The essential role of the intestinal microbiota in facilitating acute inflammatory responses

The restoration of blood flow, i.e., reperfusion, is the treatment of choice to save viable tissue following acute ischemia of a vascular territory. Nevertheless, reperfusion can be accompanied by significant inflammatory events that limit the beneficial effects of blood flow restoration. To evaluate the potential role of the intestinal microbiota in facilitating the development of tissue injury and systemic inflammation, germ-free and conventional mice were compared in their ability to respond to ischemia and reperfusion injury. In conventional mice, there was marked local (intestine) and remote (lung) edema formation, neutrophil influx, hemorrhage, and production of TNF-alpha, KC, MIP-2, and MCP-1. Moreover, there was an increase in the concentration of serum TNF-alpha and 100% lethality. In germ-free mice, there was no local, remote, or systemic inflammatory response or lethality after intestinal ischemia and reperfusion and, in contrast to conventional mice, germ-free animals produced greater amounts of IL-10. Similar results were obtained after administration of LPS, i.e., little production of TNF-alpha or lethality and production of IL-10 after LPS in germ-free mice. Blockade of IL-10 with Abs induced marked inflammation and lethality in germ-free mice after ischemia and reperfusion or LPS administration, demonstrating that the ability of these mice to produce IL-10 was largely responsible for their "no inflammation" phenotype. This was consistent with the prevention of reperfusion-associated injury by the exogenous administration of IL-10 to conventional mice. Thus, the lack of intestinal microbiota is accompanied by a state of active IL-10-mediated inflammatory hyporesponsiveness.     

The balance between the production of tumor necrosis factor-alpha and interleukin-10 determines tissue injury and lethality during intestinal ischemia and reperfusion

A major goal in the treatment of acute ischemia of a vascular territory is to restore blood flow to normal values, i.e. to "reperfuse" the ischemic vascular bed. However, reperfusion of ischemic tissues is associated with local and systemic leukocyte activation and trafficking, endothelial barrier dysfunction in postcapillary venules, enhanced production of inflammatory mediators and great lethality. This phenomenon has been referred to as "reperfusion injury" and several studies demonstrated that injury is dependent on neutrophil recruitment. Furthermore, ischemia and reperfusion injury is associated with the coordinated activation of a series of cytokines and adhesion molecules. Among the mediators of the inflammatory cascade released, TNF-alpha appears to play an essential role for the reperfusion-associated injury. On the other hand, the release of IL-10 modulates pro-inflammatory cytokine production and reperfusion-associated tissue injury. IL-1beta, PAF and bradykinin are mediators involved in ischemia and reperfusion injury by regulating the balance between TNF-alpha and IL-10 production. Strategies that enhance IL-10 and/or prevent TNF-alpha concentration may be useful as therapeutic adjuvants in the treatment of the tissue injury that follows ischemia and reperfusion.     

The required role of endogenously produced lipoxin A4 and annexin-1 for the production of IL-10 and inflammatory hyporesponsiveness in mice

The appropriate development of an inflammatory response is central for the ability of a host to deal with any infectious insult. However, excessive, misplaced, or uncontrolled inflammation may lead to acute or chronic diseases. The microbiota plays an important role in the control of inflammatory responsiveness. In this study, we investigated the role of lipoxin A4 and annexin-1 for the IL-10-dependent inflammatory hyporesponsiveness observed in germfree mice. Administration of a 15-epi-lipoxin A4 analog or an annexin-1-derived peptide to conventional mice prevented tissue injury, TNF-alpha production, and lethality after intestinal ischemia/reperfusion. This was associated with enhanced IL-10 production. Lipoxin A4 and annexin-1 failed to prevent reperfusion injury in IL-10-deficient mice. In germfree mice, there was enhanced expression of both lipoxin A4 and annexin-1. Blockade of lipoxin A4 synthesis with a 5-lipoxygenase inhibitor or Abs against annexin-1 partially prevented IL-10 production and this was accompanied by partial reversion of inflammatory hyporesponsiveness in germfree mice. Administration of BOC-1, an antagonist of ALX receptors (at which both lipoxin A4 and annexin-1 act), or simultaneous administration of 5-lipoxygenase inhibitor and anti-annexin-1 Abs, was associated with tissue injury, TNF-alpha production, and lethality similar to that found in conventional mice. Thus, our data demonstrate that inflammatory responsiveness is tightly controlled by the presence of the microbiota and that the innate capacity of germfree mice to produce IL-10 is secondary to their endogenous greater ability to produce lipoxin A4 and annexin-1.     

Regulation of Staphylococcus epidermidis-induced IFN-gamma in whole human blood: the role of endogenous IL-18, IL-12, IL-1, and TNF

Interleukin 12 (IL-12) and IL-18 act synergistically to stimulate interferon gamma (IFN-gamma) production; moreover, IL-1 and tumor necrosis factor (TNF) may also augment IFN-gamma synthesis. We have investigated the relative contributions of these cytokines in the production of IFN-gamma and TNF by the Gram-positive bacterium Staphylococcus epidermidis, using the specific cytokine inhibitors IL-18 binding protein (IL-18BP), IL-1 receptor antagonist (IL-1Ra), anti-IL-12 antibodies (anti-IL-12 Ab), and TNF binding protein. Inhibition of caspase-1 reduced IFN-gamma and IL-1beta levels (by 80 and 67%, respectively) when heat-killed S. epidermidis was added to whole human blood cultures. IL-18BP reduced S. epidermidis-induced IFN-gamma (77% maximal suppression). In contrast, blocking IL-1 receptors by IL-1Ra had no effect on IFN-gamma production. Blocking endogenous IL-12 and TNF reduced IFN-gamma production by 69 and 36%. S. epidermidis-induced TNF-alpha was inhibited by IL-18BP and IL-1Ra, but not anti-IL-12 Ab, whereas IL-8 production was unaffected by any of the specific cytokine blocking agents. In conclusion, S. epidermidis stimulates IFN-gamma which is IL-18, IL-12 and TNF-dependent, but IL-1 independent.     

Inhibition of IL-6, TNF-alpha, and cyclooxygenase-2 protein expression by prostaglandin E2-induced IL-10 in bone marrow-derived dendritic cells

Several endogenously produced mediators, including cytokines such as IL-6, IL-10, and TNF-alpha and prostanoids such as prostaglandin E(2) (PGE(2)), regulate dendritic cell (DC) function and contribute to immune homeostasis. In this study, we report that exogenous PGE(2) enhances the production of IL-10 from bone marrow-derived DC (BM-DC). IL-6, but not TNF-alpha, release is enhanced by PGE(2) in the presence of anti-IL-10, suggesting that endogenous IL-10 masks PGE(2)-induced IL-6. Furthermore, both exogenous IL-10 and PGE(2) inhibit LPS-induced IL-6 and TNF-alpha, whereas selective inhibition of cyclooxygenase-2 (COX-2) or addition of anti-IL-10 causes the reverse effects. Exogenous IL-10, but not IL-6, dose-dependently suppresses COX-2 protein expression and PGE(2) production, and TNF-alpha does not reverse this effect. In contrast, anti-IL-10 up-regulates prostanoid production by LPS-stimulated BM-DC. Taken together, our results show that in response to PGE(2), BM-DC produce IL-10, which in turn down-regulates their own production of IL-6-, TNF-alpha-, and COX-2-derived prostanoids, and plays crucial roles in determining the BM-DC pro-inflammatory phenotype.     

Immune complex-induced lung and dermal vascular injury. Differing requirements for tumor necrosis factor-alpha and IL-1.

Vascular injury has been induced in rat lung and dermis after deposition of IgG immune complexes (BSA-anti-BSA complexes). By the use of antibodies to TNF-alpha and IL-1 and employment of the IL-1R antagonist, the requirements for these cytokines have been evaluated. In lung, both TNF-alpha and IL-1 were required for the full expression of injury. Protection was related to the dose of cytokine-blocking agent employed and was directly correlated with diminished tissue content of myeloperoxidase (MPO). In the dermis, IL-1 was required for the full expression of injury; blocking of IL-1 protected the tissue from injury in a manner that correlated with reduced MPO content. However, anti-TNF-alpha provided no protection against dermal vascular injury and failed to reduce MPO content. In contrast, the local injection of either TNF-alpha or IL-1 beta enhanced IgG immune complex-induced dermal vascular injury, proportional to the increased tissue content of MPO, indicating that the rat dermis is reactive to both cytokines. By the employment of immunohistochemical approaches, it was demonstrated that, after deposition of immune complexes, TNF-alpha and IL-1 were readily demonstrated in lung macrophages, whereas in the dermis IL-1, but not TNF-alpha, was present in a granular pattern within interstitial cells. The immunohistochemical data are consistent with the patterns of protective effects of anti-IL-1, IL-1R antagonist and anti-TNF-alpha in the two organs. As expected, blocking of TNF-alpha or IL-1 had no protective effects on acute lung injury produced by systemic C activation after i.v. infusion of the cobra venom factor. The data suggest fundamental differences in the requirements for cytokines in lung and dermal vascular injury after deposition of IgG immune complexes.     

Expression and contribution of endogenous IL-13 in an experimental model of sepsis

IL-13 has been shown to exert potent anti-inflammatory properties. In this study, we elucidated the functional role of endogenous IL-13 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that the level of IL-13 increased in tissues including liver, lung, and kidney, whereas no considerable increase was found in either peritoneal fluid or serum after CLP. Immunohistochemically, IL-13-positive cells were Kupffer cells in liver, alveolar macrophages in lung, and epithelial cells of urinary tubules in kidney. IL-13 blockade with anti-IL-13 Abs significantly decreased the survival rate of mice after CLP from 53% to 14% on day 7 compared with control. To determine the potential mechanisms whereby IL-13 exerted a protective role in this model, the effects of anti-IL-13 Abs on both local and systemic inflammation were investigated. Administration of anti-IL-13 Abs did not alter the leukocyte infiltration and bacterial load in the peritoneum after CLP but dramatically increased the neutrophil influx in tissues after CLP, an effect that was accompanied by significant increases in the serum levels of aspartate transaminase, alanine transaminase, blood urea nitrogen, and creatinine. Tissue injury caused by IL-13 blockade was associated with increases in mRNA and the protein levels of CXC chemokines macrophage inflammatory protein-2 and KC as well as the CC chemokine macrophage inflammatory protein-1alpha and the proinflammatory cytokine TNF-alpha. Collectively, these results suggest that endogenous IL-13 protected mice from CLP-induced lethality by modulating inflammatory responses via suppression of overzealous production of inflammatory cytokines/chemokines in tissues.     

IL-10 inhibits cytokine production by activated macrophages

IL-10 inhibits the ability of macrophage but not B cell APC to stimulate cytokine synthesis by Th1 T cell clones. In this study we have examined the direct effects of IL-10 on both macrophage cell lines and normal peritoneal macrophages. LPS (or LPS and IFN-gamma)-induced production of IL-1, IL-6, and TNF-alpha proteins was significantly inhibited by IL-10 in two macrophage cell lines. Furthermore, IL-10 appears to be a more potent inhibitor of monokine synthesis than IL-4 when added at similar concentrations. LPS or LPS- and IFN-gamma-induced expression of IL-1 alpha, IL-6, or TNF-alpha mRNA was also inhibited by IL-10 as shown by semiquantitative polymerase chain reaction or Northern blot analysis. Inhibition of LPS-induced IL-6 secretion by IL-10 was less marked in FACS-purified peritoneal macrophages than in the macrophage cell lines. However, IL-6 production by peritoneal macrophages was enhanced by addition of anti-IL-10 antibodies, implying the presence in these cultures of endogenous IL-10, which results in an intrinsic reduction of monokine synthesis after LPS activation. Consistent with this proposal, LPS-stimulated peritoneal macrophages were shown to directly produce IL-10 detectable by ELISA. Furthermore, IFN-gamma was found to enhance IL-6 production by LPS-stimulated peritoneal macrophages, and this could be explained by its suppression of IL-10 production by this same population of cells. In addition to its effects on monokine synthesis, IL-10 also induces a significant change in morphology in IFN-gamma-stimulated peritoneal macrophages. The potent action of IL-10 on the macrophage, particularly at the level of monokine production, supports an important role for this cytokine not only in the regulation of T cell responses but also in acute inflammatory responses.     

IL-1 alpha beta blockade prevents cartilage and bone destruction in murine type II collagen-induced arthritis, whereas TNF-alpha blockade only ameliorates joint inflammation.

Anti-TNF-alpha treatment of rheumatoid arthritis patients markedly suppresses inflammatory disease activity, but so far no tissue-protective effects have been reported. In contrast, blockade of IL-1 in rheumatoid arthritis patients, by an IL-1 receptor antagonist, was only moderately effective in suppressing inflammatory symptoms but appeared to reduce the rate of progression of joint destruction. We therefore used an established collagen II murine arthritis model (collagen-induced arthritis(CIA)) to study effects on joint structures of neutralization of either TNF-alpha or IL-1. Both soluble TNF binding protein and anti-IL-1 treatment ameliorated disease activity when applied shortly after onset of CIA. Serum analysis revealed that early anti-TNF-alpha treatment of CIA did not decrease the process in the cartilage, as indicated by the elevated COMP levels. In contrast, anti-IL-1 treatment of established CIA normalized COMP levels, apparently alleviating the process in the tissue. Histology of knee and ankle joints corroborated the finding and showed that cartilage and joint destruction was significantly decreased after anti-IL-1 treatment but was hardly affected by anti-TNF-alpha treatment. Radiographic analysis of knee and ankle joints revealed that bone erosions were prevented by anti-IL-1 treatment, whereas the anti-TNF-alpha-treated animals exhibited changes comparable to the controls. In line with these findings, metalloproteinase activity, visualized by VDIPEN production, was almost absent throughout the cartilage layers in anti-IL-1-treated animals, whereas massive VDIPEN appearance was found in control and sTNFbp-treated mice. These results indicate that blocking of IL-1 is a cartilage- and bone-protective therapy in destructive arthritis, whereas the TNF-alpha antagonist has little effect on tissue destruction.     

Role of interleukin-6 (IL-6) in the pathogenesis of combined radiation/thermal injuries

Combined injury such as whole body gamma-irradiation at the dose of 7 Gy+10% body surface full-thickness thermal burn were investigated in (CBA x C57BL6)F1 mice. Enhanced level of IL-6 in mice serum at 6-24 hs following combined injury was established. The potential inhibiting activity of pentoxifylline (POF) as an influence to IL-6 levels, and measure of several acute phase response signs has been evaluated. It was established, that single POF injection don't modify IL-6 production, don't change leukocytosis and early hyperfermentemia (as alaninaminotransferase levels indicated). But serum albumin content was increased after preliminary POF administration to mice with combined injury. On the other side, mouse anti-IL-6 monoclonal antibodies administration increased 30-days animal survival up to 60% while 100% lethality was registered in untreated mice. Possible anti-inflammatory inactivity reasons of POF under combined injury conditions are discussed in this article, and important role of IL-6 hyperproduction in combined injury outcomes burden is suggested.     

Natural and recombinant human IL-1 receptor antagonists block the effects of IL-1 on bone resorption and prostaglandin production

Inhibitory factors towards IL-1 have been identified in the urine and in the supernatants of human monocyte cultures and have been shown to act as receptor antagonists. We have investigated whether a natural inhibitor purified from human urine (uIL-1ra) and a recombinant molecule expressed using the gene for an IL-1 antagonist isolated from monocytes (rIL-1ra) can alter responses to human rIL-1 alpha in organ cultures of fetal rat long bones and neonatal mouse calvariae. The two preparations probably contained similar or identical molecules, because an antibody to rIL-1ra reacted with uIL-1ra by Western blot analysis. uIL-1ra and rIL-1ra specifically blocked stimulation of bone resorption by rIL-1 in both culture systems, as well as the increase in PGE2 production in cultured calvariae. Resorptive effects of parathyroid hormone and TNF-alpha were not blocked. The uIL-1ra preparation had some intrinsic resorbing activity, but on gel chromatography this appeared in fractions that eluted earlier than uIL-1ra. Concentration ratios of rIL-1ra to rIL-1 as low as 10 could block the resorptive response of fetal rat long bones, whereas concentration ratios of 100 to 1000 were required to block IL-1 action on neonatal mouse calvariae. The inhibitory effects appeared to be competitive, because increasing concentrations of IL-1 overcame the block of bone resorption in both systems and the inhibition of PGE2 production in calvariae.     

Immunomodulatory effects of glycine on LPS-treated monocytes: reduced TNF-alpha production and accelerated IL-10 expression.

Cytokines play a pivotal role in the pathogenesis of septic shock. Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) stimulate the progression of septic shock whereas the anti-inflammatory cytokine IL-10 has counterregulative potency. The amino acid glycine (GLY) has been shown to protect against endotoxin shock in the rat by inhibiting TNF-alpha production. In the current study we investigated the role of GLY on lipopolysaccharide (LPS) -induced cell surface marker expression, phagocytosis, and cytokine production on purified monocytes from healthy donors. GLY did not modulate the expression of HLA-DR and CD64 on monocytes, whereas CD11b/CD18 expression (P<0.05) and E. coli phagocytosis (P<0.05) decreased significantly. GLY decreased LPS-induced TNF-alpha production (P<0.01) and increased IL-10 expression of purified monocytes. Similarly, in a whole blood assay, GLY reduced TNF-alpha (P<0.0001) and IL-1beta (P<0.0001) synthesis and increased IL-10 expression (P<0.05) in a dose-dependent manner. The inhibitory effects of GLY were neutralized by strychnine, and the production of IL-10 and TNF-alpha was augmented by anti-IL-10 antibodies. Furthermore, GLY decreased the amount of IL-1beta and TNF-alpha-specific mRNA. Our data indicate that GLY has a potential to be used as an additional immunomodulatory tool in the early phase of sepsis and in different pathophysiological situations related to hypoxia and reperfusion.     

Ligand-activation of the adenosine A2a receptors inhibits IL-12 production by human monocytes

Adenosine (ADO) exerts potent anti-inflammatory and immunosuppressive effects. In this paper we address the possibility that these effects are partly mediated by inhibition of the secretion of IL-12, a proinflammatory cytokine and a major inducer of Th1 responses. We demonstrate that 5'-N-ethylcarboxamidoadenosine (NECA), a nonspecific ADO analogue, and 2-p-(2-carbonyl-ethyl)phenylethylamino-5'-N-ethylcarboxamidoadenos ine (CGS-21680), a specific A2a receptor agonist, dose-dependently inhibited, in whole blood ex vivo and monocyte cultures, the production of human IL-12 induced by LPS and Stapholococcus aureus Cowan strain 1. However, the A1 receptor agonist 2-Chloro-N6-cyclopentyladenosine and the A3 receptor agonists N6-Benzyl-NECA and 1-deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-N-methyl-be ta-d -ribofuranuronamide expressed only weak inhibitory effects. On the other hand, NECA and CGS-21680 dose-dependently potentiated the production of IL-10. The differential effect of these drugs on monocyte IL-12 and IL-10 production implies that these effects are mediated by A2a receptor signaling rather than by intracellular toxicity of ADO analogue's metabolites. Moreover, CGS-21680 inhibited IL-12 production independently of endogenous IL-10 induction, because anti-IL-10 Abs failed to prevent its effect. The selective A2a antagonist 8-(3-Chlorostyryl) caffeine prevented the inhibitory effect of CGS-21680 on IL-12 production. The phosphodiesterase inhibitor Ro 20-1724 dose-dependently potentiated the inhibitory effect of CGS-21680 and, furthermore, Rp-cAMPS, a protein kinase A inhibitor, reversed the inhibitory effect of CGS-21680, implicating a cAMP/protein kinase A pathway in its action. Thus, ligand activation of A2a receptors simultaneously inhibits IL-12 and stimulates IL-10 production by human monocytes. Through this mechanism, ADO released in excess during inflammatory and ischemic conditions, or tissue injury, may contribute to selective suppression of Th1 responses and cellular immunity.     

IL-23 induces human osteoclastogenesis via IL-17 <Emphasis Type="Italic">in vitro</Emphasis>, and anti-IL-23 antibody attenuates collagen-induced arthritis in rats

This study demonstrates that IL-23 stimulates the differentiation of human osteoclasts from peripheral blood mononuclear cells (PBMC). Furthermore, in vivo blockade of endogenous IL-23 activity by treatment with anti-IL-23 antibody attenuates collagen-induced arthritis in rats by preventing both inflammation and bone destruction. IL-23 induced human osteoclastogenesis in cultures of PBMC in the absence of osteoblasts or exogenous soluble-receptor activator of NF-kappaB ligand (RANKL). This IL-23-induced osteoclastogenesis was inhibited by osteoprotegerin, anti-IL-17 antibody, and etanercept, suggesting that RANKL, IL-17, and TNF-alpha are involved. In addition, we found the ratio of production levels of IL-17 to those of IFN-gamma from activated human T cells was elevated at 1 to 10 ng/ml IL-23. The inductive effect of IL-17 and the inhibitory effect of IFN-gamma on osteoclastogenesis indicate that the balance of these two cytokines is particularly important. We also demonstrated that IL-23 administered at a later stage significantly reduced paw volume in rats with collagen-induced arthritis, in a dose-dependent manner. Furthermore, anti-IL-23 antibody reduced synovial tissue inflammation and bone destruction in these rats. These findings suggest that IL-23 is important in human osteoclastogenesis and that neutralizing IL-23 after onset of collagen-induced arthritis has therapeutic potential. Thus, controlling IL-23 production and function could be a strategy for preventing inflammation and bone destruction in patients with rheumatoid arthritis.     

IL-10 and TGF-beta redundantly protect against severe liver injury and mortality during acute schistosomiasis

The cytokines IL-10 and TGF-beta regulate immunity and inflammation. IL-10 is known to suppress the extent of hepatic damage caused by parasite ova during natural infection with Schistosoma mansoni, but the role of TGF-beta is less clear. Cytokine blockade studies in mice revealed that anti-IL-10R mAb treatment during acute infection modestly increased cytokine production and liver damage, whereas selective anti-TGF-beta mAb treatment had marginal effects. In contrast, mice administered both mAbs developed severe hepatic inflammation, with enlarged, necrotic liver granulomas, cachexia, and >80% mortality by 8 wk postinfection, despite increased numbers of CD4(+)CD25(+)Foxp3(+) T regulatory cells. Blocking both IL-10 and TGF-beta at the onset of egg production also significantly increased IL-4, IL-6, TNF, IFN-gamma, and IL-17 production and markedly increased hepatic, peritoneal, and splenic neutrophilia. In contrast, coadministration of anti-IL-10R and TGF-beta mAbs had little effect upon parasite ova-induced intestinal pathology or development of alternatively activated macrophages, which are required to suppress intestinal pathology. This suggests that inflammation is controlled during acute S. mansoni infection by two distinct, organ-specific mechanisms: TGF-beta and IL-10 redundantly suppress hepatic inflammation while intestinal inflammation is regulated by alternatively activated macrophages.     

Intraepithelial NK cell-derived IL-13 induces intestinal pathology associated with nematode infection

IL-13 is a Th2-derived cytokine associated with pathological changes in asthma and ulcerative colitis. Moreover, it plays a major role in the control of gut nematode infection and associated immunopathology. The current paradigm is that these effects are due to T cell-derived IL-13. We show in this study that an innate source of IL-13, the intraepithelial NK cell, is responsible for the disruption of intestinal tissue architecture and induction of goblet cell hyperplasia that characterizes infection with the intestinal helminth Trichinella spiralis. IL-13 or IL-4Ralpha (but not IL-4) null mice failed to induce intestinal pathology. Unexpectedly, SCID and athymic mice developed the same pathology found in immunocompetent mice following infection. Moreover, immunodeficient mice expressed IL-13 in the intestine, and abnormal mucosal pathology was reduced by in vivo administration of a soluble IL-13 antagonist. IL-13 expression was induced in non-T intraepithelial CD3- NK cells. Epithelial cells expressed the IL-13 signaling receptor, IL-13Ralpha1, and after infection, IL-4Ralpha. Furthermore, the soluble IL-13 decoy receptor IL-13Ralpha2, which regulates IL-13 responses, was also induced upon infection. These data provide the first evidence that intestinal tissue restructuring during helminth infection is an innate event dependent on IL-13 production by NK cells resident in the epithelium of the intestine.     

Exacerbation of granuloma formation in IL-1 receptor antagonist-deficient mice with impaired dendritic cell maturation associated with Th2 cytokine production

Dendritic cell (DC) maturation at the site of inflammation and migration into draining lymph nodes is fundamental to initiate Ag-specific immune responses. Although several proinflammatory cytokines, including IL-1, are known to promote DC maturation in vitro, their contributions to DC activation and migration within peripheral inflamed tissue compartments are not yet fully understood. We show here that endogenous IL-1 receptor antagonist (IL-1ra) controls the activation state of liver-recruited DCs and their migration in a Propionibacterium acnes-induced murine granulomatous liver disease model. After P. acnes treatment, formation of portal tract-associated lymphoid tissue was conversely impaired in IL-1ra-deficient mice. IL-1ra-deficient mice developed hepatic granulomas within 3 days after P. acnes administration and showed a more pronounced granuloma formation than wild-type mice. Although sinusoidal granulomas contained numerous CD11c+ DCs at day 7, expressions of CCR7, IL-12p40 by these DCs were dramatically decreased in IL-1ra-deficient mice, suggesting aberrant DC maturation and sinusoid portal migration in the absence of endogenous IL-1ra. This was accompanied with enhanced intrahepatic Th2 cytokine production and severe hepatocellular damage. Thus, hepatocyte-derived IL-1ra may control optimal activation and migration of inflammatory DCs within the liver and thereby determine the local immune responses in granulomatous liver disease.     

Evaluation of TNF-alpha and IL-1 blockade in collagen-induced arthritis and comparison with combined anti-TNF-alpha/anti-CD4 therapy

We have evaluated the effects of anti-TNF-alpha, anti-IL-1, and combined anti-TNF-alpha/anti-CD4 therapy in collagen-induced arthritis. Blockade of TNF-alpha or IL-1 before disease onset delayed, but did not prevent, the induction of arthritis. When treatment was initiated after onset of arthritis, anti-TNF-alpha, anti-IL-1beta, and anti-IL-1R (which blocks IL-1alpha and IL-1beta) were all found to be effective in reducing the severity of arthritis, with anti-IL-1R and anti-IL-1beta showing greater efficacy than anti-TNF-alpha. Anti-IL-1beta was equally as effective as anti-IL-1R, indicating that IL-1beta plays a more prominent role than IL-1alpha in collagen-induced arthritis. An additive effect was observed between anti-TNF-alpha and anti-IL-1R in the prevention of joint erosion and in normalization of the levels of serum amyloid P. Combined anti-TNF-alpha/anti-CD4 therapy also caused normalization of serum amyloid P levels. The therapeutic effect of anti-TNF-alpha plus anti-CD4 was comparable to that of anti-TNF-alpha plus anti-IL-1R, suggesting that combined anti-TNF-alpha/anti-CD4 therapy prevents both TNF-alpha- and IL-1-mediated pathology. Anti-TNF-alpha treatment reduced IL-1beta expression in the joint and, conversely, anti-IL-1beta treatment reduced TNF-alpha expression. Combined anti-TNF-alpha/anti-CD4 treatment almost completely blocked the expression of IL-1beta, thereby confirming the ability of this form of combination therapy to prevent IL-1ss-mediated pathology.