Increased 67LR expression in circulating CD34⁺ cells after G-CSF administration is significantly correlated with mobilization efficiency. (A) Percentage of 67LR-expressing CD34⁺ cells in PBMNCs collectd from 35 healthy donors before G-CSF administration (day 0, ▪) or at the time of cell harvesting (day 5, □). Mean percentages ± SEM of 67LR⁺ circulating CD34⁺ cells were 2.36% ± 0.4% before G-CSF administration and 42.4% ± 4.1% on the day of cell harvesting (P < .001). (B) 67LR expressing CD34⁺ cells/μLin PBMNCs collected from 35 healthy donors at the time of cell harvesting (day 5 of G-CSF administration, □) and the corresponding peak value of CD34⁺ cells/μl (▤). Mean ± SEM of 67LR⁺ circulating CD34⁺ cells was 0.11 ± 0.02/μL before G-CSF administration and 29.6 ± 4.2/μL on the day of cell harvesting (P < .001). (A, B) Four of 5 poorly mobilizing donors (*) did not show 67LR increase in circulating CD34⁺ cells. (C) Pearson linear regression analysis between percentages of 67LR-expressing PB CD34⁺ cells/μL after G-CSF administration and PB CD34⁺ cell peak values on the day of collection (r = 0.5, P = .002). Percentages of 67LR⁺ circulating CD34⁺ cells are significantly correlated with the degree of mobilization.