MECHANISM OF PHAGOCYTOSI1 - more susceptible to...

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MECHANISM OF PHAGOCYTOSIS There are four main phases in the process: 1. Chemotaxis---chemical attraction of phagocytes to microbes. The chemicals involved include: Microbial products such as toxins Chemicals released by white blood cells already in the area Chemicals released by damaged tissue cells Complement   2. Adherence---the plasma membrane of the phagocytic cell attaches to the surface of the  microbe or  foreign particle. Attachment can be inhibited by the presence of a well-developed  capsule on the microbe or by special proteins produced by some microbes which coat their  surface (M protein of  Streptococcus pyogenes,  for example).    Organisms whose capsules interfere  with adherence include  Streptococcus pneumoniae  and  Hemophilus influenzae  type b.    Opsonization is the coating of the microbe with certain plasma proteins which make the microbe 
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Unformatted text preview: more susceptible to phagocytosis. Proteins which cause this effect include some of the complement system and antibody molecules. 3. Ingestion---the plasma membrane of the phagocyte extends pseudopods that surround and engulf the microbe. The microbe is brought into the cell enclosed in a sac made of a bit of the cell’s plasma membrane---this is called a phagosome or phagocytic vesicle. 4. Digestion---at this stage, the microbe has not been harmed. The phagocytic cell must now take steps to destroy it. As the phagocytic vesicle moves into the cell, it comes in contact with lysosomes. The membranes enclosing the phagocytic vesicle and the lysosome fuse, forming one larger vesicle called a phagolysosome. The digestive enzymes of the lysosome are able to kill most bacteria within 10 - 30 minutes....
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MECHANISM OF PHAGOCYTOSI1 - more susceptible to...

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