Presence of IL-10–expressing macrophages in the vicinity of LCH cells in bone and lymph node lesions but not in isolated skin lesions.

(A) Frozen sections from skin lesion (patient 6423), eosinophilic granuloma of the bone (patient 7553), and a lesional lymph node (patient 6193) were fixed in acetone and stained with anti-Langerin (mouse IgG1) revealed with a goat F(ab)2 antimouse IgG and with anti–IL-10 (rat IgG) and streptavidin-Cy3 and examined by confocal microscopy. Only faint background staining with anti–IL-10 was detectable in the epidermis (arrow) and dermis of the skin lesion (upper panel, magnification × 40). Similar results were observed in 3 patients with isolated skin disease. At the same magnification, relatively numerous cells stained with anti–IL-10 were readily detectable (in red) within eosinophilic granuloma (middle panel). Although faint IL-10 staining may be observed in some Langerin-stained cells, most frequently, IL-10 and Langerin staining did not colocalize. Similar results were observed in 3 patients with bone disease. A similar pattern is also observed in lymph node section (lower panel), shown at a higher magnification (× 100) to illustrate that Langerin positive cells display virtually no staining for IL-10, whereas the Langerin⁻ large-sized cells in their close vicinity strongly express IL-10. (B) Frozen sections from eosinophilic granuloma of the bone (patient 10337) were stained with FITC-conjugated anti-Langerin (DCGM-5, mouse IgG1), PE-conjugated CD68 (Pharmingen) and with anti–IL-10 (rat IgG) and streptavidin-Cy5 and examined by confocal microscopy. Cells that stained strongly for IL-10 (blue) also stained strongly for CD68 (red) and appeared purple, whereas Langerin-stained cells (green) display weaker CD68 expression and no or very weak IL-10 staining.