Overview of Immunology

Introduction

• Presenter: Tom from Zero2Finals.com
• Objective: Provide a broad understanding of immunology and the immune system
• Categories of Immune System: Innate & Specific
  • Innate Immune System: Immediate, generalized response
  • Specific Immune System: Involves T and B cells, slower, specific response

Components of the Immune System

• Innate Immune System: Already at the infection site
• Specific Immune System: Specialized cells (T and B cells) activated away from infection site
• Complement System: Works alongside innate and specific immune systems

Barriers to Infection

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

Initial Immune Response

• Recognition and Activation:
  1. Macrophages recognize pathogens
  2. Dendritic Cells present antigens to T and B cells
  3. Pathogens activate the complement system via lectin and alternative pathways
• Phagocytosis: Process used by macrophages
  • PAMPs & Receptors: Recognized by Toll-like receptors
  • Process: Pathogen is engulfed, contained in phagosome, then destroyed by lysosomal enzymes

Inflammation and Cytokines

• If pathogens overwhelm macrophages, they release cytokines
• Cytokines: Signal infection and recruit more immune cells
• Inflammation:
  • Vasodilation, increased vascular permeability, mast cell activation, clotting, kinin system activation
  • Interleukins: IL-1 (causes fever), IL-6 (produces acute phase proteins), IL-8 (recruits neutrophils)
  • NK Cells: Activated by IL-2 and IL-12
  • TNF-α: Promotes inflammation

Complement System

• Complement Cascades: Involves complement proteins C1 to C9
• Functions: Opsonins, inflammation, direct pathogen destruction
• Activation Pathways: Lectin, alternate (pathogen directly), classical (antibody-antigen complexes)

Specific Immune System

• Key Players: T and B cells (lymphocytes)
• Antigens: Unique molecules on pathogens
• T Cell and B Cell Activation: Role of Dendritic Cells
• T Cells:
  • CD4 Cells: Proliferate to T-helper cells
  • CD8 Cells: Differentiate into cytotoxic T cells
  • T-helper Cells: Assist in activating B cells and promoting macrophage activity
• B Cells:
  • Plasma Cells: Produce antibodies
  • Memory B Cells: Provide long-term immunity
• Cytotoxic T Cells: Kill infected cells (granule exocytosis, apoptosis via FASP molecule)
• Antibodies: Neutralize toxins, prevent pathogen function, agglutination, act as opsonins

Conclusion

• Summary of innate, specific immune systems, and complement system
• Encouragement to check out related videos and resources on Zero to Finals website for further study