phagocyte

Examples of phagocyte in the following topics:

• Microbial Evasion of Phagocytosis

  • Pathogens have evolved mechanisms to evade capture by phagocytes in the immune system.
  • 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.
  • There are several ways bacteria avoid contact with phagocytes.
  • First, they grow in sites that phagocytes are not capable of traveling to (e.g. the surface of unbroken skin).
  • Bacteria have developed several ways of killing phagocytes.

• Phagocyte Migration and Phagocytosis

  • The phagocyte then stretches itself around the bacterium and engulfs it.
  • Once inside the phagocyte, the bacterium is trapped in a compartment called a phagosome.
  • This debris serves as a signal to recruit more phagocytes from the blood.
  • All phagocytes, and especially macrophages, exist in degrees of readiness.
  • Chemotaxis is the process by which phagocytes follow the cytokine "scent" to the infected spot.

• Phagocytes

  • Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles and help initiate an immune response.
  • Most phagocytes are derived from stem cells in the bone marrow.
  • The main types of phagocytes monocytes, macrophages, neutrophils, tissue dendritic cells, and mast cells.
  • Phagocytes derive from stem cells in the bone marrow.
  • Describe the types of phagocytes and their role in initiating an immune response

• Direct Damage

  • Phagocytosis is a process utilized by phagocytes (white blood cells) as a defense mechanism to protect from foreign bodies.
  • The phagocytes engulf invaders and present them to additional factors within the immune system that result in their destruction.
  • Pathogens that exhibit the ability to avoid contact utilize various processes to accomplish this, including: the ability to grow in regions of the body where phagocytes are incapable of reaching; the ability to inhibit the activation of an immune response; inhibiting and interfering with chemotaxis which drives the phagocytes to site of infection; and 'tricking' the immune system to identify the bacteria as 'self. ' Additional mechanism(s) by which bacteria can avoid destruction is by avoiding engulfment.
  • This is accomplished by the ability of the bacteria to exhibit produce molecules that interfere with the phagocytes ability to internalize the bacteria.

• Type IV (Delayed Cell-Mediated) Reactions

  • Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
  • Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells.

• Whooping Cough

  • The end result is that phagocytes convert too much ATP to cyclic AMP, which can cause disturbances in cellular signaling mechanisms.
  • This prevents phagocytes from correctly responding to an infection.

• Neuroglia of the Peripheral Nervous System

  • They also perform phagocytic functions and clear cellular debris, allowing for the regrowth of PNS neurons.

• The Complement System

  • The complement system helps or "complements" the ability of antibodies and phagocytic cells to clear pathogens from an organism.
  • The complement system helps or "complements" the ability of antibodies and phagocytic cells to clear pathogens from an organism.
  • C3b binds to the surface of pathogens, leading to greater internalization by phagocytic cells by opsonization.

• Cells and Organs of the Immune System

  • The innate leukocytes include the phagocytes, mast cells, eosinophils, basophils, and natural killer cells.
  • Neutrophils and macrophages are phagocytes that travel throughout the body in pursuit of invading pathogens.
  • Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte.
  • Dendritic cells are phagocytes in tissues that are in contact with the external environment, and are located mainly in the skin, nose, lungs, stomach, and intestines.

• WBC Function

  • The antibodies bind to pathogens to opsonize (mark) them for phagocytes to engulf, neutralize them, or start a complement cascade in which proteins form a membrane attack complex to lyse the pathogen.