Infused macrophages repopulate and proliferate in the liver. (A) Scheme of BrdU injection. Two doses of BrdU (100 mg/kg) were injected intraperitoneally at 72 and 24 hours, respectively, before tissue harvest (22 weeks after macrophage infusion) to label proliferating cells. (B) The immunofluorescence of Hmox1 and BrdU was detected in the livers of WT (top panel) and Hmox1 KO (bottom panel) mice infused with macrophages. DAPI for nucleus was used as the counterstaining. White arrows indicate Kupffer cells that costained with BrdU, Hmox1, and DAPI. Two representative BrdU-labeled macrophages were shown. Scale bar, 10 μm.