Fig. 9

Ultrastructure of lung tissue from a healthy human (a and b) and human IPF lung explants. Human tissue was taken from previous studies [18, 42]. In a, an overview of a healthy interalveolar septa is shown separating three airspaces from each other. The AE2 cell has contact to two neighboring airspaces. At the junction of three septa, a corner vessel (cap) is visible. In b, a healthy AE2 cell is shown at higher magnification, demonstrating tightly packed lamellar bodies (LB), microvilli (mv), and tight junctions (tj). The mitochondria are not swollen. Within severely remodeled parenchymatous tissue from the IPF lung explant (c–e), lamellar body (LB) containing cells/alveolar epithelial cells can be identified without contact to the airspace on two-dimensional sections. C1–E1 show overviews. Corresponding C2–E2 depict detail images of these cells. In C1–E1, the rectangle gives an orientation where corresponding detail images were taken from. Besides LB, microvilli (mv) can also be observed in C2. In D2, the AE2 cell forms a tight junction (tj) with an alveolar epithelial type 1 (AE1) cell. The apical membrane can be identified by the presence of microvilli (mv), directed to a space which contains dense edema fluid (D2, ed). In E1, the AE2 cell also contains LB and forms tight junctions (tj) with neighboring cells. The airspace (air) is visible in E1 at the bottom. The AE1 cell is severely injured so that the basal lamina (bl) is denuded (asterisk). cap.: capillary lumen