Fig. 1

Neutrophils and mononuclear phagocytes are expanded in the alveolar airspace following LPS inhalation. a Schematic overview of study design. Solid arrows denote LPS inhalation (red) or saline inhalation control (blue). Black arrows denote blood sampling. Dashed arrows denote BAL. b Flow cytometry of leukocyte preparations from SS-BAL, LPS-BAL, and HC blood. The CD45 versus SSC plot was used to define CD45⁺SSC^hi AM, CD45^loSSC^mid neutrophils and CD45⁺SSC^lo mononuclear cells (see also Supplementary Fig. 1). Monocyte/macrophages and DCs were negative for lineage markers CD3, CD19, CD20, and CD56 and expressed HLA-DR. Monocyte/macrophages were divided into CD14⁺⁺CD16⁻, CD14⁺⁺CD16⁺, and CD14^-CD16⁺⁺ populations analogous to blood classical, intermediate and non-classical monocytes. DCs within the CD14^-CD16⁻ gate were divided into subsets: Axl⁺Siglec6⁺ DC5s, CD11c^loCD123⁺ pDCs, CD1c⁺BTLA^lo-mid DC2/3s, and BTLA^hi DC1s. Plots are representative of n = 9 SS BAL and n = 10 LPS BAL. c Concentrations of neutrophil, monocyte/macrophage and DC subsets in SS-BAL and LPS BAL. Bars represent mean and lines SEM. p-values from unpaired t-tests of SS versus LPS are shown: “ns” p > 0.05, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. d Monocyte/macrophage and DC frequency in HC blood, SS-BAL and LPS-BAL as a proportion of SSC^lo MHC class II-expressing cells (not-including CD1c- DCs). e Concentration of selected leukocyte populations in peripheral blood at 2-h intervals following inhalation of saline (blue line) or LPS (red line). Data points show mean ± SEM for 3–5 participants. p-values from one-way ANOVA are shown. p-value representation is described in c