Vaccine

• Describe how a vaccine can lead to protection against specific bacteria 


  Antigen on surface of bacterium binds to surface receptor on a specific B cell. Activated B cell divides by mitosis to produce clones; Division stimulated by specific T helper cells; B plasma cells release antibodies; Some B cells become memory cells; upon re-exposure to the pathogen-memory cells produce plasma cells and therefore antibodies faster and in greater volumes.
• why is it better to have a variety of antigens from the same pathogen in a vaccine 


  Contains a greater range of antigens; Each antigen causes its own immune response and so the production of a range of specific antibodies directed against different antigens on the same pathogen
• describe how a vaccine leads to the production of antibodies against a disease causing organisms 


  Vaccine contains antigen from pathogen; Phagocyte presents antigen on its surface; T cell with complementary receptor protein binds to antigen; T helper cell stimulates specific B cell; With complementary antibody on its surface; B cell divides to form cloned plasma cells all producing and secreting same antibody; B cell secretes large amounts of antibody;
• Give an example of natural and artificial active immunity and an example natural and artificial passive immunity 


  passive:

  Natural= antibodies given to foetus by the mother

  Artificial= injected with antibodies

  Active:

  Natural=exposure to a pathogen followed by an immune response

  Artificial = vaccination
• compare and contrast active and passive immunity 


  Active involves memory cells, passive does not; Active involves production of antibody by plasma cells and memory cells;

  Passive involves antibody introduced into body from an outside source; Active is long term, because antibody produced in response to antigen; Passive short term,
• what is vaccination


  injection of antigens Antigen from attenuated microorganism or dead microorganism stimulates the formation of memory cells
• what is meant by herd immunity 


  when unvaccinated individuals in a population are protected because most of the population is vaccinated so the spread of the pathogen is much reduced