Type I Hypersensitivity — MFDS Part 1 MCQ
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Correct answer: B — IgE
IgE is the immunoglobulin that mediates classical type I hypersensitivity. During sensitisation, allergen-specific IgE binds high-affinity Fc-epsilon-RI receptors on mast cells and basophils. Re-exposure causes cross-linking of receptor-bound IgE, triggering degranulation and release of histamine and other inflammatory mediators responsible for the immediate response. IgG commonly participates in type II antibody-mediated reactions and type III immune-complex reactions. IgM may also contribute to type II reactions and complement activation. IgA is predominantly associated with mucosal immunity, while IgD mainly functions as a receptor on naïve B lymphocytes. Therefore, A is the single best answer.
Reference: Vitte J, et al. Allergy, Anaphylaxis, and Nonallergic Hypersensitivity: IgE, Mast Cells, and Beyond. Medical Principles and Practice. 2022;31(6):501–515. https://pubmed.ncbi.nlm.nih.gov/36219943/