Fig. 1.

Non-phagocytic resolution phase macrophages express IFN-β. a, b Male mice were injected intraperitoneally with zymosan A (1 mg/mouse) followed by an injection of PKH2-PCL at 62 h. After 4 h, the peritoneal cells were recovered and immuno-stained for F4/80 and CD11b. Then, F4/80⁺ macrophages were sorted based on the extent of PKH2-PCL acquisition (PKH2 + /− populations; >98% purity) using the FACSAria III sorter (illustrated in (a). The collected cells were immediately used for RNA extraction (with RNA integrity value above 7.5), and a gene expression microarray analysis was performed using Illumina hiSeq 2500. Differential gene expression analysis and gene ontology (GO) enrichment were performed for genes that were significantly upregulated (b, left panel) or downregulated (b, right panel) in non-phagocytic/satiated (PKH2-PCL^lo) macrophages in comparison to phagocytic (PKH2-PCL^hi) ones. The results indicate the statistical significance of the GO term and the percentage of enrichment is presented. c–e Expression of IFN-β and ISG15 in sorted satiated and phagocytic macrophages. Representative results (c) and mean ± SEM (d, e) for three independent experiments. *P < 0.05 (Student’s t test). g, h Peritoneal exudates were collected from unchallenged mice (0 h) or following peritonitis for 4–96 h. IFN-β content in cell-free fluids was determined by ELISA (f). Results are mean ± SEM from three (24, 72, 96 h) or four (0, 4, 48 h) mice. *P < 0.05, **P < 0.01, ***P < 0.005 (Tukey’s HSD). Alternatively, resolution phase macrophages were recovered 66 h post peritonitis initiation (PPI) and incubated with TGF-β (5 ng/ml), poly (I:C) (4 μg/ml) or apoptotic cells (AC, at a ratio of 1:5) for 24 h. Culture supernatants were then collected and IFN-β content was measured (g). Culture media from apoptotic cells served as control. Results are representative from three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.005 (Tukey’s HSD). Source data are provided as a Source Data file