Anaphylaxis IgE — FRCA Primary MCQ
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Correct answer: E — IgE
The correct answer is E, IgE. In classic immediate allergic anaphylaxis, prior sensitisation produces antigen-specific IgE, which binds high-affinity FcεRI receptors on mast cells and basophils. Re-exposure cross-links receptor-bound IgE, causing cellular activation and release of mediators including histamine, tryptase, leukotrienes and prostaglandins. These produce vasodilatation, increased vascular permeability, bronchospasm and other manifestations of anaphylaxis. IgG is the most plausible distractor because uncommon IgG-associated immune mechanisms have been described, but IgE is the predominant immunoglobulin in allergic perioperative anaphylaxis. IgA, IgD and IgM do not mediate the classic type I hypersensitivity mechanism. Not all perioperative anaphylaxis is IgE-mediated; non-IgE mast-cell activation can produce an indistinguishable clinical syndrome.
Reference: Egner W, Cook TM, Garcez T, et al. Specialist perioperative allergy clinic services in the UK 2018: Results from the Royal College of Anaesthetists Sixth National Audit Project (NAP6) investigation of perioperative anaphylaxis. Clinical & Experimental Allergy. 2018;48:846–861. https://pubmed.ncbi.nlm.nih.gov/27181074/