What are the functions of neutrophils

Many people don’t know what neutrophils are. In fact, neutrophils are a type of hematopoietic stem cell derived from the bone marrow. Although many people do not understand neutrophils, the role of neutrophils cannot be ignored. Neutrophils play a defensive role in fighting infection.

1. Neutrophils have a strong chemotactic effect

Chemotaxis is the movement of cells toward the direction stimulated by a chemical substance. Substances that have a chemotactic effect on neutrophils are called neutrophil chemotactic factors. There are chemokine receptors on the cell membrane of neutrophils. The receptors bind to chemokines, activating the calcium pump on the cell membrane. The cell extends its lamellae forward, causing the cell to move toward the site where the chemokine is produced.

2. Eliminate bacteria

Neutrophils play a very important role in the nonspecific cellular immune system of the blood. They are at the front line of the body's defense against microbial pathogens, especially against the invasion of purulent bacteria. When inflammation occurs, they are attracted to the site of inflammation by chemotactic substances. Because they obtain their energy through glycolysis, they are able to survive the hypoxic conditions of swelling and poor blood flow, where they form cytotoxic cells that damage the cell membranes of bacteria and nearby tissues. Because neutrophils contain a large amount of lysosomal enzymes, they can break down bacteria and tissue fragments that have been engulfed into the cells. In this way, the invading bacteria are surrounded in a local area and eliminated, preventing the spread of pathogenic microorganisms in the body. When the neutrophils themselves disintegrate, the release of lysosomal enzymes can dissolve the surrounding tissue to form an abscess.

3. Others

When neutrophils are acted upon by bacterial products, antigen-antibody complexes, etc., the contents of their granules are released outside the cells. The released acidic proteases and neutral proteases can decompose the vascular basement membrane, glomerular basement membrane, collagen and elastin of connective tissue, as well as complement C5, C15 and kininogen in plasma. Some of its decomposition products are neutrophil chemotactic factors, which can attract more neutrophils. The substances released by neutrophils include eosinophil chemotactic factor, neutrophil immobilization factor (NIF), kininogen, plasminogen, coagulation factors, leukotrienes, etc.

In addition to playing an important defensive role in anti-infection, neutrophils can cause inflammatory responses at the site of infection and participate in allergic reactions triggered by parasitic infections, thereby causing immunopathological damage. Antibodies act directly on antigens on tissues or cells, and neutrophils bind to antigens on the surface of target cells through their Fc receptors.