Which mediator, along with histamine, contributes to bronchospasm and vascular changes in allergic reactions?

• A. Epinephrine
• B. Histamine
• C. Leukotrienes
• D. Sepsis

Answer: (C)

Leukotrienes. In allergic reactions, after IgE on mast cells and eosinophils are activated, leukotrienes produced from arachidonic acid — especially LTC4, LTD4, and LTE4 — contribute to bronchospasm and increased vascular permeability. They are potent and longer-lasting bronchoconstrictors than histamine, helping drive the sustained airway constriction and edema seen in the reaction's later phase. This complementary action to histamine explains why both mediators together amplify vascular changes and bronchial narrowing. Epinephrine tends to counteract bronchospasm, and sepsis is not involved in allergic mediator production, while histamine alone doesn’t account for the prolonged bronchoconstriction that leukotrienes produce.