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  • immunity
    • non specific response
      • always works in the same way regardless of the pathogen
      • many are barriers
      • make up our primary defence mechanisms
      • skin
        • made up of protein heratin effective barrier against pathogens
      • mucus membrane
        • goblet cells and ciliated epithelium to trap and remove pathogens
      • stomach acid
        • PH2 destroys pathogens entering, enzymes and proteins denatures by low PH
      • tear ducts
        • secrete substances containing enzymes to break down bacteria
    • second line of defence
      • phagocytosis
        • neutrophils and monocytes
          • engulf and digest non self particles ' bacteria and viruses'
        • body cells damaged by bacteria etc. release cytokines which will attract phagocytes to the area
        • bacteria will have different surface proteins (antigens) so are recognised as non self
    • inflammation
      • damaged tissues release histamine
      • this causes widening of arterioles in this area
      • causes more blood to flow to that area and increases temp
      • capillaries become more permeable, so more tissue fluid escapes, which causes swelling
      • more phagocytes delivered to the area to deal with any bacteria that could cause infection
    • third line of defence
      • antibodies
        • 4 polypeptide chains, two heavy and two light
        • constant region is the same for all antibiodies
        • variable region different for each type
        • variable region allows antibody to attach to a specific pathogen and destroy it
        • antibodies are quaternary proteins
      • lymphocytes
        • Bl lymphocytes
          • each capable of producing a separate antibody
          • when a pathogen enters the body on type of b lymphocyte will have the receptors matching to the antigens on the pathogens surface, thin takes time to find
          • when the b lymphocyte is found it will divide by mitosis in a process called clonal expansion
          • some become plasma cells (to deal with the pathogen
          • some become memory cells which remain in the body for long periods of time in case the pathogen enters again
        • t lymphocytes
          • cloned t lymphocytes differentiate into three types
            • t killer
              • kill any body cells infected with the virus (release chemicals to show they are damaged)
            • t helper
              • secrete cytokines which carry out cell signalling which stimulates further phagocytes and stimulates b lymphocytes to produce more antibodies and stimulates continued division of t killer cells
            • t supressor
              • nhibit immune response once the pathogen has been dealt with
      • agglutination:hold the bacteria close together so that they clump making it easier for phagocytes to engulf them
      • precipitation:causes soluble antigens on the pathogen to precipitate making them easier to engulf
      • neutralisation:antibodies can bind to the toxins and neutralise them
      • lysis : antibodies can attract enzymes to the pathogen to break them down
      • opsonins attach to the pathogens specific binding site and attach to a phagocyte on the other end which holds it nearer making it easier to engluf
    • primary response is slow because it takes time for clonal selection and expansion
      • secondary response is fast due to memory cells recognising the pathogen
        • leads to immunity


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