In tuberculosis granulomas, which cell type forms the core along with macrophages and lymphocytes?

• A. B cells
• B. T lymphocytes
• C. Activated macrophages
• D. Epithelial cells

Answer: (C)

Tuberculosis granulomas are driven by a Th1-type immune response that activates macrophages. These recruited macrophages become epithelioid histiocytes, taking on an elongated, epithelial-like appearance, and they often fuse to form Langhans giant cells. This activated-macrophage population constitutes the cellular core of the granuloma, usually with caseating necrosis in the center. Surrounding this core is a mantle of T lymphocytes that sustains the activation, while B cells are not a defining component of the granuloma core. Since the key central cells are the activated macrophages (epithelioid histiocytes), they best fit the description of forming the core along with the macrophages and the surrounding lymphocytes.