Inflammation : Cellular response

Cellular response

• Blood flow through capillaries in area of inflammation slows as fluid is lost and viscosity increases
• Neutrophils and monocytes move to inner surface of capillaries and then migrate through capillary wall to site of injury
  • Chemotaxis
    • Directional migration of WBCs along concentration gradient of chemotactic factors
    • Mechanism for accumulating neutrophils and monocytes at site of injury
  • Neutrophils
    • First leukocytes to arrive at site of injury (6 – 12 hours)
    • Phagocytize bacteria, other foreign material, and damaged cells
    • Short life span (24 – 48 hours)
    • Pus is composed of
      • Dead neutrophils accumulated at site of injury
      • Digested bacteria
      • Other cell debris
    • Bone marrow releases more neutrophils in response to infection, resulting in elevated WBC
  • Monocytes
    • Second type of phagocytic cells to migrate to site of injury from circulating blood
    • Attracted to the site by chemotactic factors
    • Arrive within 3 to 7 days after onset of inflammation
    • On entering tissue spaces, monocytes transform into macrophages
    • Assist in phagocytosis of inflammatory debris
    • Macrophages have a long life span and can multiply
  • Macrophages
    • Important in cleaning area before healing can occur
    • May stay in damaged tissues for weeks
    • Cells may fuse to form multinucleated giant cell
  • Lymphocytes
    • Arrive later at the site of injury
    • Primary roles of lymphocytes involve
      • Cell-mediated immunity
      • Humoral immunity