Human Colony-stimulating Factor Research Articles

Myeloid Differentiation of Purified CD34+ Cells After Stimulation With Recombinant Human Granulocyte-Monocyte Colony-Stimulating Factor (CSF), Granulocyte-CSF, Monocyte-CSF, and Interleukin-3

CD34+ cells isolated from bone marrow or umbilical cord blood from healthy donors were studied for proliferation and differentiation in liquid cultures in the presence of recombinant human granulocyte-monocyte colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF), monocyte CSF (M-CSF), and interleukin-3 (IL-3), followed by immunophenotyping for myeloid and myeloid-associated cell surface markers. IL-3, either alone or together with GM-CSF, G-CSF, or M-CSF, induced, on average, 50-fold cell multiplication, GM-CSF five fold to 10-fold, and G-CSF and M-CSF less than fivefold. Cells from cultures stimulated with GM-CSF, G-CSF, or M-CSF alone contained cells with a "broad" myeloid profile, "broader" than observed in cultures with IL-3. However, since IL-3 induced rapid cell multiplication, high numbers of cells expressing early (CD13, CD33) and late myeloid markers (CD14, CD15) were recovered. The presence of other CSFs together with IL-3 did not alter the IL-3-induced effect on the cells. When 5,000 CD34+ cells were cultured with IL-3 alone, the cultures still contained 2,000 to 5,000 CD34+ cells after 14 days of culture, while cells cultured with GM-CSF, G-CSF, or M-CSF contained less than 1,000 CD34+ cells. Furthermore, 1,000 to 3,000 cells were positive for the megakaryocytic lineage marker CD41b after cultures with GM-CSF or IL-3, while cultures with G-CSF or M-CSF did not contain detectable numbers of CD41b+ cells. Finally, erythroid cells could also be generated from purified CD34+ cells. The results show that IL-3 and GM-CSF can induce rapid proliferation of purified CD34+ cells in vitro with differentiation to multiple myeloid lineages, while certain subsets maintain expression of CD34.

Modulation of Neonatal Myelopoiesis in Newborn Rats after 7 Days' Administration of Either Granulocyte-Monocyte Colony Stimulating Factor or Interleukin-3

Single-pulse administration of either recombinant human granulocyte-monocyte colony stimulating factor or recombinant human granulocyte colony stimulating factor to newborn rats has previously been demonstrated to increase the peripheral neutrophil count and modulate bone marrow (BM) neutrophil pools. In our present study, we investigated the effects of 7 d of either recombinant murine granulocyte-monocyte colony stimulating factor (rmGM-CSF) (75 micrograms/kg/d) or recombinant murine IL-3 (rm IL-3) (10 micrograms/kg/d) on newborn rat myelopoiesis. Sprague Dawley newborn rats (greater than or equal to 24 h) were injected (intraperitoneally) daily for 7 d with either rmGM-CSF, rmIL-3, or PBS/BSA. rmGM-CSF induced a significant increase in the peripheral neutrophil count on d 3 (p less than 0.03) and d 7 (p less than 0.001) (75% increase). Additionally, rmGM-CSF induced a 50% increase in the BM neutrophil storage pool (p less than 0.025). rmIL-3 increased the BM colony forming unit-granulocyte monocyte pool (p less than 0.001); however, it failed to increase the peripheral neutrophil count or BM neutrophil storage pool. Neither CSF increased the BM neutrophil proliferative pool or BM colony forming unit-granulocyte monocyte proliferative rate. Additionally, 7 d of rmGM-CSF with or without antibiotics did not synergistically alter the mortality rate after group B streptococcol inoculation. This study suggests that rmIL-3 appears to stimulate more neonatal myeloid committed progenitor cell activity compared with rmGM-CSF. Optimal modulation of neonatal myelopoiesis may require the use of a sequential combination of hematopoietic CSF, namely an early-acting CSF followed by a more lineage myeloid-specific CSF.

Purification of human megakaryocyte colony-stimulating factor (Meg-CSF) from urine of aplastic anemia patients

Our laboratory has already documented that extracts of urine from aplastic anemia patients stimulate megakaryocyte and platelet production in vivo in rats and mice. This stimulatory activity was apparently mediated by a unique cytokine. This report describes the purification of the factor likely responsible for this activity because it stimulates megakaryocyte colony formation (CFU-meg) in vitro. The factor, when purified to homogeneity, exhibits a molecular weight of 55,000–57,000 and an isoelectric point of 7.2–7.4. Under physiological conditions, ultrafiltration experiments indicate that human megakaryocyte colony-stimulating factor (hMeg-CSF) exists as a monomer or dimer. In contrast to human urinary erythropoietin (Epo), only a small amount of hMeg-CSF forms complexes of high molecular weight aggregates. In contrast to interleukin (IL)-3, hMeg-CSF induces small colonies in vitro containing three to five megakaryoblasts. Even at concentrations 100-fold greater than the threshold amount required to stimulate CFU-meg colony formation, hMeg-CSF stimulated only CFU-meg colonies, but did not stimulate myeloid or erythroid lineage colonies. We propose that this purified factor is specific for the megakaryocyte lineage, and that it be termed human Meg-CSF.

Peptide Antisera to Human Colony-Stimulating Factor 1 Receptor Detect Ligand-Induced Conformational Changes and a Binding Site for Phosphatidylinositol 3-Kinase

A peptide antiserum (anti-A) directed to the intracellular, juxtamembrane region (residues 552 to 574) of the human colony-stimulating factor 1 receptor (CSF-1R) precipitated only ligand-activated, native receptors from solution but bound to unstimulated forms after their denaturation. Two peptide antisera (anti-KI1 and -KI2), directed to residues 679 to 700 and 701 to 721, respectively, in the CSF-1R kinase insert (KI) domain and including mapped sites of ligand-induced phosphorylation at Tyr-699 and Tyr-708, bound at least 80% of the receptor molecules expressed in either CSF-1-stimulated or unstimulated cells. Immune complexes formed with anti-KI1, anti-A, or a peptide antiserum to the CSF-1R carboxyl terminus (anti-C-ter) coprecipitated CSF-1R complexed to a phosphatidylinositol 3-kinase (PtdIns 3-K) from CSF-1-stimulated cells, whereas anti-KI2 serum did not. In an in vitro assay, binding of CSF-1R to PtdIns 3-K required receptor tyrosine phosphorylation but not CSF-1R-mediated phosphorylation of the lipid kinase, and the association was specifically blocked by anti-KI2 or antibodies to phosphotyrosine. Neither anti-KI1, anti-A, nor anti-C-ter serum inhibited binding. We conclude that (i) only a minority of ligand-activated receptors form a stable complex with PtdIns 3-K in vivo, (ii) efficient binding of the lipid kinase requires receptor tyrosine phosphorylation within the CSF-1R KI domain, and (iii) a region within the KI domain defined by residues 701 to 721 at least partially overlaps the PtdIns 3-K binding site.

Peptide antisera to human colony-stimulating factor 1 receptor detect ligand-induced conformational changes and a binding site for phosphatidylinositol 3-kinase.

A peptide antiserum (anti-A) directed to the intracellular, juxtamembrane region (residues 552 to 574) of the human colony-stimulating factor 1 receptor (CSF-1R) precipitated only ligand-activated, native receptors from solution but bound to unstimulated forms after their denaturation. Two peptide antisera (anti-KI1 and -KI2), directed to residues 679 to 700 and 701 to 721, respectively, in the CSF-1R kinase insert (KI) domain and including mapped sites of ligand-induced phosphorylation at Tyr-699 and Tyr-708, bound at least 80% of the receptor molecules expressed in either CSF-1-stimulated or unstimulated cells. Immune complexes formed with anti-KI1, anti-A, or a peptide antiserum to the CSF-1R carboxyl terminus (anti-C-ter) coprecipitated CSF-1R complexed to a phosphatidylinositol 3-kinase (PtdIns 3-K) from CSF-1-stimulated cells, whereas anti-KI2 serum did not. In an in vitro assay, binding of CSF-1R to PtdIns 3-K required receptor tyrosine phosphorylation but not CSF-1R-mediated phosphorylation of the lipid kinase, and the association was specifically blocked by anti-KI2 or antibodies to phosphotyrosine. Neither anti-KI1, anti-A, nor anti-C-ter serum inhibited binding. We conclude that (i) only a minority of ligand-activated receptors form a stable complex with PtdIns 3-K in vivo, (ii) efficient binding of the lipid kinase requires receptor tyrosine phosphorylation within the CSF-1R KI domain, and (iii) a region within the KI domain defined by residues 701 to 721 at least partially overlaps the PtdIns 3-K binding site.

Preclinical studies on the efficacy of CSFs in dogs and subhuman primates

Hemopoiesis-stimulating activity of various recombinant human colony-stimulating factors (rhCSFs) has been studied in four different preclinical animal models. The CSFs used were erythropoietin (Epo), granulocyte-macrophage (GM) CSF, granulocyte (G) CSF, interleukin (IL) 3, IL-1β, and mast cell growth factor (MGF) or stem cell factor (SCF). Emphasis was placed on effects induced by combination treatment with varied pairs of the factors. Dogs and primates were chosen because of evidence of efficacy from earlier studies with the single recombinant human factors alone. The animal models chosen were: 1) isovolemic hemodilution to a hematocrit of 10% (or 20%) of dogs, splenectomized at least three months before start of the study. Additionally, the animals had been primed with Epo (or Epo plus IL-3) on three days daily or five days every other day before hemodilution. 2) Total body irradiation (TBI) of dogs (2.4 Gy) followed by daily treatment with IL-1β (d1-7) plus Epo administered daily over three weeks. 3) TBI of rhesus monkeys (4.5 Gy) and daily treatment with IL-3 and GM-CSF over three weeks. 4) Treatment of healthy normal cynomolgus monkeys with various factor combinations over about two or three weeks. The results can be summarized as follows: 1) Priming with Epo before blood loss (withdrawal) allows a strikingly enhanced recovery of hematocrit and other hematological parameters. Further evaluation of the role of concomitantly applied CSFs (e.g., IL-3, GM-CSF or G-CSF) on the restoration of immune functions would be desirable. 2) Single CSFs and preferentially factor combinations are valuable agents to reduce irradiation injury and to enhance recovery from bone marrow hypoplasia. 3) Treatment of healthy animals with selected CSF combinations results in a stronger hemopoietic stimulation than with single factors alone. Some particular combinations even stimulate platelet production, e.g., IL-3/GM-CSF, GM-CSF/Epo or G-CSF/IL-3. The results obtained indicate that stimulatory responses of hemopoiesis in normal animals cannot always be compared with the effects seen in compromised animals. It is assumed that the preclinical data obtained in compromised animals may perhaps more realistically reflect what is eventually to be expected in future clinical studies.

Treatment of myelodysplastic syndromes with human granulocytic-macrophage colony-stimulating factor (GM-CSF) or GM-CSF combined with low dose (ARA-C)

Treatment of myelodysplastic syndromes with human granulocytic-macrophage colony-stimulating factor (GM-CSF) or GM-CSF combined with low dose (ARA-C)

The Potential Role of Recombinant Hematopoietic Colony-Stimulating Factors in Preventing Infections in the Immunocompromised Host

Hematopoietic colony-stimulating factors coordinate the proliferation and maturation of bone marrow and peripheral blood cells during normal hematopoiesis. Most of these factors are now available as recombinant human colony-stimulating factors, and preclinical and clinical testing is proceeding rapidly. Granulocyte and granulocyte/macrophage colony-stimulating factors have been the most extensively studied to date. In human clinical trials, granulocyte colony-stimulating factor improves neutrophil counts and function, reduces episodes of febrile neutropenia, improves neutrophil recovery after disease- or treatment-induced myelosuppression, and reduces the number of serious infections in several neutropenic disease states. Granulocyte/macrophage colony-stimulating factor has similar biological properties but may also improve eosinophil proliferation and function, and platelet cell recovery after myelotoxic bone marrow injury, Interleukin-1 boosts the effects of granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor, but also may promote the resolution of established infections in conjunction with antibiotics. The therapeutic realities and future therapeutic implications of these agents for the therapy of infections, cancer and hemopoietic disorders are discussed.

Sequential studies on the role of mitoxantrone, high-dose cytarabine, and recombinant human granulocyte-macrophage colony-stimulating factor in the treatment of refractory non-Hodgkin's lymphoma.

Mitoxantrone (Novantrone, American Cyanamid Company; NO) and high-dose cytarabine (Ara-C; AC) have each been shown to be active in non-Hodgkin's lymphomas (NHL) in various studies. The studies reported here are sequential. The first study (NOAC I) combined high-dose cytarabine (3 g/m2/12 h as a 3 h infusion on day 1) with mitoxantrone (10 mg/m2/d on days 2 and 3). Of 31 patients with relapsed and refractory NHL, 7 achieved complete remission (CR) and 7, partial remission (PR). Myelosuppression was the major toxicity of this regimen. In the second study (NOAC II), the dosage of cytarabine was escalated to 3 g/m2/12 h on days 1 and 2 (4 doses) while mitoxantrone remained 10 mg/m2/d on days 2 and 3. The effects of recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF) were simultaneously studied. Twenty-three patients from five centers were treated with NOAC plus rhGM-CSF while 14 patients from four centers received NOAC II alone. A CR was achieved in 9 of 23 patients who received the additional rhGM-CSF and in 2 of 14 patients treated with NOAC alone. With rhGM-CSF, the median duration of severe neutropenia (less than 0.5/nL) after chemotherapy was 8 days versus a median of 13 days without rhGM-CSF, while the duration of severe thrombocytopenia (less than 20/nL) was not significantly different. The rates of infection and mucositis were 25% and 17%, respectively, with rhGM-CSF compared to 53% and 60% without rhGM-CSF. Thus, this last nonrandomized pilot study indicates that administration of rhGM-CSF reduces the duration of chemotherapy-induced cytopenia and the rate of mucositis. This growth factor does not appear to result in stimulation of lymphoma cells. At present, a controlled randomized trial is being conducted using NOAC II with rhGM-CSF or placebo to establish the definitive role of this growth factor in the treatment of NHL.

Exploiting the cell membrane for the production of heterologous proteins in Escherichia coli.

The bacterial membrane serves both as a cell organelle and as a barrier for segregating the metabolically active cytoplasm from the extracellular milieu. Thus we can use plasmid vectors designed to produce a hybrid protein containing an efficient signal peptide coupled to the amino terminus of the cloned heterologous protein (secretion cloning vectors) for the production of proteins which are insoluble, proteolytically sensitive, or bacteriocidal when produced in the cytoplasm of Escherichia coli. We demonstrate that human granulocyte-macrophage colony stimulating factor can be isolated as an active species only after transport into the bacterial periplasm. Production of the protein in the bacterial cytoplasm is bacteriocidal. We also demonstrate that biologically active human interleukin 4 appears only after transport of the protein into the bacterial growth medium. The protein forms membrane-associated aggregates in the cytoplasm, and demonstrates an active but nonnative conformation when expressed in the periplasm. This may correlate with the affinity of the interleukin 4 molecule for negatively charged macromolecules, including bacterial membrane components and bacterial lipopolysaccharides, which may alter the folding pathway inside the cell.

Differential effects of recombinant human colony stimulating factor (rh G‐CSF) on stem cells in marrow, spleen and peripheral blood in mice

Previously it has been hypothesized that the granulopoietic and erythropoietic lineages may compete for differentiating stem cells. According to this hypothesis one would expect that a stimulation of granulopoiesis by G-CSF administration would lead to a reduction of the stem cell pool and be followed by a decline of erythropoietic progenitor numbers. In addition one would expect an enhanced response of granulopoiesis if G-CSF administration were combined with suppression of erythropoiesis by red cell transfusion. To evaluate whether this hypothesis holds true C57bl mice were injected subcutaneously for 6 d with 3.75 micrograms rh G-CSF/mouse/d (150 micrograms G-CSF/kg body weight/d). Marrow CFU-S numbers showed an increase to 160% on day 2, followed by a decrease to 50% of control on day 6. Splenic and peripheral blood CFU-S increased 20-fold and 10-fold, respectively. Marrow CFU-E declined to 40% of the control value. Splenic CFU-E increased 10-fold. The increase in marrow CFU-GM numbers ranged between 140% and 180%. CFU-GM obtained from the spleen and the peripheral blood increased 60-fold and 15-fold, respectively. Regarding the CFU-S and CFU-GM a similar pattern of response was found in an experiment where rh G-CSF administration was combined with an additional red cell transfusion. These data do not provide convincing evidence for an exhaustion of haemopoietic stem cells during treatment with G-CSF. They rather suggest that an important side effect of G-CSF treatment is a release of CFU-S and progenitors from the marrow to the peripheral blood and a reseeding in the spleen.

Effect of Granulocyte Colony-Stimulating Factor after Intensive Induction Therapy in Relapsed or Refractory Acute Leukemia

Background. Although colony-stimulating factors have been shown to accelerate recovery from severe neutropenia after intensive chemotherapy or bone marrow transplantation, their use in acute leukemia has been controversial because in vitro they stimulate leukemic colonies as well as normal granulocyte colonies. Methods. We conducted a prospective, randomized, controlled study to determine the safety and efficacy of recombinant human granulocyte colony-stimulating factor (CSF) after a standard course of intensive therapy in 108 patients with relapsed or refractory acute leukemia (67 with acute myelogenous leukemia, 30 with acute lymphocytic leukemia, 9 in blast crisis from chronic myelogenous leukemia, and 2 with acute leukemia arising from myelodysplastic syndromes). Treatment with granulocyte CSF (200 micrograms per square meter of body-surface area per day in a 30-minute infusion) was begun two days after the end of the chemotherapy and continued until the neutrophil count rose above 1500 per cubic millimeter. Results. Treatment with granulocyte CSF accelerated the recovery of neutrophils significantly (P less than 0.01), shortening it by about a week, but it had no effect on platelet recovery. Although the incidence of febrile episodes was almost the same, documented infections were significantly less frequent in the group treated with granulocyte CSF (P = 0.028). There was no evidence that granulocyte CSF accelerated the regrowth of leukemic cells. Fifty percent of 48 patients in the CSF group who could be evaluated and 36 percent of 50 controls had complete remission. The rate of relapse was almost the same in the two groups. Conclusions. It appears that recombinant human granulocyte CSF is safe in acute leukemia, accelerating neutrophil recovery and thereby reducing the incidence of documented infection without affecting the regrowth of leukemic cells. It should be used with caution, however, pending further confirmation of these early results.

A point mutation at tyrosine-809 in the human colony-stimulating factor 1 receptor impairs mitogenesis without abrogating tyrosine kinase activity, association with phosphatidylinositol 3-kinase, or induction of c-fos and junB genes.

Substitution of phenylalanine for tyrosine-809 in the human colony-stimulating factor 1 receptor (CSF-1R) inhibited its ability to transduce ligand-dependent mitogenic signals in mouse NIH 3T3 cells. When combined with an "activating" mutation at codon 301 that induces constitutive CSF-1R tyrosine kinase activity, the codon 809 mutation suppressed ligand-independent cell transformation. Comparative mapping of tryptic phosphopeptides from mutant and wild-type CSF-1R indicated that tyrosine-809 is a site of ligand-dependent receptor phosphorylation in vivo. The mutant receptor was active as a tyrosine kinase in vitro and in vivo, underwent CSF-1-dependent association with a phosphatidylinositol 3-kinase, and induced expression of the protooncogenes c-fos and junB, underscoring its ability to trigger some of the known cellular responses to CSF-1. The mutant receptor is likely to be impaired in its ability to interact with critical cellular effectors whose activity is required for mitogenesis.

Hemogram Changes in Lactating Dairy Cows Given Human Recombinant Granulocyte Colony Stimulating Factor (r-MethuG-CSF)

As a prelude to mammary gland challenge experiments, this investigation was implemented to assess the hematologic changes in lactating dairy cattle induced by two dosage regimes of human recombinant colony stimulating factor (Hr-GCSF). This study documents the capability of the human recombinant colony stimulating factor to produce hematologic changes in both a time and dose dependent manner when administered to the adult lactating bovine. A screening dose of 1 microgram/kg of Hr-GCSF administered to three study subjects produced a three- to four-fold increase in peripheral blood mature neutrophil counts (P less than 0.043) by day 12 of the trial. The priming dose treatment group of four lactating cows (3 micrograms/kg of Hr-GCSF) exhibited a three- to five-fold increase in peripheral blood mature neutrophil counts (P less than 0.05) and two- to three-fold increases in white blood cell counts by day 5 of the trial. Hematologic examinations of the control group (n = 4; no Hr-GCSF administration) did not detect significant changes in their neutrophil counts over baseline values. The milk somatic cell counts did not statistically shift over baseline values in any of the control or Hr-GCSF treatment groups. When attempting to alter the course of infectious disease processes, potential applications of colony stimulating factors provide interesting speculations about new therapeutic modalities.

Abnormal Responses of Myeloid Progenitor Cells to Recombinant Human Colony-Stimulating Factors in Congenital Neutropenia

The effects of recombinant human interleukin-3 (IL-3) and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) in semisolid agar culture were studied in two patients with Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from patients was significantly reduced in response to various concentrations of either IL-3 or G-CSF alone, compared with that from normal subjects. There was no inhibitory effect of bone marrow cells from patients on normal CFU-C formation supported by IL-3 or G-CSF. However, the simultaneous stimulation with IL-3 and G-CSF induced the increase of CFU-C formation in patients with congenital neutropenia. Furthermore, CFU-C growth in both patients was supported when bone marrow cells were preincubated with IL-3 in liquid culture followed by the stimulation with G-CSF in semisolid agar culture. In contrast, that was not supported by the preincubation with G-CSF and the subsequent stimulation with IL-3. This evidence suggests that the hematopoietic progenitor cells in patients with congenital neutropenia have the potential for developing CFU-C in the combined stimulation with IL-3 and G-CSF, and that this growth may be dependent on the priming of IL-3 followed by the stimulation with G-CSF. The level of mature neutrophils in peripheral blood was not fully restored to normal levels by the daily administration of G-CSF in doses of 100 to 200 micrograms/m2 of body surface area for 20 to 25 days in both patients. These observations raise the possibility that the combination of IL-3 and G-CSF might have a potential role for the increase of neutrophil counts in patients with congenital neutropenia.

Abnormal responses of myeloid progenitor cells to recombinant human colony-stimulating factors in congenital neutropenia

The effects of recombinant human interleukin-3 (IL-3) and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) in semisolid agar culture were studied in two patients with Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from patients was significantly reduced in response to various concentrations of either IL-3 or G-CSF alone, compared with that from normal subjects. There was no inhibitory effect of bone marrow cells from patients on normal CFU-C formation supported by IL-3 or G-CSF. However, the simultaneous stimulation with IL-3 and G- CSF induced the increase of CFU-C formation in patients with congenital neutropenia. Furthermore, CFU-C growth in both patients was supported when bone marrow cells were preincubated with IL-3 in liquid culture followed by the stimulation with G-CSF in semisolid agar culture. In contrast, that was not supported by the preincubation with G-CSF and the subsequent stimulation with IL-3. This evidence suggests that the hematopoietic progenitor cells in patients with congenital neutropenia have the potential for developing CFU-C in the combined stimulation with IL-3 and G-CSF, and that this growth may be dependent on the priming of IL-3 followed by the stimulation with G-CSF. The level of mature neutrophils in peripheral blood was not fully restored to normal levels by the daily administration of G-CSF in doses of 100 to 200 micrograms/m2 of body surface area for 20 to 25 days in both patients. These observations raise the possibility that the combination of IL-3 and G-CSF might have a potential role for the increase of neutrophil counts in patients with congenital neutropenia.

Human Colony-Stimulating Factor 1 (CSF-1) Receptor Confers CSF-1 Responsiveness to Interleukin-3-Dependent 32DCL3 Mouse Myeloid Cells and Abrogates Differentiation in Response to Granulocyte CSF

Interleukin-3 (IL-3)-dependent mouse myeloid 32DC13 cells differentiate to neutrophils in response to granulocyte colony-stimulating factor (G-CSF). Introduction of the human c-fms gene, which encodes the receptor for CSF-1, into 32DC13 cells gave rise to variants that were able to proliferate in medium containing either murine IL-3 or human recombinant CSF-1, but were unable to differentiate to granulocytes in response to G-CSF. Unlike parental 32CD13 cells, CSF-1-responsive derivatives expressed nonspecific esterase when grown in CSF-1, but did not exhibit many other morphologic, immunologic, or functional properties of mononuclear phagocyte differentiation, or express murine CSF-1 receptors. Accelerated turnover of the human CSF-1 receptor was observed in response to CSF-1 and phorbol esters, but not after stimulation with IL-3 or bacterial lipopolysaccharide. Although both CSF-1 and IL-3 induced tyrosine phosphorylation of heterologous substrates in the dually responsive cells, differences in the patterns of substrate phosphorylation were observed in response to the two hematopoietins. We conclude that expression of the human CSF-1 receptor in 32DC13 cells not only induces CSF-1 responsiveness, but alters its phenotype in a way that prohibits granulocyte differentiation.

Human colony-stimulating factor 1 (CSF-1) receptor confers CSF-1 responsiveness to interleukin-3-dependent 32DC13 mouse myeloid cells and abrogates differentiation in response to granulocyte CSF

Interleukin-3 (IL-3)-dependent mouse myeloid 32DC13 cells differentiate to neutrophils in response to granulocyte colony-stimulating factor (G- CSF). Introduction of the human c-fms gene, which encodes the receptor for CSF-1, into 32DC13 cells gave rise to variants that were able to proliferate in medium containing either murine IL-3 or human recombinant CSF-1, but were unable to differentiate to granulocytes in response to G-CSF. Unlike parental 32CD13 cells, CSF-1-responsive derivatives expressed nonspecific esterase when grown in CSF-1, but did not exhibit many other morphologic, immunologic, or functional properties of mononuclear phagocyte differentiation, or express murine CSF-1 receptors. Accelerated turnover of the human CSF-1 receptor was observed in response to CSF-1 and phorbol esters, but not after stimulation with IL-3 or bacterial lipopolysaccharide. Although both CSF-1 and IL-3 induced tyrosine phosphorylation of heterologous substrates in the dually responsive cells, differences in the patterns of substrate phosphorylation were observed in response to the two hematopoietins. We conclude that expression of the human CSF-1 receptor in 32DC13 cells not only induces CSF-1 responsiveness, but alters its phenotype in a way that prohibits granulocyte differentiation.

Antibody-induced mitogenicity mediated by a chimeric CD2-c-fms receptor.

A chimeric receptor composed of the extracellular domain of the human T-cell antigen CD2 (T11) joined to the membrane-spanning segment and the intracellular tyrosine kinase domain of the human colony-stimulating factor 1 receptor (CSF-1R) was expressed in murine NIH 3T3 fibroblasts. Stimulation of these cells with monoclonal antibodies to CD2 induced phosphorylation of the chimeric glycoprotein on tyrosine, receptor downmodulation, and mitogenesis. In contrast, neither human CSF-1R nor the chimeric receptor was able to function in interleukin-2-dependent murine T cells. In fibroblasts, then, CSF-1 per se is not required for activation of the receptor kinase or for a biological response, whereas in T cells, CSF-1R may be unable to engage the downstream signal transduction machinery.

Antibody-Induced Mitogenicity Mediated by a Chimeric CD2–c-fms Receptor

A chimeric receptor composed of the extracellular domain of the human T-cell antigen CD2 (T11) joined to the membrane-spanning segment and the intracellular tyrosine kinase domain of the human colony-stimulating factor 1 receptor (CSF-1R) was expressed in murine NIH 3T3 fibroblasts. Stimulation of these cells with monoclonal antibodies to CD2 induced phosphorylation of the chimeric glycoprotein on tyrosine, receptor downmodulation, and mitogenesis. In contrast, neither human CSF-1R nor the chimeric receptor was able to function in interleukin-2-dependent murine T cells. In fibroblasts, then, CSF-1 per se is not required for activation of the receptor kinase or for a biological response, whereas in T cells, CSF-1R may be unable to engage the downstream signal transduction machinery.