Fig. 1

NET-forming neutrophils and NETs in sputum samples of COPD subjects stained with anti-NE (green) and PI (red). a non-activated neutrophil with lobulated nucleus and cytoplasmic localisation of NE. (B-D) activated neutrophils at different stages of NET formation. b nucleus swollen, NE staining still confined to cytoplasm. c NE present in both, cytoplasm and nucleus. d ruptured cell in early phase of NET release. e, f Representative examples of NET morphology. NETs are characterised by extensive colocalisation of DNA and NE (the lack of absolute DNA-NE overlap is explainable by the irregular molecular structure of NETs [24], and by secondary alteration this structure during sputum transport). e Long stretch of NET-DNA (arrow) extending between two dense aggregates. In part of the motif, overlap of DNA stain and NE stain is illustrated by stippled lines. f Clusters of NET-DNA, cell debris and an intact neutrophil (asterisk) connected by thin NET trajectories (arrows)