see also:

• immunology

• 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

• 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

• 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

• see inflammation
• 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
• 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⁾

• mainly activated in response to invading extracellular organisms
• see complement