IL-13 receptors are expressed by tumor cells in the skin lesions of CTCL patients and in the peripheral blood CD4⁺ T cells of Sézary patients. (A) Expression by immunohistochemistry of IL-13Rα1 (upper panel) and IL-13Rα2 (lower panel) in biopsies from CTCL and normal skin (original magnification ×400). Representative examples are shown (n = 17 CTCL, n = 3 NS). (B) The percentages of IL-13⁺, IL-13Rα1⁺, and IL-13Rα2⁺ cells in CTCL skin biopsies at different disease stages are shown. Error bars are mean ± SD. (C) Representative examples of IL-13Rα1 or IL-13Rα2 costaining with CD4 or TOX by immunofluorescence of frozen CTCL skin biopsies (original magnification ×1000, n = 7). Flow cytometry expression of IL-13Rα1 (D) or IL-13Rα2 (E) in CD4⁺ T cells from the peripheral blood of SS patients. Representative examples out of 5 SS patients tested.