phagocytosis

Examples of phagocytosis in the following topics:

• Phagocyte Migration and Phagocytosis

  • Phagocytosis is the engulfment of foreign material in a body by a specialized cell type.
  • Phagocytosis is the process by which a cell takes in particles such as bacteria, parasites, dead host cells, and cellular and foreign debris.
  • Phagocytosis of bacteria by human neutrophils takes on average nine minutes to occur.
  • Dendritic cells and macrophages, on the other hand, are not so fast, and phagocytosis can take many hours in these cells.
  • Their size and rate of phagocytosis increases—some become large enough to engulf invading protozoa.

• Direct Damage

  • The ability to manipulate the process of phagocytosis is a mechanism often utilized by bacteria to ensure they effectively invade a host.
  • Phagocytosis is a process utilized by phagocytes (white blood cells) as a defense mechanism to protect from foreign bodies.
  • However, a successful and destructive pathogen often exhibits the ability to evade phagocytosis.
  • The mechanism(s) utilized by pathogens to avoid phagocytosis include avoiding both contact and engulfment.
  • Staphylococcus aureus exhibit physical properties, specifically a capsule, that protect the bacteria from phagocytosis.

• Microbial Evasion of Phagocytosis

  • Pathogenic bacteria and protozoa have developed a variety of methods to resist attacks by phagocytes (phagocytosis), and many actually survive and replicate within phagocytic cells.
  • Bacteria often produce proteins or sugars that coat their cells and interfere with phagocytosis; these are called capsules.
  • These include cytolysins which form pores in the phagocyte's cell membranes, streptolysins and leukocidins which cause neutrophils' granules to rupture and release toxic substances, and exotoxins which reduce the supply of a phagocyte's ATP, needed for phagocytosis.

• Endocytosis

  • Phagocytosis (the condition of "cell eating") is the process by which large particles, such as cells or relatively large particles, are taken in by a cell.
  • In preparation for phagocytosis, a portion of the inward-facing surface of the plasma membrane becomes coated with a protein called clathrin, which stabilizes this section of the membrane.
  • Pinocytosis results in a much smaller vesicle than does phagocytosis, and the vesicle does not need to merge with a lysosome .
  • In receptor-mediated endocytosis, as in phagocytosis, clathrin is attached to the cytoplasmic side of the plasma membrane.
  • In phagocytosis, the cell membrane surrounds the particle and engulfs it.

• Phagocytes

  • Phagocytosis is the process by which a phagocyte engulfs a pathogen or debris.
  • Typical phagocytosis occurs over the course of a few steps:
  • These are the general mechanisms used by phagocytosis to engulf and kill pathogens, but some variations can occur.
  • There are many classes of phagocytes within the body, each with different specialized functions involving phagocytosis.
  • Neutrophils die after phagocytosis, becoming pus that is later cleaned up by macrophages.

• Sea Coral and Sea Anemone Zooxanthellae

  • Generally, these dinoflagellates enter the host cell through phagocytosis, persist as intracellular symbionts, reproduce, and disperse to the environment (note that in most mollusks, Symbiodinium are inter- rather than intra-cellular).
  • Each Symbiodinium cell is coccoid in hospite (living in a host cell) and surrounded by a membrane that originates from the host cell plasmalemma during phagocytosis.

• Macrophages

  • Phagocytosis is a front-line defense against pathogen attack requiring the concerted action of macrophages.

• Glycocalyx

  • The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (i.e. prevents phagocytosis).
  • A capsule-specific antibody may be required for phagocytosis to occur.

• WBC Function

  • Phagocytosis of pathogens.
  • Following phagocytosis, protein components (antigens) of the pathogen are expressed on leukocyte MHC molcules and are presented to naive T cells (and B cells) in the lymph nodes.

• Cell Structure, Metabolism, and Motility

  • Amoebas and some other heterotrophic protist species ingest particles by a process called phagocytosis in which the cell membrane engulfs a food particle and brings it inward, pinching off an intracellular membranous sac, or vesicle, called a food vacuole .
  • The stages of phagocytosis include the engulfment of a food particle, the digestion of the particle using enzymes contained within a lysosome, and the expulsion of undigested materials from the cell.