Quantification of CD34+ cells: comparison of methods

Peripheral Blood Stem Cell Harvest HPC Count Is an Effective Surrogate Marker for CD34+ Cell Count in Allogeneic Stem Cell Transplant Setting

OBJECTIVE: We assessed the predictive potential of XN-HPC for CD34+ cell count as obtained through Sysmex automated hematology analyzers (XN-1000). METHODS: This study was conducted at the National Institute of Blood Diseases and Bone Marrow Transplantation in 84 donors between December 2012 and December 2017 in the first phase and later validated in 112 donors between December 2017 and December 2018. Sysmex XN-1000 and BD FACS Calibur estimated XN-HPC and CD34+ cells of peripheral blood apheresis product, respectively. Spearman's correlation was assessed between XN-HPC and CD34+ cell count followed by receiver operating characteristic curve calculation to determine the XN-HPC cutoff for a CD34+ count of ≥2 million cells/kg of recipient's body weight RESULTS: There is a moderately positive correlation (P value = .003) between XN-HPC and CD34+ count. Receiver operating characteristic curve analyses demonstrated that a cutoff value for XN-HPC of ≥1·845×10⁶cells/kg of recipient's body weight has a specificity and sensitivity of 100% and 78·2%, respectively, for predicting the CD34+ count of ≥2 million cells/kg of recipient's body weight. This cutoff value of XN-HPC was prospectively validated in 112 donors. The positive predictive value was found to be 100%, while negative predictive value was 17%. CONCLUSION: XN-HPC has a highly promising potential to serve as a cost-effective and time-saving surrogate for CD34+ cell count.

Circulating adult stem and progenitor cell numbers-can results be trusted?

BACKGROUND

Within the last years, the interest in physical exercise as non-invasive stimulus influencing circulating hematopoietic stem and progenitor cell (CPC) concentrations has constantly grown. Cell estimates are often derived by determining the subgroup of CPC as percent lymphocytes (LYM) or mononuclear cells (MNC) via flow cytometry and back calculation over whole blood (WB) cell counts. However, results might depend on the used cell isolation technique and/or gating strategy. We aimed to investigate MNC loss and apoptosis during the flow cytometry sample preparation process preceded by either density gradient centrifugation (DGC) or red blood cell lysis (RBCL) and the potential difference between results derived from back calculation at different stages of cell isolation and from WB.

METHODS

Human blood was subjected to DGC and RBCL. Samples were stained for flow cytometry analysis of CPC (CD34+/CD45dim) and apoptosis analysis (Annexin V) of MNC and CPC subsets. MNC and LYM gating strategies were compared.

RESULTS

Both DGC as well as RBCL yielded comparable CPC concentrations independent of the gating strategy when back calculated over WB values. However, cell loss and apoptosis differed between techniques, where after DGC LYM, and monocyte (MONO) concentrations significantly decreased (p < 0.01 and p < 0.05, respectively), while after RBCL LYM concentrations significantly decreased (p < 0.05) and MONO concentrations increased (p < 0.001). LYM apoptosis was comparable between techniques, but MONO apoptosis was higher after DGC than RBCL (p < 0.001).

CONCLUSIONS

Investigated MNC counts (LYM/MONO ratio) after cell isolation and staining did not always mimic WB conditions. Thus, final CPC results should be corrected accordingly, especially when reporting live CPC concentrations after DGC; otherwise, the CPC regenerative potential in circulation could be biased. This is of high importance in the context of non-invasively induced CPC mobilization such as by acute physical exercise, since these cell changes are small and conclusions drawn from published results might affect further applications of physical exercise as non-invasive therapy.

Naja sputatrix Venom Preconditioning Attenuates Neuroinflammation in a Rat Model of Surgical Brain Injury via PLA2/5-LOX/LTB4 Cascade Activation

Inflammatory preconditioning is a mechanism in which exposure to small doses of inflammatory stimuli prepares the body against future massive insult by activating endogenous protective responses. Phospholipase A2/5-lipoxygenase/leukotriene-B4 (PLA2/5-LOX/LTB4) axis is an important inflammatory signaling pathway. Naja sputatrix (Malayan spitting cobra) venom contains 15% secretory PLA2 of its dry weight. We investigated if Naja sputatrix venom preconditioning (VPC) reduces surgical brain injury (SBI)-induced neuroinflammation via activating PLA2/5-LOX/LTB4 cascade using a partial frontal lobe resection SBI rat model. Naja sputatrix venom sublethal dose was injected subcutaneously for 3 consecutive days prior to SBI. We observed that VPC reduced brain edema and improved neurological function 24 h and 72 h after SBI. The expression of pro-inflammatory mediators in peri-resection brain tissue was reduced with VPC. Administration of Manoalide, a PLA2 inhibitor or Zileuton, a 5-LOX inhibitor with VPC reversed the protective effects of VPC against neuroinflammation. The current VPC regime induced local skin inflammatory reaction limited to subcutaneous injection site and elicited no other toxic effects. Our findings suggest that VPC reduces neuroinflammation and improves outcomes after SBI by activating PLA2/5-LOX/LTB4 cascade. VPC may be beneficial to reduce post-operative neuroinflammatory complications after brain surgeries.

Peripheral blood late mixed chimerism in leucocyte subpopulations following allogeneic stem cell transplantation for childhood malignancies: does it matter?

The impact of persistent mixed chimerism (MC) after haematopoietic stem cell transplantation (HSCT) remains unclarified. We investigated the incidence of MC in peripheral blood beyond day +50 after HSCT and its impact on rejection, chronic graft-versus-host disease (c-GvHD) and relapse in 161 children receiving allogeneic HSCT for haematological malignancies. The 1-year incidence of late MC was 26%. Spontaneous conversion to complete donor chimerism (CC) occurred in 43% of patients as compared to 62% after donor lymphocyte infusions. No graft rejection occurred. The 1-year incidence of c-GvHD was 20 ± 7% for MC, and 18 ± 4% for CC patients (P = 0·734). The 3-year cumulative incidence of relapse (CIR) according to chimerism status at days +50 and +100 was 22 ± 4% for CC patients vs. 22 ± 8% for MC patients (day +50; P = 0·935) and 21 ± 4% vs. 20 ± 7% (day +100; P = 0·907). Three-year CIRs in patients with persistent MC and patients with CC/limited MC were comparable (8 ± 7% vs. 19 ± 4%; P = 0·960). HSCT for acute leukaemia or myelodysplastic syndrome as secondary malignancies (hazard ratio (HR) 4·7; P = 0·008), for AML (HR 3·0; P = 0·02) and from mismatched donors (HR 3·1; P = 0·03) were independent factors associated with relapse. Our data suggest that late MC neither protects from c-GvHD nor does it reliably predict impending disease relapse.

Concentration of Rat Bone Marrow Nucleated Cells Using Hypo-osmotic Hemolysis in Distilled Water

Background:

Bone marrow aspirates contain primarily red blood cells. To achieve efficient cell transplantation for regeneration, the red blood cells need to be removed from the aspirates. Cell isolation is typically performed using density gradient centrifugation. However, this method entails issues of clinical safety and convenience. This study describes an efficient method to concentrate bone marrow nucleated cells by hypo-osmotic hemolysis.

Methods:

The optimal hemolysis conditions were determined by diluting the bone marrow suspensions with distilled water in various dilution ratios. Then, the resulting cell fractions were transplanted in a rat cranial defect model to evaluate their effects on bone formation and their angiogenic effects.

Results:

The optimal hemolysis conditions were a 3.3-fold dilution in distilled water and a hypo-osmotic exposure time of 45 seconds. Nucleated cells obtained using this method included granulocytes and mononuclear cells. These cells contain cytoplasmic angiogenic factors, including vascular endothelial growth factor, basic fibroblast growth factor, and hepatocyte growth factor. In a rat cranial defect model, callus formation and angiogenesis were significantly increased following transplantation of concentrated marrow nucleated cells in this manner.

Conclusions:

These results suggest angiogenic and osteogenetic effects of transplanting marrow nucleated cells using this hypo-osmotic method.

Early recipient chimerism testing in the T- and NK-cell lineages for risk assessment of graft rejection in pediatric patients undergoing allogeneic stem cell transplantation

Timely diagnosis of impending graft rejection is crucial for effective therapeutic intervention after allogeneic hematopoietic stem cell transplantation (SCT). We have investigated the predictive potential of early leukocyte subset-specific chimerism for graft loss in children undergoing SCT. In total, 192 pediatric patients transplanted for the treatment of malignant and non-malignant diseases after reduced-intensity or myeloablative conditioning were investigated. Surveillance of lineage-specific chimerism was initiated upon first appearance of leukocyte counts amenable to cell sorting. Graft rejection occurred in 23 patients between 24 and 492 days post-transplant (median 63 days). The first chimerism analysis of T and NK cells performed at a median of 20 days after SCT identified three different risk groups that were independent from the conditioning regimen: recipient chimerism (RC) levels in T cells below 50% indicated a very low risk of rejection (1.4%), whereas high levels of RC (>90%) both in T and NK cells heralded graft loss in the majority of patients (90%) despite therapeutic interventions. RC >50% in T cells and ≤90% in NK cells defined an intermediate-risk group in which timely immunotherapy frequently prevented rejection. Early assessment of T- and NK-cell chimerism can therefore be instrumental in the risk assessment and therapeutic management of imminent graft rejection.

CD34+ Cell Enumeration by Flow Cytometry: A Comparison of Systems and Methodologies

Context.—An increasing number of medical centers can collect bone marrow, peripheral blood, or umbilical cord stem cells. Pathology laboratories should accommodate this trend, but investment in additional equipment may be impractical.

Objectives.—To compare CD34+ cell counting results by using 2 widely available flow cytometry systems, with and without the use of a separate hematology analyzer (ie, single-platform versus dual-platform methodologies).

Design.—Whole blood and peripheral blood stem cell (PBSC) samples were analyzed from 13 healthy allogeneic PBSC donors and 46 autologous PBSC donors with various malignancies. The Cytomics FC500 (Beckman Coulter, Fullerton, California) was compared with the FACSCalibur (BD Biosciences, San Jose, California). Dual-platform CD34+ cell counting incorporated data from a KX-21 hematology analyzer (Sysmex, Kobe, Japan).

Results.—Subtle differences in CD34+ cell counting between 2 systems and 2 methods did not achieve statistical significance.

Conclusion.—Different systems and methods for CD34+ cell enumeration, properly validated, can support care for patients undergoing transplants and provide meaningful data for multicenter studies or meta-analyses.

Flow cytometric monitoring of hematopoietic reconstitution in myeloablated patients following allogeneic transplantation

BACKGROUND

We report a routine flow cytometric (FACS) approach to quantify circulating leukocytes (NC) in myeloablated patients before and during regeneration after allogeneic transplantation of either whole bone marrow (BM) or of highly purified (> 99%) blood-derived CD34(+) cells (PBSC).

METHODS

Blood samples were analyzed daily between infusion of the transplant and hematopoietic reconstitution. Significant differences in the composition of NC types and CD34(+) cells were observed between the two CD34 sources. The detection threshold for NC was roughly 1 cell per w L blood.

RESULTS

The cell nadir of < 100 NC/ microL was reached on Day +4 (BM) and on day 0 (PBSC), when unusual CD34(+) cells of recipient genotype were detected in all patients. They were not clonogenic, showed high CD34 expression, but were negative for CD45, CD38, CD33, CD50, HLA-DR and Stro-1. Between Days +5 and +16, the onset of hematopoietic reconstitution was clearly detectable in multi-parameter evaluation of the FACS data. This was a median of 3.5 days before NC increased above 200/ w L blood and 4-10 days before granulocyte counts were > 500/ microL. It was marked by the appearance of monocytes, immature (CD38(+)) granulocytes, and clonogenic donor CD34(+) cells exhibited normal size and phenotype.

DISCUSSION

We conclude that dynamic FACS analyses can reliably detect hematopoietic reconstitution, but also graft rejection, before a visible increase NC numbers. This may have considerable impact on clinical management strategies.

Monitoring of adenovirus load in stool by real-time PCR permits early detection of impending invasive infection in patients after allogeneic stem cell transplantation

Invasive adenovirus (AdV) infections are associated with high morbidity and mortality in allogeneic stem cell transplant recipients. We observed that molecular detection of the virus in stool specimens commonly precedes AdV viremia, suggesting that intestinal infections may represent a common source of virus dissemination. To address this notion, we have investigated 153 consecutive allogeneic transplantations in 138 pediatric patients by quantitative monitoring of AdV in stool specimens and peripheral blood by a pan-adenovirus real-time (RQ)-PCR approach. AdV was detectable in serial stool specimens in all cases of AdV viremia during the post-transplant course (P<0.0001). The incidence of AdV viremia in individuals with peak virus levels in stool specimens above 1 x 10E6 copies per gram (n=22) was 73% vs 0% in patients with AdV levels in stool specimens below this threshold (n=29; P<0.0001). Serial measurement of AdV levels in stool specimens by RQ-PCR permitted early diagnosis of impending invasive infection with a sensitivity and specificity of 100% (95% confidence interval (CI) 96-100%) and 83% (95% CI 67-92%), respectively. The median time span between detection of AdV loads in stool specimens above 1 x 10E6 copies per gram and first observation of viremia was 11 days (range 0-192). Quantitative monitoring of the AdV load in stool specimens therefore provides a rationale for early initiation of antiviral treatment with the aim of preventing progression to life-threatening invasive infection.

The anti-cell death FNK protein protects cells from death induced by freezing and thawing

The FNK protein, constructed from anti-apoptotic Bcl-xL with enhanced activity, was fused with the protein transduction domain (PTD) of the HIV/Tat protein to mediate the delivery of FNK into cells. The fusion protein PTD-FNK was introduced into chondrocytes in isolated articular cartilage-bone sections, cultured neurons, and isolated bone marrow mononuclear cells to evaluate its ability to prevent cell death induced by freezing and thawing. PTD-FNK protected the cells from freeze-thaw damage in a concentration-dependent manner. Addition of PTD-FNK with conventional cryoprotectants (dimethyl sulfoxide and hydroxyethyl starch) increased surviving cell numbers around 2-fold compared with controls treated only with the cryoprotectants. Notably, PTD-FNK allowed CD34+ cells among bone marrow mononuclear cells to survive more efficiently (12-fold more than the control cells) from two successive freeze-thaw cycles. Thus, PTD-FNK prevented cell death induced by freezing and thawing, suggesting that it provides for the successful cryopreservation of biological materials.

Lineage-specific chimaerism after stem cell transplantation in children following reduced intensity conditioning: potential predictive value of NK cell chimaerism for late graft rejection

Chimaerism of FACS-sorted leucocyte subsets (CD14+, CD15+, CD3-/56+, CD3+/4+, CD3+/8+, CD19+) was monitored prospectively between days +14 and +100 in 39 children undergoing allogeneic stem cell transplantation with reduced intensity-conditioning regimens. Cell subsets exceeding 1% of nucleated cells were subject to cell sorting. Chimaerism was analysed by dual-colour FISH and/or by short tandem repeat-polymerase chain reaction. The chimaerism pattern on day +28 was evaluated with regard to its correlation with graft rejection. Of 39 patients, nine patients had donor chimaerism (DC) in all subsets. Mixed/recipient chimaerism (MC/RC) was detectable within T cells in 62%, within NK cells in 39% and within monocytes and granulocytes in 38% of the patients. The correlation of secondary graft rejection with the chimaerism pattern on day +28 revealed the strongest association between RC in NK-cells (P<0.0001), followed by T cells (P=0.001), and granulocytes and monocytes (P=0.034). Notably, patients with RC in T cells rejected their graft only if MC or RC was also present in the NK-cell subset. By contrast, none of the children with DC in NK cells experienced a graft rejection. These observations suggest that, in the presence of recipient T-cell chimaerism, the chimaerism status in NK-cells on day +28 might be able to identify patients at high risk for late graft rejection.

A multicolor, no-lyse no-wash assay for the absolute counting of CD34+ cells by flow cytometry

BACKGROUND

We previously developed a method for counting CD34(+) cells in unlysed whole blood. This method was applied to normal human bone marrow, peripheral blood after mobilization of progenitor cells, leukapheresis products, and cord blood and was validated with two different lyse-no wash methods. However, the main advantage that we described, erythrocyte discrimination using nucleic acid staining, was also the main restriction because additional markers for the immunologic characterization of CD34(+) cells cannot be included.

METHODS

We used SYTO-13 and fluorescein isothiocyanate (FITC)-CD45 staining (FL1) instead of SYTO-13 and phycoerythrin (PE)Cy5-CD45 staining (FL3) to leave the third and fourth fluorescence parameters available for further characterization of CD34(+) cells. The new method was validated by applying it to cord blood samples (n = 20).

RESULTS

FITC-CD45 antibody gave a 1.7-fold increase in mean fluorescence intensity over SYTO-13 alone. From absolute counts (CD34(+) cells per microliter), we plotted the differences between the methods against their mean, showing that differences fell into acceptable ranges.

CONCLUSIONS

No-lyse procedures may represent an advance for cell immunophenotyping and it could be applied to the measurement of additional markers. Cytometry (Clin. Cytometry) 50:249-253, 2002.

Collection efficiencies of MNC subpopulations during autologous CD34+ peripheral blood progenitor cell (PBPC) harvests in small children and adolescents

There is increasing demand for mononuclear cell (MNC) harvests not only for PBPC but also for immune therapies using dendritic cells and donor lymphocytes. We determined the collection efficiencies (CE) of various MNC subpopulations during CD34+ cell harvests using a Fenwal CS 3000 Plus Omnix system in small children and adolescents. The cell content of 140 leukapheresis products (LP) was prospectively evaluated in 45 pretreated patients with solid tumors and hematological malignancies. The median age was 12 years (range 0.8-22), and the median body weight (BW) 43 kg (range 9-92). Depending upon the BW of the patients, the media used for priming were saline (SP) in 86, human albumin (HA, HAP) in 10, and packed red blood cells (BP) in 44 apheresis procedures. The major nucleated cell (NC) fractions collected were monocytes (52% of NC) and CD3+ T cells (26%). The median cell yield for monocytes was 174 * 10(6)/kg (range 24-613) representing a CE of 55%. The median number of CD3(+) T cells was 84 * 10(6)/kg (range 5.6-380; CE = 74%). CD34+ cells represented a very small cell fraction of the LP (1.3% of NC), with a median yield of 4.2 * 10(6)/kg (range 0.2-87) and a CE of 63%. The cell yield of various MNCs was significantly correlated with the cell count in the peripheral blood (PB) and with the blood volume processed (ANOVA, P < 0.0001). No influence on the CE was observed for the priming procedure, the patients' age or sex, or the other adaptations used in the harvesting protocol. In conclusion, the Fenwal CS 3000 Plus OMNIX system with the CD34+ cell program and the described adaptations, is also predictably useful for harvest of monocytes or lymphocytes in pediatric patients. We present regression equations that predict the cell yield of various MNC subpopulations in apheresis products.

Ex vivo expansion of long-term culture initiating marrow cells by IL-10, SCF, and IL-3

BACKGROUND

Ex vivo expansion of progentior cells may shorten hematopoietic regeneration after myeloablative chemoradiotherapy, increase target cells for gene therapy, and improve purging of progenitor cell components.

STUDY DESIGN AND METHODS

Marrow cells were incubated for 1 week in suspension culture with and without IL-10, IL-3, and SCF. As long-term culture initiating cells (LTC-ICs) represent early hematopoietic progenitors in vitro, these cells were quantified at initiation and after a 1-week culture period in a limiting dilution assays. Additionally, immunophenotyping of cells before and after culture was performed.

RESULTS

In six experiments, marrow cells cultured for 1 week with IL-10, IL-3, and SCF showed a significant increase (almost doubling) in LTC-ICs as compared with marrow cells before expansion. Additionally, an increased proliferative capacity of LTC-ICs was achieved with a sevenfold increase of committed colony-forming cells and a 10-fold proliferation of high proliferative potential colony-forming cells. Immunophenotyping revealed a sevenfold increase of CD34+ CD45 RA- cells in IL-10-, IL-3-, SCF-stimulated suspension cultures. In unstimulated cultures, no LTC-ICs were maintained after 1 week.

CONCLUSION

Expansion of LTC-ICs by IL-10, IL-3, and SCF has not been shown so far. This in vitro model allows expansion of LTC-IC if compared with the input of progenitor cells without extensive progenitor cell manipulation. This should be an attractive model for in vitro purging, gene transfer, or expansion of progenitor cells to allow rapid engraftment after myeloablative chemotherapy.

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.

IL-10 increases the number of CFU-GM generated by ex vivo expansion of unmanipulated human MNCs and selected CD34+ cells

BACKGROUND

Ex vivo expansion strategies with different cytokine combinations are currently used by several groups as a means of increasing the number of HPCs for a variety of special clinical applications. Because there is little information on the potential role of IL-10 in such ex vivo expansion models, the effect of this cytokine on the generation of myeloid progenitor cells in suspension cultures was investigated.

STUDY DESIGN AND METHODS

On the basis of data from the literature and from new experiments, the combination of SCF and IL-3 at concentrations of 100 ng per mL and 100 U per mL, respectively, was chosen as the standard cocktail. The addition of IL-10 to such cultures resulted in a marked and dose-dependent potentiation of myeloid progenitor cell production.

RESULTS

Using unmanipulated leukapheresis components from 13 individuals (including lymphoma and cancer patients and normal donors), the expansion multiple of CFU-GM after 14 days as compared with pre-expansion values was 9.54 +/- 2.31 times by SCF/IL-3 and 46.38 +/- 7.37 times by the combination of SCF/IL-3 and 100 ng per mL of IL-10 (p<0.001). IL-10 also potentiated CFU-GM generation from selected CD34 PBMNCs (n = 9) with an expansion of 17.22 +/- 7.04 times versus 45.67 +/- 16.78 times using the SCF/IL-3 and SCF/IL-3/IL-10 combination, respectively (p<0.05). Moreover, expansion-promoting effects of IL-10 were observed in liquid cultures containing MNCs from bone marrow (n = 4) and cord blood (n = 3), but did not reach statistical significance because of the small number of samples.

CONCLUSION

These results suggest IL-10 as a useful cytokine to optimize progenitor cell-expansion strategies for clinical application.

Permanent tunneled silicone central venous catheters for autologous PBPC harvest in children and young adults

Children with high risk malignancies are usually given permanent (Hickman-type) tunneled silicone rubber central venous catheters (silicone CVCs) for the administration of chemotherapy. In the past, these children received an additional short-term polyurethane dialysis CVC for stem cell apheresis. To avoid placement of an additional short-term CVC, we started in 1995 to use pre-existing silicone CVCs for PBPC harvests. From May 1996 to February 1999 we evaluated 165 harvests in 37 children and 14 young adults (16-28 years) treated with high-dose chemotherapy and stem cell support, comparing CD34+ cell harvest efficiency, catheter tolerability, and complications in three different approaches to vascular access. Pre-existing silicone CVCs (64%) or peripheral venous cannulae (15%) were the first choice for venous access. Only when these failed were polyurethane CVCs (21%) used. No significant difference was seen between these three groups, even after dividing the silicone CVC group (105 harvests in 32 patients) into three subgroups according to weight and age. The most frequent problems were citrate toxicity (n = 33), mechanical obstruction inside (n = 9) and outside the cell separator (n = 2), decreased draw line flow in silicone CVCs (n = 7), decreased draw line flow in peripheral venous cannulae (n = 6), and one occlusion in a polyurethane CVC. Pre-existing CVCs and peripheral venous cannulae functioned efficiently when used as a draw line in 79% of the apheresis procedures without significantly reducing single harvest efficiency or catheter tolerability. Consequently, the risks and costs associated with the placement of a dialysis CVC could be avoided in the majority of cases. Bone Marrow Transplantation (2000) 26, 781-786.

[Flow cytometry: applications in transfusion medicine]

In transfusion medicine, flow cytometry (FCM) is a methodology combining laser radiation, optics and a computerized treatment of numerous results. We can measure size, cellularity and fluorescence intensity of cells or particles in suspension after the binding of appropriate fluorescent antibodies or fluorescent dyes. The main utilisation of FCM in transfusion medicine is for quality control of the process of leukocyte reduction in red cell concentrates or in platelet units, using commercial kits. In addition, it is used for the enumeration of CD 34 positive cells before bone marrow transplantation and for control of platelet function in platelet units. For clinical investigations, FCM may be used for red cell phenotyping, essentially to detect minor populations (chimerism), for the estimation of red cell survival, or for the detection of fetal erythrocytes. In the field of platelet immunology, FCM is an essential tool for detecting platelet antibodies (auto or allo), for platelet phenotyping or for cross-matching. In the future perhaps, FCM will permit us to detect bacterial contamination or prion protein in transfused blood cells.

Loss of CD34(+) hematopoietic progenitor cells due to washing can be reduced by the use of fixative-free erythrocyte lysing reagents

Current protocols for sample preparation before flow cytometric enumeration of CD34(+) hematopoietic progenitor cells (HPC) include both lyse-non-wash and lyse and wash methods. Erythrocyte lysis without washing is the method of choice when absolute cell counts are to be assessed, whilst a washing step is recommended for immunological subtyping of CD34(+) cells in order to reduce background fluorescence. Here, we analyzed the effect of the interaction between type of erythrocyte lysis reagent and washing on the outcomes of (i) CD34(+) cell enumeration and (ii) expression of CD38 by CD34(+) cells in a single-platform, whole-blood staining assay [Gratama, J.W., Keeney, M., Sutherland, D.R., 1999. Enumeration of CD34(+) hematopoietic stem cell and progenitor cells. Curr. Protocols Cytometry 6(4), 1-22.]. We studied seven commercially available lysing reagents (five containing fixative and two fixative-free) using 12 samples from cord blood (n=4), mobilized peripheral blood (n=4) and apheresis products (n=4). Using the lyse and wash technique, significant reductions of absolute and relative numbers of CD34(+) cells, as well as in the numbers of lymphocytes and leukocytes, were observed on samples that had been lysed using fixative-containing buffers as compared to the lyse-no-wash technique. Cell losses due to washing could be significantly reduced when samples were lysed using fixative-free buffers. 'Postfixation' using PBS+1% paraformaldehyde of samples that had been lysed using fixative-free buffers and then washed did not result in additional loss of CD34(+) cells or other cell types. Finally, washing unfixed samples led to a slight decrease of CD38 monoclonal antibody bound to CD34(+) cells as compared to samples that had been fixed during erythrocyte lysis. These results indicate that fixation renders (CD34(+)) cells sticky and leads to their loss from the cell suspension upon centrifugation and resuspension. We conclude that all seven lysing reagents can be used with confidence in a lyse-no-wash technique, but that only fixative-free lysing reagents should be used when a washing step is considered necessary.

Quantitative flow cytometry for the analysis of T cell receptor Vbeta chain expression

Detailed characterisation of the T cell receptor (TCR) repertoire expressed by peripheral blood lymphocytes has been used to study specific T cell responses in disease conditions. The methods have mostly involved molecular biology analysis of transcribed gene products isolated from T cell subsets or individual clones. Extensive characterisation of the TCR Vbeta chain repertoire by flow cytometry is now possible due to the recently increased availability of specific monoclonal antibodies. However, there are major logistical problems inherent in this analysis relating to the number of cells required to obtain accurate results and the vast amounts of data generated. To reduce these factors to a practical level, we have performed a detailed study to define the limits of precision of cell subset analysis by flow cytometry. Maximal achievable precision was obtained by analysing 10(4) lymphocytes; no significant improvement was obtained by analysing greater numbers of cells up to 10(5) cells, even for cell subsets present at frequencies as low as 0.5%. Careful application of these precision profiles will also permit more effective use of clinical research samples for flow cytometry when the availability of cells is limited.

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.