Chronic Inflammation:

• Inflammation of prolonged duration (weeks, months or even years) in which active inflammation, tissue destruction and healing proceed simultaneously.
• Characterized by infiltration with mononuclear cells, tissue destruction and repair with new vessel proliferation and fibrosis.
• It may occur as follows:
  • Following acute inflammation:
    • When body is unable to remove or destroy irritant, it continues to persist in that area causing constant irritation with interference in normal process of healing.
  • Response may be chronic from outset:
    • If irritant are of low intensity, they fail to stimulate body defences to cause its destruction and removal and chronic inflammation occurs.
    • Ex: if there is persistent infections by certain microorganisms such as Johne’s disease, tuberculosis, actinomycosis, Actinobacillosis. These organism are of low toxicity.
  • Prolonged exposure to toxic agents:
    • Asbestos and silica particles inhalation for prolonged period sets up chronic inflammatory response in lungs.