Figure 3. Neutrophil-specific loss of Sema3f results in more rapid neutrophil recruitment to and clearance from the lungs in a murine acute lung injury model.

(A and B) Fold change in Sema3f and Nrp2 gene expression following acute lung injury with LPS. Mice were sacrificed at 6, 24, and 48 hours after instillation. BAL neutrophils were collected and cDNA was extracted. TaqMan analysis of cDNA was performed with data normalized to murine Actb gene expression. Data are mean ± SEM of fold change compared with peripheral blood neutrophils (T0 PB) from 2 individual experiments (n = 4–6). An acute lung injury was induced by intratracheal LPS instillation, mice were sacrificed at 24 hours, and lung sections were stained for expression of the Ly6G neutrophil marker and SEMA3F (C), NRP1, and NRP2 (D). Scale bars: 50 μm. (E and F) Sema3f^fl/flMrp8Cre^–/– (WT) and Sema3f^fl/flMrp8Cre^+/– (KO) mice were challenged with LPS, sacrificed at 2, 6, 24, and 48 hours, and BAL fluid was obtained. Cell counts were performed by hemocytometer and the differential cell count was established by cytospins. Time to 50% reduction in peak neutrophil number was calculated individually for each genotype (T₅₀) (E). BAL fluid IgM content was measured by ELISA. Data are shown as log-transformed fold change from WT (F). Apoptosis was assessed by morphology, with data as mean ± SEM (G) from 3 individual experiments (n = 6–12). Statistical analysis was by 1-way ANOVA and Bonferroni’s post hoc test (A and B) and 2-way ANOVA with Sidak’s post hoc test (E–G). *P < 0.05; **P < 0.01; ***P < 0.001.