Imprecision of counting CFU-GM colonies and CD34-expressing cells

Ex vivo cultures and drug testing of primary acute myeloid leukemia samples: Current techniques and implications for experimental design and outcome

New treatment options of acute myeloid leukemia (AML) are rapidly emerging. Pre-clinical models such as ex vivo cultures are extensively used towards the development of novel drugs and to study synergistic drug combinations, as well as to discover biomarkers for both drug response and anti-cancer drug resistance. Although these approaches empower efficient investigation of multiple drugs in a multitude of primary AML samples, their translational value and reproducibility are hampered by the lack of standardized methodologies and by culture system-specific behavior of AML cells and chemotherapeutic drugs. Moreover, distinct research questions require specific methods which rely on specific technical knowledge and skills. To address these aspects, we herein review commonly used culture techniques in light of diverse research questions. In addition, culture-dependent effects on drug resistance towards commonly used drugs in the treatment of AML are summarized including several pitfalls that may arise because of culture technique artifacts. The primary aim of the current review is to provide practical guidelines for ex vivo primary AML culture experimental design.

Validation of a semi automatic device to standardize quantification of Colony-Forming Unit (CFU) on hematopoietic stem cell products

Accurate characterization of hematopoietic stem cells (HSC) products is needed to better anticipate the hematopoietic reconstitution and the outcome in patients. Although CD34+ viable cells enumeration is a key predictor of time to correction of aplasia, it does not fully inform about functionality of cells contained in the graft. CFU assay is the gold standard in vitro potency assay to assess clonogenicity of HSC and consists on the count and identification of colonies several days after culture in a semi solid media. Manual count of colonies with optic microscope is the most commonly used method but its important variability and subjectivity hinders the universal implementation of this potency assay. The aim of this study is to validate a standardized method using the STEMvision™ system, the first semi-automated instrument for imaging and scoring hematopoietic colonies, according to French and European recommendations. Results obtained highlight better performance criteria with STEMvision™ system than the manual method. This semi-automatic device tends to reduce the coefficients of variation of repeatability, inter-operator variability and intermediate precision. This newly available platform could represent an interesting option, significantly improving performances of CFU assays used for the characterization of hematopoietic progenitors.

Quantification of nucleated cells, CD34-positive cells and CFU-GM colonies in single bone marrow samples and bone marrow harvests derived from healthy children

Little is known regarding bone marrow (BM) cellularity, CD34+ fraction, and CFU-GM colony formation in relation to age and whether healthy children require a reference range distinct from healthy adults. We therefore analyzed a series of single BM aspirates from 45 healthy children who were evaluated as potential BM donors. Thirty-three of these children subsequently donated BM. We quantified the nucleated cell count, fraction of CD34+ cells, and number of CFU-GM colonies in single aspirates and BM harvests. Single aspirates displayed a mean nucleated cell count of 31.3 × 10(6) cells/mL, a mean fraction of 1.17% CD34+ cells, and a mean colony forming potential of 66.6 CFU-GM/10(5) cells. Harvests yielded the same number of nucleated cells but increased numbers of CD34+ cells and CFU-GM compared with single aspirates. The mean nucleated cell count in BM harvests was 31.1 × 10(6) /mL with a mean fraction of 1.95% CD34+ cells and a mean of 112.4 CFU-GM colonies/10(5) cells. The concentration of nucleated cells was elevated compared with reported adult counts, while CD34+ percentage and CFU-GM counts were similar. In this series of healthy children, the fraction of CD34+ cells, CFU-GM colonies, and nucleated cells decreased with age. We did not identify gender specific differences. To our knowledge, this represents the first comprehensive study of CD34+ cell fraction, CFU-GM counts, and nucleated cell numbers in the BM of healthy children. The findings provide valuable information for practical use for BM transplantation and contribute to the understanding of hematopoiesis from birth to adulthood.

Current practices and prospects for standardization of the hematopoietic colony-forming unit assay: a report by the cellular therapy team of the Biomedical Excellence for Safer Transfusion (BEST) Collaborative

BACKGROUND AIMS

Wide acceptance of the colony-forming unit (CFU) assay as a reliable potency test for stem cell products is hindered by poor inter-laboratory reproducibility. The goal of this study was to ascertain current laboratory practices for performing the CFU assay with an eye towards identifying practices that could be standardized to improve overall reproducibility.

METHODS

A survey to evaluate current laboratory practices for performing CFU assays was designed and internationally distributed.

RESULTS

There were 105 respondents to the survey, of whom 68% performed CFU assays. Most survey recipients specified that an automated rather than a manual cell count was performed on pre-diluted aliquots of stem cell products. Viability testing methods employed various stains, and when multiple sites used the same viability stain, the methods differed. Cell phenotype used to prepare working cell suspensions for inoculating the CFU assay differed among sites. Most respondents scored CFU assays at 14-16 days of incubation, but culture plates were read with various microscopes. Of 57 respondents, 42% had not performed a validation study or established assay linearity. Only 63% of laboratories had criteria for determining if a plate was overgrown with colonies.

CONCLUSIONS

Survey results revealed inconsistent inter-laboratory practices for performing the CFU assay. The relatively low number of centers with validated CFU assays raises concerns about assay accuracy and emphasizes a need to establish central standards. The survey results shed light on numerous steps of the methodology that could be targeted for standardization across laboratories.

Use of hematopoietic progenitor cell count on the Sysmex XE-2100 for peripheral blood stem cell harvest monitoring

Successful peripheral blood stem cell (PBSC) collection depends on the timing of apheresis based on CD34+ cell enumeration. Because this analysis is expensive and induces organization difficulties, we evaluated hematopoietic progenitor cell (HPC) quantification on the Sysmex XE-2100 as a surrogate analysis. We tested 157 blood samples for CD34+ cells and HPC counts. We found a good linear correlation between HPC and CD34+ and determined simple rules allowing to use HPC count in daily practice. We set a positive cut-off >30 HPC/mm(3) for allowing PBSC harvest and a negative cut-off at 0 HPC/mm(3) for which collection should be delayed. These two situations accounted for 62% of cases and CD34+ cell count by flow cytometry confirmed HPC result in 95% of cases. Between 0 and 30 HPC/mm3, CD34+ enumeration is required for decision-making. We conclude that HPC count may be a useful surrogate for CD34+ enumeration in PBSC harvest monitoring.

A new automated cell washer device for thawed cord blood units

BACKGROUND

The current available techniques to wash out DMSO from thawed umbilical cord blood (UCB) units are based essentially on standard centrifugation in an open system with various degrees of cell loss.

STUDY DESIGN AND METHODS

We evaluated the capacity of a new automated closed device (Cytomate, Baxter, IL) to wash out the DMSO from thawed UCB units, saving at the same time the progenitor and accessory cells in terms of CD34+ cells and MNCs. We modified the standard software of the device and calculated the cell recovery on 25 UCB units. Moreover, we set up a new gas chromatographic method to exactly detect the DMSO removal rate.

RESULTS

To evaluate the efficiency of the Cytomate device, we considered the postthawing (prewashing) versus postwashing cell recovery. The average recovery (%) in terms of total nucleated cells was 63.30 (range, 40.12-89.00), CD34+ cells was 70.20 (range, 11.51-89.01), CD3+ cells was 61.01 (range, 28.80-87.08), CD4+ cells was 62.53 (range, 30.62-96.73), CD8+ cells was 57.4 (range, 26.87-94.72), CD19+ cells was 63.33 (range, 39.10-90.33), CD16+/56+ cells was 70.67 (range, 8.91-98.40), CFU-GM was 74.33 (range, 20.23-98.60), total CFUs was 82.34 (range, 14.83-247.12), and viability was 89.67(range, 70.74-98.30). The total working time required was, on average, 15 minutes (range, 7-20).

CONCLUSIONS

The Cytomate device demonstrated a satisfying efficiency in cell recovery and in maintaining the clonogenic power of the UCB graft. The removal rate of DMSO was practically complete with evident advantages for the recipient. Finally, the entire manipulation performed in a closed system revealed to be safe, maintaining the sterility of the graft.

Cord blood processing with an automated and functionally closed system

BACKGROUND

Umbilical cord blood processing with standard centrifugation techniques is performed in open systems and results in varying cell and volume recoveries.

STUDY DESIGN AND METHODS

Forty umbilical cord blood donations were randomly assigned to processing either with a microprocessor-controlled cell separator equipped with closed disposables or with a manual separation procedure in blood bags. The collection efficiency of nucleated cells, MNCs, RBCs, and CD34+ cells and the processing time were analyzed.

RESULTS

Using the cell processor, mean collection efficiencies were 78.6 +/- 24.9 percent for nucleated cells, 77.4 +/- 27.8 percent for MNCs, 55.5 +/- 14.6 percent for RBCs, and 83.6 +/- 32.5 percent for CD34+ cells, while they were 73.1 +/- 13.2 percent for nucleated cells, 78.1 +/- 14.9 percent for MNCs, 26.0 +/- 12.2 percent for RBCs, and 77.0 +/- 17.6 percent for CD34+ cells when using the standard centrifugation technique. The processing time was about 20 minutes for automated processing and 60 to 80 minutes for the standard centrifugation technique.

CONCLUSION

Using the new cell processor, the collection efficiencies for nucleated cells, MNCs, and CD34+ cells are similar to those obtained by established centrifugation techniques while the RBC reduction is less effective. The main advantages of the new systems are the closed system, the more standardized processing procedure, and a significantly shorter processing time.

Flow cytometric CD34+ determination in stem cell transplantation: before or after cryopreservation of grafts?

Various attempts have been made to standardize and improve the reproducibility of flow cytometric determination of CD34+ hematopoietic progenitor cells. It is still not clear, however, whether the quantification of CD34+ cells in a stem cell graft should be done before or after cryopreservation. To address this issue, we investigated 78 unselected and 32 immunomagnetically selected autologous and allogeneic leukapheresis products (LA) before and after cryopreservation using pilot vials. Cell numbers were quantified within a Neubauer chamber, and CD34+ content was determined by flow cytometry; propidium iodide staining was used to exclude dead cells from analysis. Before freezing, the mean viable CD34 cell content in the unselected samples was 1.22% and increased after thawing to a mean of 2.16% of viable cells. Taking into account cell loss and cell death, the overall recovery of viable cells was 64.5%; all CD34+ cells could be recovered. Mean purity in the CD34-selected cell fraction was 85% (48-97) before and 91.3% (67-99) after thawing. The number of viable cells was 86.8% before and 86.1% after freezing with a 93.9% recovery of total cells. This leads to a mean 93.7% (SD +/- 23.1) recovery of viable cells and 100% (SD +/- 22.3) recovery of viable CD34+ cells. There was no significant difference in tolerance to freeze/thaw stress between cells from heavily pretreated autologous patients and healthy allogeneic donors. Our data show that freezing significantly increases the percentage of CD34(+) cells in unmanipulated LA, probably due to the death of granulocytes and mononuclear cells (MNCs). Nevertheless, the overall number of viable CD34+ cells in unselected as well as selected samples remains unchanged. Thus, CD34 data from different laboratories, for example, within multicenter trials, should be comparable independent of the different time points of acquisition.

A single-step colony-forming unit assay for unseparated mobilized peripheral blood, cord blood, and bone marrow

The colony-forming unit (CFU) assay is exposed to a lot of variation, part of which is introduced by several enrichment strategies that are routinely performed before assessment of clonogenic capacity in mobilized peripheral blood (PB), bone marrow (BM), or cord blood (CB). We investigated the possibility to perform a single-step CFU assay by direct plating of PB, BM, or CB into CFU culture medium to obtain more reproducible results than after a standard Ficoll or lysis procedure. Direct plating implies the presence of red blood cells (RBC), white blood cells (WBC), and plasma in the CFU assay, which could possibly influence the outcome of the assay. Of all components, only the RBC was found to negatively influence CFU-GM growth if a concentration of > 0.02 x 10(9)/ml was present in the CFU culture medium. Subsequently, depending on the RBC concentration PB, BM, and CB samples were prediluted in triplicate or quadruplicate and plated into CFU medium. Lysis and/or Ficoll procedures were also performed in triplicate or quadruplicate on the same samples, and the mean colony number and coefficient of variation (CV) of the three techniques were compared. Significantly smaller CV values were found using the direct plating technique (all assays, mean 7.5%, range 1.6-15.6%) than after Ficoll separation (mean 18.0%, range 2.2-62.5%). Intermediate results were obtained with the lysis method (mean CV 11.6%, range 3.3-29%). In most samples, and especially in those with a very low number of clonogenic cells per milliliter, more colonies were detected with the direct plating method than with either the lysis or Ficoll method. In conclusion, the single-step direct plating method significantly enhances reproducibility of the CFU assay for PB, BM, and CB samples in comparison with standard techniques by circumvention of loss of colony formation and by decreasing variability. Furthermore, the direct plating technique is a timesaving assay.

Improvement of the precision in CFU-GM and BFU-E counting by flow cytometry-based standardization of short-term culture assays

The counting of colony-forming units granulocyte-macrophage (CFU-GM) and burst-forming units erythrocyte (BFU-E) provides substantial in vitro information about the graft quality after peripheral stem cell transplantation (PBSCT). By using different techniques for culturing and scoring, high inter- and intralaboratory coefficients of variation (CV) are frequently reported. We minimized the imprecision by using flow cytometry-based incorporation of constant numbers of CD34(+) cells per culture dish instead of the formerly used mononuclear cells. Our results show acceptable CVs for CFU-GM (12.3%) and for BFU-E (13.3%) based on this seeding technique, which contributes to fulfilling the demands of a quality assurance system in stem cell laboratories.

Trafficking of CD34+ cells into the peripheral circulation during collection of peripheral blood stem cells by apheresis

The number of CD34+ cells collected during apheresis is related to the volume of blood processed. In large-volume apheresis (LVL) procedure, more cells can be collected than were originally present in the peripheral blood at the start of the collection procedure. We prospectively studied the levels of CD34+ cells in the blood and apheresis product during LVL procedures for 21 patients with acute myelogenous leukemia or multiple myeloma. These patients experienced a slow decline in blood CD34+ cell concentrations during the apheresis procedure. No patient demonstrated a sustained rise in CD34+ cell counts as a result of the procedure. The number of CD34+ cells collected exceeded the number calculated to be in the peripheral blood at the start of the procedure by an average of 3.0-fold. The efficiency of collection for CD34+ cells averaged 92.6% and did not vary with speed of blood processing, diagnosis, or mobilization regimen. The calculated release of CD34+ cells from other reservoirs into the peripheral blood averaged 3.71 x 10(6)/min (range, 0.36-13.7 x 10(6)/min), and correlated (r = 0.82) with the concentration of these cells in the peripheral blood at the start of the procedure. These data show that the apheresis procedure used in this study does not affect the release of CD34+ cells in a cytokine-treated patient. LVL will result in collection of larger quantities of CD34+ cells than procedures involving processing of smaller volumes of blood, but the number of cells collected is limited by the rate of release of these cells into the peripheral circulation where they are accessible for collection.

Determination of peripheral blood stem cells by the Sysmex SE-9500

The Sysmex SE-9500 automated haematology analyser provides an estimate of immature cells, referred to as 'haematopoietic progenitor cells' (HPC). The aim of this study was to evaluate the reliability and usefulness of the SE-9500 HPC parameter as compared with the CD34 + cell count and to determine whether the HPC count was of value in predicting the optimal harvesting time for peripheral blood stem cells (PBSC). Studies were performed on 112 samples from 21 patients with haematological malignancies and 13 healthy donors undergoing progenitor cell mobilisation. Coefficients of variation for the HPC count were 30%, 23.8%, 12.4% and 8.3% respectively for samples with low (4 x 106/l), medium (13 x 106/l), high (250 x 106/l) and very high (2413 x 106/l) counts. There was good linearity for HPC measurement in both peripheral blood (PB) and purified CD34 + cell suspensions (r > 0.995), and no detectable carryover was observed. There was an acceptable correlation between HPC and CD34 + cell counts for PB samples (r=0.669) and for CD34 + cell suspensions (r=0.859). Analysis of purified CD34 + cells using the SE-9500 HPC mode revealed that they appear both in the blast cell area and the immature granulocyte area of the analyser cell display. Quantitation of CD34 + cells and HPC during PBSC mobilisation showed good agreement between these parameters with regard to the optimal time for PBSC harvesting. These findings suggest that HPC counting with the Sysmex SE-9500 may be clinically useful for optimising the timing of PBSC collection.

A European reference protocol for quality assessment and clinical validation of autologous haematopoietic blood progenitor and stem cell grafts

Recently, the regulatory authorities have begun to show interest in haematopoietic stem cell products. On a professional rather than a regulatory basis, the International Society for Hematotherapy and Graft Engineering (ISHAGE) has established the Foundation for the Accreditation of Haematopoietic Cell Therapy (FACHT), which has drawn up guidelines for standards and accreditation of such activity. In Europe, the regulatory environment with regard to haematopoietic stem cell grafts, processing and storage are currently less stringent. However, in 1998 the European Joint Accreditation Committee Euro-ISHAGE/EBMT (JACIE) prepared a regulatory document 'Standards for Blood and Marrow Progenitor Cell Collection, Processing and Transplantation' which was approved by the EBMT General Assembly. The major objectives were to promote quality of medical and laboratory practice in haematopoietic progenitor cell transplantation. The standards extend and detail the pre-existing activity of EBMT centres including all phases of collection, processing and administration of these cells. This is the platform for the proposed reference protocol for CD34(+) cell enumeration and clinical validation of quality assessment to ensure that appropriate standards of work and product quality are established and will be maintained.

Technical aspects and clinical impact of hematopoietic progenitor subset quantification

As high-dose therapy for malignancies is now being applied to newly diagnosed patients as adjuvant therapy, it has become a requirement that quality and safety assessment of hematopoietic stem cell grafts be evidence-based. This process has developed a new institution in medicine, the stem cell laboratory. In most cases this speciality has evolved from or within hematological research laboratories. However, the increased routine technologies applied in quality evaluation, ex vivo manipulation and safety assessment in stem cell handling naturally places this activity in transfusion medicine. Multiparametric flow cytometry can identify progenitor subsets in normal human bone marrow and peripheral blood, and such subset quantification has been used retrospectively to predict three-lineage engraftment following high-dose therapy for malignancies. Published single center data have suggested an impact on clinical outcome, and a standardized technique for subset enumeration needs to be established before prospective multicenter trials can be initiated to document the prognostic value of such quality assessment in autografting. Based on experiences of CD34 enumeration, which we consider to be the first step in quality assessment of hematopoietic stem cell grafts, this review discusses flow cytometry subset identification by lineage-specific differentiation markers, stromal-dependent adherence molecules, and regulatory growth factor receptors from a technical point of view. The aim of this review is:To recommend a simple method based on the experiences of the Nordic workshop III on subset identification; To present new molecular genetic-based methods for future use in quality assessment; and To propose new endpoints necessary for validation of the likely clinical impact of subsets in prospective trials. As sample differences between blood and marrow result in technical difficulties, this review only focuses on the methodology of identifying subsets in blood and leukapheresis products. Methods for subset analysis in diagnostic bone marrow samples will be covered in a forthcoming review.

Circulating CD4+ T lymphocytes with intracellular but no surface CD3 antigen in five of seven patients consecutively diagnosed with angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) accounts for less than 1% of all lymphatic malignancies. Oligoclonality or monoclonality for any of the T-cell receptor (TCR) chain genes can be demonstrated in the majority of the cases. During systematic screening for the presence of circulating lymphocytes with atypical coexpression of differentiation antigens in patients with T-cell lymphomas, we have discovered a minor population (accounting for 0.2% to 10.% of all lymphocytes) of atypical lymphocytes in the blood of five of seven patients consecutively diagnosed in 1997/1998 by lymph node histology to have AITL. The major distinguishing feature of these cells consists of the lack of the surface expression of the CD3 antigen, but not of the intracellular expression. These cells express the T-cell antigens CD2 and CD5 on their surface, but not CD7, and they express CD4 and CD45 at numbers of molecules per cell typical for T lymphocytes. Gene scan analyses for the TCR gamma chain revealed oligoclonality of these flow-sorted cells in one patient and monoclonality in two patients, the same patterns of TCR gamma chain gene as determined processing the respective diagnostic lymph nodes. Circulating CD4-expressing T lymphocytes with exclusively cytoplasmic expression of CD3 appear to represent the malignant population in patients with histologically diagnosed AITL.

Use of the haemopoietic progenitor cell count of the Sysmex SE-9500 to refine apheresis timing of peripheral blood stem cells

The Sysmex SE-9500 automated cell counter provides an estimate of immature cells referred to as 'haemopoietic progenitor cells' (HPC). The aim of this study was to relate the HPC count to CD34+ cell levels in mobilized peripheral blood and to determine whether the HPC count was valuable in predicting apheresis yields of CD34+ cells. Studies were performed on 114 samples from 67 patients undergoing progenitor cell mobilization. HPC cells were undetectable in the steady state. On the day of apheresis the HPC and CD34 counts were weakly correlated, with the median HPC count being 2.3-fold greater than the CD34+ cell count. The HPC count did not include the CD34+ cells as immunomagnetic depletion of CD34+ cells did not significantly reduce the HPC count. CD34+ cell counts predicted for apheresis yield (r = 0.773) on that day as did the HPC count (r = 0. 623). The optimal strategy to prevent unnecessary harvesting while minimizing the risk of missing an adequate harvest, and minimizing laboratory investigations, was to screen all samples for HPC and limit CD34+ cell measurements to those with an HPC count <10 x 106/l (19/114 samples). If the CD34+ cell count was also <10 x 106/l then harvesting should not be carried out.

Content of long-term culture-initiating cells, clonogenic progenitors and CD34 cells in apheresis harvests of normal donors for allogeneic transplantation, and in patients with acute myeloid leukaemia or multiple myeloma

Using a limiting dilution assay the frequency of long-term culture-initiating cells (LTC-IC) in the apheresis products following mobilization by granulocyte-colony stimulating factor (G-CSP) with or without chemotherapy from 14 normal donors (ND) for allogeneic bone marrow transplantation, 16 patients with multiple myeloma (MM) and 15 patients with acute myeloid leukaemia (AML), where the aphereses were intended for autologous transplantation, were compared. The estimated median incidences of LTC-IC in the first apheresis products from ND, MM and AML were 1/3289, 1/1775 and 1/13075 mononuclear cells (MNC) respectively. The patients with AML had a significantly lower incidence compared with the other two groups (P < 0.0001). There was a positive correlation between the incidence of LTC-IC and the number of CD34+ cells, the number of GM-CFC, and the number of BFU-E. The positive association with GM-CFC or BFU-E was weaker. In these experiments the percentage of CD34+ cells was the best predictor for the frequency of LTC-IC in the peripheral blood progenitor cells (PBPC). In eight cases of MM the LTC-IC assay was performed for both the first and second harvest. All cases had a lower LTC-IC frequency in the second harvest compared with the first, an average of 23% (13-42%, 95% confidence interval) and this reduction was statistically significant (P<0 001); CD34+ cells were also lower (P< 0.001).

Quality assurance of CFU-GM assays: inter-laboratory variation despite standard reagents

To investigate the hypothesis that commercial kits for CFU-GM (colony forming unit granulocyte-macrophage) assay will reduce the interlaboratory variation noted by many workers, we carried out a quality assurance exercise in 2 parts. There were 8 participants in the first study and each performed CFU-GM assays using their in-house method and a commercial kit (Stem Cell CFU Kit, Gibco) in parallel. In the second exercise there were 10 participants and each performed CFU-GM with in-house methods and with a different commercial medium (Methocult GF H4534, Stem Cell Technologies). Twelve samples of cryopreserved peripheral blood progenitor cells (PBPC) were analysed by each participant in each part of the study. A very wide range of results was found for the different in-house methods, but standardizing the clonogenic assay with the commercial kits did not reduce the variation seen. To improve the reproducibility of CFU-GM assays between laboratories, scrupulous attention should be paid to all the steps involved in the assays, as little progress will be made by using commercial medium in isolation from efforts to reduce other sources of variation.

CD34+ subset and tumor cell quantitation by flow cytometry--step toward quality assessment of autografts in B cell malignancies

To day it is possible to predict the probability of fast engraftment based on a very simple flow cytometry standard analysis of CD34+ cells as documented by the 28 laboratories within the NSCL-G. However, the risk for delayed platelet engraftment still needs to be predicted in clinical practice for patients receiving less than 10 x 10(6) CD34+ cells/kg. Here we present data from our center supporting that identification by double staining of uncommitted (CD34+/CD38-) and lineage specific (CD34+/CD61+) progenitors may allow us to predict patients at high risk for prolonged platelet recovery. Following high dose therapy more than 30% of patients with haematological malignancies do suffer from disease recurrence within the first 3-6 months following high dose therapy. Today there are strong indications that such patients may have been transplanted with an autograft contaminated with a high number of potentially malignant B cells. Here we present a novel methodology for quantitation of blood circulating tumor cells by combining flow cytometry, cell sorting, limiting dilution and single cell RT-PCR. Such methodology has documented mobilization of clonal B cells following priming of the peripheral blood stem cell harvest and it can be used to identify minor populations and predict the efficacy of patient specific purging strategy. Consequently, quality assessment of autografts may include techniques which can predict fast three lineage engraftment as well as the risk for prolonged platelet recovery and can identify the group of patients/autografts with a strong contamination of potential tumor cells with a risk of early relapse. The future supportive cell therapy may depend upon improvements of such technologies and strategies including the selective administration of lineage specific growth factors e.g., trombopoietin as well as patient specific controlled purging strategies.

Analysis of CD34-expressing cells in clinical practice

The flow cytometric determination of haemopoietic cells defined as CD34-expressing cells has greatly added to the improvement of the management of harvesting circulating haemopoietic cells for subsequent autologous reinfusion in the setting of high-dose chemo/(radio)-therapy. Additionally, this flow cytometric determination has replaced, in some institutions, the in-vitro culture test for CFU-GM as the measure to estimate the haemopoietic potential of the cells to be reinfused/transplanted.

High CD34+ Cell Counts Decrease Hematologic Toxicity of Autologous Peripheral Blood Progenitor Cell Transplantation

Optimal numbers of CD34+ cells to be reinfused in patients undergoing peripheral blood progenitor cell (PBPC) transplantation after high-dose chemotherapy are still unknown. Hematologic reconstitution of 168 transplantations performed in patients with lymphoproliferative diseases was analyzed according to the number of CD34+ cells reinfused. The number of days from PBPC reinfusion until neutrophil recovery (>1.0 × 109/L) and unsustained platelet recovery (>50 × 109/L) were analyzed in three groups defined by the number of CD34+ cells reinfused: a low group with less than or equal to 2.5 × 106 CD34+ cells/kg, a high group with greater than 15 × 106 CD34+cells/kg, and an intermediate group to which the former two groups were compared. The 22 low-group patients had a significantly delayed neutrophil (P < .0001) and platelet recovery (P < .0001). The 41 high-group patients experienced significantly shorter engraftment compared with the intermediate group with a median of 11 (range, 8 to 16) versus 12 (range, 7 to 17) days for neutrophil recovery (P = .003), and a median of 11 (range, 7 to 24) versus 14 (range, 8 to 180+) days for platelet recovery (P< .0001). These patients required significantly less platelet transfusions (P = .002). In a multivariate analysis, the amount of CD34+ cells reinfused was the only variable showing significance for neutrophil and platelet recovery. High-group patients had a shorter hospital stay (P = .01) and tended to need fewer days of antibotic administration (P = .12). In conclusion, these results suggest that reinfusion of greater than 15 × 106 CD34+ cells/kg after high-dose chemotherapy for lymphoproliferative diseases further shortens hematopoietic reconstitution, reduces platelet requirements, and may improve patients' quality of life.

High CD34+ Cell Counts Decrease Hematologic Toxicity of Autologous Peripheral Blood Progenitor Cell Transplantation

Optimal numbers of CD34+ cells to be reinfused in patients undergoing peripheral blood progenitor cell (PBPC) transplantation after high-dose chemotherapy are still unknown. Hematologic reconstitution of 168 transplantations performed in patients with lymphoproliferative diseases was analyzed according to the number of CD34+ cells reinfused. The number of days from PBPC reinfusion until neutrophil recovery (>1.0 × 109/L) and unsustained platelet recovery (>50 × 109/L) were analyzed in three groups defined by the number of CD34+ cells reinfused: a low group with less than or equal to 2.5 × 106 CD34+ cells/kg, a high group with greater than 15 × 106 CD34+cells/kg, and an intermediate group to which the former two groups were compared. The 22 low-group patients had a significantly delayed neutrophil (P < .0001) and platelet recovery (P < .0001). The 41 high-group patients experienced significantly shorter engraftment compared with the intermediate group with a median of 11 (range, 8 to 16) versus 12 (range, 7 to 17) days for neutrophil recovery (P = .003), and a median of 11 (range, 7 to 24) versus 14 (range, 8 to 180+) days for platelet recovery (P< .0001). These patients required significantly less platelet transfusions (P = .002). In a multivariate analysis, the amount of CD34+ cells reinfused was the only variable showing significance for neutrophil and platelet recovery. High-group patients had a shorter hospital stay (P = .01) and tended to need fewer days of antibotic administration (P = .12). In conclusion, these results suggest that reinfusion of greater than 15 × 106 CD34+ cells/kg after high-dose chemotherapy for lymphoproliferative diseases further shortens hematopoietic reconstitution, reduces platelet requirements, and may improve patients' quality of life.

Quality Assurance in Ex Vivo Progenitor Cell Manipulation

Over the past few years, hemopoietic transplant has evolved from an investigational phase to routine therapy, thus becoming a potentially curative strategy for a large variety of diseases. Several transplant situations are still outstanding and the need for ex vivo graft manipulation for different transplantation products is growing. To obtain an ideal graft, many different methods, even sophisticated manipulations, may be required. Since transplantation products play an important role in disease outcome, the assessment of graft quality to ensure standard compliance is needed. The development of a regulatory approach to these new manipulated hematopoietic products is very complex and should come under current Good Manufacturing Practices (cGMPs). Manufacturing approach to these new blood products must be urgently introduced to accounting Quality System in Transfusion Medicine. The best way to develop compliance with standards, in agreement with internationally accepted criteria, is, likely, an accreditation system in transplantation programs.