Frequency of CAFCs. CAFC frequency of CD34⁺ cells from healthy donors (n = 3) that were exposed to imatinib at the concentrations ranging from 0 to 10 μM for 5 weeks. The frequency of CAFCs was calculated with L-Calc software (StemCell Technologies). The relative progenitor frequency as compared to untreated cells for every single donor as well as the mean (horizontal bar) is shown.