Keratin 7 in the lining alveolar epithelium of the lung (human, adult)

Stain: anti-keratin 7 antibody (Pan-Ck 7) immunoperoxidase staining (with aminoethylcarbazole (AEC) substrate). Both alveolar epithelial cell types I (1) and II (2) stain dark brown-red after the reaction with AEC indicating a positive reaction for cytokeratin 7. Note the white (non-stained) capillaries (↓) sandwiched between the red-brown reacting alveolar epithelial cells (air-blood exchange). Within the alveolar lumen alveolar macrophages (M) appear negative for keratin 7. This antibody can be used in the study of alveolar developmental processes in the lung, or of various types of bronchial carcinoma as well in the differential diagnosis between various types of carcinoma in the lungs.