Persistence of BCR-ABL⁺ cells in primitive progenitor/stem cells in CML patients in CCR with imatinib mesylate treatment for 5 years. (A) Experimental procedures for isolating CD34⁺CD38⁺ and CD34⁺CD38⁻ cells by flow cytometry sorting followed by Q-PCR for BCR-ABL and BCR are shown. (B) The cumulative results for Q-PCR analysis for BCR-ABL levels in MNC, CD34⁺CD38⁺, and CD34⁺CD38⁻ cells in CML patients after 1 to 5 years of imatinib mesylate treatment are shown using box and whisker (Tukey) plots. Significance values comparing MNC and CD34⁺CD38⁻ cells are *.05 > P < .1, **P < .01, ***P < .001; comparing CD34⁺CD38⁺ and CD34⁺CD38⁻ cells are ^.05 > P < .1, ^P < .05.