At day 25 after HSCT, a total of 18 mice (from 2 independent experiments) were randomly assigned to ibrutinib (25 mg/kg/d), 18 to vehicle, and 11 to cyclosporine (10 mg/kg/d). Sclerodermatous lesions, hair loss, hunched posture, and gaunt appearance are characteristic visual indicators of cGVHD in this model. (A) Representative visual analysis of 4 randomly selected mice at day 39 after HSCT. (B) H&E-stained skin preparations of sclerodermatous skin lesions showing levels of dermal fibrosis, epidermal hyperplasia, serocellular crusting, erosion, and lymphohistiocytic infiltration, consistent with cGVHD. Original magnification, ×200. (C) Pathologic cGVHD involvement of the skin was independently assessed on a scale from 0 to 8 for each mouse. Cohort averages are displayed. *P < 0.05. Error bars indicate SEM.