FIG. 3.

Addition of pAsc at later stages of OP9-DL1 cultures induces T-cell maturation, and the DP population requires continual exposure to pAsc for maintenance. LSK-Thy-1.1-neg cells cultured in an MEM with 1 ng/ml IL-7 and 5 ng/ml Flt3L were maintained for 14 days in the absence of ascorbate, with passages every 3–4 days as described in the Materials and Methods section. Cultures were supplemented with 30 μM pAsc beginning at 14 days. On the final passage at day 23, replicate cultures were established in which pAsc was either included or not for the final 3 days of culture. All cultures were analyzed after 26 days.