Which immunoglobulin causes secretion of histamines, leukotrienes and prostaglandins during a hypersensitivity reaction?

• A. IgG
• B. IgE
• C. IgM
• D. IgA

Answer: (B)

IgE-mediated activation of mast cells and basophils drives this mediator release. When an allergen is encountered, B cells switch to producing IgE that binds to high-affinity FcεRI receptors on these cells. On subsequent exposures, the allergen cross-links the bound IgE, triggering intracellular signaling that causes rapid degranulation and the production of lipid mediators. Histamine released from granules causes vasodilation and increased vascular permeability, contributing to swelling and redness, itching, and, in the airways, bronchoconstriction. In addition, leukotrienes and prostaglandins are produced and amplify inflammation, promoting further bronchoconstriction, mucus secretion, and vascular effects. This sequence is the classic Type I hypersensitivity reaction. Other antibody classes (like IgG or IgM) do not cause this immediate mast cell degranulation in the same way, and IgA does not primarily drive this rapid mediator release.