Action of interleukin-3, G-CSF, and GM-CSF on highly enriched human hematopoietic progenitor cells: synergistic interaction of GM-CSF plus G-CSF

Purified preparations of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF), and interleukin 3 (IL-3 or multi-CSF) alone and in combination, have been compared for their stimulatory effects on human granulocyte-macrophage colony forming cells (GM-CFC). In cultures of unseparated normal human bone marrow, the combinations of G-CSF plus IL-3 and GM-CSF plus IL-3 stimulated additive numbers of GM colonies, while GM-CSF plus G-CSF stimulated greater than additive numbers of GM colonies, compared with the sum of the colony formation obtained with each factor alone. Cultures of unseparated bone marrow, harvested from patients four to six days after administration of 5-fluorouracil (5-FU), resulted in additive GM colony formation with GM-CSF plus G-CSF, GM-CSF plus IL-3, and G-CSF plus IL-3. In order to address the possibility of secondary factor involvement in the synergistic interaction of GM-CSF and G-CSF, CD33+/CD34+ colony forming cells were separated from normal and post FU marrow by two color fluorescence activated cell sorting. In cultures of CD33+/CD34+ cells the combination of GM-CSF plus G-CSF stimulated a synergistic increase in GM colonies while GM-CSF plus IL-3 stimulated additive numbers of colonies. These results suggest that GM-CSF, G-CSF, and IL-3 stimulate distinct populations of GM-CFC. Furthermore GM-CSF and G-CSF interact synergistically and this action is a direct effect on progenitor cells not stimulated by GM-CSF or G-CSF alone.     

Recombinant human stem cell factor enhances the formation of colonies by CD34+ and CD34+lin- cells, and the generation of colony-forming cell progeny from CD34+lin- cells cultured with interleukin-3, granulocyte colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor.

We tested the ability of recombinant human stem cell factor (SCF) to stimulate isolated marrow precursor cells to form colonies in semisolid media and to generate colony-forming cells (CFC) in liquid culture. SCF, in combination with interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte colony-stimulating factor (G-CSF) caused CD34+ cells to form increased numbers of granulocyte-macrophage colonies (CFU-GM), and to form macroscopic erythroid burst-forming units (BFU-E) in the presence of IL-3, erythropoietin (Epo), and SCF. We tested isolated CD34+lin- cells, a minor subset of CD34+ cells that did not display antigens associated with lymphoid or myeloid lineages, and CD34+lin+ cells, which contain the vast majority of CFC, and found that the enhanced colony growth was most dramatic within the CD34+lin- population. CD34+lin- cells cultured in liquid medium containing SCF combined with IL-3, GM-CSF, or G-CSF gave rise to increased numbers of CFC. Maximal numbers of CFU-GM were generated from CD34+lin- cells after 7 to 21 days of culture, and required the presence of SCF from the initiation of liquid culture. The addition of SCF to IL-3 and/or G-CSF in cultures of single CD34+lin- cells resulted in increased numbers of CFC due to the proliferation of otherwise quiescent precursors and an increase in the numbers of CFC generated from individual precursors. These studies demonstrate the potent synergistic interaction between SCF and other hematopoietic growth factors on a highly immature population of CD34+lin- precursor cells.     

Colony-stimulating activity in the serum of patients with hemopoietic malignancies after intensive chemotherapy/radiotherapy: its augmentation by GM-CSF in vivo and interleukin 4 in vitro.

Colony-stimulating activity (CSA) in the serum of patients with hematological malignancies increased substantially after intensive therapy with cyclophosphamide/busulfan, cyclophosphamide/total body irradiation, or melphalan/total body irradiation. This was not dependent on patients receiving allogeneic bone marrow transplantation (ABMT) or autologous bone marrow rescue (ABMR). In 44 of 62 patients CSA was maximum approximately 7 days after chemotherapy/radiotherapy, whereas in 18 of 62 patients CSA was maximum between 9 and 20 days after therapy and decreased thereafter. The time course of CSA was not dependent on disease and was not affected by recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) given as a continuous infusion for 14 days after therapy; however, serum from patients receiving rhGM-CSF produced significantly more colonies from donor bone marrow than serum from patients who did not receive the cytokine (p = 0.013). Despite the early peak in CSA in the majority of patients, there was no correlation between the time at which CSA was maximum and the return of patients' neutrophils to 500/microliters. Recombinant human interleukin 4 (IL-4) increased the number of granulocyte-macrophage colony-forming unit colonies, principally granulocyte colony-forming unit colonies, from normal bone marrow exposed to patients' serum after intensive therapy and antibody to GM-CSF reduced colony numbers. The results suggest that after intensive therapy granulocyte colony-stimulating factor (G-CSF) as well as GM-CSF is released into the serum and, in addition to acting directly with G-CSF, IL-4 may stimulate mononuclear cells to produce and/or release G-CSF.     

Detection of a human CFC with a high proliferative potential

Colony forming cells (CFC) with high proliferative potential have been detected in nutrient agar cultures of human bone marrow cells containing recombinant human interleukin-3 (IL-3) and granulocyte macrophage colony stimulating factor (GM-CSF). These CFC were detected by the formation of large colonies with diameters greater than 0.5 mm and containing approximately 50,000 cells after 28 days incubation. The incidence of these CFC was only two in 100,000 normal bone marrow cells; however, bone marrow from patients treated with 5-fluorouracil contained up to sevenfold higher numbers of these CFC. The characteristics of these CFC, multifactor-responsive progenitors with high proliferative potential, requiring a prolonged growth period in culture and showing a relative preservation in marrow from individuals pretreated with 5-fluorouracil, are consistent with a human cell type equivalent to the primitive murine progenitor termed HPP-CFC.     

Recombinant rat stem cell factor stimulates the amplification and differentiation of fractionated mouse stem cell populations.

The role of recombinant rat stem cell factor (rrSCF) was studied on defined primitive bone marrow cell populations. In agar culture of 500 lineage-negative/Sca-1-positive (Lin-/Sca-1+) cells, rrSCF alone stimulates small colonies of predominantly granulocytic cells. The combinations of rrSCF plus interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or macrophage CSF (CSF-1) stimulated primitive progenitor cells defined as high proliferative potential colony-forming cells (HPP-CFC). Synergistic increases in total colony numbers were obtained with rrSCF plus GM-CSF, granulocyte CSF (G-CSF), CSF-1, or IL-6, but not IL-1 or IL-3. Lin-/Sca-1+ cells were incubated in liquid culture at 3,000 cells/mL for 6 days in the presence of rrSCF alone or in combination with other growth factors. The total number of cells was increased twofold in the presence of rrSCF, with the progeny primarily myeloid in nature. The greatest increase in cell number was obtained with rrSCF plus IL-3, where the cell number increased 40-fold. These factors also stimulated an increase in HPP-CFC (10-fold) and GM-CFC (500-fold). To determine if these interactions were direct, single Lin-/Sca-1+ cells were sorted into microtiter wells and the cell proliferation scored 6 days later. RrSCF synergized with IL-3, IL-6, and G-CSF to stimulate the proliferation of single cells. The cells in positive wells were subcultured into colony-forming assays and up to 400 CFC per well were obtained after 14 days incubation of the secondary cultures. These data demonstrate that rrSCF acts in combination with various growth factors to directly stimulate the amplification potential of hematopoietic primitive precursors, resulting in differentiation of these precursors.     

Studies on the myeloid synergistic factor from 5637: comparison with interleukin-1 alpha

A synergistic factor that is produced by the human bladder carcinoma cell line 5637 (SF-1) stimulates primitive bone marrow progenitor cells, termed high proliferative-potential colony-forming cells (HPP- CFC), in the presence of an optimal dose of macrophage colony stimulating factor (CSF-1). Recent reports have demonstrated that interleukin-1 alpha (IL-1) is identical to hemopoietin 1 and have suggested that IL-1 is the synergistic factor present in 5637 conditioned medium (cm). We have compared the ability of recombinant human IL-1 alpha and partially purified preparations of SF-1 to synergize with optimal doses of CSF-1 to stimulate HPP-CFC. In all experiments performed the numbers of HPP-CFC colonies formed with IL-1 were significantly less than with SF-1. Replating experiments demonstrated that SF-1 plus CSF-1 generated HPP-CFC (responsive to IL-3 plus CSF-1); however, IL-1 plus CSF-1 resulted in no generation of HPP- CFC. Multiple factor combinations of IL-1 and SF-1 with G-CSF, GM-CSF, and CSF-1 also resulted in less HPP-CFC colony formation in cultures containing IL-1 compared with SF-1. Incubation of SF-1 with an antibody to IL-6 had no effect on HPP-CFC colony formation and IL-6 did not synergize with IL-1 plus CSF-1 or SF-1 plus CSF-1. These data suggest the presence of a factor in 5637 cm, which is distinct from G-CSF, GM- CSF, and IL-6, which synergizes with IL-1 to produce the SF-1 effect.     

Regulation of differentiation of murine progenitor cells derived from blast cell colonies under serum-deprived conditions

We have examined the effect of interleukin 3 (IL-3), granulocyte-macrophage (GM)-, granulocyte (G)-, and macrophage (M)-colony-stimulating factors (CSFs) on the induction of GM colonies from highly enriched murine hematopoietic progenitor cells under serum-deprived conditions. Each growth factor was tested alone or in combination with suboptimal concentrations of the others. The effect of each CSF on GM colony growth in fetal bovine serum (FBS)-supplemented cultures of unfractionated marrow cells is reported for comparison. GM-CSF induced GM colony growth in serum-deprived cultures of purified progenitor cells to the same extent as in FBS-supplemented cultures of unfractionated marrow cells. In contrast, IL-3 was only one-tenth as active in promoting the growth of enriched progenitor cells under serum-deprived conditions when compared with its effect on colony growth from unfractionated marrow. M-CSF and G-CSF were almost completely ineffective in both cases. G-CSF induction of GM colony growth from purified progenitor cells was restored by addition of suboptimal concentrations of IL-3 or GM-CSF, suggesting that either IL-3 or GM-CSF is required to observe the effect of G-CSF. Addition of G-CSF to GM-CSF-stimulated cultures did not increase the maximal number of colonies detected, indicating that these two growth factors may act on the same subset of progenitor cells. Addition of GM-CSF or IL-3 to IL-3- or GM-CSF-stimulated cultures, respectively, increased by 40% the maximal number of colonies detected, suggesting that these two factors act on at least partially separate subsets of GM progenitors. These data parallel the recent observations on the control of human GM colony formation under FBS-deprived conditions and support a model for the control of myeloid differentiation that requires the interplay of different growth factors.     

Hematopoietic progenitors in cyclic neutropenia: effect of granulocyte colony-stimulating factor in vivo.

The number and growth factor requirements of committed progenitor cells (colony-forming units-granulocyte/macrophage and burst-forming units-erythroid) in three patients with cyclic neutropenia (two congenital, one acquired) were studied before and during therapy with recombinant human granulocyte colony-stimulating factor (G-CSF; 3 to 10 micrograms/kg/d). When the patients with congenital disease were treated with G-CSF, the cycling of blood cells persisted, but the cycle length was shortened from 21 days to 14 days, and the amplitude of variations in blood counts increased. There was a parallel shortening of the cycle and increase of the amplitude of variations (from two- to three-fold to 10- to 100-fold) in the number of both types of circulating progenitor cells in these two patients. In the patient with acquired cyclic neutropenia, cycling of both blood cells and progenitors could not be seen. In cultures deprived of fetal bovine serum, erythroid and myeloid bone marrow progenitor cells from untreated patients and from normals differed in growth factor responsiveness. As examples, maximal growth of granulocyte/macrophage (GM) colonies was induced by granulocyte/macrophage (GM)-CSF plus G-CSF in the patients, whereas a combination of GM-CSF, G-CSF and interleukin-3 (IL-3) was required in the normals, and erythropoietin alone induced fourfold more erythroid bursts from cyclic neutropenic patients than from normal donors (46% versus 11% of the maximal colony number, respectively). The growth factor responsiveness of marrow progenitor cells slightly changed during the treatment toward the values observed with normal progenitors. These results indicate that treatment with G-CSF not only ameliorated the neutropenia, but also increased the amplitude and the frequency of oscillation of circulating progenitor cell numbers. These data are consistent with the hypothesis that G-CSF therapy affects the proliferation of the hematopoietic stem cell.     

In vitro differentiation of human granulocyte/macrophage and erythroid progenitors: comparative analysis of the influence of recombinant human erythropoietin, G-CSF, GM-CSF, and IL-3 in serum-supplemented and serum- deprived cultures

The effects of recombinant human erythropoietin (Ep), granulocyte/macrophage (GM) and granulocyte (G) colony-stimulating factors (CSF), and interleukin-3 (IL-3) on erythroid burst and GM colony growth have been studied in fetal bovine serum (FBS)- supplemented and FBS-deprived culture. Sources of progenitor cells were nonadherent or nonadherent T-lymphocyte-depleted marrow or peripheral blood cells from normal humans. G-CSF, in concentrations up to 2.3 X 10(-10) mol/L, induced only the formation of neutrophil colonies. In contrast, GM-CSF and IL-3 both induced GM colonies and sustained the formation of erythroid bursts in the presence of Ep. However, the activities of these growth factors were affected by the culture conditions. IL-3 induction of GM colonies depended on the presence of FBS, whereas the degree of GM-CSF induction of GM colonies in FBS- deprived cultures depended on the method by which adherent cells were removed. GM-CSF increased colony numbers in a concentration-dependent manner only if the cells had been prepared by overnight adherence. Both GM-CSF and IL-3 exhibited erythroid burst-promoting activity in FBS- deprived cultures. However, some lineage restriction was evident because GM-CSF was two- to threefold more active than IL-3 in inducing GM colonies but IL-3 was two- to threefold more active in promoting erythroid burst growth. Furthermore, in FBS-deprived cultures, the number of both erythroid bursts and GM colonies reached the maximum only when Ep, GM-CSF, and IL-3 or GM-CSF, IL-3, and G-CSF, respectively, were added together. These results suggest that the colonies induced by IL-3, GM-CSF, and G-CSF are derived from different progenitors.     

Granulocyte colony-stimulating factor enhances interleukin 3-dependent proliferation of multipotential hemopoietic progenitors.

In cultures of spleen cells from normal mice, recombinant human granulocyte colony-stimulating factor (G-CSF) supported the formation of multipotential blast cell colonies. Serial replating of the blast cell colonies in the presence of G-CSF, however, failed to demonstrate any direct effect of G-CSF on murine multipotential progenitors. We therefore examined the effects of G-CSF in combination with murine interleukin 3 on proliferation of murine blast cell colony-forming cells. The time course of total colony formation and multilineage colony formation by spleen cells harvested from mice 4 days after injection of 5-fluorouracil at 150 mg/kg was significantly shortened in cultures containing both factors in contrast with cultures supported by either factor alone. Serial observations of individual multipotential blast cell colonies (mapping) revealed that blast cell colonies emerged at random time intervals in the presence of interleukin 3 or G-CSF. The appearance of blast cell colonies, however, was significantly hastened in cultures containing both factors relative to cultures grown with either factor. In cultures of day-2 post-5-fluorouracil bone marrow cells, G-CSF in concentrations as low as 1 unit/ml revealed synergism with interleukin 3 in supporting the proliferation of multipotential progenitors. This synergistic activity may explain the previous in vivo studies suggesting the effects of G-CSF on apparent multipotential stem cells.     

Interleukin-3 in vivo: kinetic of response of target cells

Human recombinant interleukin-3 (IL-3; Sandoz AG, Basel, Switzerland) was administered for 7 days to patients with neoplastic disease and normal hematopoiesis. The purpose of the study was to assess IL-3 toxicity, to identify target cells, to define their kinetics of response at different dose levels, and to determine if IL-3 in vivo increased the sensitivity of bone marrow (BM) progenitors to the action of other hematopoietic growth factors. A total of 21 patients entered the study; the dosage ranged from 0.25 to 10 micrograms/kg/d. The effect on peripheral blood cells during treatment showed no significant changes in the number of platelets, erythrocytes, neutrophils, or lymphocytes (and their subsets). A mild monocytosis and basophilia occurred. Eosinopenia, present in the first hours of treatment, was followed by a dose-and time-dependent eosinophilia. IL-3 treatment affected BM cell proliferation by increasing the percentage of BM progenitors engaged in the S-phase of the cell cycle. The effect was dose dependent, with the various progenitors showing different degrees of sensitivity. The most sensitive progenitors were the megakaryocyte progenitors (colony-forming unit-megakaryocyte), then the erythroid progenitors (burst-forming unit-erythroid), and finally the granulo- monocyte progenitors (colony-forming unit-granulocyte-macrophage) whose proliferative activity was stimulated at the higher doses of IL-3. Only a slight increase in the proliferative activity of myeloblasts, promyelocytes, and myelocytes was observed, whereas the activity of erythroblasts was unchanged. The priming effect was such that BM progenitors, purified from patients treated with IL-3, produced more colonies in vitro in the presence of granulocyte colony-stimulating factor (G-CSF; granulocyte colonies), IL-5 (eosinophil colonies), and granulocyte-macrophage CSF (GM-CSF; predominantly eosinophil colonies). These data indicate that even in vivo IL-3 acts essentially as a primer for the action of other cytokines. Therefore, optimum stimulus of myelopoiesis will require either endogenous or exogenous late-acting cytokines such as G-CSF, erythropoietin, GM-CSF, and IL-6 for achieving fully mature cells in peripheral blood. If exogenous cytokines are used with IL-3, it is likely that G-CSF will yield more neutrophils, whereas GM-CSF may enhance eosinophils, monocytes, and neutrophils. Attention to the clinical relevance of each cell type will be necessary and should determine the selection of the combination of cytokines.     

Differential activity of recombinant colony-stimulating factors in supporting proliferation of human peripheral blood and bone marrow myeloid progenitors in culture

Unlike bone marrow progenitor cells, human myeloid progenitors isolated from peripheral blood do not form colonies in semi-solid medium in the presence of rhG-CSF, rhM-CSF or rhIL-6, but do form colonies containing neutrophils, macrophages, eosinophils, basophils or mixed neutrophilic-macrophages colonies in the presence of rhIL-3 or rhGM-CSF. Priming of blood progenitors by culturing them for several days in the presence of rhGM-CSF resulted in a dramatic increase in the frequency of cells that proliferate in response to G-CSF and IL-6 and form neutrophilic granulocytic colonies. Suspension cultures maintained in the presence of IL-3 yielded increased numbers of clonogenic cells responsive to GM-CSF and G-CSF, but not to M-CSF or IL-6. rhIL-6 did not directly stimulate colony formation of peripheral blood progenitors but did prime them to respond to G-CSF. These results are consistent with a hierarchical model of granulocytic differentiation in which circulating progenitors proceed sequentially through a programme of changing growth factor sensitivity with the following sequence: IL-3, GM-CSF, IL-6 and/or G-CSF.     

Target cells for granulocyte colony-stimulating factor, interleukin-3, and interleukin-5 in differentiation pathways of neutrophils and eosinophils.

To study the relationship between hematopoietic factors and their responsive hematopoietic progenitors in the differentiation process, both purified factors and enriched progenitors are required. We isolated total CD34+ cells, CD34+,CD33+ cells, and CD34+,CD33- cells individually from normal human bone marrow cells by fluorescence-activated cell sorter (FACS), and examined the effects of granulocyte colony-stimulating factor (G-CSF), interleukin-3 (IL-3), and IL-5 on in vitro colony formation of these cells. CD34+,CD33+ cells formed granulocyte colonies in the presence of G-CSF. Both CD34+,CD33+ cells and CD34+,CD33- cells formed granulocyte/macrophage colonies in the presence of IL-3. Eosinophil (Eo) colonies were only formed by CD34+,CD33- cells in response to IL-3, but scarcely formed by CD34+ cells in the presence of IL-5. We performed the two-step cultures consisting of the primary liquid culture for 6 days and the secondary methylcellulose culture, and serially examined changes in phenotypes of ,he cells cultured in the primary culture. CD34-,CD33+ cells derived from CD34+,CD33+ cells by preincubation with G-CSF or IL-3 formed Eo colonies in the presence of IL-5 but not IL-3. CD34-,CD33+ cells derived from CD34+,CD33- cells by preincubation with IL-3 also formed Eo colonies by support of IL-5 as well as IL-3. Both CD34+ cells gradually lost the CD34 antigen by day 6 of incubation with G-CSF or IL-3. Loss of this antigen was well-correlated with acquisition of susceptibility to IL-5. It was concluded that G-CSF supported the neutrophil differentiation of committed colony-forming cells, IL-3 supported that of both committed and multipotent colony-forming cells. G-CSF and IL-3 also supported the early stage of E. differentiation; IL-5 supported the late stage of that.     

A stimulatory effect of recombinant murine interleukin-7 (IL-7) on B- cell colony formation and an inhibitory effect of IL-1 alpha

Using a clonal culture system, we investigated the lymphohematopoietic effects of recombinant interleukin-7 (IL-7) obtained from conditioned media of transfected COS 1 cells. IL-7 alone acted on murine bone marrow cells and supported the formation of B-cell colonies. These colony cells were positive for B220, and some of them were also found to have either IgM or Thy-1. B220+, IgM- cells, but not B220- cells sorted from fresh bone marrow cells were able to form B cell colonies in the presence of IL-7. Thus, IL-7 supported the differentiation of B220+, IgM- cells to B220+, IgM+ cells. B220+, IgM+ cells did not proliferate in the presence of IL-7. IL-7 did not affect the myeloid colony formation supported by IL-3, IL-5, IL-6, granulocyte macrophage colony stimulating factor (GM-CSF), and G-CSF. On the other hand, lymphocyte colony formation was not affected by IL-2, IL-3, IL-4, IL-5, IL-6, GM-CSF, or G-CSF. Interestingly, IL-1 alpha inhibited IL-7- induced B cell colony formation in a dose-dependent manner, while the same concentration of IL-1 alpha enhanced the myeloid colony formation by IL-3. This reciprocal effect of IL-1 alpha may act on hematopoietic progenitor cells without accessory cells. These data show that IL-7 is a B cell growth factor and that IL-1 alpha may play an important role in differentiation of myeloid and lymphoid lineages.     

Synergistic interactions between hematopoietic growth factors as detected by in vitro mouse bone marrow colony formation

We have investigated the proliferative effects of several combinations of hematopoietic growth factors in agar cultures of murine bone marrow cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) synergized with granulocyte colony-stimulating factor (G-CSF), while G-CSF also synergized with macrophage colony-stimulating factor (CSF-1) and interleukin 3 (IL3), resulting in colony numbers greater than the sum of the numbers of colonies formed with each factor alone. In addition, these combinations resulted in increased colony sizes, with the formation of day-14 colonies with diameters greater than 0.5 mm. The combination of GM-CSF plus IL3 showed an increase in numbers of colonies that approximated the sum of that seen with each factor alone, however, the size of the colonies was increased with a number of day-14 and day-21 colonies having diameters greater than 0.5 mm. These data add to the list of hematopoietic factors known to synergistically stimulate myeloid progenitors and suggest that some of these interactions may be on early progenitor cells with high proliferative potentials.     

Synergy of interleukin 1 and granulocyte colony-stimulating factor: in vivo stimulation of stem-cell recovery and hematopoietic regeneration following 5-fluorouracil treatment of mice.

The human bladder carcinoma cell line 5637 produces hematopoietic growth factors [granulocyte and granulocyte/macrophage colony-stimulating factors (G-CSF and GM-CSF)] and hemopoietin 1, which synergizes with CSFs to stimulate colony formation by primitive hematopoietic stem cells in 5-fluorouracil-treated mouse bone marrow. Molecular and functional properties of hemopoietin 1 identified it as identical to interleukin 1 alpha (IL-1 alpha). When bone marrow cells from 5-fluorouracil-treated mice were cultured in suspension for 7 days with recombinant human IL-1 alpha and/or G-CSF, it was found that the two factors synergized to enhance recovery of myelopoietic cells and colony-forming cells of both high and low proliferative potential. G-CSF alone did not sustain these populations, but the combination had greater-than-additive stimulating capacity. In vivo, 5-fluorouracil (150 mg/kg) produced profound myelosuppression and delayed neutrophil regeneration for up to 2 weeks in C3H/HeJ mice. Daily administration of recombinant human G-CSF or recombinant human IL-1 alpha accelerated recovery of stem cells, progenitor cells, and blood neutrophils by up to 4 days in 5-fluorouracil-treated C3H/HeJ and B6D2F1 mice. The combination of IL-1 alpha and G-CSF acted synergistically, reducing neutropenia and accelerating recovery of normal neutrophil numbers by up to 7 days. This was accompanied by accelerated regeneration of spleen colony-forming units and erythroid, myeloid, and megakaryocytic progenitor cells in marrow and spleen, with enhanced erythroid and granulocytic differentiation. These results indicate the possible therapeutic potential of combination therapy with IL-1 and hematopoietic growth factors such as G-CSF in the treatment of chemotherapy- or radiation-induced myelosuppression.     

Human granulocyte-macrophage progenitors and their sensitivity to cytotoxins: analysis by limiting dilution

Limiting dilution analysis of granulocyte-macrophage progenitor cells was performed by using adherent and T cell-depleted normal human bone marrow and the recombinant human growth factors, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Estimated frequencies for progenitor cells responding to G-CSF were one in 489 for colonies scored at day 7, and one in 1,015 for day 14 colonies. For GM-CSF the frequencies were one in 1,407 (day 7) and one in 574 (day 14). The effects of tumor necrosis factor (TNF) and lymphotoxin (LT) on the frequency of progenitors responding to either G-CSF or GM-CSF was determined. Both TNF and LT inhibited the response of cells to G-CSF, and in these cultures the frequency of progenitor cells that responded to G-CSF was reduced to less than one in 100,000 cells. In contrast, the frequency of cells able to form colonies in cultures stimulated with GM-CSF was unaltered by either cytotoxin. This differential sensitivity to cytotoxins suggests that either G-CSF and GM-CSF are acting on separate granulocyte progenitor populations or that TNF and LT selectively influence the biochemical pathways associated with the activation of receptors for G-CSF.     

Differential effects of IL-3, GM-CSF and G-CSF in an adult with congenital neutropenia.

Using a methylcellulose culture system, we studied the effects of recombinant human interleukin-3 (IL-3), recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) from an adult patient with congenital neutropenia. The moderate clinical course and the maturation arrest at blast-promyelocyte stage in the marrow differentiated this patient from those described as having Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from the patient responded to IL-3 normally in a dose-dependent manner. GM-CSF stimulated only macrophage colony formation in a dose-dependent manner comparable to that in normal subjects. Neither GM-CSF nor G-CSF stimulated any significant granulocyte colony formation. This evidence suggests that the hematopoietic progenitor cells in this patient had the potential for developing CFU-C with IL-3, and that the neutropenia in this patient could be a result of an intrinsic defect in myelopoiesis along a granulocytic pathway responsive to GM-CSF or G-CSF.     

Granulocyte colony-stimulating factor augments in vitro megakaryocyte colony formation by interleukin-3

Granulocyte colony-stimulating factor (G-CSF) has been purified to homogeneity and the cDNA isolated. The reported properties of G-CSF have suggested that it is specific for the granulocytic lineage and only forms pure granulocyte colonies in in vitro cultures of murine bone marrow. We have demonstrated in this report that G-CSF augments the effect of interleukin 3 (IL3) on megakaryocyte formation. G-CSF alone had no stimulatory effect on megakaryocyte colony formation, however, the addition of G-CSF to IL3 in cultures of normal murine bone marrow increased the number of megakaryocyte colonies to 176% compared to cultures containing IL3 alone. Also, the combination of G-CSF plus IL3 stimulated the formation of larger megakaryocyte colonies than those formed in cultures of IL3 alone. In contrast, G-CSF had no effect on the number or size of megakaryocyte colonies stimulated by granulocyte-macrophage CSF. These results demonstrate that G-CSF augments the megakaryocyte colony formation of IL3, but not GM-CSF, and expands the lineage potential of G-CSF.     

Enrichment, characterization, and responsiveness of single primitive CD34 human umbilical cord blood hematopoietic progenitors with high proliferative and replating potential

To characterize the growth of cord blood progenitor cells, single nonadherent, low-density, T-lymphocyte-depleted CD34 cells were sorted by flow cytometer with an autoclone device into single wells containing culture medium and cytokines. These cells were evaluated for proliferation and for replating ability of their progeny. This latter effect is used as a measure of self-renewal capacity. Colony formation was assessed in 1 degree wells containing various cytokines, alone and in combination, and single colonies deriving after 21 days in semisolid medium were replated into 2 degree wells in the presence of the combination of purified preparations of recombinant human steel factor (SF, a c-kit ligand), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), interleukin-3 (IL-3), and erythropoietin (Epo). Replating of single colonies was performed also for 3 degrees, 4 degrees, and 5 degrees cultures. In the presence of serum, colony formation was observed in > 66% of the wells stimulated with the combination of Epo, SF, GM-CSF, G-CSF, and IL-3, and more than 39% of the colonies formed in these 1 degree wells were very large in size (> 2.5 mm in diameter, dense in the center, and containing > 10(4) cells/colony). The replating efficiency of these large colonies was up to 93% with generation of subsequent colonies of very large size. Replating could be shown for up to five generations. The cells in these colonies were large, nonspecific esterase positive, and contained large amounts of cytoplasm with one or more nuclei containing several nucleoli per nucleus. Smaller colonies (1 to 2.5 mm in diameter and dense in the center) containing similar cells and making up an additional 14% of the colonies formed in 1 degree wells also showed extensive replating capacity, including generation of larger colonies. These colony-forming cells are likely similar to the murine macrophage high-proliferative potential colony-forming cells. The cells giving rise to these colonies are present in about eightfold higher frequency in cord blood than in adult bone marrow. These cells may at least in part be associated with the successful hematopoietic repopulating capacity of umbilical cord blood cells.