Figure 2.

Bacterial load in lungs, blood, spleen and lung tissue damage in myeloid KLF4 knockout and KLF4 wildtype mice 24 hours after transnasal infection with S. pneumoniae. Myeloid KLF4 knockout (mKLF4 KO, KO) and KLF4 wildtype (mKLF4 WT, WT) mice were transnasally inoculated with 5x10⁵ CFU NCTC 7978 pneumococci (A–I) or PBS (E–H). 24 hours after inoculation venous blood was sampled, BAL was performed and mice were sacrificed. Bacterial CFUs were determined from lung homogenates (A), venous blood (B) and spleen homogenates (C) (lower limit of detection lung/spleen homogenates 50 cfu/ml, venous blood 10 cfu/ml, dotted line). Murine albumin (MA) in BALF and plasma was quantified using ELISA (E). Whole lung sections were stained using a polyclonal antibody against S. pneumoniae (D) or hematoxylin & eosin (F–I) and semiquantitatively scored for bacterial count (D), perivascular edema formation (F), pleuritis formation (G) and necrosis formation (H). Graphs show boxplots with min to max whiskers on base-10 log scale of 5 mice, each (A, C), boxplots with min to max whiskers on base-10 log scale of 11 mice (mKLF4 WT) or 12 mice (mKLF4 KO) (B), median with interquartile range of 4 mice, each (D, F–H), or boxplots with min to max whiskers on linear scale of 6 mice, each (E). (I) shows representative sections of lung tissue of mKLF4 KO mice 24 hours after infection with S. pneumoniae (hematoxylin & eosin staining). # PMN infiltrate, ∆ necrosis formation, § suppurative bronchopneumonia, * perivascular edema formation, ▲ pleuritis formation. Scale bars: 100 µm upper and lower left, 20 µm upper right, and 50 µm lower right picture. Statistics: Mann-Whitney U test (A–E), or Kruskal-Wallis test with Dunn multiple-comparisons test (F–H). *p < 0.05, **p < 0.01, *** < 0.001, n.s., not significant; N.D., not detectable.