non specific immune responses

• phagocytosis:

  • often seen in association with inflammation
  • involves two groups of blood cells (neutrophils and macrophages)
  • sometimes seen in pus
  • engulphs + ingests pathogens
• inflammation:

  • often occurs when infection is localised
  • when tissue is damaged, mast cells and damaged white blood cells release histamine
  • more widespread infection causes inflammation in the form of a rash
  • histamine promotes tissue changes
• interferon:

  • when cells are invaded, they produce interferons
  • an interferon diffuses from the cell where it is made into the surrounding cells
  • then it binds to receptors in the cell surface membrane of uninfected cells
  • this stimulates a pathway which makes the cell resistant to infection by viruses, by stopping them reproducing
  • this prevents the infection of more cells when the virus breaks out of the first cell
• fever:

  • when a pathogen invades, the hypothalamus sets up a higher running body temperature
  • this reduces the pathogens ability to reproduce quickly
  • the specific response systems work better at higher temperatures, so will be more successful at fighting infection
  • in viral infection, the temperature often spikes very high when the viruses burst out of the cell and then drops again
  • fevers are damaging, and can be fatal
• histamines:

  • released by mast cells/damaged white blood cells
  • causes blood vessels to dilate, causing local heat and redness
  • locally raised temperatures reduces pathogen reporduction
  • they make the wall of the capillaries leaky, forcing plasma, white blood cells and antibodies out of the capillaries