Hypersensitivity Types — ORE Part 1 MCQ
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Correct answer: B — Type I is immediate and IgE-mediated; type II is cytotoxic and IgG/IgM-mediated
Type I hypersensitivity is an immediate reaction mediated by allergen-specific IgE on mast cells and basophils; it can present rapidly with urticaria, angioedema, bronchospasm or anaphylaxis, for example after latex exposure. Type II hypersensitivity is antibody-mediated: IgG or IgM binds antigens on cells or tissues, causing injury through complement activation or antibody-dependent cellular cytotoxicity. Therefore B is correct. B incorrectly assigns delayed T-cell-mediated reactivity to type I and IgE-mediated immediate reactivity to type II. Delayed contact allergy to dental materials is classically type IV, not type II. C and D misclassify type III immune-complex reactions, while E again incorrectly describes type II as delayed T-cell-mediated.
Reference: Uzzaman A, Cho SH. Chapter 28: Classification of hypersensitivity reactions. Allergy Asthma Proceedings. 2012. https://pubmed.ncbi.nlm.nih.gov/22794701/