Hypersensitivity reaction
Background
- 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
References
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