Gdf15 signaling is required for recovery from PHZ induced acute anemia. (A) Steady-state erythropoiesis is represented by red blood cell (RBC) counts, hemoglobin (Hb) concentrations, and hematocrit levels. n = 9 for WT and n = 11 for Gdf15^−/−. Data are shown as individual subject and the mean ± standard error of the mean (SEM). (B-F) Analysis of recovery from PHZ-induced acute anemia. (B) Survival analysis of WT and Gdf15^−/− after receiving different doses of PHZ with P = .0019 when Gdf15^−/− is compared with control (Gehan-Breslow-Wilcoxon test). (C) Hematocrit levels during the entire recovery period. Each time point reflects >5 mice analyzed. Data are shown as the mean ± SEM. (D) Spleen weights at key time points during recovery. (E-F) Spleen stress BFU-E assay was conducted at key time points following PHZ injection. (E) Quantification of stress BFU-E colonies. (F) Representative images of stress BFU-E colonies of WT and Gdf15^−/− mice. Pictures were taken with 40× magnification using an Olympus CK40 microscope. Each time point reflects >3 mice analyzed. Data are shown as individual subject and the mean ± SEM. *P < .05, **P < .01, and ***P < .001.