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Phagocytosis

Bound pathogen is surrounded by a membrane, forming the phagosome which becomes acidified. Lycososomes containing enzymes, proteins and peptides fuse with the phagosome to form the phagolysosome. Upon phagocytosis, macrophages and neutrophils produce toxic products which are directly toxic to bacteria. Pathogenic microbes must either avoid engulfment, grow inside the phagosome (as do mycobacteria) or grow a thick polysaccharide capsule not recognized by any phagocyte receptor.

  1. Foreign microbe attaches to pseudopods on the surface of a phagocyte. Pseudopods are long extensions of the cell, like arms.
  2. The phagocyte's cellular membrane engulfs the microbe to forma phagosome organelle which floats into the cytoplasm.
  3. The phagosome fuses with a lysosome organelle which contains the toxic chemical and enzymes (such as H2O2, O2- and NO).
  4. Lysosomal contents digest the captured microbe; the phagolysosome refuses with the phagocyte cellular membrane to release its contents into surrounding tissue.
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