Ki-67 expression in CD5⁺B cells from healthy elderly donors and patients with CLL. PBMCs from 20 healthy elderly donors and 95 patients with CLL were analyzed for expression of CD5, CD38, CD19, and Ki-67. (A) Percentage of CD5⁺CD19⁺ cells from healthy controls and patients with CLL expressing Ki-67 (P < .001; Mann-Whitney test). (B) Percentage of CD38⁺ B cells in CLL clones designated CD38^low (55 of 95) and CD38^high (40 of 95) based on a 30% cut-off. (C) Significant differences in Ki-67 expression between CD38^low and CD38^high patients with CLL (P < .001; Mann-Whitney test). Horizontal lines in panels A and B indicate averages of values in corresponding groups.