The Adaptive Immune System and Humoral Response

Introduction

• Analogy: Like in World of Warcraft, to defeat an enemy, you must understand it.
• Comparison: Innate defense system vs. Adaptive immune system
  • Innate: Immediate response, generalized defense
  • Adaptive: Requires introduction to pathogen, specific and stronger response

Adaptive Immune System

• Activation: Triggered when a threat overpowers the innate system
• Characteristics: Popularity for:
  • Not innate (ex. requires exposure to become active)
  • Slow initial response, but retains memory of pathogens
  • Systemic response: Can fight infections throughout the body
  • Uses humoral immunity and cellular defenses

Humoral Immunity

• Components: Antibodies produced by B lymphocytes
• Role: Patrol body fluids like blood and lymph to combat pathogens
• Key functions:
  • Identifying and binding to specific antigens
  • Targeting viruses, bacteria
  • Important for long-term immunity (e.g., recovering from mumps)
  • Basis for vaccinations

Antigens

• Definition: Foreign molecules that trigger adaptive immune response
• Types: Bacteria, viruses, toxins, diseased cells
• Role: Flagging pathogens for adaptive immune system

B Lymphocytes (B Cells)

• Origin: Bone marrow
• Function: Recognize specific antigens and develop antibodies
• Mechanisms:
  • Immunocompetence: Ability to bind specific antigens
  • Self-tolerance: Avoid attacking the body's own cells
• Activation: Binding to the perfect antigen leads to:
  • Cloning to produce effector B cells (plasma cells) and memory B cells
  • Mass production of antibodies (approx. 2,000 per second for 4-5 days)

Antibodies

• Structure & Function:
  • Membrane-bound on B cell surface initially; later free-floating in blood/lymph
  • Neutralization: Block pathogen binding sites
  • Agglutination: Clumping antigens for easier removal by phagocytes
  • Rousing other immune cells for cleanup

Immunity Types

• Active humoral immunity:
  • Natural occurrence (e.g., getting infected)
  • Artificial induction (vaccinations)
• Passive humoral immunity:
  • Natural (e.g., maternal antibodies during pregnancy/breastfeeding)
  • Artificial (e.g., receiving antibodies from recovered patients)

Vaccinations

• Mechanism: Introduce a dead/weakened pathogen to prime the immune response
• Purpose: Speed up and intensify the secondary immune response to genuine infections
• Effectiveness: Essential in preventing serious diseases (e.g., polio, measles)
• Challenges: Some pathogens, like influenza, evolve quickly

Conclusion

• Summary: Adaptive immune system's humoral response guards extracellular regions
• Process: B cells mature, identify antigens, make antibodies, and trigger immune responses
• Further Topics: Cellular defenses and their role in combating intracellular pathogens