Kinetics of CD38⁺ and CD38⁻ CLL cells in each patient studied. Curves represent the fraction (f) of labeled cells at the 3 time points studied. Note that different levels of ²H enrichment were observed among patients, and the graphs have different scales. Vertical dotted lines indicate the end of ²H₂O assumption. Based on the slopes of the CD38⁺ and CD38⁻ kinetic curves, 2 groups of patients were defined, A and B. (A) In group A, CD38⁺ cells rapidly achieve maximal ²H enrichment levels at the end of the labeling period; ²H incorporation in these cells subsequently falls during washout. (B) Patients in group B are characterized by similar kinetic patterns of both CD38⁺ and CD38⁻ fractions with delayed appearance and slow achievement of maximal levels of labeled cells.