Granulocyte-macrophage Colony-stimulating Activity Research Articles

The Impact of Oral Hypoglycemics and Statins on Outcomes in Myelodysplastic Syndromes

The Impact of Oral Hypoglycemics and Statins on Outcomes in Myelodysplastic Syndromes

小児癌患者における化学療法後血球回復期単球の造血因子分泌能 (GM-CSA) について

小児癌患者における化学療法後血球回復期単球の造血因子分泌能 (GM-CSA) について

Stimulating effect of catechin, an active component of Spatholobus suberectus Dunn, on bioactivity of hematopoietic growth factor

Hematopoietic growth factor (HGF) is indispensable to hematopoiesis in the body. The proliferation and differentiation of hematopoietic cells must rely on the existence and stimulation of HGF. This study investigated the effect of catechin, an active component extracted from Spatholobus suberectus Dunn (SSD), on bioactivity of granulocyte-macrophage colony-stimulating activity (GM-CSA), burst-promoting activity (BPA) and megakaryocyte colony-stimulating activity (MK-CSA) in spleen condition medium (SPCM) of mice to clarify the hematopoietic mechanism of catechin and SSD. Spleen cells of mice were separated and spleen condition medium (SPCM) was prepared from spleen cell culture. Bone marrow cells of mice were separated and cultured in a culture system including 10% (v/v) SPCM (induced by catechin in vivo or ex vivo) for 6 days. Granulocyte-macrophage colony forming units (CFU-GM), erythrocyte burst-colony-forming units (BFU-E) and megakaryocyte colony-forming units (CFU-Meg) formation were employed to assay the effects of different treatment on the bioactivity of GM-CSA, BPA and MK-CSA in SPCM. SPCM induced by 100 mg/L catechin ex vivo could promote the growth of CFU-GM, BFU-E and CFU-Meg, which indicated that catechin could stimulate the production of GM-CSA, BPA and MK-CSA in SPCM. SPCM prepared at the fourth day of spleen cell culture showed the best stimulating activity. The bioactivity of GM-CSA, BPA and MK-CSA in the SPCM prepared after intraperitoneally injecting catechin into mice was also increased. The number of CFU-GM, BFU-E and CFU-Meg gradually increased as the dose of catechin increased and the time of administration prolonged. CFU-GM, BFU-E and CFU-Meg of the high-dose catechin group were significantly higher than those of the control group (P < 0.01) and reached the maximum at the seventh day after administration. This study suggests that catechin extracted from the active acetic ether part of Spatholobus suberectus Dunn can regulate hematopoiesis by inducing bioactivity of GM-CSA, BPA and MK-CSA in SPCM of mice. This may be one of the mechanisms for the hematopoietic-supportive effect of catechin and Spatholobus suberectus Dunn.

Induction of tolerance-inducing antigen-presenting cells in bone marrow cultures in vitro using monoclonal antibodies to CD200R.

CD200 to CD200R interactions produce immunoregulation. We investigated whether the expression of CD200R on dendritic cell (DC) precursors affects their developmental fate. C57BL/6 bone marrow (BM) cells were cultured in vitro in the presence of (interleukin-4 + granulocyte-macrophage colony-stimulating activity) to generate allostimulatory DCs, which were in turn used to induce cytotoxic T-lymphocyte and cytokine production after culture with C3H responder spleen cells. Some marrow cultures included anti-CD200R antibodies. The inclusion of monoclonal antibodies in different isoforms of CD200R in the BM culture led to a generation of cells (tolerogenic DCs) that were unable to produce allostimulation in vitro with responder cells. Cells taken from these latter mixed leukocyte cultures (MLCs) now contained CD4(+)CD25(+) cells able to inhibit the antigen-specific MLC response of fresh C3H responder cells to stimulation with C57BL/6 cells, but not stimulation with BALB/c cells. Tolerogenic DCs, infused in vivo into mice receiving C57BL/6 skin grafts, produced antigen-specific decreased rejection of BL/6 allografts, not BALB/c allografts, compared with mice receiving control DCs (generated from BM in the absence of anti-CD200R). The induction of CD4(+)CD25(+) suppressor cells in MLCs using tolerogenic DCs from the initial BM cultures could be overcome by using limiting numbers of tolerogenic DCs and an excess of allostimulatory DCs derived from BM cultures maintained in the absence of anti-CD200R. These data indicate that anti-CD200R biases stem cells in BM toward the development of suppressive antigen-presenting cells, which can induce CD4(+)CD25(+) regulatory T cells. Tolerogenic DCs have the potential to modify graft acceptance in vivo.

Dendritic cells exposed to nacystelyn are refractory to maturation and promote the emergence of alloreactive regulatory t cells.

Drugs blocking dendritic cell (DC) maturation might be useful in transplantation by inhibiting the induction of primary alloimmune responses and promoting the emergence of regulatory T lymphocytes (Treg). We investigated the effects of Nacystelyn (NAL), an N-acetyl-L-cysteine derivative, on human DCs, paying attention to the T-cell responses elicited by NAL-treated DCs in vitro. Lipopolysaccharide (LPS) was used to induce the maturation of DCs naturally present in blood or generated from human monocytes cultured in interleukin-4 and granulocyte-macrophage colony-stimulating activity. We first analyzed the consequences of NAL on cytokine production and expression of major histocompatibility complex class II and costimulatory molecules. Monocyte-derived DCs were then used as stimulators in mixed leukocyte cultures with naive CD4 T cells. Cytokine levels were measured in culture supernatants; the phenotype of T cells and their capacity to inhibit the proliferation of third-party T-cell responders was determined at the end of the culture. NAL proved to be a potent inhibitor of DC maturation in whole blood experiments and on monocyte-derived DCs. Alloreactive T cells stimulated with DCs pretreated with LPS in the presence of NAL produced much less interferon-gamma but similar levels of interleukin-13 compared with DCs treated with LPS alone. Immature DCs induced Treg, which was not observed with mature DCs. DCs cultured with LPS in the presence of NAL were as efficient as immature DCs to generate alloreactive T cells with regulatory activity. NAL is a potent inhibitor of DC maturation, which might be useful to promote allograft acceptance by inducing the differentiation of allospecific Treg.

AM5, a protein-associated polysaccharide, stimulates hematopoiesis and modulates the expression of endogenous hematopoietic growth factors in murine long-term bone marrow cultures.

We have investigated the mechanism behind the hematopoietic stimulation mediated by AM5, a protein-associated polysaccharide that stimulates in vivo the murine hematopoietic system. A dose-dependent increase in hematopoietic progenitors was observed in long-term bone marrow cultures (LTBMCs) treated in vitro with AM5. The stimulatory effect was more marked in colony-forming units-granulocyte-macrophage (CFU-GM) than in CFU-spleen (CFU-S) progenitors and also more significant in the supernatant than in the adherent layer. This stimulatory effect was reversible, and continuous stimulation with high doses of AM5 was conductive to a progressive exhaustion of the culture. The analysis of the CFU-GM stimulating activity present in the supernatant of AM5-treated cultures revealed a dose-dependent induction of granulocyte-macrophage colony-stimulating activity (GM-CSA), in contrast with control cultures in which no CSA was detected. Northern blots of LTBMC-adherent layers obtained after in vitro treatment with AM5 revealed a significant mRNA expression for interleukin 1 alpha (IL-1 alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage CSF (M-CSF) and granulocyte CSF (G-CSF), in contrast with adherent layers from untreated cultures which only expressed, in detectable levels, M-CSF and stem cell factor (SCF). The SCF expression was down-modulated in AM5-treated cultures. Our results strongly suggest that the hematopoietic stimulation induced by AM5 is mediated by the modulated expression of endogenous hematopoietic growth factors.

Effects of combination of immunomodulators and an adrenochrome derivative on survival of irradiated mice

Purpose : The combined effects of immunomodulators (lithium or OK432) and an adrenochrome derivative (AMM), an agent found to activate granulocyte-macrophage colony stimulating activity, on the survival of irradiated ddY mice is described. Methods and Materials : ddY mice at 4–5 weeks old were whole body irradiated with X rays at 8.5 Gy. Sole injection and combined injection of AMM and/or one of the immunomodulators were performed before or after irradiation. Then, survival was monitored daily for 30 days after irradiation. Results : Lithium at 60 mg/kg had no radioprotective effect; rather it accelerated radiation induced death. Sole treatment with AMM (100 mg/kg) had no effect on survival of irradiated mice. However, combination of both drugs caused a slight radioprotection. OK432 (25 KE/kg), which activates a variety of cellular effector cells had radioprotective effect. When combined with AMM, however, it totally lost radioprotective effect. Conclusion : Lithium chloride cannot be used as a radioprotector because of its adverse effect. Combination with AMM showed slight radioprotection, but the extent thereof may not be clinically useful. OK432 was proved to be a potent radioprotector. However, combination with AMM should be avoided, since the radioprotection was totally eliminated.

Colony promoting activity (CPA) is a novel factor distinct from IL-6

The supernatant (CM) of long-term bone marrow culture (LTBMC) contains colony promoting activity (CPA) which does not have granulocyte-macrophage (GM) colony-stimulating activity but which enhances GM-colony formation in the presence of CSF. CPA is different from IL-1, IL-3 and GM, G-, and M-CSF. Since CPA-containing LTBMC-CM always contains a substantial level of IL-6, CPA was thought to be similar to IL-6. In the present study. we found that LTBMC with a particular batch of horse serum produced IL-6 without a corresponding production of CPA. Addition of IL-6 to GM-colony assay system in the presence of GM-CSF did not enhance the colony formation. LTBMC-CM did not stimulate proliferation nor differentiation of mast cell progenitors. Anti-IL-6 antibodies suppressed IL-6 activity, but not CPA. These results indicate that CPA is a novel factor distinct from IL-1, IL-3, G-, M-, GM-CSF, IL-6 and SCF ( c-kit ligand).

Microglial mitogens are produced in the developing and injured mammalian brain.

The central nervous system produces growth factors that stimulate proliferation of ameboid microglia during embryogenesis and after traumatic injury. Two microglial mitogens (MMs) are recovered from the brain of newborn rat. MM1 has an approximate molecular mass of 50 kD and a pI of approximately 6.8; MM2 has a molecular mass of 22 kD and a pI of approximately 5.2. These trypsin-sensitive proteins show specificity of action upon glia in vitro serving as growth factors for ameboid microglia but not astroglia or oligodendroglia. Although the MMs did not stimulate proliferation of blood monocytes or resident peritoneal macrophage, MM1 shows granulocyte macrophage colony-stimulating activity when tested upon bone marrow progenitor cells. Microglial mitogens may help to control brain mononuclear phagocytes in vivo. The MMs first appear in the cerebral cortex of rat during early development with peak levels around embryonic day E-20, a period of microglial proliferation. Microglial mitogens are also produced by traumatized brain of adult rats within 2 d after injury. When infused into the cerebral cortex, MM1 and MM2 elicit large numbers of mononuclear phagocytes at the site of injection. In vitro study shows that astroglia from newborn brain secrete MM2. These observations point to the existence of a regulatory system whereby secretion of proteins from brain glia helps to control neighboring inflammatory responses.

Induction of granulocyte-macrophage colony-sitmulating activity toy 12-O-tetradecanoylphobol-13-acetate in SENCAR and B6C3F1 mice

Previous studies in this laboratory and others have indicated that 12-O-tetradecanoylphorbol-13-acetate (TPA), the most potent skin tumor promoter known, evokes significantly greater inflammatory responses in phorbol ester-sensitive (SENCAR) mice compared to strains (e.g. C57BL/6 and B6C3F1) that are relatively resistant to the outgrowth of skin tumors in two-stage chemically induced carcinogenesis protocols. In the studies reported herein, subchronic topical application of TPA at doses relevant to two-stage protocols induced serum granulocyte-macrophage colony-stimulating activity (GM-CSA) in both SENCAR and B6C3F1 mice; however, the increase in SENCAR mice was significantly greater than that observed in the relatively resistant B6C3F1 strain (5-fold versus a 2-fold increase respectively). The greater increase in serum GM-CSA observed in SENCAR mice was correlated with a 31% increase in the number of splenic leukocytes that lacked both B and T cell surface markers (i.e. double-negative cells), a presumed GM progenitor cell; no significant increase in the relative percentage of such cells was observed in B6C3F1 mice. Alternatively, significant decreases in splenic T lymphocytes (23 and 32% in SENCAR and B6C3F1 respectively) were observed in both strains of TPA-treated mice and may, in part, account for the previously observed decreases in splenic cell blastogenic response to the T cell mitogen phytohemagglutinin (PHA). In vitro incubation of splenic cells from SENCAR mice with 0.01-1.0 microM TPA led to significantly greater increases in colony formation relative to splenic cells isolated from B6C3F1 mice; therefore, differences in the biochemical responsiveness between strains may occur at the level of signal transduction in splenic GM progenitor cells. In conclusion, these studies indicated that strain-dependent differences in the systemic inflammatory response following topical application of TPA may result from direct stimulation of splenic GM precursor cells by TPA and/or may occur, indirectly, through the release of cytokines [e.g. GM colony-stimulating factor (GM-CSF)] by induced epidermal (or other) cells.

Colony stimulating activity in the serum of patients with multiple myeloma is enhanced by interleukin 3: a possible role for interleukin 3 after high dose melphalan and autologous bone marrow transplantation for multiple myeloma

Sera from 36/37 multiple myeloma patients and 19/21 sera from patients with other solid or liquid tumours had granulocyte-macrophage colony stimulating activity (CSA) towards normal human donor bone marrow whereas 1/16 sera from normal donors had this activity. Unlike human rhGM-CSF and GM-CSF from 5637 (human bladder cell line) conditioned medium which is heat stable, CSA from serum is heat labile (56 degrees C/30 min). In multiple myeloma patients, CSA was detectable more than 2 years after treatment with 'high dose melphalan. Although multiple myeloma patients, at relapse, have sufficient CSA in their serum to produce maximal stimulation of GM-CFUc from normal donor bone marrow in vitro, their own GM population responds poorly. The results suggest that the failure of patients own bone marrow to respond to endogenous CSA may be due to damage to the stem cells of the marrow or the failure of precursor cells to respond to CSA. Addition of rhIL-3 to myelomatous serum increased the number of GM-CFUc from both normal and myelomatous bone marrow but did not stimulate the growth of MY-CFUc significantly. The results suggest that rhIL-3 may assist bone marrow recovery in multiple myeloma patients after intensive chemotherapy.

Colony promoting activity: differences from interleukin-3 and similarities to interleukin-6

The supernatant of long-term bone marrow culture contains colony promoting activity (CPA) which does not have granulocyte-macrophage colony stimulating activity (CSF) but which enhances granulocyte-macrophage (CM) colony formation in the presence of CSR CPA might consist of IL-3 or IL-3-like activity, since CPA stimulates proliferation and differentiation of more immature cells to CSF-responding granulocytes-macrophage progenitors (GM-CFC), and since IL-3 also stimulates immature hemopoietic cells to proliferate and differentiate to functional blood cells. IL-1 and IL-6 are also known to enhance GM colony formation. One or both of these molecules can accordingly be another candidate for CPA. In the present study, GM-CSF activity of IL-3 was dependent on the batch of serum: it was negative in the presence of fetal calf serum, but positive in the presence of horse serum. In contrast, GM-CSF and CPA showed no such dependence on the batch of serum. The addition of IL-3 to GM colony assay system did not enhance but rather suppressed GM colony formation. The supernatant of long-term bone marrow culture which contains substantial levels of CPA did not stimulate proliferation of IL-3 dependent DA-1 cells, but facilitated the proliferation of IL-6 dependent, MH60-BSF2 cells. No detectable level of IL-1 activity was found in the supernatant. These results indicate that CPA is different from IL-1, IL-3 or GM-CSF, but similar to or the same as IL-6.

Human G‐CSF produced by adherent cells in the presence of human recombinant GM‐CSF

Adherent cells (AdCs) in blood from normal volunteers produced granulocyte-macrophage (GM) colony-stimulating activity (CSA) in the presence of 10 ng/ml of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) in vitro. GM-CSA produced by adherent cells in the presence of GM-CSF reached a plateau level on day 6. Colonies stimulated by adherent cell-conditioned medium (AdC-CM-GM-CSF), which had been harvested after 6 days of incubation of AdCs with rhGM-CSF, were granulocyte predominant. When phagocyte-depleted marrow mononuclear cells (PD-M-MNCs) were cultured with AdC-CM-GM-CSF and anti-rabbit serum against rhGM-CSF, 99% of the colonies on day 7 were exclusively composed of neutrophils. When 2 X 10(4) PD-M-MNCs were cultured in a medium containing AdC-CM-GM-CSF, AdC-CM-GM-CSF + anti-GM-CSF, AdC-CM-GM-CSF + anti-G-CSF, or AdC-CM-GM-CSF + both of the anti-bodies, the PD-M-MNCs formed (mean +/- SD) 100 +/- 2.0%, 64.3 +/- 2.5%, 38.6 +/- 0.4%, and 6.0 +/- 0.4% GM colonies, respectively. Furthermore, northern blot analysis revealed that AdCs incubated with 10 ng/ml of rhGM-CSF for 6 h expressed much more mRNA of G-CSF than those without the CSF. These data indicated that AdCs in blood produce G-CSF in the presence of GM-CSF.

Presence of an activity indispensable for the granulocyte/macrophage colony-stimulating activity of interleukin 3 in bovine serum albumin

Media conditioned by an interleukin 3 (IL-3)-producing T-cell line, STIL-3, as well as recombinant mouse IL-3 showed granulocyte/macrophage (GM) colony-stimulating activity in the semi-solid culture medium containing horse serum (HS) or bovine serum, but the activity was not apparent when fetal calf serum (FCS) was used. No such serum-dependency of GM colony formation was observed when abdominal wall conditioned medium or L-cell conditioned medium containing GM colony-stimulating factor was used. Although the levels of albumin and total protein were lower in FCS than HS, increase of FCS concentration did not affect the GM colony-stimulating activity of IL-3. Addition of bovine serum albumin (BSA) preparation to FCS, however, increased the number of GM colonies to the same level as that observed with HS. The levels of bacterial lipopolysaccharide (LPS) in sera and BSA and the effect on the bone marrow cells from LPS-nonresponsive C3H/HeJ mice indicated that the observed effect of BSA was not due to the contaminating LPS. The activity of BSA was not substituted by IL-1, IL-2, IL-4, IFN-gamma, TNF, NGF or erythropoietin. The present study suggests the presence in BSA of co-factor(s) of IL-3 in stimulating GM colony formation.

Interleukin-1 potentiates granulopoiesis and thrombopoiesis by producing hematopoietic factors in vivo

In vivo administration of recombinant human interleukin-1 β (rHu IL-1β) selectively enhanced the recovery from granulocytopenia and thrombocytopenia caused by whole body irradiation, in a dose dependent manner. Since IL-1 itself in vitro had no colony-stimulating activity (CSA), we studied whether IL-1 can produce hematopoietic factors in vivo, which in turn will promote granulopoiesis and thrombopoiesis. Serum from IL-1 injected mice showed marked granulocyte/macrophage CSA (GM-CSA), but little megakaryocyte CSA (Meg-CSA) Interestingly, strong megakaryocyte potentiator ( Meg-POT ) activity was detected in the serum. Further analysis of the serum by gel filtration chromatography showed that Meg-POT activity could be eluted in different fractions from GM-CSA. Since erythropoietin which is known to simulate erythropoiesis also exhibited remarkable Meg-POT activity, serum from IL-1 injected mice were assayed for erythroid CSA. We found that unlike erythropoietin the serum showed no erythroid CSA. Taken together, these results suggest that IL-1 may potentiate granulopoiesis and thrombopoiesis by producing at least two distinct types of hematopoietic growth factors in vivo, namely granulocyte/ macrophage colony-stimulating factor and a thrombopoietin-like factor.

Down Regulation of Myelopoiesis by Mediators Inhibiting the Production of Macrophage-Derived Granulomonopoietic Enhancing Activity (GM-EA)

Monocyte-derived lipid-containing macrophages (MDLMs) constitutively synthesize a granulomonopoietic enhancing activity (GM-EA) that potentiates the function of granulocyte-macrophage colony-stimulating activity (GM-CSA). In the study reported, we show that GM-EA is distinct from interleukin-1 (IL-1) in biochemical and functional properties and that its production is negatively regulated by several mediators. Thus, MDLM cultures pretreated with interferon-gamma (IFN-gamma, 3 to 900 U/mL), prostaglandin E2 (PGE2, 10(-13) to 10(-8) mol/L), or lactoferrin (LF, 10(-13) to 10(-8) mol/L) invariably produced less GM-EA than untreated controls. The relative potency of inhibition was in the order of IFN-gamma greater than or equal to PGE2 greater than LF. The extent of the inhibitory effects was proportional to dosage and the duration of treatment and could be observed following only a brief exposure (two hours) of the MDLMS to physiologic doses of the mediators. Under optimal conditions, IFN-gamma (300 U/mL for 24 to 48 hours) and PGE2 (10(-9) mol/L for 24 to 48 hours) could totally abrogate the ability of the MDLMs to produce GM-EA. However, the drug-inhibited MDLMs could be reactivated to produce GM-EA by treatment with zymosan (60 micrograms/mL). These results demonstrate that a mechanism for the control of myelopoiesis by mediators such as IFN-gamma, PGE2, and LF may involve the inhibition of GM-EA production. Furthermore, this negative feedback control is reversible and can be overridden when a proper stimulatory signal is given.

Down regulation of myelopoiesis by mediators inhibiting the production of macrophage-derived granulomonopoietic enhancing activity (GM-EA)

Monocyte-derived lipid-containing macrophages (MDLMs) constitutively synthesize a granulomonopoietic enhancing activity (GM-EA) that potentiates the function of granulocyte-macrophage colony-stimulating activity (GM-CSA). In the study reported, we show that GM-EA is distinct from interleukin-1 (IL-1) in biochemical and functional properties and that its production is negatively regulated by several mediators. Thus, MDLM cultures pretreated with interferon-gamma (IFN- gamma, 3 to 900 U/mL), prostaglandin E2 (PGE2, 10(-13) to 10(-8) mol/L), or lactoferrin (LF, 10(-13) to 10(-8) mol/L) invariably produced less GM-EA than untreated controls. The relative potency of inhibition was in the order of IFN-gamma greater than or equal to PGE2 greater than LF. The extent of the inhibitory effects was proportional to dosage and the duration of treatment and could be observed following only a brief exposure (two hours) of the MDLMS to physiologic doses of the mediators. Under optimal conditions, IFN-gamma (300 U/mL for 24 to 48 hours) and PGE2 (10(-9) mol/L for 24 to 48 hours) could totally abrogate the ability of the MDLMs to produce GM-EA. However, the drug- inhibited MDLMs could be reactivated to produce GM-EA by treatment with zymosan (60 micrograms/mL). These results demonstrate that a mechanism for the control of myelopoiesis by mediators such as IFN-gamma, PGE2, and LF may involve the inhibition of GM-EA production. Furthermore, this negative feedback control is reversible and can be overridden when a proper stimulatory signal is given.

Factors influencing release of granulocyte-macrophage colony-stimulating activity from human mononuclear phagocytes.

Mononuclear phagocytes play an important role in the regulation of hematopoiesis, not only by producing regulatory monokines such as prostaglandins, tumor necrosis factor and interleukin-1 (IL-1), but also by the production of colony-stimulating activity (CSA). Previously, we have demonstrated that granulocyte-macrophage CSA (GM-CSA) production by mononuclear phagocytes can be induced by IL-1. In the present study, the influence of culture conditions on the production of GM-CSA was studied. It was found that both human sera and fetal bovine sera contain constituents - at present undefined - that induce GM-CSA production. These factors are distinct from IL-1 and lipopolysaccharide. In selected experiments, no GM-CSA-inducing effect of serum was found, suggesting that the effect may be donor-related. GM-CSA release in the presence of serum could be reduced by 40% after incubation of mononuclear phagocytes at low cell concentrations in methylcellulose, indicating that intimate cell-cell contact is an additional factor that enhances GM-CSA release.

Granulocyte macrophage colony-stimulating activity production by cultured human thymic nonlymphoid cells is regulated by endogenous interleukin-1

Supernatants of cultured human thymic nonlymphoid cells were assayed for granulopoietic factors using cultures of low density bone marrow mononuclear cells (LD-BMMC). Thymic nonlymphoid cell-conditioned medium (TNLC-CM) supported vigorous myeloid colony growth of LD-BMMC, and of LD-BMMC depleted of T lymphocytes and/or monocytes. Colony stimulating activity (CSA) in TNLC-CM was abrogated by a highly specific neutralizing antiserum against recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). TNLC-CM also enhanced colony growth in LD-BMMC stimulated by colony stimulating activity from a giant cell tumor culture (GCT). The enhancing activity of TNLC-CM, unlike its CSA activity, required the presence of adherent cells in the marrow cell culture. The addition of anti-interleukin-1 (anti-IL-1) antibody to TNLC-CM inhibited the GCT-enhancing activity, but not the CSA. When the anti-IL-1 immunoglobulin was added directly to cultures of thymic nonlymphoid cells, GM-CSF production was completely inhibited, and the GCT enhancing activity was neutralized. We conclude that an intercellular regulatory network exists in cultured thymic explants in which GM-CSF expression is induced by IL-1. In this system, the granulopoietic effect of IL-1 derives not from a direct effect on myeloid progenitors, but from its ability to recruit CSA production by other cells.

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.