Q. A 25-year-old female presents to the emergency department with a rash and difficulty breathing. The patient reports that she recently underwent a surgical procedure and was prescribed cephalexin for post-operative prophylaxis. She reports that she noticed a rash on her arms and legs, which then spread to her chest and back. She also reports difficulty breathing, with wheezing and shortness of breath. The patient has no significant medical history and no known drug allergies. On physical examination, she appears uncomfortable and is experiencing labored breathing. Her vital signs are blood pressure of 130/80 mm Hg, heart rate of 110/min, respiratory rate of 24/min, and an oxygen saturation of 90 percent on room air. A diffuse maculopapular rash is noted on her arms, legs, chest, and back. Lung auscultation reveals diffuse expiratory wheezes. You order a chest X-ray to rule out any underlying pulmonary disease, which appears normal. Blood work shows an elevated white blood cell count, and antibody titers indicate a type II hypersensitivity reaction, which was most likely caused by the recent administration of cephalexin. Which of the following mechanisms is LEAST likely to have played a role in this patient’s symptoms?