Figure 3.

IHC staining for claudin-1, -2, -3, -4, -5, and -7 in a patient with usual interstitial pneumonia (UIP). Metaplastic epithelium overlying remodeled and fibrotic alveolar walls (arrows) are positive for claudin-1 (A), claudin-2 (B), claudin-3 (C), and claudin-4 (D). (E) Claudin-5 is strongly positive in the endothelium of a remodeled artery (arrow) and capillaries of alveolar wall (arrowhead). Claudin-5 also shows a weak positive staining in the metaplastic epithelium of fibrotic alveolar wall (large arrow). (F) Metaplastic epithelium overlying a fibroblast focus within alveolar wall is positive for claudin-7 (arrow). Bar = 50 μm.