Pathogenesis Of Anemia Of Chronic Disease Research Articles

СРАВНИТЕЛЬНЫЙ АНАЛИЗ СЕКРЕЦИИ ИНТЕРЛЕЙКИНА-6, ИНТЕРЛЕЙКИНА-1БЕТА, ИНТЕРЛЕЙКИНА-10, ФАКТОРА НЕКРОЗА ОПУХОЛИ-АЛЬФА, ИНТЕРФЕРОНА-ГАММА ПРИ РАЗЛИЧНЫХ ТИПАХ АНЕМИИ У ПАЦИЕНТОВ С ВИЧ-ИНФЕКЦИЕЙ

Aim. To compare the secretion of interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-1-beta, tumor necrosis factor-alpha (TNF-α), interferon-gamma (INF-γ) in patients with HIV infection with anemia of chronic disease (ACD), iron deficiency anemia (IDA), as well as their combination. To assess the effect of the studied cytokines on erythropoiesis in each of the studied types of anemia in this category of patients. Material and methods. 125 patients with HIV infection were examined: 101 with anemia (55 men, 46 women, 39.4±9.6 years), 24 patients with HIV infection without anemia (13 men, 11 women, mean age 37.6± 7.37 years). In accordance with the Van Santen and Worwood criteria, by determining the transferrin saturation index (TSI), ferritin concentrations, C-reactive protein (CRP), patients with anemia were divided into 3 groups: group 1 – 36 patients with ACD (19 men, 17 women, mean age 41.7±11.8 years), group 2 – 30 patients with a combination of ACD/IDA (18 men, 12 women, mean age 41.2±10 years), group 3 – 35 patients with IDA (18 men, 17 women, mean age 35.4±7.1 years). In all patients, the number of erythrocytes, the concentration of hemoglobin, ferritin, CRP, CNT, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), interleukin-1beta (IL-1β), interferon-gamma (INF-γ). For quantitative indicators, the arithmetic mean, standard error of the mean, and interquartile range (IQR) were calculated. Significance of differences between several unrelated groups was determined using the Kruskal-Wallis’s test. To assess the relationship between variables, the Spearman correlation coefficient I was calculated. Results. In the ACD group, the maximum concentration of IL-6 (36.6 [IQR, 11.5-51.1]) and IL-10 (21.6 [IQR, 11.4-28.8]) compared with the ACD/IDA group (IL-6 (9.1 [IQR, 5.1-11.4]), IL-10 (15.5 [IQR, (7.1-21.6)]), and IDA (IL- 6 (6.2 [IQR, 1.6–7.2]), IL-10 (8.6 [IQR, 3.9–9.3]) (p<0.05). In the groups of patients with ACD and ACD/IDA, the maximum and almost equal concentrations of TNF-α (15.2 [IQR,6.1-24.1] in the ACD group and 17.3[IQR,7.9-17.3] in the ACD/IDA group), IL-1β (16.7[IQR,4.7-28.9] in the ACD group and 19.2 [IQR,3.9-28.8] in the ACD/IDA group), INF-γ ( 62.6[IQR,4.6-85.3] in the ACD group and 58.3[IQR,8.5-37.5] in the ACD/IDA group), which were statistically significantly higher than the concentrations of these cytokines in patients with IDA and the control group. There were no significant differences in the concentrations of TNF-α, IL-1β, IL-10 and IFN-γ between patients with IDA and the control group. Significant moderate and strong negative correlations were found in the groups of patients with ACD and ACD/IDA between all studied cytokines, erythrocytes and hemoglobin. In the IDA group, the correlation coefficients between cytokines, erythrocytes, and hemoglobin are low or absent. Conclusions. In patients with HIV infection, a wide prevalence of ACD has been shown, especially in patients with immunodeficiency and in the late stages of the disease. ACD, unlike IDA, has a complex multicomponent pathogenesis. This study shows the importance of pro-inflammatory and inflammatory cytokines in the development of ACD in HIV patients, including due to their negative effect on erythropoiesis and hemoglobin synthesis. A working version of the classification of ACD (with a predominant iron deficiency, with impaired regulatory mechanisms of erythropoiesis, with insufficient production of erythropoietin) has been proposed. It is necessary to further study the pathogenesis of ACD in this category of patients to improve treatment.

Effect of Interleukin and Hepcidin in Anemia of Chronic Diseases.

Background Anemia of chronic disease (ACD) also termed as the anemia of inflammation has been found to be associated with inflammations, chronic infections, and cancers, particularly in old age. Recent studies revealed that interleukin-6 (IL-6), a proinflammatory cytokine, and hepcidin, an antimicrobial hepatic peptide, play a key role in ACD pathogenesis. Patients and Methods. The study included 40 subjects with chronic diseases and 40 normal subjects of the same age group. Red cell indices, levels of IL-6 and hepcidin, and iron profile were measured in all participants using Bayer ADVIA 120, VITROS 5600, Integrated System/2008, and ELISA assay, respectively. Results The level of hemoglobin was considerably less in patients of chronic diseases referred to as “cases” than the normal subjects or “controls” (8.7 ± 1.5 vs. 13.2 ± 0.9). Red blood corpuscle (RBC) count, hematocrit (HCT) level, serum iron, mean corpuscular hemoglobin concentration (MCHC), and serum total iron-binding capacity (TIBC) were found to be significantly lower in the cases as compared to controls (p < 0.001). Serum IL-6 and hepcidin levels were substantially higher in the cases than in the controls (p < 0.001). Serum IL-6 and hepcidin levels were substantially higher in the cases than in the controls (p < 0.001). Serum IL-6 and hepcidin levels were substantially higher in the cases than in the controls (Conclusion This study detected a significant increase in serum IL-6 and hepcidin levels in patients with ACD than the controls. These findings offer an insight into the role played by both cytokine and peptide in the pathogenesis of ACD and thus provide a rationale for future use of novel drugs inhibiting their effects on iron metabolism.

Interferon-gamma induced nitric oxide-mediated apoptosis of anemia of chronic disease in rheumatoid arthritis

Proinflammatory cytokines play a role in the pathogenesis of anemia of chronic disease (ACD), which is a common cause of anemia in rheumatoid arthritis (RA). Anemia in RA is associated with increased apoptosis of erythroid cells. However, there is unclear information on the mechanism of ACD in the disease. The purpose of this study is to investigate the role of cytokines on nitric oxide-mediated apoptosis in erythroid progenitor cells of ACD in RA patients. Erythroid progenitor cells from healthy subjects and RA patients with ACD were treated with cytokines like interleukin-1β, tumor necrosis factor-α, and interferon-γ at concentrations of 2, 20, and 40 ng/ml for 14 days. Cell viability and cell apoptosis were analyzed by trypan blue staining and flow cytometry, respectively. The results showed that the highest effect of cytokines on reduction cell viability and induction cell apoptosis was found in 20 ng/ml IFN-γ-treated cells of RA patients. In addition, IFN-γ showed significantly increased nitric oxide production and iNOS mRNA expression, which was measured by Griess assay and real-time PCR, respectively. The percentage of cell apoptosis and NO production was reduced after an inducible nitric oxide synthase inhibitor, SMT, treatment. In conclusion, IFN-γ could induce nitric oxide production-mediated apoptosis process, which might be involved in the pathogenesis of ACD in RA patients.

Role of BMP Signaling In the Anemia of Chronic Disease

AbstractAbstract 2043 Introduction:Anemia of chronic disease (ACD) describes anemia associated with diverse chronic inflammatory, infectious, or neoplastic processes. These conditions are frequently associated with increased circulating levels of inflammatory cytokines such as interleukin 6 (IL-6). IL-6 regulates expression of the hormone hepcidin, which inhibits the release of iron from hepatocytes, macrophages, and enterocytes into the circulation. In addition to IL-6, hepcidin gene expression is known to be transcriptionally regulated by bone morphogenetic protein (BMP) signaling. Hypothesis:We hypothesized that BMP signaling is required for the induction of hepcidin gene expression by IL-6 and plays a critical role in the pathogenesis of ACD. Methods:We used a turpentine-dependent model of ACD in mice. Mice were challenged with weekly subcutaneous injections of turpentine, which induces anemia in an IL-6 dependent manner. This model was studied to determine hepcidin gene expression and rescue ACD using BMP inhibition. Moreover, we examined hepcidin gene expression in zebrafish injected with Pseudomonas aeruginosa, and in transgenic zebrafish overexpressing human IL-6. The regulation of hepcidin gene expression was also studied in the human hepatocarcinoma cell line (HepG2). Results:Injections of mice with IL-6 (0.8 μg/g ip) increased hepatic hepcidin mRNA levels expression at 24 hours and decreased serum iron concentrations. Both effects were prevented by a small molecule BMP type I receptor kinase inhibitor, LDN-193189, or protein BMP antagonists. Weekly turpentine injections induced microcytic anemia after 3 weeks with a decrease in hemoglobin levels from 12.8±0.3 to 9.7±1.7 g/dL (*p<0.01). Concurrent treatment with LDN-193189 prevented turpentine-induced anemia and microcytosis (*p<0.01 for both). In mice challenged with turpentine for 6 weeks, treatment with LDN-193189, beginning after anemia was established at week 3, led to an increase in hemoglobin levels at week 6 (10.9±0.1 vs 9.5±0.2 g/dL, LDN193189 vs vehicle, respectively; *p<0.05).In zebrafish, microinjection with Pseudomonas aeruginosa or overexpression of human IL-6 induced hepatic hepcidin expression, an effect which was blocked by LDN-193189.Incubation of HepG2 cells with IL-6 (100 ng/ml) increased hepcidin mRNA levels 2 to 5 fold. Pretreatment with LDN-193189, or recombinant protein BMP antagonists such as noggin, abrogated the induction of hepcidin expression by IL-6. Incubation of HepG2 cells with BMP6 (2.5 to 10 ng/ml) modestly increased hepcidin mRNA levels. However, the combination of IL-6 and BMP6 synergistically increased hepcidin gene expression (*p<0.05). Conclusion:BMP signaling appears to play a critical role in the pathogenesis of anemia in a mouse ACD model. Our findings support the concept that BMP signaling is required for the induction of hepcidin gene expression by IL-6 in vitro and in vivo. Moreover, manipulation of BMP signaling represents a potentially novel therapeutic approach to the treatment of anemia associated with inflammation. Disclosures:Steinbicker:Deutsche Forschungsgemeinschaft DFG: Research Funding. Scadden:Fate Therapeutics: Consultancy, Equity Ownership, Patents & Royalties. Peterson:Massachusetts General Hospital Executive Committee on Research and NIDDK 1R01DK082971: Research Funding. Bloch:Massachusetts General Hospital Executive Committee on Research and NIDDK 1R01DK082971: Research Funding. Yu:Harvard Stem Cell Institute Seed Grant and the Howard Hughes Medical Institute Early Career Physician-Scientist Award: Honoraria, Research Funding; NHLBI 5K08HL079943: Research Funding.

Hepcidin expression in anemia of chronic disease and concomitant iron-deficiency anemia

Hepcidin is a key hormone governing mammalian iron homeostasis and may be directly or indirectly involved in the development of most iron deficiency/overload and inflammation-induced anemia. The objective of this study was to investigate the expression of hepcidin in anemia of chronic disease. To characterize serum hepcidin, iron and inflammatory indicators associated with anemia of chronic disease (ACD), we studied ACD, ACD concomitant iron-deficiency anemia (ACD/IDA), pure IDA and acute inflammation (AcI) patients and analyzed the associations between hepcidin levels and inflammation parameters in various types of anemia. Serum hepcidin levels in patient groups were statistically different, from high to low: ACD, AcI > ACD/IDA > the control > IDA. Serum ferritin levels were significantly increased in ACD and AcI patients but were decreased significantly in ACD/IDA and IDA. Elevated serum EPO concentrations were found in ACD, ACD/IDA and IDA patients but not in AcI patients and the controls. A positive correlation between hepcidin and IL-6 levels only existed in ACD/IDA, AcI and the control groups. A positive correlation between hepcidin and ferritin was marked in the control group, while a negative correlation between hepcidin and ferritin was noted in IDA. The significant negative correlation between hepcidin expression and reticulocyte count was marked in both ACD/IDA and IDA groups. All of these data demonstrated that hepcidin might play role in pathogenesis of ACD, ACD/IDA and IDA, and it could be a potential marker for detection and differentiation of these anemias.

Myelodysplasia and anemia of chronic disease in human tumor necrosis factor‐α transgenic mice

TNF-alpha is a pleitropic cytokine that expresses both pro- and anti-inflammatory activity and transgenic mice expressing human tumor necrosis factor-alpha (TNF-alpha) exhibit a progressive polyarthritis that models rheumatoid arthritis (RA). One of the common comorbidities of RA is anemia of chronic disease (ACD). The purpose of these experiments was to study the changes in the bone marrow and peripheral blood that accompany polyarthritis in TNF-alpha transgenic mice in an effort to better understand the pathogenesis of myelodysplasia and ACD. Polychromatic cytometry, hematology and serum cytokine analysis were used to study the pathogenesis of ACD in human TNF-alpha transgenic mice. Our hematological evaluation revealed a mild, compensated, microcytic hypochromic anemia, and monocytosis. In the bone marrow, we observed alterations in cell kinetics, decreased relative expression of transferrin receptor and increased apoptosis and cell death in several late precursor cell populations. Although significant levels of human TNF-alpha were found in the serum, neither change in serum murine erythropoietin nor any significant difference observed in serum levels of murine IL-beta, IL-5, IL-6, IL-10, IL-12(p70), IL-17, TNF-alpha, IFNgamma, GM-CSF, MIP-1alphaJE, MCP-5 was observed. Tg197 mice develop a compensated, microcytic, hypochromic anemia, and a functional iron deficiency by 9 weeks of age. Changes in peripheral blood are reflected in alterations in cell kinetics, transferrin receptor expression and markedly increased apoptosis and cell death in the bone marrow indicating that TNF-alpha may contribute to myelodysplasia in ACD. Moreover, since human TNF-alpha can interact only with murine TNFR1, our data suggest that TNFR1 may play an important role in the development of ACD.

Inflammatory Cytokine IL-1β Upregulates Hepcidin Expression in Human Hepatoma Cell Lines.

The anemia of chronic disease (ACD) is commonly observed in patients with inflammatory disorders, malignancies, and chronic infections. ACD is characterized by low serum iron concentration and elevated serum ferritin concentration. A number of previous findings suggest that impaired mobilization of iron from the reticuloendotherial system (RES), such as macrophages, and an inhibition of iron absorption from intestine contribute to ACD. However, the precise mechanisms for generating the conditions of ACD have long been unclear despite extensive investigations until hepcidin was recently found. Hepcidin was found as one of antimicrobial peptides, but hepcidin is now thought to be a key regulator in iron metabolism. Hepcidin inhibits iron absorption from enterocytes and iron efflux from RES, which have suggested that hepcidin could account for the pathogenesis of ACD. Some cytokines have also been shown to modulate iron metabolism in the condition of inflammation. Interleukin-6 (IL-6), one of inflammatory cytokines, has been reported to induce hepcidin production not only in vitro but also in vivo. However, it is not clear whether other cytokines have such effect or not. We, therefore, investigated the possibility that other inflammatory cytokines might have a regulatory effect on hepcidin expression. Because hepcidin is produced mainly by hepatocytes, we used human hepatoma-derived cell line HuH-7 cells and hepatoblastoma-derived cell line HepG2 cells. Cells are incubated with or without inflammatory cytokines, such as IL-1β, IL-6, tumor necrosis factor α (TNFα), and then total RNA was extracted. Quantitative RT-PCR was then performed, revealing that IL-1β upregulate hepcidin mRNA expression as well as IL-6, although TNFα down regulates hepcidin expression in both cell lines. We next investigated the dose-response effect of IL-1β and IL-6 on hepcidin mRNA expression. Strong induction of hepcidin mRNA by IL-1β was observed when cells were incubated with low concentrations of IL-1β (0.2 ng/ml), although much higher concentrations of IL-6 were needed for hepcidin mRNA upregulation. It was likely that the concentrations of IL-1β that needed for hepcidin upregulation were more physiological than those of IL-6. Since it has been reported that IL-1β induce IL-6 production in hepatocytes, there was a possibility that the effect of IL-1β on hepcidin mRNA expression was not direct but come from IL-6 induced by IL-1β. However, the manners of IL-6 mRNA induction and hepcidin mRNA induction by IL-1β stimulation were quite different when cells were incubated with IL-1β at the concentrations ranging from 0.1 to 10 ng/ml. Moreover, antibody against IL-6 did not inhibit the induction of hepcidin mRNA by IL-1β stimulation. Therefore, it is likely that the effect of IL-1β on hepcidin mRNA expression is independent from that of IL-6. We conclude that inflammatory cytokine IL-1β can induce hepcidin expression and might be a key cytokine in the condition of ACD as well as IL-6, and IL-1β might be more important than IL-6 in physiological situations.

Hepcidin and multiple myeloma related anemia

Multiple myeloma (MM) is a B cell lymphoproliferative disorder in which malignant plasma cells accumulate in the bone marrow and usually produce monoclonal immunoglobulin in excess. Interleukin-6 (IL-6), is known to be an essential survival factor of myeloma cells, high IL-6 levels being correlated with an adverse prognosis. IL-6 modulates the transcription of several liver-specific acute phase protein genes, including C-reactive protein and hepcidin. Anemia is one of the prominent features of MM, along with recurrent osteolytic lesions, bacterial infections and renal insufficiency. The current treatment strategies of MM related anemia are often inadequate and many patients rely on transfusions. Several causes have been implicated, but anemia of chronic disease (ACD) related to the inflammatory cytokines appears to be one of the main culprits. The pathogenesis of ACD had been poorly understood, but recently it has been shown that increased Il-6 upregulates the hepatic production of hepcidin, which, by binding to its cellular receptor, ferroportin, causes anemia by blocking iron export from enterocytes and macrophages. We hereby argue that by virtue of its biological characteristics, multiple myeloma should be an ideal clinical setting to test the role of hepcidin in the pathogenesis of ACD. Hepcidin levels should be higher in MM patients and might correlate with prognosis. Anemic MM patients should also be among those who would benefit mostly from hepcidin targeted therapies.

Effects of Hepcidin, Ferritin, and Iron Deprivation on Erythroid Colony Formation in Vitro.

The anemia of chronic disease (ACD) results from a combination of three pathologic processes. In ACD, a modest shortening of red cell survival creates an increased demand for red cell production, which is not met because of an impaired erythropoietic response and defects in reticuloendothelial iron mobilization and utilization. The impaired erythropoietic response, in turn, has two components: a blunted erythropoietin response, and an impaired response of erythroid progenitors to erythropoietin. Recombinant human erythropoietin (rhEPO) can reverse this impaired progenitor response in vitro, and can also correct ACD in patients. These processes have generally been considered effects of the cytokines which mediate the immune and inflammatory response, such as tumor necrosis factor, interleukin-1, and the interferons. It has recently been proposed that hepcidin, a mediator of innate immunity with the iron regulatory properties, is the factor responsible for ACD. If this is the case, then hepcidin should be able to induce the pathophysiologic mechanisms implicated in ACD. We therefore evaluated the effects of hepcidin and associated phenomena on human CFU-E colony formation in vitro. All CFU-E cultures were performed in plasma clots in serum-containing medium with rhEPO 1 U/mL. Hepcidin at concentrations 10 ng/mL -10 μg/mL had no effect on CFU-E colony formation. A number of studies have demonstrated that increased hepcidin message expression and protein production are strongly associated with increases in serum ferritin concentrations, and so the effect of added ferritin on erythroid colony formation was studied. Neither ferritin nor apo-ferritin 10 – 1000 ng/mL had inhibitory effects on CFU-E colony formation. The effect of iron deprivation on erythroid colony formation was evaluated with using desferrioxamine. Desferrioxamine 0.01mM decreased CFU-E colony formation to 60% of control values, while higher concentrations completely ablated colony growth. In summary, hepcidin does not appear to inhibit CFU-E colony formation directly or indirectly through ferritin. It may exert such an effect by decreasing availability of iron for erythropoiesis; however, such a finding would be difficult to reconcile with the observed clinical response of ACD to rhEPO, given that iron availability is typically a limiting factor in the erythropoietic response to rhEPO. The role of hepcidin in the overall pathogenesis of ACD remains to be fully determined.

Role of cytokines in the pathogenesis of anemia of chronic disease in rheumatoid arthritis.

The aim of our study was to evaluate the role of proinflammatory cytokines: tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), as well as the possible contribution of interleukin-10 (IL-10) in anemia of chronic disease (ACD) of rheumatoid arthritis (RA) patients. We measured the serum levels of TNFalpha, IL-1beta, and IL-6 in 105 anemic and 127 nonanemic RA patients. We also investigated the effects of the above cytokines on the development of burst-forming units-erythroid (BFUe) and colony-forming units-erythroid (CFUe) in bone marrow cultures. Anemic patients had significantly higher serum levels of TNFalpha, IL-1beta, and IL-6 compared to nonanemics. Serum IL-10 levels were low and there was no significant difference in IL-10 concentrations between anemic and nonanemic patients. Proinflammatory cytokines inhibited proliferation of BFUe and CFUe. IL-10 did not decrease the erythroid colony growth. Proinflammatory cytokines may play a role in the pathogenesis of ACD in RA patients. Low levels of IL-10 possibly contribute to the development of ACD.

Pathogenesis of the anemia of chronic disease: A cytokine‐mediated anemia

The anemia found in patients with chronic infectious, inflammatory and neoplastic disorders, known as the anemia of chronic disease (ACD), is one of the most common syndromes in medicine. A characteristic finding of the disorders associated with ACD is increased production of the cytokines which mediate the immune or inflammatory response, such as tumor necrosis factor, interleukin 1 and the interferons. All the processes involved in the development of ACD can be attributed to these cytokines, including shortened red cell survival, blunted erythropoietin response to anemia, impaired erythroid colony formation in response to erythropoietin and abnormal mobilization of reticuloendothelial iron stores. Improved understanding of the role played by cytokines in the pathogenesis of ACD may lead to the development of more specific therapy for this syndrome.

Chronic Exposure to Tumor Necrosis Factor In Vivo Preferentially Inhibits Erythropoiesis in Nude Mice

AbstractThe anemia of chronic disease (ACD) is associated with conditions in which macrophage activation occurs. Activated marrow macrophages suppress erythropoiesis in vitro and produce tumor necrosis factor (TNF). Therefore, we tested the effects of chronic in vivo exposure to TNF to determine if it was a candidate for a mediator of ACD. Nude mice were inoculated with Chinese hamster ovary (CHO) cells expressing the human TNF gene or with control cells containing the transfection vector alone. The TNF mice promptly became reticulocytopenie, and after 3 weeks their corrected reticulocytes were 2.6% ± 0.7% as compared with 7.3% ± 4% in control mice. The hematocrit at 3 weeks was 28.4% ± 1.7% in TNF mice as compared with 46% ± 0.8% in control mice. This anemia was also associated with low serum iron and normal iron stores and increased erythropoietin (Epo) levels. The TNF mice showed an absolute monocytosis with twice the number of circulating monocytes as control mice and had M-colony- stimulating factor (CSF) activity in their serum. The TNF mice also became mildly thrombocytopenic. Marrow CFU-E and BFU-E were profoundly decreased (1.2 ± 0.2 × 103v 8.6 ± 0.2 × 104 CFU-E per femur, and 6.5 ± 1 × 102v 8.5 ±0.2 × 104 BFU-E per femur). Splenic CFU-E and BFU-E were similarly depressed. In contrast, marrow CFU-GM and CFU-GEMM were not affected. The residual BFU-E in TNF mice were relatively resistant to TNF as compared with control mice. These data demonstrate that TNF preferentially inhibits erythropoiesis in vivo and may be important in the pathogenesis of ACD.

Chronic exposure to tumor necrosis factor in vivo preferentially inhibits erythropoiesis in nude mice

The anemia of chronic disease (ACD) is associated with conditions in which macrophage activation occurs. Activated marrow macrophages suppress erythropoiesis in vitro and produce tumor necrosis factor (TNF). Therefore, we tested the effects of chronic in vivo exposure to TNF to determine if it was a candidate for a mediator of ACD. Nude mice were inoculated with Chinese hamster ovary (CHO) cells expressing the human TNF gene or with control cells containing the transfection vector alone. The TNF mice promptly became reticulocytopenic, and after 3 weeks their corrected reticulocytes were 2.6% +/- 0.7% as compared with 7.3% +/- 4% in control mice. The hematocrit at 3 weeks was 28.4% +/- 1.7% in TNF mice as compared with 46% +/- 0.8% in control mice. This anemia was also associated with low serum iron and normal iron stores and increased erythropoietin (Epo) levels. The TNF mice showed an absolute monocytosis with twice the number of circulating monocytes as control mice and had M-colony-stimulating factor (CSF) activity in their serum. The TNF mice also became mildly thrombocytopenic. Marrow CFU-E and BFU-E were profoundly decreased (1.2 +/- 0.2 x 10(3) v 8.6 +/- 0.2 x 10(4) CFU-E per femur, and 6.5 +/- 1 x 10(2) v 8.5 +/- 0.2 x 10(4) BFU-E per femur). Splenic CFU-E and BFU-E were similarly depressed. In contrast, marrow CFU-GM and CFU-GEMM were not affected. The residual BFU-E in TNF mice were relatively resistant to TNF as compared with control mice. These data demonstrate that TNF preferentially inhibits erythropoiesis in vivo and may be important in the pathogenesis of ACD.