A 43-year-old man has had a cough and fever for the past 2 months. A chest radiograph shows bilateral nodular densities, some with calcification, located mainly in the upper lobes of the lungs. A transbronchial lung biopsy is performed, yielding a specimen with the microscopic appearance shown. Which of the following chemical mediators is most important in the pathogenesis of this lesion?

• Complement C5a
• Interferon-γ
• Bradykinin
• Nitric oxide

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