Hypersensitivity and Autoimmunity · USMLE Step 1

A patient develops urticaria after receiving radiocontrast dye. Which mediator is primarily released during this reaction?

  1. Interleukin-2
  2. Histamine
  3. Interferon-gamma
  4. TNF-alpha
Show answer and explanation

Correct answer: Histamine

Histamine is released from mast cells during IgE-mediated Type I hypersensitivity reactions. It causes vasodilation and itching.

Difficulty: Medium Question 18 of 20

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