Hypersensitivity is an exaggerated immune response to an antigen, causing damage to the host. It can be classified into four types: Type I (immediate), Type II (cytotoxic), Type III (immune complex-mediated), and Type IV (delayed-type).
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Type I hypersensitivity involves IgE antibodies and is commonly associated with allergies.
Type II hypersensitivity is mediated by IgG or IgM antibodies targeting cell surface or matrix antigens, leading to cell destruction.
Type III hypersensitivity occurs when immune complexes deposit in tissues, causing inflammation and tissue damage.
Type IV hypersensitivity is a T-cell mediated response that typically takes 48-72 hours to develop.
Common examples of hypersensitivity reactions include allergic rhinitis, hemolytic anemia, serum sickness, and contact dermatitis.
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Related terms
Allergen: A substance that can cause an allergic reaction.
Autoimmunity: A condition in which the immune system attacks the body's own tissues.