CCR6 and CCR7 expression in histiocytic processes.

(A-H) Serial sections of LCH-involved lymph node, demonstrating coexpression of CCR6 and CCR7 by CD1a⁺ pathologic LCs. (A) Hematoxylin and eosin. (B) Anti-CD1a. (C) Anti-CCR6 showing pathologic LCs staining with variable intensities. (D) Anti-CCR7 showing uniform staining of all pathologic LCs (note endothelial cell staining as well). (E) Anti-CCR6 at high power showing typical LCH lesional cells all staining for CCR6. (F) Anti-CCR7 at high power showing cells in the same field and having the same morphology as those in panel E staining for CCR7. (G) IgG_2B isotype control for anti-CCR6. (H) IgG₁ isotype control for anti-CCR7. (I-L) Serial sections of RDD-involved lymph node, demonstrating coexpression of CCR6 and CCR7 in areas containing S100⁺ RDD histiocytes. (I) Hematoxylin and eosin. (J) Anti-S100. (K) anti-CCR6. (L) Anti-CCR7. Note reactive germinal center in the lower right portion of panels I-L in which B cells are CCR6⁻ and CCR7⁺. (M-N) Serial sections of HPS-involved soft tissue, demonstrating coexpression of CCR6 and CCR7 by histiocytes. (M) Anti-CCR6. (N) Anti-CCR7; note large, intensely positive histiocytes in panels M and N. All panels are original magnification × 400, except for E and F, which are × 1000.