Overexpression of IL-13 promotes disease progression, whereas reduction of IL-13/IL-4 signaling ameliorates MF in vivo. (A) Schematic of experiment. (B) IL-13 levels in the BM of control (Ctrl-GFP) or IL-13 overexpressing (IL13-GFP) mice. (C) WBC counts in control and IL-13 overexpressing mice. (D) Spleen weights of indicated mice. (E) Percentage of megakaryocytes (CD41⁺) in the BM of control and IL-13 overexpressing mice. (F) Levels of active TGF-β in the BM of the indicated mice. (G) Hematoxylin and eosin (H&E) and reticulin staining of BM sections from Ctrl-GFP and IL13-GFP mice. Fibrosis scoring for all mice in the experiment is shown (right). (H) Schematic of the experimental setup. (I) Survival analysis of mice transplanted with Il4ra WT or KO cells. P value from the log-rank (Mantel-Cox) test is shown. WBC counts (J) and percentage of GFP⁺ cells (K) in peripheral blood are shown from indicated mice. (L) Spleen and liver weight of indicated mice. P value from unpaired Student t test is shown. (M) Representative images of BM sections stained with H&E and reticulin of indicated mice. Scale bar, 50 μm. Fibrosis scores are shown (right). In all graphs, the data represent the average ± SEM. eGFP, enhanced green fluorescent protein; H&E, hematoxylin and eosin; WBC, white blood cell count; WBM, whole bone marrow.