Immune Cells Overview

Introduction

• Immune cells originate from hematopoietic stem cells in bone marrow.
• Hematopoietic stem cells differentiate into:
  • Myeloid lineage
  • Lymphoid lineage

Myeloid-Derived Innate Immune Cells

• Macrophages
  • Perform phagocytosis to kill pathogens and clear cellular debris.
  • Tissue-resident macrophages originate in the fetal yolk sac.
  • Secrete cytokines to shape immune response.
• Granulocytes
  • Preloaded with granules of antimicrobial chemicals.
  • Types: Neutrophils, Eosinophils, Basophils, Mast cells.
  • Neutrophils:
    • Most numerous in blood, first responders to infection, effective in phagocytosis.
    • Short lifespan, produce pus.
  • Eosinophils and Basophils:
    • Less common, important for wound healing and tissue repair.
  • Mast Cells:
    • Found in connective tissue, promote allergies and asthma.
• Dendritic Cells
  • Phagocytose and present antigens to T cells in lymph nodes.
  • Vital for linking innate and adaptive immune systems.

Lymphoid-Derived Innate Immune Cells

• Innate Lymphoid Cells
  • Includes Natural Killer Cells which target cancer and virally infected cells.
  • Respond to microbial cues and stress signals.

Adaptive Immune Cells

• Lymphocytes
  • B Cells
    • Produce antibodies that bind to pathogens and mark them for destruction.
    • Require T cell assistance for full activation.
  • T Cells
    • Killer T Cells (CD8): Target and kill cancerous or infected cells.
    • Helper T Cells (CD4): Activate B cells and secrete cytokines.
    • Regulatory T Cells (CD4): Regulate immune response, can kill out-of-control killer T cells.

Immune System Summary

• Composed of myeloid-derived and lymphoid-derived white blood cells.
• Cells communicate via cytokines and chemokines.
• Function to destroy pathogens and heal damaged tissues.

Next Steps

• Upcoming topics include the investigation of the lymphatic system.