Purification and biochemical characterization of human pluripotent hematopoietic colony-stimulating factor

Production of granulocyte colony-stimulating factor (G-CSF) by human cells: T lymphocyte-dependent and T lymphocyte-independent release of G-CSF by blood monocytes

To evaluate the production of granulocyte colony-stimulating factor (G-CSF) by human immune and inflammatory cells, an assay specifically measuring G-CSF activity in the presence of other cytokines was developed which was based on the proliferation of 32Dcl cells induced by G-CSF. Successful use of the 32Dcl cells to specifically measure G-CSF activity required the selection of cells highly responsive to G-CSF and with reduced responsiveness to interleukin 2 (IL 2) by intermittent culture in medium containing G-CSF. Furthermore, the addition of exogenous IL 2 to standards and experimental samples was necessary to ensure that the concentration of IL 2 was similar in all samples, since IL 2 directly stimulated the proliferation of 32Dcl cells and increased their responsiveness to G-CSF. A variety of stimuli were found to induce G-CSF release by blood monocytes. Lipopolysaccharide and monocyte adherence appeared to directly stimulate G-CSF release, whereas stimulation of G-CSF release from monocytes by mitogenic lectins required the presence of T lymphocytes. In all cases, release of G-CSF was detectable as soon as 4 h after stimulation and was essentially complete after 48 h. These findings indicate that G-CSF release can be initiated by a variety of pathways, and therefore suggest that the production of this mediator may occur in the course of many immune and inflammatory reactions.

Granulocyte colony-stimulating factor enhances interleukin 3-dependent proliferation of multipotential hemopoietic progenitors

In cultures of spleen cells from normal mice, recombinant human granulocyte colony-stimulating factor (G-CSF) supported the formation of multipotential blast cell colonies. Serial replating of the blast cell colonies in the presence of G-CSF, however, failed to demonstrate any direct effect of G-CSF on murine multipotential progenitors. We therefore examined the effects of G-CSF in combination with murine interleukin 3 on proliferation of murine blast cell colony-forming cells. The time course of total colony formation and multilineage colony formation by spleen cells harvested from mice 4 days after injection of 5-fluorouracil at 150 mg/kg was significantly shortened in cultures containing both factors in contrast with cultures supported by either factor alone. Serial observations of individual multipotential blast cell colonies (mapping) revealed that blast cell colonies emerged at random time intervals in the presence of interleukin 3 or G-CSF. The appearance of blast cell colonies, however, was significantly hastened in cultures containing both factors relative to cultures grown with either factor. In cultures of day-2 post-5-fluorouracil bone marrow cells, G-CSF in concentrations as low as 1 unit/ml revealed synergism with interleukin 3 in supporting the proliferation of multipotential progenitors. This synergistic activity may explain the previous in vivo studies suggesting the effects of G-CSF on apparent multipotential stem cells.

Human thymic epithelial cells directly induce activation of autologous immature thymocytes

To study the role that epithelial cells of the thymic microenvironment play in promoting activation of immature CD7+, CD2+, CD4-, CD8- (double-negative) human thymocytes, we have isolated thymocyte subsets from normal postnatal thymus and have cocultured autologous double-negative thymocytes with pure populations of thymic epithelial (TE) cells. We report that TE cells directly activate double-negative thymocytes to proliferate and that TE cells enhance the ability of double-negative thymocytes to proliferate in response to stimulation with exogenous interleukin 2. Activated double-negative thymocytes that proliferated in vitro in the presence of TE cells and interleukin 2 remained double-negative after 23 days in culture. Moreover, TE-cell culture supernatants in the absence of intact TE cells contain interleukin 1, interleukin 3, and granulocyte/macrophage-colony-stimulating factor activity for human bone marrow cells and can activate double-negative thymocytes to proliferate. Antibodies against interleukin 1 and against granulocyte/macrophage-colony-stimulating factor inhibited TE-cell-induced thymocyte activation. These data indicate that one role of TE cells in vivo may be to activate double-negative thymocytes to proliferate.

Effect of granulocyte colony stimulating factor on neutropenia induced by cytotoxic chemotherapy

A phase I/II study of granulocyte colony stimulating factor (G-CSF) was undertaken in patients with advanced malignancy receiving melphalan to determine the granulocyte response, side-effects, and pharmacokinetics. Patients received doses of 1-60 micrograms/kg intravenously. There were 3 patients at each dose level. Before chemotherapy the immediate effect of G-CSF was a transient depression in circulating neutrophils followed by a dose-dependent rise. Neutrophil counts up to 80 X 10(9)/l were achieved. G-CSF administration following melphalan reduced the period of neutropenia caused by melphalan. G-CSF was well tolerated and the only clinical observation that appeared related to G-CSF administration was slight bone pain during some infusions. G-CSF was rapidly cleared from the blood with a mean half-life of 110 min for the second phase. Reductions in the number of days of neutropenia following cytotoxic chemotherapy may reduce the morbidity and mortality of chemotherapy.

Recombinant human granulocyte-macrophage colony-stimulating factor induces secretion of autoinhibitory monokines by U-937 cells

Colony-stimulating factors are required for survival proliferation, differentiation and functional activation of granulocytes, macrophages and their precursor cells. In the present report, however, we demonstrate antiproliferative activity of recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF) on monoblast cell line U-937 and provide evidence for the involvement of tumor necrosis factor alpha TNF-alpha and interleukin 1 beta (IL 1 beta) in its growth inhibitory action. GM-CSF (but not granulocyte CSF, G-CSF or macrophage CSF, M-CSF) suppressed DNA synthesis and self renewal of U-937 cells. Similarly, medium conditioned by U-937 cells in response to GM-CSF (GM-CSF U-937-CM) was able to reduce clonogenicity and [3H]thymidine uptake by U-937 cells. Since neutralization of GM-CSF present in GM-CSF U-937-CM by monoclonal antibody to GM-CSF did not abrogate the autoinhibitory activity present in GM-CSF U-937-CM, we considered the possibility that other soluble molecules are released by U-937 cells upon GM-CSF stimulation. Neutralization by antibodies to IL 1 beta and TNF-alpha suggested that both monokines could be the antiproliferative principle operating in GM-CSF U-937-CM. Moreover, employing IL 1 beta-specific enzyme-linked immunosorbent assay, TNF-alpha specific radioimmunoassay, Northern analysis using a cloned TNF-alpha-specific cDNA and an oligonucleotide probe for IL 1 beta, we demonstrate GM-CSF-inducible IL 1 beta and TNF-alpha gene expression by U-937 cells at the mRNA and protein level. Although M-CSF expression was induced under similar conditions, M-CSF failed to inhibit growth of U-937 cells.

Nuclear proteins interacting with the promoter region of the human granulocyte/macrophage colony-stimulating factor gene

The gene for human granulocyte/macrophage colony-stimulating factor (GM-CSF) is expressed in a tissue-specific as well as an activation-dependent manner. The interaction of nuclear proteins with the promoter region of the GM-CSF gene that is likely to be responsible for this pattern of GM-CSF expression was investigated. We show that nuclear proteins interact with DNA fragments from the GM-CSF promoter in a cell-specific manner. A region spanning two cytokine-specific sequences, cytokine 1 (CK-1, 5' GAGATTCCAC 3') and cytokine 2 (CK-2, 5' TCAGGTA 3') bound two nuclear proteins [nuclear factor (NF)-GMa and NF-GMb] from GM-CSF-expressing cells in gel retardation assays. NF-GMb was inducible with phorbol 12-myristate 13-acetate and accompanied induction of GM-CSF message. NF-GMb was absent in cell lines not producing GM-CSF, some of which had other distinct binding proteins. NF-GMa and NF-GMb eluted from a heparin-Sepharose column at 0.3 and 0.6 M KCl, respectively. We hypothesize that the sequences CK-1 and CK-2 bind specific proteins and regulate GM-CSF transcription.

Human platelet alpha granules contain a nonspecific inhibitor of megakaryocyte colony formation: its relationship to type beta transforming growth factor (TGF-beta)

Whole blood serum (WBS) and platelet-poor plasma-derived serum (PDS) from the same normal subject were compared for their abilities to support human megakaryocyte (MK) colony formation. In all cases, PDS promoted the growth of a higher number (20-50%) of MK colonies than did WBS. Increasing amounts of WBS decreased the number of colonies, whereas increasing concentration of PDS had no marked effects. Crude platelet extracts or platelet secretory products from thrombin-activated platelets also elicited an inhibition of MK colony formation in a dose-dependent manner. A complete inhibition was found for a dose equivalent to 1.10(9) platelets/ml and a 50% inhibition in a range of 1.10(7)-1.10(8) platelets/ml. These platelet products were also inhibitory for erythroid progenitor growth. Platelets from two patients with gray platelet syndrome elicited only a minor inhibition of MK growth, suggesting that the platelet alpha granule is the origin of this inhibition. When platelet extracts were acid-treated, the biological activity of the inhibitor on CFU-MK and CFU-E growth was 20-50-fold higher. In addition, a potent stimulatory activity on the growth of day 7 CFU-GM was observed. The enhancement of biological activities by acid treatment suggests that type beta transforming growth factor (TGF-beta) could be involved in this platelet inhibitory activity. The homogeneous native TGF-beta (from 1 pg to 1 ng/ml) produced the same effects previously induced by platelet products. It totally inhibited CFU-MK growth (at a 500 pg/ml), it inhibited CFU-E growth, and it stimulated growth of day 7 CFU-GM in the presence of a colony-stimulating factor. The inhibition of CFU-MK growth was also observed on purified progenitors. In conclusion, these results suggest that TGF-beta may be implicated in negative autocrine regulation of megakaryopoiesis. However, since this molecule has ubiquitous biological activities, its physiologic relevance as a normal regulator of megakaryopoiesis requires further investigation.

Detection of a human hematopoietic progenitor cell capable of forming blast cell containing colonies in vitro

A progenitor cell CFU-B1 (blast cell colony forming unit) present in human bone marrow and capable of producing blast cell containing colonies in vitro was detected using a serum containing semisolid culture system. The CFU-B1 has the capacity not only to undergo self-renewal, but also commitment to a number of hematopoietic lineages. This progenitor cell therefore has characteristics which suggest that it is identical to or closely related to the human pluripotent hematopoietic stem cell. Pretreatment of marrow cells with 5 fluorouracil facilitated detection of CFU-B1 derived colonies. The formation of CFU-B1 derived colonies was dependent upon the addition of media conditioned by the human bladder carcinoma cell line 5637. The ability of 5637 CM (conditioned media) to support blast cell colony formation was in part but not totally ablated by pretreatment of the CM with an IL-1 alpha (interleukin-1) neutralizing antibody. This data suggests that IL-1 alpha plays a role in the regulation of primitive events occurring during human hematopoiesis. IL-1 alpha might be exerting these effects by either acting directly on the CFU-B1, causing marrow accessory cells to elaborate other cytokines or by synergizing with cytokines already present in 5637 CM.

Early hemopoietic differentiation: the action of multi-CSF is complemented by lineage specific growth factors

Although mechanisms controlling differentiation of hemopoietic stem and early progenitor cells are still poorly understood, it is generally conceded that a pivotal role is played by hemopoietic growth factors (HGFs). However, in-vitro analysis of their action on early progenitors may be obscured by cell-cell interaction, as well as by the presence of fetal bovine serum (FBS). To overcome these limitations, we investigated the action of pure multipotent or lineage-specific HGFs on purified progenitors grown in FBS-free cultures. In the murine system, highly purified progenitors were cultured in the presence of multipotent colony-stimulating factor (multi-CSF, also termed interleukin-3), erythropoietin (Ep) and macrophagic-CSF (M-CSF). Each HGF was unable by itself to induce significant colony growth. However, combined addition of multi-CSF and either Ep or M-CSF gave rise only to pure erythroid or macrophagic colonies, respectively. Partly purified human progenitors were challenged by human granulomonocytic-CSF (GM-CSF), pluripotent CSF (PPO, also termed granulocytic-CSF, G-CSF) and Ep. Here again, each HGF was unable per se to promote colony growth, but combined addition of GM-CSF or PPO and Ep gave rise only to pure erythroid colonies. These results support a model of early hemopoietic differentiation according to which multi-lineage HGFs represent "competence" GFs, the action of which is complemented by lineage-specific "progression" HGFs.

Recombinant human macrophage colony-stimulating factor (M-CSF) requires subliminal concentrations of granulocyte/macrophage (GM)-CSF for optimal stimulation of human macrophage colony formation in vitro

Human macrophage colony-stimulating factor (M-CSF or CSF-1), either in purified or in recombinant form, is able to generate macrophagic colonies in a murine bone marrow colony assay, but only stimulates small macrophagic colonies of 40-50 cells in a human bone marrow colony assay. We report here that recombinant human granulocytic/macrophage colony stimulating factor (rhGM-CSF) at concentrations in the range of picograms enhances the responsiveness of bone marrow progenitors to M-CSF activity, resulting in an increased number of macrophagic colonies of up to 300 cells. Polyclonal antiserum against M-CSF did not alter colony formation of bone marrow progenitors incubated with GM-CSF at optimal concentration (1-10 ng/ml) for these in vitro assays. Thus, GM-CSF at higher concentrations (nanogram range) can by itself, elicit macrophagic colonies, and at lower concentrations (picogram range) acts to enhance the responsiveness of these progenitors to M-CSF.

Tumor-derived growth factors that support proliferation and differentiation of normal and leukemic hemopoietic cells

The conditioned media of 34 human tumor cell lines were screened for the ability to induce granulocyte-macrophage colonies in vitro in bone marrow cultures, to stimulate proliferation of a murine IL-3 dependent hemopoietic cell line (32D clone 3) and to stimulate thymidine incorporation in suspension cultures of acute myelogenous leukemia cells. Twelve tumor cell lines produced factors that were active in these assays. The conditioned medium of the glioblastoma cell line U87 MG was characterized in detail and found to contain G-CSF and GM-CSF. Cloning and sequencing of the U87 MG G-CSF indicated that it was derived from G-CSF b mRNA, which encodes a protein with a deletion of 3 amino acids at residues 36-38. The gene for G-CSF was mapped to human chromosome 17 band q21, a region involved in translocations frequently found in acute promyelocytic leukemia. G-CSF (U87MG) was able to induce granulocytic differentiation of the total population of a murine IL-3 dependent cell line, 32D clone 3; this effect was antagonized by IL-3. GM-CSF (U87-MG) supported the proliferation without inducing differentiation of two growth factor-dependent leukemic cell lines, TALL 101 and AML-193.

The regulation of hematopoiesis following bone marrow transplantation

Allogeneic bone marrow transplantation requires that donor stem cells home to the recipient bone marrow, proliferate and differentiate under normal physiologic regulatory mechanisms. Recent observations that T cell depletion of donor bone marrow leads to a greatly increased incidence of graft failure mandate a detailed understanding of the engraftment process. Post-transplant hematopoietic deficiencies appear to be related to several sources: decreased number of stem cells, activation of donor hematopoietic suppressor cells, rejection of donor stem cells by residual recipient lymphocytes and abnormal function of accessory cells that produce hematopoietic growth factors. A better understanding of the relative roles of these factors should lead to a better understanding of engraftment as well as graft failure and its prevention.

Synergy of interleukin 1 and granulocyte colony-stimulating factor: in vivo stimulation of stem-cell recovery and hematopoietic regeneration following 5-fluorouracil treatment of mice

The human bladder carcinoma cell line 5637 produces hematopoietic growth factors [granulocyte and granulocyte/macrophage colony-stimulating factors (G-CSF and GM-CSF)] and hemopoietin 1, which synergizes with CSFs to stimulate colony formation by primitive hematopoietic stem cells in 5-fluorouracil-treated mouse bone marrow. Molecular and functional properties of hemopoietin 1 identified it as identical to interleukin 1 alpha (IL-1 alpha). When bone marrow cells from 5-fluorouracil-treated mice were cultured in suspension for 7 days with recombinant human IL-1 alpha and/or G-CSF, it was found that the two factors synergized to enhance recovery of myelopoietic cells and colony-forming cells of both high and low proliferative potential. G-CSF alone did not sustain these populations, but the combination had greater-than-additive stimulating capacity. In vivo, 5-fluorouracil (150 mg/kg) produced profound myelosuppression and delayed neutrophil regeneration for up to 2 weeks in C3H/HeJ mice. Daily administration of recombinant human G-CSF or recombinant human IL-1 alpha accelerated recovery of stem cells, progenitor cells, and blood neutrophils by up to 4 days in 5-fluorouracil-treated C3H/HeJ and B6D2F1 mice. The combination of IL-1 alpha and G-CSF acted synergistically, reducing neutropenia and accelerating recovery of normal neutrophil numbers by up to 7 days. This was accompanied by accelerated regeneration of spleen colony-forming units and erythroid, myeloid, and megakaryocytic progenitor cells in marrow and spleen, with enhanced erythroid and granulocytic differentiation. These results indicate the possible therapeutic potential of combination therapy with IL-1 and hematopoietic growth factors such as G-CSF in the treatment of chemotherapy- or radiation-induced myelosuppression.

Defective in vitro growth of the hemopoietic progenitor cells in the acquired immunodeficiency syndrome

In addition to immunologic derangement, hematological abnormalities have been reported in the majority of patients with acquired immunodeficiency syndrome (AIDS). In this study 15 patients with AIDS or AIDS-related complex (ARC) were evaluated for the in vitro growth of hemopoietic progenitor cells. In all patients a significant reduction of growth (mean +/- SEM) of colony-forming unit-granulocyte, erythrocyte, macrophage, (megakaryocyte) (CFU-GEM) (1.2 +/- 0.3), burst-forming unit-erythroid (BFU-E) (17 +/- 10), CFU-megakaryocyte (CFU-Mk) (1.7 +/- 0.6), and CFU-granulocyte-macrophage (CFU-GM) (35 +/- 10) was observed in comparison with normal controls. Depletion of T cells from the bone marrow before culture led to a significant increase in colony growth, which indicated an imbalance of the normally modulating T cell subsets. This increase was reversed by readdition of autologous T cells causing a decrease in colony growth to a degree, dependent on the T4 to T8 ratio. A decreased number of hemopoietic progenitor cells and/or a defective modulation of progenitor cell growth, normally carried out by T lymphocyte subsets, might be the cause of the hematological abnormalities in AIDS patients.

The human hematopoietic colony-stimulating factors

The complementary DNAs and genes encoding the four major human myeloid growth factors--granulocyte colony-stimulating factor, macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and interleukin-3--have all been molecularly cloned. These DNA clones have proved valuable for studying the molecular biology of these important regulatory molecules as well as for the large-scale production of the recombinant growth factor proteins. These advances have led to a much better understanding of the role of the myeloid growth factors in regulating hematopoiesis in vivo that should soon find practical application in clinical medicine.

Recombinant murine granulocyte-macrophage (GM) colony-stimulating factor supports formation of GM and multipotential blast cell colonies in culture: comparison with the effects of interleukin-3

We studied the effects of murine recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) on murine hemopoiesis in methylcellulose culture. The GM-CSF was purified from cultures of Saccharomyces cerevisiae transfected with a cloned murine GM-CSF cDNA. In cultures of spleen cells from normal mice, only granulocyte-macrophage (GM) colonies were supported by GM-CSF. Blast cell colonies were the predominant type in cultures of spleen cells from 5-fluorouracil (5-FU)-treated mice. Dose-response studies revealed that maximal GM and blast cell colony formation is achieved with 100 U/ml GM-CSF. Blast cell colonies revealed variable but high replating efficiencies, and the secondary colonies included multilineage colonies. Serial replating of washed blast cell colonies in cultures with GM-CSF provided evidence for the direct effects of GM-CSF on the proliferation of multipotential blast cells. A combination of GM-CSF and interleukin-3 (IL-3) did not increase the number of blast cell colonies over the level supported by IL-3. This observation indicates that the progenitors for blast cell colonies that responded to GM-CSF are a subpopulation of multipotential progenitors that are supported by IL-3. Cytological studies of colonies derived from GM-CSF and/or IL-3 suggest that the eosinophilopoietic ability of murine GM-CSF is less than that of IL-3.

The chromosomal gene structure for murine granulocyte colony-stimulating factor

The chromosomal gene for murine granulocyte colony-stimulating factor (G-CSF) has been isolated from a mouse genomic library. The nucleotide sequence analysis of the gene and its flanking region has revealed that the murine G-CSF gene is composed of four introns and five exons, which is similar to the human G-CSF gene. The S1 mapping analysis of murine G-CSF mRNA has identified the major transcription initiation site for the murine G-CSF gene at 36 base pairs upstream of the ATG initiation codon. In the flanking region, there are sequences of about 300 base pairs which are highly conserved between human and murine G-CSF genes. The decanucleotide GAGRTTCCAC, which was found at the 5'-flanking region of genes for other hemopoietic growth factors, was also present within the corresponding regions of human and murine G-CSF gene. Unlike the human G-CSF gene, no alternative splicing was observed for the murine G-CSF gene.

Stimulation of oxidative metabolism of granulocytes by recombinant granulocyte-macrophage-colony-stimulating-factor and a conditioned medium of a urinary bladder carcinoma cell line

Neutrophils (PMN) are the major host defence cells protecting the body against invasion by microorganisms. Products of oxidative metabolism mediate PMN microbicidal and tumoricidal activity, but the mechanisms by which these pathways become activated are not well understood. The colony stimulating factors (CSF) are known to stimulate proliferation and differentiation of committed bone marrow stem cells. These regulators may probably play an important role in non specific resistance to infections. We studied the oxidative metabolism of neutrophils after stimulation with recombinant GM-CSF (r.GM-CSF) and the concentrated conditioned medium of the UBC-5637 cell line (UBC-CM) showing CSF activity. It could be demonstrated that the r.GM-CSF, as well as the UBC-CM, induce an activation of the neutrophil respiratory burst without any cofactors such as f-MLP, PMA, or zymosan. In addition, we observed an increase of the response to those stimulants in the presence of either r.GM-CSF or UBC-CM. These effects were not endotoxin-induced, since stimulation persisted after addition of Polymyxin B, which is known to inhibit the action of endotoxins.

In vivo stimulation of granulopoiesis by recombinant human granulocyte colony-stimulating factor

Osmotic pumps containing Escherichia coli-derived recombinant human granulocyte colony-stimulating factor (rhG-CSF) were attached to indwelling jugular vein catheters and implanted subcutaneously into Golden Syrian hamsters. Within 3 days, peripheral granulocyte counts had increased greater than 10-fold with a concomitant 4-fold increase in total leukocytes. Microscopic examination of Wright-Giemsa-stained blood smears from rhG-CSF hamsters showed that only the neutrophil subpopulation of granulocytes had increased. No significant changes in lymphocyte or monocyte counts were observed during the course of continuous rhG-CSF treatment. After subcutaneous injection at rhG-CSF doses of up to 10 micrograms X kg-1 X day-1 only granulocyte counts were affected. However, at higher dose levels, a transient thrombocytopenia was noted. Erythrocyte had lymphocyte/monocyte counts remained unaffected by rhG-CSF over the entire dose range (0.3-300 micrograms X kg-1 X day-1) studied. Total leukocyte counts increased 3-fold within 12 hr after a single s.c. injection of rhG-CSF. This early effect was associated with an increase in the total number of colony-forming cells and the percent of active cycling cells in the marrow. A sustained elevation of peripheral leukocyte and marrow progenitor counts was observed following seven daily s.c. injections of rhG-CSF. The ability of rhG-CSF to increase the production and release of granulocytes from the marrow may underlie the beneficial effect it produced on the restoration of peripheral leukocyte counts in hamsters made leukopenic by treatment with 5-fluorouracil.

Human megakaryocytic progenitor cells

Megakaryocytopoiesis represents one of several differentiation pathways that hematopoietic stem cells may enter. Cells representing intermediate stages of differentiation between pluripotent stem cells and maturing megakaryocytes are called megakaryocytic progenitor cells. They are identified in human bone marrow and peripheral blood by their ability to proliferate in culture (colony forming unit-megakaryocyte, CFU-M); at some point they lose the capacity for cell division and acquire the ability for endoreduplication of DNA, a phenomenon that is unique to the megakaryocyte lineage. This review summarizes current understanding of the biology of human megakaryocytic progenitor cells, including characterization of their proliferation potentials, their antigenic determinants, and the mechanisms that govern their proliferation and maturation. Finally the involvement of CFU-M in various disorders of thrombopoiesis is discussed.

Recombinant human granulocyte colony-stimulating factor. Effects on hematopoiesis in normal and cyclophosphamide-treated primates

We examined the in vivo effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in primates (cynomolgus monkeys) treated with subcutaneous doses of rhG-CSF for 14-28 d. A dose-dependent increase in the peripheral white blood cells (WBC) was seen, reaching a plateau after 1 wk of rhG-CSF treatment. The elevation of WBC was due to an increase in the absolute neutrophil count. These results demonstrate that rhG-CSF is a potent granulopoietic growth and differentiation factor in vivo. In cyclophosphamide (CY)-induced myelosuppression, rhG-CSF was able to shorten the time period of WBC recovery in two treated monkeys to 1 wk, as compared to more than 4 wk for the control monkey. Its ability to significantly shorten the period of chemotherapy-induced bone marrow hypoplasia may allow clinicians to increase the frequency or dosage of chemotherapeutic agents. In addition, the increase in absolute numbers of functionally active neutrophils may have a profound effect in the rate and severity of neutropenia-related sepsis. Furthermore, the activities reported here indicate a potential role for rhG-CSF in the treatment of patients with myelodysplastic syndrome, congenital agranulocytosis, radiation-induced myelosuppression, and bone marrow transplantation.

Comparative effects in vivo of recombinant murine interleukin 3, natural murine colony-stimulating factor-1, and recombinant murine granulocyte-macrophage colony-stimulating factor on myelopoiesis in mice

Purified murine colony-stimulating factors (CSF) recombinant interleukin 3 (IL-3), natural CSF-1, and recombinant granulocyte-macrophage (GM) CSF were assessed in vivo for their effects on BDF1 mouse bone marrow and spleen granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells in untreated mice and in mice pretreated with purified iron-saturated human lactoferrin (LF). The CSF and LF preparations did not contain detectable endotoxin (less than 0.1 ng). Mice pretreated with LF were more sensitive to the effects of CSF. In mice pretreated with LF, 2,000 U IL-3 or 20,000 U CSF-1 significantly enhanced the cycling status and absolute numbers of all progenitors, whereas 20,000 U GM-CSF significantly increased the cycling status of CFU-GM and CFU-GEMM, but had no effect on cycling of BFU-E or on numbers of any of the progenitors. The effects of CSF in mice pretreated with LF were not mimicked by 0.1-100 ng E. coli lipopolysaccharide.

The role of the colony-stimulating factors in resistance to acute infections

A set of specific glycoproteins, the colony-stimulating factors, has been identified as regulating granulocyte and macrophage production and function. These colony-stimulating factors have now been purified and mass produced by recombinant technology. These versatile regulators are capable of providing the body both with an ultrarapid and sustained system for responding to infections. The granulocytes, macrophages and eosinophils involved in these responses appear likely to be key cell populations ensuring adequate resistance to acute infections and the colony-stimulating factors may prove to be valuable agents in the clinic for increasing resistance to life-threatening infections particularly in immunologically compromised patients.

Purified colony stimulating factors (G-CSF and GM-CSF) induce differentiation in human HL60 leukemic cells with suppression of clonogenicity

Purified recombinant human granulocyte-macrophage colony-stimulating factor (rHGM-CSF) and purified native murine granulocyte-CSF (G-CSF) both induced differentiation in HL60 cells as evidenced by expression of granulocyte and macrophage membrane antigens, although this was not accompanied by morphological evidence of differentiation. Both types of CSF suppressed clonogenic HL60 cells with evidence of complete clonal extinction. The suppression of clonogenic HL60 cells was preceded in some experiments by CSF-stimulated proliferation of HL60 cells, and this was most evident in cultures containing low concentrations of fetal calf serum (FCS).

Regulation of hematopoiesis by T lymphocytes and natural killer cells

T lymphocytes and natural killer (NK) cells exert both stimulatory and suppressive effects that regulate growth and differentiation of hematopoietic cells. Activated T and NK cells have been demonstrated in different pathological states of bone marrow failure and are proposed to play a role in the pathogenesis of the disease. T and NK cells have also been shown to be responsible for bone marrow graft rejection in both allogeneic and syngeneic donor/recipient combinations. Lymphocytes can regulate hematopoietic cell growth by direct cellular contact or by releasing soluble factors, such as colony-stimulating factors, immune interferon, lymphotoxin, and tumor necrosis factor, active on hematopoietic precursor cells.

Granulocyte colony-stimulating factor and differentiation-induction in myeloid leukemic cells

The granulocyte colony-stimulating factor (G-CSF) belongs to a family of hemopoietic growth factors regulating the production of granulocytes and macrophages. Murine G-CSF stimulates the proliferation and differentiation of precursors of neutrophilic granulocytes and is also able to stimulate the functional activities of mature neutrophils. Among the hemopoietic growth factors, G-CSF has an outstanding capacity to induce terminal differentiation and suppression of self-renewal in myeloid leukemic cells. Murine and human G-CSF's show complete biological cross-reactivity across species and bind equally well to G-CSF receptors of either species. Specific receptors for G-CSF exist on all normal neutrophilic cells and have not been lost in the generation of primary human myeloid leukemias. This data indicates that G-CSF may be a useful reagent in the treatment of myeloid leukemia, in hemopoietic regeneration and in increasing resistance against infections.

Biomolecule-cell interactions and the regulation of myelopoiesis

The regulation of myelopoiesis in vivo most likely entails a complex set of interactions between cell-derived biomolecules and their target cells. Much of what we currently know of these interactions has been derived from studies in vitro utilizing techniques for the purification of both the biomolecules and the cells producing and responding to these factors. Stimulating and suppressing influences have been uncovered, and with the cloning and purification of biologically active factors, studies assessing the actions of these molecules in vivo have begun. From studies in vitro it is apparent that many of the purified molecules can have move than one action and that different molecules can collaborate in a synergistic manner to enhance or suppress functional endpoints.

The role of CFU-GEMM in human hemopoiesis

The assay for CFU-GEMM has provided a measurement for pluripotent hemopoietic precursors in normal and abnormal hemopoiesis. While these cells are able to express the functional repertoire that includes not only myelopoiesis but also lymphopoiesis attempts to determine their self-renewal have shown little or no self-renewal capability. It is currently not known whether this observation reflects culture conditions favouring differentiation processes and suppressing self-renewal, or whether the observation made in culture truly reflects the potential of cells in vivo. Recent advances in molecular biology have lead to the identification of the genomic sequences of at least one of the hemopoietic growth factors thus confirming their importance as regulators.

Tumor necrosis factor and lymphotoxin induce differentiation of human myeloid cell lines in synergy with immune interferon

We show that the cytotoxins tumor necrosis factor (TNF) or lymphotoxin (LT), at concentrations of approximately 10(-11) M induce monocytic differentiation of human myeloid cell lines. After 5 d of culture in the presence of rTNF and LT, a significant proportion of the myeloid cell lines express monocyte differentiation antigens and ANAE activity, and become able to reduce nitroblue tetrazolium (NBT) and mediate low levels of ADCC against tumor target cells. These markers of differentiation, however, are maximally induced when rIFN-gamma, at concentrations as low as 4 U/ml, is present simultaneously with the cytotoxins, and the two classes of cytokines act synergistically to induce terminal differentiation. The appearance of monocytic antigens is accompanied by acquisition of morphology and other functional properties of mature monocytic cells, such as chemiluminescence and phagocytosis, and by expression of FcR for monomeric IgG. A decrease in cell proliferation accompanies induced differentiation, and is not due to the cytotoxic properties of TNF or LT, as indicated in simultaneous analysis of surface phenotype and cell cycle. The lack of cytotoxicity of TNF on the HL-60 cell line is also demonstrated by the enhancing effect of TNF on HL-60 cell growth and nucleoside uptake in the first 2 d of culture. These data show that the cytotoxins TNF and LT mediate complex effects on cells of the myelomonocytic lineage and, in synergy with IFN-gamma, can fully induce immature myeloid cells to differentiate into cells with phenotypic, functional, and proliferative characteristics of terminally differentiated myelomonocytic cells.

Recombinant human granulocyte colony stimulating factor: molecular and biological characterization

Human or rodent bone marrow treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) in a CFU-GM assay yield predominantly granulocytic colonies. The specificity for granulocyte progenitors in vitro is also demonstrated in vivo by a five- to six-fold elevation in hamster peripheral blood neutrophils. Other cell types (monocytes, lymphocytes and eosinophils) remain stable. Analysis of mRNA from the bladder carcinoma cell line 5637 (1A6) shows the predominant species of mRNA codes for a mature protein of 174 amino acids. A small fraction of the mRNA can code for an alternative form of hG-CSF containing additional three amino acids between positions 35 and 36.

Biological and biochemical characteristics of the basophil-like cell promoting activity (BaPA) and a human IL 3-like activity

Two growth factors isolated from lectin-stimulated human mononuclear cells stimulate the long-term growth of metachromatically staining cells in human bone marrow cultures. One factor, termed basophil-like cell promoting activity, induces also differentiation of cells which morphologically and functionally resemble human basophils. A second factor, which in contrast to BaPA stimulates murine IL3-dependent cells, induces the growth of human metachromatically staining cells of an immature morphology with certain resemblance to mast cell-like cells. BaPA inhibits the growth of HL-60 cells, while IL3-like activity stimulates the growth of HL-60 cells. BaPA does not share biochemical similarities to other well-defined human growth factors, while the IL3-like activity has strong resemblance to pluripotential hemopoietic CSF.

Human pluripotent hemopoietic colony stimulating factor: activities on human and murine cells

Human pluripotent colony stimulating factor (Pluripoietin) was shown to act synergistically with human pluripotent alpha-like colony-stimulating activity (Pluripoietin-alpha) supporting the proliferation and differentiation of human CFU-GM progenitor cells in vitro, increasing colony size and numbers. In addition, Pluripoietin enhanced cytotoxic activity of mature human neutrophil granulocytes in an antibody-dependent cellular cytotoxicity assay. Biological activities of Pluripoietin known so far suggest great potentials for clinical use. Preclinical in vivo studies of Pluripoietin in different disease situations may be feasible in mice, because Pluripoietin is active on granulocyte precursors and on a variety of other murine cells.

Serum basophil-stimulating activity in the guinea-pig during induction of basophilic responses to ovalbumin and tick feeding

We have described functional and biochemical characteristics of a distinct T-cell dependent guinea-pig basophil-stimulating factor (BSF), measured using a sensitive 7-day bone marrow culture assay, standardized with high-activity BSF present in serum-free splenic cell-conditioned medium (CM). In the present studies, the in vivo relevance of BSF was explored during protocols of induction of peripheral blood or tissue basophil responses to ovalbumin (OA) injection or Amblyomma americanum tick feeding. Pooled immune serum, taken from OA-injected inbred or outbred animals during induction of blood and marrow basophilia, contained an in vitro inhibitor to BSF at high concentrations and BSF-like activity at low concentrations; maximal stimulation of histamine synthesis by bone marrow cells in vitro was found in the presence of Day 4 OA-immune serum. In vivo studies in the OA model demonstrated maximal serum BSF-like activity at 48-72 hr before peak bone marrow basophil response, followed by a levelling off to 50% of maximum at 2 weeks. In the tick model, serum BSF-like activity was present in Day 8, but not Day 1, post-primary infection and was maximal at Day 3 post-secondary infection; post-primary Day 1 serum was inhibitory to basophil growth in vitro. These observations suggest that BSF regulates the appearance of basophils in response to antigen in vivo by an effect on basophil progenitors. The observations stress the potential application of guinea-pig models to understanding the regulation of basophil production in allergic disorders.

Human embryonic hemopoiesis. Kinetics of progenitors and precursors underlying the yolk sac----liver transition

Human embryonic development involves transition from yolk sac (YS) to liver (L) hemopoiesis. We report the identification of pluripotent, erythroid, and granulo-macrophage progenitors in YS, L, and blood from human embryos. Furthermore, comprehensive studies are presented on the number of hemopoietic progenitors and precursors, as well as of other cell types, in YS, L, and blood at precisely sequential stages in embryos and early fetuses (i.e., at 4.5-8 wk and 9-10 wk postconception, respectively). Our results provide circumstantial support to a monoclonal hypothesis for human embryonic hemopoiesis, based on migration of stem and early progenitor cells from a generation site (YS) to a colonization site (L) via circulating blood. The YS----L transition is associated with development of the differentiation program in proliferating stem cells: their erythroid progeny shows, therefore, parallel switches of multiple parameters, e.g., morphology (megaloblasts----macrocytes) and globin expression (zeta----alpha, epsilon----gamma).

Cloning and expression of the rat interleukin-3 gene

Genomic clones carrying the rat interleukin-3 (IL-3) gene have been isolated and the nucleotide sequence of the gene determined. Alignment of this sequence with that of the mouse IL-3 gene has allowed the structure of the rat IL-3 gene to be deduced. The intron-exon boundaries are conserved and extensive nucleotide homology (approx 90%) is present in the 5' flanking region and the portion of the gene coding for the signal peptide. Several proposed regulatory sequences are conserved and an analogous element to the tandem repeat in intron 2 of the mouse gene is also present. The predicted amino acid sequence for mature rat IL-3 shows surprisingly low homology (54%) with its murine counterpart, although all four cysteine residues are conserved. The rat IL-3 gene was expressed in monkey COS-1 cells and colony assays established that rat IL-3 is a multi-lineage haemopoietic growth regulator. There was little cross-reactivity of the respective IL-3 species on mouse and rat bone marrow cells suggesting that rat IL-3, in concert with its receptor, has evolved significantly away from the mouse IL-3/receptor system.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Pluripoietin alpha: a second human hematopoietic colony-stimulating factor produced by the human bladder carcinoma cell line 5637

We have identified a factor constitutively produced by the human bladder carcinoma cell line 5637, which has the following capacities: to induce the differentiation of the human promyelocytic leukemic cell line HL-60; to induce the expression of chemotactic peptide receptors in leukemic cells as well as in normal peripheral blood granulocytes; to function as a chemoattractant for neutrophils as well as, under certain conditions, inhibiting their migration; to support the growth of eosinophil and granulocyte/macrophage progenitors, which is maximal when scored at day 14; and to support the growth of human mixed pluripotent progenitors and erythroid bursts from normal human bone marrow. This factor has a molecular size of 32 kDa by gel filtration and 16.5 kDa by NaDodSO4/PAGE. We have termed this factor pluripoietin alpha.

Multilineage, non-species specific hematopoietic growth factor(s) elaborated by a feline fibroblast cell line: enhancement by virus infection

In studies designed to determine the role of feline leukemia virus (FeLV) in the pathogenesis of marrow failure in the cat, we tested medium conditioned by uninfected and FeLV-infected feline embryonic fibroblasts (FEA) for its effect on hematopoietic colony growth in culture. As opposed to an inhibitory effect, we found that the conditioned medium (CM) from FEA or FEA/FeLV increased the in vitro growth of multiple hematopoietic progenitor cell types including erythroid burst-forming cells (BFU-E), granulocyte/macrophage colony-forming cells, megakaryocytic colony-forming cells, and mixed-cell colony-forming cells. Furthermore, CM enhanced the growth of progenitors in cultures of mouse or human marrow cells, as well as cat marrow cells. Stimulation of feline BFU-E was most marked with an increment in growth of 400% over control. The human burst promoting activity (BPA) of the CM was equivalent or better than other CM available in our laboratory. The evidence suggest that the growth-promoting activity is a constitutive product(s) released by FEA which was enhanced eightfold with virus infection. Studies with non-adherent and T-lymphocyte-depleted human marrow cells and human peripheral blood cells suggest that the growth factor(s) acts directly on progenitor cells and not through readily identified accessory cells. These findings are consistent with the concept that mesenchymal cells such as fibroblasts have the capacity to release hematopoietic growth factor(s) capable of acting on primitive hematopoietic progenitors. The results provide an example of how injury of such cells, through virus infection, may enhance growth factor(s) release and influence the hematopoietic microenvironment.