Inhibition of human erythroid colony-forming units by interleukin-1 is mediated by gamma interferon.

IL-1 inhibits erythropoiesis in vivo and in vitro. This inhibition was studied by comparing the effect of recombinant human IL-1 (rhIL-1) on highly purified CFU-erythroid (E) generated from peripheral blood burst-forming units-erythroid (BFU-E) (mean purity 44.4%) with its effect on unpurified marrow CFU-E (mean purity 0.36%). Colony formation by marrow CFU-E was significantly inhibited by rhIL-1, while colony formation by highly purified CFU-E was not inhibited. However, purified CFU-E colonies were inhibited by rhIL-1 in the presence of autologous T-lymphocytes, and also by cell-free conditioned medium prepared from T-lymphocytes stimulated by rhIL-1. This inhibitory effect was ablated by neutralizing antibodies to gamma interferon (IFN), but not by antibodies to human IL-1, tumor necrosis factor, or beta IFN. Colony formation by highly purified CFU-E was also inhibited by recombinant human gamma IFN (rh gamma IFN). IL-1 and gamma IFN play significant roles in the pathogenesis of the anemia of chronic disease. These studies indicate that rhIL-1 inhibits CFU-E colony formation by an indirect mechanism involving T-lymphocytes and requiring gamma IFN and that gamma IFN itself is most probably the direct mediator of this effect.     

An erythropoietic stimulating factor similar to erythropoietin released by macrophages after treatment with silica

An erythropoietic stimulating factor (ESF) can be detected in the supernatant from fetal liver and adult bone marrow and spleen cells when preincubated with the macrophage-specific cytotoxic agent, silica. Stimulation is observed in 12-day fetal liver CFU-E cultures in the absence of added erythropoietin (Ep). The concentration of ESF in the supernatant added to CFU-E cultures is dependent on the preincubated cell dose and the volume added. The stimulating activity is abolished when mice are hypertransfused and increased above normal values when mice are bled. A concentrated silica-treated spleen supernatant was able to stimulate erythropoiesis in the polycythemic mouse bioassay. It is concluded that the ESF is similar, if not identical, to Ep.     

Murine B-cell stimulatory factor-1 (BSF-1)/interleukin-4 (IL-4) is a multilineage colony-stimulating factor that acts directly on primitive hemopoietic progenitors

Interleukin-4 (IL-4), which was originally identified as a B-cell growth factor, has been shown to produce diverse effects on hemopoietic progenitors. The present study investigated the effects of purified recombinant murine IL-4 on early hemopoetic progenitors in methylcellulose culture. IL-4 supported the formation of blast cell colonies and small granulocyte/macrophage (GM) colonies in cultures of marrow and spleen cells of normal mice as well as spleen cells of mice treated with 150 mg/kg 5-fluorouracil (5-FU) 4 days earlier. When the blast cell colonies were individually picked and replated in cultures containing WEHI-3 conditioned medium and erythropoietin (Ep), a variety of colonies were seen, including mixed erythroid colonies, indicating the multipotent nature of the blast cell colonies supported by IL-4. To test whether or not IL-4 affects multipotent progenitors directly, we replated pooled blast cells in cultures under varying conditions. In the presence of Ep, both IL-3 and IL-4 supported a similar number of granulocyte/erythrocyte/macrophage/megakaryocyte (GEMM) colonies. However, the number of GM colonies supported by IL-4 was significantly smaller than that supported by IL-3. When colony-supporting abilities of IL-4 and IL-3 were compared using day-4 post-5-FU spleen and day-2 post-5-FU marrow cells, IL-4 supported the formation of fewer blast cell colonies than did IL-3. IL-4 and IL-6 revealed synergy in support of colony formation from day 2 post-5-FU marrow cells. These results indicate that murine IL-4 is another direct-acting multilineage colony-stimulating factor (multi-CSF), similar to IL-3, that acts on primitive hemopoietic progenitors.     

Differentiation of erythroid progenitor (CFU-E) cells from mouse fetal liver cells and murine erythroleukemia (TSA8) cells without proliferation.

Erythropoietin (epo) appears to play a significant role in influencing the proliferation and differentiation of erythroid progenitor (CFU-E) cells. To determine the mechanism of action of epo, the effect of drugs on the in vitro colony formation of CFU-E cells induced from a novel murine erythroleukemia cell line, TSA8, was examined. While cytosine arabinoside inhibited colony formation and terminal differentiation of the CFU-E cells responding to epo, herbimycin, which is a drug that inhibits src-related phosphorylation, inhibited colony formation only. The same effect of herbimycin was observed with normal CFU-E cells from mouse fetal liver cells. These results suggest that epo induces two signals, one for proliferation and the other for differentiation, and that the two signals are not linked in erythroid progenitor cells.     

小鼠胎肝基质细胞造血刺激因子体外生物活性研究

本实验对基质细胞造血刺激因子－１（ＳＨＦ－１）的体外生物活性进行了研究。结果表明,ＳＨＦ－１可刺激小鼠骨髓ＣＦＵ－Ｅ、ＢＦＵ－Ｅ、ＣＦＵ－ＧＭ、ＣＦＵ－Ｍｉｘ集落的形成,它产生的这些广泛造血刺激作用是其自身所具活性的直接影响。正常小鼠骨髓细胞与ＳＨＦ－１在体外孵育４ｈ,其中ＣＦＵ－Ｓ的自杀率可提高约１０％,显示它对造血干细胞也有诱导增殖作用。     

Thrombopoietic activity of human interleukin-6

Thrombopoietin (TPO), a regulatory factor in platelet production, was purified from the conditioned medium of TNK-01 cells cultured in the presence of human interleukin-1. The N-terminal sequence of purified TPO was determined to be VPPGEDSKDVAAPHRQPLT, identical to that of the N-terminal region of human interleukin-6 (IL-6). Two forms of TPO with molecular masses of 24 and 27 kDa were identified as IL-6 by Western analysis using an anti-IL-6 antibody. Commercial recombinant human IL-6 produced in Escherichia coli, stimulated megakaryocyte colony formation in the presence of mouse interleukin-3 and increased the number of peripheral platelets in mice in a dose-dependent manner. From these results, it is concluded that human IL-6 has thrombopoietic activity.     

Myeloproliferative sarcoma virus: its effects on erythropoiesis in adult DBA/2J mice

Adult susceptible mice (DBA/2J) infected with MPSV (myeloproliferative sarcoma virus), a defective RNA tumour virus, develop splenomegaly and progressive disruption of the haematologic system culminating in death. The present study was specifically directed toward determining the effects of the virus on erythroid differentiation. Early and late precursor cells (erythroid burst-forming units; BFU-E and colony-forming units; CFU-E, respectively) were evaluated by the ability of bone marrow and spleen cells to form colonies of fully differentiated erythroid cells in vitro. MPSV caused substantial modification of both the BFU-E and CFU-E populations in the bone marrow and spleen of infected animals. Changes were detected in the CFU-E population preceding any significant increase in spleen weight. In the bone marrow, the proportion of CFU-E cells increased almost twofold by days 5-10 after virus infection but decreased by day 15. In the spleen, CFU-E frequency rose 40-fold by days 10-15 and then declined steadily prior to death. At the peak of CFU-E expansion, a small proportion of the population appeared to be erythropoietin (Ep) independent, although there was no evidence of a complete switch to Ep-independence which occurs in Friend virus-induced erythroleukemia. Dose-response curves showed that none of these data could be explained in terms of a changing responsiveness to Ep. However, evidence is presented that indicates that BFU-E from MPSV-infected animals lose or have a reduced requirement for burst-promoting activity (BPA) relative to normal cells although their progeny still need Ep for terminal erythroid differentiation.     

Erythropoietic progenitors capable of colony formation in culture: state of differentiation

The differentiated state of mouse erythropoietic progenitor cells (CFU-E), detected by their ability to form erythropoietin-dependent colonies in vitro, has been investigated. Transfusion-induced plethora was found to reduce the population size of CFU-E in both spleen and femoral marrow, which indicates that a significant number of CFU-E arise by differentiation processes that are themselves erythropoietin-dependent. Individual spleen colonies were found to be heterogeneous in their content of CFU-E, and the numbers of CFU-E per colony were not correlated either positively or negatively with the numbers of granulocyte-macrophage progenitors (CFU-C) present in the same colonies. The absence of a negative correlation between CFU-E and CFU-C indicates that the erythropoietic and granulopoietic pathways of differentiation are not mutually exclusive within individual spleen colonies. The numbers of CFU-E per spleen colony were also found to vary independently of the numbers of pluripotent stem cells (CFU-S) per colony; in contrast, as found previously, the numbers of CFU-C and CFU-S per colony were positively correlated. These results indicate that more randomizing events separate CFU-E from CFU-S than separate CFU-C from CFU-S, and are consistent with the view that CFU-E occupy a position on the erythropoietic pathway of differentiation that is more remote from the pluripotent stem cells than is the corresponding position of CFU-C on the granulopoietic pathway.     

Interactions between purified GM-CSF, purified erythropoietin and spleen conditioned medium on hemopoietic colony formation in vitro.

Preincubation of C57BL adult marrow cells or CBA fetal liver cells with a 250-fold excess concentration of purified GM-CSF failed to reduce the frequency of cells forming eosinophil, megakaryocyte or erythroid colonies in subsequent agar cultures. When excess concentrations of purified GM-CSF were added to agar cultures stimulated by pokeweed mitogen-stimulated spleen conditioned medium (SCM), no reduction was observed in the frequency of eosinophil, megakaryocyte or erythroid colonies. Addition of 4 units of purified erythropoietin (EPO) to cultures of fetal liver or adult marrow cells stimulated by SCM increased the number of erythroid colonies but did not reduce the number of non-erythroid colonies or the non-erythroid content of mixed erythroid colonies. Although neither GM-CSF nor EPO alone was able to stimulate erythroid colony formation in agar cultures of fetal liver cells, small numbers of large erythroid colonies were stimulated to develop in cultures containing both purified regulators. Purified GM-CSF was also able to support the survival in vitro of a small proportion of erythroid colony-forming cells in fetal liver populations cultured initially in the absence of SCM and the survival of some eosinophil and megakaryocyte colony-forming cells in similar cultures of adult marrow cells. The results do not support the hypothesis that GM-CSF and EPO compete for a common pool of uncommitted progenitor cells. On the contrary, the data indicate that GM-CSF und EPO are able to collaborate in stimulating the proliferation of some erythropoietic cells. Furthermore, purified GM-CSF appears to be able to support temporarily the survival and/or initial proliferation of at least some cells forming erythroid, eosinophil and megakaryocyte colonies, even though GM-CSF is unable to stimulate the formation of colonies of these types.     

Release of erythropoietin from macrophages by treatment with silica

An erythropoietic stimulating factor (ESF) can be shown to be released from preincubated macrophage-containing cell suspensions from mice by the macrophage-specific, cytotoxic agent, silica. A concentrated silica treated spleen cell supernatant containing ESF is shown to cause a dose dependent increase in ⁵⁹ Fe incorporation into red blood cells using the in vivo polycythemic mouse bioassay. The ESF from the same supernatant can also be neutralized by anti-erythropoietin. A second concentrated supernatant fractionated using wheat germ lectin-Sepharose 6MB and compared to either unfractionated or fractionated step 111 erythropoietin (Ep), tested in vitro using the erythroid colony-forming technique and 12-day fetal liver as target cells, indicates parallelism of all linear dose-response lines. This, together with the in vivo data, strongly suggests that the ESF released from macrophages treated with silica is, in fact, Ep. Substituting Ca²⁺ ions for fetal calf serum in the preincubation procedure results in the same activity being released compared to the presence of 1% or 20% fetal calf serum.     

The opposing actions in vivo on murine myelopoiesis of purified preparations of lactoferrin and the colony stimulating factors

The actions of purified iron-saturated human lactoferrin (LF), purified preparations of human MiaPaCa colony stimulating factor-1 (CSF-1), and recombinant murine interleukin-3 (IL-3) were evaluated in vivo in mice. Studies in vitro were compared at lowered (5%), as well as at normal incubator (20%), oxygen (O2) tension because of the potentially greater physiologic relevance of in vitro studies performed at lowered O2 tension. The results demonstrate that 1) increased release of granulocyte-macrophage colony stimulating factor (GM-CSF) in vitro from pokeweed mitogen stimulated mouse spleen cells and from human mononuclear blood cells occurred at lowered O2 tension, and that human mononuclear blood leukocytes were more sensitive to the LF-induced suppression of GM-CSF release when cells were cultured at 5%, compared to 20%, O2 tension; 2) LF administered intravenously (IV) to mice pretreated with sublethal intraperitoneal dosages of Cytoxan decreased the cycling status of marrow and spleen granulocyte-macrophage (CFU-GM), erythroid (BFU-E-2 and BFU-E-1) and multipotential (CFU-GEMM) progenitor cells and the absolute numbers of these progenitors; these effects were most noticeable if care was taken to deplete endotoxin from the LF samples prior to testing LF in vivo and if the control medium was endotoxin free; 3) endotoxin-depleted LF decreased the cycling status of marrow and spleen CFU-GM, BFU-E, and CFU-GEMM and the numbers of these progenitors in the marrows of mice previously untreated with Cytoxan; these effects were most apparent when assessment of progenitor cells and their cycling rates were evaluated in vitro at lowered (5%) O2 tension; 4) purified natural human CSF-1 increased the absolute numbers of marrow CFU-GM and the cycling status of marrow CFU-GM and CFU-GEMM in mice pretreated with LF; and 5) purified recombinant murine IL-3 stimulated proliferation of day 8 and day 12 CFU-S (colony forming unit-spleen) in mice not previously treated with Cytoxan. These results substantiate the in vivo myelosuppressive effects of LF on CFU-GM and extend these effects to erythroid and multipotential progenitor cells, provide evidence that human CSF-1 has an in vivo action in mice, and confirm the studies of others showing that IL-3 stimulates the proliferation of CFU-S in vivo.     

Interleukine-17-induced inhibitory effect on late stage murine erythroid bone marrow progenitors

Recent studies have shown that the T cell-derived cytokine, interleukin-17 (IL-17), stimulates hematopoiesis, specifically granulopoiesis inducing expansion of committed and immature progenitors in bone marrow. Our previous results pointed to its role in erythropoiesis too, demonstrating significant stimulation of BFU-E and suppression of CFU-E growth in the bone marrow from normal mice. As different sensitivities of erythroid and myeloid progenitor cells to nitric oxide (NO) were found, we considered the possibility that the observed effects of IL-17 were mediated by NO. The effects of recombinant mouse IL-17, NO donor (sodium nitroprusside - SNP) and two NO synthases inhibitors (L-NAME and aminoguanidine) on erythroid progenitor cells growth, as well as the ability of IL-17 to induce nitric oxide production in murine bone marrow cells, were examined. In addition, we tested whether the inhibition of CFU-E colony formation by IL-17 could be corrected by erythropoietin (Epo), the principal regulator of erythropoiesis. We demonstrated that IL-17 can stimulate low level production of NO in murine bone marrow cells. Exogenously added NO inhibited CFU-E colony formation, whereas both L-NAME and aminoguanidine reversed the CFU-E suppression by IL-17 in a dose-dependent manner. The inhibition of CFU-E by IL-17 was also corrected by exposure to higher levels of Epo. The data obtained demonstrated that at least some of the IL-17 effects in bone marrow related to the inhibition of CFU-E, were mediated by NO generation. The fact that Epo also overcomes the inhibitory effect of IL-17 on CFU-E suggests the need for further research on their mutual relationship and co-signalling.     

Stimulation of embryonic mouse limb bud mesenchymal cell growth by peptide growth factors

The possible role of peptide growth factors in mammalian intrauterine cell growth has been investigated using primary cultures of undifferentiated mesenchymal cells from 11-day mouse embryo limb buds. When grown as monolayer cultures, proliferation is greatly favored by high cell densities. In medium containing 0.2% serum, purified epidermal growth factor (EGF), fibroblast growth factor (FGF), multiplication stimulating activity (MSA), insulin, and somatomedin-C (Sm-C) do not increase cell growth, but a 30-40,000 molecular weight component of mouse fetal liver conditioned medium is stimulatory. On the other hand, when limb bud cells are grown as high density or micromass cultures, a method which better approximates in vivo growth conditions, all of the purified growth factors tested stimulate cell growth significantly. These growth factors have additive effects when used in combination, the best stimulation being observed with liver medium (10% v/v), EGF (10 ng/ml), FGF (200 ng/ml), and either insulin (1 microgram/ml) or Sm-C (20 ng/ml). We conclude that the response of limb bud cells to growth stimulation is influenced by the manner in which the cells are cultured and that at least four different growth factors are required for optimal in vitro proliferation. One of these, the active component of liver medium, appears to be a previously uncharacterized growth factor.     

Nude mice bearing human CSF-producing tumor: analysis of hemopoietic factor(s) acting on primitive stem cells

Previously, we serially transplanted tumors that produced colony-stimulating factor (CSF) into nude mice, who developed marked granulocytosis along with tumor growth; their leukocyte counts reaching approximately one million per cu mm. The numbers of CFU-GM, CFU-E, CFU-Meg, CFU-S and BFU-E were increased in nude mice bearing CSF-producing tumor. We here report that tumor-conditioned medium (TCM) derived from the CSF-producing tumors had colony-stimulating activity (CSA) and burst-promoting activity (BPA) when normal murine spleen cells as well as normal human bone marrow cells were the target cells. The activity of TCM supported multilineage colony formation in 5-fluorouracil (5-FU)-treated mouse spleen cells, in which only the primitive population of stem cells was reserved. No interleukin-3 (IL-3) activity was detected in TCM when assayed using the IL-3 dependent cell lines. We conclude that the factor in TCM acts on pluripotent stem cells and on the early progenitor stage of various cell lineages. It is distinct from IL-3.     

Proliferative effects of purified granulocyte colony-stimulating factor (G-CSF) on normal mouse hemopoietic cells

When granulocyte colony-stimulating factor (G-CSF), purified to homogeneity from mouse lung-conditioned medium, was added to agar cultures of mouse bone marrcw cells, it stimulated the formation of small numbers of granulocytic colonies. At high concentrations of G-CSF, a small proportion of macrophage and granulocyte-macrophage colonies also developed. G-CSF stimulated colony formation by highly enriched progenitor cell populations obtained by fractionation of mouse fetal liver cells using a fluorescence-activated cell sorter, indicating that G-CSF probably acts directly on target progenitor cells. Granulocytic colonies stimulated by G-CSF were small and uniform in size, and at 7 days of culture were composed of highly differentiated cells. Studies using clonal transfer and the delayed addition of other regulators showed that G-CSF could directly stimulate the initial proliferation of a large proportion of the granulocvte-macrophage progenitors in adult marrow and also the survival and/or proliferation of some multipotential, erythroid, and eosinophil progenitors in fetal liver. However, G-CSF was unable to sustain continued proliferation of these cells to result in colony formation. When G-CSF was mixed with purified granulocyte-macrophage colony-stimulating factor (GM-CSF) or macrophage colony-stimulating factor (M-CSF), the combination stimulated the formation by adult marrow cells of more granulocyte-macrophage colonies than either stimulus alone and an overall size increase in all colonies. G-CSF behaves as a predominantly granulopoietic stimulating factor but has some capacity to stimulate the initial proliferation of the same wide range of progenitor cells as that stimulated by GM-CSF.     

The effect of erythropoietin on the mature burst forming unit erythroid in mice

The aim of the study was to further delineate the erythropoietin (Ep) dependence of the mature Burst Forming Unit-Erythroid - BFU-E(d4). Experiments were performed in normal and polycythemic CBA mice. BFU-E(d4) were determined by means of the methylcellulose culture technique. It was demonstrated that in plethoric mice the number of BFU-E(d4) is reduced from 9 000/femur and 30 000/spleen found in normal mice to less than 1 000/femur and 2 000/spleen on day 6 post-hypoxia. The number of BFU-E(d4) remained low both in the bone marrow and spleen in mice with posthypoxic polycythemia between days 6 and 11 post-hypoxia. When exogenous Ep was injected into the plethoric mice the number of BFU-E(d4) increased after 24 h both in the bone marrow and spleen. In Ep stimulated polycythemic mice the CFU-E:BFU-E(d4) ratio did not achieve normal values, indicating that although Ep stimulation increased the number of BFU(d4), the number of CFU-E produced per BFU-E(d4) was lower than in normal nonpolycythemic mice. The results obtained indicate that BFU-E(d4) population size depends on the effect of Ep on differentiation and proliferation of erythroid committed precursors.     

Erythropoietin responses and physical characterization of erythroid progenitor cells in Rauscher virus infected BALB/c mice.

Infection of BALB/c mice with Rauscher leukemia virus (RLV) gives rise to pronounced erythrocytopoiesis manifesting in splenomegaly and is associated with progressive development of anemia. In the spleen erythroid colony forming units (CFU-E) increase exponentially up to 800-fold that of normal levels by the third week of infection. In vitro these CFU-E are dependent on erythropoietin for colony formation, their erythropoietin requirements being higher than that of CFU-E from normal mice. Numbers of CFU-E in spleen and degree of splenomegaly in anemic RLV infected mice were also shown to be modified by red blood cell transfusion, but progression of the disease was not stopped. Erythroid burst forming units (BFU-E) were also responsive to erythropoietin. However, a small proportion of cells also formed BFU-E colonies at concentrations which did not support growth of normal marrow BFU-E. When compared to normal, CFU-E found in RLV-infected spleen have similar velocity sedimentation rates. However, buoyant density separation of leukemic spleen cells indicated that CFU-E were more homogeneous (modal density 1.0695 g/cm3) than CFU-E from normal spleen. Analysis of physical properties of CFU-E and the nonhemoglobinized erythroblast-like cells, which accumulate in the spleen showed that they differed mainly in their distribution of cell diameter. Our findings show that erythroid progenitor cells in RLV infected mice are responsive to erythropoietin in vitro. Also in vivo erythropoiesis appears to be under control of erythropoietin but other factors which lead to progression of RLV disease apparently exist. Most proerythroblast-like cells, which are characteristic of this disease, apparently lack the potential to form colonies and may be more mature than CFU-E.     

Segregation of mouse hemopoietic progenitor cells using the monoclonal antibody,YBM/42

A rat monoclonal antibody, YBM/42, directed against mouse leukocyte common antigen, was used for the analysis and separation of hemopoietic progenitor cells from mouse bone marrow and fetal liver. Cells were fractionated on a FACS-II cell sorter and the resulting subpopulations examined for their morphology and ability to form colonies in agar (for day 7 colonies) and methylcellulose (for day 2 erythroid clones). The antibody bound to all leukocytes, including blast cells and day 7 hemopoietic progenitor cells (day 7 colony forming cells, CFC), but not to erythrocytes or nucleated erythroid cells. This antibody can be used to advantage to enrich for early progenitor cells from mouse fetal liver, in which the majority of cells (70%) are nucleated erythroid cells. In day 12 fetal liver, approximately 10% of all cells bind this antibody strongly and, of these approximately 70% are blast cells. Contained within this positive population are 95% of all day 7 CFC. In the most enriched fraction about 20% of the cells formed day 7 colonies. This represents a 25-fold enrichment over unsorted fetal liver. The negative fractions contain 94% of all cells forming erythroid clones (≥8 cells) on day 2 of culture (day 2 CFU-E). In the most enriched fraction, 20% of the cells are day 2 CFU-E. Day 7 CFC can therefore be well separated from day 2 CFU-E, with good recovery of both cell types, by use of a single label. Day 7 colony forming cells were classified as granulocyte (G-CFC), macrophage (M-CFC), mixed granulocyte/macrophage (GM-CFC), pure erythroid (E), or mixed erythroid (E_mix). A high enrichment for multipotential cells is achieved and constitues 3–5% of cells in the most enriched fraction. Most types of day 7 CFC could not be separated with YMB/42, but GM-CFC and M-CFC exhibit a broader distribution than the other CFC with regard to fluorescence intensity. This implicit heterogeneity in GM-CFC and M-CFC is further substantiated by the finding that myeloid progenitors in the different FACS fractions also share a differential reactivity to different sources of growth factors.     

Stimulation of the synthesis of collagenase activator protein in cartilage by a factor present in synovial-conditioned medium

We have purified a low molecular weight protein from medium conditioned by calf synovium with physical and biological properties similar to the leukocyte cytokine interleukin 1 (IL-1). The factor is active in stimulating the synthesis (three- to fivefold) of collagenase activator protein (CAP) by the surface (1-2 mm) of articular cartilage while CAP synthesis in the deeper zones of articular cartilage is not affected. Recombinant mouse IL-1 and commercially available purified human IL-1 are also capable of stimulating cartilage to synthesize and secrete CAP. The synthesis of other proteins, including collagenase, appeared to be unaffected by either the synovial factors or the human and mouse IL-1.     

The effect of interleukin-17 on hematopoietic cells and cytokine release in mouse spleen

To evaluate whether the response of hematopoietic cells to interleukin-17 (IL-17) depends on the tissue microenvironment in which hematopoiesis occurs, the influence of recombinant mouse IL-17 on spleen hematopoietic cells and cytokine release was assessed in normal mice in vitro and in vivo. In vitro, IL-17 did not significantly affect the growth of granulocyte-macrophage (CFU-GM) and erythroid (BFU-E and CFU-E) derived colonies. A single injection of IL-17 in vivo exhibited stimulatory effects on hematopoietic cells from both granulocytic and erythroid lineages. The increased number of metamyelocytes 48 h after treatment imply to the IL-17-induced stimulation of granulopoiesis. The number of BFU-E was increased at 24 h, while the number of CFU-E increased 6 h and 24 h after treatment. Since the same treatment in the bone marrow decreased the number of CFU-E, it may be concluded that the local microenvironment plays an important role in IL-17-mediated effects on CFU-E. IL-17 increased the release of IL-6 both in vitro and in vivo, but showed tendency to suppress the constitutive secretion of IL-10 by spleen cells. Our results suggest the complexity of target cell response and interplay of secondary induced cytokines by IL-17 in different hematopoietic organs.