Active & Passive Immunity (AQA AS Biology): Revision Note

Types of immunity

Active immunity

• Active immunity occurs when the immune system is stimulated by an antigen to produce antibodies and memory cells

• It can be stimulated:

  • Naturally, from an infection

  • Artificially, from a vaccination

• Active immunity provides long-term immunity due to memory cell formation

• This means if the same antigen is encountered again, there will be a faster and stronger secondary response

Passive immunity

• Passive immunity is when a person receives ready-made antibodies without producing them

• No immune response is triggered, so no memory cells are formed

  • This means that protection is short-term

• Passive immunity is useful when there is no time to wait for an immune response and immediate protection is needed

  • e.g. providing a tetanus antitoxin which contains specific antibodies that bind to the tetanus toxin

• Passive immunity can be:

  • Artificial: where antibodies are introduced via an injection(e.g. antitoxins)

  • Natural: where antibodies are passed from mother to foetus via the placenta or to a baby via breast milk (colostrum)

  Feature	Active	Passive
  Production of antibodies	produced by the body	not produced by the body
  Time before antibodies appear in the blood	1–2 weeks	immediate
  Presence of memory cells	yes	no
  Induced by:
  Natural	exposure to a pathogen	antibodies received from another organism (e.g. via the placenta or colostrum/breast milk)
  Artificial	vaccination	antibodies manufactured and injected or transfused into the organism (e.g. monoclonal antibodies delivered by blood transfusion)