Immunostaining of platelet endothelial cell adhesion molecule-1 (PECAM-1). Lung sections from fetuses aged 32–33 weeks (fetal age) without (A, control lung) or with (B, CDH, and C, urogenital defect) LH were immunostained with mouse monoclonal anti-human PECAM-1 antibody and counterstained with hematoxylin. All pictures are at same magnification. Control fetuses had extensive staining of endothelial cells within septa, whereas immunostaining appeared less intense in the hypoplastic lungs that displayed reduced complex intertwining of alveolar capillaries.