CD38 expression in Ki-67⁺ and Ki-67⁻ CLL cells and ²H enrichment in CLL clonal fractions sorted based on CD38 and Ki-67. (A) PBMCs from CLL 822 were incubated with fluorochrome-labeled mAbs reactive with CD19, CD5, and CD38, and, after cell permeabilization, with Ki-67. Cells were first gated for CD19 and then analyzed as reported in the figure. (Top plot) CLL clone contains ∼ 5% Ki-67⁺ cells. (Bottom plots) Percentage of CD38⁺ cells in the CD19⁺CD5⁺Ki-67⁺ fraction (83%; bottom right) is much higher compared with that observed in the CD19⁺CD5⁺Ki-67⁻ fraction (18%; bottom left). CLL cells from CLL 452 (B) and CLL 625 (C) were flow-sorted based on CD38 and Ki-67 expression, and ²H-labeled DNA was measured in the sorted fractions. Curves represent the fraction (f) of labeled cells reported in the tables. Ki-67⁺ cells, both CD38⁻ and CD38⁺, incorporated more ²H than their Ki-67⁻ counterparts.