Lecture: Inflammation and Repair

Definition of Inflammation

• Response of vascularized tissue to any cellular injury or infection.
• Mechanism to bring host defense cells/molecules to the needed sites.

Types of Inflammation

1. Acute Inflammation
   • Fast onset (minutes to hours).
   • Typically involves neutrophils.
   • Local/systemic signs and symptoms are prominent (e.g., redness, swelling, pain, heat, loss of function).
   • Generally mild and self-limited.
2. Chronic Inflammation
   • Slow onset (days to months).
   • Involves monocytes, macrophages, and lymphocytes.
   • Tissue injury often severe and progressive.

Features of Inflammation

• Five Cardinal Signs: Redness, swelling, heat, pain, loss of function.
• Physiological Basis: Increased blood flow, exudation, release of mediators.

Causes of Inflammation

• Infections (bacterial, viral, fungal, parasitic).
• Foreign bodies.
• Tissue necrosis (due to ischemia, trauma).
• Immune reactions (autoimmune diseases, allergies).

Steps of Inflammation

1. Recognition of Injury
2. Recruitment of Leukocytes
3. Removal of Agent
4. Regulation of Response
5. Repair

Leukocyte Recruitment and Activity

• Neutrophils: Predominant in acute inflammation.
• Monocytes/Macrophages: Predominant in chronic inflammation.
• Phagocytosis: Recognition, engulfment, and degradation of offending agents.

Vascular Changes in Inflammation

• Vasodilatation: Earliest manifestation, increases blood flow.
• Vascular Permeability: Hallmark of acute inflammation, allows leukocytes to exit the bloodstream.
• Edema Formation: Accumulation of fluid, can be exudates (protein-rich) or transudates (protein-poor).

Inflammatory Mediators

• Histamine and Serotonin: Cause vasodilatation and increased permeability.
• Prostaglandins and Leukotrienes: Involved in pain, fever, and bronchospasm.
• Cytokines: Interleukins and tumor necrosis factors, manage immune responses.
• Complement System: Enhances inflammation and pathogen clearance.

Chronic Inflammation

• Persistent inflammation due to non-healing wounds, prolonged exposure, or autoimmune conditions.
• Characterized by tissue destruction and fibrosis.
• Key cells: Macrophages, lymphocytes, mast cells.

Tissue Repair

• Proliferation: Driven by growth factors and stem cells.
• Fibrosis: Replacement with connective tissue in severe cases.
• Angiogenesis: Formation of new blood vessels to support tissue repair.

Wound Healing

• First Intention: Clean, surgical wounds with approximated edges.
• Second Intention: Large, open wounds or abscesses with extensive tissue loss.
• Complications: Can include ulceration, excessive scarring (keloid), or contraction.

Effects of Inflammation

• Systemic Effects: Fever, leukocytosis, increased acute-phase proteins.
• Local Effects: Pain, swelling, redness.

Summary

• Inflammation is a complex process essential for healing but can lead to chronic conditions if unresolved.
• Understanding the mechanisms and regulation of inflammation helps in managing diseases and tissue repair effectively.