week 12- #1

IMMUNE SYSTEM OVERVIEW

  • The immune system is responsible for defending the body against pathogens (disease-causing agents).
    • Pathogenic agents include:
    • Viruses
    • Bacteria
    • Fungi
    • Parasites
    • Protists
    • Prions

IMMUNE SYSTEM CLASS OUTLINE

  • Key topics covered in Week 12:
    • Innate Immunity
    • Inflammation
    • The lymphatic system
    • Adaptive Immunity
    • B Cells, antibodies, and humoral immunity
    • T Cells and cell-mediated immunity
    • Immune Disorders

INNATE IMMUNITY

  • Definition: Non-specific immune responses that act as the first line of defense.
  • Components include:
    • External Barriers:
    • Impermeable Skin: Acts as a physical barrier to pathogens.
    • Desquamation: Shedding of dead skin cells helps slough off pathogens.
    • Stomach Acids: Low pH kills harmful bacteria.
    • Tears & Saliva: Contain antibacterial enzymes.
    • Mucus Linings: Trap dirt and microbial pathogens.
    • Hairs: Filter out pathogens from inhaled air.
    • Internal Defenses: (Humoral and Cellular)
    • Humoral Immunity: Involves secreted molecules for pathogen destruction.
    • Cellular Immunity: Involves cells directly killing pathogens.

WHITE BLOOD CELLS (LEUKOCYTES)

  • Derived from stem cells and play a crucial role in the immune response.
    • Types of White Blood Cells:
    • Granulocytes: Include neutrophils, basophils, and eosinophils.
    • Agranulocytes: Include lymphocytes (B Cells and T Cells) and monocytes.
    • Common functions:
    • Basophils: Release histamine (inflammation) and target allergens.
    • Eosinophils: Release toxic chemicals and target parasites.
    • Neutrophils: Move to the site of infection, phagocytose microorganisms.
    • Macrophages: Phagocytose pathogens and dead cells, live in tissues.
    • Natural Killer Cells: Target stressed or infected cells for destruction.

HUMORAL IMMUNITY

  • Complement System:
    • Functions include:
    1. Opsonization: Marks cells for phagocytosis, facilitating immune cell binding.
    2. Chemotaxis: Attracts immune cells to the site of infection.
    3. Lysis: Destroys pathogen cells by piercing the cell membrane.
    4. Inflammation: Helps mobilize the immune response by inducing vascular changes.

INFLAMMATION

  • Purpose: Mobilizes innate immunity to site of infection.
    • Key factors include:
    • Complement proteins
    • Histamines (causes vasodilation)
    • Recruitment of phagocytes (neutrophils and macrophages)
    • Benefits:
    • Quickly responds to infection.
    • Can lead to discomfort (itching) necessitating the use of antihistamines and anti-inflammatory medications.

LYMPHATIC SYSTEM

  • Functions:
    • Collects interstitial fluid (excess fluid from tissue)
    • Plays a significant role in immune response by containing lymphocytes and macrophages.
    • Major organs include:
    • Lymph nodes
    • Thymus
    • Spleen
    • Bone marrow
  • Importance of Lymph Nodes:
    • Swollen lymph nodes can indicate infection or other issues, assessed during medical examinations.

QUESTIONS AND DISCUSSIONS

  • Think-Pair-Share Exercises:
    • Discuss advantages of innate immune responses vs. use of anti-inflammatory drugs.
    • Cases when immune systems might not want to lyse infected cells (e.g., in viral infections) when other responses might be beneficial.