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.

• 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.

• Immunoassays for Disease

  • When a foreign agent penetrates the first line of resistance, an immune reaction is elicited and immune cells are recruited into the site of infection to clear microorganisms and damaged cells by phagocytosis.

• Type III (Immune Complex) Reactions

  • The cause of damage is as a result of the action of cleaved complement anaphylotoxins C3a and C5a, which, respectively, mediate the induction of granule release from mast cells (from which histamine can cause urticaria), and recruitment of inflammatory cells into the tissue (mainly those with lysosomal action, leading to tissue damage through frustrated phagocytosis by polymorphonuclear neutrophils and macrophages).
  • After an antigen-antibody reaction, the immune complexes can be subject to any of a number of responses, including complement deposition, opsonization, phagocytosis, or processing by proteases.

• Immune Complex Autoimmune Reactions

  • After an antigen-antibody reaction, the immune complexes can be subject to any of a number of responses, including complement deposition, opsonization, phagocytosis, or processing by proteases.

• Primary and Secondary Antibody Responses

  • These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.

• The Complement System

  • The following are the basic functions of the complement: opsonization (enhancing phagocytosis of antigens); chemotaxis (attracting macrophages and neutrophils); cell lysis (rupturing membranes of foreign cells); and clumping (antigen-bearing agents).