Immunohistochemical findings. (A) Numerous SMA-positive myofibroblasts (intense) were present in airway lumens (Scale bar = 100 μm). (B) TGF-β-positive lymphocytes and macrophages (moderate) were sporadically seen in the fibrous tissue of BO lesions (Scale bar = 20 μm). (C) CD34-positive cells (moderate) were mainly distributed in the peribronchiolar lesions (Scale bar = 100 μm). (D) D2-40-positive cells (intense) were uniformly distributed in the bronchiolar lumens and peribronchiolar lesions (Scale bar = 100 μm).