Quantitation of Siglec-F ligands in airway epithelial cells and peribronchial inflammatory cells in WT and Siglec-F deficient mice challenged with IL-4, IL-13 or TNF-α. WT or Siglec-F deficient mice were administered either IL-4, IL-13, TNF-α, or PBS diluent control. Twenty four hours after each individual cytokine or diluent challenge, the mice were sacrificed. BAL was obtained for determination of eosinophil and neutrophil cell counts, and the lungs were processed for immunohistology to detect Siglec-F ligand expression and MBP+ peribronchial eosinophils using a light microscope objective at 20×. Administration of either IL-4 (p < 0.001, WT; p < 0.001, Siglec-F deficient) or IL-13 (p < 0.001, WT; p < 0.001, Siglec-F deficient) induced a similar significant increase in levels of Siglec-F ligand expression by peribronchial cells (Fig 7A-C, 7E). In contrast, administration of TNF-α induced a small increase in peribronchial Siglec-F ligands (p < 0.01)(Fig 7E), but did not significantly increase Siglec-F ligand expression by airway epithelium in either WT or Siglec-F deficient mice (p = ns) (Fig 7 D, 7F). Administration of either IL-4 (p < 0.001 WT; p < 0.001 Siglec-F deficient) or IL-13 (p < 0.001 WT; p < 0.001 Siglec-F deficient) induced significantly increased levels of Siglec-F ligand expression by airway epithelium (Fig 7A-C, 7F). Although both IL-4 and IL-13 induced strong upregulation of Siglec-F ligand expression by airway epithelium (Fig 7F), levels of Siglec-F ligands in airway epithelium were slightly lower in Siglec-F deficient vs WT mice induced by IL-13 (p = 0.02) but not IL-4 (p = 0.10) (Fig 7F). IL-4 induced the strongest eosinophil response in BAL (WT p < 0.03; Siglec-F deficient p = 0.02)(Fig 7G) and lung (WT p < 0.001; Siglec-F deficient p < 0.001)(Fig 7H), while IL-13 and TNF-α induced a weaker eosinophil response in BAL (Fig 7G) and lung (Fig 7H). TNF-α, but not IL-4 or IL-13, induced a strong neutrophil response in BAL in both WT (p = 0.03) and Siglec-F deficient mice (p = 0.03) (Fig 7I)(n = 3 mice/group).