Effect of Spi-B on cell survival.

Spi-B– or control-transduced CD34⁺CD1⁻ and CD34⁺CD1⁺ postnatal thymocytes were cultured in the presence of SCF and IL-7. In this cytokine combination most cells generated from both CD34⁺ populations express CD4 and CD8α, indicating that the cytokines induce committed T-cell precursors in this culture period.52 After 7 days, the percentage of apoptotic cells was determined by FACS analysis on annexin V and 7-AAD.