Figure 4

Immunohistochemical staining for claudins 1, 3, 4, 5 and 7 in the alveolar period i.e. weeks 36-40. 4A-4B. Epithelium of alveoli is negative for claudin-1. Scale bar = 80 μm in the Fig 4A, scale bar = 25 μm in the Fig 4B. 4C, 4D, 4E: Type II pneumocytes of alveoli (arrows) and epithelium of bronchioles (short arrows) are positive for claudin-3 (4C) and claudin-4 (4D, 4E). Scale bar = 80 μm in the Figs 4C and 4 D, scale bar = 25 μm in the Fig 4E. 4F. Endothelial cells of alveolar capillaries (arrow) and an artery (arrowhead), and bronchiolar cells (short arrow) are positive for claudin-5, whereas alveolar epithelium is not. Scale bar = 80 μm. 4G: Epithelium of a bronchiole (short arrow) and type II pneumocytes of alveoli (arrow) are positive for claudin-7. Scale bar = 80 μm. 4H. Negative control in which the primary antibody has been substituted with PBS with haematoxylin counterstain. Scale bar = 80 μm.