Correlation between leukemic burden and CD26⁺ SC in patients with CML. (A) The comparison of the percentage of CD26⁺ BM SC (of all CD34⁺/CD38⁻ cells) in patients with high white blood counts (WBC) at diagnosis (>150 G/L, n = 15, left bar) with that in patients in whom lower WBC were measured (<150, G/L, n = 23). (B) The correlation between WBC and the percentage of CD26⁺ SC in CML at diagnosis in all patients (n = 38) are shown. (C) The comparison of the percentage of CD26⁺ SC with the percentage of CD26⁺ progenitor cells (CD34⁺/CD38⁺) in patients with freshly diagnosed CML are shown. As is visible, CD26 is primarily expressed in the CD34⁺/CD38⁻ fraction of the leukemic clone.