Treatment of erythroleukemic mice with Epo results in accumulation of stem/progenitor Sca1⁺ cells and immune cells. At 6 weeks after F-MuLV infection, mice were separated into 2 experimental groups and injected intraperitoneally with PBS or 100 IU recombinant human Epo (3 times a week for a 2-week period). Simultaneously, a control group of uninfected age-matched mice were treated with PBS for the same time period. (A) Sixty days after infection, mice were bled from tail veins and hematocrit values were measured and represented as the mean ± SEM. **P < .005. (B) Spleens from all groups were harvested 60 days after infection, and their weight measurements are represented as the mean ± SEM. **P < .005.