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How White Blood Cells Work

The white blood cells are an important part of our body's immune system. Neutrophils are a special group of white blood cells that play an extremely important role in protecting the body against infections. Mature neutrophils do not divide. New neutrophils are constantly formed in the bone marrow where they develop and mature. Mature neutrophils are released into the blood where they circulate for 3 to 12 hours and then move to other tissues, where they survive only 2 to 3 days. These mature neutrophils can be found in large and small blood vessels, as well as in the tiny capillaries in different tissues. In the bloodstream, neutrophils act as surveillance cells searching for infections. Neutrophils can sense a site of infection because of chemicals that are released by the bacteria. Upon detecting these chemicals, neutrophils slow down and begin to stick to the walls of the blood vessel. They then squeeze between the cells of the blood vessel wall and enter the infected tissue. Here, the neutrophils crawl towards the infection as they continue following the chemical signals. At the site of infection, bacteria are coated with antibodies of the immune system and marked for ingestion. The neutrophil recognizes the marked bacterium, engulfs it into its body, ... And traps the bacterium in a sac called a phagosome. The neutrophil contains pouches called lysosomes, which are full of digestive enzymes and chemicals that can kill bacteria. The pouches or lysosomes then combine with the phagosomes containing the bacteria and release the enzymes and chemicals, ... Resulting in the ultimate death of the bacterium inside the neutrophil. After killing and digesting the bacteria, the neutrophil is spent. Having completed its duty, the neutrophil shrinks in size and breaks up into smaller pieces that can be recognized and eaten by other cells.