What Is the Role of Phagocytic Leukocytes?
The immune system consists of a variety of cells, tissues and organs that work together to protect the body from foreign invaders (such as bacteria and viruses) and rid the body of dead or damaged cells. The white blood cells, or leukocytes, are the primary cells of the immune system. There are five different types of leukocytes. Each type performs a specific role in the immune response.
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Phagocytic Leukocytes
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The term "phagocyte" literally means "eating cell." Phagocytic leukocytes are white blood cells responsible for finding, engulfing and digesting microorganisms, foreign substances, abnormal cells, cellular debris and waste products. They are basically the body's garbage collectors. There are two types of phagocytic leukocytes; neutrophils and macrophages.
Neutrophils
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Neutrophils are the most abundant type of white blood cell in the body and are often referred to as the first line of defense, particularly against bacteria. Neutrophils contain granules that contain digestive enzymes. When bacteria enter the body, the bone marrow responds by releasing neutrophils into the bloodstream in large numbers. Once the cells reach the site of infection, they engulf and digest foreign substances. The pus that accompanies an infection consists primarily of dead neutrophils.
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Macrophages
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Macrophages also ingest foreign substances, including bacteria, parasites and tumor cells. If fighting an infection was a race, the neutrophils would be the sprinters and the macrophages would be the long-distance runners. Although macrophages are not as quick to respond to infection, they are larger, can consume more and live longer than neutrophils.
Unlike neutrophils, which are found circulating in the blood, macrophages are present in the body's tissues. In addition to being "big eaters," macrophages also send out chemicals that alert the rest of the immune system of the foreign intrusion.
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