Mobilized peripheral blood stem cells (PBSC) were collected in autologous plasma and acid-citrate-dextrose formula A (ACD-A) by leukaphereses using the CS3000 cell separator (Baxter) and stored at 4 degrees C in a refrigerator for 8 days. We have looked at the viability of the nucleated cells with the trypan blue test and the proliferation and differentiation capacity using a standardized progenitor cell cloning assay. The changes in viability, granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst-forming units (BFU-E), and mixed-lineage colony-forming units (CFU-GEMM) were determined daily during the storage period. Viability was 90.8% (SD 8%) at day 0 and declined to a mean of 69.5% (SD 15.5%) at day 8. CFU-GM decreased to 47% (SD 28.7%), CFU-GEMM to 48% (SD 42.2%), and BFU-E to 40.1% (SD 18.4%) after 6 days. After 5 days of storage the mean viability was 79.7% (SD 17.8%), whereas the mean CFU-GM were 65.3% (SD 28.4%) the mean CFU-GEMM were 61.8% (SD 30.4%) and the mean BFU-E were 55.1% (SD 18.2%). At day 4 viability was still 82.5% (SD 17.0%), recovery of CFU-GM was 78.5% (SD 28.8%), recovery of CFU-GEMM was 70.7% (SD 40.4%) and recovery of BFU-E was 65.0% (SD 17.5%). These data show, that PBSC can be stored safely over at least 5 days at 4 degrees C while the patient receives high-dose chemotherapy. ablative radiochemotherapy. Increasing experience shows that PBSC autografting leads to more rapid neutrophil and platelet recovery after high-dose chemotherapy as compared with autologous bone marrow transplantation [8, 26]. PBSC transplantation needs no general anesthesia and is a successful technique for patients with a hypocellular bone marrow [13]. After mobilization with chemotherapy and recombinant human granulocyte (rhG-CSF) or granulocyte-macrophage colony-stimulating factor (rhGM-CSF), peripheral blood stem cells can be collected in large quantities by only a small number of continuous-flow leukaphereses [4-7, 17, 19, 20, 24, 25]. The storage of stem cells by cryopreservation techniques requires extensive equipment and is labor intensive, time consuming, and expensive. It is therefore of interest to prove the possibility of noncryopreservation storage of PBSC as an alternative method. Experiences with noncryopreservative liquid storage of bone marrow have shown a sufficient stem cell survival, as determined by granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst-forming units (BFU-E), and mixed-lineage colony-formming units (CFU-GEMM) after storage at 4 degrees C for 3 days, and still a certain recovery of progenitor cells after 7 days [14, 16]. We stored PBSC after mobilization and harvest by apheresis in small plastic tubes over a period of 8 days in a refrigerator at 4 degrees C and examined the change of viability daily in in vitro studies using the trypan-blue dye exclusion test and the change of proliferation and differentiation capacity with a standardized cell-cloning assay for detecting CFU-GM, BFU-E, and CFU-GEMM.
