In vitro expansion of CD34(+)CD38(-) cells under stimulation with hematopoietic growth factors on AGM-S3 cells in juvenile myelomonocytic leukemia

Using serum-containing culture, we examined whether AGM-S3 stromal cells, alone or in combination with hematopoietic growth factor(s), stimulated the proliferation of CD34(+) cells from patients with juvenile myelomonocytic leukemia (JMML). AGM-S3 cells in concert with stem cell factor plus thrombopoietin increased the numbers of peripheral blood CD34(+) cells to approximately 20-fold of the input value after 2 weeks in nine JMML patients with either PTPN11 mutations or RAS mutations, who received allogeneic hematopoietic transplantation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) also augmented the proliferation of JMML CD34(+) cells on AGM-S3 cells. The expansion potential of CD34(+) cells was markedly low in four patients who achieved spontaneous hematological improvement. A large proportion of day-14-cultured CD34(+) cells were negative for CD38 and cryopreservable. Cultured JMML CD34(+)CD38(-) cells expressed CD117, CD116, c-mpl, CD123, CD90, but not CXCR4, and formed GM and erythroid colonies. Day-7-cultured CD34(+) cells from two of three JMML patients injected intrafemorally into immunodeficient mice stimulated with human GM-CSF after transplantation displayed significant hematopoietic reconstitution. The abilities of OP9 cells and MS-5 cells were one-third and one-tenth, respectively, of the value obtained with AGM-S3 cells. Our culture system may provide a useful tool for elucidating leukemogenesis and for therapeutic approaches in JMML.

Subcutaneous fat accumulation in early infancy is more strongly associated with motor development and delay than muscle growth

AIM

Physical growth in neurologically healthy preterm infants affects motor development. This study investigated the separate relationships between muscle and fat in infancy and later motor development and physical growth.

METHODS

Muscle thickness and subcutaneous fat thickness of the anterior thigh were measured using ultrasound images obtained from neurologically healthy preterm infants at birth, 3, 6, 12 and 18 months' corrected age. We also obtained the Pediatric Evaluation of Disability Inventory and Alberta Infant Motor Scale scores at 18 months' corrected age to assess motor ability and motor delay.

RESULTS

Thirty preterm infants completed the study protocol. There was a significant positive correlation between motor ability and increments in subcutaneous fat thickness during the first 3 and 6 months' corrected age (r = 0.48 and 0.40, p < 0.05, respectively), but not between motor ability and muscle thickness growth in any of the periods. A secondary, logistic regression analysis showed that increments in subcutaneous fat thickness during the first 3 months were a protective factor for motor delay.

CONCLUSION

Subcutaneous fat accumulation in early infancy is more strongly associated with motor development and delay than muscle growth.

[Stem cell and self-renewal]

Stem cells are defined as cells with the ability for self-renewal and differentiation. Hematopoietic stem cells are well known, and their application is useful for the treatment of various kinds of diseases. Recently, neural stem cells have been identified even in the adult brain, which has up to now been considered to be a tissue with no regenerative capacity. In addition, it has emerged that tissue stem cells can differentiate into various kinds of cells beyond their original characteristics. Here, we discuss the self-renewal mechanisms of embryonic stem (ES) cells, hematopoietic stem cells and neural stem cells.

Characterization of the gammac chain among 27 unrelated Japanese patients with X-linked severe combined immunodeficiency (X-SCID)

X-linked severe combined immunodeficiency (X-SCID) is a rare fatal disease that is caused by mutations in the gene encoding the gammac chain. In this study, 27 unrelated Japanese patients with X-SCID were examined in terms of their genetic mutations and surface expression of the gammac chain. Among 25 patients examined, excluding two patients with large deletions, 23 different mutations were identified in the IL2RG gene, including 10 novel mutations. One patient bearing an extracellular mutation and all three of the patients bearing intracellular mutations after exon 7 expressed the gammac chain on the cell surface. Overall, 84% of patients lacked surface expression of the gammac chain leading to a diagnosis of X-SCID.

Activation of Stat3 by cytokine receptor gp130 ventralizes Xenopus embryos independent of BMP-4

Stat3 is one of the main signaling components of cytokine receptors, including gp130. Here we show that activation of cytokine receptor gp130 resulted in a dramatic ventralization of Xenopus embryos and that the ventralization correlated well with Stat3 activation potential of the receptor. This finding led to identification of Xenopus Stat3 (Xstat3), which showed a 95% homology to its murine and human counterparts, at the amino acid level, and was expressed from the one-cell stage throughout development. The mechanism of gp130/XStat3-mediated ventralization proved to be independent of BMP-4. gp130/Xstat3 stimulation inhibited Smad2-induced ectopic axis formation in embryos and Smad2-dependent luciferase activity. A dominant-negative Stat3, in contrast, dorsalized Xenopus embryos, resulting in ectopic axis formation. We propose that Stat3-mediated signaling has the capacity to modify dorsoventral patterning in the early development of Xenopus.

Chimeric cytokine receptor can transduce expansion signals in interleukin 6 receptor alpha (IL-6Ralpha)-, IL-11Ralpha-, and gp130-low to -negative primitive hematopoietic progenitors

We generated transgenic mice expressing chimeric receptors, which comprise extracellular domains of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor and transmembrane and cytoplasmic domains of the mouse leukemia inhibitory factor receptor. In suspension cultures of lineage-negative (Lin(-)), 5-fluorouracil-resistant bone marrow cells of the transgenic mice, a combination of hGM-CSF and stem cell factor (SCF) induced exponential expansions of mixed colony-forming unit. The combination of hGM-CSF and SCF was effective on enriched, Lin(-)Sca-1(+)c-kit(+) progenitors and increased either mixed colony-forming unit or cobblestone area-forming cells. In case of stimulation with hGM-CSF and SCF, interleukin-6 (IL-6) and SCF, or IL-11 and SCF, the most efficient expansion was achieved with hGM-CSF and SCF. When Lin(-)Sca-1(+)c-kit(+)CD34(-) further enriched progenitors were clone sorted and individually incubated in the presence of SCF, hGM-CSF stimulated a larger number of cells than did IL-6, IL-6 and soluble IL-6 receptor (IL-6R), or IL-11. These data suggest the presence of IL-6Ralpha-, IL-11Ralpha-, and gp130-low to -negative primitive hematopoietic progenitors. Such primitive progenitors are equipped with signal transduction molecules and can expand when these chimeric receptors are genetically introduced into the cells and stimulated with hGM-CSF in the presence of SCF.

Hypomethylation of the proximal and intronic regulatory regions of the IFN-gamma gene is not essential for its transcription by naive CD4+ T cells cultured with IL-4

Recently, long-term preculture with IL-4 or IL-7 has been reported to induce IFN-gamma-producing ability in naive CD4+ T cells without stimulation via TCR. The mechanism of IFN-gamma-transcription in naive CD4+ T cells precultured with IL-4 was analyzed and compared with that in typical Th1 cells by focusing on the TATA proximal and first intronic regulatory regions of the IFN-gamma gene. Both regulatory regions in these IL-4-primed naive CD4+ T cells, which produce a large amount of IFN-gamma upon stimulation with PMA and ionomycin, were completely methylated in contrast to the same hypomethylated regions in Th1 cells. DNase I hypersensitive site analysis suggested that both regulatory regions in IL-4-primed naive CD4+ T cells were not active for IFN-gamma-expression. Moreover, we demonstrated that the composition of transcriptional factors that can bind to the proximal regulatory region is different between IL-4-primed naive CD4+ T cells and Th1 cells. These results indicated that the transcriptional machinery involved in the expression of the IFN-gamma gene by CD4+ T cells varied depending on their modes of differentiation in both the responsive regulatory regions and the specific nuclear factors.

STAT3 activation is sufficient to maintain an undifferentiated state of mouse embryonic stem cells

Embryonic stem (ES) cells can be maintained in an undifferentiated state in the presence of leukemia inhibitory factor (LIF). LIF acts through a receptor complex composed of a low affinity LIF receptor (LIFRbeta) and gp130. We reported that the intracellular domain of gp130 plays an important role in self-renewal of ES cells. In the present study, we examined the signaling pathway through which gp130 contributes to the self-renewal of ES cells. Mutational analysis of the cytoplasmic domain of gp130 revealed that the tyrosine residue of gp130 responsible for STAT3 activation is necessary for self-renewal of ES cells, while that required for SHP2 and MAP kinase activation was dispensable. Next, we constructed a fusion protein composed of the entire coding region of STAT3 and the ligand binding domain of the estrogen receptor. This construction (STAT3ER) induced expression of junB (one of the targets of STAT3) in ES cells in the presence of the synthetic ligand 4-hydroxytamoxifen (4HT), thereby indicating that STAT3ER is a conditionally active form. ES cells transfected with STAT3ER cultured in the presence of 4HT maintained an undifferentiated state. Taken together, these results strongly suggest that STAT3 activation is required and sufficient to maintain the undifferentiated state of ES cells.

Cytoplasmic domains of the leukemia inhibitory factor receptor required for STAT3 activation, differentiation, and growth arrest of myeloid leukemic cells

Leukemia inhibitory factor (LIF) induces growth arrest and macrophage differentiation of mouse myeloid leukemic cells through the functional LIF receptor (LIFR), which comprises a heterodimeric complex of the LIFR subunit and gp130. To identify the regions within the cytoplasmic domain of LIFR that generate the signals for growth arrest, macrophage differentiation, and STAT3 activation independently of gp130, we constructed chimeric receptors by linking the transmembrane and intracellular regions of mouse LIFR to the extracellular domains of the human granulocyte macrophage colony-stimulating factor receptor (hGM-CSFR) alpha and betac chains. Using the full-length cytoplasmic domain and mutants with progressive C-terminal truncations or point mutations, we show that the two membrane-distal tyrosines with the YXXQ motif of LIFR are critical not only for STAT3 activation, but also for growth arrest and differentiation of WEHI-3B D+ cells. A truncated STAT3, which acts in a dominant negative manner was introduced into WEHI-3B D+ cells expressing GM-CSFRalpha-LIFR and GM-CSFRbetac-LIFR. These cells were not induced to differentiate by hGM-CSF. The results indicate that STAT3 plays essential roles in the signals for growth arrest and differentiation mediated through LIFR.

A selective switch-on system for self-renewal of embryonic stem cells using chimeric cytokine receptors

Propagation of embryonic stem (ES) cells with an undifferentiated pluripotential phenotype depends on leukemia inhibitory factor (LIF). The LIF receptor complex is composed of a heterodimer of LIF receptor alpha (LIFR alpha) and gp130. To activate LIFR signaling pathways independently from endogenous ones, we constructed chimeric receptors by linking the extracellular domain of human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha or beta (hGMR alpha or beta) to the transmembrane and cytoplasmic regions of either mouse LIFR alpha or gp130. hGMR alpha-mLIFR/hGMR beta-mgp130 or hGMR alpha-mgp130/hGMR beta-mgp130, but not hGMR alpha-mLIFR/hGMR beta-mLIFR, preserved the self-renewal activity in A3 ES cells. All of these chimeric receptors were phosphorylated after hGM-CSF stimulation without phosphorylation of endogenous gp130. Phosphorylation of the signal transducer and activator of transcription 3 through chimeric receptors correlated with the undifferentiated phenotype. Therefore, these chimeric receptors prove useful to analyze mechanisms of the self-renewal of ES cells.

IL-4 and prostaglandin E2 inhibit hypomethylation of the 5' regulatory region of IFN-gamma gene during differentiation of naive CD4+ T cells

We have previously shown that prostaglandin E2 (PGE2) and IL-4 inhibit the priming of IFN-gamma-production during the differentiation of naive CD4+ T cells from human cord blood by different signal-transducing mechanisms. To compare and analyse the molecular mechanisms by which PGE2 and IL-4 inhibit the priming of IFN-gamma production, we investigated the effects of PGE2 and IL-4 on the methylation of the IFN-gamma gene during the in vitro differentiation of naive CD4+ T cells. In human naive CD4+ T cells, which produce primarily IL-2 and a little amount of IFN-gamma, the IFN-gamma gene was methylated. After stimulation via TCR, CD4+ T cells produced IFN-gamma and the CpG dinucleotide contained within the TATA proximal regulatory element of the IFN-gamma gene was partially hypomethylated. Both IL-4 and PGE2 inhibited the hypomethylation of this site and the acquisition of IFN-gamma-producing ability. In contrast to the SnaBI site in the TATA proximal regulatory element, the HpalI site in the first intron of the IFN-gamma gene of the CD4+ T cells from cord blood was completely methylated even after stimulation via TCR. 5-azacytidine restored the IFN-gamma-producing ability of these cells treated with IL-4 and PGE2. These findings suggest that, although the signal transduction that inhibits the priming of IFN-gamma-production is different for each reagent, the protection from hypomethylation of the regulatory region of the IFN-gamma gene is involved in the molecular mechanisms by which these reagents inhibit the priming of IFN-gamma-production during the differentiation of human naive CD4+ T cells.

X-linked severe combined immunodeficiency with gamma delta T cells

A patient with X-linked severe combined immunodeficiency (X-SCID) was found to have a deletion mutation of a four base pair in the transmembrane domain of the IL-2 receptor gamma chain gene, a subunit shared by the receptors for IL-4, IL-7, IL-9, and IL-15 (common gamma chain; gamma c). He had very few alpha beta T cells but had a considerable number of gamma delta T cells in his peripheral blood. Fluorescence in situ hybridization (FISH) analysis showed that the gamma delta T cells in his peripheral blood were not of maternal origin. He had received a Bacillus Calmette-Guerin (BCG) vaccination before recognition of the disease, and the BCG infection remained quiescent with no reaction for 19 months. After successful bone marrow transplantation, the site of the BCG vaccination showed a reaction, and live BCG were detected. It is useful to consider the relationship between the existence of gamma delta T cells and BCG in this case, and it is suggested that gamma delta T cells may be, in a given situation, less dependent on the gamma c chain than are alpha beta T cells.

Negative signaling in B cells by surface immunoglobulins

Cross-linking of surface immunoglobulins generates negative signals that cause B-cell death unless appropriate rescue signals are provided. Surface IgM is the main transducer of the negative signaling, but surface IgD and IgG may also transduce negative signaling when cross-linked intensively. In the surface IgM+, IgD+ human malignant B lymphoma cell lines B104 and DND-39, cross-linking of surface IgM by anti-IgM antibodies induced cell death. Anti-IgM antibody-induced B104 cell death was inhibited by stimulation with alpha- and beta-interferons but not stimulation with anti-CD40 antibody or IL-4, whereas anti-IgM antibody-induced DND-39 cell death was inhibited by stimulation with anti-CD40 antibody but not stimulation with alpha- and beta-interferons. Anti-IgM antibody-stimulated B104 cells had morphologic features compatible with necrosis, whereas anti-IgM antibody-stimulated DND-39 cells showed morphologic features of apoptosis. CD11a/CD54-dependent cell adhesion induced by stimulation with anti-CD40 antibody was involved in anti-CD40 antibody-mediated inhibition of anti-IgM antibody-induced DND-39 cells. In normal human mature B cells, cross-linking of surface IgM induced different signaling consequences, including DNA synthesis or cell division (positive signaling) or cell cycle arrest or death (negative signaling). In this system, too, CD40-transduced signal inhibited anti-IgM antibody-induced negative signaling, and CD11a/CD54-dependent cell adhesion played a role in the rescue process. It is suggested that quantitatively different intensities of surface IgM cross-linking induce qualitatively different signaling consequences; relatively weak cross-linking may induce DNA synthesis; moderate cross-linking may induce DNA synthesis with cell cycle arrest at the G2/M interphase; and intense cross-linking may induce apoptotic cell death. The reasons for this difference are not yet known. Further elucidation of the molecular mechanisms responsible for surface IgM-mediated negative signaling and its rescue signaling may contribute toward development of therapy for allergic disorders by artificial modulation of specific immunoglobulin production.

Signal transduction pathway of interleukin-4 and interleukin-13 in human B cells derived from X-linked severe combined immunodeficiency patients

Interleukin-4 (IL-4) and IL-13 are functionally similar cytokines. The functional IL-4 receptor (IL-4R) consists of the IL-4R alpha chain (IL-4R alpha) and the IL-2R gamma chain (gamma c), which is shared by the IL-2, IL-7, IL-9, and IL-15 receptors. The functional IL-13R is thought to involve the IL-4R alpha but not gamma c. In this study, we have analyzed activation of members of the Janus tyrosine kinase (Jak) family and signal transducers and activators of transcription (STAT) 6 induced by IL-4 and IL-13 in Epstein-Barr virus-transformed B cells derived from two patients of X-linked severe combined immunodeficiency, who have mutations of the gamma c gene in the extracellular and intracellular domains. In these B cells, IL-4 failed to induce tyrosine phosphorylation of Jak3 and activation of STAT6, or activation of these molecules was significantly decreased compared with Epstein-Barr virus-transformed normal B cells. In contrast, IL-13 activated STAT6 in these cells as well as normal B cells. However, Jak3 was not activated by IL-13, even in normal B cells. These results clearly indicated that gamma c is essential for activation of Jak3 and STAT6 in the signal transduction pathway of IL-4 in human B cells and that IL-13 does not utilize gamma c but activates STAT6 through an alternative pathway, which is not impaired in B cells of X-linked severe combined immunodeficiency patients.

Role of LFA-1/ICAM-1-dependent cell adhesion in CD40-mediated inhibition of anti-IgM antibody-induced B-cell death

Cross-linking of surface IgM by anti-IgM antibody caused activation-induced cell death of a surface IgM+, IgD+ human B lymphoma cell line, B104. The dying B104 cells did not show the morphology of apoptosis but did show that of necrosis. However, anti-IgM antibody caused apoptosis of another surface IgM+, IgD+ human B lymphoma cell line, DND-39. The influx of extracellular Ca2+ was necessary for the cell deaths of B104 and DND-39 caused by anti-IgM antibody. Their cell deaths were inhibited by cyclosporine. The anti-IgM antibody-induced cell death of DND-39, but not that of B104, was prevented by costimulation with anti-CD40 antibody. In human peripheral blood B-cells, anti-IgM antibody inhibited cell cycle transition induced by Staphylococcus aureus Cowan I at the G2/M interphase without inhibition of DNA synthesis. In this system, too, anti-CD40 antibody canceled the inhibitory signal transduced through surface IgM and increased the number of M phase cells. Blocking antibodies against the leukocyte function-associated antigen-I/intercellular adhesion molecule-1 system decreased the rescue effect of anti-CD40 antibody in both DND-39 cells and peripheral B-cells, which shows that leukocyte function-associated antigen-1/intercellular adhesion molecule-1-dependent cell adhesion plays an important role in the CD40-mediated inhibition of surface IgM-mediated negative signals.

Pyrrolidine dithiocarbamate inhibits intercellular adhesion molecule-1 biosynthesis induced by cytokines in human fibroblasts

Intercellular adhesion molecule-1 (ICAM-1), the ligand of lymphocyte function-associated antigen-1, plays an important role in the interactions of a variety of hemopoietic and nonhemopoietic cells, including leukocytes, fibroblasts, and endothelial cells. ICAM-1 is known to be involved in the onset of several diseases such as inflammation, allograft rejection, and so on. In this report, we investigated the effects of dexamethasone, cyclosporin A, FK506, and pyrrolidine dithiocarbamate (PDTC) on the induction of the ICAM-1 gene by cytokines in fibroblasts. PDTC, a potent inhibitor of NF-kappa B, was shown by ELISA and FACS analysis to prevent dramatically the expression of the ICAM-1 gene stimulated by IL-1 alpha, IFN-gamma, and PMA, although the other reagents inhibited it only slightly. Ribonuclease protection assay revealed that PDTC blocked the expression of the ICAM-1 gene at the mRNA level. To elucidate the mechanism of this inhibition, we constructed a series of ICAM-1 promoter deletion mutants linked to the chloramphenicol acetyl transferase gene and analyzed the effect of PDTC on their activities. Transient transfection analysis indicated that the critical region for inhibition by PDTC is an NF-kappa B binding site-like motif (GGGAGGATTCC, ICAM-1 kappa B) that is located at position-540. Electrophoresis mobility shift assay revealed that PDTC actually inhibits the binding of NF-kappa B (or NF-kappa B-like) protein to the ICAM-1 kappa B site. These findings suggest that PDTC inhibits ICAM-1 gene expression by inhibiting the association of NF-kappa B (or NF-kappa B-like) protein with the ICAM-1 kappa B site.

Pyrrolidine dithiocarbamate inhibits intercellular adhesion molecule-1 biosynthesis induced by cytokines in human fibroblasts

Intercellular adhesion molecule-1 (ICAM-1), the ligand of lymphocyte function-associated antigen-1, plays an important role in the interactions of a variety of hemopoietic and nonhemopoietic cells, including leukocytes, fibroblasts, and endothelial cells. ICAM-1 is known to be involved in the onset of several diseases such as inflammation, allograft rejection, and so on. In this report, we investigated the effects of dexamethasone, cyclosporin A, FK506, and pyrrolidine dithiocarbamate (PDTC) on the induction of the ICAM-1 gene by cytokines in fibroblasts. PDTC, a potent inhibitor of NF-kappa B, was shown by ELISA and FACS analysis to prevent dramatically the expression of the ICAM-1 gene stimulated by IL-1 alpha, IFN-gamma, and PMA, although the other reagents inhibited it only slightly. Ribonuclease protection assay revealed that PDTC blocked the expression of the ICAM-1 gene at the mRNA level. To elucidate the mechanism of this inhibition, we constructed a series of ICAM-1 promoter deletion mutants linked to the chloramphenicol acetyl transferase gene and analyzed the effect of PDTC on their activities. Transient transfection analysis indicated that the critical region for inhibition by PDTC is an NF-kappa B binding site-like motif (GGGAGGATTCC, ICAM-1 kappa B) that is located at position-540. Electrophoresis mobility shift assay revealed that PDTC actually inhibits the binding of NF-kappa B (or NF-kappa B-like) protein to the ICAM-1 kappa B site. These findings suggest that PDTC inhibits ICAM-1 gene expression by inhibiting the association of NF-kappa B (or NF-kappa B-like) protein with the ICAM-1 kappa B site.

Cis-acting DNA elements of mouse granulocyte-macrophage colony-stimulating factor gene responsive to Fc epsilon receptor cross-linking stimulation in the mouse mast cell line MC/9

Mouse mast cells produce many kinds of cytokines in response to cross-linking of high affinity Fc epsilon receptor (Fc epsilon RI). Among these cytokines, granulocyte-macrophage CSF (GM-CSF) gene induction in mouse mast cells has been reported to be regulated at both the transcriptional level and the post-transcriptional level. We analyzed the mechanism of the transcriptional regulation of GM-CSF gene induction through Fc epsilon RI cross-linking stimulation in the mouse mast cell line MC/9. In MC/9, the GM-CSF gene was activated transcriptionally by Fc epsilon RI cross-linking stimulation. The 5' deletion analysis of GM-CSF gene promoter indicated that the 5' boundary of the responsive promoter region lay between positions -113 and -95. When the deletion was extended to positions -72 or -60, the stimulatory effect was significantly diminished. We then examined 3' deletion of pmGMCAT -113 from position -60. This analysis indicated that the 3' boundary lay between positions -84 and -72. No subfragments of the region spanning positions -113 to -72 could cover the full induction level. A site-directed mutagenesis experiment revealed that the sequence spanning positions -108 to -72 was needed for full activation. These data indicate that GM-CSF gene in mast cells is activated mainly through the sequence spanning positions -108 to -72.

Cis-acting DNA elements of mouse granulocyte-macrophage colony-stimulating factor gene responsive to Fc epsilon receptor cross-linking stimulation in the mouse mast cell line MC/9

Mouse mast cells produce many kinds of cytokines in response to cross-linking of high affinity Fc epsilon receptor (Fc epsilon RI). Among these cytokines, granulocyte-macrophage CSF (GM-CSF) gene induction in mouse mast cells has been reported to be regulated at both the transcriptional level and the post-transcriptional level. We analyzed the mechanism of the transcriptional regulation of GM-CSF gene induction through Fc epsilon RI cross-linking stimulation in the mouse mast cell line MC/9. In MC/9, the GM-CSF gene was activated transcriptionally by Fc epsilon RI cross-linking stimulation. The 5' deletion analysis of GM-CSF gene promoter indicated that the 5' boundary of the responsive promoter region lay between positions -113 and -95. When the deletion was extended to positions -72 or -60, the stimulatory effect was significantly diminished. We then examined 3' deletion of pmGMCAT -113 from position -60. This analysis indicated that the 3' boundary lay between positions -84 and -72. No subfragments of the region spanning positions -113 to -72 could cover the full induction level. A site-directed mutagenesis experiment revealed that the sequence spanning positions -108 to -72 was needed for full activation. These data indicate that GM-CSF gene in mast cells is activated mainly through the sequence spanning positions -108 to -72.

IgM-mediated B cell apoptosis

Cross-linking of surface immunoglobulin M (sIgM) on normal mature B cells induces different signaling consequences, including DNA synthesis (positive signaling) and cell cycle arrest and/or death by apoptosis (negative signaling). Presumably, the difference depends on the intensity of sIgM cross-linking: relatively weak cross-linking induces DNA synthesis, moderate cross-linking induces DNA synthesis with cell cycle arrest at the G2/M interphase, and intense cross-linking induces apoptosis. In vivo experiments with transgenic mice have shown that relatively weak cross-linking of sIgM by soluble antigens induces anergy in autoreactive B cells, whereas intense sIgM cross-linking by membrane-bound forms of antigens induces deletion of them. However, it is still unknown whether the different intensities of sIgM cross-linking generate qualitatively different signals responsible for DNA synthesis or cell death or whether they generate qualitatively the same but quantitatively different signals, and the quantitative difference is responsible for the induction of positive or negative signaling. The sIgM-mediated negative signaling presumably plays an important role in the induction and maintenance of B cell tolerance, and sIgD and sIgG also possess the machinery necessary for negative signaling. Negative signaling through sIgM is dependent on tyrosine kinase(s) and Ca2+ influx and is sensitive to cyclosporin A in certain types of B cells but not in all B cells. It has been suggested that there are different intracellular signaling pathways that transduce negative signaling via sIgM, and that activation-induced B cell death by sIgM cross-linking does not necessarily show DNA fragmentation and the morphology of apoptosis. On the other hand, sIgM-mediated B cell death may be inhibited in the presence of appropriate co-stimulators such as IL-4, alpha-, and beta-interferons and CD40-mediated signaling. The CD40-mediated signaling effectively inhibits sIgM-mediated B cell apoptosis in many but not all experimental systems. Although homotypic cell adhesion through the LFA-1/ICAM-1 dependent pathway was shown to be involved in certain types of CD40-mediated inhibition of sIgM-mediated negative signaling, it is still not known how the cytokines and CD40-mediated signaling inhibit sIgM-mediated B cell death. The molecular mechanisms responsible for sIgM-mediated negative signaling and for the inhibitory signaling against sIgM-mediated negative signaling need further elucidation.

Developmental changes of GM-CSF gene inducibility in embryonal carcinoma cells

Murine embryonal carcinoma (EC) P19 cells, a tissue culture model of early embryonic development, failed to produce cytokines, such as interleukin-3 (IL-3), IL-4, granulocytemacrophage colony stimulating factor (GM-CSF) and interferon-beta (IFN-beta) at the mRNA level. Differentiation induced by retinoic acid (RA) released this repression to produce some cytokines. GM-CSF and IFN-beta genes were expressed in response to PMA/A23187, poly(I):poly(C), IL-1 alpha, forskolin, or LPS stimulation in differentiated P19 cells, whereas IL-3 and IL-4 genes were not expressed. To elucidate the mechanism of the GM-CSF gene induction after differentiation, we transfected a series of 5' deletion mutants of the mouse GM-CSF promoter fused to the bacterial CAT gene. The 740-bp fragment of the 5'-flanking region mediated the positive response. Deletion analysis revealed that the 5' boundary region of the DNA element required for activation lies between positions -95 and -84 and the region upstream of position -95 appears inhibitory. These results indicate that the maturation of the transcriptional machinery after differentiation results in the activation of the GM-CSF gene.

Involvement of LFA-1/intracellular adhesion molecule-1-dependent cell adhesion in CD40-mediated inhibition of human B lymphoma cell death induced by surface IgM crosslinking

B cells have been shown to receive negative signals for their growth through crosslinking of surface IgM (sIgM), and it has been demonstrated that anti-IgM Abs induce B cell death. Proliferation of B cells in response to Ag stimulation in vivo may thus require additional signals that inhibit the sIgM-transduced negative signals. Signaling through CD40 has been proposed as a candidate for such costimulatory signals. To investigate the role of CD40-transduced signals in sIgM-mediated B cell death, we used a human B cell line (DND-39) that expresses sIgM, sIgD, and CD40. Crosslinking of sIgM, but not sIgD, by Abs induced DND-39 cell death. The dying cells showed the morphology of apoptosis and DNA fragmentation. Anti-CD40 Abs induced homotypic adhesion of DND-39 cells and rescued them from anti-IgM Ab-induced cell death. Anti-CD40 Abs inhibited anti-IgM Ab-induced cell death when added within 3 h after stimulation with anti-IgM Ab. Treatment with Abs against CD11a, CD18, or CD54 inhibited not only the homotypic adhesion but also the inhibition of anti-IgM Ab-induced apoptosis by anti-CD40 Ab. CD11a antisense decreased the surface CD11a expression, the anti-CD40 Ab-induced homotypic adhesion, and the inhibitory effect of anti-CD40 Ab on anti-IgM Ab-induced apoptosis. The data show that LFA-1/ICAM-1-dependent cell adhesion induced by signaling through CD40 plays an important role in the inhibition of anti-IgM Ab-induced apoptosis of DND-39 cells.

Involvement of LFA-1/intracellular adhesion molecule-1-dependent cell adhesion in CD40-mediated inhibition of human B lymphoma cell death induced by surface IgM crosslinking

B cells have been shown to receive negative signals for their growth through crosslinking of surface IgM (sIgM), and it has been demonstrated that anti-IgM Abs induce B cell death. Proliferation of B cells in response to Ag stimulation in vivo may thus require additional signals that inhibit the sIgM-transduced negative signals. Signaling through CD40 has been proposed as a candidate for such costimulatory signals. To investigate the role of CD40-transduced signals in sIgM-mediated B cell death, we used a human B cell line (DND-39) that expresses sIgM, sIgD, and CD40. Crosslinking of sIgM, but not sIgD, by Abs induced DND-39 cell death. The dying cells showed the morphology of apoptosis and DNA fragmentation. Anti-CD40 Abs induced homotypic adhesion of DND-39 cells and rescued them from anti-IgM Ab-induced cell death. Anti-CD40 Abs inhibited anti-IgM Ab-induced cell death when added within 3 h after stimulation with anti-IgM Ab. Treatment with Abs against CD11a, CD18, or CD54 inhibited not only the homotypic adhesion but also the inhibition of anti-IgM Ab-induced apoptosis by anti-CD40 Ab. CD11a antisense decreased the surface CD11a expression, the anti-CD40 Ab-induced homotypic adhesion, and the inhibitory effect of anti-CD40 Ab on anti-IgM Ab-induced apoptosis. The data show that LFA-1/ICAM-1-dependent cell adhesion induced by signaling through CD40 plays an important role in the inhibition of anti-IgM Ab-induced apoptosis of DND-39 cells.

Positive and negative signals transduced through surface immunoglobulins in human B cells

Cross-linking of surface IgM and surface IgD by anti-IgM antibodies and anti-IgD antibodies, respectively, showed different effects on the growth of normal human peripheral blood B cells and the human B lymphoma cell line, B104. Only cross-linking of surface IgM transduced signals that inhibited cell division of peripheral blood B cells and B104 cells at the G2/M interphase. In B104 cells, the inhibition of cell division was followed by rapid B104 cell death. The negative signals were inhibited by cyclosporin A and FK-506 at lower concentrations than those that inhibited proliferation of the B cells. Anti-IgM antibody-induced B104 cell death was dependent on Ca2+ influx and macromolecular synthesis. B104 cells treated with anti-IgM antibodies showed neither DNA fragmentation or morphology of apoptosis but showed DNA single-strand breaks and morphology of necrosis. Nicotinamide inhibited anti-IgM antibody-induced B104 cell death and the involvement of poly(adenosine diphosphate-ribosyl)ation was suggested in the process of the B104 cell death. With regard to the intracellular mechanisms responsible for the different signals, however, no qualitative difference was detected in putative signal transducers, including tyrosine phosphorylated protein, phosphatidyl inositol turnover, Ca2+ influx, activation of protein kinase C, and messenger ribonucleic acid expression of c-fos and Egr-1 when surface IgM and surface IgD were crosslinked. Further investigations of the mechanisms responsible for the different signals transduced through surface IgM and surface IgD will provide better understanding of immunodeficiencies and autoimmune diseases.

Effects of cyclic AMP on expression of LFA-1, Mac-1, and VLA-4 and eosinophilic differentiation of a human leukemia cell line, EoL-1

We examined the effect of dibutyryl cAMP (dbcAMP) on the expression of LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), and VLA-4 (CD49/CD29) and on eosinophilic differentiation of a human leukemia cell line, EoL-1. Dibutyryl cAMP induced eosinophilic differentiation of EoL-1 cells from 6-9 days after the start of culture with down-regulation of CD11a, CD18, and CD49 expression and up-regulation of CD11b expression. Changes in integrin expression, except for CD18, were seen predominantly in the fraction containing eosinophilic granule-positive cells, suggesting that the changes were dependent on eosinophilic differentiation. On the other hand, dbcAMP-induced changes of integrin expression were reversible and were not seen on day 9 when dbcAMP was removed on day 3, whereas eosinophilic differentiation was still present. A combination of G-CSF and TNF-alpha, which also induced eosinophilic differentiation of EoL-1 cells, increased CD11b expression slightly but had no significant effect on the expression of the other integrins. Butyrate and PMA up-regulated CD11b expression without eosinophilic differentiation. The results collectively suggest that the regulation of integrin expression on EoL-1 cells is partly dependent and partly not dependent on eosinophilic differentiation. The possible involvement of protein kinase A and protein kinase C in these changes is suggested.

Mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti-MHC class II antibodies

The mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti-MHC class II antibodies (Ab) were compared with those in anti-IgM Ab-induced B104 growth inhibition. Two anti-MHC class II Ab, L227 and 2.06, inhibited the growth of B104 cells, although 2.06, but not L227, needed to be further cross-linked with a goat anti-mouse IgG Ab (GAM) to show the effect. L227 induced an increase in intracellular free Ca2+ concentration ([Ca2+]i) from the intracellular pool and little or no protein tyrosine phosphorylation, phosphatidyl inositol turnover, or expression of Egr-1 mRNA, whereas 2.06 plus GAM induced an increase in [Ca2+]i from both the intracellular and, in particular, the extracellular pools. The inhibition of B104 cell growth induced by anti-MHC class II Ab was Ca(2+)-independent and not inhibited by actinomycin D or cyclosporin A, and cell cycle arrest at the G2/M interphase was not observed. These features are very different from those observed in B104 cell death induced by anti-IgM Ab. Neither DNA fragmentation nor the morphology of apoptosis was observed. These findings demonstrate that cross-linking of MHC class II molecules transduced the negative signals through intracellular mechanisms different from those present in the cross-linking of surface IgM.

Induction of eosinophilic granules, nonspecific esterase activity and CD14 expression in the human eosinophilic leukemia cell line, EOL-1

We examined the expression of eosinophilic granules, esterase activity and CD14 in a human eosinophilic cell line, EoL-1. Unstimulated EoL-1 cells were weakly positive for nonspecific esterase, but negative for surface CD14, and contained a few eosinophilic granule-positive cells. A combination of G-CSF and TNF-alpha increased the eosinophilic granule-containing cells, but failed to increase esterase activity or CD14 expression. IFN-gamma alone or in combination with TNF-alpha enhanced nonspecific esterase activity but failed to induce CD14 expression or increase eosinophilic granule-containing cells. dbcAMP increased eosinophilic granule-containing cells, nonspecific esterase activity and CD14 expression. Specific esterase activity was not detected in any circumstances. EoL-1 cells fractionated by density gradients or CD14 expression showed nonspecific esterase activity and CD14 expression in both the eosinophilic granule-positive and negative cell populations. Forskolin and butyrate had a synergistic effect on CD14 induction and protein kinase A was suggested to play a role in dbcAMP-induced CD14 expression. A protein kinase C activator, phorbol 12-myristate 13-acetate, did not increase eosinophilic granules, nonspecific esterase activity or CD14 expression in EoL-1 cells. The results show that EoL-1 cells can express nonspecific esterase and CD14, but the expression is not necessarily restricted to cells which have differentiated into the monocyte/macrophage lineage.

Molecular basis for developmental changes of GM-CSF gene inducibility in embryonal carcinoma cells

In a previous report, we reported that the induction of GM-CSF gene in differentiated P19 cells results from the maturation of the transcriptional machinery. Here, we identified a cis-DNA element which confers the activation of GM-CSF gene in response to PMA/A23187 stimulation in differentiated state. Analysis of the 5'-flanking region between -113 and -60 revealed two elements responsible for promotion and one for inhibition, and the overall effects led to the activation of GM-CSF gene mainly through the sequence between -95 and -73. Using the oligonucleotide between -94 and -73 as a probe in gel retardation assays, we identified a DNA-binding protein, NF-GM-P19, the binding activity of which was induced after differentiation in response to PMA/A23187 stimulation. These results indicate that the induction of GM-CSF gene after differentiation results from the maturation of the transcriptional machinery which recognizes the sequence between -95 and -73.

Induction of phosphatidylinositol turnover and EGR-1 mRNA expression by crosslinking of surface IgM and IgD in the human B cell line B104

We have previously shown that a human B lymphoma cell line, B104, expressed surface IgM (sIgM) and surface IgD (sIgD), and that crosslinking of sIgM and sIgD by anti-IgM antibody (Ab) and anti-IgD Ab, respectively, induced Ca2+ influx to almost the same degree, whereas only sIgM-crosslinking caused B104 cell death. Here, we investigated the accumulation of cyclic AMP (cAMP), the hydrolysis of inositol phosphates, protein kinase C (PKC) activity and the induction of Egr-1 and c-fos mRNA expression by sIgM- and sIgD-crosslinking to examine differences in the signals mediated through sIgM and sIgD in B104 cells. Both sIgM- and sIgD-crosslinking with antibodies induced elevation of cAMP levels, phosphatidylinositol turnover, PKC activation and expression of Egr-1 and c-fos mRNA, although sIgM-crosslinking was more effective than sIgD-crosslinking, presumably due to the higher expression of sIgM than of sIgD. Egr-1 mRNA expression induced by sIgM- and sIgD-crosslinking was inhibited by H7, erbstatin and genistein, but not by HA1004. Erbstatin and genistein inhibited the sIg-crosslinking-induced Egr-1 mRNA expression in a dose-dependent manner parallel to that observed in the inhibition of sIg-crosslinking-induced protein tyrosine phosphorylation. Phorbol myristate acetate induced Egr-1 mRNA expression but forskolin and dibutyryl cyclic AMP did not. These findings suggest that the Egr-1 mRNA activating signals through sIgM and sIgD are protein tyrosine kinase- and PKC-dependent, but protein kinase A-independent. Cyclosporin A (CsA) and FK506 rescued B104 cells from death induced by anti-IgM Ab, but did not affect the expression of Egr-1 and c-fos mRNA, showing that CsA and FK506 affect signal transducers differently from or downstream to these molecules. The difference in signals transduced through sIgM and sIgD in B104 cells is discussed.

Anti-Fas antibody induces different types of cell death in the human histiocytic cell line, U937, and the human B cell line, B104: the role of single-strand DNA breaks and poly (ADP-ribosyl)ation in cell death

We investigated the anti-Fas antibody-induced cell death in two different types of human cell lines, U937 and B104. IFN-gamma increased the surface expression of Fas antigen and susceptibility to anti-Fas Ab-induced cell death of B104 and U937 cells. Anti-Fas Ab-induced death of U937 and B104 cells required neither a Ca2+ influx nor macromolecular synthesis. U937 cells treated with anti-Fas Ab represented apoptosis with DNA fragmentation, whereas anti-Fas Ab-treated B104 cells did not. Single-strand DNA breaks, however, appeared in the B104 cells. Zinc ions prevented DNA fragmentation and the morphological features of apoptosis in anti-Fas Ab-treated U937 cells, but did not inhibit cell death. However, zinc ions, when used in combination with the poly(ADP-ribosyl)ation inhibitors, inhibited anti-Fas Ab-induced U937 cell death. The inhibitors by themselves did not inhibit anti-Fas Ab-induced U937 cell death, but did inhibit anti-Fas Ab-induced B104 cell death. A substantial decrease in NAD pools was observed in anti-Fas Ab-treated B104 and U937 cells in parallel with the increase of DNA strand breaks before cell death became apparent. These results suggest the involvement of single-strand DNA breaks and poly(ADP-ribosyl)ation in the mechanisms of anti-Fas Ab-induced U937 and B104 cell death.

Induction of phosphatidylinositol-linked Fc gamma receptor III expression on an eosinophilic cell line, EoL-1, by dibutyryl cyclic AMP and interferon-gamma

The expression of Fc gamma receptor III (Fc gamma RIII) on a human eosinophilic leukemia cell line, EoL-1, was examined and compared with its expression on normal blood eosinophils. Surface Fc gamma RIII expression on EoL-1 cells could be induced in vitro with a combination of dibutyryl cAMP (dbcAMP) and gamma-interferon (IFN-gamma), but not with IFN-gamma or dbcAMP alone. Pretreatment of EoL-1 cells with dbcAMP induced EoL-1 cells to express Fc gamma RIII when stimulated with IFN-gamma, but EoL-1 cells pretreated with IFN-gamma and then stimulated with dbcAMP failed to express Fc gamma RIII. Cyclic AMP was shown to play a role in the effect of dbcAMP. Both the treatment with phosphatidyl-inositol-specific phospholipase C (PI-PLC) and the restriction enzyme digestion of Fc gamma RIII cDNA showed that the Fc gamma RIII on EoL-1 cells was a phosphatidylinositol-linked form. On the other hand, freshly isolated blood eosinophils constitutively expressed few, if any, Fc gamma RIII, and IFN-gamma induced Fc gamma RIII expression on them in vitro. Dibutyryl cAMP did not induce Fc gamma RIII expression and even suppressed the IFN-gamma-induced Fc gamma RIII expression on normal eosinophils. The EoL-1 cell line appears to be a useful in vitro model for the expression and function of the phosphatidylinositol-linked form of Fc gamma RIII on eosinophils.

Tyrosine phosphorylation of IgM- and IgD-associated molecules of a human B lymphoma cell line B104

We investigated tyrosine phosphorylation and structural properties of the IgM-associated molecules in comparison with IgD-associated molecules in a recently established human surface IgM+, IgD+ B lymphoma cell line, B104, the growth of which was irreversibly inhibited by anti-IgM mAbs but not by anti-IgD mAbs. Tyrosine kinase activity and tyrosine phosphorylated proteins were detected in anti-IgM and anti-IgD immunoprecipitates from digitonin lysates of B104 cells with the use of an in vitro kinase assay followed by a re-immunoprecipitation experiment with anti-phosphotyrosine mAbs. Tyrosine phosphorylated proteins of 74, 58-44, 41, and 39 kDa were detected in anti-IgM immunoprecipitates, whereas tyrosine phosphorylated proteins of 74, 58-44, and 39 kDa, but not 41 kDa, were detected in anti-IgD immunoprecipitates. Crosslinking of surface IgM and surface IgD stimulated rapid tyrosine phosphorylation of different sets of proteins which included tyrosine-phosphorylated proteins of the same or similar molecular weights as those detected in the anti-IgM and anti-IgD immunoprecipitates respectively. After deglycosylation by N-glycosidase, both the IgM- and IgD-associated phosphoproteins (pp58-pp39) gave rise to the same three bands of 29, 27, and 26 kDa. Proteolytic peptide mapping of these three deglycosylated proteins showed that the primary structures of the IgM- and IgD-associated molecules are identical, suggesting that the IgM- and IgD-associated phosphoproteins (pp58-pp39) are the products of the same or closely related genes. One of the products, pp41, may be associated with IgM, but not with IgD, although the same gene product may be associated with IgD in a different glycosylation pattern.

Anti-IgM antibody-induced cell death in a human B lymphoma cell line, B104, represents a novel programmed cell death

We investigated the mechanisms of anti-IgM antibody-induced cell death in a recently established human surface IgM+ IgD+ B lymphoma cell line, B104, the growth of which is irreversibly inhibited by anti-IgM antibody but not by anti-IgD antibody, and compared it with the cell death of T cells via TCR/CD3 complex and with the cell death of a murine anti-IgM antibody-sensitive B lymphoma cell line, WEHI-231. The rapid time course of B104 cell death and its requirements for de novo macromolecular synthesis and Ca2+ influx suggest that anti-IgM antibody-induced B104 cell death is an active Ca(2+)-dependent programmed cell death. Moreover, cyclosporin A rescued B104 cells from this lethal signal, via surface IgM, suggesting that the intracellular mechanisms involved are quite similar to those of T cell death. DNA fragmentation, which has been reported in TCR/CD3 complex-mediated T cell death, apoptosis, was not involved in the B104 cell death process, but the possible involvement of DNA single-strand breaks was suggested. Observations under light microscopy and transmission electron microscopy indicated that the morphologic features of dying B104 cells resembled necrosis rather than apoptosis. B104 cell death was shown to be quite distinct from that of WEHI-231 in cell death kinetics, the mode of cell death, and the response to cyclosporin A. These data collectively indicate that the death of B104 cells resulting from surface IgM cross-linking represents a hitherto undefined mode of programmed cell death.

Anti-IgM antibody-induced cell death in a human B lymphoma cell line, B104, represents a novel programmed cell death

We investigated the mechanisms of anti-IgM antibody-induced cell death in a recently established human surface IgM+ IgD+ B lymphoma cell line, B104, the growth of which is irreversibly inhibited by anti-IgM antibody but not by anti-IgD antibody, and compared it with the cell death of T cells via TCR/CD3 complex and with the cell death of a murine anti-IgM antibody-sensitive B lymphoma cell line, WEHI-231. The rapid time course of B104 cell death and its requirements for de novo macromolecular synthesis and Ca2+ influx suggest that anti-IgM antibody-induced B104 cell death is an active Ca(2+)-dependent programmed cell death. Moreover, cyclosporin A rescued B104 cells from this lethal signal, via surface IgM, suggesting that the intracellular mechanisms involved are quite similar to those of T cell death. DNA fragmentation, which has been reported in TCR/CD3 complex-mediated T cell death, apoptosis, was not involved in the B104 cell death process, but the possible involvement of DNA single-strand breaks was suggested. Observations under light microscopy and transmission electron microscopy indicated that the morphologic features of dying B104 cells resembled necrosis rather than apoptosis. B104 cell death was shown to be quite distinct from that of WEHI-231 in cell death kinetics, the mode of cell death, and the response to cyclosporin A. These data collectively indicate that the death of B104 cells resulting from surface IgM cross-linking represents a hitherto undefined mode of programmed cell death.