Phagocytes are white blood cells that perform phagocytosis, which is the engulfing, absorption, and destruction of pathogenic microorganisms, cancer cells, and protein particles. There are three types of phagocytic cells: 1) the neutrophil, which is a granulocyte that intercepts and kills bacteria; 2) mononuclear phagocytes, which include the monocyte and macrophage; 3) organ-specific phagocytes, which are found in the liver, spleen, lymph nodes, lungs, and brain.
The organ-specific phagocytes have different names, according to the organs and systems in which they are found. For example, in the brain, they are called microglia; and, in the liver, they called Kupffer cells. These are ¨fixed¨ phagocytes, meaning that these cells do not move around throughout the organ but they are rather disseminated (scattered) everywhere in the tissue of the parenchyma. A well-known mononuclear phagocyte, the macrophage, operates separately from the immune system, clearing cellular debris (remnants of dead cells, which usually dies from apoptosis).
Phagocytic cells engulf bacteria and cell particles in the same way amoeba eats. A bacterium or cell particle gets surrounded by cytoplasmic extensions, which are called pseudopods. These extensions derive from the plasma membrane and release enzymes, which kills and break down the pathogenic cell or particle.
