WT macrophage infusion increased iron levels and rescued microcytic anemia of Hmox1 KO mice. (A) Hematocrits, (B) hemoglobin, (C) MCV, (D) MCH, and (E) RDW-CV of WT and Hmox1^−/− (KO) mice without or with macrophage infusion (WT+M and KO+M). (F) Serum iron, (G) TIBC, and (H) Tf saturation of WT and Hmox1 KO mice before and after infusion with macrophages for 12 weeks. (I) Total iron contents per million RBCs of WT and Hmox1 KO mice without or with macrophage infusion for 12 weeks. Iron contents were measured with inductively coupled plasma mass spectrometry. (J) TfR1 levels on reticulocytes of peripheral blood of WT and Hmox1 KO mice without or with macrophage infusion for 12 weeks. TfR1 levels were measured with flow cytometry, then the fluorescence intensity was normalized to WT control group. Mean ± SD; statistical analyses were performed using 2-way ANOVA (multiple comparisons). The graphs were created with GraphPad Prism software. *P < .05, **P < .01, ***P < .001, ****P < .0001.