Fig. 2.

Leukocytes localized to occlusive lesions and areas of smooth muscle hypertrophy in human PAH lung tissue. Hematopoietic cells were identified in lung tissue by antibody staining to detect CD45 and vascular structures by α-SMA. DAPI was used as the nuclear stain. Large normal vessels and tissue (A–D) had less CD45 reactivity than the PAH vessels and parenchymal tissue (E–H). Arterioles from PAH tissue (M–P) had CD45 localized to the smooth muscle layers, whereas none was detected in the control (I–L). High levels of CD45 expression were detected in occlusive lesions (Q–T). Scale bars = 75 μm. Insets: enlarged panels of CD45 staining.