A 48-year-old man presents with a 3-month history of persistent dry cough, fatigue, and unintentional weight loss. Chest imaging reveals bilateral hilar lymphadenopathy. Transbronchial lung biopsy demonstrates collections of activated macrophages with an epithelioid appearance surrounded by lymphocytes, consistent with noncaseating granulomas. Which cytokine, produced by which T cell subset, is most critical in promoting the macrophage activation that leads to granuloma formation in this patient?