Effect of inflammation and Epo injections on serum IFN-γ levels and BFU-E numbers in bone marrow and spleen. (A) Serum concentrations of IFN-γ in ZIGI mice, either nontreated (−Epo) or after Epo injections (+Epo). In the latter case, serum IFN-γ determinations were performed at the usual time points (Z9Epo1, Z12Epo4, and Z17Epo9). Data are the mean from 2 to 6 pools of 2 sera each. Errors bars represent SEM. (B-E) Analysis of BFU-E expansion from bone marrow (B-D) and spleen (C-E) in different groups of mice. (B-C) A total of 1.5 × 10⁴ bone marrow (B) and 3 × 10⁵ splenocytes (C) cells were plated in methylcellulose media containing 3 U/mL Epo (spleen) or 3 U/mL Epo plus 10 ng/mL IL-3 (bone marrow) and BFU-E were scored after 5 days (spleen) or 8 days (bone marrow). The pictures (inset) show typical BFU-E colony from an Epo1 bone marrow (B) or from a Z9Epo1 spleen (C). Photographs of BFU-E colonies were taken with a camera Control Pro (Nikon). (D-E) To test the IFN-γ effect on BFU-E proliferation, a total of 1.5 × 10⁴ bone marrow cells (D) and 3 × 10⁵ splenocytes (E) cells from 3 different Epo1 mice were plated in methylcellulose media containing 3 U/mL Epo (spleen) or 3 U/mL Epo plus 10 ng/mL IL-3 (bone marrow), in the presence (+IFN-γ) or absence (−IFN-γ) of 2000 U/mL IFN-γ in the media. Three independent mice were analyzed for each condition. Errors bars represent SEM. Significant differences were found only in the bone marrow when analyzed by Student paired t test.