Infection and Immunity - Essay Example

Download file to see previous pages This essay is being carried out in order to establish a clear understanding of the functionalities of phagocytes and phagocytosis, as applied to these cells and to normal body processes. Body Phagocytes are crucial cells in the fight against infection and in ensuring immunity against harmful bacteria and viruses. Phagocytes are very much developed among vertebrates and with every litre of blood, about six billion phagocytes are present (Mayer, 2006). These cells have first been discovered by Ilya Mechnikov in 1882 during his study of starfish larvae, and throughout the years, other discoveries on this cell have been made and developed by other scientists (Mayer, 2006). Aside from humans and vertebrates, phagocytes are also seen in other species, with some amoebae portraying behaviour very much like macrophage phagocytes, thereby, suggesting that phagocytes are apparent very early on in the development of living things (Janeway, 2001). Phagocytes may either be professional or non-professional based on how effective they are during phagocytosis. The professional phagocytes include the neutrophils, monocytes, macrophages, dendritic cells, and mast cells, and these cells have receptors which are highly sensitive to harmful objects or cells, including bacteria that are not normally part of the body (Ernst and Stendahl, 2006). These phagocytes are needed to fight infections and help maintain healthy cells by removing dead or dying cells (Robinson and Babcock, 1988). Where infection is present, chemicals attract the phagocytes to areas where infection is already present (Ernst and Stendahl, 2006). The chemicals may be from the bacteria itself or from the phagocytes themselves. As soon as these phagocytes come in contact with bacteria, the receptors on the surface of the phagocyte bind to them, causing the bacteria to be engulfed by the phagocyte (Janeway, 2001). The phagocytes then kill the bacteria through oxidants and nitric oxide (Fang, 2004). After the process of phagocytosis, the macrophages and dendrites usually take part in antigen presentation, where the phagocyte brings back the ingested materials to the surface. Such material is available to other cells in the immune system. The phagocytes also traverse the body’s lymph nodes where the material is displayed to the lymphocytes (Fang, 2004). These activities and processes are crucial to securing immunity. Phagocytosis involves activities, drawing out bacteria, parasites, as well as dead cells (Janeway, 2001). It takes place when bacteria or other foreign bodies bind to the receptors on the surface of phagocytes. Such phagocytes then elongate and stretch in order to engulf the bacteria or foreign object. This process usually takes place within nine minutes (Hampton, 1994). As soon as the foreign material is in the phagocyte’s phagosome, the material cannot anymore get out (Hampton, 1994). The phagosome merges with the lysosome or any granule and form into a phagolysosome. Moreover, the bacterium is also made to undergo various killing processes and in a few minutes is already dead (Hampton, 1994). Phagocytosis can take hours for dendrites and macrophages as macrophages are usually slow and untidy eaters, often regurgitating some of the materials into the system. Such undigested materials often trigger more phagocytes to engulf excess materials (Sompayrac, 2008). The phagocytes, in contrast, are ...Download file to see next pages Read More