Immunity

• Immunity


  Based on recognition of self and destruction of foreign material
• Every organism has unique molecules on the surface of its cells
• Pathogens


  Can be species-specific although others can cross species barriers
• B lymphocytes


  Are activated by T lymphocytes in mammals
• Activated B cells


  1. Multiply to form clones of plasma cells and memory cells

  2. Plasma cells secrete antibodies

  3. Antibodies aid the destruction of pathogens
• White cells


  Release histamine in response to allergens
• Histamines


  Cause allergic symptoms
• Immunity


  Depends upon the persistence of memory cells
• Vaccines


  Contain antigens that trigger immunity but do not cause the disease
• Hybridoma cell


  Fusion of a tumour cell with an antibody-producing plasma cell
• Monoclonal antibodies


  Produced by hybridoma cells
• Smallpox


  • First infectious disease of humans to have been eradicated by vaccination
• Monoclonal antibodies to HCG

  • Used in pregnancy test kits
• Antigens on the surface of red blood cells stimulate antibody production in a person with a different blood group
• Vaccination


  1. Initiates a primary immune response

  2. Results in the production of memory cells

  3. Allows an individual to become immune to a disease without experiencing it
• Forms of antigens in vaccines

  • Attenuated (weakened) or inactivated viruses
  • Weakened toxins (produced by bacterial pathogens)
  • Subunits - the antigen or part of the pathogen carrying the antigen
• Vaccines provide long-term immunity, but memory cells may not survive a life time therefore booster shots may be required
• Smallpox was the first infectious disease of humans to have been eradicated by vaccination
• Cowpox is a mild viral infection of cows, which is very similar to smallpox
• In 1796 Edward Jenner deliberately infected an eight-year old boy with cowpox from pocks/blisters of a milkmaid with this disease
• Jenner repeated his initial experiment on himself and a small group of people
• Jenner then attempted to infect the boy with smallpox, but found that he was immune
• Nature of science: Consider ethical implications of research - Jenner tested his vaccine for smallpox on a child
• Zoonosis


  Any disease or infection that is naturally transmissible from vertebrate animals to humans
• Examples of pathogens


  • Polio, Measles and Syphilis only affect humans
  • Flu, Ebola and Salmonella can be transmitted between humans and other animals
• Hybridoma


  Fusion of a tumour cell with an antibody-producing plasma cell
• Production of monoclonal antibodies

  1. Animal injected with antigen produces specific plasma cells

  2. Plasma cells harvested from animal spleen

  3. Harvested plasma cells fused with tumor cells forming hybridoma cells

  4. Hybridoma cells screened to determine which are producing useful antibodies

  5. Selected hybridoma allowed to divide to produce clones

  6. Hybridomas used to synthesise large quantities of a single (monoclonal) antibodies
• Monoclonal antibodies to HCG are used in pregnancy test kits
• Epidemiology


  The study of the incidence, distribution, and possible control of diseases
• Surveillance is critical to the control of Measles
• Most Member States submit monthly reports on suspected and confirmed measles cases identified through their national disease surveillance systems to the WHO
• Despite having an established vaccination program in most countries Europe has seen a peak in Measles incidence between 2010 and 2013