Variability of PTPγ expression in tissue macrophages. Sections were obtained from normal lung (A), a patient with foreign body reaction to oil-based contrast media (B), and a patient with mycobacterial lymphadenitis (C). In normal lung, strong PTPγ reactivity was observed in the cytoplasm of alveolar macrophages, some of them showing obvious anthracosis (arrowheads). In nodal foreign body reaction, numerous PTPγ⁺ sinus macrophages were present; no PTPγ reactivity was observed in numerous multinucleated giant cells surrounding lipidic drops (B, arrowheads). In mycobacterial lymphadenitis, only rare PTPγ cells were found outside the granuloma, and no staining was observed in epithelioid macrophages (C, asterisks). Indirect immunoperoxidase technique was applied, and nuclei were counterstained with hematoxylin.