Ki-67 expression in relation to density of CD38. PBMCs from patients with CLL were stained as described for Figure 1, and contour plots depicting expression of CD5 and CD38 in CD19⁺ cells of patients with CLL were generated. (A) The CD38⁺ fraction was divided into 3 regions—R4, R5, and R6—referred to as CD38^low, CD38^int, and CD38^high, respectively. Percentages of Ki-67–expressing cells were scored only if at least 50 cells fell within marked regions. (B) Percentages of Ki-67–expressing cells in CD38^low, CD38^int, and CD38^high subsets from 60 of 95 patients with CLL. Horizontal lines indicate averages of values in corresponding populations. (C) Average (± SE) of values from panel B. (D) Lines connect data points depicting percent Ki-67⁺ cells in each CD38 subset for each of 60 patients with CLL. (E) In every patient studied, CD5⁺Ki-67⁺ cells showed higher density of CD38 compared with CD5⁺Ki-67⁻ cells from the same case.