Iron binding to different lobes of Tf differentially affects red cell indices. Complete blood count (CBC) parameters from 2-month-old mice demonstrated significant increases in RBCs in the Tf^C-bl/C-bl mice relative to Tf^N-bl/N-bl and WT mice (A), significant decreases in Hb concentration in both the Tf^N-bl/N-bl and Tf^C-bl/C-bl mice relative to WT, with more pronounced decreases in the Tf^N-bl/N-bl mice (B), significant decreases in mean corpuscular volume (MCV) in both the Tf^N-bl/N-bl and Tf^C-bl/C-bl mice relative to WT, with more pronounced microcytosis in the Tf^C-bl/C-bl strain (C), significant decreases in mean cellular Hb (MCH) in the Tf^N-bl/N-bl and Tf^C-bl/C-bl mice relative to WT, with more pronounced decreases in the Tf^C-bl/C-bl mice (D), and no significant differences in mean corpuscular Hb concentration (MCHC) between strains (E). (F) Red cell lifespan assays, measuring the decrease in the percentage of biotinylated red cells over time, indicated no differences between strains. Data are presented as Tukey box and whisker plots or line graphs, with mean ± standard deviation values indicated for each time point. For CBC parameters, n = 13 to 18 females and 13 to 17 males per strain. For red cell lifespan assays, n = 3 to 6 mice per sex for WT and n = 3 to 4 mice per sex for mutant mice. Statistical significance was analyzed by Kruskal-Wallis or 1-way ANOVA for hematologic parameters and 2-way ANOVA with Geisser-Greenhouse correction for lifespan data. *P ≤ .05, **P ≤ .01, ****P ≤ .0001.