Growth Of Hematopoietic Progenitor Cells Research Articles

Impaired in vitro growth of peripheral blood hematopoietic progenitor cells in HIV-infected patients: Evidence of an inhibitory effect of autologous T lymphocytes

The in vitro growth of both circulating granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) progenitor cells was assessed in 29 individuals infected with the human immunodeficiency virus (HIV) at different stages of infection. The effects of autologous T lymphocytes, adherent cells, and serum on the in vitro growth of hematopoietic progenitor cells were also investigated. Compared with normal controls, baseline growth was significantly reduced for both CFU-GM and BFU-E in HIV-infected patients, independent of the clinical stage of the disease. In HIV-infected subjects depletion of autologous T cells was associated with a significant increase of progenitor cell growth. Similar results were observed after selective depletion of CD8+ T cells, while readdition of T cells to T-depleted mononuclear cells reduced the number of CFU-GM. A dose-dependent colony inhibitory activity was found in conditioned medium of T cells from HIV-infected subjects. Neither autologous adherent cells nor serum from either HIV+ or HIV- subjects had any significant effect on the in vitro growth of CFU-GM. These results indicate that the in vitro growth of circulating hematopoietic progenitor cells is impaired even in the early stages of HIV infection, and that autologous T cells exert an inhibitory effect on the in vitro growth of progenitor cells, possibly via soluble mediator(s).

Interferon-γ Enhances Growth Factor-Dependent Proliferation of Clonogenic Cells in Acute Myeloblastic Leukemia

Abstract Interferon-gamma (IFN-gamma) has been reported to antagonize the stimulatory effect of various conditioned media on the growth of normal hematopoietic progenitor cells and clonogenic blasts from patients with chronic myelogenous leukemia (CML) and acute myeloblastic leukemia (AML). In the present study, using purified recombinant cytokines and homogenous cell populations, we provide evidence for a synergistic or additive effect of IFN-gamma with recombinant human (rhu) hematopoietic growth factors in the stimulation of clonogenic blasts from most AML patients examined. Under conditions of limiting cell concentration, rhuIFN-gamma alone showed little effect on blast proliferation, whereas in conjunction with recombinant human interleukin-3 (rhuIL-3), IFN- gamma significantly enhanced colony formation in 13 of 15 AML cases. Maximal stimulation was obtained at low concentrations of IFN-gamma (2 to 20 pmol/L) in four cases and at higher concentrations (700 to 7,000 pmol/L) in the remainder. IFN-gamma also synergized with recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) in 9 of 13 cases. Within 1 hour of exposure, IFN-gamma induced a twofold to fourfold accumulation of tumor necrosis factor alpha (TNF alpha)- specific transcripts in AML blasts and several AML cell lines that include HL-60 and OCI-AML 1. Further, the synergy between IFN-gamma and IL-3 on AML blasts was partially or completely abrogated by a TNF alpha neutralizing antibody, suggesting that growth enhancement by IFN-gamma may be mediated through TNF alpha production in AML blast culture. Exposure of normal precursors (burst-forming unit-erythroid [BFU-E] and colony-forming unit granulocyte-macrophage [CFU-GM]) to IFN-gamma also resulted in significant growth enhancement, suggesting that the proliferative response elicited by IFN-gamma was not limited to AML blasts. Finally, in M07-E, an IL-3-dependent human “megakaryoblastic” cell line, IFN-gamma also significantly enhanced IL-3-supported colony formation, much in the same way as in primary AML blasts. In contrast, IFN-gamma inhibited growth of all CSF-independent leukemic cell lines tested. This inhibition was partially alleviated by anti-TNF alpha antibody. In summary, our data indicate that IFN-gamma can enhance or antagonize cell proliferation, depending on the cell type. Further, TNF alpha appears to mediate the biologic effect of IFN-gamma either in growth stimulation or growth inhibition.

Stem cell factor induces proliferation and differentiation of highly enriched murine hematopoietic cells.

Recombinant rat stem cell factor (SCF) was studied for its ability to stimulate the growth of murine hematopoietic progenitor cells and to generate colony-forming cells (CFC) from highly enriched populations of hematopoietic cells. In serum-deprived cultures, SCF alone stimulated few colonies but interacted with a number of other hematopoietic growth factors, particularly interleukin 3, to promote colony formation. The most marked effect was on the generation of mixed-cell colonies. Hematopoietic cells were sorted into wheat-germ agglutinin-negative, monocyte-depleted, rhodamine 123 (Rh123)-bright or Rh123-dull cells. Historically, Rh123-bright cells are capable of short-term (less than 1 mo) marrow engraftment, whereas among Rh123-dull cells are cells capable of long-term marrow engraftment. Enriched cells (2.5 x 10(3) were placed into serum-deprived liquid cultures with various hematopoietic growth factors. Initially, the Rh123-bright and Rh123-dull cells had few CFC but, in the presence of interleukin 3 and SCF, Rh123-bright cells gave rise to greater than 15,000 granulocyte/macrophage CFC, greater than 1500 erythroid burst-forming cells, and greater than 700 mixed-cell CFC by day 5. In contrast, Rh123-dull cells proliferated only in the presence of interleukin 3 and SCF, but total cell numbers rose to a peak of 18,000 by day 21, and one-third of the cells were CFC. Thus, SCF, in combination with other growth factors, can generate large numbers of CFC from pre-CFC and appears to act earlier than hematopoietic growth factors described to date.

Interferon-gamma enhances growth factor-dependent proliferation of clonogenic cells in acute myeloblastic leukemia

Interferon-gamma (IFN-gamma) has been reported to antagonize the stimulatory effect of various conditioned media on the growth of normal hematopoietic progenitor cells and clonogenic blasts from patients with chronic myelogenous leukemia (CML) and acute myeloblastic leukemia (AML). In the present study, using purified recombinant cytokines and homogenous cell populations, we provide evidence for a synergistic or additive effect of IFN-gamma with recombinant human (rhu) hematopoietic growth factors in the stimulation of clonogenic blasts from most AML patients examined. Under conditions of limiting cell concentration, rhuIFN-gamma alone showed little effect on blast proliferation, whereas in conjunction with recombinant human interleukin-3 (rhuIL-3), IFN-gamma significantly enhanced colony formation in 13 of 15 AML cases. Maximal stimulation was obtained at low concentrations of IFN-gamma (2 to 20 pmol/L) in four cases and at higher concentrations (700 to 7,000 pmol/L) in the remainder. IFN-gamma also synergized with recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) in 9 of 13 cases. Within 1 hour of exposure, IFN-gamma induced a twofold to fourfold accumulation of tumor necrosis factor alpha (TNF alpha)-specific transcripts in AML blasts and several AML cell lines that include HL-60 and OCI-AML 1. Further, the synergy between IFN-gamma and IL-3 on AML blasts was partially or completely abrogated by a TNF alpha neutralizing antibody, suggesting that growth enhancement by IFN-gamma may be mediated through TNF alpha production in AML blast culture. Exposure of normal precursors (burst-forming unit-erythroid [BFU-E] and colony-forming unit granulocyte-macrophage [CFU-GM]) to IFN-gamma also resulted in significant growth enhancement, suggesting that the proliferative response elicited by IFN-gamma was not limited to AML blasts. Finally, in M07-E, an IL-3-dependent human "megakaryoblastic" cell line, IFN-gamma also significantly enhanced IL-3-supported colony formation, much in the same way as in primary AML blasts. In contrast, IFN-gamma inhibited growth of all CSF-independent leukemic cell lines tested. This inhibition was partially alleviated by anti-TNF alpha antibody. In summary, our data indicate that IFN-gamma can enhance or antagonize cell proliferation, depending on the cell type. Further, TNF alpha appears to mediate the biologic effect of IFN-gamma either in growth stimulation or growth inhibition.

Stimulation of granulopoiesis by transforming growth factor beta: synergy with granulocyte/macrophage-colony-stimulating factor.

Transforming growth factor beta 1 (TGF-beta 1) is known to inhibit the growth of immature hematopoietic progenitor cells, whereas more mature, lineage-restricted progenitors are not inhibited. In contrast, in the presence of saturating concentrations of granulocyte/macrophage-colony-stimulating factor (GM-CSF), TGF-beta promoted a 3- to 5-fold increase in the number and size (greater than 0.5 mm) of bone marrow colonies in a dose-dependent manner with an ED50 of 10-20 pM; TGF-beta 1 alone had no effect. Morphological examination showed an increase in granulocyte colonies. In suspension cultures, TGF-beta 1 and GM-CSF stimulated an increase in total viable cells with markedly enhanced neutrophilic differentiation and a concomitant decrease in the number of monocytes/macrophages by day 6 in culture. Limiting dilution analysis demonstrated a 2- to 5-fold increase in the frequency of progenitor cells that responded to GM-CSF plus TGF-beta 1 vs. GM-CSF alone. Bone marrow progenitors obtained from mice 3 days after treatment with 5-fluorouracil responded to a combination of GM-CSF and TGF-beta 1, whereas either factor alone had no effect. A single-cell assay identified a progenitor cell that directly responded to TGF-beta and GM-CSF. TGF-beta increased the number of GM-CSF receptors on bone marrow cells. Thus, TGF-beta 1 can act as a bifunctional mediator of hematopoietic cell growth, and TGF-beta 1 and GM-CSF act together to stimulate granulopoiesis as measured by large granulocyte colony formation; the progenitor cell is tentatively designated granulocyte burst-forming unit.

Effect of murine mast cell growth factor (c-kit proto-oncogene ligand) on colony formation by human marrow hematopoietic progenitor cells

Purified natural (n) and recombinant (r) murine (mu) mast cell growth factor (MGF, a c-kit ligand) were evaluated alone and in combination with r human (hu) erythropoietin (Epo), rhu granulocyte-macrophage colony-stimulating factor (rhuGM-CSF), rhuG-CSF, and/or rhuM-CSF for effects in vitro on colony formation by multipotential (colony-forming unit-granulocyte, erythroid, monocyte, megakaryocyte [CFU-GEMM]), erythroid (burst-forming unit erythroid [BFU-E]) and granulocyte- macrophage (CFU-GM) progenitor cells from normal human bone marrow. MGF was a potent enhancing cytokine for Epo-dependent CFU-GEMM and BFU-E colony formation, stimulating more colonies and of a larger size than either rhu interleukin-3 (rhuIL-3) or rhuGM-CSF. MGF, especially at lower concentrations, also acted with rhuIL-3 or rhuGM-CSF to enhance Epo-dependent CFU-GEMM and BFU-E colony formation. MGF had little stimulating activity for CFU-GM colonies by itself, but in combination with suboptimal to optimal amounts of rhuGM-CSF enhanced the numbers and the size of CFU-GM colonies in an additive to greater than additive manner. While we did not detect an effect of MGF on CFU-G colony numbers stimulated by maximal concentrations of rhuG-CSF, MGF did enhance the size of CFU-G-derived colonies. MGF did not enhance the activity of rhuM-CSF. In a comparative assay, maximal concentrations of rmu and rhuMGF were equally effective in the enhancement of human bone marrow colony formation, but rhuMGF, in contrast to rmuMGF, did not at the concentrations tested enhance colony formation by mouse bone marrow cells. MGF effects on BFU-E, CFU-GM, and CFU-GEMM may be direct acting ones as MGF-enhanced colony formation by these cells in highly enriched progenitor cell populations of CD34 HLA-DR+ and CD34 HLA-DR+CD33- sorted cells in which greater than or equal to 1 of 2 cells was a BFU-E plus CFU-GM plus CFU-GEMM. MGF appears to be an early acting cytokine that preferentially stimulates the growth of immature hematopoietic progenitor cells.

Synergistic effect of recombinant interferon-gamma and interleukin-3 on the growth of immature human hematopoietic progenitors

Purified peripheral blood hematopoietic progenitors from children in early remission from cancer respond to recombinant human interleukin-3 (IL-3), but not to granulocyte colony-stimulating factor (G-CSF). With these purified cells as a target, we studied the effect of recombinant human interferon-gamma (IFN-gamma) on progenitor growth, using both liquid-suspension limiting dilution assay (LDA) and regular methylcellulose culture of progenitors. We found that in LDA with IL-3, IFN-gamma directly stimulated the growth of blood progenitors in a dose- dependent manner with single-hit kinetics, whereas IFN-gamma suppressed the growth of G-CSF-supported progenitors obtained from bone marrow. The stimulatory effect was also observed in methylcellulose culture, but the addition of antibodies for G-CSF, granulocyte-macrophage CSF, IL-1 alpha, IL-1 beta, IL-6, or tumor necrosis factor did not result in a decrease of the colony number, supporting further the possible direct effect of IFN-gamma on progenitor growth. These results suggest that the inhibitory effect of IFN-gamma on hematopoietic progenitors is limited to those in an advanced stage of maturation. IFN-gamma may be one of the essential lymphokines upregulating the growth of human hematopoietic progenitor cells.

Effect of Murine Mast Cell Growth Factor (c-kit Proto-Oncogene Ligand) on Colony Formation by Human Marrow Hematopoietic Progenitor Cells

Purified natural (n) and recombinant (r) murine (mu) mast cell growth factor (MGF, a c-kit ligand) were evaluated alone and in combination with r human (hu) erythropoietin (Epo), rhu granulocyte-macrophage colony-stimulating factor (rhuGM-CSF), rhuG-CSF, and/or rhuM-CSF for effects in vitro on colony formation by multipotential (colony-forming unit-granulocyte, erythroid, monocyte, megakaryocyte [CFU-GEMM]), erythroid (burst-forming unit erythroid [BFU-E]) and granulocyte-macrophage (CFU-GM) progenitor cells from normal human bone marrow. MGF was a potent enhancing cytokine for Epo-dependent CFU-GEMM and BFU-E colony formation, stimulating more colonies and of a larger size than either rhu interleukin-3 (rhulL-3) or rhuGM-CSF. MGF, especially at lower concentrations, also acted with rhulL-3 or rhuGM-CSF to enhance Epo-dependent CFU-GEMM and BFU-E colony formation. MGF had little stimulating activity for CFU-GM colonies by itself, but in combination with suboptimal to optimal amounts of rhuGM-CSF enhanced the numbers and the size of CFU-GM colonies in an additive to greater than additive manner. While we did not detect an effect of MGF on CFU-G colony numbers stimulated by maximal concentrations of rhuG-CSF, MGF did enhance the size of CFU-G–derived colonies. MGF did not enhance the activity of rhuM-CSF. In a comparative assay, maximal concentrations of rmu and rhuMGF were equally effective in the enhancement of human bone marrow colony formation, but rhuMGF, in contrast to rmuMGF, did not at the concentrations tested enhance colony formation by mouse bone marrow cells. MGF effects on BFU-E, CFU-GM, and CFU-GEMM may be direct acting ones as MGF-enhanced colony formation by these cells in highly enriched progenitor cell populations of CD34+++HLA-DR+ and CD34+++HLA-DR+CD33− sorted cells in which ⩾ 1 of 2 cells was a BFU-E plus CFU-GM plus CFU-GEMM. MGF appears to be an early acting cytokine that preferentially stimulates the growth of immature hematopoietic progenitor cells.

Synergistic Effect of Recombinant Interferon-γ and Interleukin-3 on the Growth of Immature Human Hematopoietic Progenitors

Purified peripheral blood hematopoietic progenitors from children in early remission from cancer respond to recombinant human interleukin-3 (IL-3), but not to granulocyte colony-stimulating factor (G-CSF). With these purified cells as a target, we studied the effect of recombinant human interferon-γ (IFN-γ) on progenitor growth, using both liquid-suspension limiting dilution assay (LDA) and regular methylcellulose culture of progenitors. We found that in LDA with IL-3, IFN-γ directly stimulated the growth of blood progenitors in a dose-dependent manner with single-hit kinetics, whereas IFN-γ suppressed the growth of G-CSF–supported progenitors obtained from bone marrow. The stimulatory effect was also observed in methylcellulose culture, but the addition of antibodies for G-CSF, granulocyte-macrophage CSF, IL-1α, IL-1β, IL-6, or tumor necrosis factor did not result in a decrease of the colony number, supporting further the possible direct effect of IFN-γ on progenitor growth. These results suggest that the inhibitory effect of IFN-γ on hematopoietic progenitors is limited to those in an advanced stage of maturation. IFN-γ may be one of the essential lymphokines upregulating the growth of human hematopoietic progenitor cells.

Transforming growth factor-beta trans-modulates the expression of colony stimulating factor receptors on murine hematopoietic progenitor cell lines

Transforming growth factor beta (TGF-beta) is a potent and selective growth inhibitor of early hematopoietic progenitors and leukemic cells. The cellular mechanism(s) underlying this antiproliferative effect is, however, currently unknown. In the present study, we demonstrate that TGF-beta inhibits the expression of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3), and granulocyte-CSF (G-CSF) receptors on murine factor-dependent and independent hematopoietic progenitor cell lines without a significant change in receptor affinity. A maximum reduction in GM-CSF receptor numbers of 65% to 77% was observed by 96-hour incubation with TGF-beta. The TGF- beta induced trans-down-modulation of GM-CSF receptors was prolonged, noncytotoxic but reversible, and not due to endogenous production of GM- CSF. The TGF-beta induced reduction in CSF receptor numbers preceded TGF-beta's growth inhibitory action. In addition, the ED50 (1 to 10 pmol/L) for TGF-beta's CSF receptor modulatory and antiproliferative effect was similar. The effect of TGF-beta on cell surface CSF receptor expression was specific, because the expression of other cell surface proteins (Ly 5 and Ly 17) was not affected by TGF-beta treatment, and because other growth inhibitors (tumor necrosis factor and interferon) did not affect CSF receptor expression. These data suggest that the downregulation of the growth of hematopoietic progenitor cells by TGF- beta involves reducing the cell surface expression on growth factor receptors.

Transforming Growth Factor-β Trans-Modulates the Expression of Colony Stimulating Factor Receptors on Murine Hematopoietic Progenitor Cell Lines

AbstractTransforming growth factor beta (TGF-β) is a potent and selective growth inhibitor of early hematopoietic progenitors and leukemic cells. The cellular mechanism(s) underlying this antiproliferative effect is, however, currently unknown. In the present study, we demonstrate that TGF-β inhibits the expression of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3), and granulocyte-CSF (G-CSF) receptors on murine factor-dependent and independent hematopoietic progenitor cell lines without a significant change in receptor affinity. A maximum reduction in GM-CSF receptor numbers of 65% to 77% was observed by 96-hour incubation with TGF-β. The TGF-β induced trans-down-modulation of GM-CSF receptors was prolonged, noncyto-toxic but reversible, and not due to endogenous production of GM-CSF. The TGF-β induced reduction in CSF receptor numbers preceded TGF-β's growth inhibitory action. In addition, the ED50 (1 to 10 pmol/L) for TGF-β's CSF receptor modulatory and antiproliferative effect was similar. The effect of TGF-β on cell surface CSF receptor expression was specific, because the expression of other cell surface proteins (Ly 5 and Ly 17) was not affected by TGF-β treatment, and because other growth inhibitors (tumor necrosis factor and interferon) did not affect CSF receptor expression. These data suggest that the downregulation of the growth of hematopoietic progenitor cells by TGF-β involves reducing the cell surface expression of growth factor receptors.

Identification of Functionally Distinct Domains of Human Granulocyte-Macrophage Colony-Stimulating Factor Using Monoclonal Antibodies

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein that is required for the survival, growth, and differentiation of hematopoietic progenitor cells. Although the primary structure of GM-CSF is known from cDNA cloning, the relationship between structure and function of GM-CSF is not fully understood. Fifteen different monoclonal antibodies (MoAbs) to human GM-CSF were generated to map immunologically distinct areas of the molecule. Each of the MoAbs was biotinylated and shown by enzyme-linked immunosorbent assay to bind to recombinant GM-CSF that had been affixed to a solid phase. Each of the 15 unconjugated MoAbs was then used to compete with each biotinylated MoAb for binding to GM-CSF. These cross-blocking studies identified eight distinct epitopes of native GM-CSF. Seven of these epitopes were also present in denatured GM-CSF by Western blotting, and four of the epitopes were at least partially conserved on GM-CSF that was reduced in beta-mercaptoethanol. MoAbs to four of eight epitopes neutralized both recombinant (glycosylated and nonglycosylated) and natural human GM-CSF in a GM colony-forming unit (CFU-GM) assay and blocked GM-CSF-induced activation of neutrophils. For most of the antibodies there was a good correlation between neutralizing activity and the capacity to block binding of 125I-GM-CSF to neutrophils or blasts. Non-neutralizing antibodies to one epitope partially blocked binding of 125I-GM-CSF to neutrophils. None of the MoAbs neutralized interleukin-3, G-CSF, or M-CSF. The locations of seven of the epitopes could be partially mapped with regard to the amino acid structure by determining reactivity to GM-CSF synthetic peptides or to human-mouse chimeric GM-CSFs. The neutralizing antibodies were found to map to amino acids 40-77, 78-94, or 110-127. Thus, these MoAbs are useful to identify functional domains of GM-CSF and in identifying regions that are likely to be involved in receptor interaction.

Identification of functionally distinct domains of human granulocyte- macrophage colony-stimulating factor using monoclonal antibodies

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein that is required for the survival, growth, and differentiation of hematopoietic progenitor cells. Although the primary structure of GM-CSF is known from cDNA cloning, the relationship between structure and function of GM-CSF is not fully understood. Fifteen different monoclonal antibodies (MoAbs) to human GM-CSF were generated to map immunologically distinct areas of the molecule. Each of the MoAbs was biotinylated and shown by enzyme-linked immunosorbent assay to bind to recombinant GM-CSF that had been affixed to a solid phase. Each of the 15 unconjugated MoAbs was then used to compete with each biotinylated MoAb for binding to GM-CSF. These cross-blocking studies identified eight distinct epitopes of native GM-CSF. Seven of these epitopes were also present in denatured GM-CSF by Western blotting, and four of the epitopes were at least partially conserved on GM-CSF that was reduced in beta-mercaptoethanol. MoAbs to four of eight epitopes neutralized both recombinant (glycosylated and nonglycosylated) and natural human GM-CSF in a GM colony-forming unit (CFU-GM) assay and blocked GM-CSF-induced activation of neutrophils. For most of the antibodies there was a good correlation between neutralizing activity and the capacity to block binding of 125I-GM-CSF to neutrophils or blasts. Non-neutralizing antibodies to one epitope partially blocked binding of 125I-GM-CSF to neutrophils. None of the MoAbs neutralized interleukin-3, G-CSF, or M-CSF. The locations of seven of the epitopes could be partially mapped with regard to the amino acid structure by determining reactivity to GM-CSF synthetic peptides or to human-mouse chimeric GM-CSFs. The neutralizing antibodies were found to map to amino acids 40–77, 78–94, or 110–127. Thus, these MoAbs are useful to identify functional domains of GM-CSF and in identifying regions that are likely to be involved in receptor interaction.

Regulation of c-jun expression and AP-1 enhancer activity by granulocyte-macrophage colony-stimulating factor.

Granulocyte-macrophage colony stimulating factor (GM-CSF) stimulates the growth and differentiation of human hematopoietic progenitor cells by activating transcription of specific genes. The mechanism by which binding of GM-CSF to its receptor stimulates gene expression remains unknown. To examine this process in more detail, we have transfected human monocytic leukemia cells U937 with a plasmid containing an AP-1 enhancer element and a chloramphenicol acetyltransferase recorder gene and treated them with GM-CSF. We find that GM-CSF stimulates a 2-3-fold increase in chloramphenicol acetyltransferase activity over a concentration range 1-1,000 units/ml. Northern and Western blot analysis demonstrates that the mechanism by which GM-CSF stimulates AP-1 enhancer activity involves increases in c-jun and c-fos mRNA levels, and increases in Jun protein. In a similar fashion the treatment of normal human monocytes with GM-CSF also induced increases in total cellular c-jun. Because protein kinase C plays a crucial role in activating c-jun transcription we examined the role of this enzyme in mediating the effects of GM-CSF. Treatment of U937 cells with inhibitors of protein kinase C including staurosporine 10 nM and H-7 50 microM, or down-regulation of protein kinase C by phorbol ester pretreatment blocks the induction of c-jun by GM-CSF. However, HA which does not block protein kinase C had no effect on GM-CSF stimulation of c-jun RNA levels. In addition, GM-CSF treatment causes the rapid translocation of protein kinase C to the particulate fraction which was maximal by 5 min and returned to base line by 80 min. These data suggest that the binding of GM-CSF to its receptor stimulates increases in c-jun mRNA and protein and activates AP-1 enhancer activity. These effects may be at least in part mediated by activation of protein kinase C.

Lack of Evidence for Infection of or Effect on Growth of Hematopoietic Progenitor Cells After In Vivo or In Vitro Exposure to Human Immunodeficiency Virus

AbstractThe pathogenesis of the hematologic abnormalities commonly observed in patients with acquired immunodeficiency syndrome (AIDS) is incompletely understood. We report here that in vitro growth of myeloid (CFU-GM) and erythroid (BFU-E) progenitor cells from six patients with AIDS was not significantly different from that of normal human immunodeficiency virus (HIV) seronegative donors: 25.3 ± 5 CFU-GM per 5 × 104 low density marrow cells and 33.5 ± 5 BFU-E were observed in AIDS patients versus 32.7 ± 5 CFU-GM and 42.1 ± 5 BFU-E in controls. Furthermore, no HIV-DNA in individual colonies (CFU-GM and BFU-E) could be detected using the polymerase chain reaction (PCR) technique, although HIV-1 DNA was detected in peripheral blood mononuclear cells from the same patients. Similarly, normal bone marrow cells exposed in vitro to different isolates of HIV or recombinant purified HIV-1 envelope glycoprotein (gp) 120 did not exhibit any difference in growth of CFU-GM or BFU-E as compared with mock exposed bone marrow cells. HIV-1 DNA could not be detected by the PCR technique in individual colonies derived from HIV exposed marrow. This study suggests that committed myeloid and erythroid progenitors from AIDS patients are responsive to hematopoietic growth factors in vitro and do not appear to contain HIV-1 DNA. Also, HIV or its envelope gp did not alter the growth of hematopoietic progenitor cells in vitro. No evidence of HIV infection of progenitor cells could be demonstrated. Impaired hematopoiesis in patients with AIDS may not be related to direct effects of HIV on committed progenitor cells.

Lack of evidence for infection of or effect on growth of hematopoietic progenitor cells after in vivo or in vitro exposure to human immunodeficiency virus

The pathogenesis of the hematologic abnormalities commonly observed in patients with acquired immunodeficiency syndrome (AIDS) is incompletely understood. We report here that in vitro growth of myeloid (CFU-GM) and erythroid (BFU-E) progenitor cells from six patients with AIDS was not significantly different from that of normal human immunodeficiency virus (HIV) seronegative donors: 25.3 +/- 5 CFU-GM per 5 x 10(4) low density marrow cells and 33.5 +/- 5 BFU-E were observed in AIDS patients versus 32.7 +/- 5 CFU-GM and 42.1 +/- 5 BFU-E in controls. Furthermore, no HIV-DNA in individual colonies (CFU-GM and BFU-E) could be detected using the polymerase chain reaction (PCR) technique, although HIV-1 DNA was detected in peripheral blood mononuclear cells from the same patients. Similarly, normal bone marrow cells exposed in vitro to different isolates of HIV or recombinant purified HIV-1 envelope glycoprotein (gp) 120 did not exhibit any difference in growth of CFU-GM or BFU-E as compared with mock exposed bone marrow cells. HIV- 1 DNA could not be detected by the PCR technique in individual colonies derived from HIV exposed marrow. This study suggests that committed myeloid and erythroid progenitors from AIDS patients are responsive to hematopoietic growth factors in vitro and do not appear to contain HIV- 1 DNA. Also, HIV or its envelope gp did not alter the growth of hematopoietic progenitor cells in vitro. No evidence of HIV infection of progenitor cells could be demonstrated. Impaired hematopoiesis in patients with AIDS may not be related to direct effects of HIV on committed progenitor cells.

Reversal of Azidothymidine-Induced Bone Marrow Suppression by 2′,3′-Dideoxythymidine as Studied by Hemopoietic Clonal Culture

The hematological toxicity of the antiviral drug azidothymidine (AZT) was studied in vitro by measuring the cell growth of hematopoietic progenitor cells obtained from normal bone marrow. AZT inhibited the growth of granulocyte-macrophage (CFU-GM) and early and late erythroid (BFU-E and CFU-E) progenitors in a dose-dependent manner. The hemopoietic inhibition of AZT was significantly reduced by the addition of 2',3'-dideoxythymidine (2',3'-ddT). The results suggest that 2',3'-ddT may be of potential value in reducing AZT toxicity.

Human P40 T-cell growth factor (interleukin-9) supports erythroid colony formation

Because human P40 T-cell growth factor, tentatively designated interleukin-9 (IL-9), was isolated through its ability to stimulate a human IL-3-dependent leukemic cell line (M-O7E), we tested the ability of IL-9 to support the growth and differentiation of normal hematopoietic progenitor cells from peripheral blood and bone marrow. Although the M-O7E cell line was derived from a patient with megakaryoblastic leukemia, IL-9 has not proved to be a growth or maturation factor for megakaryocytes, but instead has proved to be effective in supporting the development of erythroid bursts (BFU-E) in cultures supplemented with erythropoietin. Using highly purified progenitors from peripheral blood, IL-3 showed a BFU-E plating efficiency of 46% compared with 20% for IL-9. Because of the purity of these cell preparations and the low cell density in culture, IL-9 is likely to interact directly with erythroid progenitors. Analysis of mixing experiments and of the morphology of the BFU-E in culture indicated that IL-9 interacts preferentially with a relatively early population of IL-3-responsive BFU-E. In cultures of human bone marrow or cord blood, IL-9 selectively supported erythroid colony formation, while IL-3 and granulocyte/macrophage colony-stimulating factor additionally yielded granulocyte/macrophage colonies. Therefore, IL-9 represents a new T cell-derived cytokine with the potential for selectively stimulating erythroid development in the hematopoietic system.

A role for calmodulin in the growth of human hematopoietic progenitor cells

A possible role for calmodulin in the colony growth of human hematopoietic progenitor cells was investigated using pharmacologic approaches. We obtained evidence for a dose-dependent inhibition of colony formation of myeloid progenitor cells (CFU-C) stimulated by interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte CSF (G-CSF) by three calmodulin antagonists, N- (6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), N- (4-aminobutyl)-5-chloro-2-naphthalenesulfonamide hydrochloride (W-13), and trifluoperazine. Chlorine-deficient analogs of W-7 and W-13, with a lower affinity for calmodulin, did not inhibit the growth of CFU-C colonies. W-7, W-13, and trifluoperazine inhibited the colony formation of immature erythroid progenitor cells (BFU-E) stimulated by IL-3 plus erythropoietin (Ep) or GM-CSF plus Ep, in a dose-dependent manner, while they did not affect the colony formation of mature erythroid progenitor cells (CFU-E) induced by Ep. W-7, W-13, and trifluoperazine also led to a dose-dependent inhibition of GM-CSF-induced colony formation of KG-1 cells. Calmodulin-dependent kinase activity derived from the KG-1 cells was inhibited by these three calmodulin antagonists in a dose-dependent manner. These data suggest that calmodulin may play an important regulatory role via a common process in the growth of hematopoietic progenitor cells stimulated by IL-3, GM-CSF, and G-CSF. Mechanisms related to the growth signal of Ep apparently are not associated with calmodulin-mediated systems.

A Role for Calmodulin in the Growth of Human Hematopoietic Progenitor Cells

A possible role for calmodulin in the colony growth of human hematopoietic progenitor cells was investigated using pharmacologic approaches. We obtained evidence for a dose-dependent inhibition of colony formation of myeloid progenitor cells (CFU-C) stimulated by interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte CSF (G-CSF) by three calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide hydrochloride (W-13), and trifluoperazine. Chlorine-deficient analogs of W-7 and W-13, with a lower affinity for calmodulin, did not inhibit the growth of CFU-C colonies. W-7, W-13, and trifluoperazine inhibited the colony formation of immature erythroid progenitor cells (BFU-E) stimulated by IL-3 plus erythropoietin (Ep) or GM-CSF plus Ep, in a dose-dependent manner, while they did not affect the colony formation of mature erythroid progenitor cells (CFU-E) induced by Ep. W-7, W-13, and trifluoperazine also led to a dose-dependent inhibition of GM-CSF-induced colony formation of KG-1 cells. Calmodulin-dependent kinase activity derived from the KG-1 cells was inhibited by these three calmodulin antagonists in a dose-dependent manner. These data suggest that calmodulin may play an important regulatory role via a common process in the growth of hematopoietic progenitor cells stimulated by IL-3, GM-CSF, and G-CSF. Mechanisms related to the growth signal of Ep apparently are not associated with calmodulin-mediated systems.