DISTRIBUTION OF MOBILIZED PROGENITOR CELLS IN THE BUFFY COAT OF THE HEMONETICS MCS3P CELL SEPARATOR - A STUDY TO OPTIMIZE THE COLLECTION OFPROGENITORS BY LEUKAPHERESIS

Hematopoietic progenitor and stem cells for transplantation can be mob ilized into the circulation and collected by leukapheresis. In this pr ocedure, the leukocytes are distributed in the buffy coat along a dens ity gradient, and the composition of the final product depends on whic h layer was collected. For the Haemonetics MCS3p Cell Separator, the m anufacturer recommended starting the progenitor cell collection at a l ight transmission of 30%-40% (compared with plasma) and continue it fo r 40-50 ml. To optimize the use of this machine, the buffy coat it pro duces was studied in 12 patients by collecting it in fractions of incr easing specific weight. Each fraction was analyzed by morphology, immu nocytometry, and cell culture. We found that the buffy coat uniformly contains 8 times more leukocytes than blood, but the proportion of eac h white cell type varies along a gradient. The lymphocyte-predominant lighter layers are richer in CD34+ cells when compared with the granul ocyte-predominant denser layers (6-14 times versus 2-4 times more than blood). The majority of CD34+ cells are found at a light transmission of 10%-70% (hematocrit 6-9). We conclude that cells for transplantati on should be collected in a lighter fraction of the buffy coat than or iginally suggested by the manufacturer.