Clone

Prior to fluorochrome staining, FcRIII/II blocking was performed using the TrueStain fcX™ antibody (Biolegend, London, UK). Cell surface staining was done with anti-CD3 (clone 145-2C11), anti-CD4 (clone GK1.5), anti-CD8 (clone 53–6.7), anti-CD11b (clone M1/70), anti-CD11c (clone N418), anti-CD19 (clone 6D5), anti-CD26 (clone H194–112), anti-CD45 (clone 30-F11), anti-CD69 (clone H1.2F3), anti-CD172a (clone P84), anti-CD206 (clone C068C2), anti-EpCAM (clone G8.8), anti-F4/80 (clone BM8), anti-Ly6C (clone HK1.4), anti-Ly6G (clone 1A8), anti-MHC-I (clone AF6–88.5), anti-MHC-II (clone AF6–120.01), anti-NK1.1 (clone PK136), anti-PD-1 (clone 29F.1A12), anti-PD-L1 (clone 10F.9G2), anti-CD86 (clone GL-1), anti-CD40 (clone 3/23), anti-XCR1 (clone ZET; all BioLegend, London, UK) and anti-CD204 (clone 2F8, Biorad, Munich, Germany) antibodies, and Fixable Viability Dye (Thermo Fisher Scientific, Karlsruhe, Germany) was used to exclude dead cells. The gating strategy is depicted in Additional file 1: Figure S1. Intracellular staining was done for arginase-1 (Polyclonal Sheep IgG; R&D Systems, Minneapolis, USA) using the eBioscience™ FoxP3/Transcription Factor Staining Buffer Kit (Thermo Fisher Scientific, Karlsruhe, Germany). Data were acquired on a BD LSRFortessa system (BD Bioscience, Heidelberg, Germany) and analyzed with FlowJo X software (FLOWJO LLC, Ashland, OR, USA).

Flow cytometric analysis of monocytes was performed as previously described (11 (link)). To this end, cells were stained with the following monoclonal antibodies (BioLegend, Uithoorn, The Netherlands) in PBS supplemented with 0.1% BSA and 0.01% NaN₃: anti-human CD14-PE/Cy7 (clone: HCD14), anti-human CD16-APC/Cy7 (clone: 3G8), anti-human CD163-PE (clone GHI/61), anti-human CD192 (CCR2)-PerCP/Cy5.5 (clone: K036C2), and anti-human CX3CR1-FITC (clone: 2A9-1). Data were acquired on a FACS Canto II device (BD Bioscience) and analyzed using FlowJo® software (Tree Star, Ashland, OR).

Primary alveolar epithelial cells type II were isolated from ICR mice or AhR^–/– mice as previously reported.^{41 (link),42} Briefly, mice were perfused with 10 mL cold PBS through the right ventricle. Lungs were filled with 2 mL dispase (BD Bioscience, CA, USA) and low gelling temperature agarose (Sigma Aldrich, MO, USA) before lung tissues were incubated with 2 mL dispase in 37 °C for 20 min. Then, lung tissues were rubbed and the slurry was filtered through 70- and 40-μm nylon meshes (JETBIOFIL, China). The cells suspension was incubated with biotinylated anti-CD45 (Biolegend, clone 30-F11, Cat. 103104), anti-CD16/32 (BD Pharmingen^TM, clone 2.4G2, Cat. 553143), anti-CD31 (Biolegend, clone MEC13.3, Cat. 102504), anti-TER119 (Biolegend, clone TER119, Cat. 116204) and anti-CD104 (Biolegend, clone 346–11A, Cat. 123603) antibodies at 4 °C for 30 min and then Dynabeads^TM MyOne^TM streptavidin T1 magnetic beads (Thermo Fisher Scientific, Cat. 65601) were added to the cell suspension to exclude leukocytes, monocytes/macrophages, NK cells, neutrophils, endothelial cells and erythroid cells. Negative selection of fibroblasts was performed by adherence on non-coated plastic plates. Cell purity was assessed routinely by flow cytometry.