Receptor for macrophage colony-stimulating factor transduces a signal decreasing erythroid potential in the multipotent hematopoietic EML cell line.

OBJECTIVE: To test the hypothesis that hematopoietic growth factors may influence lineage choice in pluripotent progenitor cells, we investigated the effects of macrophage colony-stimulating factor (M-CSF) on erythroid and myeloid potentials of multipotent EML cells ectopically expressing M-CSF receptor (M-CSFR). METHODS: EML cells are stem cell factor (SCF)-dependent murine cells that give rise spontaneously to pre-B cells, burst-forming unit erythroid (BFU-E), and colony-forming unit granulocyte macrophage (CFU-GM). We determined BFU-E and CFU-GM frequencies among EML cells transduced with murine M-CSFR, human M-CSFR, or chimeric receptors, and cultivated in the presence of SCF, M-CSF, or both growth factors. Effects of specific inhibitors of signaling molecules were investigated. RESULTS: EML cells transduced with murine M-CSFR proliferated in response to M-CSF but also exhibited a sharp and rapid decrease in BFU-E frequency associated with an increase in CFU-GM frequency. In contrast, EML cells expressing human M-CSFR proliferated in response to M-CSF without any changes in erythroid or myeloid potential. Using chimeric receptors between human and murine M-CSFR, we showed that the effects of M-CSF on EML cell differentiation potential are mediated by a large region in the intracellular domain of murine M-CSFR. Furthermore, phospholipase C (PLC) inhibitor U73122 interfered with the negative effects of ligand-activated murine M-CSFR on EML cell erythroid potential. CONCLUSION: We propose that signaling pathways activated by tyrosine kinase receptors may regulate erythroid potential and commitment decisions in multipotent progenitor cells and that PLC may play a key role in this process.

Role of the membrane form of human colony-stimulating factor-1 (CSF-1) in proliferation of multipotent hematopoietic FDCP-mix cells expressing human CSF-1 receptor.

Because IL-3-dependent multipotential FDCP-Mix cells expressing human colony-stimulating factor-1 (CSF-1) receptor did not proliferate in response to soluble CSF-1, we investigated whether their proliferation would be induced in co-culture with adherent cells expressing the membrane form of CSF-1 (MemCSF-1). FDCP-Mix cells with high CSF-1R expression (NAF21 cells) were placed on stromal MS-5 cells or STO fibroblasts expressing MemCSF-1 (2M-1 cells and STO-M2 cells, respectively), in absence of IL-3. NAF21 cells bound significantly to 2M-1 cells as compared to control FDCP-Mix cells. Adhesion of NAF21 cells was inhibited by anti-huCSF-1 antibodies, as well as anti-huCSF-1R antibodies. Interestingly, NAF21 cells proliferated on both 2M-1 and STO-M2 cells but with very different kinetics. Moreover, NAF21 cell proliferation was also supported by glutaraldehyde-fixed 2M-1 cells or highly concentrated MS-5 cell culture supernatant, but not by CSF-1 coated on culture dishes. These results strongly suggest that MemCSF-1/CSF-1R interaction mediates a specific adhesion of NAF21 cells to stromal cells and allows stimulation of hematopoietic cells by stromal cell-derived factors expressed in a membrane-bound form or concentrated within the extracellular matrix. Thus, cytokine receptors deficient in mitogenic signalling may nevertheless have a regulatory role in hematopoietic progenitor cell proliferation by acting as adhesion molecules.

Differential effects of human erythroid burst stimulating activity (HuEBSA) on human cord blood burst forming units-erythroid (BFU-Es) as a function of their differentiation state.

An erythroid stimulating activity which promotes the growth of small bursts probably arising from mature burst forming units-erythroid (BFU-Es) of adult human bone marrow cells and called human erythroid burst stimulating activity (HuEBSA), was previously found in media conditioned by a fetal human kidney cell line. In the present work we report that adding HuEBSA to cultures did not increase the burst number but increased the size of bursts from cord blood (CB) cells. A similar observation was made using stem cell factor (SCF). However, a synergistic effect on the burst number was noted when both HuEBSA and SCF were introduced to cultures. We also noticed that CB erythroid progenitors pre-cultured with 5637-Conditioned Medium [as a source of burst promoting activity (BPA)] and erythopoietin (Epo) for 3 days could be stimulated by HuEBSA but not by SCF. Similar results were obtained when interleukin 3 (IL-3) was introduced with Epo to the pre-cultures. These results suggest that two different populations of erythroid progenitors coexist in cord blood, one is Epo- and IL-3-sensitive, the other solely Epo-sensitive. It also seems probable that HuEBSA acts on erythroid progenitors arising from the more immature erythroid population, since its stimulating activity was evident after a 3-day pre-culture of cord blood cells in Epo and IL-3.

Colony-stimulating factor-1 impairs both proliferation and differentiation signals of erythropoietin during the commitment of bipotential NFS-60 cell line to the monocytic lineage.

The interleukin-3 (IL-3) dependent cell line NFS-60 contains bipotential progenitors that exhibit both erythroid and myelomonocytic potentials. In order to study their commitment to the monocytic lineage, NFS-60 cells were retrovirally transduced with mouse c-fms cDNA, which encodes the colony-stimulating factor-1 receptor (CSF-1R), resulting in the N-Fms cell line. N-Fms cells proliferated in response to CSF-1 with a growth rate similar to that obtained in response to IL-3 and progressively differentiated from myeloid blasts to monocytic cells within 3 days of culture. When maintained in IL-3, about 3% of N-Fms cells formed large hemoglobinized colonies in semisolid cultures supplemented with erythropoietin (EPO). However, this property was lost after a 24-hour cultivation in the presence of CSF-1 or, interestingly, both CSF-1 and IL-3. This loss of response to EPO was reverted following a brief passage (24 hours) in IL-3, but the rescued colonies did not undergo terminal erythrocytic differentiation. Furthermore, CSF-1 also affected proliferative response to EPO of N-Fms cells constitutively expressing EPO receptors. Our data strongly suggest that CSF-1 can suppress erythroid potential in bipotential N-Fms cells by altering proliferative and differentiation signal of EPO.

A novel growth-factor-dependent myeloid cell line derived from mouse bone marrow cells contains progenitors endowed with high proliferative potential.

Constitutive expression of human colony-stimulating factor-1 receptor (CSF-1R) confers long-lasting CSF-1-dependent proliferation to mouse myeloid cell lines. We developed mice transgenic for human CSF-1R because mouse CSF-1 cannot activate human CSF-1R. Then bone marrow cells from transgenic mice were plated onto MS-5 stromal cells expressing the membrane form of human CSF-1 (2M-1 cells) in order to combine the hematopoietic supporting properties of stromal cells and the proliferative effects of CSF-1. Thus, we were able to derive a hematopoietic cell line, called 47.10, that grew indefinitely under these conditions, whereas no cell line could be developed from nontransgenic mice. Proliferation of 47.10 cells is severely affected by neutralizing anti-CSF-1R monoclonal antibodies. Morphologic and cytofluorometry analysis established that most 47.10 cells are immature myelomonocytic cells. Consistent with this phenotype, the myeloid transcription factor PU.1, but not the erythroid transcription factor GATA-1, is expressed in 47.10 cells. A few 47.10 cells (3-5%) do not express lineage specific markers; they differentiate spontaneously to lineage-positive cells after replating on 2M-1 cells. In agar cultures, 47.10 cells form 7- and 14-day colonies in response to a cocktail of granulocyte/macrophage colony-stimulating factor (2.5 ng/mL), interleukin-3 (1 ng/mL), and mouse CSF-1 (10 ng/mL). Under these conditions, about 0.5% of 47.10 cells formed large 14-day colonies (>1 mm) composed of mature monocytes and granulocytes, reflecting the presence of progenitors endowed with high proliferative potential (HPP-47.10 cells). In conclusion, we have characterized a novel continuous myeloid cell line presenting a hierarchical structure similar to that of the bone marrow progenitor cell compartment.

Mona, a novel hematopoietic-specific adaptor interacting with the macrophage colony-stimulating factor receptor, is implicated in monocyte/macrophage development.

The production, survival and function of monocytes and macrophages are regulated by the macrophage colony-stimulating factor (M-CSF or CSF-1) through its tyrosine kinase receptor Fms. Binding of M-CSF results in Fms autophosphorylation on specific tyrosines that act as docking sites for intracellular signaling molecules containing SH2 domains. Using a yeast two-hybrid screen, we cloned a novel adaptor protein which we called 'Mona' for monocytic adaptor. Mona contains one SH2 domain and two SH3 domains related to the Grb2 adaptor. Accordingly, Mona interacts with activated Fms on phosphorylated Tyr697, which is also the Grb2-binding site. Furthermore, Mona contains a unique proline-rich region located between the SH2 domain and the C-terminal SH3 domain, and is apparently devoid of any catalytic domain. Mona expression is restricted to two hematopoietic tissues: the spleen and the peripheral blood mononuclear cells, and is induced rapidly during monocytic differentiation of the myeloid NFS-60 cell line in response to M-CSF. Strikingly, overexpression of Mona in bone marrow cells results in strong reduction of M-CSF-dependent macrophage production in vitro. Taken together, our results suggest an important role for Mona in the regulation of monocyte/macrophage development as controlled by M-CSF.

A human cell line isolated from fetal kidney produces an apparently erythroid-specific stimulating activity.

The burst formation from human and murine burst forming unit-erythroid (BFU-E) requires the presence of erythropoietin (Epo) in semi-solid cultures of bone marrow cells. A number of haematopoietic factors are described that increase the burst number: interleukin 3 (IL-3), stem cell factor (SCF), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-9, IL-11, insulin-like growth factor I, and erythroid potentiating activity (EPA). The authors now show that another activity present in medium conditioned from adult or fetal human kidney cells specifically stimulates the proliferation of BFU-E. A cell line derived from fetal kidney produced such an activity, which was shown to be different from the previously cited haematopoietins, acted on CD34(+)-enriched BFU-E and promoted an increase in CFU-E number in the bone marrow of injected animals, could be precipitated using 40% ammonium sulfate, was destroyed by proteolytic enzymes and was shown to be a glycoprotein by its retention on ConA-Sepharose. The authors propose to call this apparently novel activity, which influences only the number of bursts, human erythroid burst-stimulating activity (hEBSA).

Modulation of human and mouse erythropoiesis by thyroid hormone and retinoic acid: evidence for specific effects at different steps of the erythroid pathway.

Receptors for L-triiodothyronine (T3) and alltrans retinoic acid (ATRA) are DNA-binding proteins that can form transcriptionally active heterodimers. In this study, we sought whether T3 and ATRA could cooperate to modulate human and mouse erythropoiesis in vitro. Effects of T3 and ATRA were first assessed on burst forming unit-erythroid (BFU-E) proliferation and differentiation in semi-solid cultures. T3 did not alter the cloning efficiency of BFU-E but it decreased the production of colony forming unit-erythroid (CFU-E) during the course of BFU-E development. In contrast to T3, ATRA inhibited the early steps of BFU-E proliferation. ATRA and T3 acted in a dose-dependent manner with optimal effects at 10(-6) M and 10(-8) M, respectively. Furthermore, T3 and ATRA used in combination had more pronounced effects than when used alone, but only at their respective optimal concentrations, indicating that these effects were additive rather than synergistic. Similar results were obtained with unfractionated mouse bone marrow cells or human CD34+ bone marrow cells, suggesting that the effects of T3 or ATRA were not mediated by accessory cells. This study was extended to the mouse IL-3-dependent NFS-60 cells that can differentiate in vitro into mature erythroid cells in response to erythropoietin (Epo). When used alone, neither T3 nor ATRA could affect NFS-60 cell proliferation in response to Epo; however, T3 and ATRA had an anti-proliferative effect when used together. In addition, T3-dramatically reduced the proportion of hemoglobinized colonies in Epo-stimulated cultures of NFS-60 cells. Furthermore, ATRA, but not T3, could inhibit the IL-3-dependent proliferation of NFS-60 cells. Altogether these data suggest that T3 and ATRA can cooperate in modulating in vitro erythropoiesis although having individual effects at different but overlapping steps along the erythroid pathway.

Isolation of a murine bone marrow cell line producing a novel erythroid-enhancing activity.

Erythroid differentiation requires hematopoietic factors to proceed from early erythroid progenitors, burst-forming units-erythroid (BFU-E), to mature red cells. A number of factors possessing burst-promoting activity (BPA) have been characterized, such as interleukin-3 (IL-3), stem cell factor (SCF), and granulocyte-macrophage colony-stimulating factor (GM-CSF). These factors have broad spectra of activity on different hematopoietic and nonhematopoietic cell lines. In this paper, we describe the effect of an apparently selective erythroid factor that acts on a class of mature BFU-E, giving rise to bursts containing a relatively small number of subcolonies. This activity is produced by a bone marrow cell line; it is a glycoprotein, since it is destroyed by proteases; it is retained on Concanavalin A/Sepharose; and it precipitates at low ammonium sulfate concentration, indicating high hydrophobicity. This activity, shown to be different from known hematopoietic cytokines having BPA, exhibits an apparent strict erythroid specificity. Since it increases the development of rather small bursts probably arising from mature BFU-E, we refer to it as murine burst maturation promoting activity (mBMPA).

IL-11 directly stimulates murine and human erythroid burst formation in semisolid cultures.

The effect of interleukin-11 (IL-11) on cultures of bone marrow cells was investigated. We found that IL-11 increased, in a dose-dependent manner, the number of bursts in the presence of Epo in murine or human cells cultures. This effect was also observed in cultures of murine cells established in serum-free conditions as well as in cultures of CD34+ enriched human cells in serum-containing (but not serum-free) cultures. A linear relationship between the number of bursts and the plated cell number was observed with murine bone marrow cells or non-adherent mononuclear cells (NA-MNC) human bone marrow cells. Moreover, the effect of IL-11 was not abrogated when either anti-stem cell factor-receptor (anti-SCF-R), anti-IL-3, or anti-granulocyte/macrophage colony-stimulating factor (GM-CSF), three cytokines known to greatly synergize with IL-11, was added to cultures. These results lead us to conclude that IL-11 directly stimulates the proliferation of murine and human burst-forming units-erythroid (BFU-E).

Antiproliferative effect of D-aspartic acid beta-hydroxamate (DAH) on Friend virus-infected erythropoietic progenitor cells.

D-aspartic beta-hydroxamate (DAH), an aspartic acid analog, exerts antitumoral activity on murine leukemia L5178Y, both in vitro and in vivo. In this study, we show that DAH is also active in vivo against Friend virus (FV-P)-induced erythroleukemia, and we report the effects of DAH in vivo an in vitro on FV-P target cells, i.e. the mature erythroid colony-forming cells (CFU-E). DAH treatment (2 g/kg/day) given for 95 days as a single daily i.p. injection to DBA/2 mice either 3 or 12 days following inoculation with a high dose (10(3) plaque-forming units) of FV-P resulted in a marked increase in the mean survival time of treated animals (212 and 191%, respectively). Since FV-P elicits spleen enlargement and polycythemia, we examined the effects of DAH on spleen size, spleen-nucleated cell number, and hematocrit, in normal and FV-P infected mice, at different times in the course of continuous DAH treatments. DAH treatment initiated 3 days after viral infection inhibits the virus-induced splenomegaly, with at day 26 p.i. 1.15 x 10(8) and 12.6 x 10(8) nucleated cells per spleen observed in DAH-treated mice and untreated mice respectively, whereas only 1.03 x 10(8) nucleated cells were observed in uninfected mice. Furthermore, DAH prevents virus-induced polycythemia: on day 26, an hematocrit of 39% was measured in DAH-treated mice as compared to 60% in untreated mice. DAH treatment initiated 12 days after viral infection reduces splenomegaly, the number of nucleated spleen cells and the hematocrit of infected mice. DAH treatment initiated 3 days after viral infection prevents the tremendous increase of CFU-E in the spleen of infected mice: on day 11, the spleen of infected mice contained 4.6 x 10(6) CFU-E, while the spleen of treated mice only contained 26 x 10(3) CFU-E, and on day 26 the spleen CFU-E numbers were 45.4 x 10(6) and 1.5 x 10(6) in untreated and treated infected mice, respectively. In control uninfected mice, DAH treatment induced a transient decrease in spleen CFU-E followed by a rebound phenomenon. In vitro, preincubation with DAH inhibits colony formation by FV-P infected CFU-E, at doses starting at 3 mM, as compared to uninfected CFU-E. These data show that DAH inhibits the expression of the retroviral infection, and appears to preferentially inhibit the proliferation of infected target cells (CFU-E) in vivo.

Expression of functional human CSF-1 receptors on mouse bone marrow erythroid progenitor cells.

We have previously shown that a murine multipotent hematopoietic cell line could proliferate in response to CSF-1 after retroviral transfer of human CSF-1 receptor (CSF-1R) gene (c-fms) without loss of the erythroid differentiation potential. In the light of these data, we asked whether ectopic expression of human c-fms gene would lead to the conditional immortalization of murine hematopoietic progenitor cells. In the present studies, murine bone marrow cells were infected with recombinant retroviruses containing the human c-fms cDNA. We found that CSF-1 could exert a stimulatory activity on erythroid progenitors in the presence of Epo only when bone marrow cells had been previously infected with c-fms retroviruses. In addition, expression of human CSF-1R in murine Epo-dependent, v-src-immortalized cells resulted in CSF-1-dependent proliferation of these cells in the absence of Epo. These data show that human CSF-1R (i) can stimulate early bone marrow erythroid progenitors, (ii) might require additional signals provided by oncogenes or cytokine receptors to transduce a mitogenic signal into mouse bone marrow erythroid progenitors.

Expression of human colony-stimulating factor-1 (CSF-1) receptor in murine pluripotent hematopoietic NFS-60 cells induces long-term proliferation in response to CSF-1 without loss of erythroid differentiation potential.

NFS-60 and FDCP-Mix cells are interleukin-3--dependent multipotent hematopoietic cells that can differentiate in vitro into mature myeloid and erythroid cells. Retrovirus-mediated transfer of the human colony-stimulating factor-1 (CSF-1) receptor gene (c-fms) enabled NFS-60 cells but not FDCP-Mix cells to proliferate in response to CSF-1. The phenotype of NFS-60 cells expressing the human CSF-1 receptor (CSF-1R) grown in CSF-1 did not grossly differ from that of original NFS-60 as assessed by cytochemical and surface markers. Importantly, these cells retained their erythroid potentiality. In contrast, a CSF-1-dependent variant of NFS-60, strongly expressing murine CSF-1R, differentiated into monocyte/macrophages upon CSF-1 stimulation and almost totally lost its erythroid potentiality. We also observed that NFS-60 but not FDCP-Mix cells could grow in response to stem cell factor, (SCF), although both cell lines express relatively high amounts of SCF receptors. This suggests that SCF-R and CSF-1R signalling pathways share at least one component that may be missing or insufficiently expressed in FDCP-Mix cells. Taken together, these results suggest that human CSF-1R can use the SCF-R signalling pathway in murine multipotent cells and thereby favor self-renewal versus differentiation.

Murine interleukin 9 stimulates the proliferation of mouse erythroid progenitor cells and favors the erythroid differentiation of multipotent FDCP-mix cells.

Murine interleukin 9 (mIL-9) is a T-cell-derived growth factor that stimulates erythroid burst-forming units (BFU-E) from murine bone marrow. We further investigated this activity using enriched mouse bone marrow progenitors and the multipotent interleukin 3 (IL-3)-dependent FDCP-Mix cell line. We report here that mIL-9 stimulates erythroid burst formation of total bone marrow cells and accessory cell-depleted bone marrow cells, even in serum-free cultures. On the other hand, we observed that although mIL-9 could not support proliferation of FDCP-Mix cells, it favors erythroid differentiation of these cells in the presence of both IL-3 and erythropoietin. These results strongly suggest that mIL-9 acts directly on mouse erythroid progenitor cells.

The identification and characterization of a novel human differentiation-inhibiting protein that selectively blocks erythroid differentiation.

We have isolated a novel inhibitor of erythropoietic differentiation from the plasma of a patient suffering from idiopathic pure red cell aplasia. This differentiation-inhibiting protein (DIP) specifically blocked the differentiation of human burst-forming unit-erythroid (BFU-E), but not colony-forming unit-erythroid (CFU-E) cells. DIP also blocked the maturation of murine BFU-E cells, but not CFU-E or CFU-granulocyte-macrophage cells, and it inhibited the dimethyl sulfoxide (DMSO)-induced differentiation of Friend murine erythroleukemia cells (FLC) at levels between 10(-10) and 10(-12) mol/L. DIP activity was not detectable in the plasma of normal, healthy subjects. Unlike other known inhibitors of hematopoiesis, DIP appears to directly inhibit erythropoietic differentiation, because it did not affect the proliferation of untreated FLC and it effectively blocked FLC hemoglobinization without affecting the ability of the blocked cells to proliferate. DIP blocked FLC differentiation only when added to the culture medium within 1 hour of inducing the cells with DMSO, suggesting that the protein inhibited an early, but critical, DMSO-induced cellular process. DIP appears to be at least partially responsible for the patient's anemia, and its unique activity suggests a role in the early development of some erythroleukemias.

Erythropoiesis in long term cultures of foetal liver cells is transiently obtained on adult but not on foetal adherent cell layers.

We have previously reported long term erythroid differentiation of adult bone marrow cells seeded onto adherent cells derived from adult bone marrow. In this paper, we show that the adherent cells obtained from foetal liver do not support the erythroid differentiation of either adult bone marrow cells or foetal liver cells. Adherent layers derived from bone marrow of adult W/Wv mice supported differentiation of adult bone marrow precursors, but foetal liver progenitors only produced erythrocytes for a few weeks and the foetal origin of these red cells was confirmed by haemoglobin typing. The duration and extent of erythropoiesis was generally inversely proportional to the cell dose. Foetal progenitors were as sensitive to erythropoietin as adult cells, but were optimally stimulated at a lower plateau concentration. These results suggest that inhibitory cells present in foetal liver may block erythropoiesis and their growing importance with age may provide an explanation for the arrest of erythropoiesis in the liver at late developmental stages.

Insulin-like growth factor-1 stimulates proliferation of myeloid FDC-P1 cells overexpressing the human colony-stimulating factor-1 receptor.

Retrovirally expressed human CSF-1 receptor can induce CSF-1-dependent growth of IL-3-dependent hemopoietic cells FDC-P1. Here we show that expression of the human CSF-1 receptor also allowed FDC-P1 cells to grow in response to Insulin-like Growth Factor-1 (IGF-I). The authentic receptor for IGF-I was identified by affinity cross-linking and binding analysis on both control (infected with a neo vector) and CSF-1 receptor expressing FDC-P1 cells. DNA and RNA analysis of these cells and of five clones of IGF-I responsive cells demonstrated that the IGF-I receptor gene was not rearranged nor was it abnormally expressed in IGF-I responsive cells. These results suggest that myeloid cells over-expressing CSF-1R (c-fms protooncogene product) might have a proliferative advantage over normal myeloid cells in a physiological situation, independently of the presence of CSF-1 or the capacity of the cells to respond to CSF-1. This would indicate a possible role for c-fms in human neoplasia.

Interpretation of snow-climate feedback as produced by 17 general circulation models.

Snow feedback is expected to amplify global warming caused by increasing concentrations of atmospheric greenhouse gases. The conventional explanation is that a warmer Earth will have less snow cover, resulting in a darker planet that absorbs more solar radiation. An intercomparison of 17 general circulation models, for which perturbations of sea surface temperature were used as a surrogate climate change, suggests that this explanation is overly simplistic. The results instead indicate that additional amplification or moderation may be caused both by cloud interactions and longwave radiation. One measure of this net effect of snow feedback was found to differ markedly among the 17 climate models, ranging from weak negative feedback in some models to strong positive feedback in others.

Characterization of a novel erythropoiesis-inhibiting human protein.

We have isolated an erythropoiesis-inhibiting protein, DIP (differentiation-inhibiting protein), from the blood of a 60-year-old woman suffering from pure red cell aplasia. This protein inhibits the growth and differentiation of normal human and murine BFU-E, but not CFU-E, cells as well as dimethyl sulfoxide-induced hemoglobin synthesis by Friend murine erythroleukemia cells. It appears that DIP primarily affects differentiation rather than proliferation, because it does not inhibit the proliferation of untreated Friend erythroleukemia cells. DIP seems to function like a recently described 45-kDa autocrine differentiation-inhibiting protein factor (ADIF) which is secreted by tsAEV-transformed chicken erythroleukemia cells. Both proteins selectively block the differentiation of normal human and murine BFU-E cells as well as the differentiation (but not the proliferation) of Friend murine erythroleukemia cells. However, the human DIP is not an autocrine product of the patient's bone marrow cells, nor does it affect chicken erythroid cells.

Expression of human CSF-1 receptor induces CSF-1-dependent proliferation in murine myeloid but not in T-lymphoid cells.

The receptor for human macrophage colony stimulating factor (CSF-1R) was introduced into hematopoietic cell lines of myeloid and T-lymphoid origin, both of which normally do not express the CSF-1R. Infection of an interleukin-3 (IL-3)-dependent mouse myeloid cell line (FDC-P1) with a high titer retroviral vector expressing the human c-fms c-DNA, enabled CSF-1-dependent proliferation in short-term liquid culture assays as well as in clonal culture systems. CSF-1-dependent cell lines could be established after sorting for CSF-1R positive cells. In contrast to FDC-P1 cells, expression of the CSF-1R in CTLL cells, an IL-2-dependent mouse cytotoxic T-cell line, and in T-cell growth factor III/P40-dependent helper T-cells, ST2/K9.4a2, did not lead to CSF-1-dependent proliferation. These observations lead to the conclusion that ectopically expressed CSF-1R may function on certain myeloid cells where it is normally not expressed, suggesting the presence of signal transduction pathways which can be utilized by that foreign receptor. In contrast, it appears that T-lymphoid cells lack such a signalling mechanism, indicating that quite different modes of transducing mitogenic signals from the cell membrane to the nucleus must have developed during myeloid and T-lymphoid differentiation.