Inflammation: Definition, Causes, and Stages

Definition and Causes

• Inflammation is a natural response of the body's immune system to injury, infection, or damage.
• It is a complex biological process involving various cell types, chemical mediators, and tissues.
• Causes of inflammation include:
  • Infection (bacterial, viral, fungal)
  • Injury (physical, thermal, chemical)
  • Autoimmune disorders (e.g., rheumatoid arthritis, lupus)
  • Allergic reactions
  • Environmental factors (e.g., pollution, UV radiation)

Stages of Inflammation

• Acute inflammation: immediate response to injury or infection, characterized by:
  • Increased blood flow to the affected area
  • Increased permeability of blood vessels
  • Migration of white blood cells (leukocytes) to the site
  • Release of chemical mediators (e.g., histamine, bradykinin)
• Chronic inflammation: prolonged inflammation, often associated with:
  • Tissue damage and repair
  • Fibrosis (scarring)
  • Immune system dysregulation

Signs and Symptoms

• Cardinal signs: classic symptoms of inflammation:
  • Redness (rubor)
  • Swelling (tumor)
  • Heat (calor)
  • Pain (dolor)
  • Loss of function (functio laesa)
• Other symptoms may include:
  • Fever
  • Fatigue
  • Muscle weakness
  • Joint stiffness

Chemical Mediators

• Cytokines: signaling molecules that regulate inflammation:
  • Pro-inflammatory cytokines (e.g., TNF-α, IL-1β)
  • Anti-inflammatory cytokines (e.g., IL-10, TGF-β)
• Chemokines: chemotactic cytokines that attract immune cells:
  • CXCL8 (IL-8)
  • CCL2 (MCP-1)
• Eicosanoids: lipid-derived mediators:
  • Prostaglandins (e.g., PGE2)
  • Leukotrienes (e.g., LTB4)

Resolution of Inflammation

• Resolution phase: the process of returning to homeostasis:
  • Clearance of inflammatory mediators
  • Resolution of tissue damage
  • Restoration of tissue function
• Regulatory mechanisms: mechanisms that regulate inflammation:
  • Immune suppression (e.g., Tregs, cytokine regulation)
  • Anti-inflammatory cytokines (e.g., IL-10, TGF-β)
  • Resolution of inflammation through specialized pro-resolving mediators (SPMs)

Inflammation Definition and Causes

• Inflammation is a natural immune response to injury, infection, or damage.
• It's a complex biological process involving various cell types, chemical mediators, and tissues.
• Causes of inflammation include:
  • Infection (bacterial, viral, fungal)
  • Injury (physical, thermal, chemical)
  • Autoimmune disorders (e.g., rheumatoid arthritis, lupus)
  • Allergic reactions
  • Environmental factors (e.g., pollution, UV radiation)

Stages of Inflammation

• Acute Inflammation:
  • Immediate response to injury or infection
  • Characterized by increased blood flow, permeability, and white blood cell migration
  • Release of chemical mediators (e.g., histamine, bradykinin)
• Chronic Inflammation:
  • Prolonged inflammation often associated with tissue damage and repair
  • Fibrosis (scarring) and immune system dysregulation

Signs and Symptoms

• Cardinal Signs:
  • Redness (rubor)
  • Swelling (tumor)
  • Heat (calor)
  • Pain (dolor)
  • Loss of function (functio laesa)
• Other symptoms may include:
  • Fever
  • Fatigue
  • Muscle weakness
  • Joint stiffness

Chemical Mediators

• Cytokines:
  • Pro-inflammatory cytokines (e.g., TNF-α, IL-1β)
  • Anti-inflammatory cytokines (e.g., IL-10, TGF-β)
• Chemokines:
  • Attract immune cells (e.g., CXCL8, CCL2)
• Eicosanoids:
  • Prostaglandins (e.g., PGE2)
  • Leukotrienes (e.g., LTB4)

Resolution of Inflammation

• Resolution Phase:
  • Clearance of inflammatory mediators
  • Resolution of tissue damage
  • Restoration of tissue function
• Regulatory Mechanisms:
  • Immune suppression (e.g., Tregs, cytokine regulation)
  • Anti-inflammatory cytokines (e.g., IL-10, TGF-β)
  • Resolution through specialized pro-resolving mediators (SPMs)