Biomedical subjects

C C Paul

Publications and source records attributed to C C Paul.

At least 19 recordsLinked to original sources

PubMed2001

Modulation of MEK activity during G-CSF signaling alters proliferative versus differentiative balancing.

Previous studies of the granulocyte colony stimulating factor (G-CSF) receptor have demonstrated that discrete signals direct proliferative and maturation signaling. Receptor deletion/mutant studies have shown that although activation of the ras-mitogen activated protein (MAP) kinase pathway is necessary for G-CSF directed proliferation, it is not necessary for maturation induced by this cytokine. We have assessed the effects of selective inhibition or overexpression of MAP kinase kinase (MEK) in a cell line model of G-CSF-induced neutrophil progenitor growth. Using the human G-CSF responsive MPD cell line, we specifically inhibited MEK using PD 98059 and also transfected MPD cells with a constitutively active MEK construct. We then exposed the cells to G-CSF and assessed the effects of MEK inhibition and forced expression on proliferation and differentiation. Inhibition of MEK followed by G-CSF stimulation consistently resulted in an early 2.5-fold increase in morphologically differentiated neutrophils expressing CD11b and CD16 and containing lactoferrin over that produced by G-CSF alone. MEK inhibition alone had little effect on the differentiation stage of these cells, although proliferation was impaired. Forced expression of activated MEK resulted in a three- to five-fold decrease in differentiated, lactoferrin containing neutrophilic cells resultant from G-CSF induction, and a commensurate increase in cell proliferation. These observations suggest that modulation of MAPK activation may be a control point for altering the balance between proliferation and differentiation in response to G-CSF. Physiologically, this control is likely exerted by costimulatory cytokines.

Cell Differentiation↗

PubMed2001

MAP kinase upregulation after hematopoietic differentiation: role of chemotaxis.

Mitogen-activated protein kinase (MAPK) isoform p42 is known to be active in exponentially growing cells at several points of the cell cycle. A high basal activity was present in three cell lines representative of immature myeloid cells tested: uHL-60, AML-14, and MPD. However, DMSO-induced differentiation of HL-60 cells (dHL-60) and subsequent expression of the neutrophilic phenotype occurred with a concomitant reduction on the basal level of MAPK activity. Simultaneously, extracellular stimuli like the cytokine granulocyte/macrophage colony-stimulating factor (GM-CSF) induced a fast (<10 min) and robust response. In terms of MAPK activity, the more mature the cell was, the higher the corresponding activity, in the three differentiation series considered: AML-14 < 3D10; MPD < G-MPD; uHL-60 < dHL-60 < neutrophils. Interestingly, peripheral blood neutrophils expressed the highest (16-fold) MAPK activation level in response to GM-CSF. Finally, using the specific MAPK inhibitor PD-98059, we demonstrated that MAPK activation is needed for neutrophil chemotaxis toward interleukin-8 and its priming by GM-CSF. Since neutrophils are terminally differentiated cells, GM-CSF does not serve a purpose in proliferation, and it must trigger the recruitment of selective signal transduction pathways particular to that final stage that includes enhanced physiological functions such as chemotaxis.

Cell Differentiation↗

PubMed2000

Strain-dependent productive infection of a unique eosinophilic cell line by human immunodeficiency virus type 1.

Eosinophils are granulocytic leukocytes that function in both protective and pathological immune responses. They can be infected by HIV-1, but characterization of the infection has been hindered by lack of a productive cell culture model. In the present study, the unique eosinophilic cell line AML14.3D10 was used as a model to test the hypothesis that HIV-1 productively infects eosinophilic cells in a strain-dependent fashion. The AML14.3D10 cell line was cultured with one T cell-tropic (T-tropic) strain and two macrophage-tropic (M-tropic) strains of HIV-1 (HTLV-IIIB, HIV-1AdaM, and HIV-1Ba-L strains, respectively). Cytopathic effects were evident in living cultures and in stained slide preparations of AML14.3D10 cells infected with the T-tropic strain of HIV-1. Culture supernatants from infected AML14.3D10 cells contained high levels of HIV-1 p24 protein that peaked at approximately 7-10 days postinfection. A line of AML14.3D10 cells chronically infected with HTLV-IIIB and continuously producing high levels of virus was established. In contrast to the T-tropic strain, the M-tropic strains of HIV-1 did not productively infect the eosinophilic cell line. Thus, the AML14.3D10 eosinophilic cell line was permissive for a T-tropic strain but not for M-tropic strains of HIV-1. Flow cytometry revealed that uninfected AML14.3D10 cells were positive for the HIV-1 receptor CD4 and coreceptors CXCR4 and CCR5; the cell line was negative for CCR3. The lack of productive infection by M-tropic strains despite CCR5 expression indicates that strain-dependent infection may not be determined at the coreceptor level in AML14.3D10 cells.

Cytopathogenic Effect, Viral↗

PubMed2000

Human cell line that differentiates to all myeloid lineages and expresses neutrophil secondary granule genes.

The aim of this study was to characterize a human leukemic cell line that appears capable of spontaneous differentiation to all myeloid lineages. The MPD cell line was derived using standard tissue culture techniques from the peripheral blood of a patient with an aggressive nonchronic myelogenous leukemia myeloproliferative disorder. Immunophenotyping, cytogenetic analysis, reverse transcriptase polymerase chain reaction, Northern blotting, immunoblotting, and colony assays were used to characterize the line and to assess its ability to express lineage-specific genes representative of advanced differentiation.Light microscopic morphologic analysis of the MPD cell line suggests that it has the unique property of spontaneous differentiation to mature-appearing neutrophils, macrophages, eosinophils, and basophils in proportions that approximate those found in normal bone marrow or peripheral blood. It was demonstrated that this cell line is capable of producing lineage-specific mRNA and granule proteins of at least two myeloid lineages, neutrophil and eosinophil, including neutrophil secondary granule proteins, which are not expressed in other available human cell lines. MPD cells were found to be capable of producing differentiated myeloid colonies (neutrophil, eosinophil, macrophge, mixed) in semisolid medium. The ability of MPD cells to express genetic programs associated with advanced differentiation of multiple myeloid lineages will make it a valuable tool for the study of the processes underlying lineage commitment and the regulation of expression of lineage-specific genes.

Basophils↗

PubMed1998

The AML14 and AML14.3D10 cell lines: a long-overdue model for the study of eosinophils and more.

Over the past three decades, a number of myeloid cell lines have been established and have proven useful for the study of various aspects of normal and disordered hematopoiesis. However, one myeloid lineage for which a useful cell line model has been sorely lacking is the eosinophil. We review the characteristics of the recently developed AML14 and AML14.3D10 cell lines and summarize how they have been used to obtain important new information relevant to eosinophil biology. Observations regarding the apparent ability of the AML14.3D10 cell line to "switch" lineages and to produce and use GM-CSF in an autocrine fashion are also reviewed.

Aged↗

PubMed1997

Autocrine activation of the IL-3/GM-CSF/IL-5 signaling pathway in leukemic cells.

The AML14.3D10 human myeloid leukemic cell line expresses receptors for granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-5 (IL-5), but not IL-3. We have found that this cell line produces GM-CSF in amounts up to 113 pg/ml in culture supernatants. Deprivation of endogenous GM-CSF by addition of neutralizing anti-GM-CSF antibody strongly inhibits proliferation of the cells, suggesting a GM-CSF autocrine growth mechanism. To examine whether endogenously produced GM-CSF activates intracellular GM-CSF/IL-3/IL-5-related signal transduction pathways, we performed antiphosphotyrosine immunoblotting of cell lysates of AML14.3D10 cells before and after deprivation of endogenous GM-CSF. We found constitutive tyrosine-phosphorylation of a number of proteins in AML14.3D10 that could not be detectably increased by the addition of exogenous GM-CSF, IL-3, or IL-5. However, GM-CSF-deprived cells demonstrated a marked increase in phosphorylation of proteins of identical molecular mass following addition of GM-CSF and IL-5, but not IL-3, consistent with the receptor expression of the cells and the known use of the same signaling pathways by the three cytokines. This suggests that AML14.3D10 cells use endogenously produced GM-CSF to activate signal transduction pathways, interfering with activation by exogenous cytokine until the endogenous stimulation is removed. We then assessed the activation of the beta-subunit common to the GM-CSF/IL-3/IL-5 receptors (beta c), JAK2 and p53/56 lyn, known to be involved in the common signaling pathways of the three cytokines. We found that phosphorylation of beta c and JAK2 in response to GM-CSF and IL-5 could be markedly enhanced by depriving cells of endogenous GM-CSF. Constitutive hyperphosphorylation of lyn was found in AML14.3D10 cells, and no further activation of lyn in response to cytokine was demonstrable in GM-CSF-deprived cells, suggesting that lyn is activated in this cell line by a mechanism other than GM-CSF. These studies represent the first demonstration of autocrine activation of intracellular cytokine signaling pathways by malignant hematopoietic cells. Because the addition of anti-GM-CSF to cell cultures improved responsiveness of intracellular signal transducing molecules to exogenous GM-CSF and IL-5, it can be inferred that endogenously produced GM-CSF exerts its effects by secretion and binding to surface GM-CSF receptors, although an intracellular component to signaling cannot be excluded. These observations provide further information regarding an autocrine contribution to leukemic cell growth, and establish a new model for study of these events.

Antibodies↗

PubMed1997

Interleukin-5 and human B lymphocytes.

Interleukin-5 was initially characterized in murine systems, where it was found to have B-lymphocyte proliferative and differentiative activity and to promote the growth of eosinophils. Recombinant production of human IL-5 was soon accomplished by using murine IL-5 cDNA to isolate the highly homologous human sequence. Although human IL-5 was also found to be an eosinophil-active growth factor, a significant biologic effect of IL-5 on human B lymphocytes was initially difficult to demonstrate. More recently, reports from our own laboratory and other laboratories have provided evidence that IL-5 does have activity on human B lymphocytes and that human B lymphocytes may even produce IL-5 in some situations, suggesting the possibility of autocrine stimulatory mechanisms. However, we and others have failed to demonstrate the known heterodimeric high-affinity IL-5 receptor on human B lymphocytes, in spite of evidence that we have accumulated suggesting that human B lymphocytes specifically bind IL-5. We review our own work and that of others in an area that will remain controversial until a human B-lymphocyte IL-5 receptor is definitively identified and characterized.

Antibodies↗

PubMed1996

S6 kinase p90rsk in granulocyte-macrophage colony-stimulating factor-stimulated proliferative and mature hematopoietic cells.

The ribosomal S6 kinase p90(rsk) was studied in mature and proliferating hemopoietic cells in response to the human cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF). In neutrophils, GM-CSF induced time-dependent electrophoretic mobility shifts in immunoreactive p90(rsk). Although these shifts suggested changes in the phosphorylation status of the molecule, a kinase assay with whole cell lysates detected minimal (1.5-fold) increments in enzymatic activity. Only immunoprecipitation followed by immune complex kinase assay or in-gel kinase assay performed against the RSK substrate RRLSSLRA evidenced an increase in p90(rsk) activity (3.4-fold). p90(rsk) was also detected in the GM-CSF-dependent erythroleukemia cell line TF-1. Normally cultured, cytokine-supplemented cells did not respond to further GM-CSF stimulation. However, the activity of p90(rsk) in cytokine-starved cells increased dramatically in response to short term GM-CSF challenge. This effect was readily observable in total cell lysates (6.6-fold increase over controls) and was paralleled by changes in mitogen-activated protein kinase activity (a substrate of p90(rsk)). Thus, p90(rsk) is present in mature hemopoietic cells, but the extent of the enzymatic response to GM-CSF is significantly lower than that seen in proliferative cells.

Amino Acid Sequence↗

PubMed1996

Interleukin-5 receptor alpha subunit gene regulation in human eosinophil development: identification of a unique cis-element that acts lie an enhancer in regulating activity of the IL-5R alpha promoter.

Further functional and biochemical characterization of the nuclear factor(s) which interacts with the EOS1 enhancer-like element in the IL-5R alpha promoter is currently in progress. Since different transcription factors recognize and interact with DNA in distinct fashions and with distinct structural motifs, we have modeled potential binding of the EOS1 factor to its cis-element based upon its methylation interference pattern (Fig. 2), using a cylindrical DNA helical projection (Fig. 6). Over a length of two helical turns, all nuclear protein contacts indicated by methylation interference map to one side of the DNA helix, suggesting that EOS1 binds in the major groove, across the minor groove, and on only one side of the helix. Further review of the model also reveals a potential diad symmetry for the binding site, suggestive of binding by a homodimer and consistent with the formation of the two DNA-protein complexes in our electrophoretic mobility shift experiments that could represent interactions with monomer versus dimer. Comparison of the EOS1 binding motif to similar models for the binding of other transcription factor families for which structural crystallographic and/or binding data is available suggests a similarity of the EOS1 complex to that of the bacterial helix-turn-helix phage lambda and 434 repressor-operator complexes, and the Cys4 zinc finger glucocorticoid response element (GRE) DNA-binding motifs, all of which show similar diad symmetry and binding in the major groove on one side of the DNA. The possibility that EOS1 functions as a GRE is being investigated, especially since there is a consensus AP-1 site at bp -440 to -432 of the IL-5R alpha promoter, immediately adjacent to the EOS1 binding site (see Fig. 5 in reference [36]) and AP-1/GRE interactions have been identified for composite response elements in the regulation of a number of different genes. The identification or cloning of EOS1, a potentially novel and eosinophil lineage-active transcription factor, should enhance our understanding of the processes involved in eosinophil development in particular and myeloid lineage commitment and differentiation in general.

Animals↗

PubMed1995

Changing the differentiation program of hematopoietic cells: retinoic acid-induced shift of eosinophil-committed cells to neutrophils.

The mechanisms by which hematopoietic progenitor cells become lineage-committed remain poorly understood. A cloned subline of the AML14 cell line (AML14.3D10) that spontaneously differentiates to eosinophilic myelocytes in the absence of cytokine stimulation was obtained by limiting dilution. This subline exhibits augmented expression of interleukin-5 (IL-5) receptor alpha subunit mRNA and synthesizes all major eosinophil granule proteins. Exposure of this cell line to all-trans retinoic acid (ATRA) causes loss of eosinophilic granules and fast green staining within 48 hours, without cell death. In addition, mRNA for the IL-5 receptor alpha subunit becomes undetectable by 48 hours and the cells lose responsiveness to IL-5. Major basic protein, measured as a marker of eosinophilic granule content, decreases from more than 16 pg/cell to undetectable levels by 5 days after ATRA. Concomitant with the loss of major basic protein and fast green staining, surface expression of CD16 becomes detectable and is maximum by 10 days after ATRA. mRNA for the granulocyte colony-stimulating factor (G-CSF) receptor becomes detectable by day 5, and the cells become responsive to G-CSF. At this time, the cells appear morphologically as mature neutrophils and can reduce nitroblue tetrazolium. With continued culture, the neutrophilic cells die and the culture becomes repopulated with eosinophilic myelocytes. These findings show that it is possible to change the differentiation program of hematopoietic cells even after they show evidence of advanced lineage commitment. The AML14.3D10 subclone of AML14 will be a valuable model for study of the transcriptional regulation of the eosinophil and neutrophil differentiation programs and lineage-specific gene expression.

Base Sequence↗

PubMed1995

Identification and characterization of a functional promoter region in the human eosinophil IL-5 receptor alpha subunit gene.

The molecular basis for the commitment of multipotential myeloid progenitors to the eosinophil lineage, and the transcriptional mechanisms by which eosinophil-specific genes are subsequently expressed and regulated during eosinophil development are currently unknown. Interleukin-5 (IL-5) is a T cell and mast cell-derived cytokine with actions restricted to the eosinophil and closely related basophil lineages in humans. The high affinity receptor for IL-5 (IL-5R) is composed of an alpha subunit (IL-5R alpha) expressed by the eosinophil lineage, that associates with a beta c subunit shared with the receptors for IL-3 and granulocyte-macrophage colony stimulating factor (GM-CSF). As a prerequisite to studies of the transcriptional regulation of the IL-5R alpha subunit gene, we used three different methods, including primer extension, RNase protection, and 5'-RACE to precisely map the transcriptional start site to a position 15 base pairs (bp) upstream of the 5' end of the published sequence of IL-5R alpha exon 1. To initially identify the IL-5R alpha promoter, 3.5 kilobases (kb) and 561 bp of the 5' sequence flanking the transcriptional start site were subcloned into the promoterless pXP2-luciferase vector. Transient transfection of these constructs into an eosinophil-committed HL-60 subline, clone HL-60-C15, induced the expression of approximately 240-fold greater luciferase activity than the promoterless vector, identifying a strong functionally active promoter region within the 561 bp of sequence proximal to the transcriptional start site and with activity equivalent to pXP2 constructs containing the entire 3.5 kb of upstream sequence. To more precisely localize the cis-acting regulatory elements in this region important for promoter activity, a series of 5' deletion mutants of the 561-bp region were generated in the pXP2-luciferase vector. Deletion of the region between bp -432 and -398 reduced promoter activity by more than 80% in the HL-60-C15 cell line. Further analyses of the activity of the IL-5R alpha promoter constructs in various other eosinophil, myeloid, and non-myeloid cell lines indicated that the promoter was relatively myeloid and eosinophil lineage-specific in its expression. Consensus sequences for known transcription factor binding sites were not present in the 34-bp region of the promoter required for maximal activity, suggesting unique myeloid- and possibly eosinophil-specific regulatory elements.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗

PubMed1994

Cytokine induction of granule protein synthesis in an eosinophil-inducible human myeloid cell line, AML14.

Study of eosinophil growth and differentiation has been hampered by the difficulty of obtaining adequate numbers of highly purified eosinophil progenitors or mature eosinophils for analysis. The AML14 myeloid leukemia cell line has the unusual ability to exhibit eosinophilic differentiation in response to stimulation by combinations of the eosinophil-active cytokines interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5. We now demonstrate that AML14 cells can be stimulated by a combination of these cytokines to produce mRNA encoding all the eosinophil granule proteins, including major basic protein (MBP), eosinophil peroxidase (EPO), eosinophil cationic protein (ECP), eosinophil-derived neurotoxin (EDN), and the Charcot-Leyden crystal (CLC) protein (eosinophil lysophospholipase). The production of the mature proteins was demonstrated by Western blotting, and ultrastructural analysis demonstrated the presence of immature secondary granules in cells that had been induced to differentiate to eosinophils. These findings demonstrate the utility of the AML14 cell line as a model for the study of cytokine induction of eosinophil growth and differentiation.

Base Sequence↗

PubMed1993

Cooperative effects of interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor: a new myeloid cell line inducible to eosinophils.

The cytokines interleukin-3 (IL-3); IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) are known to contribute to the proliferation and differentiation of eosinophil progenitors. Recently, it was determined that the cellular receptors for these three cytokines share a common beta-chain while having unique alpha-chains. Thus, there is considerable interest in how these cytokines and their receptors interact in promoting production of eosinophils. We have established a cell line (AML14) from a patient with acute myelogenous leukemia that will consistently exhibit eosinophilic differentiation in suspension in response to IL-3, IL-5, and GM-CSF. Proliferation with only modest differentiative effects was observed in response to a single cytokine. Combinations of two cytokines gave variable results, with GM-CSF + IL-3 and IL-3 + IL-5 causing more proliferation than a single cytokine but little more differentiation. The combination of GM-CSF + IL-5 caused marked enhancement of eosinophilic differentiation with only modest augmentation of proliferation. The combination of all three cytokines was most effective in stimulating both proliferation and eosinophilic differentiation (up to 70% of cells) of AML14 cells. Specific binding of GM-CSF and IL-5 to AML14 cells can be conveniently studied by flow cytometric methods, and cross-competition of these two cytokines for their respective receptors was demonstrated. IL-3 was shown to partially compete for IL-5 binding on AML14 cells. Although specific IL-3 binding could not be demonstrated by flow cytometry, mRNA for the alpha-chains of the IL-3, IL-5, and GM-CSF receptors and the beta-chain common to all three receptors was detected in AML14 cells. The AML14 cell line may be a useful model for the study of cooperative interactions of IL-3, IL-5, GM-CSF, and their respective receptors in the promotion of eosinophil progenitor growth and differentiation.

Aged↗

PubMed1992

Interleukin-5 is an autocrine growth factor for Epstein-Barr virus-transformed B lymphocytes.

Because of the recent finding that interleukin-5 (IL-5) is produced by Epstein-Barr virus-transformed B lymphocytes (EBV-B cells), we performed studies to ascertain whether EBV-B cells might use IL-5 by an autocrine mechanism. EBV-B cells known to be IL-5 producers were capable of responding to addition of exogenous IL-5 by dose-related augmented proliferation. The addition of a neutralizing anti-IL-5 antibody reduced these effects and also dose-dependently inhibited proliferation and reduced viability of unsupplemented EBV-B cells, having a maximum effect at about 120 hours. In contrast, no stimulatory effect of IL-5 was noted on Burkitt's lymphoma cell lines, nor were these lines growth-inhibited by anti-IL-5 antibody. With biotinylated IL-5, (b-IL-5) second labeling with streptavidin-FITC, and flow cytometric analysis, binding of IL-5 to EBV-B cells cultured in fresh medium was demonstrated and could be competed for by excess unlabeled IL-5, suggesting the presence of IL-5-specific binding sites. Binding of IL-5 was reduced on cells cultured for longer periods before study but could be restored by extensively washing cells before labeling them with b-IL-5, suggesting that surface binding sites had become occupied by endogenously produced IL-5. These findings support a role for IL-5 in autocrine support of EBV-B cell growth.

Antibodies↗

PubMed1992

Effects of interleukin-5 on acute myeloid leukemias.

Because of the known activity of interleukin-5 (IL-5) as a growth factor for human eosinophils, we performed studies to ascertain whether M4Eo acute leukemia cells might be capable of responding to IL-5. Surprisingly, short term incubation of freshly isolated M4Eo blasts with rhIL-5 induced differentiation of the cells to macrophages. To determine whether other variants of acute myelogenous leukemia (AML) might also be capable of responding to IL-5, we studied cells from four additional unselected cases and found that one responded to IL-5 by vigorous proliferation. Using biotinylated rhIL-5, second labelling with streptavidin-fluorescein isothiocyanate (FITC) and flow cytometric analysis, specific binding of IL-5 to both responsive leukemias was demonstrated, suggesting the presence of specific IL-5 receptors. Additional study will be needed to assess the frequency of IL-5 responsiveness in AML and to determine the relationship of these phenomena to the physiologic role of IL-5 in the regulation of hematopoiesis.

Cell Differentiation↗

PubMed1991

Regional and systemic CD4 and CD8 subsets in bronchogenic carcinoma.

We studied lung and blood lymphocytes from 12 asymptomatic patients with peripheral bronchogenic carcinoma. Bronchoalveolar lavage was performed in the lung segment with tumor and a contralateral uninvolved lung segment and analyzed separately. After partial removal of macrophages by plastic adherence, cells were labeled with markers for CD4 and CD8 and analyzed by flow cytometric analysis. We found no significant difference in the percentages of mononuclear cells in either immune subset when comparing the lung containing tumor with the uninvolved lung. We did find, however, a depressed CD4/CD8 ratio in the peripheral blood. We conclude that a lung carcinoma does not change the local immunologic milieu of the lung parenchyma containing the carcinoma. It is not clear if the immunologic findings in the lungs and blood are due to the bronchogenic carcinoma, smoking, or the underlying chronic obstructive pulmonary disease.

Aged↗

PubMed1990

Epstein-Barr virus transformed B lymphocytes produce interleukin-5.

Interleukin-5 (IL-5) has previously been isolated only as a product of T lymphocytes. We have found that Epstein-Barr virus transformed B lymphocytes produce large amounts of IL-5 activity in culture supernatants, inducing proliferation of murine BCL1 cells, and supporting the selective growth of eosinophil colonies in semi-solid culture. Production of IL-5 messenger RNA by transformed B-cell lines was verified by Northern analysis using a 3.2-kilobase cloned DNA fragment containing the full-length human IL-5 gene, and immunoreactive IL-5 was detected in B-cell culture supernatants. These findings suggest a possible expanded role for the B cell in the induction of eosinophilia, and should serve as a focus for additional investigation into possible roles for IL-5 in human B-cell proliferation and differentiation.

B-Lymphocytes↗

PubMed1990

Modulation of spontaneous outgrowth of Epstein-Barr virus immortalized B-cell clones by granulocyte-macrophage colony-stimulating factor and interleukin-3.

Spontaneous outgrowth of immortalized Epstein-Barr virus (EBV) infected B-cell clones will occur from cultures of peripheral blood mononuclear cells (PBMNCs) of some persons with a history of EBV infection. We determined that outgrowth of such clones may be reproducibly modulated by supplementation of cultures with the hematopoietic growth factors GM-CSF and interleukin-3 (IL-3). Continuous supplementation of cultures with GM-CSF facilitates emergence of immortalized B-cell clones, whereas supplementation with IL-3 completely prevents their emergence. The effect of GM-CSF may be direct, at least in part, as the proliferation of pure clones of EBV-transformed B lymphocytes was augmented in response to GM-CSF. An indirect mechanism appears to be responsible for the inhibition of transformed B-cell outgrowth in response to IL-3, as IL-3 had no inhibitory effect on proliferation of pure transformed B-cell clones and IL-3-mediated inhibition could be eliminated by antibody neutralization of gamma-interferon (gamma-IFN) or tumor necrosis factor-alpha (TNF-alpha) early in culture. The mechanisms of these effects deserve further study and may have clinical relevance to use of hematopoietic growth factors for support of bone marrow (BM) function in immunocompromised patients.

B-Lymphocytes↗