Trafficking of CD34(+) cells into the peripheral circulation during collection of peripheral blood stem cells by apheresis

The number of CD34(+) cells collected during apheresis is related to the vo lume of blood processed. tn large-volume apheresis (LVL) procedure, more ce lls can be collected than were originally present in the peripheral blood a t the start of the collection procedure. We prospectively studied the level s of CD34(+) cells in the blood and apheresis product during LVL procedures for 21 patients with acute myelogenous leukemia or multiple myeloma. These patients experienced a slow decline in blood CD34(+) cell concentrations d uring the apheresis procedure. No patient demonstrated a sustained rise in CD34(+) cell counts as a result of the procedure. The number of CD34(+) cel ls collected exceeded the number calculated to be in the peripheral blood a t the start of the procedure by an average of 3.0-fold. The efficiency of c ollection for CD34(+) cells averaged 92.6% and did not vary with speed of b lood processing, diagnosis, or mobilization regimen. The calculated release of CD34(+) cells from other reservoirs into the peripheral blood averaged 3.71 x 10(6)/min (range, 0.36-13.7 x 10(6)/min), and correlated (r = 0.82) with the concentration of these cells in the peripheral blood at the start of the procedure. These data show that the apheresis procedure used in this study does not affect the release of CD34(+) cells in a cytokine-treated p atient. 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 peripheral circulation where they are accessible for collection.