Understanding Inflammation and Its Effects

What is Inflammation?

• The body's response to injury
• Designed to eliminate the cause of injury and break down damaged cells
• Part of innate immunity: First line of defense
• Not a disease and not always caused by infection
• Denoted by the suffix "itis"

Beneficial effects

• Delivery of immune cells and proteins
• Dilution of toxins
• Elimination of substances to allow tissue repair
• Stimulating further response
• Entry of drugs

Malfunction of Inflammation

• Inappropriate triggers: Autoimmune disorders
• Excessive response: Sepsis
• Inadequate response: AIDS

Causes of Inflammation

• Infectious agents
• Chemicals
• Foreign bodies
• Physical trauma
• Dead cells
• Allergens

Types of Inflammation

• Acute Inflammation: Immediate defensive response, characterized by vascular and exudative processes
• Chronic Inflammation: Prolonged and persistent inflammation, can be a continuation of acute inflammation or due to an insidious insult, characterized by scar tissue formation

Acute Inflammation

• Macroscopic Features:

  • Erythema (redness)
  • Oedema (swelling)
  • Warmth
  • Pain
  • Loss of function

• Microscopic Features:

  • Vascular changes: Vasodilation
  • Exudative changes: Increased permeability for fluid, proteins, and cells
  • Neutrophil emigration and accumulation to eliminate substances through phagocytosis

Outcomes of Acute Inflammation

• Resolution
• Chronic inflammation
• Healing
• Tissue injury with lytic enzymes and pus accumulation
• Autoimmune disease
• Death

Chronic Inflammation

• Features:

  • Prolonged duration
  • Coexistence of inflammation, injury, and repair
  • Can follow acute inflammation or develop insidiously

• Microscopic Features:

  • Lymphocytes and macrophages
  • Tissue destruction
  • Attempts at healing
  • Adaptive immunity

Adaptive Immunity in Chronic Inflammation

• T Lymphocytes:
  • Helper T cells (TH)
  • Cytotoxic T cells (TC)
• B Lymphocytes
• Plasma cells

Other mediators in Chronic Inflammation

• Monocytes/Macrophages
• Interleukins
• Acute phase proteins
• Complement

Leukocytosis

• Increase in white blood cell count, indicating inflammation

Activity Response

• Patient 1: 45-year-old gentleman with a high white blood cell count indicates possible bacterial infection.
• Patient 2: 89-year-old lady with dementia, the high WBC count combined with high neutrophil count might also indicate bacterial infection, but the dementia might complicate interpretation and diagnosis.

Inflammation

• Inflammation is the body's response to injury
• Its purpose is to get rid of the cause of injury and break down damaged cells
• Inflammation is part of innate immunity, the body's first line of defence
• Inflammation is not a disease
• Inflammation is not always caused by infection
• Inflammation is denoted by the suffix 'itis'
• The suffix 'itis' indicates inflammation of an organ, for example, appendicitis is inflammation of the appendix
• Inflammation can be beneficial
• It delivers immune cells and proteins that help the body fight off infection and repair damaged tissue
• It dilutes toxins
• Inflammation allows tissue repair
• Inflammation can be harmful
• It can be inappropriately triggered, leading to autoimmune disorders
• An excessive response can lead to sepsis
• An inadequate response can lead to AIDS
• Causes of inflammation include: infection, chemicals, foreign bodies, physical trauma, dead cells, and allergens

Types of Inflammation

• Acute inflammation is the immediate response to injury
• Acute inflammation is characterised by vascular and exudative processes
• There is an increase in blood flow to the affected area
• Fluid, proteins and cells move into the affected area
• Neutrophils emigrate and accumulate in the affected area
• Neutrophils try to eliminate the cause of injury by phagocytosis
• Chronic inflammation is a prolonged and persistent response to injury
• Chronic inflammation can be a continuation of acute inflammation
• Chronic inflammation can be caused by an insidious insult, such as a persistent infection or foreign body
• Chronic inflammation is characterised by scar tissue formation

Chronic Inflammation

• Causes of chronic inflammation include: persisting infection, autoimmune diseases, persisting foreign bodies, ongoing injury, ongoing trauma, prolonged toxin exposure, and an inadequate response to the initial injury
• Chronic inflammation is characterised by a prolonged duration
• It is a mixture of inflammation, injury and repair
• It can follow acute inflammation or develop insidiously
• Chronic inflammation involves adaptive immunity
• Adaptive immunity involves lymphocytes, including T helper cells, cytotoxic T cells, B lymphocytes and plasma cells
• Other mediators of chronic inflammation include: monocytes/macrophages, interleukins, acute phase proteins and complement

Outcomes of Acute Inflammation

• The outcomes of acute inflammation are resolution or chronic inflammation
• Resolution is the ideal outcome and occurs when the cause of injury is removed and the tissue heals
• Chronic inflammation occurs when the cause of injury is not removed or when the body is unable to heal properly
• Other outcomes of acute inflammation include: healthy tissue injury, pus accumulation and death

Outcomes of Inflammation

• Possible outcomes of inflammation other than chronic inflammation include:
• Healing
• Death
• Autoimmune disease
• Lytic enzymes
• Accumulation of pus