Mediators of Inflammation Quiz

Mediators of Inflammation

• Mediators of inflammation are chemical substances that regulate inflammation.
• Two types exist: plasma-derived and cell-derived mediators.
• Plasma-derived mediators are proteins circulating in the blood, becoming active in response to inflammatory triggers. They are mainly produced in the liver.
• Cell-derived mediators are produced locally by cells.
• Most mediators are short-lived, breaking down quickly or being inactivated by enzymes.
• One mediator often triggers the release of another.
• Some mediators can harm cells and tissues.

Chemical Mediators

• Plasma-Derived:
  • Complement proteins (activated for inflammation)
  • Clotting factors
  • Kinin system
• Cell-Derived (Preformed):
  • Histamine (Mast cells)
  • Serotonin (Platelets and nerve endings)
• Cell-Derived (Synthesized de novo):
  • Arachidonic acid metabolites (e.g., prostaglandins, leukotrienes)
  • Cytokines (e.g., TNF, IL-1, IL-6)
  • Chemokines
  • Complement proteins (some)
  • Kinins

Actions of Mediators

• Histamine:
  • Source: Mast cells
  • Action: Vasodilation, increased vascular permeability.
• Platelet-activating factor: Affects blood vessels and platelets during inflammation.
• Cytokines:
  • Sources: Macrophages, mast cells, T lymphocytes, endothelial cells.
  • Actions: Involved in acute and chronic inflammation, fever, promoting leukocyte recruitment, and activating macrophages.
• Chemokines: Attract leukocytes to sites of inflammation.
• Complement:
  • Actions:
    • Opsonization (enhancing phagocytosis).
    • Chemotaxis (attracting leukocytes).
    • Cell lysis (membrane attack complex).

Arachidonic Acid Metabolites

• Derived from cell membrane phospholipids via the action of enzymes (e.g., phospholipases).
• Prostaglandins:
  • Actions: Vasodilation, increased vascular permeability, pain, fever.
• Leukotrienes:
  • Actions: Increased vascular permeability, bronchospasm, chemotaxis.
• Lipoxin:
  • Actions: Inhibit inflammation.

Types of Inflammation

• Acute Inflammation:
  • Characterized by vascular congestion, edema, and neutrophil infiltration.
  • Mediators include histamine, prostaglandins, leukotrienes, and cytokines.
• Chronic Inflammation:
  • Longer duration, involves mononuclear cells (lymphocytes and macrophages).
  • Mediators include cytokines and growth factors. Outcomes can be fibrosis.

Other types of inflammation

• Fibrous: Occurs when significant fluid leaks, clotting factors enter the tissues. Fibrin forms, and the tissues are scar-like.
• Serous: Characterized fluid accumulation and little cell debris, often in the body cavities.
• Purulent (suppurative): Pus formation, often caused by bacterial infection.
• Granulomatous: Collection of macrophages and lymphocytes, often a chronic response to something the body can't get rid of.
• Ulcers: Tissue loss, often in the lining of organs.