FIGURE 1.

Exposure to asbestos or TiO₂ is distinguished by the recruitment of monocyte-derived alveolar macrophages (Mo-AMs) to the lung. IM: interstitial macrophage; SSC: side scatter; FSC: forward scatter; GFP: green fluorescent protein; MFI: median fluorescence intensity. a) Mice were administered crocidolite asbestos or TiO₂ (both at 100 µg intratracheally), and monocyte and macrophage populations were quantified by flow cytometry 14 days later (see supplementary figure S1a and b for gating strategy and quantification of other myeloid cell populations). b) Representative contour plots gated on AMs (CD64⁺Siglec F⁺) from asbestos- or TiO₂-treated animals. c) Quantification of Siglec F^low and Siglec F^high AMs from naive, TiO₂- or asbestos-exposed animals according to gating in (b). d) Schematic of the experimental design for (e). e) Cx3cr1^ER-Cre×ZsGreen mice were treated with tamoxifen, and the percentage of GFP⁺ classical monocytes, IMs and AMs was assessed by flow cytometry. Representative histograms showing GFP expression are shown. f) Schematic of the experimental design for (g) and (h): lineage tracing system to track the ontogeny of AMs after intratracheal administration of asbestos or TiO₂. Cx3cr1^ER-Cre×ZsGreen mice were treated with asbestos or TiO₂ and tamoxifen was administered as two boluses at days 7 and 8. The number of GFP⁺ AMs was analysed 7 days later. g) Representative contour plots and h) quantification of GFP⁺ Mo-AMs after asbestos or TiO₂ exposure. i) Representative histograms and MFI demonstrating expression of Siglec F and CD11b on Mo-AMs 14 days after exposure to asbestos. All data are presented as mean±sem. n=4–5 mice per group. One-way ANOVA with the Tukey–Kramer test for multiple comparisons. *: p<0.05; **: p<0.01; ***: p<0.001; ****: p<0.0001. Representative data from two independent experiments.