Hypersensitivity reaction

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  • Uncomfortable, damaging, and sometimes fatal reactions produced by the normal immune system including allergies and autoimmunity.

Clinical Features

Type Mechanism Example
I: Allergy, Immediate IgE-mediated degranulation of mast cells and basophils; usually happens after a first exposure which causes sensitization Urticaria, anaphylaxis, angioedema
II: Cytotoxic, Antibody Dependant IgG or IgM antibodies react with cell antigens with resultant complement activation Myasthenia gravis, goodpasture syndrome, erythroblastalis fetalis, AI hemolytic anemia, Graves disease
III: Immune Complex IgG immune complex deposition and subsequent complement activation Serum sickness, RA, SLE, poststreptococcal glomerulonephritis
IV: Cell-mediated, Delayed Activated T cells against cell surface antigens TB skin test, chronic transplant rejection, delayed drug rashes, contact dermatitis

See Also