A Patient with Chest Pain

A 35-year-old man presents to emergency department with complaints of left-sided substernal chest pain and dyspnea that has started 30 minutes ago. The pain is stable in intensity, is not exacerbated by inspiration or movement and radiates to the left arm and lower jaw. The patient's medical history includes postprandial abdominal pain, significant weight loss (>10 pounds) during the last 2 months, muscular aches, night sweats and a recent episode of testicular torsion. Vital signs are as follows: 80/50 mmHg, 97.7°F, 110 bpm, 90% blood O2 saturation in room air and 20 respirations/min. Electrocardiogram (ECG) shows ST elevation in leads V1 and V2, arterial blood gas (ABG) values are completely normal and cardiac Troponin I is elevated. Invasive coronary angiography reveals multiple microaneurysms at the proximal left anterior descending artery, with thrombus formation occluding its entire lumen. The lesions are eventually treated with percutaneous coronary intervention (PCI) and the patient recovers. Considering the medical history of the patient, mesenteric angiography is ordered as well. It demonstrates multiple microaneurysms at the superior mesenteric artery. Diagnosis of polyarteritis nodosa is made, and intravenous treatment with methylprednisolone and cyclophosphamide is started.

Which of the following mechanisms characterizes polyarteritis nodosa?

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