CD68-GFP mice display increased GFP expression during monocyte-to-macrophage differentiation compared with CX₃CR1^GFP mice. Bone marrow monocytes isolated from CD68-GFP and CX₃CR1^GFP mice using negative immunomagnetic selection were cultured in vitro in macrophage colony-stimulating factor containing media. (A) Images taken across 5 days indicate GFP expression is maintained and increased as CD68-GFP monocytes differentiate. In contrast, monocytes isolated from CX₃CR1^GFP reporter mice showed loss of GFP fluorescence over this time course. Representative images are shown; similar results were obtained with monocytes from 2 independent mice (scale bar = 40 µm). (B-C) Flow cytometry analysis was also carried out to confirm GFP expression levels and macrophage differentiation using F4/80 and 7/4. (D) CD68-GFP and WT mice were injected intraperitoneally with 100 µg zymosan. Mice were euthanized at 96 hours, and a representative flow cytometry plot of peritoneal macrophages using F4/80 and 7/4 and GFP expression is shown (Analysis was carried out in 3 to 4 mice.)