Selective generation of erythroid burst-promoting activity by recombinant interleukin 2-stimulated human T lymphocytes and natural killer cells

Because T lymphocytes and natural killer (NK) cells produce a variety of growth factors and interleukin 2 (IL2) modulates the activity of both, we assessed the ability of IL2 to stimulate human T cells and NK cells to produce hematopoietic growth factors detectable in clonogenic marrow culture. Human recombinant interleukin 2 (rIL2) added directly to cultures of human bone marrow that had been depleted of monocytes or depleted of both monocytes and T cells caused no significant alteration of myeloid (CFU-GM) or erythroid colony formation. Conditioned media harvested from rIL2-stimulated (greater than 100 U/mL) peripheral blood mononuclear cells, T cells, Leu-2 cells, and Leu-3 cells all had erythroid burst-promoting activity (BPA) but lacked myeloid colony-stimulating factor (GM-CSF) or CFU-GM-inhibitory activity. These T cells were IL2 receptor-negative, and the addition of anti-IL2 receptor monoclonal antibody (anti-Tac) to T cell cultures did not abrogate this IL2-stimulated BPA production. In addition, Percoll gradient-enriched, large granular lymphocytes (LGL) were separated by fluorescence-activated cell sorting into Leu-11+ (NK) cells and Leu-11- (low-density Leu-4+ T) cell fractions. rIL2 stimulated LGL, Leu-11+ and Leu-11- cells to produce BPA but not detectable GM-CSF or CFU-GM-inhibitory activity. Leu-11+ (NK) cells were Tac-negative from days 0 through 14 of culture. We conclude that rIL2 at high concentrations stimulated T cells, Leu-2 and Leu-3 cell subsets, LGL, and NK cells to produce BPA but not GM-CSF and that this stimulation may be mediated by an IL2 receptor distinct from Tac or by an epitope of the IL2 receptor not recognized by the anti-Tac antibody.

A soluble activity from adherent marrow cells cooperates with IL 3 in stimulating growth of pluripotential hematopoietic precursors

Marrow cells from 5-fluorouracil (5-FU)-treated mice formed few or no mixed erythroid colonies when plated in semisolid medium with interleukin 3 (IL 3) and erythropoietin (Ep) alone. When conditioned medium (CM) from plastic-adherent marrow or thymus cells was also included, however, growth of mixed erythroid colonies was strongly stimulated. Both IL 3 and the accessory activity (AA) had to be present at the initiation of the cultures for growth to occur. AA was also produced by a cloned immortalized line (95/1.7) of fibroblastoid marrow cells that lacked macrophage-specific cell surface markers. Colony-stimulating factor-1 (CSF-1) was also released, but not granulocyte colony-stimulating activity. When 95/1.7 CM was analyzed by gel filtration, AA eluted with an apparent size of 35 kd and separated completely from the CSF-1. Biologic assays failed to detect IL 1 or IL 3 activity in 95/1.7 CM. Growth of mixed erythroid colonies from 5-FU-treated marrow is thus stimulated by adherent marrow cell-derived factors that appear distinct not only from the known CSFs including IL 3, but also from IL 1.

Hematopoietic growth factor glycosylation. Multiple forms of chicken myelomonocytic growth factor

The production of chicken myelomonocytic growth factor (cMGF) can be rapidly induced by bacterial lipopolysaccharide from the macrophage cell line HD11. Immunoprecipitation analysis of lipopolysaccharide-induced HD11 cells labeled with various radioactive precursors showed the secretion of a variety of cMGF forms. The precursor-product relationships of the different cMGF forms were studied by pulse-chase experiments, by long-term metabolic labeling in the presence or absence of glycosylation- and oligosaccharide-processing inhibitors, as well as by glycosidase treatment of immunoprecipitates. Our results show that the half-time for intracellular processing/secretion is less than 10 min, making cMGF one of the most rapidly processed proteins. The different forms of the factor are generated from a 24-kDa polypeptide precursor by co- and post-translational acquisition of one or two N-linked oligosaccharides and by O-linked glycosylation. In addition, a fraction of cMGF is modified by long chain, chondroitinase-sensitive, sulfated glycans. This modification is tunicamycin-sensitive, suggesting that the sulfated glycans are attached to N-linked rather than to O-linked oligosaccharides.

[Mechanisms of the interaction of the leukemic cell with endogenous regulators of the proliferation of hematopoietic tissue]

A substance inhibiting DNA synthesis in mouse leukemic cells was isolated from the regenerating calf spleen. When added to a suspension of leukaemic cells, this substance is adsorbed on their surface. The following changes in cell features being noticed: 1) a minute decrease in electrophoretic cell motility, 2) a decrease in esterase activity of the cells, 3) an increase in microviscosity of membrane lipids, 4) an increase in the intracellular pH values. With a longer contact with this substance, changes in nuclear chromatin structure were noticed, with special reference to weakened bonds between DNA and proteins. The data obtained are of significance for revealing molecular mechanisms of hematopoietic mediator action on target cells.

Activation and proliferation signals in murine macrophages: stimulation of glucose uptake by hemopoietic growth factors and other agents

Purified colony-stimulating factor (CSF-1) (or macrophage colony stimulating factor [M-CSF]) stimulated the glucose uptake of murine bone marrow-derived macrophages (BMM) and resident peritoneal macrophages (RPM) as measured by 3H-2-deoxyglucose (2-DOG) uptake. Similar concentrations of CSF-1 stimulated the 2-DOG uptake and DNA synthesis in BMM. Other purified hemopoietic growth factors, granulocyte-macrophage CSF (GM-CSF) and interleukin-3 (IL-3) (or multi-CSF), and the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), even though differing in their mitogenic capabilities on BMM, were also stimulators of 2-DOG uptake in BMM and RPM. The nonmitogenic agents, lipopolysaccharide (LPS) and concanavalin A (Con A), were also active. The inhibition by cytochalasin B and by high concentrations of D-glucose suggest that the basal and stimulated 2-DOG uptake occurred via a carrier-facilitated D-glucose transport system. The responses of the two macrophage populations to the hemopoietic growth factors and to the other agents were quite similar, suggesting that events that are important for the induction of DNA synthesis are not tightly coupled to the earlier rise in glucose uptake. For the BMM, the ability of a particular agent to stimulate glucose uptake did not parallel its ability to promote cell survival. However, stimulation of glucose uptake could still be a necessary but insufficient early macrophage response for cell survival and subsequent DNA synthesis.

Acetylated lipoproteins impair erythroid growth factor release from endothelial cells

Endothelial cells are a known source of hematopoietic growth-enhancing factors, including platelet-derived growth factor (PDGF). In addition, endothelium interacts directly with plasma lipoproteins which have been shown to modulate hematopoiesis. To determine the relationship of these properties, we measured the release of an erythroid growth-enhancing factor from bovine endothelial cells under lipid-loaded and control conditions. Human bone marrow cells cultured under serum-free conditions form more erythroid, granulocyte/macrophage, and mixed hematopoietic colonies when supplemented with endothelial cell-conditioned medium (ECCM) than do controls (P less than 0.05). The activity is expressed over a wide range of erythropoietin, lymphocyte-conditioned medium (LCM), recombinant human interleukin-3, and colony-stimulating factor (CSF) concentrations, and is related to ECCM dose. In contrast, enhancing activity in ECCM prepared with 0-400 micrograms/ml acetylated low density lipoproteins (AcLDL) or native LDL is diminished to 0% in a dose-dependent fashion (relative to ECCM from unexposed cells or from cells incubated with very low density lipoproteins, P less than 0.05). Upon dilution, medium prepared from cells incubated with LDL shows a rightward shift in the dose-response curve for erythroid colony formation, while that prepared from AcLDL loaded cells demonstrates a downward shift, indicating that the inhibitory activities are kinetically distinct. Delipidation of ECCM prior to addition to marrow culture removes the inhibitory action of native LDL (P less than 0.05) but not that of AcLDL (P greater than 0.10). Immunochemical analysis suggests that the erythropoietic activity in ECCM is unrelated to that of PDGF, recombinant human CSF, and erythroid burst-promoting activity (BPA) present in LCM. This conclusion is supported by Northern blot analysis of endothelial cells using a cDNA probe for the v-sis homologue of the PDGF beta chain and by immunoprecipitation of metabolically labeled PDGF. The relative amounts of c-sis transcripts and of secreted PDGF were similar in endothelial cells incubated with or without AcLDL. We conclude that AcLDL impair the synthesis or release of an erythropoietic growth-enhancing factor(s) which is biologically distinct from PDGF and BPA present in LCM.

Role of pokeweed mitogen spleen conditioned medium in regulating haematopoiesis in long-term human marrow cultures

The modulatory effect of pokeweed mitogen spleen conditioned medium (PWM-SCM) on the growth of myeloid progenitors (CFU-C) and on the composition of the stromal layer in human bone marrow long-term cultures was studied. In the presence of PWM-SCM there was enhanced CFU-C growth in the adherent layer throughout 6 weeks of incubation, with 2-fold, 2-fold and 3.4-fold increases during wk 2, 4 and 6 respectively (p less than 0.05). In the non-adherent layer of control cultures, however, there was a rapid decline in haematopoiesis which could not be offset by PWM-SCM. The differentiation pattern of CFU-C (entailing monocyte - macrophage progenitors CFU-M, granulocytic progenitors CFU-G or monocyte - granulocyte progenitors CFU-GM) was not altered by PWM-SCM. Fewer lipid-containing cells developed in the adherent layer of cultures treated with PWM-SCM than in control cultures, but the distribution pattern of monocytes - macrophages or granulocytes was not affected. These results suggest that in long-term cultures of human marrow cells there may be extensive haematopoiesis in the presence of PWM-SCM. Whether this is a direct effect on progenitor cells of stimulating factors, or rather of accessory cells in the adherent layer, remains to be clarified.

Recombinant human tumor necrosis factors alpha and beta stimulate fibroblasts to produce hemopoietic growth factors in vitro

The influences of TNF alpha and TNF beta were evaluated for their stimulatory and inhibitory effects on in vitro colony formation by human bone marrow granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells. Both TNF alpha and TNF beta induced fibroblasts to produce stimulators of CFU-GM, BFU-E, and CFU-GEMM in a dose-dependent fashion. Similar results were seen when equivalent concentrations of TNF alpha and TNF beta were used. Prior incubation of the TNF alpha and TNF beta with their respective antibodies inactivated the ability of the TNF preparations to induce the release of granulocyte-macrophage, erythroid, and multipotential colony-stimulating activity from fibroblasts. In addition, incubation of the TNF-induced fibroblast supernatant with antibody before colony assay resulted in enhanced colony formation, suggesting that the TNF carried over into the colony assay suppressed colony formation. Additional proof of this suppression by TNF was evident when TNF was added directly to the CFU-GM, BFU-E, and CFU-GEMM colony assays. IL-1 does not appear to function as an intermediary in growth factor production by fibroblasts stimulated with TNF because antibody to IL-1 displayed no effect. Furthermore, assay of TNF-induced fibroblast supernatant was negative for IL-1. These results suggest that TNF alpha and TNF beta exert both a positive and negative influence on in vitro hemopoietic colony formation.

Monoclonal anti-Thy-1.2 antibody induced hematopoiesis in vivo

The intravenous injection of a monoclonal anti-Thy-1.2 alloantibody (IgM class) induced a rapid increase in the number, and the ratio, of multipotent hematopoietic stem cells (CFU-S) in S-phase. The onset of hematopoiesis was thymus-independent. Reconstitution of lethally-irradiated mice with bone marrow cells from mice injected with antibody augmented the T-cell responsiveness to mitogens. No activation was observed in granulocyte/macrophage progenitors. The monoclonal antibody did not directly stimulate CFU-S in vitro, although hematopoietic activity could be found in the sera of antibody-injected mice. Immediately after injection, the antibody was found bound on Thy-1+ cells in spleen. No decrease in the number of peripheral T cells was seen. These results seem to indicate that Thy-1.2-positive cells bound with anti-Thy-1.2 alloantibody may secrete a factor which induces the proliferation of hematopoietic stem cells.

Induction of proliferation of acute myeloblastic leukemia (AML) cells with hemopoietic growth factors

Like their normal counterparts, leukemic blasts have recently been shown to respond to hemopoietic growth factors in both suspension culture and in semisolid media. In the present study, we have evaluated the proliferative response of 35 AML cases to colony-stimulating factors (CSFs) containing conditioned media derived from the human cell lines GCT, 5637, MO and MG U87, and to human recombinant IL-1 (rh-IL1), IL-3 (rhIL-3), GM-CSF (rhGM-CSF) and G-CSF (rhG-CSF). In the great majority of cases, an increase of 3H-thymidine (3H-TdR) uptake was obtained in response to at least one conditioned medium. The labeling index (LI) and the growth fraction (GF), evaluated in a restricted group of cases, were also increased by the growth factors, suggesting that they act by recruiting leukemic cells in cycle from the resting compartment. The ability of blast populations to form colonies was also studied. Conditioned media were found to induce or significantly increase the clonogenic capacity in 20 cases out of 22. The response of leukemic cells to human recombinant CSFs and rhIL-1, used alone or in combination, was also assayed. The results, in agreement with those obtained with conditioned media, show that each leukemic case displays a different pattern of response to CSFs, and that optimal growth conditions must be individually assessed. The possibility of increasing the fraction of cycling cells in AML populations may represent a way to render them more sensitive to cytostatic agents, with a view to new therapeutic strategies.

Hematopoietic growth factors (BPA and Epo) induce the expressions of c-myc and c-fos proto-oncogenes in normal human erythroid progenitors

We investigated serial expressions of eight proto-oncogenes during in-vitro differentiation of normal human burst-forming unit, erythroid (BFU-E), and found that c-myc and c-fos are expressed in progenies of BFU-E. The expressions of the two proto-oncogenes correlated to the replating efficiency and adversely to erythroid differentiation. The absence of hematopoietic growth factors decreased the expressions, but the addition of erythropoietin together with burst promoting activity induced a re-expression of the c-myc and c-fos after 2 h of incubation. These observations suggest that the c-myc and c-fos proto-oncogenes have a physiological role in the proliferation of erythroid progenitors and that activations of the two proto-oncogenes are early cellular events after the stimulation by hematopoietic growth factors.

Hematopoetic precursors respond to a unique B lymphocyte-derived factor in vivo

In this study we detected a factor that stimulates the proliferation of bone marrow-derived hematopoietic precursors in diffusion chambers implanted in mice. This factor, called diffusible colony-stimulating factor (D-CSF), was found in medium conditioned in the presence of spleen and peripheral blood cells from mice with B cell leukemia (BCL1). After the administration of D-CSF, the number of colonies formed in the plasma clot inside the chamber (CFU-DG) was increased, as were the number of hematopoietic precursors (CFU-MIX, CFU-S, CFU-C, and BFU-E) as judged by a subculture of diffusion chamber contents. Depletion of macrophages and T cells from the spleen cell suspension did not decrease the production of D-CSF, thereby indicating that it was derived from B cells. Neoplastic BCL1 cells appear to be the source because D-CSF could not be detected in medium conditioned with normal B cells. BCL1-conditioned medium (CM) did not enhance CFU-MIX, BFU-E, and CFU-C colony formation in vitro, which suggested that D-CSF is different from multi-CSF, EPA, or CSF. The addition of BCL1 CM to multi-CSF-, erythroid potentiating activity (EPA), and CSF (EL-4CM)-containing cultures had no effect on CFU-MIX, BFU-E, and CFU-C colony formation, thus indicating the absence of a synergistic or inhibitory activity. On the other hand, EL-4 CM, which stimulates CFU-MIX, BFU-E, and CFU-C in vitro, had no effect on CFU-DG in vivo. Biochemical characterization of BCL1 CM revealed that D-CSF is relatively heat stable and loses its bioactivity with protease treatments. It binds to lentil-lectin, according to gel-filtration chromatography has a relative molecular weight of approximately 43,000, and on reverse-phase high-performance liquid chromatography elutes with acetonitrile. These data also indicate that transformed B cells may serve as a source for hematopoietic regulators that act on hematopoietic precursors in vivo.

Early hemopoietic differentiation: the action of multi-CSF is complemented by lineage specific growth factors

Although mechanisms controlling differentiation of hemopoietic stem and early progenitor cells are still poorly understood, it is generally conceded that a pivotal role is played by hemopoietic growth factors (HGFs). However, in-vitro analysis of their action on early progenitors may be obscured by cell-cell interaction, as well as by the presence of fetal bovine serum (FBS). To overcome these limitations, we investigated the action of pure multipotent or lineage-specific HGFs on purified progenitors grown in FBS-free cultures. In the murine system, highly purified progenitors were cultured in the presence of multipotent colony-stimulating factor (multi-CSF, also termed interleukin-3), erythropoietin (Ep) and macrophagic-CSF (M-CSF). Each HGF was unable by itself to induce significant colony growth. However, combined addition of multi-CSF and either Ep or M-CSF gave rise only to pure erythroid or macrophagic colonies, respectively. Partly purified human progenitors were challenged by human granulomonocytic-CSF (GM-CSF), pluripotent CSF (PPO, also termed granulocytic-CSF, G-CSF) and Ep. Here again, each HGF was unable per se to promote colony growth, but combined addition of GM-CSF or PPO and Ep gave rise only to pure erythroid colonies. These results support a model of early hemopoietic differentiation according to which multi-lineage HGFs represent "competence" GFs, the action of which is complemented by lineage-specific "progression" HGFs.

A colorimetric liquid culture assay of a growth factor for primitive murine macrophage progenitor cells

Synergistic factors from media conditioned (CM) by human placentas or the 5637 human bladder carcinoma cell line (SFH-HPCM and SFH-5637 respectively) have the ability to stimulate early progenitor cells in mouse bone marrow to form large colonies in agar cultures after 12-14 days, in the presence of CSF-1. Culture conditions have been examined and a quicker and more convenient liquid culture assay has been developed for this factor, using a tetrazolium salt to quantitate cell proliferation. The use of flat-bottomed vessels, high cell density, supra-optimal doses of CSF-1 or the addition of WEHI-3-CM to these cultures, all resulted in a decrease in the required incubation time. In combination, these modifications reduced the assay time to 4 days.

Generation of murine hematopoietic precursor cells from macrophage high-proliferative-potential colony-forming cells

High-proliferative-potential colony-forming cells (HPP-CFC) have been described as primitive murine macrophage progenitors. We have previously demonstrated the existence of two populations of HPP-CFC: one population, termed HPP-CFC-1, is stimulated by the combination of macrophage colony-stimulating factor (CSF-1) plus haemopoietin-1 (H-1) and actively generates a second population of HPP-CFC, termed HPP-CFC-2. HPP-CFC-2 are stimulated by CSF-1 plus interleukin-3 and generate macrophage CFC that differentiate to form mature macrophages. In this study, we have demonstrated that HPP-CFC-1, when stimulated by CSF-1 plus H-1, generate colony-forming cells (CFC) for the megakaryocyte and granulocyte lineages in addition to HPP-CFC-2 and M-CFC. No CFC were detected with erythroid potential. In addition, HPP-CFC-1 generated cells that formed day-13 spleen colonies, cells that repopulated the bone marrow, cells with platelet-repopulating ability, and cells with erythroid-repopulating ability in lethally irradiated mice. These data support previous data that the HPP-CFC-1 represent a primitive hemopoietic cell population and demonstrate the multipotentiality but not totipotentiality of these cells.

Production of human hematopoietic survival and growth factor by a myeloid leukemia cell line (KPB-M15) and placenta as detected by a monoclonal antibody

Fifty-five hematopoietic cell lines, including 19 T-, 16 B-, 5 pre-B-, 5 non-T non-B-, 1 erythroid, and 9 myeloid-monocytoid cells, were screened for production of human hematopoietic survival and stem cell growth factor (SCGF) by enzyme immunoassay using anti-SCGF monoclonal antibody. The KPB-M15 myeloid cell line constitutionally secreted a considerable quantity of SCGF, while other T- or myeloid-monocytoid cell lines did not secrete SCGF. Other biomaterials investigated were fetal calf, horse, and human serum; granulocyte-macrophage colony-stimulating factor and erythropoietin preparations; human placental conditioned medium; lectin (phytohemagglutinin, concanavalin A, and pokeweed mitogen); and mixed leukocyte reaction-stimulated leukocyte-conditioned medium. SCGF was detected only in human placental conditioned medium. SCGF produced by the KPB-M15 cells was a protein with a molecular weight of 20,000. The molecule, highly purified by immunoadsorbent affinity chromatography, retained SCGF activity in vitro, e.g., erythroid burst-promoting activity and granulocyte-macrophage-colony potentiation. With the availability of purified SCGF, it is now possible to study in detail the mechanisms regulating hematopoietic stem cells.

Inhibition of hemopoietic growth factor-induced proliferation by adenosine diphosphate-ribosylation inhibitors

The effects of adenosine diphosphate (ADP) ribosylation inhibitors on hematopoietic growth factor-induced proliferation were examined. Significant inhibition of interleukin-3 (IL-3), colony-stimulating factor 1, and lung conditioned media-induced clonal agar growth of normal murine hematopoietic cells by 10 mmol/L nicotinamide (NAM), 10 mmol/L 3-aminobenzamide (3AB), and 5 mmol/L N1-methylnicotinamide (1MN) was noted. Nicotinic acid, a related compound that does not inhibit ADP ribosylation, failed to inhibit the growth factor-mediated proliferation. NAM (10 mmol/L), 3AB (10 mmol/L), and 1MN (5 mmol/L) also prevented IL-3 and phorbol ester-stimulated 3H-thymidine incorporation into the IL-3-responsive FDC-P1 cell line. Exposure of FDC-P1 cells to 10 mmol/L NAM led to a significant decrease in nuclear poly-(ADP-ribose) levels. Exposure of FDC-P1 cells to 5 mmol/L 1MN did not affect the interaction of the phorbol ester receptor, protein kinase-C (PK-C), with the cell membrane as determined by assay of phorbol ester binding in cytosol and membrane preparations. Nor did it affect the catalytic activity of PK-C as determined by assaying the in vitro phosphorylation of histone H1 by cytosolic kinase preparations from FDC-P1 as well as EL4 thymoma cells. 1MN markedly enhanced the inhibitory effects of phorbol esters on DNA synthesis of EL4 cells even at concentrations (1.25 mmol/L) that had no effects on DNA synthesis in the absence of phorbol esters. Our findings demonstrate that (a) active ADP ribosylation inhibitors interfere with growth factor-induced proliferation of murine hematopoietic cells and (b) the inhibition occurs at a step that follows the activation and translocation of PK-C and is more closely linked to DNA synthesis.

Detection of murine hemopoietin-1 in media conditioned by EMT6 cells

We have previously reported replating experiments which demonstrated the existence of subpopulations of murine high-proliferative-potential colony-forming cells (HPP-CFC). One population of HPP-CFC, termed HPP-CFC-1, is stimulated by the combination of macrophage colony-stimulating factor (CSF-1) plus hemopoietin-1 (H-1), and actively generate a second population of HPP-CFC, termed HPP-CFC-2, which is responsive to CSF-1 plus interleukin-3 (IL-3). These reclonal experiments represent an assay system that discriminates between the two types of synergistic factors, namely H-1 and IL-3. To date H-1 has only been detected in medium conditioned by human cells. In this paper we have utilized these recloning experiments to study the synergistic factor(s) present in media conditioned by the murine mammary carcinoma cell line EMT6. Colony formation in secondary cultures containing cells picked up from primary cultures incubated in CSF-1 plus EMT6-conditioned medium was identical to that seen in secondary cultures containing cells picked up from primary cultures incubated in CSF-1 plus a source of H-1. Both sets of cultures demonstrated the generation of HPP-CFC-2 in the primary cultures, indicating the presence of a molecule in EMT6-conditioned medium that is the murine equivalent of H-1.

Interleukin 1 regulates hematopoietic activity, a role previously ascribed to hemopoietin 1

A murine in vitro assay was developed to measure potentiation of a proliferative response to suboptimal concentrations of the hematopoietic regulatory molecule granulocyte/macrophage colony-stimulating factor by an immature bone marrow population. The assay, designated the 5-fluorouracil bone marrow proliferation assay, was used to characterize potentiating activity in serum-free culture supernatants of the human tumor cell line HBT 5637. Molecular and biochemical analyses indicated that the HBT 5637-derived potentiating activity could be attributed to interleukin 1 alpha. Serologic analysis using a monoclonal antibody against purified recombinant interleukin 1 alpha proved conclusively that the potentiating activity in HBT 5637 serum-free supernatants is due to interleukin 1 alpha. From these data, the activity of interleukin 1 alpha seems to be the same synergistic activity formerly ascribed to hemopoietin 1.

Role of interleukin 2 (IL 2) and hemopoietin-1 (H-1) in the generation of mouse natural killer (NK) cells from primitive bone marrow precursors

The development of natural killer (NK) cells from bone marrow (BM) precursors was studied. Recombinant interleukin 2 (IL 2) was able to induce the in vitro development of NK cells when added to cultures of mouse BM cells. Treatment of donor mice with 5-fluorouracil (150 mg/kg i.v.), which eliminates more differentiated cells but spares less differentiated cells, appears to augment NK cell development. The "NK stem cell" was found to be asialo GM1-, Thy-1+, Lyt-2-, and Lyt-1-. The cells generated in vitro had a typical phenotype of NK cells, being asialo GM1+, Lyt-5+, Thy-1+, Lyt-2-, and Lyt-1-. These effector cells also had specificity characteristics of NK cells lysing the NK-susceptible YAC-1 and K562 targets, but not the NK-resistant EL/4 or allogeneic and syngeneic blasts. Hemopoietin-1 (H-1), a factor which acts on very primitive multipotent BM cells, was able to cooperate with IL 2, increasing the development of NK cells. In contrast, other factors such as interleukin 3 or colony-stimulating factor did not cause induction of NK activity when added to cultures of BM cells, indicating that this effect, i.e., induction of NK cell development, is peculiar to IL 2. These results indicate that IL 2 can act as a differentiation as well as growth factor for NK cells, and that H-1 can promote the development of functional activity in a lymphocyte subpopulation as well as affect the differentiation of myelomonocytic and other cell lineages. This experimental system appears quite useful for characterization of BM precursors for NK cells, and should help to better understand the relationship of the NK cell lineage to the T cell or other lineages.

Inhibition by the mushroom toxins alpha-amanitin and phalloidin of hepatopoietin-induced 3H-thymidine incorporation into rat liver DNA and of plasma protein production in hepatocyte cultures

In primary cultures of rat hepatocytes the induction of 3H-thymidine uptake into DNA of liver cells by the liver cell proliferation factor hepatopoietin demonstrates that this factor is active not only in vivo but also in vitro. Addition of the mushroom toxins alpha-amanitin or phalloidin to liver cell culture decreased the uptake of 3H-thymidine into hepatocytes (in the absence or presence of hepatopoietin) as well as the attachment of the hepatocyte cultures. Mushroom toxins also inhibited the production of plasma proteins in hepatocyte cultures. The inhibition, observed at toxin concentrations from 10(-5) to 10(-7) M, was dose-dependent. At low concentrations of phalloidin the inhibition appears to be selective for certain proteins.

Hemopoietic growth factors and their interactions with specific receptors

Four hemopoietic growth factors (colony-stimulating factors--CSF's) interact with committed progenitors of granulocytes and macrophages to control their survival, proliferation, differentiation, and functional activation of the mature cells. All four growth factors have now been purified and cloned, and their human equivalents identified and cloned. In this review the most important characteristics of the biological specificities of each CSF are described and correlated with what has been learned about the interactions of the CSF's with specific cellular receptors.