Immunity

• Active immunity


  Acquired when an antigen enters the body triggering a specific immune response (antibodies are produced)
• Active immunity


  • Can be naturally acquired through exposure to microbes or artificially acquired through vaccinations
  • The body produces memory cells, along with plasma cells, giving the person long-term immunity
• Primary response to a pathogen (natural) or to a vaccination (artificial)

  Antibody concentration in the blood takes one to two weeks to increase
• If the body is invaded by the same pathogen again or by the pathogen that the person was vaccinated against


  During the secondary response, the antibody concentration in the blood takes a much shorter period of time to increase and is higher than after the vaccination or first infection
• Passive immunity


  Acquired without an immune response, antibodies are not produced by the infected person
• Passive immunity


  • As the person's immune system has not been activated, there are no memory cells that can produce antibodies in a secondary response
  • If a person is reinfected they would need another infusion of antibodies
• Artificial passive immunity


  People are given an injection/transfusion of the antibodies, e.g. antitoxin for tetanus
• Natural passive immunity


  • Foetuses receive antibodies across the placenta from their mothers
  • Babies receive the initial breast milk from mothers (the colostrum) which delivers a certain isotype of antibody (IgA)
• Features


  • Active
  • Passive
• Production of antibodies


  • Are produced by the body
  • Not produced by the body
• Time before antibodies appear in blood

  • 1-2 weeks
  • immediate
• Presence of memory cells

  • yes
  • no
• Induced by


  • Natural exposure to pathogen
  • Artificial vaccination
  • Antibodies received from another organism (e.g. via the placenta or colostrum/breast milk)
  • Antibodies manufactured and injected or transfused into organism (e.g. monoclonal antibodies delivered by blood transfusion)