Selected Bone Marrow Cells Research Articles

Day +60 WT1 assessment on CD34 selected bone marrow better predicts relapse and mortality after allogeneic stem cell transplantation in acute myeloid leukemia patients.

The aim of this study was to evaluate the role of WT1 expression after allogeneic stem cell transplantation (alloHSCT) in patients with acute myeloid leukemia (AML). We studied WT1 expression in bone marrow cells from 50 patients in complete remission on day +60 after transplant. WT1 was assessed on unfractionated bone marrow mononuclear cells (MNC) and on CD34+ selected cells (CD34+). A ROC curve analysis identified 800 WT1 copies on CD34+ selected cells, as the best cut-off predicting relapse (AUC 0.842, p=0.0006, 85.7% sensitivity and 81.6% specificity) and 100 copies in MNC (AUC 0.819, p=0.007, 83.3% sensitivity and 88.2% specificity). Using the 800 WT1 copy cut off in CD34+ cells, the 2 year cumulative incidence of relapse was 12% vs 38% (p=0.005), and 2 year survival 88% vs 55% (p=0.02). Using the 100 WT1 copy cut off in unfractionated MNC, the 2 year cumulative incidence of relapse 13% vs 44% (p=0.01) and the 2 year survival 88% vs 55% (p=0.08). In a multivariate Cox analysis WT1 expression in CD34 cells proved to highly predictive of relapse (p=0.004); also WT1 expression on unfractionated cells predicted relapse (p=0.03). In conclusion, day-60 WT1 expression after allogeneic HSCT is a significant predictor of relapse, particularly when tested on CD34+ selected bone marrow cells.

Characterization of the Mutational Landscape of Multiple Myeloma Using Comprehensive Genomic Profiling

Introduction:Multiple myeloma (MM) is a neoplastic disease of the bone marrow characterized by a malignant transformation of plasma cells. Many patients relapse after initial treatment and require additional therapies. Impaired cell cycle regulation and DNA repair mechanisms as well as exposure to genotoxic drugs leads to accumulation of genomic alterations with progressive disease. Pressure from antineoplastic agents, including novel agents, eventually leads to the selection of resistant clones. Assessing acquired somatic mutations in MM patients can identify key genomic drivers and guide the development of a rational, individualized therapy plan for each patient with advanced disease. Here we report on the mutational landscape of cancer-associated genes in 214 patients who underwent comprehensive genomic profiling.Methods:Review of this data was approved by the UAMS institutional review board. DNA and RNA were extracted from CD138+ selected cells from bone marrow aspirates. Adaptor ligated sequencing libraries from extracted nucleic acids were captured by solution hybridization using bait sets targeting 405 cancer-related and 265 frequently rearranged genes (FoundationOne Heme®; Foundation Medicine ). For samples with low cell yield only the DNA portion was performed. All samples were sequenced in a CLIA-certified, CAP-accredited laboratory to an average depth >500x.ResultsWe identified 147 clinically relevant alterations with an average of 3 alterations per patient ranging from 1 to 8. The most frequently altered genes were KRAS (29% of cases), NRAS (23%), TP53 (19%), RB1 (10%), BRAF (8%), TRAF3(8%), CDKN2C (7%), DNMT3A (5%), NF1, FAF1 and TET2 (4% each). While RAS, RAF, RB1 and TP53 mutations are also found in previously untreated patients, albeit in lower frequencies, mutations of DNTM3A and TET2 are rarely reported in the early phase of the disease, arguing for the accumulation of genomic alterations over time. We found concomitant alterations in KRAS and BRAF in 5, KRAS and NRAS in 3, and NRAS and BRAF in 2 patients. The vast majority of RAS alterations occurred at hotspots resulting in activating alterations at codons 12, 13 or 61 with mutant allele frequencies ranging from 0.01 to 0.92 with an average of 0.30. In the 17 patients with BRAF alterations the hotspot mutation V600E was found in 7 with mutant allele frequencies ranging from 0.01 to 0.48 with an average of 0.32. Overall the MAPK pathway was affected in 128 of 214 patients. 61 patients had alterations of genes associated with DNA damage repair. Among the 10 patients with DNMT3A alterations 2 also had alterations of TET2 suggesting significant epigenetic deregulation in a subset of patients. Data on subclonal structure and correlation of mutation status with paired gene expression profiles will be presented as well, as will be selected responses of patients treated on the basis of these results.ConclusionSubjecting CD138 selected bone marrow cells to comprehensive genomic profiling allows for the identification of clinically relevant alterations, which deregulate critical pathways in multiple myeloma. Small molecule inhibitors that target key genes in these affected pathways (MEK, BRAF) have recently been approved for therapy in other cancers or are being actively developed (PI3K, AKT, PARP). This comprehensive genomic characterization allows rational development of individualized clinical strategies using molecular targets for MM patients who are refractory to standard of care therapies. DisclosuresWalker:Onyx Pharmaceuticals: Consultancy, Honoraria. van Rhee:Senesco: PI Other. Zangari:Norvartis: Membership on an entity’s Board of Directors or advisory committees; Onyx: Research Funding; Millennium: Research Funding. Ali:Foundation Medicine, Inc.: Employment, Equity Ownership. Stephens:Foundation Medicine: Employment, Equity Ownership. Miller:Foundation Medicine, Inc: Employment. Morgan:Celgene Corp: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees; Janssen: Membership on an entity’s Board of Directors or advisory committees; Myeloma UK: Membership on an entity’s Board of Directors or advisory committees; International Myeloma Foundation: Membership on an entity’s Board of Directors or advisory committees; The Binding Site: Membership on an entity’s Board of Directors or advisory committees; MMRF: Membership on an entity’s Board of Directors or advisory committees. Barlogie:Celgene: Consultancy, Patents & Royalties, Research Funding; Millenium: Consultancy, Patents & Royalties, Research Funding.

MicroRNA-21 and −155 Are Induced by a Widely Expressed Mutation in MyD88 (L265P) in Waldenstrom’s Macroglobulinemia,

Abstract 3957 Introduction:MicroRNA dysregulation has been described in Waldenstrom’s Macroglobulinemia (WM), an indolent non-Hodgkin’s lymphoma characterized by the accumulation of IgM secreting lymphoplasmacytic cells (LPC). Whether MicroRNA dysregulation represents a primary oncogenic event, is reactive to an oncogenic event, or is related to the stage of B-cell differentiation remains to be clarified. As part of these efforts, we sought to delineate aberrant MicroRNAs which emerge by direct comparison of WM LPC with memory B-cells, from wherein the WM clone is believed to have emerged. Further to these efforts, we also sought to clarify whether MicroRNA dysregulation is related to the presence of a somatic mutation in MYD88 (L265P), a widely expressed mutation in WM patients, which also induces NF-kB and STAT3 activation via IRAK 1/4 (Nature 2011, 470:115–119). Patients and Methods:CD19+ selected bone marrow cells from WM patients were isolated by immunomagnetic sorting. Healthy donor B-cells (CD19+) were isolated from peripheral blood, and further sorted using a memory B-cell (CD19+ CD27+) isolation kit (Miltenyi, Auburn CA). MicroRNA profiling was performed using Taqman low-density arrays. Taqman stem-loop Real-Time PCR was used for validation of MicroRNA changes. MYD88 L265P expressing BCWM.1 and MWCL-1 cells were used for lentiviral transduction experiments, and inhibitory studies using an IRAK 1/4 kinase inhibitor (407601, EMD, Gibbstown, USA) in order to assess changes in MicroRNA expression. STAT3 and IKKα phosphorylation were detected by Western blot using phospho-specific antibodies. Results:MicroRNA profiling was performed using bone marrow LPC from 11 WM patients, and compared to total B-cells, and selected memory B-cells from 7 healthy donors. Real-time PCR was also performed in 27 additional patients for a total of 38 patients which showed that MicroRNA-21, −155 and −29c were increased, and MicroRNA-9*, −27b, −126, and −145 were decreased when WM LPC were directly compared with total healthy donor CD19+ cells. When WM LPC were directly compared to healthy donor memory B-cells, only MicroRNA-21 and −155 remained significantly higher in WM LPC. To investigate whether MicroRNA-21 and −155 are impacted by the MYD88 L265P mutation, we next performed lentiviral knock-down experiments in BCWM.1 and MWCL-1 cells. Levels of MicroRNA-21 and −155 decreased following knockdown of MYD88, whereas over-expression of MYD88 L265P led to enhanced Micro-RNA 21 expression. In addition, MicroRNA-21 but not −155 decreased following treatment of BCWM.1 and MWCL-1 cells with an IRAK 1/4 kinase inhibitor potentially signifying differences in downstream activation of MicroRNA-21 and −155 by MYD88 L265P. Conclusion:Differences in MicroRNA expression vary based on which population of healthy donor B-cells are compared to WM LPC. Direct comparison of WM LPC to healthy donor memory B-cells reveals differences in MicroRNA-21, and −155. Importantly, MicroRNA-21 and −155 are induced by the MYD88 L265P mutation through distinct signaling pathways. The data suggest a reactive role for MicroRNA-21 and −155 in response to the MYD88 L265P mutation in WM. Disclosures:No relevant conflicts of interest to declare.

Cotransplanted Bone Marrow Derived Mesenchymal Stem Cells (MSC) Enhanced Engraftment of Hematopoietic Stem Cells in a MSC-dose Dependent Manner in NOD/SCID Mice

Transplantation of marrow-derived mesenchymal stem cells (MSCs), expanded by culture in addition to whole bone marrow, has been shown to enhance engraftment of human hematopoietic stem cells (HSCs). Our hypothesis was that there might be an optimum ratio range that could enhance engraftment. We examined the percent donor chimerism according to the ratio of HSCs to MSCs in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. We tested a series of ratios of co-transplanted CD34+-selected bone marrow cells, and marrow-derived MSCs into sublethally irradiated NOD/SCID mice. In all experiments, 1×105 bone marrow derived human CD34+ cells were administered to each mouse and human MSCs from different donors were infused concomitantly. We repeated the procedure three times and evaluated engraftment with flow cytometry four weeks after each transplantation. Serial ratios of HSCs to MSCs were 1:0, 1:1, 1:2 and 1:4, in the first experiment, 1:0, 1:1, 1:2, 1:4 and 1:8 in the second and 1:0, 1:1, 1:4, 1:8 and 1:16 in the third. Cotransplantation of HSCs and MSCs enhanced engraftment as the dose of MSCs increased. Our results suggest that the optimal ratio of HSCs and MSCs for cotransplantation might be in the range of 1:8-1:16; whereas, an excessive dose of MSCs might decrease engraftment efficiency.

Abnormal Expression of the Plasma Cell Differentiation Factor X-Box Protein 1 (Xbp-1) in Waldenstrom's Macroglobulinemia.

INTRODUCTION: Xbp-1 is a ubiquitously expressed basic leucine zipper protein which serves as key transcription factor for plasma cell differentiation and immunoglobulin production. XBP-1 mRNA undergoes splicing at an IRE-1a specific cleavage site to produce a spliced form (Xbp-1s) which due to a frame shift results in a more stable and potent transcription factor than the unspliced form (Xbp-1us). Previous observations demonstrated that Xbp-1 was highly expressed in multiple myeloma (MM), though its expression in other B-cell disorders including Waldenstrom's macroglobulinemia (WM) remains to be clarified.METHODOLOGY: In this study, we investigated the different forms of Xbp-1 in CD19+ selected bone marrow (BM) cells from 61 patients with the consensus panel definition of WM using semi-quantitative PCR analysis. CD19+ selected BM cells from 6 healthy donors, and CD138+ selected BM cells from 4 MM patients were used as controls. All RT-PCR results were normalized to b-actin levels. Sequencing of Xbp-1 in CD19+ selected LPC was also performed for 20 WM patients.RESULTS: In 9/61 (15%) WM patients, Xbp-1 transcripts were undetectable. Among WM patients expressing Xbp-1, as well as all MM patients evaluated, higher levels of XBP-1us were observed in comparison to normal healthy donors (p=0.001). Decreased XBP-1s transcript levels were also observed among WM and MM patients versus healthy donors, but did not reach statistical significance. Sequence analysis of Xbp1 in CD19+ selected BM LPC demonstrated variants 10/20 WM patients in exon 1 that are currently under investigation.CONCLUSIONS: Abnormal expression of Xbp-1 is common in patients with WM, and includes loss of expression, and aberrations in splice patterns. The genetic basis for these findings is under investigation.

Gene therapy of RAG-2−/− mice: sustained correction of the immunodeficiency

Patients with mutations of either RAG-1 or RAG-2 genes suffer from severe combined immunodeficiency (SCID) characterized by the lack of T and B lymphocytes. The only curative treatment today consists of hematopoietic stem cell (HSC) transplantation, which is only partially successful in the absence of an HLA genoidentical donor, thus justifying research to find an alternative therapeutic approach. To this end, RAG-2-deficient mice were used to test whether retrovirally mediated ex vivo gene transfer into HSCs could provide long-term correction of the immunologic deficiency. Murine RAG-2-/-Sca-1(+) selected bone marrow cells were transduced with a modified Moloney leukemia virus (MLV)-based MND (myeloproliferative sarcoma virus enhancer, negative control region deleted, dl587rev primer-binding site substituted) retroviral vector containing the RAG-2 cDNA and transplanted into RAG-2-/- sublethally irradiated mice (3Gy). Two months later, T- and B-cell development was achieved in all mice. Diverse repertoire of T cells as well as proliferative capacity in the presence of mitogens, allogeneic cells, and keyhole limpet hemocyanin (KLH) were shown. B-cell function as shown by serum Ig levels and antibody response to a challenge by KLH also developed. Lymphoid subsets and function were shown to be stable over a one-year period without evidence of any detectable toxicity. Noteworthy, a selective advantage for transduced lymphoid cells was evidenced by comparative provirus quantification in lymphoid and myeloid lineages. Altogether, this study demonstrates the efficiency of ex vivo RAG-2 gene transfer in HSCs to correct the immune deficiency of RAG-2-/- mice, constituting a significant step toward clinical application.

SUCCESSFUL TRANSPLANTATION OF HAPLOIDENTICAL CD34 + SELECTED BONE MARROW CELLS FOR AN INFANTILE CASE OF SEVERE COMBINED IMMUNODEFICIENCY WITH ASPERGILLUS PNEUMONIA

A 5-month-old boy with X-linked severe combined immunodeficiency (SCID) and aspergillus pneumonia was successfully transplanted. Before and during transplantation, the patient received O 2 administration, systemic amphotericin B, and itraconazole. The transplant was performed with a conditioning regimen of busulfan/cyclophosphamide and 2.9 2 10 6 /kg of CD34 + selected bone marrow cells from his HLA haploidentical mother. Acute grade II graft-versus-host disease (GvHD) was well controlled. Neutrophil counts reached > 0.5 2 10 9 /L by day 15 and platelet counts reached > 50 2 10 9 /L by day 48. The T-cell subset (counts) in peripheral blood increased to 42.2% (0.31 2 10 9 /L) by day 46. The pneumonia improved by day 54. The patient has been doing well with limited chronic GvHD of the gut with a follow-up of longer than 40 months after BMT. Conquest of aspergillus pneumonia in SCID infants could be achieved by CD34 + bone marrow cell transplantation together with appropriate anti-fungal treatment.

Ex vivo expansion of canine dendritic cells from CD34+ bone marrow progenitor cells.

The aims of this study were to ex vivo expand canine dendritic cells and determine their phenotype and functional characteristics. CD34+-selected cells and CD34+-depleted canine bone marrow (BM) cells were cultured in Iscove's modified medium for 14 days. Cytokines added to the cultures included human granylocyte/macrophage colony-stimulating factor 5 ng/ml, hFlt3 ligand 200 ng/ml, and human tumor necrosis factor-alpha 10 ng/ml. Cultured cells and purified subpopulations were assessed for cell surface antigen expression, morphology, and function by flow cytometric analysis, electron microscopy, and an allogeneic mixed lymphocyte reaction at day 14. Two main cell populations were identified, DR++(bright)/CD14- and DR+(dim)/CD14+. Ex vivo expanded CD34+-selected cells showed increased allostimulatory activity compared to both cultured CD34+-depleted cells and mononuclear cells. In contrast, ex vivo expansion from CD34+-depleted cells was unsuccessful. After sorting cells from the ex vivo expanded CD34+-selected bone marrow to enrich for DR++/CD14- cells, a 42-fold increase (median) of allostimulatory activity was observed as compared with sorted DR+/CD14+ cells (P=0.02). Cells with dentric cell-like phenotypes and functions can be cultured from canine CD34+-selected bone marrow cells. Future studies will address the roles of these cells in engraftment, graft versus host reactions and graft-host tolerance in a canine hematogoietic stem cell transplantaton model.

Expression of novel surface antigens on early hematopoietic cells.

The purpose of this report is to demonstrate the expression of very recently identified surface antigens on CD34+ and AC133+ bone marrow (BM) cells. Coexpression analysis of AC133 and defined antigens on CD34+ BM cells revealed that the majority of the CD164+, CD135+, CD117+, CD38low, CD33+, and CD71low cells resides in the AC133+ population. In contrast, most of the CD10+ and CD19+ B cell progenitors and a fraction of the CD71high population are AC133-, indicating that CD34+AC133+ cells are enriched in primitive and myeloid progenitor cells, whereas CD34+AC133- cells mainly consist of B cell and late erythroid progenitors. This corresponds to the highly reduced percentage of CD10+ B cells and the absence of CD71high erythroid progenitors on AC133+ selected BM cells. A portion of 0.2-0.7% of the AC133+ selected cells do not coexpress CD34. These cells are very small and define a uniform CD71-, CD117-, CD10-, CD38low, CD135+, HLA-DRhigh, CD45+ population with unknown delineation. Four color analysis on CD34+CD38- BM cells revealed that virtually all of these primitive cells express AC133. Using an improved liposome-enhanced labeling technique for the staining of weakly expressed antigens, subsets of this population could be identified which express the angiopoietin receptors TIE (67.6%) and TEK (36.8%), the vascular endothelial growth factor receptors FLT1 (7%), FLT4 (3.2%), and KDR (10.4%), or the receptor tyrosine kinases HER-2 (15.4%) and FLT3 (CD135; 77.6%). Our results suggest that the CD34+CD38- population is heterogeneous with respect to the expression of the analyzed receptor tyrosine kinases.

Megakaryocyte ex vivo expansion potential of three hematopoietic sources in serum and serum-free medium.

Megakaryocytes (MK) were expanded from purified human CD34+ cells obtained from three sources, bone marrow (BM), mobilized peripheral blood progenitor cells (PB), and umbilical cord (UC) blood. CD34+-selected cells were cultured for 12 days with 10 ng/ml thrombopoietin (TPO), 10 ng/ml IL-3, 10 ng/ml TPO + 10 ng/ml IL-3, or 200 ng/ml promegapoietin (PMP), a chimeric dual agonist of the c-Mpl and human IL-3 receptors. MK production was compared in serum-free versus human serum-supplemented liquid media. PMP and the combination of TPO and IL-3 (TPO + IL-3) increased MK production similarly. Culturing CD34+ cells with PMP in serum-free medium resulted in a twofold increase in MK yield compared with serum-supplemented medium. CD34+ cells from UC proliferated more than those from either BM or PB in liquid culture, resulting in much greater MK production under all conditions. Phenotypic analysis of the uncultured CD34+ cells showed that BM had a higher frequency of CD34+/CD41+ cells than PB or UC. TPO + IL-3 or PMP produced larger and greater numbers of BFU-MK and CFU-MK per seeded CD34+/CD41+ cell from UC than from either BM or PB. Thus, although uncultured CD34+-selected BM cells contained a higher frequency of committed mature MK progenitors, UC CD34+ cells had a greater proliferative capacity and, therefore, were more productive. PMP induced megakaryocytopoietic activity comparable to that achieved with TPO + IL-3 and may be useful for ex vivo expansion of MK for clinical trials.

Prion Protein Expression in Human Leukocyte Differentiation

The cellular isoform of the prion protein (PrPC) is a small glycoprotein attached to the outer leaflet of the plasma membrane by a glycosylphosphatidylinositol anchor. This molecule is involved in the pathogenesis of prion diseases in both humans and animals. We have characterized the expression patterns of PrPC during human leukocyte maturation by flow cytometry with monoclonal antibodies to PrPC, the glycan moiety CD15, and the stem cell marker CD34. We observe that prion protein is present on CD34+bone marrow (BM) stem cells. Although lymphocytes and monocytes maintain PrPC expression throughout their differentiation, PrPC is downregulated upon differentiation along the granulocyte lineage. In vitro retinoic acid–induced differentiation of the premyeloid line HL-60 into granulocyte-like cells mimics the suppression of PrPC in granulocyte differentiation, as both PrPC mRNA and protein are downregulated. These data suggest that selected BM cells and peripheral mononuclear cells may support prion agent replication, because this process is dependent on availability of PrPC. Additionally, retinoic acid–induced extinction of PrPC expression in HL-60 cells provides a potential model to study PrP gene regulation and protein function. Finally, these data suggest the existence of cell-specific glycoforms of PrPC that may determine cellular susceptibility to infection by the prion agent.

Prion Protein Expression in Human Leukocyte Differentiation

AbstractThe cellular isoform of the prion protein (PrPC) is a small glycoprotein attached to the outer leaflet of the plasma membrane by a glycosylphosphatidylinositol anchor. This molecule is involved in the pathogenesis of prion diseases in both humans and animals. We have characterized the expression patterns of PrPC during human leukocyte maturation by flow cytometry with monoclonal antibodies to PrPC, the glycan moiety CD15, and the stem cell marker CD34. We observe that prion protein is present on CD34+bone marrow (BM) stem cells. Although lymphocytes and monocytes maintain PrPC expression throughout their differentiation, PrPC is downregulated upon differentiation along the granulocyte lineage. In vitro retinoic acid–induced differentiation of the premyeloid line HL-60 into granulocyte-like cells mimics the suppression of PrPC in granulocyte differentiation, as both PrPC mRNA and protein are downregulated. These data suggest that selected BM cells and peripheral mononuclear cells may support prion agent replication, because this process is dependent on availability of PrPC. Additionally, retinoic acid–induced extinction of PrPC expression in HL-60 cells provides a potential model to study PrP gene regulation and protein function. Finally, these data suggest the existence of cell-specific glycoforms of PrPC that may determine cellular susceptibility to infection by the prion agent.

Lethally irradiated normal strains of mice radioprotected with SCID bone marrow develop sensitivity to low doses of staphylococcal enterotoxin B

Normal strains of mice are rendered sensitive to small amounts (3–10 μg) of staphylococcal enterotoxin B (SEB) by transplanting bone marrow cells of SCID donor mice to lethally irradiated recipients. Four to 12 weeks post-transplantation, SEB induces 56–100% lethality. Transplantation of normal mouse bone marrow cells, either alone or with the SCID mouse selected bone marrow cells, does not confer SEB sensitivity. These data imply that either irradiation ablates certain cell population(s), that confer resistance to SEB in normal mice (populations that are absent in the SCID donor mice) or that the donor cells selectively repopulate recipients with SEB-sensitive cells. This model will help elucidate the cells, cytokines and the SEB peptide fragments responsible for SEB toxicity and will be useful in identifying promising vaccine candidates and in developing preventive medicines to protect against this potent toxin.

Enrichment of interleukin-2-responsive natural killer progenitors in human bone marrow

Natural killer (NK) cells can be cultured in interleukin-2 (IL-2)-containing medium from selected human bone marrow (BM) cells obtained after the elimination of mature T and NK cells. To isolate and characterize IL-2-responsive NK progenitors in the selected BM cells, we investigated the expression of IL-2 receptors (IL-2R) on these cells. Neither CD25 (IL-2R alpha) nor IL-2R beta antigen was observed on the selected BM cells before culture. However, CD25+ cells without detectable levels of IL-2R beta antigen appeared 24 hours after culture in IL-2-containing medium. Cells were sorted from each fraction of the selected BM cells 24 hours after culture after staining with anti-CD33, anti-CD34, and anti-CD25 monoclonal antibodies. The generation of NK cells (CD3- CD56+ cells) and NK activity were observed only from the CD33-/CD34-/CD25+ cell fraction after culture in IL-2-containing medium. The frequency of IL-2-responsive NK progenitors relative to the fraction was 1/231 (95% confidence range, 1/156 to 1/289), which corresponded to the frequency relative to the total number of selected BM cells when the frequency relative to the CD33-/CD34-/CD25+ cell-fraction was converted according to the percentage of these cells in the total number of selected BM cells. These results indicated that IL-2-responsive NK progenitors were enriched in the CD33-/CD34-/CD25+ cell fraction.

Enrichment of Interleukin-2-Responsive Natural Killer Progenitors in Human Bone Marrow

Abstract Natural killer (NK) cells can be cultured in interleukin-2 (IL-2)- containing medium from selected human bone marrow (BM) cells obtained after the elimination of mature T and NK cells. To isolate and characterize IL-2-responsive NK progenitors in the selected BM cells, we investigated the expression of IL-2 receptors (IL-2R) on these cells. Neither CD25 (IL-2R alpha) nor IL-2R beta antigen was observed on the selected BM cells before culture. However, CD25+ cells without detectable levels of IL-2R beta antigen appeared 24 hours after culture in IL-2-containing medium. Cells were sorted from each fraction of the selected BM cells 24 hours after culture after staining with anti-CD33, anti-CD34, and anti-CD25 monoclonal antibodies. The generation of NK cells (CD3- CD56+ cells) and NK activity were observed only from the CD33-/CD34-/CD25+ cell fraction after culture in IL-2-containing medium. The frequency of IL-2-responsive NK progenitors relative to the fraction was 1/231 (95% confidence range, 1/156 to 1/289), which corresponded to the frequency relative to the total number of selected BM cells when the frequency relative to the CD33-/CD34-/CD25+ cell- fraction was converted according to the percentage of these cells in the total number of selected BM cells. These results indicated that IL- 2-responsive NK progenitors were enriched in the CD33-/CD34-/CD25+ cell fraction.

Decreased frequency of bone marrow NK progenitors in aplastic anaemia.

Twelve patients with aplastic anaemia were studied with regard to the frequency of NK progenitors in the bone marrow (BM) to investigate the mechanism of depressed NK activity and low NK cell count in the peripheral blood. NK cell (CD16+ cell) count and NK (K562) activity were significantly decreased (P less than 0.02 and P less than 0.001, respectively) in the patients as compared to eight healthy control subjects. Nylon wool non-adherent (NW-NA) BM mononuclear cells (MNC) of each patient and control were prepared. Mature T and NK cells were extensively depleted by sheep red cell rosette formation followed by a centrifugation on Ficoll-Hypaque and monoclonal antibody mediated complement dependent cytolysis. Those selected BM cells were cultured in the presence of recombinant interleukin 2 (rIL2). Generation of NK activity was significantly decreased (P less than 0.01) in the patients with aplastic anaemia. Frequency of NK progenitors in the selected BM cells assayed by the limiting dilution method was significantly decreased in those patients (P less than 0.05). The frequency of BM NK progenitors relative to NW-NA BM cells were related to NK cell count (P less than 0.01). Those results indicate that depressed NK activity in aplastic anaemia is closely related to decreased NK cell count which is probably due to decreased production of NK cells in the BM.