PTPγ expression in lymphoid organs and skin. Sections were obtained from spleen (A), human tonsil (B), lymph node (C-D), skin (E), and thymus (F-H). In the spleen, PTPγ⁺ stained tingible body macrophages of a B-cell follicle and macrophages (white arrowhead) and sinus lining cells (black arrowheads) in the red pulp (A;Gc indicates germinal center; Mz: marginal zone). Double immunofluorescence staining shows that all PTPγ⁺ found in the B-cell follicle coexpressed CD11c on the plasma membrane (B), and some of them clustered with CD3⁺ germinal center T-cells (B, inset). PTPγ⁺ cells with dendritic morphology are obvious in the interfollicular (IF) area, highlighted by the presence of high endothelial venules (C, black arrowhead) and in most DC-SIGN⁺ sinus macrophages (D, yellow cells). In normal skin, PTPγ⁺⁺ positivity was diffuse in the epidermis; in the dermis, scattered PTPγ⁺⁺ cells were observed, most of which showed an irregular morphology and coexpressed DC-SIGN (E, yellow cells). In normal thymus, scattered PTPγ⁺⁺ cells were observed in the cortex (Tc) and in the medulla (Tm) (F), highlighted by the presence of Hassal bodies (arrowhead); no reactivity was observed on most thymocytes (F-H). PTPγ⁺⁺ cells were irregular in morphology and showed abundant cytoplasm (F-H), and some of them coexpressed DC-SIGN (F, inset). PTPγ positivity was absent on CD123⁺ plasmacytoid dendritic cells (G) and in DC-LAMP⁺ mature dendritic cells (H) populating the thymic medulla. Indirect immunoperoxidase technique was applied, and nuclei were counterstained with hematoxylin (A, C, F). Double immunofluorescence was performed using FITC- and Texas red–conjugated secondary antibodies, as labeled (B, D-E, G-H).