Telomerase in CD34⁺/CD38⁺ and CD34⁺/CD38⁻ cells. (A) Telomerase activity in CD34⁺/CD38⁺ and CD34⁺/CD38⁻ cells on days 3, 5, and 7 of ex vivo expansion culture. Telomerase was upregulated to a higher extent in CD34⁺/CD38⁺ cells compared with the more quiescent CD34⁺/CD38⁻ population. Both fractions when stimulated with multiple cytokines (K36EG, F36EG, KF36EG) as opposed to KL + IL-6 or KL + IL-6 + sIL-6R resulted in an increased telomerase expression. (B) Telomerase activity at baseline with telomerase confined to CD34⁺/CD38⁺ cells and absent in CD34⁺/CD38⁻ fraction is diplayed. After 1 week of ex vivo expansion, telomerase upregulation using combinations of KL + IL-6 was increased in CD34⁺/CD38⁺ cells compared with CD34⁺/CD38⁻ cells. This was even more pronounced when cytokine combinations of KF36EG were used. Lane 1: CD34⁺/CD38⁻ fraction at baseline (day 0) [no telomerase activity]; lane 2: CD34⁺/CD38⁺ fraction at baseline (day 0) [telomerase activity]; lane 3: CD34⁺/CD38⁻ fraction, 7 days in ex vivo expansion (day 7) with KL + IL-6; lane 4: CD34⁺/CD38⁺, 7 days in ex vivo expansion (day 7) with KL + IL-6; lanes 5 to 7: CD34⁺/CD38⁻ fraction on day 3 (lane 5), day 5 (lane 6), and day 7 (lane 7) of ex vivo exansion with KF36EG; lanes 8 to 10: CD34⁺/CD38⁺ fraction on day 3 (lane 8), 5 (lane 9), and 7 (lane 10) with KF36EG.