocytes, partial myeloid leukemia), viral infections, typhoid fever, paracrine fever, certain parasitic diseases (malaria, black fever), hyperthyroidism, hypersplenism, Waldenstrom’s disease, multiple myeloma, Felty’s syndrome, anemia (iron deficiency, folic acid deficiency, vitamin B12 deficiency), radiation (e.g., localization therapy), granulocyte deficiency (poisoning: piramiphos-methyl, phenothiazine, pautazone, antithyroid drugs, etc.; immuno-immunopathic diseases; systemic diseases). Third, what to do with low neutrophils Generally, neutrophils are derived from hematopoietic stem cells of the bone marrow, which differentiate and develop in the bone marrow and enter the blood or tissues. The number of distribution in the bone marrow, blood and connective tissue is 28:1:25, and the number of neutrophils in the blood of adults accounts for about 55% to 70% of the total number of white blood cells. Neutrophils are a type of polymorphonuclear leukocyte, and because they are the most numerous of the granulocytes, some people refer to polymorphonuclear leukocytes as neutrophils. This cell contains many diffusely distributed fine light red or light purple characteristic granules, which contain myeloperoxidase, acid phosphatase, phagocytosis, lysozyme, etc. Myeloperoxidase is unique to neutrophils and is rarely or completely absent even in macrophages, which have a strong phagocytic effect. In cytochemistry, this myeloperoxidase is generally used as a marker of neutrophils. Neutrophils are highly chemotactic. By chemotaxis, we mean that the cells move in the direction of a certain chemical stimulus. The substance that acts as a chemotactic agent for neutrophils is called neutrophil chemotactic factor. Neutrophils have chemokine receptors on their membranes, which bind to the chemokine and activate the calcium pump on the cell membrane, and the cell extends its lamellar foot forward, causing the cell to move toward the site of chemokine production.