Collection of peripheral blood mononuclear cells as a byproduct of plateletpheresis with two different blood cell separators

Quantitation of primitive and lineage-committed progenitors in mobilized peripheral blood for prediction of platelet recovery post autologous transplant

Leukapheresis collections obtained following one of four mobilization regimens from 90 cancer patients were analyzed for their content of various progenitor cell types including erythroid and granulopoietic colony-forming cells in methylcellulose (total CFC), CFC-megakaryocyte (CFC-Mk), CFC detected after 10, 35 and 56 days in long-term culture (LTC), and total CD34+ cells. The number of each of these progenitor cell types collected from individual patients varied over 1000-fold. Nevertheless, within an individual leukapheresis, there was a significant correlation between the number of CD34+ cells and each progenitor type (except day 56 LTC CFC) suggesting that all of them are mobilized by a common mechanism. Patients who had previously received extensive chemotherapy and/or radiotherapy mobilized fewer of all these cell types than those who had not. For the 65 patients who proceeded to autologous transplantation, the median times to an absolute neutrophil count (ANC) of > or =0.5 x 109/l and the last platelet transfusion post transplant were 13 and 11 days, respectively, with 14 (22%) of patients having platelet recovery delayed beyond day 21. There was no significant difference between patients who had or had not received extensive chemo/radiotherapy or among the different mobilization regimens for time to neutrophil or platelet recovery or the number of platelet or red blood cell transfusions received post transplant. Threshold doses of the different cell types transplanted (per kg of patient weight) which predicted rapid platelet recovery were 2 x 106 CD34+ cells, 5 x 105 total CFC and 2.5 x 104CFC-Mk. Corresponding thresholds for progenitor activity measured in LTC could not be established. These results further support the view that standard mobilization regimens yield progenitor numbers that are, in most cases, nonlimiting for generating neutrophil and platelet recoveries within 2 to 3 weeks after myeloablative therapy. Assessment of the CD34+ cell and/or CFC content of leukapheresis collections may identify patients in whom platelet recovery is likely to be significantly delayed although CFC-Mk enumeration does not appear to offer any unique predictive advantage.

Comparison of performance of six different cell separators in collecting peripheral blood mononuclear cells

We compared the efficacy of six different cell separators in collecting peripheral mononuclear cells to be used for autologous or homologous peripheral stem cell transplantation. The product obtained with the Dideco Vivacell cell separator showed a low percentage of mononuclear cells (38%) in the final product and a high platelet efficiency (38%). The Baxter CS3000 Plus cell separator required the longest time to load and prime the kit (18 min), it showed a high MNC efficiency (68%), with the highest percentage of MNC in the final product, the highest platelet efficiency (45%), a low red blood cell contamination in the final product (2.7 mL), the highest extracorporeal volume (450 mL) and a high percentage of technical failures (15%). The product obtained with the Fresenius AS104 cell separator with P1Y kit showed the highest final volume (297 mL), the lowest platelet efficiency (12%) and the lowest extracorporeal volume (230 mL). The same cell separator with C4Y kit showed a lower MNC efficiency (52 vs 60%) and a higher percentage of MNC in final product (63 vs 41%). The platelet contamination in final product was the lowest (18 x 10(9)/100 mL). The Haemonetics MCS3p cell separator required the lowest time to load and prime the kit (5 min), it showed the highest MNC efficiency (71%). The blood volume processed per hour (1328 mL) and the percentage of MNC in final product was lowest (32%), the extracorporeal volume (450 mL) was the highest. The Cobe Spectra cell separator allowed to process the highest blood volume per hour (3383 mL) and the final product had the lowest red blood cell contamination (2.3 mL/100 mL). The Dideco Excel cell separator required the longest time to load and prime the kit (18 min), the lowest MNC efficiency (38%), the highest platelet contamination in final product. Furthermore this machine showed the highest percentage of technical failure (20%). None of the six instruments have all the required preconditions and the ideal cell separator for peripheral stem cell apheresis at present is not available on the market.

A comparison of peripheral blood stem cell apheresis using the Fenwal CS3000 Plus and COBE Spectra

We have compared the leukapheresis products collected on the Fenwal CS3000 Plus and COBE Spectra in a well-controlled patient population. While statistically significant differences were found, i.e. in product hematocrit, volume, number of granulocytes and platelets collected, these are not felt to be physiologically important. Similar efficiency in collecting mononuclear cells and colony forming unit assay results indicate that each instrument is capable of harvesting hematopoietic progenitor cells from peripheral blood.

Autologous peripheral blood progenitor cell transplantation

Harvesting of autologous peripheral blood stem cells (PBSCs) has been facilitated by using currently available, efficient apheresis technology at the time of rebound from chemotherapy while patients are receiving recombinant growth factors, i.e., granulocyte (G) or granulocyte-macrophage (GM) colony stimulating factor (CSF). Ideally pheresis should be done before patients have had extensive stem cell toxins, i.e., alkylating agents or nitrosoureas. This strategy has facilitated the use of high dose chemoradiotherapy given as a single regimen or in a divided dose for patients with solid tumors or hematologic malignancies and results in more rapid engraftment than bone marrow transplantation (BMT). Although there are no assays which measure repopulating stem cells, enumeration of CD34+ cells within PBSCs is a direct and rapid assay which provides an index of both early and late long-term reconstitutive capacity, since it correlates with colony-forming unit (CFU)-GMs, as well as pre-progenitor or delta assays and long-term culture-initiating cells (LTC-IC). A threshold of > or = 2 x 10(6) CD34+ cells/kg recipient body weight has been reported to be required for engraftment, but may vary depending upon the clinical setting. Strategies for mobilization of normal PBSCs also increase tumor cell contamination within PB in the setting of both hematologic malignancies and solid tumors, but the significance of these tumor cells in terms of patient outcome is unclear. Recently isolation of CD34+ cells from PBSCs has been done using magnetic beads or immunoabsorption on columns or rigid plates in order to enrich for normal hematopoietic progenitors and potentially decrease tumor cell contamination. As for other cellular blood components, standards have been developed to assure efficient collection and processing, thawing, and reinfusion, and to maintain optimal PBPC viability. Finally, future directions of clinical research include expansion of hematopoietic progenitor cells ex vivo; use of umbilical cord or placenta as rich sources of progenitor cells; syngeneic hematopoietic stem cell transplantation; related and unrelated allogeneic hematopoietic stem cell transplantation; treatment of infections, i.e., Epstein Barr virus, or tumor relapse after allogeneic BMT using donor PBSC infusions; and gene therapy approaches.