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innate_immunity

innate immunity

see also:

introduction

  • innate immunity is a term used to refer to all types of immunity excluding acquired_immunity (acquired immunity relies upon immune cells such as T-cell and B-cell lymphocytes which produce antibodies and these immune systems arose late in evolution, appearing in vertebrates), and thus is relatively non-specific

innate immune system

anatomical barriers

  • intact skin and mucosa
  • desquamation helps remove bacteria
  • irrigation helps remove organisms
    • eg. tears
  • mucus forms a barrier, traps organisms and allows their expulsion
    • in the respiratory tract, mucus expelled via cilia motility mechanisms remove bacteria and fungi
  • commensal organisms form a normal flora which helps prevent colonisation by more pathogenic flora

mucus

  • an important part of innate immunity is mucus production which forms a barrier to invading organisms
  • mucus consists of mucins which are glycan sugars and recently, it has been discovered a symbiotic relationship exists whereby certain strains of bacteriophage viruses bind to the mucins and reduce binding of bacteria to the mucin by over 10,000 fold, thereby further reducing bacterial invasion.
    • an example is crAssphage which was discovered in 2014 and appears to specifically target Bacteroides sp of bacteria in the gut

the inflammatory response

  • cells involved include:
    • mast cells
    • neutrophils
    • eosinophils
    • basophils
    • macrophages and dendritic cells
    • natural killer cells - mainly target intracellular infections
    • etc
  • mechanisms utilise histamine, cytokines, chemokines, etc
    • identification of bacteria as pathogens by the innate system usually relies upon the presence of lipopolysaccharide coatings on the bacteria which contain 6 acyl chains that are not too long
  • phagocytosis of cells is important for intracellular virus or bacterial infections, and xtracellular bacteria and protozoa, but not useful for fungi or intracellular protozoa
  • coagulation may play a role
  • some bacteria once inside a macrophage can release toxins to stop the functioning of mitochondria and this then triggers the cell to undergo apoptosis 1)

complement system

  • mainly activated in response to invading extracellular organisms
innate_immunity.txt · Last modified: 2021/03/16 08:03 by gary1