scholarly journals Differential and synergistic effects of human granulocyte-macrophage colony-stimulating factor and human granulocyte colony-stimulating factor on hematopoiesis in human long-term marrow cultures

Blood ◽  
1991 ◽  
Vol 77 (3) ◽  
pp. 493-499 ◽  
Author(s):  
DE Hogge ◽  
JD Cashman ◽  
RK Humphries ◽  
CJ Eaves
Keyword(s):  
Growth Factors ◽  
Synergistic Effects ◽  
S Phase ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Single Addition ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract The ability of granulocyte-macrophage colony-stimulating factor (GM- CSF) and G-CSF to influence hematopoiesis in long-term cultures (LTC) of human marrow was studied by cocultivating light density normal human marrow cells with human marrow fibroblast feeders engineered by retroviral infection to constitutively produce one of these growth factors. Feeders producing stable levels of 4 ng/mL GM-CSF or 20 ng/mL G-CSF doubled the output of mature nonadherent cells. The numbers of both colony forming unit-GM (CFU-GM) and erythroid burst forming unit (BFU-E) in the G-CSF LTC were also increased (twofold and fourfold, respectively, after 5 weeks in culture), but this effect was not seen with the GM-CSF feeders. At the time of the weekly half medium change 3H-thymidine suicide assays showed primitive adherent layer progenitors in LTC to be quiescent in both the control and GM-CSF cultures. In contrast, in the G-CSF cultures, a high proportion of primitive progenitors were in S-phase. A single addition of either recombinant GM- CSF or G-CSF to LTC in doses as high as 80 ng/mL and 150 ng/mL, respectively, failed to induce primitive progenitor cycling. However, three sequential daily additions of 150 ng/mL G-CSF did stimulate primitive progenitors to enter S-phase and a single addition of 5 or 12.5 ng/mL of G-CSF together with 10 ng/mL GM-CSF was able to elicit the same effect. Thus, selective elevation of G-CSF in human LTC stimulates proliferation of primitive clonogenic progenitors, which may then proceed through to the terminal stages of granulopoiesis. In contrast, the effects of GM-CSF in this system appear limited to terminally differentiating granulopoietic cells. However, when both GM- CSF and G-CSF are provided together, otherwise biologically inactive doses show strong stimulatory activity. These findings suggest that the production of both of these growth factors by normal stromal cells may contribute to the support and proliferation of hematopoietic cells, not only in LTC, but also in the microenvironment of the marrow in vivo.

scholarly journals Differential and synergistic effects of human granulocyte-macrophage colony-stimulating factor and human granulocyte colony-stimulating factor on hematopoiesis in human long-term marrow cultures

Blood ◽  
1991 ◽  
Vol 77 (3) ◽  
pp. 493-499 ◽  
Author(s):  
DE Hogge ◽  
JD Cashman ◽  
RK Humphries ◽  
CJ Eaves
Keyword(s):  
Growth Factors ◽  
Synergistic Effects ◽  
S Phase ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Single Addition ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

The ability of granulocyte-macrophage colony-stimulating factor (GM- CSF) and G-CSF to influence hematopoiesis in long-term cultures (LTC) of human marrow was studied by cocultivating light density normal human marrow cells with human marrow fibroblast feeders engineered by retroviral infection to constitutively produce one of these growth factors. Feeders producing stable levels of 4 ng/mL GM-CSF or 20 ng/mL G-CSF doubled the output of mature nonadherent cells. The numbers of both colony forming unit-GM (CFU-GM) and erythroid burst forming unit (BFU-E) in the G-CSF LTC were also increased (twofold and fourfold, respectively, after 5 weeks in culture), but this effect was not seen with the GM-CSF feeders. At the time of the weekly half medium change 3H-thymidine suicide assays showed primitive adherent layer progenitors in LTC to be quiescent in both the control and GM-CSF cultures. In contrast, in the G-CSF cultures, a high proportion of primitive progenitors were in S-phase. A single addition of either recombinant GM- CSF or G-CSF to LTC in doses as high as 80 ng/mL and 150 ng/mL, respectively, failed to induce primitive progenitor cycling. However, three sequential daily additions of 150 ng/mL G-CSF did stimulate primitive progenitors to enter S-phase and a single addition of 5 or 12.5 ng/mL of G-CSF together with 10 ng/mL GM-CSF was able to elicit the same effect. Thus, selective elevation of G-CSF in human LTC stimulates proliferation of primitive clonogenic progenitors, which may then proceed through to the terminal stages of granulopoiesis. In contrast, the effects of GM-CSF in this system appear limited to terminally differentiating granulopoietic cells. However, when both GM- CSF and G-CSF are provided together, otherwise biologically inactive doses show strong stimulatory activity. These findings suggest that the production of both of these growth factors by normal stromal cells may contribute to the support and proliferation of hematopoietic cells, not only in LTC, but also in the microenvironment of the marrow in vivo.

scholarly journals A comparison of treatment of canine cyclic hematopoiesis with recombinant human granulocyte-macrophage colony-stimulating factor (GM- CSF), G-CSF interleukin-3, and canine G-CSF

Blood ◽  
1990 ◽  
Vol 76 (3) ◽  
pp. 523-532 ◽  
Author(s):  
WP Hammond ◽  
TC Boone ◽  
RE Donahue ◽  
LM Souza ◽  
DC Dale
Keyword(s):  
Bone Marrow ◽  
Growth Factors ◽  
Colony Stimulating Factor ◽  
Interleukin 3 ◽  
Gm Csf ◽  
Cell Counts ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Cyclic Hematopoiesis ◽  
Stimulating Factor

Cyclic hematopoiesis in gray collie dogs is a stem cell disease in which abnormal regulation of cell production in the bone marrow causes cyclic fluctuations of blood cell counts. In vitro studies demonstrated that recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and granulocyte colony stimulating factor (G-CSF) all stimulated increases in colony formation by canine bone marrow progenitor cells. Based on these results, gray collie dogs were then treated with recombinant human (rh) GM-CSF, IL-3, or G-CSF subcutaneously to test the hypothesis that pharmacologic doses of one of these hematopoietic growth factors could alter cyclic production of cells. When recombinant canine G-CSF became available, it was tested over a range of doses. In vivo rhIL-3 had no effect on the recurrent neutropenia but was associated with eosinophilia, rhGM-CSF caused neutrophilia and eosinophilia but cycling of hematopoiesis persisted. However, rhG-CSF caused neutrophilia, prevented the recurrent neutropenia and, in the two animals not developing antibodies to rhG- CSF, obliterated periodic fluctuation of monocyte, eosinophil, reticulocyte, and platelet counts. Recombinant canine G-CSF increased the nadir neutrophil counts and amplitude of fluctuations at low doses (1 micrograms/kg/d) and eliminated all cycling of cell counts at high doses (5 and 10 micrograms/kg/d). These data suggest significant differences in the actions of these growth factors and imply a critical role for G-CSF in the homeostatic regulation of hematopoiesis.

scholarly journals Effects of granulocyte-macrophage colony-stimulating factor and erythropoietin on leukemic erythroid colony formation in human early erythroblastic leukemias

Blood ◽  
1987 ◽  
Vol 70 (4) ◽  
pp. 965-973 ◽  
Author(s):  
MT Mitjavila ◽  
JL Villeval ◽  
P Cramer ◽  
A Henri ◽  
J Gasson ◽  
...  
Keyword(s):  
Growth Factors ◽  
Plating Efficiency ◽  
Colony Stimulating Factor ◽  
Hematopoietic Growth Factors ◽  
Erythroid Progenitors ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor ◽  
Autonomous Growth

Abstract Erythroid colonies from five patients with an early erythroblastic leukemia were obtained in “serum-free” cultures in the presence or absence of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) and homogeneous native erythropoietin (Epo). Erythroid colonies with abnormal morphology and karyotype could be grown in different culture conditions. Their erythroid nature was ascertained by the presence of carbonic anhydrase I and glycophorin A. Leukemic erythroid progenitors strongly differed from normal progenitors in that spontaneous colonies were always obtained, sometimes with an extremely high plating efficiency (up to 5.7%). Colonies were found to be autonomous from exogenous hematopoietic growth factors because they were still obtained with a high plating efficiency at an average of one cell per culture in the absence of any added growth factor. No evidence for an autocrine secretion of Epo or GM-CSF emerged because Epo or GM- CSF could not be detected by biologic or radioimmunologic assays from the culture supernatant or cellular extracts of the leukemic cells and that Epo or GM-CSF antibodies did not block autonomous growth. In all cases, however, hematopoietic growth factors increased the plating efficiency of the abnormal erythroid progenitors. In the two “de novo” leukemias, leukemic erythroid progenitors responded primarily to Epo, whereas in the three other patients' (chronic myeloid leukemia) blast crisis they responded maximally to GM-CSF plus Epo. Recombinant erythroid-potentiating activity had no effect in any of these cases. These results suggest that the leukemic erythroid clonogenic cells arise from expansion of erythroid progenitors at different levels of differentiation (ie, CFU-E or BFU-E, depending upon the disease) and that autonomous growth is not related to a secretion of Epo or GM-CSF.

scholarly journals Granulocyte-macrophage colony-stimulating factor (GM-CSF) in human long- term bone marrow cultures: endogenous production in the adherent layer and effect of exogenous GM-CSF on granulomonopoiesis

Blood ◽  
1991 ◽  
Vol 78 (5) ◽  
pp. 1230-1236 ◽  
Author(s):  
P Charbord ◽  
E Tamayo ◽  
S Saeland ◽  
V Duvert ◽  
J Poulet ◽  
...  
Keyword(s):  
Stromal Cells ◽  
Culture Medium ◽  
Neutralizing Antibody ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Bone Marrow Cultures ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract This study was designed to assess the presence of endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) within adherent layers of human Dexter-type cultures and to investigate the effect on granulomonopoiesis of adding exogenous GM-CSF to the culture medium. The presence of GM-CSF was demonstrated using a bioassay, in which adherent layers from normal bone marrows gave rise to endogenous granulocyte-macrophage colony-forming units (CFU-GM) that were specifically inhibited by increasing amounts of an anti-GM-CSF neutralizing antibody. Using an immunoassay, the estimated amounts of GM-CSF were less than or equal to 40 pg per flask in adherent layers, while remaining undetectable in supernatants. The addition of 10 ng or purified recombinant GM-CSF per milliliter of culture medium increased slightly the CFU-GM output over a 5-week culture period. The addition of 50 ng/mL decreased significantly the CFU-GM output after 5 weeks of culture. This decrease was associated with major modifications of the adherent layer cell composition. Large round or ovoid macrophages were generated at the expense of the interdigitated and elongated stromal cells and the extracellular fibronectin network was no longer observed. These studies suggest that GM-CSF production by accessory cells (stromal cells and/or monocytes) is almost equal to its consumption by hematopoietic cells, a situation similar to that found in long-term cultures of murine marrows. They also show that the maintenance of granulomonopoiesis is decreased by adding more than 10 ng/mL of exogenous GM-CSF to the culture medium, which is related to the induction of adherent macrophages, the disappearance of the major smooth-muscle-like stromal cell component of the adherent layer, and that of the fibronectin extracellular matrix.

scholarly journals Flt3 Ligand Synergizes With Granulocyte-Macrophage Colony-Stimulating Factor or Granulocyte Colony-Stimulating Factor to Mobilize Hematopoietic Progenitor Cells Into the Peripheral Blood of Mice

Blood ◽  
1997 ◽  
Vol 90 (9) ◽  
pp. 3781-3788 ◽  
Author(s):  
Kenneth Brasel ◽  
Hilary J. McKenna ◽  
Keith Charrier ◽  
Phillip J. Morrissey ◽  
Douglas E. Williams ◽  
...  
Keyword(s):  
Growth Factors ◽  
Peripheral Blood ◽  
Granulocyte Colony Stimulating Factor ◽  
Colony Stimulating Factor ◽  
Flt3 Ligand ◽  
Gm Csf ◽  
Colony Forming Unit ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract Peripheral blood progenitor cells (PBPC) are increasingly being used in the clinic as a replacement for bone marrow (BM) in the transplantation setting. We investigated the capacity of several different growth factors, including human flt3 ligand (FL), alone and in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF ) or granulocyte colony-stimulating factor (G-CSF ), to mobilize colony forming cells (CFU) into the peripheral blood (PB) of mice. Mice were injected subcutaneously (SC) with growth factors daily for up to 10 days. Comparing the single agents, we found that FL alone was superior to GM-CSF or G-CSF in mobilizing CFU into the PB. FL synergized with both GM-CSF or G-CSF to mobilize more CFU, and in a shorter period of time, than did any single agent. Administration of FL plus G-CSF for 6 days resulted in a 1,423-fold and 2,717-fold increase of colony-forming unit–granulocyte-macrophage (CFU-GM) and colony-forming unit granulocyte, erythroid, monocyte, megakaryocyte (CFU-GEMM) in PB, respectively, when compared with control mice. We also followed the kinetics of CFU numerical changes in the BM of mice treated with growth factors. While GM-CSF and G-CSF alone had little effect on BM CFU over time, FL alone increased CFU-GM and CFU-GEMM threefold and fivefold, respectively. Addition of GM-CSF or G-CSF to FL did not increase CFU in BM over levels seen with FL alone. However, after the initial increase in BM CFU after FL plus G-CSF treatment for 3 days, BM CFU returned to control levels after 5 days treatment, and CFU-GM were significantly reduced (65%) after 7 days treatment, when compared with control mice. Finally, we found that transplantation of FL or FL plus G-CSF–mobilized PB cells protected lethally irradiated mice and resulted in long-term multilineage hematopoietic reconstitution.

scholarly journals Granulocyte-macrophage colony-stimulating factor and erythropoietin act competitively to induce two different programs of differentiation in the human pluripotent cell line UT-7

Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3060-3069 ◽  
Author(s):  
O Hermine ◽  
P Mayeux ◽  
M Titeux ◽  
MT Mitjavila ◽  
N Casadevall ◽  
...  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Line ◽  
Messenger Rna ◽  
Colony Stimulating Factor ◽  
Pluripotent Cell ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract The UT-7 cell line was established from a patient with a megakaryoblastic leukemia (Komatsu et al, Cancer Res 51: 341, 1991). Its proliferation is strictly dependent on the presence of hematopoietic growth factors including erythropoietin (Epo), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3). We investigated the differentiation capacities of this cell line under the action of several growth factors, using immunomarkers, flow cytometry, and ultrastructural techniques. In the presence of GM-CSF and IL-3, eosinophil and basophil promyelocytes were detected, as well as a few cells with erythroid and megakaryocytic (MK) differentiation features. In contrast, Epo induced a marked erythroid differentiation with an increase of glycophorin A expression, accompanied by a few hemoglobinized cells. Differentiation induced by the growth factors took 24 to 48 hours to begin, and increased with cell passages to a plateau at 2 weeks of culture. However, this was not only due to a cell selection because the differential effects of Epo and GM-CSF were observed from a single cell clone and the phenotype could be reversed by opposite growth factors, even after a long period of culture. We subsequently investigated the phenotype of UT-7 in the presence of combinations of Epo, IL-3, and GM-CSF, and showed that GM-CSF and IL-3 act predominantly over Epo. This effect was mediated by a rapid downmodulation of Epo receptors by GM-CSF at messenger RNA and binding sites levels, without a change in receptor affinities. On the other hand, Epo had no effect on number and affinity of GM-CSF receptors. This study shows that UT-7 is a growth factor-dependent pluripotent cell line in which commitment may be directed by a hierarchical action of growth factors through an early and rapid transmodulation of growth factor receptors.

scholarly journals Granulocyte-macrophage colony-stimulating factor and erythropoietin act competitively to induce two different programs of differentiation in the human pluripotent cell line UT-7

Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3060-3069 ◽  
Author(s):  
O Hermine ◽  
P Mayeux ◽  
M Titeux ◽  
MT Mitjavila ◽  
N Casadevall ◽  
...  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Line ◽  
Messenger Rna ◽  
Colony Stimulating Factor ◽  
Pluripotent Cell ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

The UT-7 cell line was established from a patient with a megakaryoblastic leukemia (Komatsu et al, Cancer Res 51: 341, 1991). Its proliferation is strictly dependent on the presence of hematopoietic growth factors including erythropoietin (Epo), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3). We investigated the differentiation capacities of this cell line under the action of several growth factors, using immunomarkers, flow cytometry, and ultrastructural techniques. In the presence of GM-CSF and IL-3, eosinophil and basophil promyelocytes were detected, as well as a few cells with erythroid and megakaryocytic (MK) differentiation features. In contrast, Epo induced a marked erythroid differentiation with an increase of glycophorin A expression, accompanied by a few hemoglobinized cells. Differentiation induced by the growth factors took 24 to 48 hours to begin, and increased with cell passages to a plateau at 2 weeks of culture. However, this was not only due to a cell selection because the differential effects of Epo and GM-CSF were observed from a single cell clone and the phenotype could be reversed by opposite growth factors, even after a long period of culture. We subsequently investigated the phenotype of UT-7 in the presence of combinations of Epo, IL-3, and GM-CSF, and showed that GM-CSF and IL-3 act predominantly over Epo. This effect was mediated by a rapid downmodulation of Epo receptors by GM-CSF at messenger RNA and binding sites levels, without a change in receptor affinities. On the other hand, Epo had no effect on number and affinity of GM-CSF receptors. This study shows that UT-7 is a growth factor-dependent pluripotent cell line in which commitment may be directed by a hierarchical action of growth factors through an early and rapid transmodulation of growth factor receptors.

scholarly journals Rapid priming of human monocytes by human hematopoietic growth factors: granulocyte-macrophage colony-stimulating factor (CSF), macrophage-CSF, and interleukin-3 selectively enhance superoxide release triggered by receptor-mediated agonists

Blood ◽  
1992 ◽  
Vol 79 (6) ◽  
pp. 1553-1557 ◽  
Author(s):  
A Yuo ◽  
S Kitagawa ◽  
K Motoyoshi ◽  
E Azuma ◽  
M Saito ◽  
...  
Keyword(s):  
Growth Factors ◽  
Human Monocytes ◽  
Colony Stimulating Factor ◽  
Hematopoietic Growth Factors ◽  
Con A ◽  
Interleukin 3 ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract The effects of hematopoietic growth factors on human monocyte superoxide (O2-) release were investigated by using purified human monocytes in suspension. Among growth factors studied, granulocyte- macrophage colony-stimulating factor (GM-CSF), macrophage-CSF (M-CSF), and interleukin-3 (IL-3) primed human monocytes and enhanced O2- release stimulated by the receptor-mediated agonists, N-formyl- methionyl-leucyl-phenylalanine (FMLP) and concanavalin A (Con A), but not by phorbol myristate acetate, which bypasses the receptors to stimulate the cells. The optimal priming was obtained by pretreatment of cells with 1 to 5 ng/mL (0.07 to 0.34 nmol/L) GM-CSF, 50 to 100 ng/mL (0.5 to 1.1 nmol/L) M-CSF, or 10 to 20 ng/mL (0.6 to 1.3 nmol/L) IL-3 for 10 minutes at 37 degrees C. Potency of the maximal priming effects on FMLP- or Con A-induced O2- release was GM-CSF greater than M- CSF = IL-3. The combination of the optimal concentrations of any two CSFs resulted in the effect of more potent priming agent alone. Enhancement of O2- release by GM-CSF was observed over the complete range of effective concentrations of FMLP (10(-8) to 10(-6) mol/L). The pretreatment of monocytes with granulocyte-CSF (50 ng/mL), interferon- gamma (1,000 U/mL), or IL-4 (20 ng/mL) for 10 minutes at 37 degrees C had no effect on O2- release stimulated by FMLP or Con A. These findings show that GM-CSF, M-CSF, and IL-3 selectively enhance O2- release in human monocytes triggered by receptor-mediated agonists after short-term preincubation.

scholarly journals The effects of three recombinant growth factors, IL-3, GM-CSF, and G- CSF, on the blast cells of acute myeloblastic leukemia maintained in short-term suspension culture

Blood ◽  
1987 ◽  
Vol 70 (3) ◽  
pp. 657-663 ◽  
Author(s):  
J Miyauchi ◽  
CA Kelleher ◽  
YC Yang ◽  
GG Wong ◽  
SC Clark ◽  
...  
Keyword(s):  
Growth Factors ◽  
Acute Myeloblastic Leukemia ◽  
Colony Stimulating Factor ◽  
Short Term ◽  
Gm Csf ◽  
Bladder Cell ◽  
Blast Cells ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract The blast stem cells of acute myeloblastic leukemia (AML) respond in cell culture to growth factors by both self-renewal and terminal divisions. Both of these functions have been shown to be stimulated by the recombinant growth factors granulocyte-macrophage colony- stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF). In this paper, recombinant gibbon interleukin-3 (IL-3), homologous to human IL-3, was tested on blast cells and compared with the effects of GM-CSF, G-CSF, and medium conditioned by the bladder cell line 5637 (5637-CM). We found that IL-3 was an effective stimulator of blast renewal and terminal divisions. However, great patient-to-patient variation was found. A graphic method of presenting complex comparisons between growth factors is also included.

Localisation of granulocyte macrophage colony-stimulating factor in human long-term bone marrow cultures. Biological and immunocytochemical characterisation

1993 ◽  
Vol 106 (3) ◽  
pp. 761-769
Author(s):  
E. de Wynter ◽  
T. Allen ◽  
L. Coutinho ◽  
D. Flavell ◽  
S.U. Flavell ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Bone Marrow Cultures ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor ◽  
Marrow Cultures

The distribution of granulocyte macrophage colony-stimulating factor (GM-CSF) in human long-term bone marrow cultures (HLTBMC) was examined using two monoclonal antibodies raised using purified recombinant GM-CSF and a third commercially available GM-CSF antibody. The antibodies were able to bind to purified recombinant GM-CSF and showed inhibition of GM-CFC colonies in the presence of both recombinant and native protein. All antibodies displayed similar patterns of distribution in both permeabilised and non-permeabilised stromal cell preparations. Fibroblasts were labelled at their periphery in early cultures and both endothelial cells and fibroblasts showed cytoplasmic labelling with anti-GM-CSF. The fact that GM-CSF appears to be sequestered by cells of the bone marrow stroma raises the possibility that it is synthesized by these cells and may regulate activity of the progenitor cells in the haemopoietic foci. In contrast, early progenitor cells within the foci did not stain with any of the anti-GM-CSF antibodies. Adipocytes, which differentiate from fibroblasts in these cultures, showed a diffuse staining pattern. Two types of macrophage staining were observed in the non-permeabilised cells; those exhibiting only autofluorescence and those that bound the antibody. Intracellular staining was apparent in a small sub-population. Generally, the staining persisted up to eight weeks of culture and thereafter declined, becoming virtually undetectable after 12 weeks. This correlates with the pattern of GM-CFC production in long-term bone marrow cultures.

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