GM-CSF induces IL-33 on alveolar type II cells and peritoneal, but not alveolar, macrophages.

<p>(<b>A</b>) IL-33 and IL-6 by ELISA from freeze-thaw alveolar macrophages stimulated <i>in vitro</i> for 24 h. (<b>B</b>) IL-33 by ELISA from freeze-thaw peritoneal macrophages stimulated <i>in vitro</i> for 6, 24 or 48 h. Images and data in <b>C–G</b> are obtained at 2 wk. (<b>C</b>) Representative lung section upon exposure to Ad/GM-CSF+0.2, stained with anti-IL-33 Ab (nuclear dark brown stain), showing IL-33 immunostaining in alveolar walls but not in bronchial epithelial cells (BEC), inflammatory cells (INF) or vascular endothelial cells (V) (x200); magnified image (on the right) shows IL-33^- alveolar macrophages (AM) and IL-33⁺ alveolar type II cells (ATII). (<b>D</b>) Representative images (x400) from adjacent lung sections stained with either anti-IL-33 Ab (left image, dark brown in the nucleus) or anti-pro-SPC Ab (middle image, red in the cytoplasm) and negative controls for IL-33 (top right) and pro-SPC (bottom right). (<b>E</b>) Enlarged images. (<b>F</b>) IL-33⁺ cell counts in the lung of WT mice (or IL-33 KO as negative control). (<b>G</b>) Representative images showing distinct intensity of IL-33 stain in Ad/− <i>versus</i> Ad/GM-CSF exposed mice. N = 6 wells/condition in <b>A,B</b> or N = 3–7 mice/group in <b>E</b>. * p<0.05 versus media or saline.