Key Concepts of the Immune System

Introduction: Sex and Not Dying

• Biology focuses on reproduction (sex) and survival (not dying).
• Human bodies are constantly exposed to pathogens that aim to exploit us.

Immune System Overview

• Our immune system is an elite team of microscopic defenders.
• It defends us against pathogens and helps us survive.
• Pus indicates the presence of an immune response.

Types of Immunity

• Innate Immunity: Non-specific, quick response. Present from birth.
  • Every animal has it (e.g., sponges).
  • First line of defense: skin, mucous membranes.
  • Second line: inflammatory response.
• Acquired (Adaptive) Immunity: Learns to recognize pathogens.
  • Only vertebrates have it.
  • Develops after birth through exposure to pathogens.
  • Involves lymphocytes (T cells and B cells).

Innate Immunity

• Skin and Mucous Membranes:
  • Skin: Oily, acidic, prevents pathogen entry.
  • Digestive tract acts as a barrier.
  • Mucous membranes trap microbes.
• Inflammatory Response:
  • Mast cells release histamine, increasing blood flow and white blood cells to infected areas.
  • White blood cells (leukocytes) have VIP access to body areas.
  • Allergic reactions occur when the immune system overreacts.

Types of White Blood Cells

• Phagocytes: Ingest microorganisms.
  • Neutrophils: Quickly kill microbes.
  • Macrophages: Kill bacteria and rogue cells.
  • Natural Killer Cells: Attack infected or cancerous cells.
  • Dendritic Cells: Communicate pathogen information to acquired immune system.

Acquired Immunity

• Antigens: Substances triggering antibody production.
• Antibodies: Proteins from B cells that recognize and tag pathogens.
• Lymphocytes: Target specific pathogens.
  • T Cells:
    • Helper T Cells: Coordinate immune response.
    • Cytotoxic T Cells: Destroy infected cells.
  • B Cells:
    • Produce antibodies.
    • Differentiate into plasma and memory cells.

Immune Responses

• Cell-Mediated Response: T cells combat infected cells.
  • Helper T cells activate immune response.
  • Cytotoxic T cells kill infected cells.
• Humoral Response: Targets pathogens in body fluids.
  • B cells produce antibodies.

Conclusion

• The immune system involves complex interactions between various cells and proteins to protect against pathogens.
• Understanding these mechanisms helps in appreciating how our bodies prevent diseases and manage infections.