Constitutive IFN-γ exposure in vivo enhances RBC turnover and increases macrophage erythrophagocytosis. (A) Flow cytometric analysis of in vivo biotinylated peripheral blood using fluorescently labeled streptavidin and Ter119. Representative dot plots of day 17 after transfer are shown. (B) Turnover of in vivo biotinylated RBCs from WT, CD70TG, IFN-γ^−/−, and CD70TG*IFN-γ^−/− mice as measured by flow cytometry. (C) Turnover of adoptively transferred ex vivo biotinylated WT RBCs in WT, CD70TG, IFN-γ^−/−, and CD70TG*IFN-γ^−/− mice as measured by flow cytometry. (D) Major histocompatibility complex class II surface expression of splenic red pulp macrophages (F4/80⁺ CD11b^low) expressed as geometric MFI. (E) Uptake of CFSE-labeled erythrocytes by splenic red pulp macrophages (F4/80⁺) expressed as the ratio of CFSE geometric MFI compared with background. (E) Data are representative for 2 experiments. Data are mean ± SD for 4 mice (B-C), 3 mice (D), or duplicate analysis (E) per group. *Significant difference (P < .05) between CD70TG or CD70TG*IFN-γ^−/− mice and all other groups (1-way ANOVA with Bonferroni correction).