HS4E4V. Immunohistochemical staining of E13.5 - E21.5 normal lungs and E15.5 - E21.5 hypoplastic lungs with HS4E4V. In normal lungs, the HS4E4V HS epitope is present in epithelial basement membranes and the surrounding mesenchyme, particularly in sub-epithelial areas adjacent to distal airways. In hypoplastic lungs, expression of this epitope is severely reduced, particularly in epithelial basement membranes and mesenchyme of E15.5 and E17.5 lungs. As a negative control, endogenous HS was digested with heparitinase prior to antibody incubation. (aw) airway, (oe) oesophagus, (mes) mesenchyme, (ep) epithelium, (bm) basement membrane, (br) bronchus.