S100A9-expressing PMNs found in human pathological granulomas. (A-B) Sections of formalin-fixed, paraffin-embedded pathological lung tissues derived from patients with tuberculosis were labeled with either anti-human S100A9 (B) or control mAb (A), followed by HRP-DAB-based detection as described in “Methods.” Asterisks indicate the necrotic area at the center of the granuloma. Scale bars, 200 μm. (C) A magnified view of G213-reactive cells (arrowheads) observed in panel B indicated that the stained cells were PMNs. Scale bar, 5 μm.