7.1.3 Type III
  • Type III Hypersensitivity (Immune Complex Mediated)
    • Antigen (Ag) + antibody (Ab) complexes produce tissue damage by activation of serum mediators (primarily complement)
  • Antibodies are produced by a large dose od administered antigen (~5 days after administration)
  • Ag-Ab complexes are deposited in the tissues, (often inducing localized type I hypersensitivity reactions in glomeruli, joints, skin, heart, serosal surfaces, and small blood vessels, where they can activate complement
  • An inflammatory reaction ensues (~10 days) with resulting fever, urticaria, arthralgias, lymphadenopathy, and proteinuria
  • Inflammation in and around vessels causes an acute necrotizing vasculitis with fibrinoid deposition and acute inflammation (innocent bystander destruction)
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