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TRAFFICKING OF CD34+ CELLS INTO THE PERIPHERAL CIRCULATION DURING COLLECTION OF PERIPHERAL BLOOD STEM CELLS BY APHERESIS

*Yu J, Rowley S, Gooley T, Shelly H, Homberg L, Bensinger WI

*Congqing Children’s Hospital, Chongqing, China

Clinical Research Division, FHCRC, Seattle, USA

Objective: The number of CD34+ cells collected during apheresis does not affect the apheresis procedure is related to the volume of blood processed. In large-volume apheresis (LVL) procedure, more cells can be collected than were originally present in the peripheral blood.

Methods: We studied LVL for 21 patients with acute myelogenous leukemia or multiple myeloma, who were undergoing peripheral blood stem cell (PBSC) collection after mobilization for autologous transplantation.

Results: These patients experienced a slow decline in blood CD34+ cell concentrations during the apheresis procedure. No patient demonstrated a sustained rise in CD34+ cell counts as a result of the procedure. The number of CD34+ cells collected exceeded the number in the blood at the start of the procedure by an average of 3.9-fold. The efficiency of collection for CD34+ cells averaged 92.6% and did not vary by speed of blood processing, diagnosis, or mobilization regimen. The calculated release of CD34+ cells from other reservoirs into the peripheral blood averaged 3.71 x 10⁶/min (range, 0.36-13.7 x 10⁶/min), and was highly correlated (r = 0.82) with the concentration of these cells in the blood at the start of the procedure.

Conclusions: These data show that apheresis does not affect the release of CD34+ cells in a cytokine-treated patient. LVL will result in collection of larger quantities of CD34+ cells than procedures involving processing of smaller volumes of blood, but the number of cells collected is limited by the rate of release of these cells into the blood where they are accessible for collection.