KLF4-deficient neutrophils exhibited impaired function ex vivo. (A) Wild-type bone marrow neutrophils (BMNs) showed increased KLF4 expression after 30-minute LPS stimulation. (B) LPS-induced MMP-9 mRNA expression was blunted in KLF4-deficient BMNs. (C-D) The secreted MMP-9 and MPO in the condition medium from BMNs stimulated with LPS or E coli were measured by ELISA. (E) Caspase-3 activation in neutrophils assessed by western blot and fluorescent enzymatic activity assay. BMNs were incubated in culture medium without (Control) or with E coli (E. coli) for 2 hours at 37°C. (F) Extracellular ROS generation from Cre and K4-cKO BMNs in response to fMLF was determined by kinetic absorbance OD₅₅₀. (G) KLF4-deficient neutrophils were defective in bacterial killing assay. The images on the left are 1× scans of 10-cm dishes. (H) LPS-induced iKBα phosphorylation and degradation. (I) LPS-induced gene expression of IκBα and TNF-α was attenuated in KLF4-deficient neutrophils. (J) CD14 mRNA expression in neutrophils. (K) CD14 protein expression on neutrophil cell surface as measured by flow cytometry. All gene expression levels were determined by qPCR. n = 3 to 5 in each group. *P < .05.