Causes of inflammation and transition to tissue repair
THE CONTEXT
Inflammation may be triggered by infection, tissue necrosis, foreign bodies, or immune reactions. After elimination of the offending agents, repair replaces injured tissue.
Resolution and repair
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Once inflammation eliminates the offending agents, it subsides and initiates tissue repair.
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Repair replaces injured tissue through regeneration of surviving cells and filling of residual defects with connective tissue, producing scarring.
Infections and tissue necrosis
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Host recognition of microbial products elicits inflammatory reactions during infection.
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Tissue necrosis can result from ischemia, trauma, or physical and chemical injury, including thermal injury, irradiation, and toxins.
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Ischemia means reduced blood flow and causes infarction in the heart, brain, and other tissues.
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Molecules released by necrotic cells can trigger inflammation without infection; this is called sterile inflammation.
Foreign bodies and immune reactions
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Foreign bodies, including sutures and tissue implants, can elicit sterile inflammation.
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Immune reactions, also called hypersensitivity, occur when the normally protective immune system damages the individual’s own tissues.
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Autoimmune diseases and allergies are caused by immune responses, with inflammation contributing substantially to tissue injury in both.