Control of granulocytes and macrophages: molecular, cellular, and clinical aspects

Effects of aflatoxin B1 and T-2 toxin on the granulocyte-macrophage progenitor cells in mouse bone marrow cultures

Myelotoxic effects of aflatoxin B1 (AFB1) and T-2 toxin on the proliferation of the granulocyte-macrophage progenitor cells to granulocyte, macrophage and granulocyte-macrophage (GM) colonies were investigated in male CD-1 mice by a semisolid in vitro culture technique. Mice received 0, 0.03, 0.145 and 0.7 mg/kg or 0, 0.1, 0.5, and 2.5 mg/kg body weight of AFB1 and T-2 toxin, respectively, for 2 weeks on alternate days. Granulocyte, macrophage, and GM-colonies were suppressed in the group that received the highest dose of AFB1 (0.7 mg/kg body weight). Treatment with T-2 toxin activated granulocyte colonies at 0.5 mg/kg and macrophage colonies at 0.1 and 2.5 mg/kg but suppressed GM-colonies at 0.5 and 2.5 mg/kg body weight. Bone marrow cells from normal CD-1 mice were cultured with different concentrations of AFB1 (1-50 microM) or T-2 toxin (1-10 nM) in vitro. Significant activation of granulocyte colonies with 1 microM AFB1 and suppression of all three types of colonies with the highest concentration of AFB1 (50 microM) were observed. The suppression of granulocyte and GM-colonies associated with T-2 toxin was concentration-dependent. The greatest suppression occurred in macrophage colonies with three highest concentrations of T-2 toxin (3, 6, and 10 nM). Results suggest that AFB1 is myelotoxic both in vivo and in vitro, whereas T-2 toxin is more toxic in vitro.

The receptor for interleukin 3 is selectively induced in human endothelial cells by tumor necrosis factor alpha and potentiates interleukin 8 secretion and neutrophil transmigration

Interleukin (IL)-3 stimulates hemopoiesis in vitro. However, IL-3 is not normally found in bone marrow, raising doubts as to the in vivo role of IL-3. We have found that human umbilical vein endothelial cells (HUVEC) express functional high-affinity receptors for IL-3 after stimulation with tumor necrosis factor alpha (TNF-alpha), IL-1 beta, or lipopolysaccharide, and that this receptor is involved in inflammatory phenomena. TNF-alpha caused time- and dose-dependent up-regulation of mRNA for the IL-3 receptor alpha and beta chains, with maximal effects occurring 16-36 h after stimulation with TNF-alpha at 100 units/ml. Induction of mRNA correlated with protein expression on the cell surface as judged by monoclonal antibody staining and by the ability of HUVEC to specifically bind 125I-labeled IL-3. Scatchard analysis under optimal conditions of TNF-alpha stimulation revealed approximately 1500 IL-3 receptors per cell, which were of a high-affinity class (Kd = 500 pM) only. In contrast to a previous report, receptors for granulocyte-macrophage colony-stimulating factor could not be detected. IL-3 binding to TNF-alpha-activated HUVEC enhanced IL-8 production, E-selection expression, and neutrophil transmigration. The selective induction of a functional IL-3 receptor on endothelial cells suggests that, beyond hemopoiesis, IL-3 may have an important role in chronic inflammation and in allergic diseases.

Distinct cytoplasmic regions of the human granulocyte colony-stimulating factor receptor involved in induction of proliferation and maturation

The granulocyte colony-stimulating factor receptor (G-CSF-R) transduces signals important for the proliferation and maturation of myeloid progenitor cells. To identify functionally important regions in the cytoplasmic domain of the G-CSF-R, we compared the actions of the wild-type receptor, two mutants, and a natural splice variant in transfectants of the mouse pro-B cell line BAF3 and two myeloid cell lines, 32D and L-GM. A region of 55 amino acids adjacent to the transmembrane domain was found to be sufficient for generating a growth signal. The immediate downstream sequence of 30 amino acids substantially enhanced the growth signaling in the three cell lines. In contrast, the carboxy-terminal part of 98 amino acids strongly inhibited growth signaling in the two myeloid cell lines but not in BAF3 cells. Truncation of this region lead to an inability of the G-CSF-R to transduce maturation signals in L-GM cells. An alternative carboxy tail present in a splice variant of the G-CSF-R also inhibited growth signaling, notably in both the myeloid cells and BAF3 cells, but appeared not to be involved in maturation.

Membrane-anchored proteoglycans of mouse macrophages: P388D1 cells express a syndecan-4-like heparan sulfate proteoglycan and a distinct chondroitin sulfate form

Proteoglycan accumulation by thioglycollate-elicited mouse peritoneal macrophages and a panel of murine monocyte-macrophage cell lines has been examined to determine whether these cells express plasma membrane-anchored heparan sulfate proteoglycans. Initially, cells were screened for heparan sulfate and chondroitin sulfate glycosaminoglycans after metabolic labeling with radiosulfate. Chondroitin sulfate is secreted to a variable extent by every cell type examined. In contrast, heparan sulfate is all but absent from immature pre-monocytes and is associated predominantly with the cell layer of mature macrophage-like cells. In the P388D1 cell line, the cell-associated chondroitin sulfate is largely present as a plasma membrane-anchored proteoglycan containing a 55 kD core protein moiety, which appears to be unique. In contrast, the cell-associated heparan sulfate is composed of a proteoglycan fraction and protein-free glycosaminoglycan chains, which accumulate intracellularly. A fraction of the heparan sulfate proteoglycan contains a lipophilic domain and can be released from cells following mild treatment with trypsin, suggesting that it is anchored in the plasma membrane. Isolation of this proteoglycan indicates that it is likely syndecan-4: it is expressed as a heparan sulfate proteoglycan at the cell surface, it is cleaved from the plasma membrane by low concentrations of trypsin, and it consists of a single 37 kD core protein moiety that co-migrates with syndecan-4 isolated from NMuMG mouse mammary epithelial cells. Northern analysis reveals that a panel of macrophage-like cell lines accumulate similar amounts of syndecan-4 mRNA, demonstrating that this proteoglycan is expressed by a variety of mature macrophage-like cells. Syndecan-1 mRNA is present only in a subset of these cells, suggesting that the expression of this heparan sulfate proteoglycan may be more highly regulated by these cells.

Novel role of interleukin 7 in myelopoiesis: stimulation of primitive murine hematopoietic progenitor cells

Interleukin 7 (IL-7) has been demonstrated to be an important regulator of the growth of B and T cell precursors as well as mature T cells, whereas IL-7 has been reported to have no direct myeloproliferative effects. Here we show that IL-7 potently and directly enhances colony stimulating factor-induced myeloid colony formation from Lin-Sca-1+ murine bone marrow progenitor cells, increasing the cloning frequency up to ninefold and cell numbers up to 50-fold, without affecting their ability to differentiate along the myeloid lineages In contrast, IL-7 has no effect on proliferation of committed Lin- myeloid progenitors. Thus, in addition to its established lymphopoietic potential, this study implicates a novel role of IL-7 in early myelopoiesis.

Photofrin, but not benzoporphyrin derivative, stimulates hematopoiesis in the mouse

This report describes the effects of the porphyrin photosensitizers, Photofrin and benzoporphyrin derivative (BPD) on the immunohematopoietic system of normal and immunosuppressed DBA/2 mice in the absence of activating light. Photofrin (10 and 25 mg/kg) significantly increased in vitro colony formation by cells of the granulocyte-macrophage lineage in the spleen and bone marrow. Splenic hypercellularity, splenomegaly and elevated levels of blood leukocytes were observed in these mice 7 days following Photofrin injection. Evidence that Photofrin influenced the lymphohematopoietic compartment was suggested by a significant increase in blood lymphocytes and a population of spleen cells identified by a monoclonal antibody (LR-1) reactive with mouse splenic B lymphocytes. Proliferative responses of spleen cells from Photofrin-treated mice to sub-optimal concentrations of Con A were greater than that observed for controls. However, spleen cell responses to LPS were unaltered by Photofrin administration. In contrast, BPD (10 mg/kg) did not alter any of the immunohematopoietic parameters studied. When Photofrin was administered to mice treated with the myeloablative agent 5-FU there was a significant acceleration in the recovery of total blood leukocyte and spleen cell numbers, relative to the controls. These studies demonstrate that, in addition to its previously documented activities as a photosensitizer, Photofrin can exert stimulatory effects upon murine hematopoiesis.

Mechanism of action of hydroxychloroquine as an antirheumatic drug

The antimalarial agents chloroquine and hydroxychloroquine have been used widely for the treatment of rheumatoid arthritis and systemic lupus erythematosus. These compounds lead to improvement of clinical and laboratory parameters, but their slow onset of action distinguishes them from glucocorticoids and nonsteroidal antiinflammatory agents. Chloroquine and hydroxychloroquine increase pH within intracellular vacuoles and alter processes such as protein degradation by acidic hydrolases in the lysosome, assembly of macromolecules in the endosomes, and posttranslation modification of proteins in the Golgi apparatus. It is proposed that the antirheumatic properties of these compounds results from their interference with "antigen processing" in macrophages and other antigen-presenting cells. Acidic cytoplasmic compartments are required for the antigenic protein to be digested and for the peptides to assemble with the alpha and beta chains of MHC class II proteins. As a result, antimalarials diminish the formation of peptide-MHC protein complexes required to stimulate CD4+ T cells and result in down-regulation of the immune response against autoantigenic peptides. Because this mechanism differs from other antirheumatic drugs, antimalarials are well suited to complement these other compounds in combination drug therapy.

Dynamic modulation of the cell surface expression of the granulocyte-macrophage colony-stimulating factor receptor

The GM-CSF receptor (GM-CSFR) is composed of alpha and beta subunits. Surface expression of the alpha chain alone leads to low affinity GM-CSF binding and of both subunits to high affinity binding; the beta chain is required for transducing a proliferative signal. Studies of GM-CSFR expression have concentrated largely on static events occurring under conditions of binding equilibrium. We have examined the dynamic regulation of high and low affinity GM-CSFR expression in neutrophils (1100 +/- 200 R/cell, KD 50 +/- 15 pM) and a GM-CSF dependent human leukaemic cell line, TF-1 (2000 +/- 450 R/cell KD 15 +/- 5 pM) and 8600 +/- 1150 R/cell KD 1.8 +/- 0.3 nM). The addition of GM-CSF to TF-1 cells (350 pM, 4 h at 37 degrees C) caused a reduction in subsequent binding of 125I-GM-CSF at low ligand concentration (100 pM) (following a low pH wash to remove surface bound ligand) to 16 +/- 4% and a reduction in binding at high ligand concentration (2 nM 125I-GM-CSF) to 36 +/- 9% of control. Scatchard analysis showed complete down-regulation of high affinity GM-CSFR and a significant reduction in low affinity GM-CSFR. In neutrophils, concentration-response curves of ligand induced receptor down-regulation at 37 degrees C showed that observed down-modulation was more than 10-fold greater than predicted by static equilibrium binding data and correlated closely with GM-CSF priming of the neutrophil respiratory burst. The addition of IL-3 to TF-1 cells at 37 degrees C reduced 100 pM 125I-GM-CSF binding to 18 +/- 4% and 2 nM 125I-GM-CSF binding to 46 +/- 5% of control. TF-1 cells, but not neutrophils, were able to re-express GM-CSFR following removal of GM-CSF from medium. TF-1 proliferation assays showed that pulsed GM-CSF (0.35-3.5 nM) for up to 4 h did not cause a significant increase in 3H-thymidine incorporation which required the continued presence of GM-CSF (control 2875 +/- 208 cpm, pulsed GM-CSF 5 ng/ml 4972 +/- 1344, continuous GM-CSF 5 ng/ml 17249 +/- 2982). Therefore, proliferation of TF-1 cells required the continued presence of GM-CSF at a time when there was no detectable surface high affinity GM-CSFR.(ABSTRACT TRUNCATED AT 400 WORDS)

Stem cell renewal and determination during clonal expansion in normal and leukaemic haemopoiesis

Normal haemopoiesis is a cellular hierarchy headed by pluripotent stem cells capable of both self renewal and, after determination, the generation of differentiating lineages that end in terminal functional cells. The role of stem cells is crucial because only these have the capacity to generate clonal populations during development or after injury. During clonal expansion the cells are affected by many sets of receptors and ligands. These belong to at least two classes: one consists of growth factors that bind cell surface receptors and initiate signalling events; the other class contains receptors which act as ligand-dependent transcription factors such as the intracellular steroid superfamily. In spite of this elaborate regulatory apparatus, control during clonal expansion is lax, perhaps stochastic, as evident from the great heterogeneity disclosed by examining the cellular compositions of haemopoietic clones. It may be that the large number of signals impinging on binary possible outcomes (for example self-renewal or determination) serve to set probabilities rather than to determine outcomes. In leukaemia, many of the features of normal haemopoiesis are retained. The disease begins as transformations in normal stem cells; after additional leukaemogenic events clonal expansion yields malignant populations which are clonal in each affected individual. These dominant clonal populations retain the hierarchical organization found in the normal, the major difference is that post-deterministic divisions in leukaemia yield descendants that retain primitive (blast) morphology although proliferative capacity is lost. In acute myeloblastic leukaemia (AML) cell culture methods are available that permit the measurement of clonogenic blast stem cells. These methods have shown that regulatory mechanisms active in normal haemopoiesis are retained in AML, including lax regulation during clonal expansion. The biological features of blast stems cells displayed by the culture technique reflect in part, events in vivo, as associations have been found between results in cell culture and clinical outcome. Thus, study of leukaemic populations provides a challenge for basic science and an opportunity for successful application in control of disease.

Human recombinant GM-CSF selectively primes receptor mediated respiratory burst of neutrophils in vitro

The influence of human recombinant granulocyte-macrophage colony-stimulating factor (rH GM-CSF) on respiratory burst response of isolated human neutrophils was examined. Preincubation of cells with rH GM-CSF significantly increased the respiratory burst in response to formyl-methionyl-leucyl-phenylalanine (FMLP), measured by luminol-dependent chemiluminescence (CL) assay. This priming effect of rH GM-CSF was independent of extracellular Ca2+ and Mg2+. On the other hand, the pretreatment of cells with rH GM-CSF could not enhance the neutrophil CL responses to unopsonized, serum complement-opsonized or immunoglobulin G (IgG)-opsonized zymosan particles. rH GM-CSF directly induced a weak CL signal in neutrophils. This signal, however, was abolished when extracellular Ca2+ and Mg2+ were removed. Exposure to rH GM-CSF caused a divalent cation-dependent up-regulation of complement receptors (CR1 and CR3) on neutrophil cell surface, while the expression of IgG Fc-receptors (FcRII and FcRIII) was not markedly changed by rH GM-CSF. The results indicate that rH GM-CSF primes FMLP-induced CL but not zymosan particle-induced respiratory burst in human neutrophils. It is hypothesized that the reason for the different sensitivity of FMLP-receptors and receptors to zymosan particles to rH GM-CSF priming may lie in differences in the signal-transduction pathways of these receptor types.

Induction of macrophagic and granulocytic differentiation of murine bone marrow progenitor cells by 1,25-dihydroxyvitamin D3

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) was recently shown to promote maturation of 5-fluorouracil (5FU)-treated bone marrow cells by up-regulating macrophage-colony stimulating factor (M-CSF) receptors in the presence of interleukin 1 alpha (IL-1 alpha). In order to reveal how 1,25(OH)2D3 interacts with colony-stimulating factors and regulates the differentiation of bone marrow progenitor cell populations, in the present study, natural bone marrow cells were isolated from untreated mice and used in alpha-minimum essential medium supplemented with 20% heat-inactivated horse serum without added appropriate cytokines. Under the conditions, cells spontaneously differentiated gradually with days of culture, as assessed by expression of macrophage differentiation antigens such as Mac-1 (CD11b) and F4/80. Both M-CSF and granulocyte macrophage-colony stimulating factor (GM-CSF) induced only Mac-1 antigen expression. Simultaneous treatment with M-CSF and 1,25(OH)2D3 enhanced the M-CSF's effect on expression of both antigens, although 1,25(OH)2D3 per se has no effect on the expression for up to 11 days. In addition, successive treatment with 1,25(OH)2D3 and M-CSF or GM-CSF dramatically enhanced expression of both antigens or Mac-1 antigen, respectively. Similarly, both simultaneous and successive treatment with 1,25(OH)2D3 and M-CSF significantly enhanced phagocytic activity and H2O2 production, whereas successive treatment with 1,25(OH)2D3 and GM-CSF significantly enhanced only phagocytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of macrophage colony stimulating factor and granulocyte-macrophage colony stimulating factor on osteoclastic differentiation of hematopoietic progenitor cells

Although the hematopoietic origin of the osteoclast is generally accepted, the precise phenotype of the progenitor and the regulation of its differentiation are unclear. This study compares proliferation and differentiation of progenitors in response to macrophage colony stimulating factor (M-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF). Nonadherent progenitor cells from murine long-term bone marrow cultures (LTBMC) (as a source of osteoclast progenitors) demonstrated a significant proliferative response to M-CSF. In addition, M-CSF increased the number of multinucleated cells, only a small percent of which (14-16%) were tartrate-resistant, acid phosphatase (TRAP)-positive. In contrast, cells cultured with GM-CSF generated more TRAP-positive multinucleated cells even at concentrations less stimulatory of proliferation than M-CSF. The osteoclast phenotype of these multinucleated cells was also assessed by ultrastructural characterization of ruffled borders in association with bone fragments. The bone-active hormone 1,25-dihydroxyvitamin D3 inhibited the proliferation of this subset of progenitor cells in the presence of M-CSF or GM-CSF. All of these results show effects on progenitors in the absence of the stromal cell microenvironment in this system. These results provide evidence for a divergence in the biological responsiveness of osteoclast progenitor cells to M-CSF compared with GM-CSF; they support the notion that M-CSF has a "priming" effect on osteoclast progenitors whose subsequent differentiation to osteoclastic multinucleated cells is promoted by GM-CSF.

Cytotoxic lymphocyte maturation factor (interleukin 12) is a synergistic growth factor for hematopoietic stem cells

The recently cloned cytotoxic lymphocyte maturation factor (interleukin 12 [IL-12]) has been described as a growth factor for mature lymphocytes. The present study investigated whether purified recombinant murine IL-12 (rMuIL-12) also could affect the proliferation of primitive bone marrow progenitor cells. Using a population of Lin-Sca-1+ murine bone marrow stem cells, we now demonstrate that IL-12 is a potent synergistic factor for primitive hematopoietic stem cells. The synergy of IL-12 was observed in single-cell cloning assays, demonstrating that its effects are directly mediated. Specifically, IL-12 enhanced stem cell factor-induced myelopoiesis of Lin-Sca-1+ cells sevenfold, and synergized with colony-stimulating factors (CSFs) to induce proliferation of Lin-Sca-1+ stem cells. IL-12 increased the number of responding progenitor cells as well as the size of the colonies formed. IL-12 also increased colony formation of high proliferative potential colony-forming cells with multiple CSF combinations. The effects of IL-12 were concentration dependent with a 50% effective dose of 2-20 and 20-200 ng/ml, resulting in maximum stimulation. Furthermore, a neutralizing anti-IL-12 antibody blocked the synergistic effects of rMuIL-12. In addition, IL-12 was found to have synergistic effects on more committed bone marrow progenitors as well. Our results therefore suggest that in addition to being a potent lymphopoietic stimulator, IL-12 is a regulator of the growth of hematopoietic stem cells and their myeloid progeny.

Tumor necrosis factor alpha cooperates with interleukin 3 in the recruitment of a primitive subset of human CD34+ progenitors

We have recently demonstrated that tumor necrosis factor alpha (TNF-alpha) potentiates interleukin 3 (IL-3) and granulocyte/macrophage colony-stimulating factor-induced growth of CD34+ hematopoietic progenitor cells (HPC), and favors the generation of dendritic/Langerhans cells. The stimulatory effect of TNF-alpha was detailed in the present study. Thus, CD34+ HPC entering in cycle (S/G2M) after a 48-h pulse with IL-3 expressed the transferrin receptor (TfR), and fluorescence-activated cell sorter-separated TfR+ HPC, but not TfR-HPC, showed a high proliferative response to IL-3. In contrast, TfR-HPC were found to undergo strong proliferation in response to IL-3 + TNF-alpha. Limiting dilution experiments indicated that TNF-alpha increased both the frequency and the average size of clones generated from TfR-HPC as a result of the development of a higher number of large clones. In contrast, TNF-alpha did not enhance the IL-3-dependent proliferation of TfR+ HPC. Preculturing CD34+ HPC for 48 h with TNF-alpha enhanced the subsequent generation of IL-3-dependent colony-forming units. Precultures with TNF-alpha or cultures with suboptimal doses of TNF-alpha allowed the recruitment of cells with both granulocytic and monocytic differentiation potential. Taken together, our results indicate that TNF-alpha recruits a subpopulation of CD34+ HPC hyposensitive to IL-3, with high proliferative capacity and some features of multipotential progenitors, that are likely to be more primitive than those responding to IL-3 alone.

Proliferation patterns in acute myeloid leukemia: leukemic clonogenic growth and in vivo cell cycle kinetics

In a prospective study of 33 newly diagnosed patients with acute myeloid leukemia (AML), we analyzed the relationship of proliferation parameters with clinical parameters, response to induction therapy, and survival. The median follow-up was 26 months. The proliferative capacity of the leukemic progenitor cells was studied using colony-forming assays (number of colony-forming units, growth pattern, and spontaneous clonogenic growth capacity). The cell kinetic parameters of the bone marrow blasts were determined by in vivo labeling with iododeoxyuridine and subsequent flow cytometry: labeling index (LI), DNA synthesis time (Ts), potential doubling time. No or only weak relationships were observed between the experimental and clinical parameters such as age, sex, % blasts, white blood cell count, FAB subtype, cytogenetics, and % CD 34+ cells. This suggests that clonogenic growth and cell cycle kinetics of bone marrow blasts are independent cell biologic properties of AML. No association between the proliferation parameters and induction response rate was noticed. Analysis of the overall survival and event-free survival revealed trends to longer survival rates in patients with a below-median LI (< or = 7.6%) and below-median Ts value (< or = 14.3 h). These trends were more pronounced in the group of de novo AML (n = 23), where the prolonged event-free survival in patients with below-median Ts reached statistical significance (p = 0.02). None of the other parameters appeared significantly correlated with survival, although there was a trend to longer survival rates in patients who had no spontaneous clonogenic growth capacity (p = 0.13). In conclusion, proliferation parameters in leukemic cells provide additional information on the cell biologic characteristics of AML, and these parameters may have prognostic value for response and duration of survival in AML.

v-myb blocks granulocyte colony-stimulating factor-induced myeloid cell differentiation but not proliferation

To understand the effects of v-myb expression on mammalian hematopoietic cell differentiation, we have constructed a retroviral vector which can efficiently express v-myb gene product in mammalian cells. Infection of interleukin-3-dependent murine progenitor cell line 32D Cl3, which undergoes terminal differentiation to mature granulocytes in the presence of granulocyte colony-stimulating factor (GCSF), with this recombinant retrovirus does not abrogate its requirement of interleukin-3 for growth. However, expression of v-myb in these cells blocks their ability to differentiate in response to GCSF. Instead, the v-myb-infected cells proliferate indefinitely in the presence of GCSF. 32D Cl3 cells infected with empty vector carrying only the neomycin resistance gene responded to the addition of GCSF in a manner identical to that of the uninfected cells and underwent terminal differentiation into granulocytes. These results suggest that oncogenic forms of myb gene bring about transformation by blocking the differentiation signal derived by cytokines while promoting the proliferative signal transduction pathways.

Modulation of transferrin receptor expression by insulin and granulocyte-macrophage colony stimulating factor in AML-193 leukemic cells

The effects of insulin and granulocyte-macrophage colony stimulating factor (GM-CSF) on the expression of transferrin receptors in AML-193 myeloid leukemia cell line were investigated. Insulin, alone or in combination with GM-CSF, caused an increase in surface transferrin receptors within 5 min. This increase was inhibited by hyperosmolarity but not by cycloheximide suggesting the involvement of receptor recycling from internal pools. In contrast, receptor increase after 18 h of incubation with insulin and GM-CSF was sensitive to cycloheximide indicating that long term effects of these growth factors are mediated through protein synthesis. These results may have implications on combined GM-CSF + antitransferrin receptor antibody therapy of leukemias.

Granulocyte-macrophage colony-stimulating factor induces human melanoma-cell migration

Tumor metastasis is the primary cause of death for cancer patients. The metastatic cascade requires successful tumor cell invasion into and through vascular and parenchymal barriers. We have shown that autocrine motility factor (AMF, autotaxin) and the insulin-like growth factors (IGFs) induce tumor-cell migration. Since granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to prime neutrophils for chemotaxis, we have therefore studied the influence of GM-CSF upon tumor cells and report that GM-CSF stimulates migration of these cells in a dose-dependent fashion. The ED50 for A2058 human melanoma cell line chemotaxis to GM-CSF is approx. 60 pM. The motile response to GM-CSF was additive to that of IGF-I and AMF, both of which are potent attractants for tumor cells. Pre-treatment of cells for 2 hr with non-toxic concentrations of pertussis toxin (PT) or amiloride resulted in a 50% inhibition of chemotaxis to GM-CSF. Therefore, GM-CSF, through PT- and amiloride-sensitive signal pathways, is a potent attractant for melanoma cells, the response to which is additive to that of other attractants. The presence of the GM-CSF receptor in A2058 melanoma cells was indicated by Northern-blot analysis which identified message transcripts of 2.1 and 3.0 kb. These data emphasize the versatility of the melanoma cell migration response to an array of cytokines, including GM-CSF.

v-myb blocks granulocyte colony-stimulating factor-induced myeloid cell differentiation but not proliferation

To understand the effects of v-myb expression on mammalian hematopoietic cell differentiation, we have constructed a retroviral vector which can efficiently express v-myb gene product in mammalian cells. Infection of interleukin-3-dependent murine progenitor cell line 32D Cl3, which undergoes terminal differentiation to mature granulocytes in the presence of granulocyte colony-stimulating factor (GCSF), with this recombinant retrovirus does not abrogate its requirement of interleukin-3 for growth. However, expression of v-myb in these cells blocks their ability to differentiate in response to GCSF. Instead, the v-myb-infected cells proliferate indefinitely in the presence of GCSF. 32D Cl3 cells infected with empty vector carrying only the neomycin resistance gene responded to the addition of GCSF in a manner identical to that of the uninfected cells and underwent terminal differentiation into granulocytes. These results suggest that oncogenic forms of myb gene bring about transformation by blocking the differentiation signal derived by cytokines while promoting the proliferative signal transduction pathways.

CSF-1 expression is upregulated in astrocyte cultures by IL-1 and TNF and affects microglial proliferation and morphology in organotypic cultures

Astrocytes produce factors that control the growth and differentiation of many cell types within the CNS as well as play a role in the generation of the immune response. The extent to which these two functions interact has received less attention. We now report that astrocyte cultures established from rat brain endogenously express mRNA and low levels of secreted biologically active protein for the monocyte growth and differentiation factor colony stimulating factor-1 (CSF-1). Exposure of astrocytes to interleukin-1 (IL-1) and/or tumor necrosis factor (TNF) upregulated the expression of CSF-1 mRNA and protein. Following treatment with 100 U/ml of TNF, IL-1, or TNF+IL-1, maximum CSF-1 mRNA expression was observed at 3 hr. In the presence of IL-1 an increase in biologically active CSF-1 was detected in the astrocyte conditioned medium at 6 hr. These data indicate that the expression of CSF-1 by astrocytes can be modulated by exposure to the cytokines IL-1 and TNF. To determine whether CSF-1 provides a mitogenic signal for microglia during development, mouse spinal cord organotypic cultures were exposed to recombinant mouse CSF-1 (rmCSF-1), resulting in proliferation of microglia by 7 days and an increase in the number of ramified microglia over ameboid microglia by 14 days.

Cytokine regulation of neuronal differentiation of hippocampal progenitor cells

The signalling mechanisms governing haematolymphopoiesis and those regulating neural development may be closely related, as indicated by similarities of higher-order structure and function of the cytokines involved, of the regional and temporal regulation of their transcription and translation, and of their bioactivity. Here we investigate this possible evolutionary connection using retroviral transduction of a temperature-sensitive mutant form of the SV40 large T antigen to develop conditionally immortalized murine embryonic hippocampal progenitor cell lines. Treatment of these cells with cytokines that are thought to participate in progressive lymphoid maturation, immunoglobulin synthesis and erythropoiesis causes progressive neuronal differentiation, as defined by morphological criteria, successive expression of increasingly mature neurofilament protein, and the generation of inward currents and action potentials. The cytokine interleukin(IL)-11 induces expression of action potentials that are insensitive to tetrodotoxin, which is indicative of developmentally immature sodium channels. By contrast, for expression of more mature action potentials (tetrodotoxin-sensitive) one of the interleukins IL-5, IL-7 or IL-9 must be applied in association with transforming growth factor-alpha after pretreatment with basic fibroblast growth factor. Our results suggest that the mechanisms regulating lineage commitment and cellular differentiation in the neural and haematopoietic systems are similar. Further, they define an in vitro model system that may facilitate molecular analysis of graded stages of mammalian neuronal differentiation.

Deregulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor in murine macrophage cell line J774A.1

J774A.1 immortalized macrophage tumor cells display several phenotypes and functional capacities similar to that of murine peritoneal exudate macrophages (PEM). Both populations display comparable number of M-CSF receptors. Yet the number of GM-CSF receptors on J774A.1 cells is only one-fourth that of PEM (1,500 vs. 6,000 per cell). Unlike J774A.1 cells, which constitutively express c-myc transcripts, normal PEM required rMuGM-CSF for the induction of c-myc expression. Nevertheless, the growth of J774A.1 cells can be further enhanced in the presence of exogenous rMuGM-CSF, rHuM-CSF, and rMuIL-3. Treatment with either rMuIL-3 (20 ng/ml) and rHuTGF-beta 1 (1.0 ng/ml) for 24 hr at 37 degrees C, markedly enhanced the expression of GM-CSF receptors on normal PEM but not leukemic J774A.1 cells. J774A.1 cells also did not respond by autologous upregulation of GM-CSF receptors as seen in PEM following treatment with rMuGM-CSF. Treatment with either pertussis toxin (20-100 ng/ml) or H-8 (50 microM) for 24 hr led to an enhanced expression of GM-CSF receptors on J774A.1 cells in a time- and dose-dependent manner but did not result in enhanced receptor expression on normal PEM. These findings suggest that the expression of GM-CSF receptors may be regulated by mechanisms involving Gi-proteins and their downstream elements, which in turn are linked to regulatory pathways of other cytokine receptors. In J774A.1 cells, such regulatory interaction may not exist.

Expansion of human bone marrow progenitor cells in a high cell density continuous perfusion system

We describe here a continuous perfusion bioreactor system that enables a population of unselected human mononuclear bone marrow cells obtained from adult donors to expand up to 20 to 25-fold over a two-week period. Colony-forming units of granulocyte-macrophage (CFU-GM) progenitor cells expand 10 to 30-fold. These expansions depend on the gas phase oxygen concentration, the seeding density and time of cell harvest. Under operating conditions that allow for good cell proliferation, 3 to 4 million mononuclear cells can be obtained per square centimeter, with 0.5 to 0.8% being progenitor cells. Autologous human sera supported cell expansion as efficiently as animal sera. Increasing the size of the perfusion system to produce a clinically meaningful number of CFU-GMs could have important applications in bone marrow transplantation therapies.

Relationship between c-Kit expression and proliferation in acute myeloblastic leukemia cell lines

We have proposed that the transmembrane receptor encoded by the c-Kit protooncogene and its ligand play an important role in regulating the proliferation of blasts cells in acute myeloblastic leukemia (AML). To test this hypothesis, immunobeads were used to separate blasts from three Kit-expression positive cell lines into strongly Kit-protein positive and weakly Kit-protein positive fractions. The strongly positive fraction had greater proliferative potential than the weakly positive fraction as assessed both by colony-formation in methylcellulose and growth of clonogenic cells in suspension. The reproducibility of the percentage of each blast population found in the strongly and weakly positive fractions provided evidence that Kit-protein expression is regulated. Kinetic experiments provided evidence for reversible transitions between strong and weak Kit protein expression. Thus regulated expression of the Kit receptor may be a mechanism for controlling blast cell growth in culture.

Effect of hemopoietic growth factors G-CSF and pIXY 321 on the activity of high dose Ara-C in human myeloid leukemia cells

Recently, high dose Ara-C (HIDAC) has been shown to induce leukemic cell death in vitro by the alternative process of programmed cell death (PCD) or apoptosis which correlates with the inhibition of their clonogenic survival. Since co-treatment with hemopoietic growth facts (HGFs) GM-CSF and IL-3 have been demonstrated to enhance the metabolism and cytotoxic effects of HIDAC against leukemic progenitor cells, we examined the effect of HGFs pIXY 321 (a GM-CSF/IL3 fusion protein) and G-CSF on HIDAC induced PCD and related gene expressions as well as HIDAC mediated colony growth inhibition of human myeloid leukemia cells. Treatment with G-CSF or pIXY 321 alone for up to 24 hours neither suppressed nor induced PCD in HL-60 or KG-1 cells. However, exposure to either of the HGFs for 20 hours followed by a combined treatment for 4 hours with HIDAC plus either of the HGFs versus HIDAC alone significantly enhanced the intracellular Ara-CTP accumulation and the oligonucleosomal DNA fragmentation characteristic of PCD. This was temporally associated with a marked induction of C-jun expression but a significant repression in BCL-2 and c-myc expressions. In addition, the treatment with either of the HGFs plus HIDAC versus HIDAC alone produced a significantly greater inhibition of the clonogenic survival of the myeloid leukemia cells. These findings underscore an additional mechanism of leukemic cell death induced by HIDAC which can be modulated by the HGFs to improve the antileukemic activity of HIDAC.

Haemopoietic stem cell development to neutrophils is associated with subcellular redistribution and differential expression of protein kinase C subspecies

Multipotential FDCP-Mix A4 (A4) cells can be induced either to self-renew or to differentiate and develop into mature neutrophils in liquid culture, depending on the haemopoietic growth factors with which they are cultured. When cultured in low concentrations of interleukin 3 (IL-3, 1 unit/ml)) plus Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) and Granulocyte-CSF (G-CSF), A4 cells proliferate with accompanying development to form cells which resemble mature, postmitotic neutrophils. The presence of high concentrations of IL-3 (100 units/ml) blocks the development of A4 cells even in the presence of GM-CSF plus G-CSF. A4 cell development to neutrophils is accompanied by major changes in the expression of protein kinase C (PKC) subspecies in these cells. The predominant subspecies present in multipotent A4 cells, as judged by direct chromatographic analysis, was the type III enzyme (alpha) subspecies, whereas in mature A4 cell neutrophils, the type II (beta I + beta II) enzymes were predominant. Phorbol esters added to immature A4 cells resulted in a proliferative response, but when added to postmitotic A4 cells resembling neutrophils they elicited a large increase in reactive oxygen intermediate production. This suggests that the type III (alpha) subspecies may mediate proliferative responses in stem cells, whilst the type II (beta I + beta II) enzymes are more important for the mature cell functions of postmitotic neutrophils. In cultures containing IL-3 (100 units/ml) both the type III, and also the type II subspecies were predominantly membrane-associated for prolonged periods (&gt; 24 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

GM-CSF and TNF-alpha cooperate in the generation of dendritic Langerhans cells

Dendritic cells comprise a system of highly efficient antigen-presenting cells which initiate immune responses such as the sensitization of T cells restricted by major histocompatibility complex molecules, the rejection of organ transplants and the formation of T-cell-dependent antibodies. Dendritic cells are found in many non-lymphoid tissues, such as skin (Langerhans cells) and mucosa, and they migrate after antigen capture through the afferent lymph or the bloodstream to lymphoid organs, where they efficiently present antigen to T cells. Dendritic cells are difficult to isolate and, although they originate from bone marrow their site of maturation and the conditions that direct their growth and differentiation are still poorly characterized. Granulocyte macrophage-colony stimulating factor (GM-CSF) favours the outgrowth of dendritic cells from mouse peripheral blood. Here we extend this finding to man and demonstrate that cooperation between GM-CSF and tumour necrosis factor-alpha (TNF-alpha) is crucial for the generation of human dendritic/Langerhans cells from CD34+ haematopoietic progenitors. The availability of large numbers of these cells should now facilitate the understanding of their role in immunological regulation and disorder.

Myxoma virus M11L ORF encodes a protein for which cell surface localization is critical in manifestation of viral virulence

Myxoma virus (MYX) induces extensive immunosuppression in infected rabbits and is associated with high levels of mortality. The virus encodes multiple gene products designed to circumvent the cellular immune response to the viral infection. Deletion analysis has shown that the M11L open reading frame (ORF) is an important virulence factor which downregulates leukocyte infiltration of MYX-induced tumors. To investigate the role of the M11L protein in viral pathogenesis, we sequenced the MYX M11L ORF and showed that the sequence has motifs consistent with a 166-aa class III membrane-spanning molecule possessing a single transmembrane helix near the C-terminus and a 142-aa N-terminal extracellular domain that has six cysteine residues plus two consensus N-glycosylation sites. Transcription analysis indicates that M11L is expressed as an early gene, and surface immunofluorescence studies with anti-M11L antibodies reveal that M11L protein is transported to the infected cell surface. Immunoprecipitation analysis of an attenuated viral recombinant, vMYX-GF-delta M11L, indicates that an M11L variant protein with an altered C-terminus is synthesized at about 45% of wild type levels; however, it is not detectable on the cell surface, suggesting that proper M11L function requires localization at the infected cell membrane. We propose that M11L is a virulence factor whose function is to recognize an extracellular ligand essential for the cellular inflammatory response.

Interleukin-6 and its receptor: a paradigm for cytokines

Many cytokines and cytokine receptors involved in the regulation of hematopoiesis, immune responses, and inflammation have been identified and characterized at the molecular level. Several characteristic features of cytokines, such as pleiotropy and redundancy, are now more clearly understood on the basis of their molecular structures. Accumulating evidence has demonstrated an intimate link between cytokines and various diseases such as allergy, autoimmune diseases, and cancer. The pathogenesis of these diseases and therapies to treat them will be discussed based on insights derived from cytokine research.

Recombinant interleukin-6 protects mice against experimental bacterial infection

Because of reports of high levels of interleukin-6 (IL-6) in patients during infection, we studied the role of IL-6 in experimental infection. Mice infected with the facultative intracellular pathogen Listeria monocytogenes displayed high levels of IL-6 in their sera and tissues, particularly the spleen, 1 to 3 days after infection. At this time, the IL-6 titers correlated with bacterial numbers in individual mice and in groups of mice given graded doses of Listeria organisms. However, the presence of IL-6 in serum declined after 4 days, even when a large initial dose of bacteria meant that bacterial numbers were still increasing at this time. Recombinant mouse IL-6 injected intraperitoneally before infection protected mice in a dose-dependent manner. It was effective when given 4 h before infection but not when administration was delayed for 24 h postinfection. It is therefore believed that IL-6 plays a role in early priming of the immune response to infection. Its exact function in this model is being investigated.

Transplantable myeloproliferative disease induced in mice by an interleukin 6 retrovirus

Lethally irradiated mice transplanted with bone marrow cells infected with a novel recombinant retrovirus (murine stem cell virus-interleukin 6 [MSCV-IL-6]) bearing a mouse IL-6 gene developed a fatal myeloproliferative disease within 4 wk of engraftment. The hematologic manifestations of the syndrome included elevated peripheral leukocyte counts (up to 430 x 10(3) cells/mm3) with a predominance of neutrophilic granulocytes, microcytic anemia, and thrombocytosis or thrombocytopenia. The mice showed extensive neutrophil infiltration of the lungs, liver, and occasionally lymph nodes, plus splenomegaly resulting from enhanced splenic myelopoiesis (30-60-fold increase in progenitor numbers). Despite the chronic stimulation of neutrophil excess by IL-6, bone marrow from affected mice was capable of repopulating the hematopoietic tissues (bone marrow and spleen) of lethally irradiated hosts during repeated serial transplantation. In the longest documented case, the progeny of a single MSCV-IL-6-marked cell transferred the myeloproliferative disease to two secondary, four tertiary, and two quaternary recipients (the clone endured for a total of 72 wk). These results, demonstrating considerable proliferative longevity of the IL-6-producing cells, support an in vivo role of IL-6 in the maintenance of hematopoietic precursors. Dysregulated IL-6 production also had significant systemic effects. The mice displayed increased mesangial cell proliferation in the kidney, frequent liver abnormalities, and marked alterations in plasma protein levels. Unlike previous studies where constitutive expression of exogenous IL-6 genes resulted in lymphoproliferative disorders characterized by massive plasmacytosis, minimal plasma cell expansion occurred in the MSCV-IL-6 mice during the observation period. Potential explanations for the differences in disease phenotypes observed in the present and previous studies are different cell types expressing the exogenous IL-6 genes, higher sustained circulating levels of IL-6 achieved using the MSCV-IL-6 retroviral delivery system, and/or the premature death (3-15 wk after transplantation) of the MSCV-IL-6 mice before the onset of plasmacytosis. This animal model should prove useful for further investigation of the function of IL-6 in normal and abnormal hematopoiesis and in inflammatory responses.

The immune system in health and disease

For an immune response against an eliciting antigen, innate and adaptive immune mechanisms interact to provide a specific and appropriate response characterized by self-non-self discrimination and memory. This non-random process involves antigen presentation followed by T cell recognition and activation with the elaboration of T cell-derived lymphokines. The nature and amount of lymphokine production from antigen-activated T cells then determines the predominant immune response (e.g. cytotoxicity versus antibody). Exogenous regulatory factors, including steroid hormones, prostaglandins, and cytokines, modulate immune responsiveness. How these regulatory factors influence the immune response during specific host-parasite interactions determines the predominant immune response to specific antigen. As the regulation of the immune response is unravelled, new and powerful immunomodulatory therapies will be developed and utilized to improve the immune response and host survival.

The impact of surgery on the multidisciplinary treatment of bronchogenic small cell carcinoma (updated review including ongoing studies)

Recent results of studies on patients with SCLC treated by surgery with curative intent followed by adjuvant chemotherapy demonstrate a definite progress in comparison to non-surgical-treatment programs for patients with comparable stage of disease. Of 186 randomized patients enrolled for the multicenter cooperative ISC-Study I and II, 76 patients with stage pT1-3N0M0 received surgery for cure followed by chemotherapy and selective radiotherapy to the brain. The projected 4 year crude survival rate by September 1991 was 57%. In 27 of 43 patients with stage pT1-3N2M0, the tumors were completely resected, resulting in a 4 year survival rate of 32%. The survival curve for both groups of patients shows a sharp bent at 27 months postoperatively, whereafter the survival curves take a plateau-like course. These promising results were confirmed by several other groups. They are in favour of initial surgery for resectable tumors, followed by postoperative chemotherapy, while patients on preoperative chemotherapy followed by adjuvant surgery showed less favourable results.

IL-3 and GM-CSF induce the expression of the inositol trisphosphate receptor in K562 myeloblast cells

When treated with IL-3 plus GM-CSF, K562 myeloblast cells acquired the ability to mobilize nonmitochondrial stores of intracellular Ca2+ in response to added Ins (1, 4, 5) P3. Untreated K562 cells are capable of sequestering intracellular Ca2+ but released none of this Ca2+ in response to Ins (1, 4, 5) P3. Untreated K562 cells were shown to have no detectable specific [3H] Ins (1, 4, 5) P3 binding sites and no InsP3 receptor mRNA as assayed by Northern blot and PCR. However, following IL-3 and GM-CSF treatment, both a single class of low nM KD Ins (1, 4, 5) P3 binding site and a 10 kb InsP3 receptor mRNA were detectable. The results suggest that IL-3 and GM-CSF regulate the expression of the Ins (1, 4, 5) P3 receptor gene.

Enhancement of cell production in long-term bone marrow culture

In an effort to increase the long-term production of hematopoietic cells in vitro, Origen hybridoma cloning factor (HCF) was added at the initiation of Dexter type cultures, in which whole bone marrow (BM) was seeded into tissue culture flasks and formed an adherent stromal layer that supported the proliferation and differentiation of primitive cells. After about six weeks, all the cultures were fully established, and continuous production of nonadherent cells was maintained for at least 27 weeks. In the groups with 20% HCF, there was a significant (three- to fourfold) increase in the steady-state cell production of 106 +/- 17 x 10(4) cells/ml compared to 26 +/- 10 x 10(4) in controls. In some cases the ability of HCF to increase productivity was limited by the nutrients and metabolic products in the culture medium. Cell number varied inversely with glucose and pH. HCF increased the concentration and absolute number of myeloid progenitors (granulocyte-macrophage colony forming units and spleen colony forming units) in the nonadherent layer and shifted the differentiation of granulocyte-macrophage colony forming units toward the production of cells of the monocyte/macrophage lineage. Spleen colonies produced from 10(5) cells from cultures with HCF were more numerous (8 +/- 2 versus 4 +/- 2) and larger than those from control cultures (2.6 versus 0.2 mg/colony), but they contained the usual cell lineages (erythrocytic, granulocytic and megakaryocytic).

Epidermolysis bullosa acquisita induced by GM-CSF: a role for eosinophils in treatment-related toxicity

A patient treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) developed eosinophilia and epidermolysis bullosa acquisita. The bullae were subepidermal, and filled with an inflammatory infiltrate composed predominantly of eosinophils. Immunofluorescence studies disclosed linear deposition of IgG, IgA and C3 at the basement membrane zone and immunoelectron microscopy demonstrated antibody deposition in the lamina densa and sublamina densa region; however, the patient's serum did not contain circulating antibody to basement membrane zone antigens. Staining with monoclonal antibodies revealed dense deposits of both eosinophil peroxidase and eosinophil major basic protein at the dermal-epidermal junction. The eosinophilia and skin lesions resolved upon discontinuation of GM-CSF. This case provides evidence for two hypotheses: (1) GM-CSF induced proliferation and activation of eosinophils may contribute to some of the toxicities of GM-CSF treatment, and (2) activated granulocytes, including eosinophils, may mediate blister formation in epidermolysis bullosa acquisita.

Novel factors from stromal cells: bone marrow and thymus microenvironments

The microenvironments contained within mammalian bone marrow and thymus play major roles in the life-long process of myeloid and lymphoid cell development and renewal. The cells that give architecture to these microenvironments are collectively referred to as stromal cells, and these cells grow as adherent cell types in cell culture. Stromal cells are predominantly a mixture of fibroblasts, cells of macrophage/dendritic lineages, epithelial and endothelial cells. There are at least three mechanisms that govern the interaction of stromal cells with hematopoietic and lymphoid cells: soluble factors, or cytokines, membrane-anchored growth factors and cell surface recognition molecules, such as integrins and selections. Little is known of the mechanisms that preserve the integrity of local microenvironments and how subpopulations of cells are transiently retained in microenvironments during various maturational states. Different lymphoid cells develop in bone marrow and thymus despite the similarities in stromal cells of these tissues. It remains a major quest to determine how the components of microenvironments of these organs regulate lineage-specific differentiation. The focus here is on stromal cells, the early development of myeloid cells and B lymphocytes in bone marrow and T lymphocytes in the thymus.

Synergistic suppression: anomalous inhibition of the proliferation of factor-dependent hemopoietic cells by combination of two colony-stimulating factors

Cells of the continuous murine hemopoietic cell line FDC-P1 expressing macrophage-colony-stimulating factor (M-CSF) receptors following retroviral insertion of murine c-fms cDNA proliferated clonally when stimulated by granulocyte/macrophage (GM)-CSF, multipotential CSF, or M-CSF. However, M-CSF combined with either GM-CSF or multi-CSF, even at low CSF concentrations, strongly inhibited colony formation, with loss of clonogenicity in affected cells accompanied by increased macrophage differentiation. Stimulation by these CSF combinations did not induce short-term changes in CSF receptor expression or internalization. FDC-P1 cells expressing another inserted tyrosine kinase receptor, basic fibroblast growth factor receptor, did not exhibit suppression when GM-CSF was combined with fibroblast growth factor. This phenomenon of synergistic suppression may have relevance for the future clinical use of combinations of CSFs, because a potentially similar suppression is also observable with some normal macrophage progenitor cells.

Novel fold and putative receptor binding site of granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the development of and the cytotoxic activity of white blood cells. Recombinant human GM-CSF has proven useful in the treatment of blood disorders. The structure of GM-CSF, which was determined at 2.4 angstrom resolution by x-ray crystallography, has a novel fold combining a two-stranded antiparallel beta sheet with an open bundle of four alpha helices. Residues implicated in receptor recognition, which are distant in the primary sequence, are on adjacent alpha helices in the folded protein. A working model for the receptor binding site is presented.