Systematic Investigation of the Location of <scp>CD34</scp> + Cells Within the Mononuclear Cell Layer of Hematopoietic Progenitor Cell Collections in Normal Donors

With hematopoietic progenitor cell (HPC) collections by apheresis, it is not clear whether CD34+ cells inhabit a specific density within the mononuclear cell (MNC) interface. This study was undertaken to see whether this could be determined by targeting a specific depth in the interface as determined by the colorgram level. In 90 National Marrow Donor Program HPC collections using the continuous MNC procedure of the Spectra Optia device, the level of the MNC layer targeted for collection was systematically rotated between three different colorgram levels. Relevant collection characteristics, collection efficiencies (CE), and a novel measure, the CD34+ enrichment ratio, were compared between the three colorgram levels using one-way ANOVA. Validating the colorgram level targeting, the product Hct was significantly different between the three colorgram levels. CD34+ CE2 and the CD34+ enrichment ratio trended higher with a lower Hct level. Lymphocyte CE1 trended higher with a higher Hct level. Our results are consistent with the hypothesis that CD34+ cells layer higher than lymphocytes in the collection interface, and that CD34+ cells may perhaps be more precisely targeted by collecting lighter in the collection interface. Our results pave the groundwork for further study with a more precise CD34+ CE1 calculation.