Vitamin C inhibits granulocyte macrophage–colony-stimulating factor–induced signaling pathways

Blood ◽  
2002 ◽  
Vol 99 (9) ◽  
pp. 3205-3212 ◽  
Author(s):  
Juan M. Cárcamo ◽  
Oriana Bórquez-Ojeda ◽  
David W. Golde
Keyword(s):  
Vitamin C ◽  
Map Kinase ◽  
Luciferase Reporter ◽  
Enzymatic Reactions ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract Vitamin C is present in the cytosol as ascorbic acid, functioning primarily as a cofactor for enzymatic reactions and as an antioxidant to scavenge free radicals. Human granulocyte macrophage–colony-stimulating factor (GM-CSF) induces an increase in reactive oxygen species (ROS) and uses ROS for some signaling functions. We therefore investigated the effect of vitamin C on GM-CSF–mediated responses. Loading U937 cells with vitamin C decreased intracellular levels of ROS and inhibited the production of ROS induced by GM-CSF. Vitamin C suppressed GM-CSF–dependent phosphorylation of the signal transducer and activator of transcription 5 (Stat-5) and mitogen-activated protein (MAP) kinase (Erk1 and Erk2) in a dose-dependent manner as was phosphorylation of MAP kinase induced by both interleukin 3 (IL-3) and GM-CSF in HL-60 cells. In 293T cells transfected with alpha and beta GM-CSF receptor subunits (αGMR and βGMR), GM-CSF–induced phosphorylation of βGMR and Jak-2 activation was suppressed by vitamin C loading. GM-CSF–mediated transcriptional activation of a luciferase reporter construct containing STAT-binding sites was also inhibited by vitamin C. These results substantiate the importance of ROS in GM-CSF signaling and indicate a role for vitamin C in downmodulating GM-CSF signaling responses. Our findings point to vitamin C as a regulator of cytokine redox-signal transduction in host defense cells and a possible role in controlling inflammatory responses.

scholarly journals Growth and differentiation of a human megakaryoblastic cell line, CMK

Blood ◽  
1989 ◽  
Vol 74 (1) ◽  
pp. 42-48 ◽  
Author(s):  
N Komatsu ◽  
T Suda ◽  
M Moroi ◽  
N Tokuyama ◽  
Y Sakata ◽  
...  
Keyword(s):  
Cell Line ◽  
Colony Formation ◽  
Culture System ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Hematopoietic Factors ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract Recently, a human megakaryoblastic cell line, CMK, was established from the peripheral blood of a megakaryoblastic leukemia patient with Down syndrome. Using this cell line, we studied the proliferation and differentiation of megakaryocytic cells in the presence of highly purified human hematopoietic factors and phorbol 12-myristate-13- acetate (PMA). In a methylcellulose culture system, interleukin-3 (IL- 3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) facilitated colony formation by CMK cells in a dose-dependent manner. The maximum stimulating doses of these factors were 10 and 200 U/mL, respectively. These concentrations were comparable to those that stimulate activity in normal hematopoietic cells. In contrast, granulocyte-colony stimulating factor (G-CSF), macrophage-colony stimulating factor (M-CSF), and erythropoietin (EPO) had no effects on the colony formation of CMK cells. In a liquid culture system, 20% of the CMK cells expressed glycoprotein IIb/IIIa (GPIIb/IIIa) antigen without hematopoietic factors, whereas 40% of the cells expressed GPIIb/IIIa with the addition of IL-3 and GM-CSF. EPO also slightly enhanced expression of GPIIb/IIIa. On the other hand, PMA inhibited growth of CMK cells and induced most of them to express the GPIIb/IIIa antigen. Furthermore, PMA induced CMK cells to produce growth activity toward new inocula of CMK cells. This growth factor (GF) contained colony-stimulating activity (CSA) in normal bone marrow (BM) cells. The activity was believed to be attributable mainly to GM-CSF, since 64% of this activity was neutralized by anti-GM-CSF antibodies and a transcript of GM-CSF was detected in mRNA from PMA-treated CMK cells by Northern blot analysis. These observations suggest that GM-CSF, as well as IL-3, should play an important role in megakaryocytopoiesis.

scholarly journals Hematopoietic and Lymphopoietic Responses in Human Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF ) Receptor Transgenic Mice Injected With Human GM-CSF

Blood ◽  
1997 ◽  
Vol 90 (3) ◽  
pp. 1031-1038 ◽  
Author(s):  
I. Nishijima ◽  
T. Nakahata ◽  
S. Watanabe ◽  
K. Tsuji ◽  
I. Tanaka ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Blood Cells ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Dose Dependent ◽  
Stimulating Factor

Abstract Using a clonal assay of bone marrow (BM) cells from transgenic mice (Tg-mice) expressing the human granulocyte-macrophage colony-stimulating factor receptor (hGM-CSFR), we found in earlier studies that hGM-CSF alone supported the development not only of granulocyte-macrophage colonies, but also of erythrocytes, megakaryocytes, mast cells, blast cells, and mixed hematopoietic colonies. In this report, we evaluated the in vivo effects of hGM-CSF on hematopoietic and lymphopoietic responses in the hGM-CSFR Tg-mice. Administration of this factor to Tg-mice resulted in dose-dependent increases in numbers of reticulocytes and white blood cells (WBCs) in the peripheral blood. Morphological analysis of WBCs showed that the numbers of all types of the cell, including neutrophils, eosinophils, monocytes, and lymphocytes increased; the most remarkable being in lymphocytes that contained a number of large granular lymphocytes (LGLs) in addition to mature T and B cells. However, total cellularity of the BM of the Tg-mice decreased in a dose-dependent manner when hGM-CSF was injected. In sharp contrast to the BM, spleens of the Tg-mice were grossly enlarged. Although all types of blood cells and hematopoietic progenitors increased in the spleen, erythroid cells and their progenitors showed the most significant increase. Increased numbers of megakaryocytes and LGLs were also observed in spleen and liver of the treated Tg-mice. Flow cytometric analysis showed that LGLs expanded in Tg-mice expressed Mac-1+CD3−NK1.1+. The thymus of Tg-mice treated with hGM-CSF exhibited a dose-dependent shrinkage and a remarkable decrease in CD4+CD8+ cells. Thus, hGM-CSF stimulated not only myelopoiesis but also erythropoiesis and megakaryopoiesis of hGM-CSFR Tg-mice in vivo, in accordance with our reported in vitro findings. In addition, hGM-CSF affected the development of lymphoid cells, including natural killer cells of these Tg-mice.

scholarly journals Granulocyte-macrophage colony-stimulating factor, interleukin-3, and steel factor induce rapid tyrosine phosphorylation of p42 and p44 MAP kinase

Blood ◽  
1992 ◽  
Vol 79 (11) ◽  
pp. 2880-2887 ◽  
Author(s):  
K Okuda ◽  
JS Sanghera ◽  
SL Pelech ◽  
Y Kanakura ◽  
M Hallek ◽  
...  
Keyword(s):  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Colony Stimulating Factor ◽  
Steel Factor ◽  
Interleukin 3 ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Tyrosyl Phosphorylation ◽  
Stimulating Factor

Abstract Granulocyte-macrophage colony-stimulating factor (GM-CSF), Interleukin- 3 (IL-3), and Steel Factor (SF) induce proliferation of hematopoietic cells through binding to specific, high-affinity, cell surface receptors. However, little is known about postreceptor signal transduction pathways. In previous studies, we noted that each of these three factors could independently support proliferation of the human MO7 cell line, and also that each factor induced a rapid increase in protein-tyrosyl phosphorylation. Although the proteins phosphorylated on tyrosine by GM-CSF and IL-3 are similar or identical in MO7 cells, many of the proteins that are phosphorylated on tyrosine after SF are different. However, two proteins, p42 and p44, were prominently phosphorylated in response to all three of the factors. In MO7 cells, the tyrosyl phosphorylation of p42 and p44 was transient, peaking at 5 to 15 minutes. In contrast to many of the other proteins which are tyrosyl phosphorylated in response to these factors, phosphorylation of p42 and p44 was temperature-dependent, occurring at 37 degrees C, but not at 4 degrees C. We identified the p42 protein as p42 Mitogen- Activated Protein Kinase (p42mapk, ERK-2) and the p44 as a p42mapk- related protein using monospecific antisera to MAP kinase. GM-CSF, IL- 3, and SF were each found to induce MAP kinase activity when assayed in vitro using myelin basic protein (MBP) as a substrate. Remarkably, we found that GM-CSF-induced tyrosyl phosphorylation of p42 and p44 even in nonproliferative cells (neutrophils) that respond to this CSF, and that p42 and p44 were two of the most prominently tyrosyl phosphorylated proteins following GM-CSF stimulation of these cells. These results implicate p42mapk and p44 as important signal transducing molecules in myeloid cells, and it is likely that these kinases play a role as part of a sequential “kinase cascade” linking growth factor receptors to mitogenesis and other cellular responses.

scholarly journals Hematopoietic and Lymphopoietic Responses in Human Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF ) Receptor Transgenic Mice Injected With Human GM-CSF

Blood ◽  
1997 ◽  
Vol 90 (3) ◽  
pp. 1031-1038 ◽  
Author(s):  
I. Nishijima ◽  
T. Nakahata ◽  
S. Watanabe ◽  
K. Tsuji ◽  
I. Tanaka ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Blood Cells ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Dose Dependent ◽  
Stimulating Factor

Using a clonal assay of bone marrow (BM) cells from transgenic mice (Tg-mice) expressing the human granulocyte-macrophage colony-stimulating factor receptor (hGM-CSFR), we found in earlier studies that hGM-CSF alone supported the development not only of granulocyte-macrophage colonies, but also of erythrocytes, megakaryocytes, mast cells, blast cells, and mixed hematopoietic colonies. In this report, we evaluated the in vivo effects of hGM-CSF on hematopoietic and lymphopoietic responses in the hGM-CSFR Tg-mice. Administration of this factor to Tg-mice resulted in dose-dependent increases in numbers of reticulocytes and white blood cells (WBCs) in the peripheral blood. Morphological analysis of WBCs showed that the numbers of all types of the cell, including neutrophils, eosinophils, monocytes, and lymphocytes increased; the most remarkable being in lymphocytes that contained a number of large granular lymphocytes (LGLs) in addition to mature T and B cells. However, total cellularity of the BM of the Tg-mice decreased in a dose-dependent manner when hGM-CSF was injected. In sharp contrast to the BM, spleens of the Tg-mice were grossly enlarged. Although all types of blood cells and hematopoietic progenitors increased in the spleen, erythroid cells and their progenitors showed the most significant increase. Increased numbers of megakaryocytes and LGLs were also observed in spleen and liver of the treated Tg-mice. Flow cytometric analysis showed that LGLs expanded in Tg-mice expressed Mac-1+CD3−NK1.1+. The thymus of Tg-mice treated with hGM-CSF exhibited a dose-dependent shrinkage and a remarkable decrease in CD4+CD8+ cells. Thus, hGM-CSF stimulated not only myelopoiesis but also erythropoiesis and megakaryopoiesis of hGM-CSFR Tg-mice in vivo, in accordance with our reported in vitro findings. In addition, hGM-CSF affected the development of lymphoid cells, including natural killer cells of these Tg-mice.

Down-regulation of interleukin-3/granulocyte-macrophage colony-stimulating factor receptor β-chain in BCR-ABL+human leukemic cells: association with loss of cytokine-mediated Stat-5 activation and protection from apoptosis after BCR-ABL inhibition

Blood ◽  
2001 ◽  
Vol 97 (9) ◽  
pp. 2846-2853 ◽  
Author(s):  
Nicholas J. Donato ◽  
Ji Y. Wu ◽  
Ling Zhang ◽  
Hagop Kantarjian ◽  
Moshe Talpaz
Keyword(s):  
Map Kinase ◽  
Leukemic Cells ◽  
Signaling Cascades ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Sti 571 ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Β Chain ◽  
Stimulating Factor

Abstract Several signaling cascades are engaged by expression of the p210 bcr-abl tyrosine kinase, and evidence suggests that these signals drive leukemogenesis. In this report, signaling pathways were examined and compared between cells derived from leukemic patients and cells expressing a bcr-abl construct (MBA). The effects of acute inhibition of bcr-abl with STI-571 on these signals and the survival of bcr-abl–expressing cells were also evaluated. Expression of bcr-abl in interleukin-3 (IL-3)/granulocyte-macrophage colony-stimulating factor (GM-CSF)–dependent Mo7e cells (MBA) resulted in growth factor independence, constitutive activation of Stat-5 phosphorylation, engagement of mitogen-activated protein (MAP) kinase signals, and increased expression of PTP1B and bcl-xL. STI-571 inhibited cell growth and induced apoptosis in bcr-abl–expressing cells (MBA, K562, BV-173, KBM5) but not in bcr-abl− tumor cells (Mo7e, KG-1, ME-180, Daudi). STI-571–mediated apoptosis correlated with the inhibition of Stat-5 and MAP kinase activation and a reduction in overexpressed bcl-xL but not in PTP1B. Inhibitor had no effect on IL-3/GM-CSF–dependent Mo7e cell signaling and did not prevent activation of the other Jak/Stat pathways (interferon α, IL-3/GM-CSF). However, neither IL-3 nor GM-CSF could reactivate Stat-5 after the STI-571–mediated inhibition of bcr-abl. Expression of the common β-chain of the IL-3/GM-CSF receptor was down-regulated in Stat-5–activated myeloid leukemic cells, suppressing IL-3/GM-CSF signal transduction and the ability of these cytokines to provide apoptotic protection. These studies suggest that bcr-abl activates cytokine-independent mechanisms of survival while inactivating intrinsic cytokine signaling cascades, making bcr-abl+myeloid cells vulnerable to apoptosis after bcr-abl inactivation.

scholarly journals Susceptibility of monocytes to lymphokine-activated killer cell lysis: effect of granulocyte-macrophage colony-stimulating factor and interleukin-3

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1264-1271 ◽  
Author(s):  
JY Djeu ◽  
R Widen ◽  
DK Blanchard
Keyword(s):  
Killer Cell ◽  
Sodium Dodecyl ◽  
Lak Cells ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Interleukin 3 ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract Cultured human monocytes have been shown to be susceptible to lysis by autologous lymphokine-activated killer (LAK) cells. To determine factors that might modulate the sensitivity of monocytes to lysis, we cultured adherent peripheral blood leukocytes (PBL) in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) since these cytokines have been reported to affect both functional and physical characteristics of monocytes. Both recombinant human GM-CSF and IL-3 were found to significantly enhance the susceptibility of monocytes to lysis by LAK cells in a dose- dependent manner, with GM-CSF being slightly more effective. In a kinetics study, the lysability of monocytes increased after two days of incubation with either cytokine, with maximal susceptibility occurring after four to six days of culture. The effects of GM-CSF and IL-3 appeared to be specific for monocytes since culture of either nonadherent cells or granulocytes, which are normally resistant to LAK- mediated lysis, did not induce sensitivity. While the effects of GM-CSF and IL-3 have been shown to be synergistic in some cases, they did not act synergistically to induce monocyte susceptibility to LAK lysis. In cold target experiments cytokine-treated monocytes reciprocally blocked lysis, suggesting that similar target structures were modulated with either factor. FACS analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated comparable modulation of surface antigens with either GM-CSF or IL-3. Thus, these cytokines can serve to augment susceptibility of monocytes to LAK cells, emphasizing the complex interactions that occur in the immune system.

scholarly journals Granulocyte/macrophage colony-stimulating factor stimulates the expression of the 5-lipoxygenase-activating protein (FLAP) in human neutrophils.

1994 ◽  
Vol 179 (4) ◽  
pp. 1225-1232 ◽  
Author(s):  
M Pouliot ◽  
P P McDonald ◽  
P Borgeat ◽  
S R McColl
Keyword(s):  
De Novo ◽  
Human Neutrophils ◽  
Protein Synthesis Inhibitor ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Synthesis Inhibitor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

The synthesis of leukotrienes in human blood neutrophils chiefly relies on the activity of two enzymes, phospholipase A2 and 5-lipoxygenase (5-LO). In turn, the activation of the 5-LO requires the participation of a recently characterized membrane-bound protein, the 5-LO-activating protein (FLAP). In this study, we have investigated conditions under which FLAP expression in neutrophils may be modulated. Of several cytokines tested, only granulocyte/macrophage colony-stimulating factor (GM-CSF) (and to a lesser extent tumor necrosis factor alpha) significantly increased expression of FLAP. GM-CSF increased FLAP mRNA steady-state levels in a time- and dose-dependent manner. The stimulatory effect of GM-CSF on FLAP mRNA was inhibited by prior treatment of the cells with the transcription inhibitor, actinomycin D, and pretreatment of the cells with the protein synthesis inhibitor, cycloheximide, failed to prevent the increase in FLAP mRNA induced by GM-CSF. The accumulation of newly synthesized FLAP, as determined by immunoprecipitation after incorporation of 35S-labeled amino acids, was also increased after incubation of neutrophils with GM-CSF. In addition, the total level of FLAP protein was increased in GM-CSF-treated neutrophils, as determined by two-dimensional gel electrophoresis, followed by Western blot. GM-CSF did not alter the stability of the FLAP protein, indicating that the effect of GM-CSF on FLAP accumulation was the consequence of increased de novo synthesis as opposed to decreased degradation of FLAP. Finally, incubation of neutrophils with the synthetic glucocorticoid dexamethasone directly stimulated the upregulation of FLAP mRNA and protein, and enhanced the effect of GM-CSF. Taken together, these data demonstrate that FLAP expression may be upmodulated after appropriate stimulation of neutrophils. The increase in FLAP expression induced by GM-CSF in inflammatory conditions could confer upon neutrophils a prolonged capacity to synthesize leukotrienes.

scholarly journals A Neuroprotective Function for the Hematopoietic Protein Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF)

2007 ◽  
Vol 28 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Wolf-Rüdiger Schäbitz ◽  
Carola Krüger ◽  
Claudia Pitzer ◽  
Daniela Weber ◽  
Rico Laage ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Experimental Stroke ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Human Neuroblastoma ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Hematopoietic Factors ◽  
Macrophage Colony ◽  
Stimulating Factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine responsible for the proliferation, differentiation, and maturation of cells of the myeloid lineage, which was cloned more than 20 years ago. Here we uncovered a novel function of GM-CSF in the central nervous system (CNS). We identified the GM-CSF α-receptor as an upregulated gene in a screen for ischemia-induced genes in the cortex. This receptor is broadly expressed on neurons throughout the brain together with its ligand and induced by ischemic insults. In primary cortical neurons and human neuroblastoma cells, GM-CSF counteracts programmed cell death and induces BCL-2 and BCL-Xl expression in a dose- and time-dependent manner. Of the signaling pathways studied, GM-CSF most prominently induced the PI3K-Akt pathway, and inhibition of Akt strongly decreased antiapoptotic activity. Intravenously given GM-CSF passes the blood—brain barrier, and decreases infarct damage in two different experimental stroke models (middle cerebral artery occlusion (MCAO), and combined common carotid/distal MCA occlusion) concomitant with induction of BCL-Xl expression. Thus, GM-CSF acts as a neuroprotective protein in the CNS. This finding is remarkably reminiscent of the recently discovered functionality of two other hematopoietic factors, erythropoietin and granulocyte colony-stimulating factor in the CNS. The identification of a third hematopoietic factor acting as a neurotrophic factor in the CNS suggests a common principle in the functional evolution of these factors. Clinically, GM-CSF now broadens the repertoire of hematopoietic factors available as novel drug candidates for stroke and neurodegenerative diseases.

scholarly journals Inhibition of proliferation and induction of apoptosis in juvenile myelomonocytic leukemic cells by the granulocyte-macrophage colony- stimulating factor analogue E21R

Blood ◽  
1996 ◽  
Vol 88 (7) ◽  
pp. 2634-2639 ◽  
Author(s):  
PO Iversen ◽  
RL Rodwell ◽  
L Pitcher ◽  
KM Taylor ◽  
AF Lopez
Keyword(s):  
Cell Survival ◽  
Receptor Antagonist ◽  
Interleukin 1 ◽  
Juvenile Myelomonocytic Leukemia ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Juvenile myelomonocytic leukemia (JMML) is a malignancy that almost inevitably leads to death before adulthood. Chemotherapy has given disappointing results and a substantial number of patients relapse after bone marrow transplantation. A salient feature of this disease is that the JMML cells produce granulocyte-macrophage colony-stimulating factor (GM-CSF) spontaneously and survive and proliferate without exogeneous GM-CSF. Furthermore, JMML cells are hypersensitive to GM-CSF with addition of this cytokine leading to enhanced proliferation. We have recently generated a human GM-CSF analogue, E21R, that acts as a complete and selective GM-CSF receptor antagonist. We have now tested this molecule as a potential new agent to control the leukemic cell load in JMML with particular emphasis on its role in JMML cell survival. We found that E21R inhibited the spontaneous growth of JMML cells in vitro and caused their apoptosis in a dose- and time-dependent manner in seven of seven cases. In contrast, neither a neutralizing anti-GM-CSF monoclonal antibody (MoAb) nor a selective interleukin-1 (IL-1) receptor antagonist affected JMML cell survival. Furthermore, the apoptotic effect of E21R was seen even in the presence of interleukin-1 beta and tumor necrosis factor-alpha, which have also been implicated in the pathogenesis of JMML. The inhibitory effects of E21R on JMML cell growth and viability offer a novel approach to therapy in this lethal childhood leukemia.

scholarly journals Susceptibility of monocytes to lymphokine-activated killer cell lysis: effect of granulocyte-macrophage colony-stimulating factor and interleukin-3

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1264-1271
Author(s):  
JY Djeu ◽  
R Widen ◽  
DK Blanchard
Keyword(s):  
Killer Cell ◽  
Sodium Dodecyl ◽  
Lak Cells ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Interleukin 3 ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Cultured human monocytes have been shown to be susceptible to lysis by autologous lymphokine-activated killer (LAK) cells. To determine factors that might modulate the sensitivity of monocytes to lysis, we cultured adherent peripheral blood leukocytes (PBL) in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) since these cytokines have been reported to affect both functional and physical characteristics of monocytes. Both recombinant human GM-CSF and IL-3 were found to significantly enhance the susceptibility of monocytes to lysis by LAK cells in a dose- dependent manner, with GM-CSF being slightly more effective. In a kinetics study, the lysability of monocytes increased after two days of incubation with either cytokine, with maximal susceptibility occurring after four to six days of culture. The effects of GM-CSF and IL-3 appeared to be specific for monocytes since culture of either nonadherent cells or granulocytes, which are normally resistant to LAK- mediated lysis, did not induce sensitivity. While the effects of GM-CSF and IL-3 have been shown to be synergistic in some cases, they did not act synergistically to induce monocyte susceptibility to LAK lysis. In cold target experiments cytokine-treated monocytes reciprocally blocked lysis, suggesting that similar target structures were modulated with either factor. FACS analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated comparable modulation of surface antigens with either GM-CSF or IL-3. Thus, these cytokines can serve to augment susceptibility of monocytes to LAK cells, emphasizing the complex interactions that occur in the immune system.

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