Infused WT macrophages reside and proliferate in the liver of Hmox1^−/−mice to recycle senescent RBCs and rescue the Hmox1-deficient disease. (A) A model which illustrates that Hmox1^−/− mice, which lack erythrophagocytic macrophages, are unable to recycle iron from senescent RBCs that then rupture in the blood vessels, leading to intravascular hemolysis, microcytic anemia, and iron overload in kidneys. (B) Infused WT macrophages engraft and proliferate in the liver, recycle senescent RBCs, restore systemic iron homeostasis, preventing intravascular hemolysis and tissue damage.