Cells That Copurify with CD34 Cells

With the increased use of peripheral blood as the source of hematopoietic progenitor cells for transplantation and adoptive immunotherapy, there is interest in both the bystander cells that copurify with CD34 cells during processing and the effect these cells may have on hematopoietic engraftment, antitumor effect, and overall disease outcome (51-53). Both suppressor cells and NK cells have attracted interest, since they have repeatedly been im­ plicated in regulating immunological phenomena such as graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) after allogeneic and autol­ ogous transplantation, respectively (31,54-61). Apheresis samples from pa­ tients with non-Hodgkin’s lymphoma who were mobilized with rHuG-CSF were processed on a discontinuous density gradients ranging from 1.0520 to 1.0640 g/mL. Suppressor cell and NK cell activity was determined at the different interfaces by means of the mixed lymphocyte culture and chromium release assay, respectively. The results in Figure 5 show that more than 90% of suppressor cell activity is associated with cells that separate in a density range that is equal to or less than 1.0605 ± 0.0005 g/mL. The same is true for the distribution of NK cell activity (Fig. 6). CD34 cell preparations obtained by processing apheresis samples on single-step gradients in a density window of 1.0605 ± 0.0005 g/mL contain not only the majority of the CD34 cells, but also cells that may play a role in overall posttransplant disease progression.