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

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