Lecture Notes: Adaptive Immune System and Humoral Immunity

Key Concepts

• Adaptive Immune System: Activated when innate defenses are insufficient. Requires exposure to specific pathogens.

  • Not innate, develops over time as it encounters pathogens.
  • Systemic response: Can operate throughout the body, not limited to specific infections.
  • Memory: Remembers specific pathogens for faster response in future encounters.

• Innate vs. Adaptive Immunity:

  • Innate: Immediate response, non-specific, does not "remember" pathogens.
  • Adaptive: Specific, systemic, remembers pathogens, slower to respond initially.

Components of the Adaptive Immune System

• Humoral Immunity: Involves B cells and antibodies.

  • B Lymphocytes (B cells):

    • Originate and mature in bone marrow.
    • Develop immunocompetence (recognize antigens) and self-tolerance (avoid attacking own cells).
    • Display membrane-bound antibodies specific to antigens.
    • Seed secondary lymphoid organs (e.g., lymph nodes).

  • Antibodies: Proteins that identify and neutralize pathogens.

    • Produced by B cells.
    • Bind to specific antigens to mark them for destruction by other immune cells.
    • Can cause neutralization, agglutination, and attract phagocytes.

Immunity Mechanisms

• Active Humoral Immunity:

  • Occurs when B cells encounter antigens and produce antibodies.
  • Can be natural (e.g., infection) or through vaccination.
  • Vaccinations introduce weakened pathogens to stimulate memory cell production.

• Passive Humoral Immunity:

  • Obtained by receiving antibodies from another source (e.g., maternal antibodies, serum).
  • Temporary as the body does not produce memory cells.

Vaccinations

• Stimulate adaptive immunity by introducing antigens without causing disease.
• Create a memory of the pathogen, leading to faster and stronger responses upon future exposure.
• Important for both non-fatal and serious diseases.

Current Applications

• Flu Vaccines: Need frequent updates due to evolving antigens.
• Ebola Treatment: Serum from immune donors as a temporary measure for passive immunity.

Conclusion

• Adaptive immunity is crucial for long-term pathogen defense.
• B cells and antibodies play a key role in humoral immune response.
• Vaccinations are a vital tool for inducing immunity and preventing disease.