Primordial role of CD34+ 38- cells in early and late trilineage haemopoietic engraftment after autologous blood cell transplantation

In order to better define which cell subset contained in graft products might be the most predictive of haemopoietic recovery following autologous blood cell transplantation (ABCT), the relationships between the amounts of reinfused mononuclear cells (MNC), CFU-GM, total CD34+ cells and their CD33 and CD38 subsets. and the successive stages of trilineage engraftment kinetics, were studied in 45 cancer patients, using the Spearman correlation test, a linear regression model and a log-inverse model. No relationship was found between the infused numbers of MNC, CD33+ and CD33- subsets observed and the numbers of days to reach predetermined absolute neutrophil (ANC), platelet and reticulocyte counts. The infused numbers of CFU-GM, CD34+ and CD34+ 38+ cells correlated inconstantly with haemopoietic recovery parameters. The strongest and the most constant correlations were significantly observed between the infused numbers of CD34+ 38- cells and each trilineage engraftment parameter. The log-inverse model determined a threshold dose of 0.05 x 10(6) (= 5 x 10(4)) CD34+ 38- cells/kg, below which the trilineage engraftment kinetics were significantly slower and unpredictable. Post-transplant TBI-conditioning regimens increased the low cell dose-related delay of engraftment kinetics whereas post-transplant administration of haemopoietic growth factors (HGF) seemed to abrogate this delay. This would justify clinical use of HGF only in patients transplanted with CD34+ 38- cell amounts lower than the proposed threshold value. This study suggests that the CD34+ 38- subpopulation, although essentially participating in late complete haemopoietic recovery, is also composed of committed progenitor cells involved in early trilineage engraftment.     

CD34+CD33- cells influence days to engraftment and transfusion requirements in autologous blood stem-cell recipients

PURPOSE: To evaluate the reliability of CD34/CD33 subset enumeration as a predictor of hematopoietic repopulating potential in autologous blood stem-cell transplantation and to determine which patient and treatment-related factors affect the timing, quantity, and type of blood stem cells mobilized. PATIENTS AND METHODS: We analyzed blood stem-cell collections from 410 consecutive cancer patients who received mobilization therapy and evaluated factors, including CD34+ subset quantities, that might influence engraftment kinetics and transfusion requirements in autologous blood stem-cell recipients. RESULTS: The majority of patients (97%) mobilized CD34+33- cells, which were usually collected in the greatest quantity on the first day of apheresis. Patients who received only growth factor mobilized the highest percentage of CD34+33- cells. Extensive prior chemotherapy limited the collection of CD34+33- cells. In addition to patient diagnosis (P < .006) and total CD34+ cell dose (P = .0001), CD34+33- cell dose (P < .005) and percentage of CD34+33- cells (P < .005) were identified as independent factors significantly predictive of engraftment kinetics. CD34+33- cell dose (R2 < or = .177; P < .0001) was a strong and the only significant predictor of RBC and platelet transfusion requirements. Furthermore, independent of the total CD34+ cell dose, as the CD34+33- cell dose increased, days to neutrophil recovery, days to platelet recovery, and transfusion requirements decreased. CONCLUSION: These findings show that CD34+33- cells are readily collected in most cancer patients and significantly influence engraftment kinetics and transfusion requirements in autologous blood stem-cell recipients. CD34+33- cell quantity of the blood stem-cell graft appears to be a more reliable predictor of hematopoietic recovery rates than total CD34+ cell quantity in this setting.     

Blast counts in blood progenitor cell (BPC) correlate with CD34+ cells and CFU-GM and are useful predictor of haemopoietic recovery after autologous BPC transplantation collections

Assessment of the quality of blood progenitor cell (BPC) collections is based mainly on CD34+ cell enumeration by flow cytometry, or scoring of granulocyte-macrophage colony-forming cells (CFU-GM). A minimum cell dose for haemopoietic recovery can be defined by both assays; however, the CFU-GM assay can not be used for 'real-time' decisions, whereas CD34+ cell scoring requires facilities and expertise which are not universally available. We have investigated the possibility of using morphologically defined blast cells within BPC harvests as a surrogate marker of harvest haemopoietic stem/progenitor cell content, as well as their correlation with CD34+ cells and CFU-GM within the harvests. We have found that blast counts correlate strongly with both CD34+ cell counts and CFU-GM within BPC harvests, as well as with time to granulocyte and platelet recovery after autologous BPC transplantation (ABPCT). Furthermore, we have defined a threshold value of 1.3 x 10(6)/kg blasts, above which there is a high probability of rapid haemopoietic recovery after ABPCT. We conclude that blast count is a simple, rapid and reliable method of assessing BPC harvest quality.     

The role of granulocyte colony-stimulating factor in mobilization and transplantation of peripheral blood progenitor and stem cells

The article provides a review of the role of granulocyte colony-stimulating factor (G-CSF) for mobilization and transplantation of peripheral blood progenitor and stem cells. Recombinant gene technology has permitted the production of highly purified material for therapeutic use in humans. Progenitor cells can be assessed using semisolid and liquid culture assays or direct immunofluorescence analysis of cells expressing CD34. This antigen is found on lineage-determined hematopoietic progenitor cells as well as on more primitive stem cells with extensive self-renewal capacity. Administration of G-CSF during steady-state hematopoiesis or following cytotoxic chemotherapy leads to an increase of hematopoietic progenitor cells in the peripheral blood. The level of circulating CD34+ cells post-chemotherapy is greater compared with G-CSF administration during steady state. On the other hand, CD34+ cells harvested post-chemotherapy contain a smaller proportion of more primitive progenitor cells (CD34+/HLA-DR- or CD34+/CD38-) compared with G-CSF treatment alone. Independent of the mobilization modality, the amount of previous cytotoxic chemo- and radiotherapy adversely affects the yield of hematopoietic progenitor cells. While continuous subcutaneous administration of G-CSF between 5 and 16 micrograms/kg bodyweight is preferred, additional dose-finding studies may be helpful to optimize current dose schedules. Adhesion molecules like L-selectin, VLA (very late antigen)-4 and LFA (leukocyte function antigen)-1 are likely to play a role in mobilization, since these antigens are expressed on CD34+ cells from bone marrow in different densities compared with blood-derived CD34+ cells collected following G-CSF-supported cytotoxic chemotherapy. It is also relevant for transplantation that during G-CSF-enhanced recovery post-chemotherapy, peripheral blood is enriched with a greater proportion of CD34+ cells expressing Thy-1 in comparison with CD34+ cells from bone marrow samples obtained on the same day or before the mobilization therapy was started. The early nature of the CD34+/Thy-1+ cells is very likely since this phenotype has been found on stem cells from human fetal liver and bone marrow and on cord blood cells. As a result, G-CSF-mobilized blood stem cells provide rapid and sustained engraftment following high-dose therapy, including myeloablative regimens. Positive selection of CD34+ cells as well as ex vivo expansion using different cytokines are currently being investigated for purging and improvement of short-term recovery post-transplantation. Future developments include the use of blood-derived hematopoietic stem cells for somatic gene therapy. The availability of growth factors has been an important prerequisite for the development of these new avenues for cell therapy.     

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 x 10(9)/L) and unsustained platelet recovery (>50 x 10(9)/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 x 10(6) CD34(+) cells/kg, a high group with greater than 15 x 10(6) 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 x 10(6) CD34(+) cells/kg after high-dose chemotherapy for lymphoproliferative diseases further shortens hematopoietic reconstitution, reduces platelet requirements, and may improve patients' quality of life.     

Collection, tumor contamination, and engraftment kinetics of highly purified hematopoietic progenitor cells to support high dose therapy in multiple myeloma

Unfractionated peripheral blood stem cell (PBSC) grafts contain measurable quantities of myeloma cells and are therefore a potential source of relapse posttransplantation. In contrast, fluorescence-activated cell sorting (FACS)-sorted CD34+ Thy1+ Lin- peripheral blood cells are substantially enriched for stem cell activity, yet contain virtually no clonal myeloma cells. A study was performed in patients with symptomatic myeloma, who had received 12 months or less of preceding standard chemotherapy, to evaluate the feasibility of large scale purification of primitive hematopoietic stem cells in order to study engraftment kinetics posttransplantation and the degree of tumor cell contamination of this cell population, based on polymerase chain reaction (PCR) analysis for the patient-specific complementarity-determining region III (CDR III). PBSC were mobilized with high dose cyclophosphamide and granulocyte-macrophage colony-stimulating factor (GM-CSF). A combination of elutriation and chemical lysis was used to deplete PBSC collections of monocytes, granulocytes, erythrocytes, and platelets. Subsequently, CD34+ Thy1+ Lin- progenitor cells were purified with high speed cell sorting. Of the 10 evaluable patients, nine met the required minimum criteria of >/=7.2 x 10(5) cells/kg to support tandem transplants. After high dose melphalan (200 mg/m2) eight engrafted successfully, although granulocyte (absolute neutrophil count [ANC] >0.5 x 10(9)/L, 16 days) and platelet recovery (platelets > 50 x 10(9)/L, 39 days) was substantially delayed when compared with unmanipulated PBSC grafts; one patient required infusion of a reserve graft because of lack of evidence of engraftment by day +28. Three patients proceeded to a second graft with high dose melphalan and total body irradiation; two required infusion of a reserve graft and both died of infectious complications; one showed delayed, but complete, engraftment after this myeloablative regimen. Two of the nine evaluable patients attained a clinical complete remission (CR). The grafts from three patients were tested for tumor contamination and contained no detectable clonal myeloma cells. Larger quantities of purified cells may be required to resolve the problem of delayed engraftment.     

2-Hydroxyisonicotinate dehydrogenase isolated from Mycobacterium sp. INA1

The objective of this study was to identify factors associated with poor mobilization of peripheral blood progenitor cells (PBPCs) or delayed platelet engraftment after high-dose therapy and autologous stem cell transplantation in patients with lymphoma. Fifty-eight patients with Hodgkin's disease or non-Hodgkin's lymphoma underwent PBPC transplantation as the "best available therapy" at Memorial Sloan-Kettering Cancer Center (New York, NY) between 1993 and 1995. PBPCs were mobilized with either granulocyte colony-stimulating factor (G-CSF) alone (n = 19) or G-CSF following combination chemotherapy (n = 39). Forty-eight of these patients underwent a PBPC transplant, receiving a conditioning regimen containing cyclophosphamide, etoposide, and either total body irradiation, total lymphoid irradiation, or carmustine. A median number of 4.6 x 10(6) CD34+ cells/kg were obtained with a median of three leukapheresis procedures. Mobilization of PBPCs using chemotherapy plus G-CSF was superior to G-CSF alone (6.7 x 10(6) versus 1.5 x 10(6) CD34+ cells/kg; P = 0.0002). Poorer mobilization of progenitor cells was observed in patients who had previously received stem cell-toxic chemotherapy, including (a) nitrogen mustard, procarbazine, melphalan, carmustine or > 7.5 g of cytarabine chemotherapy premobilization (2.0 x 10(6) versus 6.0 x 10(6) CD34+ cells/kg; P = 0.005), or (b) > or = 11 cycles of any previous chemotherapy (2.6 x 10(6) versus 6.7 x 10(6) CD34+ cells/kg; P = 0.02). Platelet recovery to > 20,000/microliter was delayed in patients who received < 2.0 x 10(6) CD34+ cells (median, 13 versus 22 days; P = 0.06). Patients who received > or = 11 cycles of chemotherapy prior to PBPC mobilization tended to have delayed platelet recovery to > 20,000/microliter and to require more platelet transfusions than less extensively pretreated patients (median, 13.5 versus 23.5 days; P = 0.15; median number of platelet transfusion episodes, 13 versus 9; P = 0.17). These data suggest that current strategies to mobilize PBPCs may be suboptimal in patients who have received either stem cell-toxic chemotherapy or > or = 11 cycles of chemotherapy prior to PBPC mobilization. Alternative approaches, such as ex vivo expansion or the use of other growth factors in addition to G-CSF, may improve mobilization of progenitor cells for PBPC transplantation.     

Dendritic cell-based vaccines in the setting of peripheral blood stem cell transplantation: CD34+ cell-depleted mobilized peripheral blood can serve as a source of potent dendritic cells

We are investigating the use of tumor-pulsed dendritic cell (DC)-based vaccines in the treatment of patients with advanced cancer. In the current study, we evaluated the feasibility of obtaining both CD34+ hematopoietic stem/ progenitor cells (HSCs) and functional DCs from the same leukapheresis collection in adequate numbers for both peripheral blood stem cell transplantation (PBSCT) and immunization purposes, respectively. Leukapheresis collections of mobilized peripheral blood mononuclear cells (PBMCs) were obtained from normal donors receiving granulocyte colony-stimulating factor (G-CSF) (for allogeneic PBSCT) and from intermediate grade non-Hodgkin's lymphoma or multiple myeloma patients receiving cyclophosphamide plus G-CSF (for autologous PBSCT). High enrichment of CD34+ HSCs was obtained using an immunomagnetic bead cell separation device. After separation, the negative fraction of mobilized PBMCs from normal donors and cancer patients contained undetectable levels of CD34+ HSCs by flow cytometry. This fraction of cells was then subjected to plastic adherence, and the adherent cells were cultured for 7 days in GM-CSF (100 ng/ml) and interleukin 4 (50 ng/ml) followed by an additional 7 days in GM-CSF, interleukin 4, and tumor necrosis factor alpha (10 ng/ml) to generate DCs. Harvested DCs represented yields of 4.1+/-1.4 and 5.8+/-5.4% of the initial cells plated from the CD34+ cell-depleted mobilized PBMCs of normal donors and cancer patients, respectively, and displayed a high level expression of CD80, CD86, HLA-DR, and CD11c but not CD14. This phenotypic profile was similar to that of DCs derived from non-CD34+ cell-depleted mobilized PBMCs. DCs generated from CD34+ cell-depleted mobilized PBMCs elicited potent antitetanus as well as primary allogeneic T-cell proliferative responses in vitro, which were equivalent to DCs derived from non-CD34+ cell-depleted mobilized PBMCs. Collectively, these results demonstrate the feasibility of obtaining both DCs and CD34+ HSCs from the same leukapheresis collection from G-CSF-primed normal donors and cancer patients in sufficient numbers for the purpose of combined PBSCT and immunization strategies.     

High-dose therapy with peripheral blood stem cell transplantation results in a significant reduction of the haemopoietic progenitor cell compartment

In order to study the effect of high-dose therapy with peripheral blood stem cell transplantation (PBSCT) on the haemopoietic reserve in man, the number and composition of bone marrow (BM) and peripheral blood (PB)-derived progenitor cells were examined in 137 cancer patients. In 45 patients, paired samples from BM and PB were obtained before PBSC mobilization and 6-27 months after transplantation. Following PBSCT. the proportion of CD34+ cells was significantly smaller than before mobilization (BM 1.99 +/- 0.24 versus 0.8 +/- 0.09, P < 0.001), and no change was observed at several follow-up visits thereafter. The reduction was most pronounced for the primitive BM progenitor subsets such as the CD34+/DR- and CD34+/ Thy-1+ cells. The impairment of hematopoiesis was also reflected by a significant reduction in the plating efficiency of BM and PB samples. No relationship was found between the decrease in the proportion of CD34+ cells and any particular patient characteristics, kind of high-dose therapy or the CD34+ cell content in the autograft. In conclusion, high-dose therapy with PBSC transplantation is associated with a long-term impairment of the haemopoietic system. The reduction in the number of haemopoietic progenitor cells is not associated with a functional deficit, as peripheral blood counts post-transplantation were normal in the majority of patients.     

CD34 positive blood cells for allogeneic progenitor and stem cell transplantation

The transplantation of allogeneic peripheral blood progenitor cells (PBPC) provides complete and sustained hematopoietic and lymphopoietic engraftment. In healthy donors, large amounts of PBPC can be mobilized with hematopoietic growth factors. However, the high content of immunocompetent T-cells in apheresis products may expose recipients of allogeneic PBPC to an elevated risk of acute and chronic graft-versus-host disease. Thus, the use of appropriate T-cell reduction, but not depletion might reduce this risk. The hazards of graft rejection and a higher relapse rate can be avoided by maintaining a portion of the T-cells in the graft. The positive selection of CD34+ cells from peripheral blood preparations simultaneously provides an approximately 1000-fold reduction of T-cells. These purified CD34+ cells containing committed and pluripotent stem cells are suitable for allogeneic transplantation and can be used in the following instances: 1. As hematopoietic stem and progenitor cell transplantation instead of bone marrow cells, from HLA-identical family donors; 2. for increasing the stem cell numbers from HLA-mismatched or three HLA-loci different family donors in order to reduce the incidence of rejection but without increasing the T-cell number; 3. boosting of poor marrow graft function with stem cells from the same family donors; 4. transplantation from volunteer matched unrelated donors; 5. split transplantation of CD34+ and T-cells; 6. addition of ex vivo expanded CD34+ cells to blood cell or bone marrow transplantation; 7. generation of antigen specific immune effector cells and antigen presenting cells for cell therapy.     

The pathologic significance of the immunoglobulins expressed by chronic lymphocytic leukemia B-cells in the development of autoimmune hemolytic anemia

Since the discovery of the CD34 stem/progenitor cell antigen, considerable progress has been made in further purifying human lymphohematopoietic stem cells (HSC). These studies have identified a number of antigens which can be targeted to subfractionate the CD34+ cell population. In particular, several lines of evidence suggest that the rare CD38(-)subpopulation of CD34+ cells may be enriched in HSC. This review briefly summarizes relevant knowledge concerning the CD38 molecule and the results of in vitro and in vivo studies of CD34+38(-)cells. Possible clinical uses for purified CD34+38(-)cells are outlined.     

Atelosteogenesis type II is caused by mutations in the diastrophic dysplasia sulfate-transporter gene (DTDST): evidence for a phenotypic series involving three chondrodysplasias

Flow cytometric DNA analysis was performed in combination with three-colour immunological staining of cell surface antigens on density-separated mononuclear cells (MNC) obtained from peripheral blood (PB) before, during and after cytokine stimulation of healthy adults. The aim of the study was to determine the cell-cycling status of haemopoietic progenitor cells mobilized into the blood of healthy volunteers during a 5 d treatment period with 5/micrograms per kg body weight of either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-simulating factor (GM-CSF). Despite considerably increasing numbers of CD34+ PB MNC, the latter were not found to be in S/G2M phase, whereas, among the CD34- MNC, the proportion of cells in S/G2M phase increased from < 0.1% to 0.75 +/- 0.4% (GM-CSF) and to 1.34 +/- 0.75% (G-CSF) and dropped again after discontinuation of the cytokine stimulation. These cells expressed CD33 but were negative for CD45RA, CD3, CD19 and CD14 and were thus considered granulopoietic cells. Analogous results were obtained from analyses of cord blood (CB). In contrast, CD34+ cells from bone marrow (BM) were partially (between 9% and 15%) found to be in S/G2M phase. The non-cycling status of PB and progenitor cells was confirmed by the analysis of CD34+ cells enriched from the two cells sources. However, in vitro stimulation of these progenitor cells using IL3, GM-CSF, erythropoietin and steel factor (SF) revealed that, after 48 h in suspension culture, up to 30% of the CD34+ cells were in S/G2m phase. The fact that cycling CD34+ cells are only detectable in BM but not in PB or CB may suggest different adhesive properties of migrating/mobilized 'stem cells' which may require the BM micro-environment for adequate proliferation in vivo.     

The value of sequential CD 34 measurement for carrying out stem cell pheresis

The recent significant improvement in disease-free survival in patients with certain haematological malignancies is due to high-dose chemotherapy and subsequent autologous bone marrow and/or stem cell transplantation. The proliferation and egression of stem cells into the peripheral blood must first be stimulated by defined chemotherapy and/or by administration of cytokines. However, the increase of circulating stem cells in peripheral blood is limited to only a few days. By immunologically analysing white blood cells for the expression of the surface antigen CD 34 it is possible to calculate the numbers of haematopoietic progenitor cells. Thus, besides monitoring haematopoietic recovery, the estimation of CD34+ cells in the peripheral blood can be used to indicate the optimal time point for stem cell collection. Two to four stem cell pheresis (one per day) may then yield sufficient stem cells to enable the safe and rapid reconstitution of haematopoiesis following supralethal chemotherapy.     

Hematopoietic progenitor cell collection and neoplastic cell contamination in breast cancer patients receiving chemotherapy plus granulocyte-colony stimulating factor (G-CSF) or G-CSF alone for mobilization

BACKGROUND: We compared hematopoietic progenitor cell (HPC) collection and neoplastic cell contamination in breast cancer patients given cyclophosphamide (CTX) plus granulocyte-colony stimulating factor (G-CSF) or G-CSF alone for mobilization. PATIENTS AND METHODS: In 57 stage II-III breast cancer patients, CD34+ cells, colony-forming units-granulocyte macrophage (CFU-GM), early HPC and breast cancer cells were counted in HPC collections obtained after CTX plus G-CSF (n = 27) or G-CSF-alone mobilization (n = 30). RESULTS: The CD34+ cell collection was about two-fold greater after CTX plus G-CSF mobilization (11.0 +/- 7.9 vs. 5.8 +/- 3.5 x 10(6)/kg, P < 0.001). Similarly, the total number of CFU-GM, CD34+CD38- cells and of week-5 cobblestone area forming cells (CAFC) collected was significantly higher in patients mobilized with CTX plus G-CSF. Breast cancer cells were found in the apheresis products of 22% of patients mobilized with CTX plus G-CSF and in 10% of patients mobilized with G-CSF alone (P = 0.36). Of seven patients who failed G-CSF-alone mobilization and eventually underwent chemotherapy plus G-CSF mobilization, none had cytokeratin-positive cells after G-CSF mobilization, whereas four out of seven had cytokeratin-positive cells after chemotherapy plus G-CSF (P = 0.07 by chi 2 test). CONCLUSION: The CTX plus G-CSF mobilization protocol was associated with a significantly higher HPC collection. However, this benefit was not accompanied by a reduction in the incidence of tumor-contaminated HPC graft.     

An elevation of stem cell factor in patients with hyperthyroid Graves'' disease

The dose of cells expressing the surface antigen CD34 (CD34+) has been shown to be a reliable predictor of the time to engraftment following transplantation of PBPC to support high-dose chemotherapy. However, evaluation of rare cells is complicated by a number of factors, including the variability in operator and technical procedures. Recently, Becton Dickinson Immunocytometry Systems introduced a new CD34+ cell analysis system, the ProCOUNT cell enumeration kit, which automates the analysis of CD34+ cells and minimizes the variabilities of this procedure. We have evaluated the ProCOUNT system in comparison to a standard CD34 cell analysis (based on the Milan approach) using leukapheresis products from patients and normal donors mobilized with chemotherapy plus recombinant human G-CSF (rhG-CSF) or with rhG-CSF alone. In addition, we compared these analyses using CD34+ cell-selected mobilized leukapheresis products with purities of 75% or greater. The standard CD34 cell analysis methodology quantitated the frequency of cells identified as CD45+, low side scatter, and CD34+. A high correlation coefficient was obtained between the ProCOUNT methodology and the standard CD34 cell analysis methodology for cells obtained from leukapheresis products mobilized with chemotherapy plus rhG-CSF (r = 0.98), rhG-CSF alone (r = 0.96), and CD34+-selected mobilized leukapheresis products (r = 0.83). A comparison was also made between technicians using both analysis methods. Whereas the correlation coefficient between two technicians using the standard methodology was r = 0.77, the correlation coefficient was much higher when using ProCOUNT (r = 0.99). These data demonstrate that the use of ProCOUNT is associated with less variability between data analyzed by different operators. Also, ProCOUNT is consistent with existing CD34+ cellular analysis methodologies. An additional advantage is the ability to determine the absolute concentration of CD34+ cells, thereby allowing calculation of total CD34+ cell numbers without using WBC counts, which also have inherent errors. The ProCOUNT system provides an automated analysis procedure that minimizes the variables in CD34+ cell analysis and may be useful for standardization of methodology between laboratories.     

High-level expression of a novel epitope of CD59 identifies a subset of CD34+ bone marrow cells highly enriched for pluripotent stem cells

To further define the hierarchy of human hematopoietic progenitor cells, we have attempted to identify antibodies to cell-surface molecules expressed on CD34+ progenitor cell subsets. Herein we describe the utility of a new monoclonal antibody, HCC-1, which binds to a novel epitope of CD59 differentially expressed among CD34+ progenitor cells. HCC-1 subdivides the adult marrow CD34+ population into HCC-1high and HCC-1low/- fractions of approximately equal size. Cobblestone area-forming cells (CAFC) in long-term bone marrow culture were enriched 10-30-fold in CD34+HCC-1high cells compared with CD34+HCC1-low/- cells and two-fold compared with CD34+ cells. When injected into fetal human bone fragments implanted in SCID mice, the CD34+HCC-1high population showed potent engrafting activity leading to the production of myeloid, lymphoid, and erythroid elements, as well as the retention of progenitor cell phenotype. These studies demonstrate that the CD34+HCC-1high population contains primitive pluripotent hematopoietic stem cells. No hematopoietic engrafting activity was detected in the CD34+HCC-1low/- population. Consistent with this finding, simultaneous five-color flow cytometric analysis revealed that HCC-1high cells include virtually all CD34+Thy-1+Lin- cells, a cell population previously characterized as highly enriched for primitive pluripotent hematopoietic stem cells. The ability of CD34+ cells divided into subsets by HCC-1 to produce T cells was assessed by transplantation of sorted cells into human fetal thymus implanted into SCID mice. A higher frequency of thymus-engrafting activity was observed in the CD34+HCC-1high than in the CD34+HCC-1low/- population. Consistent with the limited ability to engraft in the SCID-hu thymus model, the CD34+HCC-1low/- population was shown to contain a low frequency of CD34+CD10+ lymphoid progenitor cells. We conclude that the HCC-1 epitope is expressed at high levels on a subset of CD34+ cells that contain virtually all primitive pluripotent hematopoietic stem cells and that the population of CD59 molecules expressed on CD34+ cells is not homogeneous.     

Does eradication of Helicobacter pylori impair healing of nonsteroidal anti-inflammatory drug associated bleeding peptic ulcers? A prospective randomized study

High-dose therapy with peripheral blood stem cell (PBSC) support is a frequently used treatment option in younger patients with poor prognosis histologically indolent (low-grade) non-Hodgkin's lymphoma (NHL), usually at the time of second or subsequent response to conventional-dose therapy. We have undertaken PBSC collection in 57 patients with histologically indolent NHL mobilized with either cyclophosphamide 1.5 g/m2 or the ESHAP regimen, followed by daily G-CSF. Progenitor cell yields were determined by quantification of CD34+ cells and GM-CFC. Twelve patients (21%) failed to achieve the minimum progenitor cell requirements of 1 x 10(6)/kg CD34+ cells or 1 x 10(5)/kg GM-CFC in their pooled harvests and 40 patients (70%) failed to achieve the optimal harvest thresholds of 3.5 x 10(6)/kg CD34+ cells or 3.5 x 10(5)/kg GM-CFC. This high failure rate is significantly higher than that in patients with histologically aggressive NHL or Hodgkin's disease. A multivariate analysis was performed to identify factors contributing to the low stem cell yields in this group. This identified the time interval from the last chemotherapy to the priming chemotherapy as the most important predictive factor. With respect to CD34 and GM-CFC numbers, on the single harvest on the day the white cell count first exceeded 5 x 10(9)/l the P values were 0.0078 and 0.0065, respectively, and for the progenitor cell values on the pooled harvests the P values were 0.004 for CD34+ cells and 0.015 for GM-CFC. Progenitor cell yields may therefore be improved in patients with low grade lymphoma by harvesting at diagnosis if no marrow disease is present, or by delaying mobilization for 6 months post-chemotherapy in patients in first or subsequent remission.     

Combination chemotherapy with mitoguazon, ifosfamide, MTX, etoposide (MIME) and G-CSF can efficiently mobilize PBPC in patients with Hodgkin's and non-Hodgkin's lymphoma

Many centers use CY and G-CSF to mobilize PBPC. In this study we explored whether a standard chemotherapy regimen consisting of mitoguazon, ifosfamide, MTX and etoposide (MIME) combined with G-CSF was capable of mobilizing PBPC in lymphoma patients. Twelve patients with Hodgkin's disease (HD) and 38 patients with non-Hodgkin's lymphoma (NHL) were mobilized with MIME/G-CSF. Most patients were heavily treated with different chemotherapy regimens receiving a median of 11 cycles (range 3 to 20) of chemotherapy prior to mobilization. It was found that the optimal time of PBPC harvest was at days 12 and 13 after initiating the mobilization regimen. The median number of collected CD34+ cells per kg body weight was 7.1 x 10(6) (range 0.5-26.2). More than 2.0 x 10(6) CD34+ cells/kg were achieved in 69% of the patients after one apheresis. When additional cycles of apheresis were done, only 6% failed to harvest this number of CD34+ cells. There was a statistically significant inverse correlation between the number of prior chemotherapy cycles and CD34+ cell yield (P = 0.003). No such association was found between CD34+ cell yield and prior radiotherapy. When MIME/G-CSF was compared with Dexa-BEAM/G-CSF, it was found that MIME/G-CSF tended to be more efficient in mobilizing PBPC in spite of being less myelotoxic. All patients transplanted with MIME/G-CSF mobilized PBPC had fast and sustained engraftment. These results demonstrate that an ordinary salvage chemotherapy regimen, such as MIME combined with G-CSF can be successfully used to mobilize PBPC.     

Ability of early acting cytokines to directly promote survival and suppress apoptosis of human primitive CD34+CD38- bone marrow cells with multilineage potential at the single-cell level: key role of thrombopoietin

Purified primitive progenitor/stem cells from bone marrow represent likely target populations for ex vivo expansion of stem cells to be used in high-dose chemotherapy or gene therapy. Whereas such primitive progenitor cells require combined stimulation by multiple cytokines for growth, some cytokines selectively promote viability rather than growth when acting individually. We investigated here for the first time the direct effects of cytokines on survival of primitive CD34+CD38- human bone marrow progenitor cells at the single-cell level. Interleukin-3 (IL-3) and the ligands for c-kit (KL) and flt3 (FL) had direct and selective viability-promoting effects on a small fraction of CD34+CD38- but not CD34+CD38+ progenitor cells. Interestingly, the recently cloned thrombopoietin (Tpo), although stimulating little growth, kept most CD34+CD38- progenitors viable after prolonged culture, maintaining twofold and fourfold more progenitors viable than KL and IL-3, respectively. A high fraction of these progenitors had a combined myeloid and erythroid differentiation potential, as well as capacity for prolonged production of progenitor cells under stroma-independent conditions. In addition, Tpo promoted viability of CD34+CD38- long-term culture-initiating cells, further supporting the idea that Tpo promotes viability of primitive human progenitor cells. Finally, Tpo suppressed apoptosis of CD34+CD38- cells in culture. Thus, the present studies show a novel effect of Tpo, implicating a potential role of this cytokine in maintaining quiescent primitive human progenitor cells viable.     

Transplantation of human umbilical cord blood cells in macrophage-depleted SCID mice: evidence for accessory cell involvement in expansion of immature CD34+CD38- cells

In vivo expansion and multilineage outgrowth of human immature hematopoietic cell subsets from umbilical cord blood (UCB) were studied by transplantation into hereditary immunodeficient (SCID) mice. The mice were preconditioned with Cl2MDP-liposomes to deplete macrophages and 3.5 Gy total body irradiation (TBI). As measured by immunophenotyping, this procedure resulted in high levels of human CD45(+) cells in SCID mouse bone marrow (BM) 5 weeks after transplantation, similar to the levels of human cells observed in NOD/SCID mice preconditioned with TBI. Grafts containing approximately 10(7) unfractionated cells, approximately 10(5) purified CD34+ cells, or 5 x 10(3) purified CD34+CD38- cells yielded equivalent numbers of human CD45+ cells in the SCID mouse BM, which contained human CD34+ cells, monocytes, granulocytes, erythroid cells, and B lymphocytes at different stages of maturation. Low numbers of human GpA+ erythroid cells and CD41+ platelets were observed in the peripheral blood of engrafted mice. CD34+CD38+ cells (5 x 10(4)/mouse) failed to engraft, whereas CD34- cells (10(7)/mouse) displayed only low levels of chimerism, mainly due to mature T lymphocytes. Transplantation of graded numbers of UCB cells resulted in a proportional increase of the percentages of CD45+ and CD34+ cells produced in SCID mouse BM. In contrast, the number of immature, CD34+CD38- cells produced in vivo showed a second-order relation to CD34+ graft size, and mice engrafted with purified CD34+CD38- grafts produced 10-fold fewer CD34+ cells without detectable CD34+CD38- cells than mice transplanted with equivalent numbers of unfractionated or purified CD34+ cells. These results indicate that SCID repopulating CD34+CD38- cells require CD34+CD38+ accessory cell support for survival and expansion of immature cells, but not for production of mature multilineage progeny in SCID mouse BM. These accessory cells are present in the purified, nonrepopulating CD34+CD38+ subset as was directly proven by the ability of this fraction to restore the maintenance and expansion of immature CD34+CD38- cells in vivo when cotransplanted with purified CD34+CD38- grafts. The possibility to distinguish between maintenance and outgrowth of immature repopulating cells in SCID mice will facilitate further studies on the regulatory functions of accessory cells, growth factors, and other stimuli. Such information will be essential to design efficient stem cell expansion procedures for clinical use.