Essential requirements for setting up a stem cell processing laboratory.

The Graft Processing subcommittee of the Worldwide Network for Blood and Marrow Transplantation wrote this guideline to assist physicians and laboratory technologists with the setting up of a cell processing laboratory (CPL) to support a hematopoietic stem cell transplant program, thereby facilitating the start-up of a transplant program in a new location and improving patient access to transplantation worldwide. This guideline describes the minimal essential features of designing such a laboratory and provides a list of equipment and supply needs and staffing recommendations. It describes the typical scope of services that a CPL is expected to perform, including product testing services, and discusses the basic principles behind the most frequent procedures. Quality management (QM) principles specific to a CPL are also discussed. References to additional guidance documents that are available worldwide to assist with QM and regulatory compliance are also provided.

Transplantation of a fetus with paternal Thy-1(+)CD34(+)cells for chronic granulomatous disease.

A fetus diagnosed with X-linked chronic granulomatous disease was transplanted with Thy-1(+)CD34(+) cells of paternal origin. The transplant was performed at 14 weeks gestation by ultrasound guided injection into the peritoneal cavity. The fetus was delivered at 38 weeks gestation after an otherwise uneventful pregnancy. Umbilical cord blood was collected and used to determine the level of peripheral blood chimerism as well as levels of functional engrafted cells. Flow cytometry was used to detect donor leukocytes identified as HLA-A2(-)B7(+) cells, whereas recipient cells were identified as HLA-A2(+)B7(-) cells. No evidence of donor cell engraftment above a level of 0.01% was found. PCR was used to detect HLA-DRB1*15(+) donor cells among the recipient's HLA-DRB1*15(-) cells, but no engraftment was seen with a sensitivity of 1:1000. The presence of functional, donor-derived neutrophils was assessed by flow cytometry using two different fluorescent dyes that measure reactive oxygen species generated by the phagocyte NADPH oxidase. No evidence of paternal-derived functional neutrophils above a level of 0.15% was observed. Peripheral blood and bone marrow samples were collected at 6 months of age. Neither sample showed engraftment by HLA typing using both flow cytometry and PCR. Functional phagocytes were also not observed. Furthermore, no indication of immunological tolerance specific for the donor cells was indicated by a mixed lymphocyte reaction assay performed at 6 months of age. While there appears to be no engraftment of the donor stem cells, the transplant caused no harm to the fetus and the child was healthy at 6 months of age. Analyses of fetal tissues, obtained from elective abortions, revealed that CD3(+) T cells and CD56(+)CD3(-) NK cells are present in the liver at 8 weeks gestation and in the blood by 9 weeks gestation. The presence of these lymphocytes may contribute to the lack of donor cell engraftment in the human fetus.

Transplantation with selected autologous peripheral blood CD34+Thy1+ hematopoietic stem cells (HSCs) in multiple myeloma: impact of HSC dose on engraftment, safety, and immune reconstitution.

OBJECTIVE: The aims of our study performed in myeloma were to evaluate the performance and the safety of Systemix's high-speed clinical cell sorter, to assess the safety and efficacy of deescalating cell dose cohorts of CD34+Thyl+ hematopoietic stem cells (HSCs) as autologous grafts by determining engraftment, and to assess the residual tumor cell contamination using polymerase chain reaction (PCR) amplification assays of patient-specific complementarity determining region III (CDR III) analysis for residual myeloma cells. MATERIALS AND METHODS: The clinical trial was performed in 31 multiple myeloma patients, using purified human CD34+Thyl+ HSCs mobilized from peripheral blood with cyclosphosphamide and granulocyte-macrophage colony-stimulating factor to support a single transplant after high-dose melphalan 140 mg/m2 alone (cohort 1) and with total body irradiation (TBI) (cohorts 2-5) after an HSC transplant cell dose de-escalation/escalation design. RESULTS: Twenty-three patients were transplanted. Engraftment data in the melphalan + TBI cohorts confirmed that HSC doses above the threshold dose of 0.8 x 10(6) CD34+Thy1+ HSCs/ kg provided prompt engraftment (absolute neutrophil count >0.5 x 10(9)/L day 10; platelet count >50 x 10(9)/L day 13). A higher rate of infections was observed in the early and late follow-up phases than usually reported after CD34+ selected or unselected autologous transplantation, which did not correlate with the CD34+Thy1+ HSC dose infused. Successful PCR for CDR III could only be performed in five patients on initial apheresis product and final CD34+Thy1+ HSC product and showed a median tumor log reduction >3.12. CONCLUSIONS: CD34+Thy1+ HSCs are markedly depleted or free of detectable tumor cells in multiple myeloma and are capable of producing fast and durable hematopoietic reconstitution at cell doses >0.8 x 10(6) CD34+Thy1+ HSCs/kg. The delayed immune reconstitution observed is not different from that described in unselected autologous bone marrow and peripheral blood mononucleated cells transplants in multiple myeloma and may be corrected by addition of T cells either to the graft or to the patient in the posttransplant phase.

Transplantation of highly purified CD34+Thy-1+ hematopoietic stem cells in patients with metastatic breast cancer.

We report here the transplantation of extensively purified "mobilized" peripheral blood CD34Thy-1 hematopoietic stem cells from 22 patients with recurrent or metastatic breast cancer. Patients were mobilized with either high-dose granulocyte colony-stimulating factor (G-CSF) alone or cyclophosphamide plus G-CSE Median purity of the stem cell product at cryopreservation was 95.3% (range, 91.1%-98.3%), and viability was 98.6% (range, 96.5%-100%). After high-dose chemotherapy with carmustine, cisplatin, and cyclophosphamide, CD34+Thy-1 cells at a median dose of 11.3 x 10(5) per kilogram (range, 4.7-163 x 10(5) per kilogram) were infused. No infusion-related toxicity was observed. Neutrophil recovery was prompt, with median absolute neutrophil count >500/microL by day 10 (range, 8-15 days) and >1000/microL by day 11 (range, 8-17 days). Median platelet recovery (>20,000/microL) was observed by day 14 (range, 9-42 days) and >50,000/microL by day 17 (range, 11-49 days). Tumor cell depletion below the limits of detection of a sensitive immunofluorescence-based assay was accomplished in all patients who had detectable tumor cells in apheresis products before processing. Although CD4+ T-cell reconstitution was slow, no unusual infections were observed. Neither early nor late graft failure was observed, and no patient required infusion of unmanipulated backup cells. At a median follow-up of approximately 1.4 years and a maximum follow-up of 2.5 years, 16 of the 22 patients remain alive, with 9 free of disease progression, and have stable blood counts. In summary, highly purified CD34+Thy-1+ cells used as the sole source of the hematopoietic graft result in rapid and sustained hematopoietic engraftment.

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.

Isolation of primitive human bone marrow hematopoietic progenitor cells using Hoechst 33342 and Rhodamine 123.

In addition to possessing multilineage differentiation and self-renewal capabilities, pluripotent hematopoietic stem cells are believed to be mitotically quiescent and metabolically inactive. Fractions of human bone marrow (BM) CD34+ cells can be further enriched for primitive hematopoietic progenitor cells (HPC) by using a number of cell-surface markers. All of these fractions, however, contain cells that are still heterogeneous as far as their metabolic and mitotic activities are concerned. We therefore used Hoechst 33342 (Hst) to identify quiescent cells and Rhodamine 123 (Rh123) to identify metabolically inactive cells. CD34+HstdimRh123dim (CD34+d/d) and CD34+HstbrightRh123bright (CD34+b/b) cells were isolated by flow cytometry to examine the hematopoietic functions of mitotically and metabolically homogeneous progenitors. Cell-cycle status, progenitor cell content, maintenance of in vitro hematopoiesis, and long-term hematopoietic culture-initiating cell (LTHC-IC) content of CD34+d/d and CD34+b/b cells were compared with CD34+HLA-DR- cells, a well-defined phenotype of primitive HPC. Whereas 99.2 +/- 0.5% of freshly isolated CD34+d/d cells were in G0/G1 phase of the cell cycle, only 74.4 +/- 11.5% of CD34+b/b and 75.6 +/- 1.1% of CD34+HLA-DR- cells were in G0/G1. The number of multipotential progenitors (colony-forming units-granulocyte/erythroid/ macrophage/megakaryocyte [CFU-GEMM]) detected in CD34+d/d cells was twice that observed in CD34+HLA-DR- cells and eight times that in CD34+b/b cells. In stromal cell-free long-term cultures maintained for 10 weeks, production of assayable progenitors in cultures initiated with CD34+d/d cells exceeded that detected in CD34+HLA-DR- cultures by more than three-fold. Only in CD34+d/d cultures were high proliferative potential colony-forming cell (HPP-CFC)-derived colonies detected over a period of 6 weeks. Limiting dilution analysis revealed that the frequency of LTHC-IC was highest among CD34+d/d cells (7.2 +/- 3.3%), followed by a frequency of 4.5 +/- 4.8% for CD34+HLA-DR- cells and 2.2 +/- 3.5% for CD34+b/b cells. The primitive nature of HPC identified by CD34, Hst, and Rh123 was confirmed by the ability of as few as 200 murine marrow cells isolated by this technique to radioprotect and fully reconstitute lethally irradiated recipients. These results indicate that Hst and Rh123 staining can be used in combination with CD34 immunofluorescence to isolate a quiescent subpopulation of human primitive hematopoietic progenitor cells. Cells isolated by this technique appear to have functional properties associated with stem cells, suggesting that they may be ideal candidates for studies requiring primitive HPC, such as ex vivo expansion and somatic gene therapy.

Retroviral mediated gene transfer in chronic myelogenous leukaemia.

Gene therapy for chronic myelogenous leukaemia (CML) may provide a therapeutic option for patients who are ineligible for bone marrow transplantation. To determine the feasibility of such an approach we evaluated the transduction efficiency of CML progenitor colonies from seven patients in chronic phase. Vector transduction was optimized using the CML-derived K562 cell line and applied to CML mononuclear cells. After vector exposure, optimal gene transfer was noted when CML mononuclear cell cultures contained stem cell factor, IL-3, GM-CSF and erythropoietin. The addition of IL-6 to this combination decreased transduction efficiency. Using these conditions, 20.4% +/- 2.4 (SE) of erythroid colonies (CFU-GEMM and BFU-E) and 20.2% +/- 4.7 of CFU-GM colonies were G418 resistant. This compares with a transduction efficiency of 5.9% +/- 1.1 and 6.4% +/- 1.5, respectively, for erythroid and CFU-GM colonies using marrow obtained from normal donors. Only a modest increase in gene transfer was noted when CML cells were stimulated with cytokines for the 24 h preceding vector exposure. Vector DNA in colonies expressing the BCR/ABL transcript was documented by performing PCR analysis on individual colonies. The relatively high gene transfer rate in CML suggests that this disease might be very suitable for gene therapy.

Persistence of human multilineage, self-renewing lymphohematopoietic stem cells in chimeric sheep.

We have previously reported the ability of uncharacterized human bone marrow (BM) cells to engraft into preimmune fetal sheep, thereby creating sheep-human chimera suitable for in vivo examination of the properties of human hematopoietic stem cells (HSC). Adult human bone marrow CD34+ HLA-DR- cells have been extensively characterized in vitro and have been demonstrated to contain a number of primitive hematopoietic progenitor cells (PHPC). However, the capacity of such highly purified populations of human marrow CD34+ HLA-DR- cells to undergo in vivo self-renewal and multipotential lymphohematopoietic differentiation has not been previously demonstrated. To achieve that, human CD34+ HLA-DR- cells were transplanted in utero into immunoincompetent fetal sheep to investigate the BM-populating potential of these cells. Long-term chimerism, sustained human hematopoiesis, and expression of human cells belonging to all human blood cell lineages were demonstrated in two animals for more than 7 months' posttransplantation. Chimeric BM contained erythroid, granulocytic/monocytic, and megakaryocytic hematopoietic progenitor cells, as well as the primitive high proliferative potential colony-forming cell (HPP-CFC). Under a variety of in vitro experimental conditions, chimeric BM cells gave rise to human T cells expressing T-lymphocyte-specific markers, human natural killer (NK) cells, and human IgG-producing B cells. In vivo expansion and possibly self-renewal of transplanted PHPC was confirmed by the detection in chimeric BM 130 days' posttransplantation of CD34+ HLA-DR- cells, the phenotype of human cells constituting the stem-cell graft. These studies demonstrate not only the BM-populating capacity, multipotential differentiation, and most likely self-renewal capabilities of human CD34+ HLA-DR- cells, but also that this BM population contains human HSC. Furthermore, it appears that this animal model of xenogeneic stem-cell transplantation is extremely useful for in vivo examination of human hematopoiesis and the behavioral and functional characteristics of human HSC.

Long-term generation and expansion of human primitive hematopoietic progenitor cells in vitro.

Although sustained production of committed human hematopoietic progenitor cells in long-term bone marrow cultures (LTBMC) is well documented, evidence for the generation and expansion of human primitive hematopoietic progenitor cells (PHPC) in such cultures is lacking. For that purpose, we attempted to determine if the human high proliferative potential colony-forming cell (HPP-CFC), a primitive hematopoietic marrow progenitor cell, is capable of generation and expansion in vitro. To that effect, stromal cell-free LTBMC were initiated with CD34+ HLA-DR-CD15- rhodamine 123dull bone marrow cells and were maintained with repeated addition of c-kit ligand and a synthetic interleukin-3/granulocyte-macrophage colony-stimulating factor fusion protein. By day 21 of LTBMC, a greater than twofold increase in the number of assayable HPP-CFC was detected. Furthermore, the production of HPP-CFC in LTBMC continued for up to 4 weeks, resulting in a 5.5-fold increase in HPP-CFC numbers. Weekly phenotypic analyses of cells harvested from LTBMC showed that the number of CD34+ HLA-DR- cells increased from 10(4) on day 0 to 56 CD34+ HLA-DR- cells increased from 10(4) on day 0 to 56 x 10(4) by day 21. To examine further the nature of the in vitro HPP-CFC expansion, individual HPP-CFC colonies were serially cloned. Secondary cloning of individual, day 28 primary HPP-CFC indicated that 46% of these colonies formed an average of nine secondary colony-forming unit--granulocyte-macrophage (CFU-GM)--derived colonies, whereas 43% of primary HPP-CFC gave rise to between one and six secondary HPP-CFC colonies and 6 to 26 CFU-GM. These data show that CD34+ HLA-DR- CD15- rhodamine 123dull cells represent a fraction of human bone marrow highly enriched for HPP-CFC and that based on their regeneration and proliferative capacities, a hierarchy of HPP-CFC exists. Furthermore, these studies indicate that in the presence of appropriate cytokine stimulation, it is possible to expand the number of PHPC in vitro.

Identification of BCR/ABL-negative primitive hematopoietic progenitor cells within chronic myeloid leukemia marrow.

Chronic myeloid leukemia (CML) is a malignant disorder of the hematopoietic stem cell. It has been shown that normal stem cells coexist with malignant stem cells in the bone marrow of patients with chronic-phase CML. To characterize the primitive hematopoietic progenitor cells within CML marrow, CD34+DR- and CD34+DR+ cells were isolated using centrifugal elutriation, monoclonal antibody labeling, and flow cytometric cell sorting. Polymerase chain reaction analysis of RNA samples from these CD34+ subpopulations was used to detect the presence of the BCR/ABL translocation characteristic of CML. The CD34+DR+ subpopulation contained BCR/ABL(+) cells in 11 of 12 marrow samples studied, whereas the CD34+DR- subpopulation contained BCR/ABL(+) cells in 6 of 9 CML marrow specimens. These cell populations were assayed for hematopoietic progenitor cells, and individual hematopoietic colonies were analyzed by PCR for their BCR/ABL status. Results from six patients showed that nearly half of the myeloid colonies cloned from CD34+DR- cells were BCR/ABL(+), although the CD34+DR- subpopulation contained significantly fewer BCR/ABL(+) progenitor cells than either low-density bone marrow (LDBM) or the CD34+DR+ fraction. These CD34+ cells were also used to establish stromal cell-free long-term bone marrow cultures to assess the BCR/ABL status of hematopoietic stem cells within these CML marrow populations. After 28 days in culture, three of five cultures initiated with CD34+DR- cells produced BCR/ABL(-) cells. By contrast, only one of eight cultures initiated with CD34+DR+ cells were BCR/ABL(-) after 28 days. These results indicate that the CD34+DR- subpopulation of CML marrow still contains leukemic progenitor cells, although to a lesser extent than either LDBM or CD34+DR+ cells.

Human interleukin (IL)-9 specifically stimulates proliferation of CD34+++DR+CD33- erythroid progenitors in normal human bone marrow in the absence of serum.

The cDNA encoding human interleukin (IL)-9 has recently been cloned and the recombinant molecule found to enhance erythroid colony formation in vitro by bone marrow, peripheral blood, and cord blood cells. In our present report, recombinant human (rhu) IL-9 was evaluated, alone and in combination with other cytokines, for its effect on colony formation by erythroid progenitor (erythroid burst-forming units, BFU-E) and precursor (erythroid colony-forming units, CFU-E) cells in low density (LD), nonadherent LD density T-lymphocyte-depleted (NALT-), and immunofluorescence-sorted CD34+++DR+ and CD34+++DR+CD33- cells from normal human bone marrow. When highly enriched CD34+++DR+ and CD34+++DR+CD33- cells were plated at 200 and 100 cells/ml in the presence of 5% (vol/vol) 5637-cell-conditioned medium and erythropoietin (Epo) under serum-containing conditions, 46 and 51 day-14 BFU-E were observed, respectively. The enhancing effect of rhuIL-9 was similar to that of 5637 CM on colony formation by Epo-dependent BFU-E and CFU-E in these enriched sorted CD34+++DR+ and CD34+++DR+CD33- cells under serum-containing and serum-depleted culture conditions. No significant synergistic or additive effect of rhuIL-9 was noted when used in conjunction with rhu interleukin 3 (rhuIL-3), rhu interleukin 6 (rhuIL-6), and/or rhu granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) under the same culture conditions. The cloning enhancing effect elicited by human IL-9 is Epo dependent, although IL-9 alone sustains the survival of erythroid progenitor cells in vitro, as assessed by delayed additions of Epo to the cultures. The ability of human IL-9 to stimulate BFU-E and CFU-E colony formation using low numbers of highly enriched progenitor cells in serum-depleted conditions demonstrates the direct effect of IL-9 on erythroid progenitors and implicates its potential role in the enhancement of erythropoiesis.

Sustained human hematopoiesis in sheep transplanted in utero during early gestation with fractionated adult human bone marrow cells.

Sheep were transplanted in utero during early gestation with subpopulations of adult human bone marrow (BM) cells enriched for human progenitor and hematopoietic stem cells (HSC). Chimerism was documented in three of seven transplanted fetuses using monoclonal antibodies against human-specific hematopoietic cell lineages and/or cytogenetic analysis of BM and peripheral blood cells of recipients. Only chimeric sheep BM cells expressing CD45 (6.0% of total BM cells) formed human hematopoietic colonies in response to human recombinant cytokines as determined by cytogenetic analysis. Sorted CD45+ BM cells developed human T-cell colonies containing CD3+, CD4+, and CD8+ cells. DNA from chimeric BM cells obtained 3 months after birth displayed a finger printing pattern identical to that of DNA from the human donor of the HSC graft. These studies indicate that first trimester sheep fetuses are tolerant of adult human HSC grafts, thus permitting the creation of xenogeneic chimera expressing human myeloid and lymphoid lineages. The present findings also suggest that HSC grafts from immunologically competent, HLA-mismatched adult donors may be useful for correcting human genetic diseases in utero during early gestation.

Role of c-kit ligand in the expansion of human hematopoietic progenitor cells.

To test the hypothesis that the c-kit ligand plays an important role in the regulation of early events occurring during human hematopoiesis, we determined the effect of a recombinant form of c-kit ligand, termed mast cell growth factor (MGF), on the high-proliferative potential colony-forming cell (HPP-CFC) and the cell responsible for initiating long-term hematopoiesis in vitro (LTBMIC). MGF alone did not promote HPP-CFC colony formation by CD34+ DR- CD15- marrow cells, but synergistically augmented the ability of a combination of granulocyte-monocyte colony-stimulating factor (GM-CSF) interleukin (IL)-3 and a recombinant GM-CSF/IL-3 fusion protein (FP) to promote the formation of HPP-CFC-derived colonies. MGF had a similarly profound effect on in vitro long-term hematopoiesis. Repeated additions of IL-3, GM-CSF, or FP alone to CD34+ DR- CD15- marrow cells in a stromal cell-free culture system increased cell numbers 10(3)-fold by day 56 of long-term bone marrow culture (LTBMC), while combinations of MGF with IL-3 or FP yielded 10(4)- and 10(5)-fold expansion of cell numbers. Expansion of the number of assayable colony-forming unit-granulocyte-monocyte (CFU-GM) generated during LTBMC was also markedly enhanced when MGF was added in combination with IL-3 or FP. In addition, MGF, IL-3, and FP individually led to a twofold to threefold increase in HPP-CFC numbers after 14 to 21 days of LTBMC. Furthermore, the effects of these cytokines on HPP-CFC expansion during LTBMC were additive. Throughout the LTBMC, cells receiving MGF possessed a higher cloning efficiency than those receiving IL-3, GM-CSF, or FP alone. These data indicate that the c-kit ligand synergistically interacts with a number of cytokines to directly augment the proliferative capacity of primitive human hematopoietic progenitor cells.

Incidence of HIV infection in monocyte subpopulations characterized by CD4 and HLA-DR surface density.

OBJECTIVE: The purpose of this study was to determine any correlation between the expression of CD4 antigen on the surface of monocytes, and the frequency with which these cells are infected with HIV. DESIGN: CD4 surface expression on monocytes is significantly less than that expressed on CD4+ lymphocytes. Nevertheless, all monocytes express the HIV CD4 receptor and infected individuals have a significant decrease in the number of monocytes that express a higher density of CD4 surface fluorescence. METHODS: Three-color flow cytometric analysis was used to characterize monocyte-enriched peripheral blood mononuclear cells (PBMC) in terms of surface expression of CD4, CD14 (macrophage antigen), and class II major histocompatibility antigen (HLA-DR). HLA-DR+ monocytes from HIV-positive individuals were sorted into two subpopulations based on either 'bright' or 'dim' CD4 surface expression. A polymerase chain reaction (PCR) assay was used to detect the presence of proviral HIV sequences within the DNA from 10(5) cells from each sorted population. RESULTS: Post-sort analysis revealed that the dim CD4+ monocyte subset expressed dim HLA-DR surface antigen, while the bright CD4+ monocyte subset contained both bright and dim HLA-DR+ cells. PCR results showed that four out of eight dim CD4+ monocyte subsets contained proviral HIV DNA, compared with one out of eight bright CD4+ monocyte subsets.

Relationship between cytokine-dependent cell cycle progression and MHC class II antigen expression by human CD34+ HLA-DR- bone marrow cells.

Human CD34+ HLA-DR- bone marrow cells constitute a phenotypically homogeneous population of quiescent cells. More than 97% of CD34+ HLA-DR- cells reside in the G0/G1 phase of the cell cycle. The in vitro effects of two cytokines, IL-1 alpha and IL-3, alone or in combination, on the viability, cell cycle status and acquisition of HLA-DR by this cell population were examined. Cell viability was preserved in cultures receiving cytokines, but declined steadily in cultures deprived of exogenous IL. Over a period of 4 days, IL-3 progressively induced the expression of HLA-DR although driving corresponding numbers of cells into S and G2 + M. Although IL-1 alpha induced the expression of HLA-DR, it was not as effective as IL-3 in promoting the exit of these cells from G0/G1. Combinations of IL-1 alpha and IL-3, however, exerted an even greater effect on promoting both HLA-DR expression and entry of cells into active phases of the cell cycle. Simultaneous measurement of HLA-DR expression and cell cycle status in response to IL-1 alpha and IL-3 indicated that the majority of de novo expression of HLA-DR occurred in cells that remained in G0/G1. CD34+ HLA-DR- cells cultured with IL-1 alpha and IL-3 but arrested in G0/G1 by hydroxyurea were still capable of expressing HLA-DR, demonstrating that the acquisition of HLA-DR was independent of the entry of these cells into active phases of the cell cycle. These data indicate that the survival, HLA-DR expression, and cell cycle status of human CD34+ HLA-DR- bone marrow cells are governed by regulatory cytokines such as IL-1 alpha and IL-3. In addition, the entry of these cells into active phases of the cell cycle does not seem to be a prerequisite for the expression of HLA-DR, nor does it seem that the acquisition of HLA-DR by hematopoietic progenitor cells is a marker of cells entering the S phase of the cell cycle.

Influence of combinations of cytokines on proliferation of isolated single cell-sorted human bone marrow hematopoietic progenitor cells in the absence and presence of serum.

Human mast cell growth factor (MGF, a c-kit ligand) and colony stimulating factors (Epo, GM-CSF, G-CSF, IL-3) were assessed in the absence or presence of serum for stimulation in semi-solid medium of single CD34 , CD34 HLA-DR+, or CD34 HLA-DR+CD33- cells sorted per microtiter well. The % of wells containing CFU-GM and erythroid containing (BFU-E and CFU-GEMM) colonies increased in proportion to the number of cytokines added. In the presence of serum, 1, to 4 cytokine combinations resulted in respective increases in cloning efficiencies of 10 to 21.0, 19.5 to 31.5, 35.8 to 42.9, and 46.3 to 60.0%. MGF had little effect by itself, but did act in combination with CSFs to enhance numbers and size of the colonies from isolated single cells. High cloning efficiencies were also obtained in the absence of serum when multiple cytokines were used. The results demonstrate that MGF and CSFs can act directly on the proliferation of single hematopoietic progenitor cells in the absence of accessory cells and serum.

Role of cytokines in sustaining long-term human megakaryocytopoiesis in vitro.

An in vitro liquid suspension culture system was used to determine the role of cytokines in sustaining long-term human megakaryocytopoiesis. Bone marrow cells expressing CD34 but not HLA-DR (CD34+DR-) were used as the inoculum of cells to initiate long-term bone marrow cultures (LTBMC). CD34+DR- cells (5 x 10(3)/mL) initially contained 0.0 +/- 0.0 assayable colony-forming unit-megakaryocytes (CFU-MK), 6.2 +/- 0.4 assayable burst-forming unit-megakaryocytes (BFU-MK), and 0.0 +/- 0.0 megakaryocytes (MK). LTBMCs were recharged every 48 hours with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 alpha (IL-1 alpha), IL-3, and/or IL-6, alone or in combination. LTBMCs were demidepopulated weekly or biweekly, the number of cells and MK enumerated, and then assayed for CFU-MK and BFU-MK. LTBMCs receiving no cytokine(s) contained no assayable CFU-MK or BFU-MK and no observable MK. LTBMCs receiving GM-CSF, IL-1 alpha, and/or IL-3 contained assayable CFU-MK and MK but no BFU-MK for 10 weeks of culture. The effects of GM-CSF and IL-3, IL-1 alpha and IL-3, but not GM-CSF and IL-1 alpha were additive with regards to their ability to augment the numbers of assayable CFU-MK during LTBMC. LTBMCs supplemented with IL-6 contained modest numbers of assayable CFU-MK for only 4 weeks; this effect was not additive to that of GM-CSF, IL-1 alpha, or IL-3. The addition of GM-CSF, IL-1 alpha, and IL-3 alone or in combination each led to the appearance of significant numbers of MKs during LTBMC. By contrast, IL-6 supplemented cultures contained relatively few MK. These studies suggest that CD34+DR- cells are capable of initiating long-term megakaryocytopoiesis in vitro and that a hierarchy of cytokines exists capable of sustaining this process.

Simultaneous use of rhodamine 123, phycoerythrin, Texas red, and allophycocyanin for the isolation of human hematopoietic progenitor cells.

The supravital, mitochondrial specific dye Rhodamine 123 (R123) was used in conjunction with three monoclonal antibodies to isolate a population of human bone marrow (BM) cells enriched for hematopoietic progenitor cells. BM cells stained with phycoerythrin-HLA-DR, Texas red-CD34, allophycocyanin-CD15, and R123 were fractionated using four-color immunofluorescence cell sorting. Cells expressing CD34 but not HLA-DR and CD15 (CD34+ HLA-DR- CD15-) were subdivided according to their reactivity with R123 into quiescent, R123 dull (R+) or cycling, R123 bright (R++) subpopulations. Morphological analysis and hematopoietic progenitor cell assays indicated that CD34+ HLA-DR- CD15- R+ cells contained larger numbers of blast cells and colony forming units than CD34+ HLA-DR- CD15- R++ cells. The flow cytometer settings used to accommodate the detection of the R123 fluorescence in combination with that of three other fluorochromes are described.

Human CD34+ HLA-DR- bone marrow cells contain progenitor cells capable of self-renewal, multilineage differentiation, and long-term in vitro hematopoiesis.

Human bone marrow cells expressing CD34 but not HLA-DR were isolated by immunofluorescence flow cytometric cell sorting. These cells contained a hematopoietic cell (CFU-B1) capable of producing, in an in vitro semisolid culture system, blast-cell-containing colonies, which possessed the capacity for self-renewal and commitment to multipotential differentiation. In addition, CD34+ HLA-DR- marrow cells contained primitive megakaryocyte progenitor cells, the burst-forming unit-megakaryocyte (BFU-MK). A subset of CD34+ HLA-DR- marrow cells lacking the expression of CD15 and CD71 was obtained by flow cytometric cell sorting and was capable of sustaining in vitro hematopoiesis in suspension culture for up to 8 weeks in the absence of a preestablished adherent marrow cell layer. The combination of IL-3 + IL-1 alpha and IL-3 + IL-6 sustained proliferation of these cells for 8 weeks, induced maximal cellular expansion, and increased the numbers of assayable progenitor cells. These studies demonstrate that human CD34+ HLA-DR- marrow cells and their subsets contain primitive multipotential hematopoietic cells capable of self-renewal and of differentiation into multiple hematopoietic lineages.