Figure 2

Characteristics of tissue indoleamine 2,3-dioxygenase (IDO) immunostaining. (A) Clustering of red staining IDO-positive cells within a melanoma-draining lymph node. The cells demonstrate a monocytoid or plasmacytoid morphology, with eccentrically placed nuclei and scant granular cytoplasm. In areas, these cells mold around surrounding lymphocytes. Bar = 20 μm. (B) Distribution of red staining IDO-positive cells in the lymphoid regions (deep purple) adjacent to the central medullary sinuses (geographic pink regions harboring macrophages). Bar = 140 μm. (C) Control IDO staining of minimally immunostimulated human pharyngeal tonsil. Only scattered red staining IDO-positive cells are identified. Bar = 100 μm. (D) Collections of red staining IDO-positive cells in the inflammatory mantle (bottom) of a cutaneous melanoma primary (top). Dark brown melanin is seen in the interface tissue between tumor and underlying inflammatory response. Bar = 60 μm. (E) Perivascular cuffing by IDO-positive cells in inflammatory milieu of cutaneous primary. Small vessel with spiraling endothelial cells surrounded by red staining plasmacytoid cells. Cutaneous Pacinian corpuscle identified in upper-right corner. Bar = 36 μm. (F) Focal red IDO staining of melanoma tumor cells in a pattern suggestive of clonal expansion. Dark brown melanin identified at interface with IDO-negative tumor cells. Bar = 100 μm. (G) Red staining IDO-positive cells within the inflammatory mantle (center) of an advancing melanoma nodal metastasis (left). Note that the majority of IDO-positive cells intermingle with nodal lymphocytes (right). Bar = 50 μm. H) Dual immunostaining for IDO (red) and HAM56 (brown). The nature of the brown diaminobenzidine (Dako) immunostaining within the more abundant cytoplasm of the macrophages makes it impossible to rule out low-level co-expression of IDO in these cells. The intense IDO staining, however, was confined to the plasmacytoid cells. Bar = 25 μm. (I) S-100 immunostaining of dendritic cells within melanoma-draining lymph node. The red staining is seen in larger cells that are heterogeneous in size and shape. These cells have abundant cytoplasm that extensively interdigitate with surrounding lymphocytes bar = 42 μm. J) Red staining S-100–positive dendritic cells occupy a peripheral perifollicular nodal location, in contrast to the central perisinusoidal distribution of IDO-positive cells. Bar = 350 μm. (K) Dual immunostaining for IDO (brown) and kappa/lambda light chains (κ/λ)(blue) within a perisinusoidal region. Note that each differentially stained population of cells has a plasmacytoid appearance. Bar = 26 μm. (L) Dual immunofluorescence for IDO (red) and κ/λ (green) confirms the presence of distinct cellular populations. Bar = 26 μm.