L-selectin is required for host defense during K pneumoniae–induced pneumonia. (A-I) WT and Sell^−/− mice were subjected to K pneumoniae intratracheal injection. Bacterial burden in terms of CFU in blood (A), lung (B), BALF (C), and spleen (D), as well as neutrophil recruitment into the alveoli (E) and lung tissue (F), were determined 24 hours after Kpneumoniae injection. Representative hematoxylin and eosin staining of the lung of WT (G) and Sell^−/− (H) mice 24 h after intratracheal instillation with K pneumoniae (scale bars, 50 µm). (I) Survival of WT and Sell^−/− mice after K pneumoniae intratracheal injection. n = 8 mice per genotype. Data are mean ± standard error of the mean. *P = .05, **P = .01, Student t test and log-rank (Mantel-Cox) test.