Overview of Immunology

May 25, 2024

Overview of Immunology

Introduction

  • Speaker: Tom from Zero to Finals
  • Focus: Basics of the immune system
    • Revisit details to fit into the bigger picture
  • Categories: Innate immune system and Specific immune system
    • Innate: Immediate, generalized response
    • Specific: Specialized T and B cells, takes longer to respond particularly upon first exposure

The Immune System Breakdown

Initial Barriers

  • Physical Barriers
    • Examples: Skin, mucosa of respiratory, gastrointestinal, and urinary tracts
  • Chemical Barriers
    • Examples: Hydrochloric acid in the stomach, lysozyme in sweat and tears, lactic acid in the vagina

Response to Pathogen Invasion

  1. Macrophages recognize pathogen and activate the innate immune system
  2. Dendritic Cells pick up antigens and activate specific T and B cells
  3. Complement System activated via lectin and alternative pathways

Innate Immune System Response

  • Recognition: Macrophages recognize pathogen-associated molecular patterns (PAMPs)
    • Use receptors like toll-like receptors
  • Phagocytosis
    • Pathogens engulfed into phagosomes, fused with lysosomes for digestion
  • Cytokines: Alarm signaling proteins leading to inflammation
    • Recruits more immune cells (e.g., neutrophils, monocytes)

Inflammatory Response

  • Processes: Vasodilation, increased vascular permeability, mast cell activation
  • Acute Phase Response
    • Interleukins (e.g., IL-1, IL-6, IL-8) recruit and activate immune cells and systemic effects
    • Example: Fever to increase body temperature, conserve energy

Complement System

  • Helps both innate and specific immune system destroy pathogens
  • Proteins: C1 to C9
    • Cascade activation leads to various immune functions: opsonins, further inflammation, direct attack
  • Activation Pathways
    • Lectin and alternative: Directly by pathogens
    • Classical: Antibody-antigen complexes

Specific Immune System

  • Key Players: T and B cells (types of lymphocytes)
    • Located in lymph nodes and mucosa-associated lymphoid tissue
    • Each specific to a single type of antigen
  • Dendritic Cells
    • Present antigens to T and B cells in lymphatic tissue
  • T-Cell Activation
    • CD4 (T helper cells) present antigens and secrete cytokines
    • CD8 (cytotoxic T cells) destroy infected cells

Cytotoxic Mechanisms

  • Granule Exocytosis: Releases enzymes causing cell lysis
  • Fas Molecule: Triggers apoptosis

B-Cell Activation and Antibodies

  • Plasma Cells: Differentiated B cells producing antibodies
  • Antibodies
    • Y-shaped, variable and fixed ends
    • Functions: Neutralize toxins, prevent viral/bacterial actions, agglutination, act as opsonins

Conclusion

  • Summary: Comprehensive overview of how the immune system functions
  • Additional Resources: More videos, website with notes, illustrations, practice questions
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