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In vitro differentiation of B cells and myeloid cells from the early mouse embryo and its extraembryonic yolk sac.

The yolk sac is the first site of hematopoiesis during ontogeny. However, the source of early embryonic hematopoietic stem cells remains unresolved. Early studies have shown that cells obtained from day-8 and -9 extraembryonic yolk sacs can give rise to T cells and myeloid cells, whereas the embryo itself appears to lack such cells. Controversy remains as to whether it is the embryo itself or the extraembryonic yolk sac that contains the initial precursors capable of differentiating into B cells. This study used the approach of enriching hematopoietic stem cells by immunocytoadherence and studying cells isolated from within the embryo itself or from the yolk sac obtained at days 8 and 9 of mouse embryonic development. We report that on day 9, both yolk sac-derived and embryo-derived cells can give rise to B cells and myeloid cells in vitro. On day 8, however, cells isolated from the yolk sac but not from the embryo produce myeloid colonies in vitro; neither source of stem cells generates B cells. Our study suggests that myeloid precursors migrate from yolk sac to embryo earlier than has previously been reported but that the origin for B cell precursors remains to be determined.

Animals↗

In vitro and in vivo differentiation into B cells, T cells, and myeloid cells of primitive yolk sac hematopoietic precursor cells expanded > 100-fold by coculture with a clonal yolk sac endothelial cell line.

The yolk sac, first site of hematopoiesis during mammalian development, contains not only hematopoietic stem cells but also the earliest precursors of endothelial cells. We have previously shown that a nonadherent yolk sac cell population (WGA+, density < 1.077, AA4.1+) can give rise to B cells, T cells and myeloid cells both in vitro and in vivo. We now report on the ability of a yolk sac-derived cloned endothelial cell line (C166) to provide a suitable microenvironment for expansion of these early precursor cells. Single day 10 embryonic mouse yolk sac hematopoietic stem cells wer expanded > 100 fold within 8 days by coculture with irradiated C166 cells. Colony-forming ability was retained for at least three passages in vitro, with retention of the ability to differentiate into T-cell, B-cell, and myeloid lineages. Stem cell properties were maintained by a significant fraction of nonadherent cells in the third passage, although these stem cells expressed a somewhat more mature cell surface phenotype than the initial yolk sac stem cells. When reintroduced into adult allogeneic immunocompromised (scid) hosts, they were able to give rise to all of the leukocyte lineages, including T cells, B cells, and myeloid cells. We conclude that yolk sac endothelial cells can support the stable proliferation of multipotential hematopoietic stem cells, thus generating adequate numbers of cells for study of the mechanisms involved in their subsequent development and differentiation, for in vivo hematopoietic restitution, and for potential use as a vehicle for gene transfer.

Animals↗

Membrane protein hMYADM preferentially expressed in myeloid cells is up-regulated during differentiation of stem cells and myeloid leukemia cells.

We report here the molecular cloning and characterization of a novel human gene (hMYADM) derived from a human bone marrow stromal cell (BMSC) cDNA library, which shares high homology with mouse myeloid-associated differentiation marker (MYADM). hMYADM is also closely related to many other eukaryotic proteins, which together form a novel and highly conserved MYADM-like family. hMYADM with 322-residue protein contains eight putative transmembrane segments and confocal microscopic analysis confirmed its membrane localization by using anti-hMYADM monoclonal antibody. hMYADM mRNA was selectively expressed in human monocytes, dendritic cells, promyeloid or monocytic leukemia cell lines, but not in CD4+, CD8+, CD19+ cells, nor in T cell leukemia or lymphocytic leukemia cell lines. hMYADM expression was also found in normal human bone marrow enriched for CD34+ stem cells, and the expression was up-regulated when these cells were induced to differentiate toward myeloid cells. The mRNA expression level of hMYADM significantly increased in acute promyelocytic leukemia HL-60 and chronic myelogenous leukemia K562 cell line after phorbol myristate acetate (PMA)-induced differentiation. Our study suggests that hMYADM is selectively expressed in myeloid cells, and involved in the myeloid differentiation process, indicating that hMYADM may be one useful membrane marker to monitor stem cell differentiation or myeloid leukemia differentiation.

Amino Acid Sequence↗

Inhibition of human immunodeficiency virus type 1 multiplication by transforming growth factor beta 1 and AZT in HIV-1-infected myeloid cells.

Myeloid cells are important reservoirs of HIV-1 infection. In response to pathogenic agents, macrophages secrete inflammatory cytokines that can modulate viral replication and contribute to AIDS pathogenesis. Because HIV replication is dependent on cellular activation, immunosuppressive cytokines that deactivate macrophages and T cells may be important modulators of an antiviral effect. We tested the anti-HIV potential of the immunosuppressive cytokine-transforming growth factor beta (TGF-beta 1) alone and in combination with AZT in a new monomyeloblastic model of HIV-1 infection. The PLB-985 cell model was infected with HIV IIIB strain, and the course of HIV-1 infection and replication was monitored by reverse transcriptase assay, p24 immunofluorescence, and northern blot analysis of HIV-1-specific mRNA. TGF-beta 1 as a single agent had no effect on the multiplication of HIV-IIIB in de novo-infected PLB 985 monomyeloblastic cells. However, cotreatment with TGF-beta 1 and AZT synergistically slowed virus multiplication within the first week following infection, as determined by reverse transcriptase measurement, p24 antigen detection, and northern blot analysis of viral RNA. The synergistic actions of TGF-beta 1 and AZT were also observed in PLB 985 cells infected with an AZT-resistant strain of HIV-1 (HIV 1393). Synergism between nucleoside analogs and cytokines may be an important therapeutic approach to HIV-1 infection. Elucidation of the role of cytokines in controlling the degree of HIV multiplication may have an impact on both clinical treatments and understanding the progression to AIDS.

Acquired Immunodeficiency Syndrome↗

Single adult human CD34(+)/Lin-/CD38(-) progenitors give rise to natural killer cells, B-lineage cells, dendritic cells, and myeloid cells.

Marrow stromal cultures support adult CD34(+)/Lin-/HLA-DR- or CD34(+)/Lin-/CD38(-) cell differentiation into natural killer (NK) or myeloid cells, but unlike committed lymphoid progenitors (CD34(+)/Lin-/CD45RA+/CD10(+)), no B cells are generated. We tested whether different microenvironments could establish a developmental link between the NK and B-cell lineages. Progenitors were cultured in limiting dilutions with interleukin-7 (IL-7), flt3 ligand (FL), c-kit ligand (KL), IL-3, IL-2, and AFT024, a murine fetal liver line, which supports culture of transplantable murine stem cells. NK cells, CD10(+)/CD19(+) B-lineage cells and dendritic cells (DC) developed from the same starting population and IL-7, FL, and KL were required in this process. Single cell deposition of 3,872 CD34(+)/Lin-/CD38(-) cells onto AFT024 with IL-7, FL, KL, IL-2, and IL-3 showed that a one time addition of IL-3 at culture initiation was essential for multilineage differentiation from single cells. Single and double lineage progeny were frequently detected, but more importantly, 2% of single cells could give rise to at least three lineages (NK cells, B-lineage cells, and DC or myeloid cells) providing direct evidence that NK and B-lineage differentiation derive from a common lymphomyeloid hematopoietic progenitor under the same conditions. This study provides new insights into the role of the microenvironment niche, which governs the earliest events in lymphoid development.

ADP-ribosyl Cyclase↗

Human hematopoietic precursors in long-term culture: single CD34+ cells that lack detectable T cell, B cell, and myeloid cell antigens produce multiple colony-forming cells when cultured with marrow stromal cells.

CD34+ human marrow cells not expressing T cell-, B cell-, and myeloid cell-associated antigens (TBM-) were cloned by two-color cell sorting into culture wells containing irradiated marrow stromal cells. After 4 wk of culture, 3.7 +/- 2.1% of these cells generated colony-forming cells (CFC), with each of these cells generating 6.3 +/- 5.3 CFC. This was not due to the 0.5 +/- 0.5% CFC present in the purified CD34+ TBM- cells, as less than 1% of CFC persist in these cultures. This is the first demonstration that single immature precursor cells in human long-term cultures generate multiple CFC progeny. The immature nature of these clonable CD34+ TBM- precursors suggests their candidate status as human hematopoietic stem cells.

Antibodies, Monoclonal↗

Effects of microflora on the neonatal development of gut mucosal T cells and myeloid cells in the mouse.

Colonization with commensal flora in very early life may profoundly influence intestinal lymphoid development and bias later immune responses. We defined gut-homing T cell phenotypes and the influence of flora on intestinal immune development in mice. Intestinal T cells were phenotyped and quantified in conventional (CV), germfree (GF) and conventionalized germfree (GF/CV) neonatal mice by immunohistochemistry. Mucosal adressin cell adhesion molecule 1 (MAdCAM-1) was expressed by mucosal vessels at birth in CV and GF mice and was more prevalent in CV than GF small intestine, but was distributed similarly and did not change with age. Less MAdCAM-1 was expressed in the colon; its distribution became restricted after weaning, with no difference between CV and GF mice. CD3(+)beta(7) (+) cells were present in similar numbers in CV and GF intestine at birth. They were CD62L(-) in CV mice and were accompanied by further CD3(+)beta(7) (+)CD62L(-) T cells as development progressed, but in GF and GF/CV intestine they expressed CD62L and numbers did not change. IEL numbers increased at weaning in CV mice in both small and large intestine, but showed delayed development in GF intestine. Macrophages were present at high levels from birth in GF intestine, but dendritic cells did not develop until day 16. Thus, fetus-derived T cells seed the intestinal lamina propria before birth via beta-MadCAM interactions. Their activation status depends on the microbiological status of the dam, and without a commensal flora they remain naive. We propose that these cells regulate antigen responsiveness of the developing mucosal T cell pool.

Aging↗

A novel pair of immunoglobulin-like receptors expressed by B cells and myeloid cells.

An Fcalpha receptor probe of human origin was used to identify novel members of the Ig gene superfamily in mice. Paired Ig-like receptors, named PIR-A and PIR-B, are predicted from sequence analysis of the cDNAs isolated from a mouse splenic library. Both type I transmembrane proteins possess similar ectodomains with six Ig-like loops, but have different transmembrane and cytoplasmic regions. The predicted PIR-A protein has a short cytoplasmic tail and a charged Arg residue in the transmembrane region that, by analogy with the FcalphaR relative, suggests the potential for association with an additional transmembrane protein to form a signal transducing unit. In contrast, the PIR-B protein has an uncharged transmembrane region and a long cytoplasmic tail containing four potential immunoreceptor tyrosine-based inhibitory motifs. These features are shared by the related killer inhibitory receptors. PIR-A proteins appear to be highly variable, in that predicted peptide sequences differ for seven randomly selected PIR-A clones, whereas PIR-B cDNA clones are invariant. Southern blot analysis with PIR-B and PIR-A-specific probes suggests only one PIR-B gene and multiple PIR-A genes. The PIR-A and PIR-B genes are expressed in B lymphocytes and myeloid lineage cells, wherein both are expressed simultaneously. The characteristics of the highly-conserved PIR-A and PIR-B genes and their coordinate cellular expression suggest a potential regulatory role in humoral, inflammatory, and allergic responses.

Amino Acid Sequence↗

Simultaneous expression of T-cell and myeloid cell phenotypes in eight newly established HTLV-I-positive T-cell lines.

Eight cell lines were established from patients with adult T-cell leukemia, and from normal adults, by cocultivation with human T-cell leukemia virus type I(HTLV-I)-producer cell lines in the presence of interleukin-2. All of these cell lines harbored HTLV-I and showed T-cell markers CD2, CD3 and CD4, but not B-cell markers. Unexpectedly, all eight cell lines expressed a myeloid marker CD13 and three of the eight lines also expressed another myeloid marker CD33. Dual staining showed the simultaneous expression of CD3 and CD13 on the same cells. Thus, evidence was obtained for the expression of myeloid antigens on HTLV-I-harboring T cells.

Adult↗

Differential ability of flt3-ligand, interleukin-11, and Steel factor to support the generation of B cell progenitors and myeloid cells from primitive murine fetal liver cells.

A variety of factors produced by stromal fibroblasts, including Flt3-ligand (FL), interleukin-11 (IL-11), Steel factor (SF), and IL-7, have been implicated in stimulating the production of pre-B cells and myeloid cells from primitive hematopoietic precursors. To investigate their relative roles in this process, either as single-acting or synergistic agents, we compared the yield and types of cells produced after 2 weeks from small numbers of Sca-1+ Lin- (i.e., B220-, Ly-1-, Gr-1-, and Ter-119-) day 14.5 murine fetal liver cells placed in stromal cell-free cultures containing all possible combinations of FL, SF, IL-7, and IL-11. None of these factors alone supported the production (or survival) of any cells beyond 1 week: only pairs of factors consisting of either FL or SF plus either IL-11 or IL-7 were effective in this regard, with FL plus IL-11 being the most potent pair (approximately 7 x 10(4) cells obtained per 100 Sca-1+ Lin- input cells). The maximum numbers of cells were produced in the presence of FL, IL-11, and IL-7: these included both B220+ and Mac-1+/Gr-1+ cells (approximately 10(6) and approximately 2 x 10(5), respectively, per 100 Sca-1+ Lin- input cells). Both of these lineages were also obtained with each of the other possible three-factor combinations, albeit with variable effectiveness. Omission of either FL or IL-7 caused the greatest reduction in the yield of B220+ cells (approximately 130-fold and approximately 80-fold, respectively). Omission of IL-11 and, to a lesser extent, FL caused the greatest reduction in the yield of Mac-1+/Gr-1+ cells (approximately 90-fold and approximately 3-fold, respectively). When fetal calf serum was replaced with a defined serum substitute, the out put of B220+ cells remained the same but myelopoiesis was consistently enhanced (approximately 5- to 20-fold). These findings support a model involving factor redundancy in the extracellular signals required to stimulate the production and amplification of both lymphoid and myeloid cells from early Sca-1+ Lin- cells. They also reveal quantitative differences in the abilities of different competent factor combinations to promote this process, which may be further modulated by the presence of undefined serum components.

Animals↗

Bispecific antibody-targeted phagocytosis of HER-2/neu expressing tumor cells by myeloid cells activated in vivo.

Studies from our laboratory and others have established that both mononuclear phagocytes and neutrophils mediate very efficient cytotoxicity when targeted through Fc receptors using a suitable monoclonal or bispecific antibody (BsAb). Cross-linking an Fc receptor for IgG (FcgammaR) triggers multiple anti-tumor activities including superoxide generation, cytokine and enzyme release, phagocytosis and antibody-dependent cellular cytotoxicity (ADCC). In this report, using unfractionated leukocytes and two color flow cytometric analysis, we describe the phagocytic capacity of peripheral blood polymorphonuclear cells (PMN) and monocytes isolated from patients enrolled in a phase I clinical trial of MDX-H210 given in combination with IFNgamma. MDX-H210 is a BsAb targeting the myeloid trigger molecule FcgammaRI and the HER-2/neu proto-oncogene product overexpressed on a variety of adenocarcinomas. In this trial, cohorts of patients received escalating doses of MDX-H210 3 times per week for 3 weeks. Interferon-gamma (IFNgamma) was given 24 h prior to each BsAb infusion. Our results demonstrate that monocytes from these patients were inherently capable of phagocytosing the HER-2/neu positive SK-BR-3 cell line and that addition of MDX-H210 into the assay significantly enhanced the number of targets phagocytosed. Two days after administration of an immunologically active dose of MDX-H210 (10 mg/m2), monocytes from these patients were able to phagocytose greater amounts of target cell material, indicating that these cells remained armed with functionally sufficient BsAb for at least 48 h. PMN from these patients very efficiently mediated phagocytosis through FcgammaRI after being treated with IFNgamma, but not before. We conclude that phagocytosis is not only an efficient mechanism of myeloid cell-mediated cytotoxicity, but may also be a mechanism by which antigens from phagocytosed cells can enter a professional antigen presenting cell for processing and presentation.

Animals↗

Deletion of the pleckstrin and phosphotyrosine binding domains of insulin receptor substrate-2 does not impair its ability to regulate cell proliferation in myeloid cells.

32D IGF-I receptor (IR) cells are IL-3-dependent myeloid cells that can be induced to differentiate into granulocytes by IGF-I. Like the parental 32D cells, 32D IGF-IR cells do not express the insulin receptor substrate (IRS)-1 or IRS-2. We investigated the effect of ectopic expression of IRS-2 in 32D IGF-IR cells. Expression in these cells of a wild-type IRS-2 inhibits IGF-I-induced differentiation, and the cells grow indefinitely in the absence of IL-3. We also investigated the effect of a mutant IRS-2 lacking both the pleckstrin (PH) and the phosphotyrosine-binding (PTB) domains, which are known to bind to the IR. The partial differentialPHPTB IRS-2 is fully as capable as the wild-type IRS-2 (and wild-type IRS-1) to stimulate the growth and inhibit the differentiation of 32D IGF-IR cells. In contrast, an IRS-1 protein lacking the same PH and PTB domains is completely inactive in blocking differentiation and stimulating IL-3-independent growth of 32D IGF-IR cells. The partial differentialPHPTB IRS-2 protein is dependent for its effect on an activated IGF-IR, is cytoplasmic, binds to the beta-subunit of the IGF-IR, and requires for its action the presence of phosphatidylinositol 3-kinase binding sequences. These experiments show that the PH and PTB domains of IRS-2 (but not IRS-1) are dispensable for the IGF-I/IRS-2-mediated growth of 32D myeloid cells. Our results also indicate that IRS-2 (either wild type or partial differentialPHPTB) is capable of inhibiting the differentiation of 32D cells.

Animals↗

Expression and roles of Cl- channel ClC-5 in cell cycles of myeloid cells.

ClC-5 is a chloride channel known to be expressed in the kidney. We previously reported that ClC-5 mRNA was also strongly expressed in immature human myeloid cell line (HL-60), but weakly expressed in mature neutrophils. To clarify the underlying mechanisms, we examined the relationship between ClC-5 expression and cell cycle. Dimethyl sulfoxide treatment of HL-60 that causes differentiation with G0/G1 cell cycle arrest decreased the expression of ClC-5 mRNA. Cell sorting and synchronization experiments revealed that ClC-5 mRNA expression was high in S and G2/M phases and low in G0/G1 phase. ClC-5 antisense oligonucleotide suppressed proliferation of HL-60 cells with a decrease in ClC-5 protein expression, probably due to G2 arrest. These results suggest that cell cycle-dependent expression of ClC-5 has a role in cell cycle progression in myeloid cells.

Cell Cycle↗

Human lymphoid and myeloid cell development in NOD/LtSz-scid IL2R gamma null mice engrafted with mobilized human hemopoietic stem cells.

Ethical considerations constrain the in vivo study of human hemopoietic stem cells (HSC). To overcome this limitation, small animal models of human HSC engraftment have been used. We report the development and characterization of a new genetic stock of IL-2R common gamma-chain deficient NOD/LtSz-scid (NOD-scid IL2Rgamma(null)) mice and document their ability to support human mobilized blood HSC engraftment and multilineage differentiation. NOD-scid IL2Rgamma(null) mice are deficient in mature lymphocytes and NK cells, survive beyond 16 mo of age, and even after sublethal irradiation resist lymphoma development. Engraftment of NOD-scid IL2Rgamma(null) mice with human HSC generate 6-fold higher percentages of human CD45(+) cells in host bone marrow than with similarly treated NOD-scid mice. These human cells include B cells, NK cells, myeloid cells, plasmacytoid dendritic cells, and HSC. Spleens from engrafted NOD-scid IL2Rgamma(null) mice contain human Ig(+) B cells and lower numbers of human CD3(+) T cells. Coadministration of human Fc-IL7 fusion protein results in high percentages of human CD4(+)CD8(+) thymocytes as well human CD4(+)CD8(-) and CD4(-)CD8(+) peripheral blood and splenic T cells. De novo human T cell development in NOD-scid IL2Rgamma(null) mice was validated by 1) high levels of TCR excision circles, 2) complex TCRbeta repertoire diversity, and 3) proliferative responses to PHA and streptococcal superantigen, streptococcal pyrogenic exotoxin. Thus, NOD-scid IL2Rgamma(null) mice engrafted with human mobilized blood stem cells provide a new in vivo long-lived model of robust multilineage human HSC engraftment.

Aging↗

Severe combined immunodeficiency mice engrafted with human T cells, B cells, and myeloid cells after transplantation with human fetal bone marrow or liver cells and implanted with human fetal thymus: a model for studying human gene therapy.

To develop an in vivo model wherein human hematopoiesis occurs, we transplanted severe combined immunodeficiency (SCID) mice with either human fetal bone marrow (HFBM) or human fetal liver (HFL). After transplantation of SCID mice with cultured HFBM (BM-SCID-hu mice) or HFL cells (Liv-SCID-hu mice), significant engraftment of the mouse bone marrow (BM) and population of the peripheral blood with human leukocytes was detected. Human colony-forming unit-granulocyte macrophage and burst forming unit-erythroid were detected in the BM of the BM-SCID-hu and Liv-SCID-hu mice up to 8 months after transplantation. When the HFBM or HFL cells were transduced with a retroviral vector before transplantation, integrated retroviral sequences were detected in human precursor cells present in the SCID mouse BM and in leukocytes circulating in the peripheral blood (PB) up to 7 months after transplantation. The PB of the BM-SCID-hu mice also became populated with human T cells after implantation with human thymic tissue, which provided a human microenvironment wherein human pre-T cells from the BM could mature. When the HFBM was retrovirally transduced before transplantation, integrated retrovirus was detected in sorted CD4+CD8+ double positive and CD4+ single positive cells from the thymic implant and CD4+ cells from the PB. Taken together, these data indicated that the BM of our BM-SCID-hu and Liv-SCID-hu mice became engrafted with retrovirally transduced human hematopoietic precursors that undergo the normal human hematopoietic program and populate the mouse PB with human cells containing integrated retroviral sequences. In addition to being a model for studying in vivo human hematopoiesis, these mice should also prove to be a useful model for investigating in vivo gene therapy using human stem/precursor cells.

Animals↗

In vitro chemosensitivity testing of selected myeloid cells in acute myeloid leukemia.

In several studies different chemosensitivity assays have been examined in acute myeloid leukemia (AML). Some have shown that in vitro chemosensitivity testing is an independent prognostic factor but so far no one has been able to show that the use of these methods can improve treatment outcome. In an attempt to improve in vitro chemosensitivity testing in AML we wanted to establish and evaluate a new flow cytometry chemosensitivity assay. After 4 days of incubation viable mononuclear myeloid cells were identified by the exclusion of propidium iodide in CD13 or CD33 positive cells. Sixty-eight samples from 64 AML patients were included. In this study, we showed that the flow cytometry method is feasible in AML and we also found some correlations to clinical data. The secondary AML at diagnosis showed an in vitro resistance to etoposide and amsacrine that was significantly higher compared to de novo AML at diagnosis (p = 0.04 and p = 0.02). When AML patients at diagnosis were compared to resistant disease/relapse patients there was a significantly higher effect of ara-C in the diagnosis group (p = 0.03). Responders and non-responders were compared in vitro but we found no significant differences. In vitro mitoxantrone was more effective in multidrug resistance (MDR) negative cells compared to MDR positive cells (p < 0.01). This new method is feasible and makes it possible to selectively evaluate the effect of cytotoxic drugs in myeloid cells. Further studies with a larger group of patients are needed to evaluate the predictive value of the assay.

Acute Disease↗

Analysis of cell death in myeloid cells inducibly expressing the cell cycle protein p55Cdc.

p55Cdc, a cell cycle protein is expressed in cycling mammalian cells and is required for normal cell division. Expression of this protein is regulated during the cell cycle, peaking in late G1 and S. We have previously shown that constitutive expression of p55Cdc results in inhibition of granulocyte differentiation. Degradation of p55Cdc is also required for apoptosis in growth factor and serum starved cells. In the present study we prepared stably transfected cells conditionally expressing p55Cdc in response to zinc stimulation to investigate the role of inducible p55Cdc expression in apoptosis of myeloid cells. We report that inducible expression of p55Cdc in the myeloid leukemic cell line 32Dc13 resulted in increased cell death. p55Cdc overexpression led to a statistically significant decrease in the viability of 32Dc13 cells compared with that of control cells. Furthermore, cell staining and flow cytometry analysis revealed that p55Cdc-overexpressing 32Dc13 cells progressed to apoptosis much earlier than uninduced cells. These results suggest that inducible expression of p55Cdc leads to earlier increases in cell death in the absence of growth factor and serum in myeloid leukemic cells.

Animals↗