Skin involvement after 7 days of thymic stromal lymphopoietin (TSLP) treatment in wild-type (WT) and IL-4Rα1–deficient mice. A–C, Representative images of hematoxylin and eosin–stained skin sections from a phosphate buffered saline (PBS)–treated wild-type mouse, showing preservation of all skin layers (A), a TSLP-treated wild-type mouse, showing cell infiltration (B), and a TSLP-treated IL-4Rα1−/− mouse, showing intense cell infiltration (C). Original magnification × 10. D–F, Representative images of CD163-stained skin sections from a PBS-treated wild-type mouse (D), a TSLP-treated wild-type mouse, showing strong CD163 staining in brown on cells in the subcutaneous layer (E), and a TSLP-treated IL-4Rα1−/− mouse, showing CD163-positive staining similar to that in E (F). Original magnification × 10. G–N, Expression of mRNA for interleukin-13 (IL-13) (G), CCL2 (H), arginase 1 (Arg1) (I), matrix metalloproteinase 12 (MMP-12) (J), IL-1α (K), type 2 nitric oxide synthase (NOS2) (L), plasminogen activator inhibitor 1 (PAI-1) (M), and osteopontin (SPP1) (N). Bars show the mean ± SEM fold change normalized to mRNA expression in 1 PBS-treated wild-type mouse sample (n = 3 samples per group).