Induction of CD39 by Foxp3. CD4⁺CD25⁻ mouse lymphocytes were infected with a retroviral construct encoding for Foxp3 and GFP (Foxp3/MIGR1) or a control construct encoding only GFP (MIGR1). At 7 days after infection, cells were stained with α-CD25, α-CD4, α-CD39, and α-CD39L1. Staining is shown versus GFP fluorescence, indicating infected cells. Numbers in end quadrant indicate percentage of total cells.