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G C Baldwin

Publications and source records attributed to G C Baldwin.

14 recordsLinked to original sources
PubMed1992

The biology of granulocyte-macrophage colony-stimulating factor: effects on hematopoietic and nonhematopoietic cells.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is one of a family of glycoprotein cytokines that have potent effects in stimulating the proliferation, maturation, and function of hematopoietic cells. Deriving its name from its ability to stimulate the formation of macroscopic colonies containing neutrophils, eosinophils, macrophages, or mixtures of these cell types, GM-CSF stimulates the proliferation and maturation of myeloid progenitors, as well as functionally activating mature neutrophils, eosinophils, and macrophages. As most of the effects observed using GM-CSF in vitro have been shown to occur in vivo either in animal models or in human subjects, it is important to consider that GM-CSF may also exert some biological effects on nonhematopoietic cells. In response to immunologic stimuli, immunologic surveillance cells and cells of the microenvironment are capable of producing GM-CSF. In vitro experiments indicate that GM-CSF production is tightly regulated. In that regard, GM-CSF is not present in measurable quantities in normal serum, but little is known about the in vivo process of GM-CSF production and regulation. The biologic capabilities of GM-CSF have triggered its widespread clinical use in situations where hematopoiesis is compromised. GM-CSF can act as a potent growth factor in vivo, increasing the number and enhancing the function of hematopoietic progenitors and mature cells. However, the precise in vivo effect that GM-CSF may have on normal and neoplastic cells of nonhematopoietic origin remains undefined. The full range of GM-CSF bioactivity is mediated following binding to its receptor. The presence of specific receptors for GM-CSF has been demonstrated in all responsive cells of hematopoietic lineage, as well as in nonhematopoietic cells, both responsive and unresponsive. In conclusion, a large body of work from a number of laboratories has defined the biology of GM-CSF. Currently available reagents and technology will provide additional insights into the biology of this molecule, thereby expanding our present definition and allowing us to explore the mechanisms regulating hematopoiesis.

Animals↗
PubMed1991

Identification and characterization of a low-affinity granulocyte-macrophage colony-stimulating factor receptor on primary and cultured human melanoma cells.

Hematopoietic growth factor receptors are present on cells of normal nonhematopoietic tissues such as endothelium and placenta. We previously demonstrated functional human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors on small cell carcinoma of the lung cell lines, and others have reported that certain solid tumor cell lines respond to GM-CSF in clonogenic assays. In the current study, we examine human melanoma cell lines and fresh specimens of melanoma to determine whether they have functional GM-CSF receptors. Scatchard analyses of 125I-GM-CSF equilibrium binding to melanoma cell lines showed a mean of 542 +/- 67 sites per cell with a kd of 0.72 +/- 0.14 nmol/L. Cross-linking studies in the melanoma cell line, M14, showed a major GM-CSF receptor species of 84,000 daltons. Under the conditions tested, the M14 cells did not have a proliferative response to GM-CSF in vitro, nor was any induction of primary response genes detected by Northern analysis in response to GM-CSF. Studies to determine internal translocation of the receptor-ligand complex indicated less than 10% of the 125I-GM-CSF internalized was specifically bound to receptors. Primary melanoma cells from five surgical specimens had GM-CSF receptors; Scatchard analysis was performed on one sample, showing 555 sites/cell with a kd of 0.23 nmol/L. These results indicate that human tumor cells may express a low-affinity GM-CSF receptor protein that localizes to the cell surface and binds ligand, but lacks functional components or accessory factors needed to transduce a signal.

Cell Line↗
PubMed1991

Macrophage-active colony-stimulating factors enhance human immunodeficiency virus type 1 infection in bone marrow stem cells.

To define the relationship between human immunodeficiency virus type 1 (HIV-1) infection in hematopoietic stem cells and virus production by their progeny, we performed kinetic studies infecting bone marrow (BM) stem cells and culturing them in the presence of hematopoietic growth factors. CD34-positive (CD34+), CD4-negative (CD4-) BM cells were isolated and infected in vitro with the monocytotropic HIV-1JR-FL strain or the laboratory-maintained HTLV-IIIB strain at a high multiplicity of infection. The cells were susceptible to productive infection only with HIV-1JR-FL, and virus production as measured by p24 protein release was markedly increased (more than fivefold) in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3). Macrophage CSF (M-CSF) was less stimulatory and granulocyte CSF (G-CSF) had no effect on virus production. Virus production coincided with proliferation of mononuclear phagocytes but was not related to granulocytic proliferation in G-CSF-treated BM cultures. Although peak virus production from GM-CSF-treated macrophages occurred 2 to 3 weeks after infection, peak virus production in infected stem cells was observed 5 to 6 weeks after. Enhancement in virus production had a more rapid onset when CD34+/CD4- cells were cultured in the presence of both GM-CSF and IL-3 for 7 or 14 days. Under these conditions there was a 10-fold enhancement in virus production after 7 days of preincubation and a 50-fold enhancement after 14 days. These data indicate that while the stem cell compartment may be susceptible to infection with a monocytotropic HIV-1 strain, productive and sustained infection is realized only after macrophage differentiation. The lack of effect of G-CSF on virus production is likely because of the limited effect of this hematopoietin on mononuclear phagocyte generation and function.

Antigens, CD↗
PubMed1990

Differentiating agents facilitate infection of myeloid leukemia cell lines by monocytotropic HIV-1 strains.

Monocytotropic human immunodeficiency virus type 1 (HIV-1) isolates from patients with acquired immunodeficiency syndrome (AIDS) infect mononuclear phagocytes as well as activated T cells, but do not usually infect immature human myeloid cell lines in vitro. The HL-60 promyelocytic/myeloblastic cell line and the promonocytic line, U937, were susceptible to productive infection by monocytotropic HIV-1 isolates (HIV-1JR-FL and HTLV-IIIBa-L) after treatment with retinoic acid, dimethyl sulfoxide, dibutyryl cAMP, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), or 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Virus production was only detected when these compounds were added before virus infection. Virus replication did not correlate with CD4 receptor expression because undifferentiated HL-60 cells express CD4 and the level of CD4 expression did not increase after differentiation in the presence of retinoic acid, 1,25(OH)2D3, or TPA. A mature monocytic cell line (THP-1) was capable of infection without pretreatment, and treatment with differentiating agents enhanced virus production. A chronically infected cell line (J-HL-60) was isolated after HIV-1JR-FL infection of HL-60 cells treated with retinoic acid. Virus production in this cell line was enhanced more than 10-fold after differentiation in the presence of 1,25(OH)2D3 or TPA. The majority of virus production by 1,25(OH)2D3-treated J-HL-60 cells was associated with the mature, adherent population. Molecular analysis of a cloned line of J-HL-60 showed integration of a single DNA provirus. These results suggest that cellular factors associated with precursor cell differentiation along the myelomonocytic pathway are required for optimal replication of monocytotropic HIV-1 strains in vitro.

Bucladesine↗
PubMed1990

Human granulocyte colony-stimulating factor: biologic activities and receptor characterization on hematopoietic cells and small cell lung cancer cell lines.

Human granulocyte colony-stimulating factor (G-CSF) is a regulatory glycoprotein that stimulates the production of neutrophilic granulocytes from committed hematopoietic progenitor cells both in vitro and in vivo. In this report, we show that biosynthetic (recombinant) human G-CSF enhances colony formation by normal human bone marrow and the human myeloid leukemic cell lines, HL-60 and KG-1, as well as nonhematopoietic small cell lung cancer lines, H128 and H69. G-CSF also modulates multiple differentiated functions of human neutrophils, including enhanced oxidative metabolism in response to f-Met-Leu-Phe (f-MLP), increased antibody-dependent cell-mediated cytotoxicity (ADCC), and augmented arachidonic acid release in response to ionophore and chemotactic agents. These effects are all maximal at a concentration of 100 to 500 pmol/L. Using 125I-labeled recombinant human G-CSF, high affinity binding sites were identified on human neutrophils, the myeloid leukemia cell lines KG-1 and HL-60, and the small cell carcinoma cell lines, H128 and H69. G-CSF receptor numbers ranged between 138 and 285 sites per cell with a kd of 77 to 140 pmol/L, consistent with the concentrations of G-CSF that elicit biologic responses in vitro. Decreased specific binding of 125l-G-CSF by human neutrophils was consistently observed in the presence of excess unlabeled human granulocyte-macrophage colony-stimulating factor (GM-CSF), suggesting competition or down modulation by GM-CSF of the G-CSF receptor.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1990

Responses of neutrophils to myeloid growth factors.

Colony-stimulating factors (CSFs) have important effects on mature myeloid cells in addition to their regulatory role in haemopoiesis. Exposure of neutrophils to granulocyte macrophage-CSF (GM-CSF) increases chemotaxis, phagocytosis and cytotoxicity and primes the cells for enhanced oxidative metabolism in response to stimuli, such as formylated oligopeptides derived from bacteria (f-Met-Leu-Phe) and endogenous activated complement components (C5a). GM-CSF induces time-dependent changes in neutrophil f-Met-Leu-Phe receptor number and affinity that correspond to changes in functional activity. The neutrophil IgA Fc receptor is also modulated by GM-CSF such that it develops a high affinity state and transduces a phagocytic signal. The ability to regulate the number and activity of mature myeloid effector cells in vivo establishes unique therapeutic opportunities in the area of infectious disease, cancer treatment, bone marrow transplantation and augmentation of host defence in immunodeficient patients.

Animals↗
PubMed1990

Human immunodeficiency virus causes mononuclear phagocyte dysfunction.

There is compelling clinical evidence for dysfunction of the mononuclear phagocyte system in patients with AIDS, which is believed due in part to loss of T-cell cooperativity. The direct consequences of human immunodeficiency virus infection on macrophage function are unknown. To address this question we infected normal human macrophages in vitro with a monocytotropic strain of human immunodeficiency virus and performed assays to quantify their extra- and intracellular killing ability. Human immunodeficiency virus-infected macrophages were significantly less effective than control cells in mediating antibody-dependent cell-mediated cytotoxicity against leukemic cell targets and intracellular killing of Candida pseudotropicalis. The functional defects were profound, related temporarily to active virus production by the macrophages, and could not be overcome by granulocyte-macrophage colony-stimulating factor. Treatment of macrophages with 3'-azido-3'-deoxythymidine (AZT) 6 days after infection caused a marked decrease in virus production and prevented development of the intracellular killing functional defect. The results suggest that early antiviral therapy may be useful in preventing or mitigating some virus-induced mononuclear phagocyte dysfunction.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1989

Granulocyte- and granulocyte-macrophage colony-stimulating factors enhance neutrophil cytotoxicity toward HIV-infected cells.

Although the control of retroviral disease in animal systems often involves antibody-dependent cell-mediated cytotoxicity (ADCC), the role of cytotoxic function in human retroviral disorders is uncertain. The ability of the neutrophil to kill HIV-infected targets directed by antiviral antibody was examined. Neutrophils from patients with AIDS killed HIV-infected MOLT-3A cells in a manner equivalent to neutrophils obtained from normal volunteers. Both granulocyte- and granulocyte-macrophage colony-stimulating factors (G-CSF and GM-CSF) markedly augmented the cytotoxic function. Studies done with fractionated human antisera revealed that ADCC to HIV-infected cells was mediated only by antibody to the env glycoprotein. ADCC in this system was not dependent on oxidative metabolism because neutrophils from patients with chronic granulomatous disease (CGD) were capable of CSF-augmented cytotoxicity. Although ADCC can be mediated by various classes of lymphocytes and mononuclear phagocytes, such cells may be infected by HIV. Because the neutrophil apparently is not productively infected by the virus, it is an ideal cell to focus on with regard to cytotoxic function in AIDS patients. The findings regarding neutrophil ADCC in AIDS are clinically relevant because the availability of CSFs now permits therapeutic regulation of neutrophils in AIDS patients, and presumably natural antibody may be useful in targeting HIV-infected cells for neutrophil cytotoxicity in vivo.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1989

Nonhematopoietic tumor cells express functional GM-CSF receptors.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the colony growth of myeloid progenitors in semisolid media, and enhances the function of mature effector cells, including neutrophils, monocytes, and eosinophils. Small cell carcinoma lines (SCCL) have properties of amine precursor uptake and decarboxylation (APUD) cells and express high levels of the enzyme, L-aromatic amino acid decarboxylase. We looked for possible expression of GM-CSF receptors on nonhematopoietic cells and found specific high-affinity binding of human GM-CSF to SCCL and to the SV40-transformed African green monkey kidney cell line, COS. The small cell carcinoma lines responded to GM-CSF with enhanced proliferation, and both small cells and COS cells were found to express authentic 84,000 dalton GM-CSF receptor protein. These findings indicate that nonhematopoietic cells can bind and respond to GM-CSF, suggesting additional biological activities as well as the possibility of tumor responses when GM-CSF is used therapeutically in humans. Since preliminary clinical trials using CSFs as adjunctive treatment in patients with solid tumors are underway, it will be important to consider the possible responsiveness of nonhematopoietic tumor cells to CSFs.

Carcinoma, Small Cell↗
PubMed1988

Therapy for neutropenia in hairy cell leukemia with recombinant human granulocyte colony-stimulating factor.

STUDY OBJECTIVE: To determine whether recombinant human granulocyte colony-stimulating factor (G-CSF) is effective in increasing neutrophil counts in patients with hairy cell leukemia and neutropenia. DESIGN: Open label, phase I/II study of G-CSF, given by daily subcutaneous injection for up to 7 weeks. SETTING: Outpatient oncology clinic of a university medical center. PATIENTS: A consecutive sample of four patients with hairy cell leukemia complicated by severe neutropenia. Three patients completed the study; one patient was removed after 2 weeks of therapy. INTERVENTIONS: Granulocyte colony-stimulating factor was given by daily subcutaneous injection. Each patient began therapy with 1 microgram/kg body weight.d; after 1 week the dose was increased to 3 micrograms/kg.d, and 1 week later to 6 micrograms/kg.d. Therapy was continued for 5 to 6 weeks. Patients were taught self-injection, and administered treatment at home. MEASUREMENTS AND MAIN RESULTS: In three patients, an increase in absolute neutrophil counts from less than 0.9 X 10(9)/L to greater than 4.0 X 10(9)/L was noted within 2 weeks of beginning G-CSF therapy. In two patients, infections resolved during therapy. One patient developed acute neutrophilic dermatosis (the Sweet syndrome) while receiving 3 micrograms/kg.d of G-CSF, and drug therapy was discontinued. CONCLUSIONS: Granulocyte colony-stimulating factor may increase neutrophil counts within 2 weeks in patients with hairy cell leukemia and neutropenia. This therapy may be a useful adjunct to definitive treatment of hairy cell leukemia with interferon or pentostatin.

Agranulocytosis↗
PubMed1988

Granulocyte-macrophage colony-stimulating factor enhances neutrophil function in acquired immunodeficiency syndrome patients.

We conducted a clinical trial of human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in leukopenic patients with acquired immunodeficiency syndrome (AIDS) and analyzed neutrophil function before, during, and after in vivo administration of rGM-CSF. Prior to GM-CSF infusion, AIDS patients' neutrophil superoxide generation and neutrophil antibody-dependent cell-mediated cytotoxicity were enhanced normally by in vitro exposure to GM-CSF. Neutrophil phagocytosis and intracellular killing of Staphylococcus aureus were also normal in the majority of these patients. Two patients, however, had discrete neutrophil functional defects: one in phagocytosis and one in intracellular killing. During the period of GM-CSF infusion, these abnormalities were corrected. The number of circulating neutrophils increased in all patients treated with GM-CSF in a dose-dependent manner. Neutrophils produced in vivo in response to GM-CSF administration functioned normally and there was evidence for neutrophil priming and activation in vivo. We conclude that GM-CSF treatment of AIDS patients leads to the production of functionally active neutrophils, suggesting therapeutic potential for GM-CSF in the treatment of patients with impaired host defense.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Biosynthetic granulocyte-macrophage colony-stimulating factor enhances neutrophil cytotoxicity toward human leukemia cells.

Purified biosynthetic (recombinant) human granulocyte-macrophage colony-stimulating factor (GM-CSF) enhances antibody-dependent cell-mediated cytotoxicity (ADCC) of human neutrophils toward human promyelocytic leukemia cells (HL-60), B-lymphoma cells, and human T-leukemia virus II-infected human B-lymphoblastoid cells. The stimulation of antibody-dependent cell-mediated cytotoxicity is rapid (less than an hour), occurs at picomolar concentrations of GM-CSF, and does not require the presence of GM-CSF during the killing reaction. Therefore, neutrophils may be targeted toward tumor cells by antibody and their tumoricidal activity enhanced by GM-CSF in vitro. These results suggest that GM-CSF may have therapeutic utility in cancer therapy by increasing the number and activity of effector cells directed toward tumors by receptors to the immunoglobulin Fc fragment.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

Electrophoretic variation between class II molecules expressed on HLA-DRw8 homozygous typing cells reveals multiple distinct haplotypes.

Two-dimensional (2D) gel electrophoresis of immunoprecipitated HLA-DR antigens from eight homozygous typing cells (HTC) expressing the HLA-DRw8 specificity revealed a clustering of polymorphic beta chain patterns into distinct electrophoretic variants. The variant patterns correlate with three discrete HLA-D clusters that are defined in the mixed leukocyte culture reaction (MLR) using DRw8-positive HTC. These HLA-D clusters have been provisionally designated Dw"8.1", detected primarily in Caucasoids, Dw"8.2", detected primarily in American Indians, and Dw"8.3", detected predominantly in Orientals. All three HLA-Dw"8.1" cell lines express a single DR-locus product as defined by immunoprecipitation with a DR-specific monoclonal antibody, P4.1. This DR beta chain is identical among the Dw"8.1" cell lines and different from the DR beta chains of the Dw"8.2" and Dw"8.3" cell lines. Two separate Dw"8.2" HTC express a shared DR beta chain that is slightly more basic than the 8.1 DR molecule; interestingly, one of these lines also expresses an additional DR-like beta chain not found in the other cells. Thus, the two lines defining the Dw"8.2" cluster share one distinct class II molecule, but differ in another and therefore are not biochemically HLA-identical. Cells from the Dw"8.3" cluster are likewise distinct from all other Dw8 clusters. One additional DRw8-positive HTC has been analyzed and found to be distinct from the Dw"8.1", "8.2" and "8.3" clusters by both MLR and 2D gels. Immunoprecipitates using monoclonal antibody 1B5 [anti-DR and anti-DQ(DS)] identify additional polymorphic class II variants among the cell lines tested. These data indicate that HLA-DRw8 is a public serologic specificity present on class II molecules expressed on multiple distinct haplotypes. These haplotypes differ from each other in expression of polymorphic class II molecules encoded by at least two HLA loci. They also differ in HLA-D, even though they all type as HLA-DRw8 homozygous. In Dw"8.2", variation in expressed beta chains is not reflected in variation in HLA-D, indicating that MLR, as well as serologic typing, does not detect the full degree of allelic polymorphism within HLA.

Antibodies, Monoclonal↗