Figure 2.

Chitin-bearing organisms are detected in the lung after chronic Aspergillus fumigatus exposure. C57BL/6 wild-type (WT), Chia^−/−, and acidic mammalian chitinase overexpressing (SPAM) mice were intratracheally challenged with 1 × 10⁷ resting or swollen A. fumigatus conidia for 2 h or subjected to the experimental allergic fungal asthma model as in materials and methods. Lungs were collected, fixed, paraffin-embedded, and sectioned. Deparaffinized sections were stained using a Calcofluor White Stain Kit (Fisher Scientific Cat. No. R40015) according to manufacturer’s instructions. Sections were imaged using a Nikon Eclipse Ti2 fluorescent inverted microscope with NIS Elements imaging software (v.5.30.06). Representative images (from 3 separate experiments with n = 3 mice/experiment) are shown for naïve mice (A), mice that received resting conidia (with yellow arrows marking chitin-positive conidia (B), mice that received swollen conidia (with red arrows marking chitin-positive swollen conidia) (C), mice subjected to allergic fungal asthma (with green arrows marking chitin-positive conidia) (D), SPAM mice subjected to allergic fungal asthma (E), and Chia^−/− mice subjected to allergic fungal asthma (F, with green arrows marking chitin-positive conidia). Original magnification ×20. Scale bar = 100 μm. [Image created with BioRender.com.]