Active & Passive Immunity (AQA A Level 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:

  • Natural – from infection

  • Artificial – from vaccination

• Provides long-term immunity due to memory cell formation

• Leads to a faster and stronger secondary response if the same antigen is encountered again

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 – protection is short-term

• This can be used when there is no time to wait for an immune response and immediate protection is needed (e.g. tetanus antitoxin)

• Passive immunity can be:

  • Artificial – injection of antibodies (e.g. antitoxins)

  • Natural – antibodies from mother via placenta or breast milk (colostrum)

  Feature	Active	Passive
  Production of antibodies	They are 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)