[The comparative characteristics of antibacterial properties of the peptides of the active site of GM-CSF, and substances delivered from supernatants of hematopoietic progenitor CD34+45- cells]

The antibacterial activity of synthetic peptides of the active site of GM-CSF and supernatants of CD34+45- hematopoietic progenitor cells has been investigated GM-CSF peptides and cell supernatants were found to possess pronounced antibacterial activity, at that a combination of these substances has a more pronounced activity in comparison with the single substances. Possible mechanisms of the identified effects of synthetic peptides and substances from the supernatants of CD34+5- cells are discussed.

Cytopenias in HIV infection: mechanisms and alleviation of hematopoietic inhibition

Hematopoietic abnormalities including anemia, cytopenias, and alterations of the stem cell plasticity in the bone marrow microenvironment commonly occur in HIV infected patients. These observations suggest that HIV-1 infection may affect processes important during early stages of hematopoiesis or stem cell differentiation. Hematopoietic abnormalities may be caused by altered stem cell differentiation possibly due to abnormal lineage specific expression of certain cellular genes such as cytokines relevant to hematopoiesis. These cytokines could affect regulatory signals important in hematopoiesis. However, in HIV infected individuals, it is not only the virus but also the highly active antiretroviral therapy (HAART) that both contribute to persistent hematopoietic suppression and ensuing cytopenias. Even if a lowering of HIV replication by HAART were to occur in infected individuals, prolonged HAART by itself and/or appearance of drug resistant mutants can contribute to hematopoietic suppression and resulting cytopenias. However, confounding factors such as opportunistic infections, immune mediated effects, or the consequences of prolonged physiological stress, which could contribute to decreased hematopoiesis in patients or other individuals, make the causative role of HIV in vivo, uncertain. The severe combined immunodeficient mouse transplanted with human fetal thymus and liver tissues (SCID-hu) is a small animal model which mimics HIV infection in humans, and is useful to determine the mechanisms of HIV-1 induced hematopoietic inhibition and development of drug therapies for interventions of stem cell differentiation. Further, SCID mouse serves as a useful small animal recipient of human progenitor cells and also allows us to study the differentiation of these cells in vivo. Results from our studies are expected to provide relief for HIV infected individuals from hematopoietic inhibition and ensuing cytopenias.

Therapeutically-induced autoantibodies in patients treated with recombinant hematopoietic growth factors: a brief summary

Since recombinant gene technology was established to provide rare important regulatory proteins as recombinant molecules, cytokine therapies have widely developed and enormously contributed to the treatment of various diseases; nevertheless, it has been revealed that recombinant therapeutic molecules are not always perfect because of side-effects related to pharmacological functions of cytokines and/or potential antigenicity observed in some clinical cases. Although studies on the antigenicity of recombinant proteins have initiated, and observations in clinical studies have been accumulated over this decade, mechanisms of the autoantibody production are not clarified yet. Among various hematopoietic growth factors introduced into clinical trials, this report summarizes current issues of autoantibodies to primary regulators for terminal hematopoiesis.

Lymphokine-dependent proliferation of T-lymphoid cells: regulated responsiveness and role in vivo

The discovery of lymphokines stemmed from their ability to promote T-lymphocyte proliferation in vitro. Even after 20 years of intensive investigation, crucial aspects remain to be clarified about the role of specific lymphokines in T-cell proliferation and the biochemical mechanisms by which they play these roles, particularly in vivo. The present review focuses on conventional populations of TCR(alpha)beta T cells. Older findings and new insights into the function of specific lymphokines in T-lymphocyte proliferation in vivo are summarized along with unanswered questions raised by these observations. Vital contributions of lymphokines to clonal proliferation arise from two processes: the protection of cells against apoptosis and the activation of cell cycling. Findings are underscored indicating that the activity of a particular lymphokine depends on the subset of T cells (CD4 vs. CD8; naive vs. memory) to which it binds, and that point to potential pitfalls of extrapolating from tissue culture-adapted models to the regulation of T cells in vivo. After summaries of signaling mechanisms related to the proliferative activity of lymphokines, recent findings are highlighted suggesting that such signaling is a regulated and plastic process rather than one fixed schema of action.

Perinatal immunomodulation

The fetus and the neonate are particularly vulnerable to injury caused directly by immunologic mechanisms or inflicted by infectious agents that take advantage of their relatively immature and inexperienced immune system. With increasing survival of high-risk neonates in the surfactant era, prevention/treatment of sepsis and chronic lung disease (CLD) has emerged as an area of priority in neonatal research. Considering the role of inflammatory mediators in the pathogenesis of sepsis and CLD, the clinical application of immunomodulator therapy to neonatology is perhaps more important at present than ever. Advances in molecular biology and immunology have led to development of newer immune modulator therapies that are directed towards specific cells or cytokines rather than resulting in a general suppression of the immune response. Failure of promising, newer immunomodulator therapies in sepsis trials in adults has, however, clearly documented the difficulties in diagnosing/correcting the imbalance between pro- and anti-inflammatory responses. As in the case of sepsis, development of a single magic bullet for prevention/management of a multi-factorial illness like CLD may be difficult, as prevention of prematurity - the single most important high-risk factor for CLD - is an unachievable goal at present. As new frontiers are being explored, older, well-established therapies like antenatal anti-D immunoglobulin prophylaxis continue to emphasize the tremendous potential of immunomodulator therapy in neonatology/perinatology. The current immunomodulators/immunotherapeutic agents with established/potential clinical applications in the perinatal period are reviewed.

Hematopoietic growth factors, dendritic cell biology, and vaccine therapy of cancer

Hematopoietic growth factors have made it possible to collect, manufacture, and engineer dendritic cells ex vivo for clinical use and expand dendritic cell subsets in vivo when administered to patients. Dendritic cells are important vectors in the induction of an effective immune response against infection and neoplastic disease. Antigens alone, even those preprocessed to bind to antigen-presenting major histocompatibility complex class I and II molecules, are insufficient to regulate effective T-cell-mediated immunity. Activated dendritic cells are essential to this task. Studies of dendritic cell biology in the laboratory and preclinical studies have facilitated the implementation of clinical trials using dendritic cells in the treatment of melanoma and other cancers. Dendritic cell subset functional differences, effective tumor target antigen loading of dendritic cells for presentation to immune effector cells, dendritic cell maturation, the route of dendritic cell administration to humans, and immunologic monitoring are parameters that require vigorous study in the context of dendritic cell immunotherapy of cancer.

Augmentation of the immune response with granulocyte-macrophage colony-stimulating factor and other hematopoietic growth factors

Granulocyte-macrophage colony-stimulating factor is by far the most widely used hematopoietic growth factor to augment immune responses. At present, the best secured effect is as an adjuvant cytokine for vaccination. Granulocyte-macrophage colony-stimulating factor can be delivered as gene-transduced tumor cells, as plasmid DNA, or as the soluble free granulocyte-macrophage colony-stimulating factor protein. Granulocyte-macrophage colony-stimulating factor must be present at the same site as the vaccine component. Granulocyte-macrophage colony-stimulating factor may also augment the effect of therapeutic monoclonal antibodies by enhancing various effector functions such as antibody-dependent cellular cytotoxicity and amplifying an idiotypic network response (i.e., antitumor immunity). It may also be advantageous to combine granulocyte colony-stimulating factor with monoclonal antibodies (neutrophil and monocyte antibody-dependent cellular cytotoxicity) for tumor therapy. However, these growth factors might also induce immune suppression, which may hamper the contemplated effect of the growth factor. It is urgently warranted to better understand these dual effects on the immune system so that we can find optimal uses for the growth factors in various clinical settings.

Human dendritic cells require exogenous interleukin-12-inducing factors to direct the development of naive T-helper cells toward the Th1 phenotype

Dendritic cells (DC) are important initiators of specific primary immune responses because they are the only APC that can efficiently activate naive Th cells. DC have the capacity to produce interleukin-12 (IL-12), a cytokine that plays a pivotal role in the development of Th1-mediated cellular immune responses. The present study focuses on the conditions under which human DC produce bioactive IL-12 p70 and, consequently, direct the development of naive T helper (Th) cells toward the Th1 phenotype. Bacteria or bacterial compounds such as Staphylococcus aureus Cowan strain I (SAC) or lipopolysaccharide (LPS) induced substantial IL-12 levels in DC, which could be further upregulated by interferon-gamma (IFN-gamma), whereas induction of IL-12 production via CD40 ligation required IFN-gamma as an obligatory, complementary signal. Also, activated naive Th cells were poor inducers of IL-12 production, unless exogenous IFN-gamma was present, whereas activated memory Th cells were effective inducers of IL-12 production and did not require exogenous IFN-gamma. Next, the cytokine profiles of matured Th cells that were primed by DC under different conditions were examined. DC promoted the development of naive Th cells into memory Th0 cells that produced both the type 1 cytokine IFN-gamma and the type 2 cytokine IL-4. In contrast, after activation with SAC, DC efficiently directed the development of Th1 cells through the release of IL-12. An APC-independent Th cell maturation model, using either recombinant IL-12 or supernatants of SAC-activated DC and neutralizing anti-IL-12 antibodies, confirmed that DC-derived IL-12 was the major Th1 skewing factor. Together, these data indicate that the contact between DC and naive Th cells during the initiation of specific immune responses does not result in the efficient induction of IL-12 production and that, consequently, exogenous IL-12-inducing factors are required to promote primary Th1-mediated cellular immune responses.

Allergen-induced increase in bone marrow progenitors in airway hyperresponsive dogs: regulation by a serum hemopoietic factor

We have previously reported that bone marrow progenitors in dogs, specifically granulocyte-macrophage colony-forming units (GM-CFU), increase developing airway hyperresponsiveness after inhalation of the allergen Ascaris suum. In the present study, we evaluated whether this increased marrow hemopoietic activity can be stimulated by a factor in serum after allergen challenge. Serum samples taken from dogs prior to and 20 min, 2 h, and 24 h after Ascaris or diluent challenge were added to bone marrow cells aspirated prior to challenge, and GM-CFU measured. A second bone marrow aspirate was performed 24 h after challenge. Nonadherent mononuclear bone marrow cells were incubated for 8 days in the presence of the serum and recombinant canine hemopoietic cytokines (stem cell factor, granulocyte colony-stimulating factor, GM colony-stimulating factor). Eight dogs that developed (airway responders) and eight dogs that did not develop (airway nonresponders) allergen-induced airway hyperresponsiveness were studied. Allergen inhalation increased bone marrow GM-CFU in response to all three growth media in vitro for the airway responder (P < 0.05) but not airway nonresponder dogs. The 24-h serum, taken from the airway responder but not the airway nonresponder dogs, produced a similar increase in granulocyte progenitors when added to the bone marrow taken before allergen inhalation (P < 0.05). These findings demonstrate that bone marrow-derived granulocyte progenitors are upregulated by a factor that can be shown to be present in serum 24 h after allergen challenge in dogs that develop allergen-induced airway hyperresponsiveness. Whether in vivo stimulation of bone marrow inflammatory cell production is necessary for the development of allergen-induced airway hyperresponsiveness remains to be proven.

Stem cell factor contributes to intestinal mucosal mast cell hyperplasia in rats infected with Nippostrongylus brasiliensis or Trichinella spiralis, but anti-stem cell factor treatment decreases parasite egg production during N brasiliensis infection

We assessed the effects of the c-kit ligand, stem cell factor (SCF), in the jejunal mucosal mast cell hyperplasia that occurs during infection with the intestinal nematodes, Nippostrongylus brasiliensis or Trichinella spiralis in rats. Compared with vehicle-treated rats, rats treated with SCF (25 micrograms/kg/d, intravenous [i.v.] for 14 days) during N brasiliensis infection exhibited significantly higher levels of the rat mucosal mast cell (MMC)-associated protease, rat mast cell protease II (RMCP II) in the jejunum and serum on day 8 of infection, but not on days 10 or 15 of infection. By contrast, in comparison to rats treated with normal sheep IgG, rats treated with a polyclonal sheep antirat SCF antibody exhibited markedly decreased numbers of jejunal MMCs, levels of jejunal RMCP II, and serum concentrations of RMCP II during infection with either nematode, particularly at the earlier intervals of infection (< or = day 10). Taken together, these findings indicate that SCF importantly contributes to MMC hyperplasia and/or survival during N brasiliensis or T spiralis infection in rats, but that levels of endogenous SCF are adequate to sustain near maximal MMC hyperplasia during infection with these nematodes. Notably, treatment of rats with SCF somewhat increased, and treatment with anti-SCF significantly decreased, parasite egg production during N brasiliensis infection. This finding raises the interesting possibility that certain activities of intestinal MMCs may contribute to parasite fecundity during infection with this nematode.

Murine spleen stromal cell line SPY3-2 maintains long-term hematopoiesis in vitro

The hematopoietic microenvironment (HIM) of mouse spleen predominantly induces the differentiation of hematopoietic progenitors into erythroid lineage in vivo. However, the mechanisms of this phenomenon have not been fully explored because of the lack of an adequate in vitro system mimicking the spleen hematopoiesis. To reconstruct the HIM of mouse spleen in vitro, we established spleen stromal cell lines from a three-dimensional (3D) spleen primary culture in collagen gel matrix. Of these, SPY3-2 cells were negative for preadipocytic and endothelial markers, had a fibroblastoid morphology, and were not converted to adipocytes in the presence of 1 mumol/L hydrocortisone. They supported the maintenance and multilineal differentiation of hematopoietic progenitor cells for more than 8 weeks in vitro. The differentiated hematopoietic cells in the coculture medium were predominantly monocytes rather than granulocytes. Furthermore, erythropoiesis was predominantly induced in the presence of 2 U/mL erythropoietin and continued for more than 12 weeks. The number of burst-forming units-erythroid (BFU-E) was increased 10 times after 3 weeks of coculture, which was followed by pronounced production of erythroid cells in the coculture after week 4. SPY3-2 expressed high levels of c-kit ligand and low levels of granulocyte macrophage colony-stimulating factor and interleukin-3, and these molecules were all involved in this long-term erythropoiesis. Thus, the clonal SPY3-2 cell line will provide a novel HIM in vitro analogous to that of mouse spleen in vivo. These results suggest that 3D collagen gel culture may facilitate the establishment of functioning stromal cell lines of hematopoietic organ.

Immunological and biochemical characterization of biglycan-like haemopoietic factor

Immunological and biochemical characteristics of a 100,000 MW biglycan-like haemopoietic factor, purified from thymic myoid cells 871207B, were studied to distinguish them from macrophage colony-stimulating factor (M-CSF), which they resemble in activity and biochemical properties. Rabbit antibody raised against a synthetic peptide fragment (J-1) designed from amino acid sequences specific to the 100,000 MW factor responded to 871207B cells, the conditioned medium of 871207B, and capillary-like structures in the thymus, but not to M-CSF producer L-929 cells or the conditioned medium of L-929 cells. In contrast, M-CSF epitope was detected in L-929 cells and the conditioned medium cells but not in 871207B cells or the conditioned medium, even after enzymatic digestion of glycosaminoglycan chains. Treatment of the 100,000 MW factor with chondroitinase ABC and AC produced a 50,000 MW component. Digestion of this product with N-glycanase resulted in a 40,000 MW protein component. These results suggest that the 100,000 MW factor is a proteoglycan consisting of a core protein with an apparent molecular mass of 40,000 MW, a 50,000 MW chondroitin sulphate chain and 10,000 MW N-linked oligosaccharide chains. A small amount of a 40,000 MW monocytic cell growth activity was also found in the 871207B cell-conditioned medium. An enzymatically obtained 40,000 MW factor, the conditioned medium 40,000 MW factor, and the 100,000 MW factor were specifically eluated from an anti-J-1 IgG-immobilized affinity column with monocytic cell growth activity, suggesting that the biological activity resides in the 40,000 MW core protein. The 100,000 MW factor induced the proliferation and differentiation of monocytic lineage cells from a variety of sources, such as bone marrow cells, peritoneal exudated cells and brain microglia cells.

Ultrastructural localization of stem cell factor in canine marrow-derived stromal cells

Stromal cell lines derived from canine long-term bone marrow cultures (LTBMC) were characterized regarding the expression of growth factors and especially the localization of stem cell factor (SCF) (c-kit ligand). One cell line (DO64) was immortalized by transformation with a retroviral vector containing the open reading frames (ORFs) E6 and E7 of the human papilloma virus type 16 (HPV-16). Transfection did not change cellular characteristics but rendered the cell line more independent from culture conditions. The transformed line DO64 consisted mainly of fibroblast-like cells. In addition, some cells showed endothelial and some smooth-muscle cell features. Stromal cells expressed a broad spectrum of surface markers, including low levels of major histocompatibility-complex (MHC) class-II antigens. A new murine monoclonal antibody (MAb), RG7.6 (IgG1), specific for canine SCF, recognized the majority of fibroblast-like stromal cells. The staining pattern for SCF showed perinuclear and intracytoplasmic dense areas. Immunoelectron microscopy revealed the localization of SCF in secretory vesicles, the perivesicular cytoplasm, and bound to the cytoplasmatic membrane. RNA analysis showed that stromal cells transcribed, in addition to SCF, messages for granulocyte colony-stimulating factor (G-CSF), granulocyte-monocyte CSF (GM-CSF), interleukin-6 (IL-6), and transforming growth factor-beta (TGF-beta). In summary, we have established and characterized canine marrow-derived stromal cell lines, and using the new MAb RG7.6, we have localized SCF to cytoplasmatic vesicles as well as the membrane of stromal cells.

Kit ligand/mast cell growth factor-independent differentiation of mast cells in myelodysplasia and chronic myeloid leukemic blast crisis

Autonomous, factor-independent growth and differentiation of malignant cells in preleukemic and leukemic disease states is a well-recognized phenomenon and is often associated with a poor prognosis. Mast cells are distinct hematopoietic cells and express a unique profile of antigens. Growth and differentiation of normal mast cells is dependent on mast cell growth factor (MGF), the ligand of the c-kit protooncogene product. In this study, we screened for mast cell-lineage involvement in 52 patients suffering from myeloid leukemias, myelodysplastic syndromes (MDS), systemic mastocytosis, or other diseases by probing for mast cell-related molecules (c-kit, tryptase, histamine, and MGF) and by analyzing kit ligand/MGF-independent growth of mast cells in long-term suspension culture. Of the 52 patients tested, 2 patients with refractory anemia with excess of blast cells in transformation and 1 patient suffering from chronic myeloid leukemia blast crisis (CML-BC) were diagnosed as mastocytic disease. These patients were characterized by complex chromosomal abnormalities, splenomegaly, high percentages of circulating metachromatic cells (5% to 25%), high levels of cellular tryptase (> 10 ng/10(5) peripheral blood mononuclear cells/mL) and a tryptase/histamine (ng:ng) ratio greater than 1. The metachromatic cells expressed the mast-cell-related surface antigen c-kit, but not basophil-related antigens (CD11b, CDw17). Furthermore, in these 3 patients, spontaneous, MGF-independent growth of mast cells along with spontaneous synthesis of tryptase was demonstrable in long-term culture. No autocrine production, paracrine production, or overproduction of MGF was found. The spontaneous growth of mast cells could neither be abbrogated by addition of monoclonal antibodies (MoAbs) to c-kit nor by MoAbs against MGF (< 5% inhibition), whereas factor (MGF)-dependent differentiation of mast cells in these patients could be abbrogated by MoAbs to c-kit or MoAbs to MGF (> 70% inhibition, P < .001). In addition, serum MGF levels in these patients were within the normal range and MGF could not be detected in cell-free culture supernatants. All 3 patients showed rapid progression of disease and had a survival time of less than 1 year. In conclusion, we describe a unique form of transformation in MDS and CML-BC characterized by mast cell lineage involvement and factor-independent differentiation of mast cells. This form of leukemic transformation has to be delineated from chronic myeloid leukemia with basophilia or basophil crisis, from primary mast cell leukemia, and from monocytic leukemias and myelodysplastic disorders associated with basophilia.

Interactions between stem cell factor and c-Kit are required for intestinal immune system homeostasis

Interactions between stem cell factor (SCF) and its receptor, c-Kit, are important for development of hematopoietic, melanocytes, and germ cells. T lymphocytes appeared normal in c-Kit (W/Wv) or SCF (SI/SId) mutant mice, except for those residing within the intestinal epithelium, the intraepithelial lymphocytes (IEL). Normally, IEL are composed of equal numbers of cells with alpha beta or gamma delta T cell receptors. In mutant mice, beginning at 6-8 weeks of age, the number of gamma delta IEL decreased, whereas alpha beta IEL increased. The latter was due largely to an increased CD4+ CD8+ TCR alpha beta subset, suggesting that these cells may be intermediates in the alpha beta IEL lineage. c-Kit or SCF was expressed by IEL or intestinal epithelial cells, respectively, indicating a potential for direct intercellular interaction. This possibility was supported by reconstitution studies that demonstrated that c-Kit mutations directly affected IEL. Thus, SCF-c-Kit interactions are important for homeostasis of the intestinal immune compartment.

Effect of hematopoietic growth factors on human blood monocytes/macrophages in in vitro culture

The production of mature monocytes/macrophages is regulated by a group of hematopoietic growth factors, or colony-stimulating factors (CSF). We investigated the in vitro effect of human hematopoietic growth factors on human blood monocyte/macrophage differentiation and proliferation in short- and long-term in vitro cultures. The addition of macrophage CSF, granulocyte-macrophage CSF, and granulocyte CSF and interleukin-6 and interleukin-3 growth factors to monocyte/macrophage cultures induced morphological changes in cultured cells, including enhancement of cell growth and the formation of multinucleated giant cells, spindle-like cells, and fibroblast-like cells. In addition, CD4 and HLA-DR antigen expression was down regulated by the addition of growth factors without a change in the expression of other surface antigens, including CD3, CD11B, CD14, CD15, NK H1, and B1. The proliferating cell nuclear antigen was not detected in growth factor-treated nonadherent monocytes/macrophages in long-term cultures. Bromodeoxyuridine was incorporated in the adherent monocytes/macrophages, and intense staining in the small rounded cells which occur above the adherent cells in these cultures was observed after a 72-h pulse, indicating that monocytes/macrophages are slowly dividing cells.

IL-12 protects bone marrow from and sensitizes intestinal tract to ionizing radiation

IL-12, a potent stimulator of hemopoietic progenitor cells, was evaluated as a potential protector against 60Co-gamma radiation-induced lethal hemopoietic syndrome in mice. Administration of IL-12 before lethal irradiation of genetically distinct strains of mice, B6D2F1 and C3H/HeJ, protected a significant fraction of both strains of mice from death. Radioprotection was associated with a fivefold increase in the number of bone marrow cells at 6 days after irradiation. Even at supralethal doses of radiation (1200 cGy), the number of c-kit+ bone marrow cells 3 days after irradiation was twofold greater in IL-12-treated mice than in saline-treated mice. However, mice that received IL-12 and 1200 cGy (B6D2F1) or 900 cGy (C3H/HeJ) died of the gastrointestinal syndrome, as was evident by gross necroscopy and histologic evaluation, within 4 to 6 days after irradiation. Induction of the gastrointestinal syndrome in mice not treated with IL-12 required radiation doses of 1500 cGy or greater in both strains. Thus, at doses of radiation at which IL-12 still protects c-kit+ hemopoietic cells, it sensitizes the intestinal tract to damage. Radioprotection with IL-12 was abrogated by anti-IL-1R or anti-stem cell factor Ab. Anti-IFN-gamma Ab did not affect IL-12-induced hemopoietic radioprotection, but abrogated sensitization of the intestinal tract by IL-12. The sensitizing effect of IL-12 may be related to its ability to prime mice to subsequent inflammatory challenge, as demonstrated by an almost 100-fold increase in circulating TNF and IL-6 levels in normal B6D2F1 mice challenged with IL-12 and LPS. This priming effect of IL-12 also was abrogated by anti-IFN-gamma Ab.

Overview of the role of hematopoietic growth factors in bone marrow transplant recovery and bone marrow transplant failure

Morbidity of bone marrow transplantation has been reduced by the prophylactic use of myeloid stimulating growth factors. Trials are current exploring the usage of hematopoietic growth factors in a variety of other potential clinical applications in bone marrow transplantations. These include stimulation of multipotent progenitor cells, enhancement of monocyte macrophage function, enhancement of lymphocyte function, and alteration of inflammatory mediators which are causal of nonhematologic toxicities of bone marrow transplantation. Hematopoietic growth factors, factors which induce production of stimulatory cytokines and/or factors which alter inflammatory pathways, may be effective in improving the tolerability of patients undergoing bone marrow transplant.

Clinical applications of hematopoietic growth factors

OBJECTIVE

To explore the history and current clinical uses of hematopoietic growth factors.

DATA SOURCES

Recent professional literature and texts dealing with recombinant DNA technology, the development of hematopoietic growth factors, and their use in various disease states.

STUDY SELECTION

Not specified.

DATA EXTRACTION

Not specified.

DATA SYNTHESIS

Hematopoietic growth factors are glycoproteins that regulate the differentiation and proliferation of hematopoietic precursor cells, and, in some cases, the function of mature blood cells. Several have been molecularly characterized and produced in quantity via recombinant DNA technology. Medically, hematopoietic growth factors can be used to replenish hematopoietic lineages by raising cell counts to normal levels; to augment host defenses against infection; to stimulate the immune system against malignancy; and to increase production of effector cells with cytotoxic activities.

CONCLUSION

In the past eight years, the hematopoietic growth factors have been used in a variety of clinical settings. They have proven to be effective in stimulating marrow proliferation, increasing circulating blood cell counts, and stimulating various host defense mechanisms. Others are in earlier stages of clinical studies, and their full therapeutic potential remains to be evaluated. New therapies are expected to emerge at a rapid pace.

Phenotypic characterization of stem cell factor-dependent human foetal liver-derived mast cells

Human foetal liver cells are an enriched source of mast cell progenitors that complete their differentiation and mature in response to stem cell factor, the ligand for Kit, in liquid culture. These mast cells are Kit+, metachromatic with toluidine blue+, tryptase+, histamine+ and show ultrastructure features of mast cells. Using a panel of monoclonal antibodies (mAb) against different cell-surface antigens (33 mAb were used), the cell-surface phenotype of human stem cell factor-dependent foetal liver-derived mast cells was examined by flow cytometry. Consistent with previous reports on tissue-derived mast cells, those derived from foetal liver in vitro expressed HLA class I, CD9, CD29, CD33, CD43, CD45 and Kit. Unlike mast cells dispersed from tissue, a high expression of CD13 was found. Also, these in vitro-derived mast cells express little, if any, high-affinity IgE receptor. However, small amounts of mRNA for the alpha-chain in foetal liver-derived mast cells compared to KU812 cells (a human basophil-like cell line) could be detected by Northern blotting. Full expression of Fc epsilon RI may require additional growth factor(s).

Effects of mast cell growth factor on acute myeloid leukemia cells in vitro: effects of combinations with other cytokines

We have investigated the stimulative effects of mast cell growth factor (MGF) in primary acute myeloid leukemia (AML) in vitro. MGF stimulated DNA synthesis of purified leukemic blasts in eight out of 10 cases and colony formation in four cases in serum-free (SF) culture. MGF synergized with interleukin-3 (IL-3; four out of 10 cases), granulocyte-macrophage colony-stimulating factor (GM-CSF; three out of 10 cases), granulocyte colony-stimulating factor (G-CSF; six out of 10 cases), macrophage colony-stimulating factor (M-CSF; one out of 10 cases) and erythropoietin (EPO; one out of 10 cases) when added to culture in combination. Synergistic effects of MGF in combination with other CSFs were also seen in the colony assay. Antibodies against GM-CSF, M-CSF, G-CSF, and IL-6 did not inhibit the MGF response, suggesting that the stimulative effect of MGF was not mediated through autocrine release of those cytokines. Cell recovery data in liquid cultures that contained MGF, IL-3, or MGF + IL-3, indicated that both MGF and IL-3 augmented the maintenance of clonogenic cells as compared to nonsupplemented cultures, but the effect of the combination of IL-3 + MGF did not show synergy. In contrast, activation of DNA synthesis by MGF was abrogated in the presence of tumor necrosis factor (TNF; four out of 10 cases) and interleukin-4 (IL-4; two out of 10 cases). Fluorescence-activated cell sorting (FACS) analysis with anti c-kit antibodies revealed MGF receptor expression in eight out of nine cases, often in a subpopulation of the cells. Scatchard analysis of MGF receptors in two cases indicated the presence of 1460 and 41,500 (mean) binding sites, respectively, of high affinity (Kd 40-160 pmol/l). The MGF dose-response curve in the presence of IL-3 or GM-CSF resulted in a higher plateau of DNA synthesis, however no shift in the dose response was apparent. The respective reciprocal dose response relations to GM-CSF, IL-3, or G-CSF were similarly elevated when MGF was added. MGF did not alter IL-3 and GM-CSF receptor expression, nor did IL-3, GM-CSF, G-CSF, TNF, or IL-4 influence MGF binding to AML cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Conditions required for myelopoiesis in murine spleen

While the spleen is an active site for myelopoiesis during the late embryonal and perinatal stages, the activity is gradually lost later. However, myelopoiesis in the adult spleen can be reactivated by irradiation or various stimulants. In this study we investigated factors which determine the myelopoiesis-supporting activity in the adult spleen. To address this question, we used scid mouse because virtually no lymphocytes, which might compete in the splenic microenvironment with hematopoietic progenitors, are present there. The results demonstrated: 1. Even in scid mouse, the myelopoiesis-supporting activity in the spleen is lost within a week after birth as in normal mice. 2. While myelopoiesis does not occur in the spleen of unstimulated scid mouse by bone marrow transfer alone, myelopoiesis in the spleen is reactivated by irradiation or lipopolysaccharide (LPS) application. 3. Myelopoiesis in the spleen induced by irradiation is dependent on c-kit and its ligand steel factor (SLF), because it was suppressed completely by the monoclonal antibody (mAb) against c-kit. 4. The expression of SLF transcripts in the spleen was enhanced after irradiation. These results suggest that the factor which determines myelopoietic activity in the spleen resides primarily in the status of the splenic microenvironment.

Maintenance of high levels of pluripotent hematopoietic stem cells in vitro: effect of stromal cells and c-kit

We show here that mouse pluripotent hematopoietic stem cells can be maintained in vitro on stroma for at least 3 weeks at levels close to those found in bone marrow. The extent of stem cell maintenance is affected by the nature of the stromal cells. The stromal cell line S17 supported stem cells significantly better than heterogeneous, primary stromal layers or the stromal cell line Strofl-1. Stem cells cultured on S17 repopulated all hematopoietic lineages in marrow-ablated hosts for at least 10 months, indicating that this culture system maintained primitive stem cells with extensive proliferative capacity. Furthermore, we demonstrate that, while pluripotent stem cells express c-kit, this receptor appears to play only a minor role in stem cell maintenance in vitro. The addition of an antibody that blocks the interaction of c-kit with its ligand essentially abrogated myelopoiesis in cultures. However, the level of stem cells in antibody-treated cultures was similar to that found in untreated cultures. Thus, it seems likely that the maintenance of primitive stem cells in vitro depends on yet unidentified stromal cell-derived factor(s).

Kit ligand in synergy with interleukin-3 amplifies the erythropoietin-independent, globin-synthesizing progeny of normal human burst-forming units-erythroid in suspension cultures: physiologic implications

Although the proliferative effects of hematopoietic cytokines on erythroid progenitors are well known, parameters that influence the initiation of expression of specialized or lineage-restricted genes are not clear. We have studied the acquisition of erythroid-differentiative features from enriched populations of human early erythroid progenitors (burst-forming unit-erythroid [BFUe]) in suspension culture and the influence of several cytokines on this process. In suspension cultures containing no erythropoietin (Epo), we have found that kit ligand (KL) in synergy with interleukin-3 not only increases the proliferation of cells and of progenitors but also consistently amplifies a population of cells that contain globin within 1 week. Our experiments suggest that neither extraneously provided nor endogenously produced Epo is critical for the generation of globin-synthesizing cells. Globin-producing cells generated mostly from late BFUe or pre-CFUe with a CD34-/EP-1+ phenotype in this system do not all express a well-coordinated erythroid program accompanied by heme or glycophorin A expression and most die maintaining an immature state. Therefore, conditions that are responsible for initiation of globin expression in these cells are not sufficient to carry them to terminal maturation. The data point to an expanded target cell population for KL, as they suggest an influence of KL on survival and/or amplification of late erythroid cells previously thought to be influenced only by Epo. Our results in aggregate are of relevance to the physiology of normal erythropoiesis and the role of Epo and KL in the initial stages of lineage-restricted gene expression. In addition, they provide insight into the understanding of anemia in W and Steel mutants in which expansion of the late erythroid progenitor pool, normally dependent on the synergistic action of KL and Epo, is curtailed.

Inhibition of c-kit ligand/steel factor by antibodies reduces survival of lethally irradiated mice

Survival after irradiation with LD100/30 (radiation dose lethal to 100% of mice in 30 days) is based on recovery of impaired hematopoietic function. Our previous studies using antibodies to interleukin-1 receptor (IL-1R), tumor necrosis factor (TNF), and IL-6 demonstrated that endogenous production of these three cytokines is required for untreated mice as well as mice protected with lipopolysaccharide (LPS), IL-1, or TNF to survive lethal irradiation. In this report we show that anti-c-kit ligand/steel factor (SIF) antibody similarly abrogates LPS- and IL-1-induced radioprotection. Furthermore, administration of this antibody to unmanipulated mice increased LD50/30 radiation lethality from 50% to 100%. Such an effect was not obtained using anti-IL-3, anti-IL-4, or anti-granulocyte-macrophage colony-stimulating factor antibody. Thus, like IL-1, TNF, and IL-6, SIF is required for survival from lethal irradiation.

Specific activation of human mast cells by the ligand for c-kit: comparison between lung, uterus and heart mast cells

Recent data suggest that stem cell factor (SCF or c-kit ligand, KL) is a major regulator of human mast cells (MCs). In the present study, MCs derived from the lung (n = 8), uterus (n = 14) and heart (n = 4) were analyzed for expression of c-kit receptor and for responses to recombinant SCF. MCs of all organs tested were recognized by mAbs to c-kit (YB5.B8, SR-1) as assessed by combined toluidine blue/immunofluorescence staining. Activation by rhSCF (10 ng/ml, 60 min) resulted in histamine release from lung MCs (SCF 12.8 +/- 2.7% histamine release; control 2.8 +/- 0.8%, p < 0.01), uterus MCs (SCF 16.8 +/- 5.8%; control 5.2 +/- 2.5%, p < 0.01) and heart MCs (SCF 18.4 +/- 2.6%; control 1.7 +/- 0.23%, p < 0.01). Short-term pre-incubation with rhSCF (15 min) did not result in histamine secretion (p > 0.05), but in an increase (lung 2.4 +/- 1.0 fold; uterus 2.1 +/- 1.1 fold, and heart 2.0 +/- 0.4 fold) of alpha IgE-induced mediator release (p < 0.05). The effects of SCF were dose-dependent (maximum responses at 10-100 ng/ml) and dependent on extracellular calcium. A monoclonal antibody to SCF was found to inhibit the effects of SCF on MCs. Furthermore, MCs could be desensitized specifically by pre-incubation of MCs with rhSCF in Ca-free medium. Together, these data suggest that SCF triggers mediator secretion from MCs in various organs via binding to the c-kit receptor.

The in vivo role of stem cell factor (c-kit ligand) on mastocytosis and host protective immunity to the intestinal nematode Trichinella spiralis in mice

The role of stem cell factor (SCF) in the generation of intestinal mast cell hyperplasia and host protective immunity following helminth infection was investigated using the Trichinella spiralis/mouse model. In vivo administration of a monoclonal antibody specific for the receptor for SCF (c-kit) was found to completely prevent the generation of intestinal mastocytosis normally observed following T. spiralis infection. This was reflected by markedly reduced intestinal mast cell protease (IMCP) levels in both tissue and serum. Moreover, animals treated with anti-c-kit antibody failed to show any evidence of worm expulsion from the gut. The data demonstrate for the first time, a critical role for the SCF in the generation of mucosal mastocytosis and host protective immunity following an intestinal helminth infection.

Establishment of a murine pre-B cell clone dependent on interleukin-7 and stem cell factor

To identify cytokines required for proliferation of murine pre-B cells, we established a pre-B cell clone MH11 (B220+ MB-1+ sIgM-) on a stromal cell line ST2 from day 13 fetal liver. The growth of MH11 is dependent on ST2. Another stromal cell line PA6, non-secretor of IL-7, could not support MH11 unless IL-7 was added. We investigated the effect of cytokines on proliferation of MH11 with or without stromal cells. IL-7 had a stimulatory effect on proliferation of MH11, but IL-7 alone could not support MH11 growth without ST2. Recombinant stem cell factor (rSCF) also had a positive effect on MH11. rSCF and rIL-7, when added together, could maintain the growth of MH11 in the absence of stromal cells. Moreover, the growth of MH11 on ST2 was inhibited almost completely by anti-c-kit monoclonal antibody (mAb). These results demonstrate that direct SCF/c-kit interaction is involved in the stimulation of pre-B cells.

Steel factor stimulates the tyrosine phosphorylation of the proto-oncogene product, p95vav, in human hemopoietic cells

Steel factor (SF) (also called stem cell factor, mast cell growth factor, or c-kit ligand) is a recently cloned hemopoietic growth factor that is produced by bone marrow stromal cells, fibroblasts, and hepatocytes. In both mouse and man it acts synergistically with several colony stimulating factors, including interleukin-3 (IL-3) and granulocyte macrophage-colony stimulating factor (GM-CSF), to induce the proliferation and differentiation of primitive hemopoietic precursor cells. In order to study its mechanism of action and to explore the molecular basis for its synergistic activity we have examined the proteins that become tyrosine phosphorylated in response to SF, IL-3, and GM-CSF. We report herein that SF, but not IL-3 or GM-CSF, dramatically stimulates the tyrosine phosphorylation of the product of the recently discovered proto-oncogene, vav, in two SF-responsive human cell lines, M07E and TF-1. Although phosphorylation is very rapid, reaching maximal levels within 2 min at 37 degrees C, co-immunoprecipitation studies suggest that c-kit may either not associate directly with p95vav or bind to it with very low affinity. Nonetheless, our data suggest that c-kit may utilize p95vav to mediate downstream signaling in hemopoietic cells.

Lymphocyte development from stem cells

Highly enriched pluripotent and multipotent hematopoietic stem cells (HSCs) are isolated from bone marrow and fetal liver as Thy-1loLin-Sca-1+ cells. Pluripotent HSCs express c-kit receptor on their surface, but the generation and proliferation of early fetal HSCs take place in the absence of steel factor. T precursor cells migrate into the fetal thymus by chemotactic mechanism. CD4lo precursors represent a newly defined phase of T-cell development in the thymus between the bone marrow-derived stem cells and the CD4-8- intrathymic precursors. Only fetal, but not adult, HSCs have the capacity to differentiate into V gamma 3+ and V gamma 4+ T cells under the fetal thymic microenvironment, and HSC themselves may lose some of their developmental potential during ontogeny. It is postulated that HSCs are the locus of a complicated but precise developmental clock that may determine both the time-dependent closure of some gene loci (e.g. V gamma 3 and V gamma 4 T cell receptor, and embryonic and fetal globin) and the activation of others (e.g. the N nucleotide insertion machinery).

IL-4 regulates c-kit proto-oncogene product expression in human mast and myeloid progenitor cells

The c-kit proto-oncogene encodes the receptor for a novel hemopoietic cytokine, termed stem cell factor (SCF) or mast cell growth factor (MGF) according to its stimulating spectrum. The human receptor for SCF/MGF is expressed in a subset of normal bone marrow progenitor cells, in leukemic myeloid cells, and in mast cells. In the present study, the effects of recombinant human growth regulators (IL-1 through -9, granulocyte-macrophage/granulocyte/macrophage-CSF, IFN, and TNF) on c-kit proto-oncogene product expression were analyzed by indirect immunofluorescence, by using the anti-SCF/MGFR mAb YB5.B8, and Northern blot analyses, by using a c-kit oligonucleotide probe. Of all cytokines tested, IL-4 was found to down-regulate expression of YB5.B8 Ag in the human mast cell line HMC-1 (maximum inhibition, 51.05 +/- 16.36% mean fluorescence intensity of control; p less than 0.02), as well as in primary leukemic myeloid cells. IL-4 was also found to down-regulate expression of YB5.B8 Ag in normal enriched bone marrow progenitor cells. The effects of IL-4 on expression of YB8.B8 Ag in myeloid/mast cell progenitors was dose and time dependent (maximum effects observed on days 2 and/or 4, by using 50 U/ml of rIL-4) and could be neutralized by using anti-IL-4 mAb. Moreover, IL-4 was found to down-regulate expression of c-kit mRNA in leukemic myeloid cells as well as in HMC-1 cells. Together, these observations identify IL-4 as a regulator of c-kit proto-oncogene product expression in the human system. The effects of IL-4 on human hemopoietic progenitor cells and mast cells may be mediated in part through regulation of SCF/MGFR expression.

The role of monocyte-derived hemopoietic growth factors in the regulation of myeloproliferation in juvenile chronic myelogenous leukemia

Juvenile chronic myelogenous leukemia (JCML) is a rare pediatric malignancy characterized by marked hepatosplenomegaly, leukocytosis with prominent monocytosis, elevated fetal hemoglobin, no Philadelphia chromosome, and generally a poor prognosis. In vitro, JCML peripheral blood granulocyte-macrophage progenitors (granulocyte-macrophage colony-forming units, CFU-GM) demonstrate the unique characteristic of "spontaneous" proliferation at very low cell densities in the absence of exogenous growth factors. The "spontaneous" CFU-GM proliferation can be abolished by prior adherent cell (monocyte) depletion, suggesting a paracrine mode of cellular proliferation. Although previous studies using a [3H]thymidine ([3H]TdR) incorporation assay suggested an important role for granulocyte-macrophage colony-stimulating factor (GM-CSF) in JCML, many non-growth factor-related reasons for [3H]TdR incorporation and the relatively low level of inhibition of [3H]TdR uptake left those conclusions open to question. Therefore, we performed clonal CFU-GM assays, which more specifically reflect cytokine effects on CFU-GM, using JCML peripheral blood mononuclear cells (PBMNC) and neutralizing antibodies against GM-CSF, granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating (M-CSF), interleukin 3 (IL-3), interleukin 1 alpha (IL-1 alpha), interleukin 1 beta (IL-1 beta), interleukin 4 (IL-4), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF alpha), and interferon gamma (IFN gamma). Cultures containing anti-GM-CSF alone inhibited "spontaneous" JCML CFU-GM by 87% +/- 9% (mean +/- standard error of the mean [SEM]). No other anti-cytokine antibody produced a significant inhibition of CFU-GM growth. Various combinations of antibodies, excluding anti-GM-CSF, failed to demonstrate any synergistic inhibitory effects upon CFU-GM. Because this apparent paracrine cellular stimulation could be due to excessive cytokine production, by monocytes or other accessory cells, we examined cytokine levels in conditioned media from various JCML cell populations using enzyme-linked immunosorbent assays (ELISAs). Monocytes from only a minority of JCML patients produced higher than normal quantities of GM-CSF, G-CSF, IL-1 beta, IL-6, and/or TNF alpha, but no obvious pattern could be discerned. Further, only 7 of 15 JCML monocyte-conditioned media (MCM) had elevated GM-CSF, and 6 of 15 JCML patients had normal levels of all nine cytokines tested. The monocyte depletion experiments and the inhibition experiments with anti-cytokine antibodies taken together demonstrate clearly that the "spontaneous" growth of JCML CFU-GM in vitro critically depends on at least one monocyte-derived growth factor, GM-CSF.(ABSTRACT TRUNCATED AT 400 WORDS)

Current applications of monoclonal antibodies for the therapy of hematopoietic cancers

Recent trials of monoclonal antibodies in patients with leukemias or lymphomas have demonstrated the remarkable potency of these agents to kill tumor cells specifically and safely. New molecular biological and radiochemical techniques are also allowing rapid inroads into the remaining obstacles to this mode of therapy.

Hematopoietic stem-cell differentiation

Hematopoietic stem cells can be identified and isolated from hematopoietic tissues of mammalian hosts. Assay systems that solely reflect hematopoietic stem cell activity are being developed, and new cytokines that influence hematopoietic stem-cell proliferation and differentiation have been described. Differentiation pathways that lead to lymphoid stages of hematopoiesis have also been suggested.