Collection and recruitment of CD34+ cells during large-volume leukapheresis.

Although sufficient progenitor cells for hematopoietic rescue following high-dose therapy may be obtained in a single leukapheresis, the majority of patients require multiple procedures. In an attempt to minimize the number of leukapheresis and maximize collection efficiency, we undertook large-volume leukapheresis in 17 patients with a variety of hematologic malignancies. Twenty-four procedures were performed over a 6-h period, with a mean of 21 L of blood processed. By employing a modified collection set, three separate 2-h collection bags were analyzed for a number of variables. CD34+ cells are collected at a steady rate throughout the procedure, with no evidence of exhaustion of progenitor cells. There was evidence of progenitor cell recruitment, with 1.4-fold more CD34+ cells in the collected product than were present in the blood at the beginning of the procedure. Initiation of leukapheresis was based on the blood CD34+ count, and this value was strongly correlated with the number of CD34+ cells in the collected product. The procedure is safe and relatively simple and minimizes the number of leukaphereses required to collect adequate progenitors for autologous transplantation.