A 28-year-old woman with a peanut allergy accidentally ingests peanut-containing food and within minutes develops generalized urticaria, laryngeal edema, and hypotension. The immediate degranulation of mast cells in this reaction is triggered by which specific event?

• A IgG-mediated antibody-dependent cellular cytotoxicity
• B Direct binding of allergen to mast cell Toll-like receptors
• C Complement activation by allergen-immune complexes
• D Cross-linking of surface-bound IgE by allergen on FcεRI receptors ✓

Explanation

Type I hypersensitivity requires prior sensitization. Allergen cross-links IgE already bound to high-affinity FcεRI on mast cells, triggering immediate degranulation with histamine and leukotriene release. Option B describes innate immune recognition, not IgE-mediated anaphylaxis. Option C describes Type III hypersensitivity. Option A describes Type II hypersensitivity (ADCC).

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.