DTR-expressing macrophages are found in multiple organs. A through D, Immunohistochemistry for GFP in lung (A), liver (B), and atherosclerotic plaque (C and D) demonstrating GFP-positive macrophages in all organs (arrowheads). C through F, ApoE−/− mice were irradiated and transplanted at 8 weeks of age with CD11b-DTR/apoE−/− marrow and 10 ng/g DT or saline control injected 3 times weekly until 22 weeks. DT reduced the percentage of GFP-positive macrophages (compare F vs control [D]). D and F, Higher-power views of areas outlined in C and E. Scale bars: 200 μm (C and E); and 50 μm (D and F).