Passive and Active Immunity

Introduction

• Passive Immunity: Provides short-term protection by receiving antibodies from another source.
• Active Immunity: Provides long-lasting protection by producing antibodies and forming memory cells.

Passive Immunity

Characteristics:

• Short-term protection.
• Antibodies received from another source (e.g., mother to baby).

Examples:

1. Placenta Transfer:

   • IgG antibodies cross the placenta during the third trimester.
   • Protects the baby both in utero and post-birth.
   • Variability in lifespan of antibodies (e.g., measles antibodies last longer).

2. Breast Milk:

   • Contains various antibodies (e.g., IgA, IgG, IgM, etc.).
   • Includes white blood cells that bind to pathogens, promoting healthy flora.
   • May stimulate or "train" baby's lymphocytes.
   • Common in colostrum, but present throughout breastfeeding.

3. Immunoglobulin Injection:

   • Used for immediate protection (e.g., post-rabies exposure).
   • Provides short-term immunity.

Active Immunity

Characteristics:

• Long-lasting protection.
• Host's body produces antibodies and forms memory cells.

Examples:

1. Natural Exposure:

   • Developing immunity through everyday exposure to pathogens.
   • Natural exposure aligns with the body’s best response pathways (e.g., mucous membranes).

2. Vaccination:

   • Live Attenuated Virus Vaccines:
     • Weakened virus introduced (e.g., MMR: measles, mumps, rubella).
   • Deactivated Toxin Vaccines:
     • Expose to toxins, not the pathogen itself (e.g., diphtheria and tetanus).
   • Cell Part Vaccines:
     • Use parts of bacterial cells (e.g., pertussis).

Adjuvants

• Substances added to vaccines to provoke a stronger immune response.
• Can be controversial due to potential side effects (e.g., heavy metals like aluminum).

Conclusion

• Understanding the differences and roles of passive and active immunity aids in appreciating how our body defends itself and the utility of vaccinations.