Immunity and Vaccines

  • Created by: Alice1425
  • Created on: 09-05-19 14:44
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  • Immunity and Vaccines
    • Vaccines can protect individuals and populations against disease
      • they contain antigens that cause your boy to produce memory cells against a pathogen without it causing disease
        • you become immune without developing any symptoms
        • Reduce the occurrence of a disease, therefore those not vaccinated are also less likely to catch it
          • "Herd immunity"
        • antigens may be free or attached to dead or attenuated pathogen
      • can be injected
      • can be taken orally
        • could be broken down by enzymes in the gut
        • vaccine molecules may be too large to be absorbed into the blood
      • sometimes booster vaccines given to make sure memory cells are produced
    • Antigenic variability helps some pathogens evade the immune system
      • Surface antigens activate primary response
        • when infected a second time, same pathogen (with same antigen) activates secondary response so you don't get ill.
        • Some pathogens change surface antigens
          • "antigenic variation"
          • formed due to changes in the genes of the pathogen
          • memory cells do not recognise the new antigen
            • immune system starts again and carries out primary response
              • takes time, you get ill again
          • e.g  HIV & Inflenza
            • influenza vaccine changes ever year
              • surface antigens change regularly, producing new strains
                • Memory cells from one vaccination will not recognise new strains
                  • new vaccine is developed every year, government and health authorities implement a vaccination programme using the most suitable vaccine
      • Makes it difficult to develop vaccines against some pathogens
    • immunity can be active or passive
      • Active immunity
        • takes a while for protection to develop
        • type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen
          • Natural
            • becoming immune after catching a disease
          • artificial
            • Becoming immune after being vaccinated with a harmless dose of antigen
        • requires exposure to the antigen
        • memory cells are produced
        • Protection is long term because the antibody is produced in response to complementary antigen being present in the body
      • Passive immunity
        • the type of immunity you get from being given  antibodies made by a different organism (your immune system doesn't make them on its own
          • Natural
            • when a baby becomes immune due to antibodies received from their mother (placenta and breast milk)
          • Artificial
            • when you become immune after being injected with antibodies from someone else
              • e.g if you contract tetanus, you can be injected with antibodies against the tetanus toxin, collected from blood donations
        • doesn't require exposure to antigen
        • protection is immediate
        • memory cells not produced
        • protection is short term because antibodies are broken down


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