c-kit<sup>+</sup> cells in the angioobliterative lesions were not mast cells.

<p>Representative optical section obtained by confocal microscopy demonstrates the presence of mast cells (c-kit<sup>+</sup> mast cell tryptase<sup>+</sup>, arrows) around the airway mucosa of SU5416/chronic hypoxia (SuHx) animal at day 21 (positive control). In a naïve control lung, only one isolated c-kit<sup>+</sup> mast cell tryptase<sup>−</sup> cell was present in the pulmonary artery (open arrow). One cell with faint granular green autofluorescence (likely a macrophage) was present in the alveolar space (double-headed arrow). No mast cells were seen in the lumen-obliterating lesions of SuHx animals at day 21, only c-kit<sup>+</sup> mast cell tryptase<sup>−</sup> cells (open arrows). A single cell with faint granular green autofluorescence was seen in the alveolar space, likely a macrophage (double-headed arrow). Nuclear counterstaining: 4',6-diamidino-2-phenylindole (DAPI). Magnification: 630×. Scale bar: 20 µm.</p>