Will CD34+ standardization solve all problems related to cell therapy?

CD34+ selection of hematopoietic blood cell collections and autotransplantation in lymphoma: overnight storage of cells at 4 degrees C does not affect outcome

The purpose of this study was to investigate whether storing mobilized peripheral blood progenitor cell (PBPC) collections overnight before CD34+ selection may delay platelet count recovery after high-dose chemotherapy and CD34+-enriched PBPC re-infusion. Lymphoma patients underwent PBPC mobilization with cyclophosphamide 4 g/m2 i.v. and G-CSF 10 microg/kg/day subcutaneously. Patients were prospectively randomized to have each PBPC collection enriched for CD34+ cells with the CellPro CEPRATE SC System either immediately or after overnight storage at 4 degrees C. Thirty-four patients were randomized to overnight storage and 34 to immediate processing of PBPC; 15 were excluded from analysis due to tumor progression or inadequate CD34+ cell mobilization. PBPC from 23 patients were stored overnight, while 30 subjects underwent immediate CD34+ selection and cryopreservation. Median yield of CD34+ enrichment was 43.6% in the immediate processing group compared to 39.1% in the overnight storage group (P = 0.339). Neutrophil recovery >500 x 10(9)/l occurred a median of 11 days (range 9-16 days) in the overnight storage group compared to 10.5 days (range 9-21 days) in the immediate processing group (P = 0.421). Median day to platelet transfusion independence was 13 (range 7-43) days in the overnight storage group vs 13.5 (range 8-35) days in those assigned to immediate processing (P = 0.933). We conclude that storage of PBPC overnight at 4 degrees C allows pooling of consecutive-day collections resulting in decreased costs and processing time without compromising neutrophil and platelet engraftment after infusion of CD34+-selected progenitor cells. Bone Marrow Transplantation(2000) 25, 559-566.

Toward standardization of CD34+ cell enumeration: an international study. Biomedial Excellence for Safer Transfusion Working Party

BACKGROUND

An international multicenter study, involving six sites in North America and six sites in Europe, was undertaken to assess the performance of standardized methods for the enumeration of CD34+ cells in peripheral blood over the dynamic range from 200 cells per microL to zero. Two commercially available techniques were studied, a flow cytometry method and a microvolume fluorimetry method.

STUDY DESIGN AND METHODS

Coded samples were centrally prepared and sent to test sites by overnight mail. Samples included internal replicates, linear dilutions, and specimens at the lower limit of detection. In addition, commercially available reagent positive control cells were sent to a subset of laboratories.

RESULTS

Over the sample range studied, the intersite precision among different laboratories was good with coefficients of variation ranging from 14 percent to 24 percent for microvolume fluorimetry and from 20 percent to 31 percent for flow cytometry. Intrasite precision ranged from 7 percent to 21 percent. Test linearity was excellent with sites demonstrating a mean r2 = 0.992 for microvolume fluorimetry and r2 = 0.984 for flow cytometry. The lower limit of detection was 5 CD34+ cells per microL for both commercial assays. Over the range of 5 to 50 CD34+ cells per microL, the microvolume fluorimetry assay reported slightly higher values than the flow cytometry assay. Preliminary analysis of reagent positive control cells showed very good precision and accuracy.

CONCLUSIONS

Standardization of CD34+ cells enumeration is improving and commercially available assays provide accurate and precise methods. More investigation of reagent positive control cells is warranted.