Reprogramming of lipopolysaccharide-primed macrophages is controlled by a counterbalanced production of IL-10 and IL-12

We studied the potential role of a cytokine regulatory mechanism(s) in LPS-dependent reprogramming and modulation of TNF-alpha and nitric oxide (NO) responses in mouse peritoneal macrophages. Reciprocal regulation of TNF-alpha and NO production by LPS-primed and LPS-stimulated macrophages was found to be dependent on the presence of soluble secretory products released by the cells during the initial LPS priming interaction. Pretreatment of naive macrophages with different mouse recombinant cytokines such as rIL-10, rIL-12, and rIFN-gamma dose dependently and differentially regulated subsequent LPS-induced production of TNF-alpha, IL-6, and NO by cytokine-primed cells. Analysis of IL-12 and IL-10 levels present in culture supernatants of LPS-primed and LPS-stimulated macrophages revealed a high degree of correlation between the profiles of TNF-alpha and IL-12 as well as NO and IL-10. Furthermore, LPS priming of macrophages in the presence of anti-IL-12-neutralizing mAb attenuated TNF-alpha responses while at the same time up-regulated NO production. In contrast, neutralization of endogenous IL-10 with anti-IL-10 mAb resulted in considerable TNF-alpha response at LPS priming doses under conditions that would otherwise strongly inhibit TNF-alpha production. We also found that the initial LPS priming of naive macrophages differentially and dose dependently regulates expression of mRNAs for IL-10, IL-12, and IFN-gamma in LPS-primed macrophages. Collectively, our data provide experimental support for the hypothesis that a cytokine regulatory network, most probably autocrine, tightly controls the reciprocal modulation of TNF-alpha and NO responses in LPS-primed macrophages.     

Pattern of cytokines and pharmacomodulation in sepsis induced by cecal ligation and puncture compared with that induced by endotoxin

The production of tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IL-6 and their pharmacomodulation were evaluated in a model of polymicrobial sepsis induced in mice by cecal ligation and puncture (CLP) and were compared with the effects of endotoxin (lipopolysaccharide [LPS]) treatment. LPS levels rose as early as 1 h after CLP and increased further after 2 and 21 h. TNF-alpha was detectable in serum, spleen, liver, and lungs during the first 4 h, with a peak 2 h after CLP. IL-1 beta was measurable in serum after 24 h, and levels increased significantly in spleen and liver 4 and 8 h after CLP. IL-6 levels increased significantly in serum throughout the first 16 h after CLP. These cytokines were detectable after LPS injection, with kinetics similar to those after CLP but at a significantly higher level. To cast more light on the differences between these two animal models of septic shock, we studied the effects of different reference drugs. Pretreatment with dexamethasone (DEX); ibuprofen (IBU), an inhibitor of cyclooxygenase; and NG-nitro-L-arginine, an inhibitor of nitric oxide synthase, significantly reduced survival, while chlorpromazine (CPZ) and TNF did not affect it. Only the antibiotics and pentoxifylline significantly increased survival in mice with CLP. However, CPZ and DEX protected the mice from LPS mortality. On inhibiting TNF-alpha with DEX, CPZ, or pentoxifylline, survival was reduced, unchanged, and increased, respectively, and on increasing TNF-alpha with IBU and TNF, survival was decreased or unchanged, respectively, suggesting that the modulation of this cytokine does not play a significant role in sepsis induced by CLP, unlike treatment with LPS. The negative effects of IBU and N(G)-nitro-L-arginine suggest a protective role by prostaglandins and nitric oxide in sepsis induced by CLP.     

Subcellular localization of G-proteins in primary-cultured mouse preadipocytes and adipocytes

We studied the pathways of macrophage response to lipopolysaccharide (LPS). When mouse macrophages pre-exposed to LPS were restimulated with this agent, reduced tumour necrosis factor-alpha (TNF-alpha) responses (desensitization/endotoxin tolerance) were accompanied by increased (priming) nitric oxide (NO) responses. Priming was also inducible with recombinant interferon-beta (IFN-beta). The requirement of TNF-alpha biosynthesis in the LPS-induced priming was also suggested by the observation that both anti-TNF-alpha serum and pentoxifylline inhibited this effect. However, addition of mouse recombinant TNF-alpha (mrTNF-alpha) did not enhance the priming induced by LPS or IFN-beta, and preincubation with mrTNF-alpha alone, or in association with other cytokines produced by macrophages (interleukin-1 beta, interleukin-6, or leukaemia inhibitory factor), did not induce a priming effect. We found however, that pentoxifylline, which blocked the priming, also decreased the level of membrane-bound TNF-alpha. Furthermore, exposure to compound BB-3103 (a metalloproteinase inhibitor that blocks the processing of membrane-bound TNF-alpha yielding to the secreted cytokine) enhanced the priming effect, the expression of membrane TNF-alpha and the specific binding of LPS. These observations suggest that the membrane form of TNF-alpha is involved in the interaction of LPS with a receptor required for LPS-induced priming.     

The biphasic mRNA expression pattern of bovine interleukin-8 in Pasteurella haemolytica lipopolysaccharide-stimulated alveolar macrophages is primarily due to tumor necrosis factor alpha

Pasteurella haemolytica serotype 1 is the bacterial agent responsible for the pathophysiological events associated with bovine pneumonic pasteurellosis. Our previous studies support a role for the lipopolysaccharide (LPS) from P. haemolytica in the induction of proinflammatory cytokines. One of the pathological hallmarks of bovine pneumonic pasteurellosis is an influx of neutrophils into the alveolar spaces. This pronounced influx suggests the local production of a chemotactic factor(s) such as interleukin-8 (IL-8). In the context of the lung, the alveolar macrophage appears to be the major producer of IL-8, a proinflammatory cytokine with potent neutrophil chemotactic activity. By using Northern blot analysis, we have examined the kinetics of IL-8 mRNA expression in P. haemolytica LPS-stimulated bovine alveolar macrophages and found that 1 ng of LPS per ml induces maximal expression of IL-8 mRNA. The results also indicate a biphasic time course expression pattern in which IL-8 mRNA levels peak between 1 and 2 h in the first phase and between 16 and 24 h in the second phase (P < 0.01). In addition, monospecific polyclonal antibodies were used to demonstrate the role of tumor necrosis factor alpha (TNF-alpha) in the second phase of IL-8 mRNA expression. Our findings support a role for P. haemolytica LPS and TNF-alpha in the induction of IL-8 from bovine alveolar macrophages.     

Somitogenesis: segmenting a vertebrate

OBJECTIVE: To evaluate the effect of gliclazide administration to NIDDM patients on 1) monocyte adhesion to cultured endothelial cells, 2) plasma cytokine and lipid peroxide levels, and 3) monocyte cytokine production. RESEARCH DESIGN AND METHODS: Poorly controlled glyburide-treated diabetic patients (n = 8) and healthy control subjects (n = 8) were recruited. At the beginning of the study, glyburide was replaced by an equivalent hypoglycemic dose of gliclazide. Serum and monocytes were isolated from blood obtained from control and diabetic subjects before and after 3 months of treatment with gliclazide. RESULTS: Plasma lipid peroxide levels and monocyte adhesion to endothelial cells are enhanced in NIDDM patients, and gliclazide administration totally reverses these abnormalities. Before gliclazide treatment, serum levels of cytokines did not differ in the control and the diabetic groups, with the exception of an enhancement of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL)-6 in NIDDM subjects. Basal and lipopolysaccharide (LPS)-stimulated monocyte production of interleukin-1 beta, IL-6, and IL-8 did not differ between the two groups. Furthermore, basal monocyte production of TNF-alpha was similar in the control and the diabetic groups, whereas a marked increase in the LPS-stimulated monocyte production of TNF-alpha was observed in the NIDDM group. Gliclazide treatment lowered LPS-stimulated TNF-alpha production by diabetic monocytes to levels similar to those observed in control subjects. CONCLUSIONS: Gliclazide administration to NIDDM patients inhibits the increased adhesiveness of diabetic monocytes to endothelial cells and reduces the production of TNF-alpha by these cells. These results suggest that treatment of NIDDM subjects with gliclazide may be beneficial in the prevention of atherosclerosis associated with NIDDM.     

Eicosapentaenoic acid potentiates the production of nitric oxide evoked by interleukin-1 beta in cultured vascular smooth muscle cells

Experiments were designed to determine whether the omega 3-unsaturated fatty acid eicosapentaenoic acid affects the production of nitric oxide evoked by interleukin-1 beta in cultured vascular smooth muscle cells. Incubation of cultured rat or human aortic smooth muscle cells with interleukin-1 beta evoked a time- and concentration-dependent release of nitrite, an oxidation product of nitric oxide. The exposure of cells to interleukin-1 beta in combination with eicosapentaenoic acid caused a significantly larger production of nitrite than that evoked by the cytokine alone. The potentiation by eicosapentaenoic acid was concentration-dependent. The production of nitrite evoked by equieffective concentrations of interleukin-1 beta in the presence and absence of eicosapentaenoic acid were inhibited to a similar extent by nitro L-arginine (an inhibitor of nitric oxide synthase), transforming growth factor beta 1, platelet-derived growth factorAB and thrombin. The addition of interleukin-1 beta-activated smooth muscle cells to suspensions of washed and indomethacin-treated platelets inhibited the aggregation caused by thrombin. The inhibitory effect was enhanced when the smooth muscle cells were exposed to the cytokine in the presence of eicosapentaenoic acid prior to the experiment. Smooth muscle cells exposed to interleukin-1 beta and eicosapentaenoic acid did not affect platelet aggregation in the presence of oxyhemoglobin or methylene blue. Untreated cells or cells exposed to the fatty acid alone did not have such effects. These observations suggest that eicosapentaenoic acid potentiates the production of nitric oxide evoked by interleukin-1 beta in vascular smooth muscle.     

Localization of mRNA for inflammatory cytokines in radicular cyst tissue by in situ hybridization, and induction of inflammatory cytokines by human gingival fibroblasts in response to radicular cyst contents

The expression of mRNA encoding the inflammatory cytokines interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha(TNF-alpha) have been examined in radicular cysts by in situ hybridization. Furthermore, the biological activity of the contents of radicular cysts (RCC) has been assayed by adding extracts of RCC to cultured human gingival fibroblasts (HGFs) and analyzing the culture medium for the release of inflammatory cytokines. In the epithelial layer, keratinocytes expressed all cytokine mRNAs examined at various levels. Basal layer cells expressed mRNA for each cytokine. In the subepithelial granulation tissue of the cysts, fibroblasts and macrophages expressed mRNA for IL-6, IL-8, IL-1beta and TNF-alpha mRNA at varying levels; especially clear expression of TNF-alpha and IL-1beta mRNA was detected on macrophages. The infiltrating lymphoid cells, largely composed of T cells and plasma cells, expressed these cytokine mRNAs, especially those encoding IL-6 and IL-8, at various levels. In vitro analysis indicated dose-dependent release of both IL-6 and IL-8 by HGFs in response to RCC. After heating to 100 degrees C for 10 min, RCC almost completely failed to stimulate IL-6 release from HGFs. Furthermore, anti-IL-1beta antibody (neutralization test) did not prevent the stimulation of IL-6 release by RCC. Significant amounts of IL-6 and IL-8 were detected in RCC in two cases, and a trace amount of IL-1beta was detected in one case. This study demonstrated the wide expression of mRNA encoding inflammatory cytokines in radicular cyst tissues, and RCC itself was capable of stimulating IL-6 and IL-8 production from HGFs.     

Production of tumor necrosis factor alpha and interleukin-6 by alveolar macrophages from patients with rheumatoid arthritis and interstitial pulmonary disease

The aim of this study was to measure the production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) by alveolar macrophages in patients with rheumatoid arthritis and interstitial lung disease (ILD). Rheumatoid arthritis patients diagnosed by ACR criteria (n = 8) with associated ILD documented by pulmonary function tests and high resolution computerized tomography scanning, and 12 healthy volunteers (6 smokers and 6 nonsmokers). We determined the spontaneous and induced production of bacterial lipopolysaccharides (LSP), TNF-alpha and IL-6 by alveolar macrophages obtained by bronchoalveolar lavage. The macrophages were isolated by Ficoll-Hypaque gradient centrifugation and plastic adherence and cultured in serum-containing medium (low endotoxin) in the presence and absence of LPS (100 ng/ml). TNF-alpha and IL-6 levels contents were determined in supernatants by ELISA. In the patient group both spontaneous and induced production of TNF-alpha were significantly higher than in controls (p < 0.01). Macrophages stimulated with LPS in patients with rheumatoid arthritis and ILD also released greater amounts of IL-6 than did those of the healthy controls. IL-6 spontaneous and induced production was significantly lower in smokers than in nonsmokers. TNF-alpha and IL-6 production in patients with rheumatoid arthritis and ILD, studied in bronchoalveolar lavage specimens reveals that alveolar macrophages are hyperreactive in these patients, who are possibly sensitized as a consequence of the inflammatory lung process inherent to the disease. Further study is needed to define the pathogenic role of these mediators.     

Macrophage inflammatory protein-1 alpha production in lipopolysaccharide-stimulated human adherent blood mononuclear cells is inhibited by the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine

The release of chemokines such as macrophage-inflammatory protein-1 alpha (MIP-1 alpha) from activated macrophages is a crucial step in cell recruitment necessary for establishing local inflammatory responses. To ascertain the importance of the L-arginine/nitric oxide (NO) pathway in LPS-induced MIP-1 alpha release, we stimulated human adherent PBMC with LPS in the presence of the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA). L-NMMA decreased LPS-induced MIP-1 alpha protein release (45.5% inhibition) and steady state levels of mRNA (48% inhibition) in adherent PBMC. The concentration of L-NMMA for inhibition of MIP-1 alpha release was dependent on the concentration of L-arginine in the cell culture medium, emphasizing the L-arginine-related action of the drug. Most of the MIP-1 alpha release was attributed to the activity of IL-1 and TNF, since coincubation of LPS-stimulated PBMC with IL-1R antagonist and TNF-binding protein abrogated LPS-induced MIP-1 alpha release (by 76.8%). Analysis of cytokine secretion revealed that, in addition to MIP-1 alpha, L-NMMA inhibited the release of mature IL-1 beta (by 70%) and TNF-alpha (by 53%). In contrast, release of macrophage chemoattractant protein-1 was unaffected; IL-10 was augmented (123.4%) by L-NMMA. In the presence of exogenous NO provided by NO donors, LPS-induced MIP-1 alpha release was enhanced. We concluded that endogenous NO acts as a mediator of inflammation. Since IL-10 is a potent anti-inflammatory cytokine, these data also suggest that L-NMMA acts as an anti-inflammatory agent by specifically altering the balance of pro- and anti-inflammatory cytokines released from LPS-stimulated human PBMC.     

Inhibition of IL-10 expression by IFN-gamma up-regulates transcription of TNF-alpha in human monocytes

Stimulation of human monocytes with LPS induces expression of multiple cytokines, including TNF-alpha, IL-1 beta, IL-6, and IL-10, IL-10 expression is delayed relative to that of TNF-alpha, IL-1 beta, and IL-6. Furthermore, IL-10 feedback inhibits expression of TNF-alpha, IL-1 beta, and IL-6, thus providing an efficient autocrine mechanism for controlling proinflammatory cytokine production in monocytes. The Th1-type lymphokine, IFN-gamma, markedly up-regulates TNF-alpha production in monocytes. However, the precise mechanism by which IFN-gamma mediates this effect is unknown. We examined the effects of IFN-gamma on IL-10 expression in LPS-stimulated monocytes, and the relationship between IL-10 and TNF-alpha production in these cells. LPS stimulation induced rapid, ordered expression of multiple cytokines. Steady-state mRNA levels for TNF-alpha increased rapidly, reached maximal levels by 2 to 3 h poststimulation, and then declined sharply. IL-1 beta and IL-6 mRNA levels also increased markedly following stimulation with LPS, but decreased more slowly than did TNF-alpha. Down-regulation of mRNA for TNF-alpha, IL-1 beta, and IL-6 coincided with a delayed and more gradual increase in IL-10 mRNA levels. Furthermore, neutralization of IL-10 with anti-IL-10 Abs prolonged TNF-alpha mRNA expression, and significantly increased net TNF-alpha production. IFN-gamma suppressed expression of IL-10 mRNA and protein in a dose-dependent manner. Moreover, inhibition of IL-10 production correlated with a marked increase in both the magnitude and duration of TNF-alpha expression. Thus, potentiation of TNF-alpha production by IFN-gamma in monocytes is coupled to inhibition of endogenous IL-10 expression.     

Peroxynitrite mediates IL-8 gene expression and production in lipopolysaccharide-stimulated human whole blood

Recent evidence indicates that free oxygen radicals, in particular hydroxyl radicals, may act as intracellular second messengers for the induction of IL-8, a potent chemoattractant and activator of neutrophil granulocytes. Here we report that peroxynitrite (ONOO-), formed by a reaction of nitric oxide (NO) with superoxide, mediates IL-8 gene expression and IL-8 production in LPS-stimulated human whole blood. The NO synthase inhibitors aminoguanidine and NG-nitro-L-arginine methyl ester (L-NAME) blocked IL-8 release by approximately 90% in response to LPS (1 microg/ml), but did not affect the production of IL-1beta or TNF-alpha. Both aminoguanidine and L-NAME blocked the induction of IL-8 mRNA by LPS. Authentic ONOO- (2.5-80 microM) augmented IL-8 mRNA expression and stimulated IL-8 release in a concentration-dependent manner, whereas the NO-releasing compounds, S-nitroso-N-acetyl-DL-penicillamine and sodium nitroprusside failed to induce cytokine production. Combination of the NO-generating chemicals with a superoxide-generating system (xanthine/xanthine oxidase) markedly increased IL-8 release. Enhanced ONOO- formation was detected in granulocytes, monocytes, lymphocytes, and plasma after challenge with LPS. Furthermore, pyrrolidine dithiocarbamate, an inhibitor of activation of nuclear factor-gammaB, markedly attenuated the induction of IL-8 mRNA expression and IL-8 release by either LPS or ONOO-. Our study identifies ONOO- as a novel signaling mechanism for IL-8 gene expression and suggests that inhibition of ONOO- formation or scavenging ONOO- may represent a novel therapeutic approach to inhibit IL-8 production that could lead to reduction of neutrophil accumulation and activation.     

In vitro IL-1 beta and TNF-alpha release from THP-1 monocytes in response to metal ions

OBJECTIVES: Previous studies have shown that biomaterials can activate macrophages to produce cytokines and promote an inflammatory response. Although the toxicity of many metal ions has been extensively investigated, little is known about the ability of these ions to alter cytokine release from macrophages. Yet the release of these ions from biomaterials has been well documented. Previous studies indicated that alterations in cytokine release might be expected because metal ions alter protein production in macrophages at sub-toxic concentrations. Thus, the hypothesis of this study was that metal ions can alter the secretion of cytokines from macrophages at sub-toxic concentrations. METHODS: The release of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) from macrophages was investigated when the macrophages were exposed to metal ions, with or without lipopolysaccharide (LPS), a component of dental plaque. Human THP-1 macrophages were exposed to ions of Ag, Au, Cu, Hg, and Ni for 24 h. In half of the cultures, LPS was added for the last 4 h. The release of IL-1 beta and TNF-alpha into the medium was measured using enzyme-linked immunosorbent assays. ANOVA and Tukey multiple comparison intervals were used to compare the various experimental conditions. RESULTS: None of the metal ions elevated the IL-1 beta or TNF-alpha levels after 24 h, but Ni ions significantly elevated the IL-1 beta and TNF-alpha levels after 72 h. With LPS added, Ag, Cu, and Ni significantly amplified the LPS-induced production of IL-1 beta but only Ni amplified the TNF-alpha response. These alterations in cytokine response occurred with metal ion concentrations which have been previously shown to be released from dental alloys in vitro and in vivo. SIGNIFICANCE: It appeared plausible that macrophage-cytokine mediated inflammatory responses may be altered by the presence of some metal ions in tissues, particularly Ni.     

Evidence for the involvement of interleukin 10 in the differential deactivation of murine peritoneal macrophages by prostaglandin E2

Among other effects, prostaglandins (PG) of the E series are known to inhibit several acute and chronic inflammatory conditions in vivo and proinflammatory cytokine production by activated macrophages in culture. The research presented here demonstrates that the inhibitory effect of PGE2 on tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) production by lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages involves IL-10. In a dose-dependent manner, PGE2 inhibits LPS-induced release of TNF-alpha and IL-6, but not of lactate or nitric oxide. The decrease in the level of these cytokines is inversely proportional to the increase in immunoreactive IL-10. This differential inhibitory effect of PGE2 is mimicked by agents that elevate intracellular levels of cAMP, but not cGMP. Neutralizing anti IL-10 antibody but not neutralizing antibodies against other macrophage secretory products (IL-6, leukemia inhibitory factor, and transforming growth factor beta [TGF-beta]), significantly reverse the potent inhibitory effect of PGE2. In vivo, the administration of PGE2 before LPS challenge significantly reduces circulating TNF-alpha and IL-6 levels. Anti-IL-10 antibody substantially enhanced the LPS-induced TNF-alpha and IL-6 levels in mice that received either LPS alone or LPS plus PGE2. These results suggest that the anti-inflammatory effect of PGE2 on mononuclear phagocytes is mediated in part by an autocrine feedback mechanism involving IL-10.     

Lipopolysaccharide and its analog antagonists display differential serum factor dependencies for induction of cytokine genes in murine macrophages

Monocytes/macrophages play a central role in mediating the effects of lipopolysaccharide (LPS) derived from gram-negative bacteria by the production of proinflammatory mediators. Recently, it was shown that the expression of cytokine genes for tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interferon-inducible protein-10 (IP-10) by murine macrophages in response to low concentrations of LPS is entirely CD14 dependent. In this report, we show that murine macrophages respond to low concentrations of LPS (相似文献   

Nitric oxide inhibits LPS-induced tumor necrosis factor synthesis in vitro and in vivo

The effect of nitric oxide (NO) on LPS-stimulated TNF-alpha synthesis has been studied in vitro and in vivo. The synthesis of TNF-alpha in J774 macrophages stimulated with LPS (0.1 microgram/ml) was increased in concentration-related fashion by NO synthase inhibitor L-NMMA (3-30-300 microM) and reduced by either L-arginine (3-30-300 microM) or the NO donor SIN-1 (1-10-100 microM). The level of TNF-alpha in the serum of LPS-challenged rats (6mg/kg/i.p.) was increased in animals pre-treated s.c. with L-NMMA (10 and 50mg/kg) and reduced in those given L-arginine (100 and 300mg/kg). These results show a negative feedback mechanism exhibited by NO on TNF-alpha synthesis suggesting an important regulatory link between NO and TNF-alpha in pathological processes.     

Suppressive effect of hepatitis B virus on the induction of interleukin-1 beta and interleukin-6 gene expression in the THP-1 human monocytic cell line

The major target organ for Hepatitis B Virus (HBV) is the liver, but extrahepatic sites including monocytes express receptors for HBV and may become infected. Therefore, we investigated the effect of HBV on the in vitro expression of interleukin-beta (IL-1 beta) and interleukin-6 (IL-6) by the monocytoid cell line THP-1, exposed to various stimuli (LPS, PMA or both). Nonstimulated THP-1 cells did not synthesize IL-1 beta and IL-6, even after in vitro exposure to HBV. LPS stimulation alone induced moderate secretion of both IL-1 beta and IL-6 (300 pg/ml). After induction of macrophage differentiation by PMA, THP-1 cells acquired adherence and expressed a higher level of IL-1 beta (up to 2 ng/ml) but did not synthesize IL-6. Treatment of THP-1 cells with PMA and LPS caused the highest production of both IL-1 beta and IL-6 (> 5ng/ml). In vitro exposure of PMA + LPS-stimulated THP-1 cells to HBV resulted in secretion of both HBsAg and preS2Ag which was maintained over 10 days of culture. Southern blot technique was used to study the state of HBV DNA in the cells. Hybridization of non-digested cellular DNA showed only high molecular weight HBV DNA forms. The HindIII restriction pattern revealed bands corresponding to large DNA fragments and the presence of bands at the 3.2 kb position. Under these conditions (PMA + LPS), HBV inhibited the production of IL-1 beta and IL-6 proteins and completely suppressed the IL-1 beta and IL-6 mRNA. Thus, our findings (i) strongly support a relationship between the state of cell differentiation and susceptibility of cells to HBV infection, and (ii) demonstrate that HBV exerts an inhibitory effect on the induction of IL-1 beta and IL-6 genes expression in monocytic THP-1 cells. These results suggest that HBV leads to a fall of pro-inflammatory cytokine production by monocytes/macrophages, which may contribute to impaired host immune response during infection.