Type | Description | Mechanism | Clinical features |
I Immediate reaction (30 to 60 min) Accelerated reaction (1 to 72 hours) | Anaphylactic, immediate-type hypersensitivity | Antigen exposure causes release of vasoactive substances, such as histamine, prostaglandins, and leukotrienes from mast cells or basophils. This response is usually, but not always, IgE-dependent. | Anaphylaxis Angioedema Bronchospasm Urticaria (hives) |
II | Antibody-dependent cytotoxicity | An antigen or hapten that is intimately associated with a cell binds to antibody, leading to cell or tissue injury. | Hemolytic anemia Interstitial nephritis |
III | Immune complex disease | Damage is caused by formation or deposition of antigen-antibody complexes in vessels or tissue. | Serum sickness |
IV | Cell-mediated or delayed hypersensitivity | Antigen exposure sensitizes T cells, which then mediate tissue injury. | Contact dermatitis |
V (>72 hours) | Uncertain, but probably involving T cell cytotoxicity. | Maculopapular rash |
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