Passive Immunity Lecture Notes

Overview of Immunity

• Active Immunity: Requires the body to do the work to fight off infection.
• Passive Immunity: Antibodies are present without the body's active response to a pathogen.

Passive Immunity Characteristics

• Pathogen enters the body but B lymphocytes are inactive.
• Antibodies are already present to combat the pathogen.
• Immediate eradication of pathogens without the person falling sick.
• B lymphocytes do not undergo clonal selection or expansion.
• No memory cells produced.

Types of Passive Immunity

Natural Passive Immunity

• Source: Mother to child via breastfeeding or placenta.
• Mechanism:
  • Antibodies provided through breast milk or placenta.
  • Child's B cells remain inactive.
• Duration: Short-lived protection.
• Limitation: No memory cells; child may fall sick if infected later without continued antibody supply.

Artificial Passive Immunity

• Source: Antibodies from another individual.
• Mechanism:
  • Used when the person's immune system cannot respond quickly.
  • Antibodies injected to provide immediate protection.
• Duration: Short-lived protection.
• Limitation: No memory cells; person may fall sick again if re-infected.

Comparison of Immunity Types

Active Immunity

• Person's body produces antibodies and memory cells.
• Long-term protection due to memory cells.
• Example: Vaccination (Artificial Active Immunity).

Passive Immunity

• Immediate protection.
• Short-term protection as no memory cells are formed.
• Example: Natural (Mother to child), Artificial (Antibody injections).

Important Considerations

• Passive immunity is beneficial for immediate response but lacks long-term protection.
• Vaccines are not administered to already sick individuals as it can introduce more foreign substances and worsen the condition.
• Vaccines are given to healthy individuals for long-term protection against specific pathogens.

Final Thoughts

• Choice between active and passive immunity depends on the situation and urgency of response needed.
• Passive immunity is a quick fix, but for sustainable protection, active immunity is essential.