Inflammation Overview

Inflammation Definition

• Local vascular and cellular response of living tissue against an injurious agent
• Aims to fight bacteria, localize infection, and remove damaged tissue

Objectives

• Define inflammation
• Differentiate between acute and chronic inflammation
• Recognize the steps of extravasation of inflammatory cells
• Recognize the process of chemotaxis and phagocytosis
• Identify different examples of inflammation

Causes of Inflammation

• Allergic reactions
• Chemical irritants
• Infections
• Trauma/Injury
• Burns
• Lacerations/Cuts/Wounds
• Frostbite
• Cardiovascular disease
• Neurological disease
• Autoimmune diseases (e.g., Rheumatoid Arthritis)
• Cancer
• Lupus
• Fibromyalgia
• Chronic Fatigue Syndrome
• Acute and chronic inflammation

Types of Inflammation

• Acute
• Chronic

Cells in Acute and Chronic Inflammation

• Acute: Neutrophils (phagocytosis, pus cells)
• Chronic: Lymphocytes, plasma, histiocytes (chronic phagocytosis, monocytes), eosinophils (allergy, parasitic), mast cells (allergy – histamine, serotonin), giant cells (phagocytosis, histiocytes)

Acute vs Chronic Inflammation

Local Signs of Inflammation

• Heat
• Redness
• Swelling
• Pain
• Loss of function

Systemic Effects of Inflammation

• Fever
• Leukocytosis
• Malaise
• Nausea
• Anorexia
• Lymphoid hyperplasia
• CRP (C-reactive protein), ESR (erythrocyte sedimentation rate) raised

Main Events of Inflammation

• Vascular response
• Inflammatory fluid exudate
• Inflammatory cellular exudate

1) Vascular Response

• Changes in vascular flow and caliber (vasodilation, stasis)
• Increased vascular permeability (histamine, kinins)
• Direct endothelial injury (formation of gaps)

2) Inflammatory Fluid Exudate

• Formation: Increased vascular permeability, hydrostatic and interstitial osmotic forces.
• Function: Dilute toxins/chemicals/poisons, deliver antibodies, deliver nutrition, help with the localization and movement of inflammatory cells and fibroblasts

3) Composition of Exudate

• Appearance: Turbid
• Consistency: Viscous
• Protein content: High (4-8g/dL)
• Specific gravity: High (>1018)
• Cell content: Numerous neutrophils
• On standing: Clumping/clotting

3) Cellular Exudate

• Steps of extravasation of neutrophils: margination, rolling/EAPING, adhesion, transmigration/diapedesis
• Chemotaxis: movement of neutrophils and macrophages towards the irritant (exogenous/endogenous mediators).
• Leukocyte "activation": production of eicosanoids, degranulation, and cytokine secretion.
• Phagocytosis: ingestion and destruction of bacteria, necrotic debris, and foreign particles by phagocytic cells

Phagocytosis

• Ingestion and destruction of bacteria, necrotic debris, and foreign particles by phagocytes.
• Phagocytes include neutrophils and macrophages.
• Phases: Recognition/Opsonization, engulfment, degradation(killing).

Outcomes of Acute Inflammation

• Resolution
• Regression and healing
• Progression and spread
• Progression to chronicity

Acute Inflammations Types

• Suppurative (pus formation)
  • Localized: abscess, furuncle, carbuncle
  • Diffuse: cellulitis
• Non-suppurative

Pus Characteristics/Composition

• Non-coagulable, creamy, alkaline, yellowish/yellow-green fluid
• Composed of: fluid exudate (no fibrin), pus cells (PNLs, macrophages, RBCs), liquified necrotic tissue, bacteria, and pigments

Abscess

• Localized suppurative inflammation
• Causes: Staphylococcus
• Site: Skin, organs
• Microscopically: necrotic tissue, dead neutrophils, inflamed tissue, granulation tissue, fibrosis

Cellulitis

• Diffuse suppurative inflammation
• Causes: Streptococcus
• Characterized by fibrinolysin, hyaluronidase and spreading factors
• Site: Loose connective tissue
• Pus: Thin, sanguinous
• More common than abscess

Chronic Inflammation

• Causes: Persistence of infection, prolonged exposure to insult
• Types: Non-specific (following acute), specific (granuloma)

Granulomas

• Chronic, specific inflammation with nodular collection of epithelioid cells, lymphocytes, and giant cells
• Etiology:
  • Infective: Tuberculosis (TB), Leprosy, Syphilis, parasitic (Bilharzia, Leishmania), fungal (Madura foot)
  • Non-infective: Foreign body (FBs), Selecosis, unknown (Crohn's disease, sarcoidosis).

Granuloma Components

• Epithelial cells
• "Giant" cells (Langhans)
• Lymphocytes
• Fibroblasts

Granuloma Classification

• Granuloma with caseation (TB)
• Granuloma without caseation (Sarcoidosis, Crohn's, Bilharzia, Selecosis)
• Suppurative granuloma (e.g., cat scratch disease)
• Foreign body granuloma (e.g., thread, silicon implant)

This quiz covers the definition of inflammation, its types, and the cellular responses involved in both acute and chronic cases. Participants will also learn about the causes and examples of inflammation, enhancing their understanding of this crucial biological response.