8.3 Acute and chronic inflammation

Acute inflammation is your body's rapid response to injury or infection. It's like a quick-fire defense system, causing redness, heat, swelling, and pain. Chemical messengers like histamine and prostaglandins kickstart the process, while cytokines and complement proteins rally the troops.

Chronic inflammation, on the other hand, is a long-term battle. It can last for weeks, months, or even years. Unlike acute inflammation's quick resolution, chronic inflammation persists, potentially causing ongoing damage. It's often triggered by persistent infections, toxic exposures, or autoimmune disorders.

Acute Inflammation

Characteristics of acute inflammation

Top images from around the web for Characteristics of acute inflammation

• 

  Frontiers | The Extracellular Matrix in Skin Inflammation and Infection View original

  Is this image relevant?

• 

  Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original

  Is this image relevant?

• 

  Frontiers | Platelets in Inflammation: Regulation of Leukocyte Activities and Vascular Repair ... View original

  Is this image relevant?

• 

  Frontiers | The Extracellular Matrix in Skin Inflammation and Infection View original

  Is this image relevant?

• 

  Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Characteristics of acute inflammation

• 

  Frontiers | The Extracellular Matrix in Skin Inflammation and Infection View original

  Is this image relevant?

• 

  Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original

  Is this image relevant?

• 

  Frontiers | Platelets in Inflammation: Regulation of Leukocyte Activities and Vascular Repair ... View original

  Is this image relevant?

• 

  Frontiers | The Extracellular Matrix in Skin Inflammation and Infection View original

  Is this image relevant?

• 

  Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original

  Is this image relevant?

1 of 3

• Acute inflammation manifests as rapid, short-term response to injury or infection typically lasting hours to days
• Cardinal signs encompass redness, heat, swelling, pain, and loss of function indicating inflammatory process
• Vascular changes involve vasodilation increasing blood flow to affected area and heightened vascular permeability allowing plasma proteins and leukocytes to enter tissues
• Leukocyte infiltration occurs through margination (white blood cells adhering to vessel walls), diapedesis (leukocytes migrating through vessel walls into tissues), and chemotaxis (directed movement of leukocytes towards injury site)

Chemical mediators in inflammation

• Histamine released by mast cells and basophils triggers vasodilation and increased vascular permeability
• Prostaglandins derived from arachidonic acid promote vasodilation and pain sensitization (aspirin blocks)
• Cytokines like Interleukin-1 (IL-1) and Tumor Necrosis Factor-alpha (TNF-α) activate endothelial cells and promote leukocyte adhesion while Interleukin-6 (IL-6) stimulates acute phase protein production
• Complement proteins enhance phagocytosis and attract leukocytes, bradykinin increases vascular permeability and causes pain, and nitric oxide acts as vasodilator and antimicrobial agent

Chronic Inflammation

Acute vs chronic inflammation

• Duration differs with acute lasting hours to days while chronic persists for weeks to months or years
• Cellular involvement shifts from predominantly neutrophils in acute to macrophages, lymphocytes, and plasma cells in chronic
• Tissue damage in acute is minimal and often reversible whereas chronic leads to progressive damage potentially causing fibrosis and organ dysfunction
• Resolution patterns vary with acute typically resolving completely while chronic remains an ongoing process with periods of exacerbation and remission

Causes of chronic inflammation

• Persistent infections (tuberculosis, hepatitis C) maintain prolonged immune activation
• Prolonged exposure to toxic agents (silica dust, asbestos) leads to ongoing tissue damage
• Autoimmune disorders (rheumatoid arthritis, systemic lupus erythematosus) result from immune system mistakenly targeting self-antigens
• Mechanisms involve persistent antigen presence stimulating ongoing immune response, dysregulation of immune system failing to resolve acute inflammation, and granuloma formation organizing macrophages in response to persistent antigens
• Consequences include tissue remodeling and fibrosis, angiogenesis forming new blood vessels, and potential for malignant transformation in some cases