Figure 1.

Mouse lung immunofluorescence. Cx3cr1-CreERT2: R26-loxp-STOP-loxp-TdTomato (Tandem dimer Tomato) mice were treated with tamoxifen for Cre activation and intratracheal bleomycin to induce lung injury, and lung sections were prepared in the fibrotic period, at 14 days. The two photos show the same microscopic field, with (right) and without (left) SiglecF (Sialic acid binding Ig-like lectin F) fluorescence. TdTomato⁺ monocyte-derived macrophages (moMacs) localize to Pdgfrb⁺ (Platelet-derived growth factor receptor beta) fibroblasts in the fibrotic niche, expressing some level of the resident macrophage marker SiglecF. Alveolar macrophages, which express SiglecF but not the Cx3cr1 marker TdTomato, lie outside the fibrotic niche. Scale bar, 50 mm. Reprinted by permission from Reference 25.