Neutrophils ingest and degrade DNA. (A) Heat map of proteins with DNase activity in neutrophils from BM or BAL. (B) Western blot (TREX1 and DNASE3L1) and ELISA (WRN) analysis of BAL neutrophils compared with BM neutrophils assessing differential protein expression. (C) Bioanalyzer tracings of supernatant after incubation of salmon sperm nuclei either without (top) or with (bottom) BAL neutrophils. The sharp spikes in the tracing without neutrophils represent standards. (D) Ingestion of nuclei by neutrophils. Neutrophils were incubated with Sytox-labeled salmon sperm DNA for 1 hour and neutrophils were stained with anti-Ly6g. Scale bar, 25 μm. Images of neutrophils having taken up DNA are shown. (E) Neutrophils from injured lungs exposed to Sytox through the intratracheal route were recovered by BAL, and stained with anti-Ly6g compared with WT neutrophils. (F) Frames (original magnification ×20) from supplemental Video 1 showing neutrophil engulfment of DNA debris in real time. (G) MyD88^−/− neutrophils were impaired in their ability to degrade DNA as assessed by agarose gel. (H) Heatmap of nucleic acid–sensing pattern-recognition receptors in BAL-derived neutrophils compared with BM-derived neutrophils after acid instillation. (I) Histologic section 96 hours after acid injury in a G-CSF^−/− mouse, which shows that repair is impaired (left). G-CSF^−/− mice were given recombinant Dornase-α (50 μg) via the intranasal route 24 and 48 hours after injury and the degree of repair is markedly improved (right). Scale bar, 100 μm; hematoxylin and eosin stain. Each point on the graphs represents 1 animal. The error bars represent the standard error of mean.