Non specific defences (2)

Inflammatory response
1. Localised response to pathogens
2. Characterised by pain, heat, redness and swelling
3. Mast cells are activated in damaged tissue and release chemicals called histamines and cytokines
  1. Histamines make blood vessels dilate, causing localised heat and redness. The increased temp helps denature proteins and prevent pathogens reproducing
  2. Histamines make blood vessel walls more leaky so plasma is forced out and then becomes tissue fluid. This causes oedema and pain
  3. Cytokines attract WBC to site and then phagocytosis occurs
Fevers
1. Cytokines stimulate hypothalamus to reset the thermostat and temp increases.
2. Most pathogens reproduce best at 37C or below so they are inhibited by higher temps
3. Specific immune system works faster at higher temps
Phagocytosis
1. Where phagocytes attack pathogens. Pus = dead neutrophils and pathogens
2. 1) The Phagocyte is attracted to the pathogen by Chemo-attractants. It moves towards the pathogen along a concentration gradient
3. 2) The phagocyte binds to the pathogen
4. 3) Lysosomes within the Phagocyte migrate towards the Phagosome formed by engulfing the bacterium, creating phagolysosome
5. 4) Lysosomes release lytic enzymes into Phagosome, breaking down the bacterium
6. 5) The breakdown products of the bacterium are absorbed by the phagocyte - antigens and combine with MHC in cytoplasm
7. 6) MHC / Antigen complex is displayed on phagocyte membrane and makes an antigen presenting cell
8. Takes a neutrophil ~10 mins to engulf and destroy bacteria
  1. Macrophages take longer cause they undergo a more complex process
    1. When a macro has digested a pathogen, it combines antigens from the pathogen surface membrane and glycoproteins in the cytoplasm (MHC).
      1. MHC complex moves pathogens antigens to the macros surface membrane, making it an antigen presenting cell.
        Stimulate other cells involved in specific immune system response
9. Phagocytes that have engulfed pathogens produce cytokines which act as cell - signalling molecules. Informing the other cells that the body is under attack and stimulating them to move to infection.
  1. Cytokines increase body temp and stimulate specific immune system
10. Opsonins bind to pathogens and tag them so they can be easily recognised by phagocytes. Phagocytes have receptors on their membranes that bind to common Opsonins and the phagocyte engulfs the pathogen.
  1. Different Opsonins include: immunoglobulin G and M which are strongest

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Non specific defences (2)

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	Created by Jess Hughes almost 8 years ago