The clearance time of infused hematopoietic stem cell from the blood circulation

There is no detailed information about the clearance time of infused hematopoietic stem cell (HSC) from the blood circulation in humans. In this prospective study, peripheral blood CD34+ cell counts were detected during the 4 days period following autologous HSC transplantation in 20 patients by means of flow cytometry. The median CD34+ cells were at the highest level in the first hour and decreased below pre-infusion values on the first day after HSC infusion. By nonparametric analysis, positive correlation was found between CD34+ cell levels at the first hour and the post-thaw CD34+ cell dose (r = 0.57, p = 0.01). An inverse correlation was determined between CD34+ cell levels at the first hour and neutrophil engraftment (r = −0.54, p = 0.01). Compared with the patients having CD34+ cell count of ⩾2 μL−1 in the first hour following HSC infusion, the patients having CD34+ cell count of <2 μL−1 had delayed both neutrophil (20 vs. 12, p = 0.008) and platelet (47 vs. 11, p = 0.01) engraftments. Our results indicated that infused HSCs were removed from the blood circulation within 1 day. In addition, CD34+ cell levels at the first hour may be used as an important indicator to predict the delay of neutrophil and platelet engraftments.