Lecture Notes: The Innate Immune System

Introduction

• Immune System Overview: Focus on innate division
• Adaptive vs. Innate:
  • Adaptive Arm: Specific responses to pathogens (bacteria, viruses, fungi)
  • Innate Arm: Non-specific, responds same way to any pathogen
• Analogy:
  • Innate: House's outer defenses (walls, doors)
  • Adaptive: Guards specific to attackers

Characteristics of Innate Immune System

• Non-Specific: Responds identically to all pathogens
• No Memory: Doesn't remember past pathogens
• First Line of Defense

Components of the Innate System

• External Division:

  • Skin: Epidermis made of stratified squamous epithelia
  • Oil Glands (Sebaceous): Unsaturated fatty acids, pH 3-5
  • Sweat: Salty, washes away microbes
  • Hair and Mucus: Traps particles
  • Secretions: Tears and saliva contain lysozymes
  • Cilia: Moves trapped particles to stomach

• Internal Division:

  • Cellular Defenses:
    • Phagocytes: Neutrophils (attack bacteria), Macrophages (antigen-presenting)
    • Wandering Macrophages: Monocytes
    • Fixed Macrophages: Located in specific tissues (e.g., Kupffer cells in liver)
    • NK Cells: Release perforins and granzymes
  • Chemical Defenses:
    • Complement Proteins: Cascade effect, enhance immune responses
    • Cytokines: Interleukins, Interferons, call upon immune cells
  • Physiological Responses:
    • Inflammation: Increases blood flow and permeability
    • Fever: Pyrogens raise body temperature, enhance immune cell function

Detailed Components

• Skin:

  • Epidermis: Stratified squamous epithelia
  • Oil and Sweat: Antimicrobial environment

• Bloodstream Innate Response:

  • Phagocytic Cells:
    • Neutrophils: Most abundant, attack bacteria
    • Macrophages: APCs, destroy pathogens
  • Natural Killer (NK) Cells: Induce apoptosis in pathogens

Chemical Defenses

• Complement System: 30 proteins, cascade activation
• Cytokines: Glycoproteins aiding both innate and adaptive systems

Physiological Responses

• Inflammation:

  • Chemicals: Prostaglandins, Histamines, Bradykinins
  • Cardinal Signs: Redness, heat, pain, swelling
  • Drug Targets: NSAIDs, antihistamines

• Fever:

  • Pyrogens: Raise body's thermostat, enhance immune response
  • Benefits: Improved immune cell function, reduced pathogen reproduction

Summary

• Innate Immune System: Essential, provides immediate defense
• Balance: Importance of regulated inflammation and fever

These notes provide a comprehensive overview of the innate immune system focusing on its non-specific nature, key components, and physiological responses such as inflammation and fever. They also offer insights into how different cellular and chemical defenses operate to protect the body from pathogens.

For further details and visuals, review the lecture video by Dr. Mike. For questions or further engagement, contact Dr. Mike on social media platforms.