2.6.2 Active & Passive Immunity

Types of Immunity:

1. Active Immunity:

• Definition:
  • Immunity gained when the body produces its own antibodies in response to an antigen.
• Key Features:
  • Long-term immunity due to the formation of memory cells.
  • Takes time to develop as it requires an immune response.
• Examples:
  • Natural Active Immunity:
  • Occurs after being exposed to a pathogen or recovering from a disease.
  • Example: Developing immunity to chickenpox after infection.
  • Artificial Active Immunity:
  • Achieved through vaccination, where antigens are introduced into the body to stimulate an immune response.
  • Example: Measles vaccination.

2. Passive Immunity:

• Definition:
  • Immunity gained by the transfer of antibodies from another source, without the involvement of the recipient's immune system.
• Key Features:
  • Provides immediate protection.
  • Short-term immunity as no memory cells are formed.
• Examples:
  • Natural Passive Immunity:
  • Occurs when a mother's antibodies are passed to her baby via the placenta or breast milk.
  • Example: Protection against infections in newborns.
  • Artificial Passive Immunity:
  • Achieved by injecting antibodies into an individual.
  • Example: Anti-venom for snake bites or monoclonal antibodies.

Comparison of Active and Passive Immunity:

Feature	Active Immunity	Passive Immunity
Source of antibodies	Produced by the individual's immune system.	Introduced from an external source.
Memory cells	Yes, memory cells are formed.	No, memory cells are not formed.
Duration	Long-term immunity.	Short-term immunity.
Onset	Slower, as it requires the immune response.	Immediate protection.
Examples	Vaccination, recovering from an illness.	Maternal antibodies, anti-venom injections.

Importance of Immunity:

1. Active Immunity:

• Provides long-term protection and contributes to herd immunity.
• Basis for the success of vaccination programmes.

2. Passive Immunity:

• Critical for immediate protection in emergencies, such as snake bites or viral outbreaks.