Figure 3

The spatial distribution of HS epitopes changes during mammalian lung morphogenesis. Antibody epitopes change in their pattern of distribution during the course of lung development. For example, the epitope recognised by HS3A8V is displayed exclusively by the epithelial basement membranes at E13.5, however, by E15.5, it is also present in the mesenchyme and on the surface of epithelial cells. At E17.5, the epitope is lost from the epithelium, and sub-epithelial mesenchymal expression is briefly increased, before becoming more widespread at E19.5 - E21.5. In contrast, the HS epitope recognised by EW4G1V is not present in E13.5 rat lungs and is only weakly expressed at E15.5 in epithelial basement membranes and mesenchyme surrounding smaller distal airways. Levels of this epitope increase considerably in epithelial basement membranes at E17.5, while mesenchymal expression remains relatively low and concentrated in sub-epithelial areas until E19.5 - E21.5, where epitope distribution becomes more widespread. E13.5 - E21.3 rat lungs were probed with HS antibodies followed by rabbit VSV-G tag antibody and FITC conjugated goat anti-rabbit IgG. Scale bar represents 10 μm and all images are the same magnification. (aw) airway, (bm) basement membrane, (me) mesenchyme, (ep) epithelium.