Figure 1.

Airway expression of forkhead box protein A2 (FOXA2) is inversely correlated with mucin abundance in canine pulmonary mycosis. Paraffin-embedded lung sections from healthy and fungal-infected animals were stained with Grocott methenamine silver (GMS), periodic acid-Schiff (PAS), and immunohistochemistry (IHC) for the presence of fungal pathogens and the expression of FOXA2 and mucins. Healthy control lung sections stained negative for fungal organisms and mucin secretion with GMS and PAS, with strong expression of FOXA2 in bronchial surface epithelia (black arrows). Fungal-infected canine lungs were positive for yeast bodies under GMS staining (black spots; black arrows) in the submucosa and bronchial lumens, accompanied by positive PAS staining (pink spots; black arrows) in surface epithelia, which colocalized to the regions expressing MUC5AC and MUC5B in IHC (black arrows). FOXA2 expression was down-regulated in the bronchial surface epithelia of the infected lung tissues (black arrows), with successful positive controls shown in basal epithelial cells (red arrows). Additional images can be found in the Supplemental Figure S2. Scale bars = 50 μm.