The Ron receptor promotes prostate tumor growth in the TRAMP mouse model.

The Ron receptor tyrosine kinase (TK) is overexpressed in many cancers, including prostate cancer. To examine the significance of Ron in prostate cancer in vivo, we utilized a genetically engineered mouse model, referred to as TRAMP mice, that is predisposed to develop prostate tumors. In this model, we show that prostate tumors from 30-week-old TRAMP mice have increased Ron expression compared with age-matched wild-type prostates. Based on the upregulation of Ron in human prostate cancers and in this murine model of prostate tumorigenesis, we hypothesized that this receptor has a functional role in the development of prostate tumors. To test this hypothesis, we crossed TRAMP mice with mice that are deficient in Ron signaling (TK-/-). Interestingly, TK-/- TRAMP+ mice show a significant decrease in prostate tumor mass relative to TRAMP mice containing functional Ron. Moreover, TK-/- TRAMP+ prostate tumors exhibited decreased tumor vascularization relative to TK+/+ TRAMP+ prostate tumors, which correlated with reduced levels of the angiogenic molecules vascular endothelial growth factor and CXCL2. Although Ron loss did not alter tumor cell proliferation, a significant decrease in cell survival was observed. Similarly, murine prostate cancer cell lines containing a Ron deficiency exhibited decreased levels of active nuclear factor-κB, suggesting that Ron may be important in regulating prostate cell survival at least partly through this pathway. In total, our data show for the first time that Ron promotes prostate tumor growth, prostate tumor angiogenesis and prostate cancer cell survival in vivo.

CXCR1 deficiency does not alter liver regeneration after partial hepatectomy in mice.

Previous studies have shown that CXC chemokines containing Glu-Leu-Arg (ELR) in their amino-terminus stimulate hepatocyte proliferation and liver regeneration after partial hepatectomy. These ELR+CXC chemokines bind to two receptors, CXCR1 and CXCR2. Previous work has shown that CXCR2 is involved in the proliferative effects of CXC chemokines. However, the function of CXCR1 during the regenerative response has not been studied. The aim of the current study was to investigate the role of CXCR1 in liver regeneration after partial hepatectomy. C57BL/6 (wild type) or CXCR1-/- mice were subjected to 70% partial hepatectomy or sham surgery and sacrificed on day 2 and 4 after operation. There were no significant differences in liver-to-body weight ratio or hepatocyte proliferation. The data suggest that CXCR1 does not mediate the proliferative effects of ELR+ CXC chemokines during liver regeneration after partial hepatectomy.

Potential role for IL-23 in hepatic ischemia/reperfusion injury.

IL-12 and IL-23 are related cytokines that share a p40 subunit. Our previous studies identified IL-12 as a primary initiator of the cytokine cascade induced after hepatic ischemia/reperfusion. Because those studies were conducted prior to the discovery of IL-23, it is not clear whether IL-12 or IL-23 is the relevant cytokine in this response. The current studies show that the antibodies used in our original study cross-react with IL-23. We also found that both IL-12 p35 and IL-23 p19 mRNA are expressed rapidly in the liver after ischemia/reperfusion. Finally, isolated Kupffer cells produced TNFalpha in response to IL-23, but not IL-12, suggesting that IL-23 may be the relevant initiator of the hepatic inflammatory response to ischemia/reperfusion.

Involvement of the neuropeptide substance P in lung inflammation induced by hepatic ischemia/reperfusion.

OBJECTIVE AND DESIGN: The purpose of this study was to examine the potential role of substance P in accumulation of neutrophils in the lung following hepatic ischemia/reperfusion. MATERIALS AND METHODS: Male C57BL/6 mice (8-10 weeks of age) were subjected to either sham surgery, partial hepatic ischemia with or without reperfusion, or intratracheal administration of saline or 1 ng substance P. Lung neutrophil accumulation was assessed by tissue content of myeloperoxidase. Activation of the transcription factor, NF-kappaB, was determined by electrophoretic mobility shift assay. Levels of substance P and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage (BAL) fluid was measured using enzyme-linked immunosorbent assays. RESULTS: Significant pulmonary neutrophil accumulation was observed just prior to hepatic reperfusion in association with increased BAL levels of substance P. Intratracheal administration of substance P resulted in a similar pattern of neutrophil accumulation which was associated with activation of NF-kappaB and increased BAL levels of the chemokine, MIP-2. CONCLUSIONS: The data suggest that hepatic ischemia causes substance P release in the lung which activates NF-kappaB leading to the production of MIP-2 and accumulation of neutrophils.

STAT4 is required for antibacterial defense but enhances mortality during polymicrobial sepsis.

The signal transducer and activator of transcription factor 4 (STAT4) pathway mediates the intracellular effects of interleukin-12 (IL-12), leading to the production of gamma interferon, induction of a T helper type 1 response, and increased natural killer cell cytotoxicity. The purpose of this study was to determine the role of the STAT4 pathway during polymicrobial peritonitis in the cecal ligation and puncture (CLP) model. CLP was performed on STAT4-deficient (STAT4(-/-)) and wild-type control (BALB/c) mice. At 4 h after CLP, STAT4(-/-) mice had significantly higher bacterial counts in the peritoneal lavage fluid, liver, and blood. This difference persisted for 18 h in the peritoneal lavage fluid and blood. Neutrophil migration to the site of infection and into remote tissues was unaffected. Despite higher bacterial counts locally and systemically, STAT4(-/-) mice had a lower mortality rate than BALB/c controls. In contrast, blockade of IL-12 in BALB/c mice was detrimental to host survival. A blunted serum IL-12 response at 18 h after CLP was exhibited in STAT4(-/-) mice. These results suggest several critical roles for the STAT4 pathway in the resolution of polymicrobial infections. Additionally, the disparate effects observed with IL-12 blockade and STAT4 deficiency on host survival suggest that IL-12 may activate alternate pathways promoting survival.

STAT4 and STAT6 regulate systemic inflammation and protect against lethal endotoxemia.

Members of the signal transducer and activator of transcription (STAT) family are transcription factors that mediate many of the effects of pro- and anti-inflammatory cytokines. The progressive systemic inflammatory response induced by endotoxin is mediated by overzealous cytokine production. Here we identify STAT4 and STAT6 as critical regulators of the systemic inflammatory response to endotoxin. Mice deficient for STAT4 or STAT6 were highly susceptible to lethal endotoxemia. In STAT4(-/-) mice, antibody blockade of IL-12 prevented mortality, suggesting that STAT4 confers protection, while another signaling pathway mediates the detrimental effects of IL-12. In STAT6(-/-) mice we observed dysregulated activation of the transcription factor NF-kappaB, resulting in augmented production of proinflammatory cytokines and chemokines. Furthermore, STAT6(-/-) mice displayed increased organ accumulation of leukocytes and significant hepatocellular injury. These findings demonstrate that STAT4 and STAT6 confer protection against endotoxin-induced death and that for STAT6 these protective effects occur through the regulation of NF-kappaB activation and subsequent production of proinflammatory cytokines and chemokines.

Regulation of experimental lung inflammation.

Acute lung inflammation is an important component of a number of pulmonary diseases, including acute respiratory distress syndrome (ARDS). Much has been learned about the manner in which various insults to lung, such as infection or trauma, bring about recruitment of neutrophils into alveoli and small airways, resulting in parenchymal damage and organ dysfunction. In this brief review, we discuss the endogenous mechanisms in which the lung regulates the acute inflammatory response in rats to intrapulmonary deposition of IgG immune complexes. Emphasis is given to the participation of the transcription factor, NF-kappaB, in the development of lung injury and the endogenous mediators which attempt to control the extent of lung inflammation by modulating the activation of NF-kappaB.

Augmented metalloproteinase activity and acute lung injury in copper-deficient rats.

Dietary copper is required for normal function of >30 mammalian enzyme systems. Copper deficiency causes a number of cardiovascular defects as well as impaired immune cell function. Little is known regarding the effects of copper deficiency on acute inflammatory responses, but this topic is relevant because many members of the Western population receive less than the recommended dietary allowance of copper. In the current studies, we investigated the effects of dietary copper deficiency on acute lung injury induced by intrapulmonary deposition of IgG immune complexes. Weanling male Long-Evans rats were fed diets either adequate (5.6 microg/g) or deficient (0.3 microg/g) in copper. IgG immune complex lung injury was greatly increased in copper-deficient rats as determined by lung vascular leakage of albumin and histopathology. However, no change was observed in either the lung content of tumor necrosis factor-alpha or lung neutrophil accumulation. Lungs from copper-deficient rats had much higher levels of matrix metalloproteinase (MMP)-2 and MMP-9 than did copper-adequate control animals. This increased activity was not attributable to alveolar macrophages or neutrophils. These data suggest that the augmented lung injury caused by copper deficiency is due to increased pulmonary MMP-2 and MMP-9 activity and not a generalized amplification of the inflammatory response.

Regulatory effects of eotaxin on acute lung inflammatory injury.

Eotaxin, which is a major mediator for eosinophil recruitment into lung, has regulatory effects on neutrophil-dependent acute inflammatory injury triggered by intrapulmonary deposition of IgG immune complexes in rats. In this model, eotaxin mRNA and protein were up-regulated during the inflammatory response, resulting in eotaxin protein expression in alveolar macrophages and in alveolar epithelial cells. Ab-induced blockade of eotaxin in vivo caused enhanced NF-kappaB activation in lung, substantial increases in bronchoalveolar lavage levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant (CINC), and increased MIP-2 and CINC mRNA expression in alveolar macrophages. In contrast, TNF-alpha levels were unaffected, and IL-10 levels fell. Under these experimental conditions, lung neutrophil accumulation was significantly increased, and vascular injury, as reflected by extravascular leak of (125)I-albumin, was enhanced. Conversely, when recombinant eotaxin was administered in the same inflammatory model of lung injury, bronchoalveolar lavage levels of MIP-2 were reduced, as was neutrophil accumulation and the intensity of lung injury. In vitro stimulation of rat alveolar macrophages with IgG immune complexes greatly increased expression of mRNA and protein for MIP-2, CINC, MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta. In the copresence of eotaxin, the increased levels of MIP-2 and CINC mRNAs were markedly diminished, whereas MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta expression of mRNA and protein was not affected. These data suggest that endogenous eotaxin, which is expressed during the acute lung inflammatory response, plays a regulatory role in neutrophil recruitment into lung and the ensuing inflammatory damage.

Exaggerated response to endotoxin in mice lacking the Duffy antigen/receptor for chemokines (DARC).

Duffy antigen/receptor for chemokines (DARC) is a promiscuous receptor for chemokines that is required for Plasmodium vivax infection of erythroid cells. This receptor is expressed by subsets of endothelial, as well as erythroid cells. Selection for protection from malaria infection resulted in an erythroid-specific defect, suggesting that DARC may play a critical role in endothelial biology. Mice with targeted disruption of this gene were generated, and the function of DARC in inflammation was explored. RNA from spleens of homozygous mutant mice lacked DARC transcripts, which were abundant in wild-type (+/+) and heterozygote (+/-) mice. DARC(-/-) mice lacked developmental abnormalities and were healthy at 1 year. Whereas hematologic parameters were within normal ranges, erythrocytes from nullizygous mice lacked CXC and CC chemokine-binding activity. Challenge with lipopolysaccharide resulted in significantly increased inflammatory infiltrates in lung and liver of nullizygous mice. These results suggest that DARC modulates the intensity of inflammatory reactions as a sink for chemokines. (Blood. 2000;96:1681-1684)

Reduced hepatic ischemia/reperfusion injury by IL-4: potential anti-inflammatory role of STAT6.

OBJECTIVE AND DESIGN: The ability of interleukin-4 (IL-4) to modulate activation of the transcription factors, NF-kappaB and STAT6, reduce proinflammatory cytokine expression and protect against liver injury induced by ischemia/reperfusion was assessed. MATERIALS AND SUBJECTS: C57BL/6 mice underwent 90 minutes of partial hepatic ischemia followed by 1 or 8 h of reperfusion with or without intravenous administration of 1 microg (0.5 microg just prior to ischemia, 0.5 microg at reperfusion) recombinant murine IL-4. Liver expression of TNFalpha mRNA was determined by RT-PCR. Activation of NF-kappaB and STAT6 in liver nuclear extracts was assessed by mobility shift assay. RESULTS: Hepatic ischemia/reperfusion increased hepatic expression of tumor necrosis factor-alpha (TNFalpha), induced significant neutrophil accumulation and liver injury. Treatment with IL-4 greatly suppressed liver TNFalpha mRNA expression, neutrophil accumulation and liver injury. IL-4 had no effect on liver NF-kappaB activation, but greatly increased the activation of STAT6. CONCLUSIONS: The data suggest that STAT6 activation by IL-4 may be responsible for the protective effects of this cytokine.

Obstructive jaundice impairs hepatic sinusoidal endothelial cell function and renders liver susceptible to hepatic ischemia/reperfusion.

BACKGROUND/AIMS: Obstructive jaundice is associated with increased surgical morbidity and mortality. While parenchymal injury has been defined in obstructive jaundice, the pathogenesis of hepatic sinusoidal endothelial cell injury in obstructive jaundice is unclear. The aims of this study were to investigate hepatic sinusoidal endothelial cell injury in obstructive jaundice by determining serum hyaluronic acid levels, purine nucleoside phosphorylase/alanine aminotransferase ratios, and hyaluronic acid elimination rate, and also to determine whether hepatic parenchymal cell injury in obstructive jaundice is induced more than in normal liver after hepatic ischemia/reperfusion. METHODS: Male Wistar rats underwent ligation and division of the common bile duct (obstructive jaundice group) or sham operation (Sham group). Serum hyaluronic acid levels and purine nucleoside phosphorylase/alanine aminotransferase ratios in both groups were examined at intervals up to 21 days after surgery. Hepatic blood flow, permeability, neutrophil accumulation, and hyaluronic acid elimination rates in both groups were measured 14 days after surgery. Changes in serum hyaluronic acid and alanine aminotransferase concentrations were determined after 15 min of hepatic ischemia followed by reperfusion. RESULTS: Serum hyaluronic acid levels remained elevated after bile duct ligation. Hepatic sinusoidal endothelial cell swelling was observed by electron microscopy, and hepatic permeability was increased 14 days after bile duct ligation in association with neutrophil accumulation. Hepatic blood flow in obstructive jaundice remained unchanged, but hyaluronic acid elimination capacity was less than that in the Sham group. After hepatic reperfusion, the disappearance rate of serum hyaluronic acid in obstructive jaundice was lower, and serum alanine aminotransferase levels were higher than those in the Sham group. CONCLUSIONS: Our findings suggest that obstructive jaundice impairs sinusoidal endothelial cells and that sinusoidal endothelial cell damage in association with sinusoidal deterioration during obstructive jaundice renders liver susceptible to ischemia/reperfusion relative to normal liver.

Regulation of liver inflammatory injury by signal transducer and activator of transcription-6.

Liver injury induced by hepatic ischemia/reperfusion is characterized by activation of the transcription factor NF-kappaB, increased production of tumor necrosis factor-alpha (TNFalpha), liver neutrophil accumulation, and hepatocellular damage. Exogenous administration of interleukin-4 (IL-4) or IL-13 was recently shown to regulate this inflammatory injury in association with activation of signal transducer and activator of transcription-6 (STAT6). The objective of the present study was to determine whether STAT6 was required for the regulation of liver inflammation by IL-4 and IL-13. Wild-type and STAT6 knockout mice underwent 90 minutes of hepatic ischemia followed by 8 hours of reperfusion. Hepatic ischemia/reperfusion in wild-type and STAT6 knockout mice significantly increased (P < 0.05) NF-kappaB activation, serum levels of TNFalpha, liver accumulation of neutrophils [measured by myeloperoxidase (MPO) content], and hepatocellular damage [measured by serum alanine aminotransferase (ALT)] compared to sham controls. In wild-type mice, activation of STAT6 was not observed after ischemia/reperfusion. Administration of 1 microg of IL-4 or IL-13 at reperfusion reduced serum TNFalpha, liver neutrophil accumulation, and hepatocellular injury in wild-type mice. Treatment with IL-4 or IL-13 had no effect on liver NF-kappaB activation but significantly increased activation of STAT6. In STAT6 knockout mice, neither IL-4 nor IL-13 had any effect on TNFalpha, MPO, or ALT values, the regulatory effects of these cytokines being completely abolished. The data suggest that activation of STAT6 may regulate liver inflammatory injury.

Requirement for NF-kappaB in transcriptional activation of monocyte chemotactic protein 1 by Chlamydia pneumoniae in human endothelial cells.

Infection with Chlamydia pneumoniae, a causative agent of acute and chronic respiratory diseases, has recently been implicated as a potential risk factor in atherosclerosis. Atherosclerotic lesions are characterized by monocyte infiltration, which may be regulated by the chemokine monocyte chemotactic protein 1 (MCP-1). We have previously shown that C. pneumoniae infection stimulates MCP-1 production in human endothelial cells, an event which may be specific to this species of Chlamydia, since Chlamydia trachomatis infection fails to induce this response. To examine the underlying mechanisms by which C. pneumoniae infection induces MCP-1 production in endothelial cells, the present study investigated the role of transcription factor NF-kappaB in MCP-1 mRNA expression. Human umbilical vein endothelial cells (HUVEC) were infected with the coronary isolate C. pneumoniae A-03 or with C. trachomatis L2, and MCP-1 mRNA expression was assessed after different periods of infection by reverse transcription-PCR. Expression of MCP-1 mRNA in C. pneumoniae-infected HUVEC was significantly elevated as early as 1 h postinfection and increased dramatically by 12 and 24 h compared to baseline controls. Nuclear translocation of NF-kappaB occurred by 30 min of infection, as determined by electrophoretic mobility shift assays and immunofluorescence staining. Treatment of C. pneumoniae-infected HUVEC with parthenolide, a specific inhibitor of NF-kappaB activation, suppressed MCP-1 mRNA expression. In contrast, infection with C. trachomatis L2 did not induce MCP-1 mRNA in infected HUVEC and failed to activate NF-kappaB. Results from this study demonstrate a requirement for NF-kappaB activation in stimulation of MCP-1 gene expression by C. pneumoniae in human endothelial cells. Furthermore, the data suggest that, within the genus Chlamydia, functionally distinct signaling pathways leading to NF-kappaB activation are utilized by C. pneumoniae in endothelial cells during infection.

The NFkappaBb/IkappaB system in acute inflammation.

The transcription factor NFkappaB is a primary regulator of a wide variety of proinflammatory mediators. Under normal conditions, NFkappaB is retained in the cytoplasm bound to inhibitory proteins of the IkappaB family. Following cell activation, a number of signal transduction pathways lead to degradation of IkappaB proteins which results in nuclear translocation of NFkappaB and the ensuing transcriptional activation of proinflammatory genes. Several endogenous regulatory mediators, which function to prevent uncontrolled inflammation, exert their effects by blocking the activation of NFkappaB. Thus, NFkappaB appears to be at the heart of the acute inflammatory response. The present review discusses the role of NFkappaB in the induction and propagation of the acute inflammatory response as well as the regulation and resolution of this process.

Anti-inflammatory effects of mutant forms of secretory leukocyte protease inhibitor.

The secretory leukocyte protease inhibitor (SLPI) is found in a variety of secreted fluids in mammals and is a known inhibitor of serine proteases. Wild-type (WT) SLPI has recently been shown to block nuclear factor kappaB (NF-kappaB) activation in rat lungs and to interfere with the ensuing inflammatory response and recruitment of neutrophils after an intrapulmonary deposition of IgG immune complexes. In this study, WT SLPI and SLPI mutants with various degrees of protease-inhibitory capacity (for trypsin, chymotrypsin, and elastase) were evaluated for their ability to suppress the lung-vascular leak, neutrophil accumulation, and NF-kappaB activation in the lung inflammatory model. The SLPI mutant with Gly(72) (replacing Leu(72) ) lost its ability to block in vivo activation of NF-kappaB, as well as its ability to suppress the lung vascular leak and neutrophil recruitment. The Phe(72) and Gly(20) mutants were as effective as the WT SLPI in suppressing NF-kappaB activation and neutrophil recruitment. The Lys(72) mutant had the most suppressive effects of the lung vascular leak and for neutrophil recruitment into the lung. The in vivo suppressive effects of SLPI mutants on lung vascular permeability, neutrophil recruitment, and NF-kappaB activation appear to be most closely related to their trypsin-inhibiting activity. These data suggest that the suppressive effects of SLPI on the intrapulmonary activation of NF-kappaB and neutrophil recruitment into the lung may be linked to their antiprotease activity, directed, perhaps, at the intracellular proteases.

Role of CC chemokines (macrophage inflammatory protein-1 beta, monocyte chemoattractant protein-1, RANTES) in acute lung injury in rats.

The role of the CC chemokines, macrophage inflammatory protein-1 beta (MIP-1 beta), monocyte chemotactic peptide-1 (MCP-1), and RANTES, in acute lung inflammatory injury induced by intrapulmonary deposition of IgG immune complexes injury in rats was determined. Rat MIP-1 beta, MCP-1, and RANTES were cloned, the proteins were expressed, and neutralizing Abs were developed. mRNA and protein expression for MIP-1 beta and MCP-1 were up-regulated during the inflammatory response, while mRNA and protein expression for RANTES were constitutive and unchanged during the inflammatory response. Treatment of rats with anti-MIP-1 beta Ab significantly decreased vascular permeability by 37% (p = 0.012), reduced neutrophil recruitment into lung by 65% (p = 0.047), and suppressed levels of TNF-alpha in bronchoalveolar lavage fluids by 61% (p = 0.008). Treatment of rats with anti-rat MCP-1 or anti-rat RANTES had no effect on the development of lung injury. In animals pretreated intratracheally with blocking Abs to MCP-1, RANTES, or MIP-1 beta, significant reductions in the bronchoalveolar lavage content of these chemokines occurred, suggesting that these Abs had reached their targets. Conversely, exogenously MIP-1 beta, but not RANTES or MCP-1, caused enhancement of the lung vascular leak. These data indicate that MIP-1 beta, but not MCP-1 or RANTES, plays an important role in intrapulmonary recruitment of neutrophils and development of lung injury in the model employed. The findings suggest that in chemokine-dependent inflammatory responses in lung CC chemokines do not necessarily demonstrate redundant function.

Regulation of inflammatory vascular damage.

The acute inflammatory response is comprised of an elaborate cascade of mediators that control an ordered sequence of events resulting in the recruitment of neutrophils to the site of infection or injury. Microvascular injury occurring during acute inflammation often results in increased vascular permeability and microvascular haemorrhage. Damage to vascular endothelial cells, basement membrane, and matrix components results from both neutrophil-dependent and neutrophil-independent mechanisms and is also dependent on the organ/tissue source of the endothelial cells. Neutrophil-mediated injury of endothelial cells involves a complex cascade in which products from both cell types affect the cytotoxic outcome. It is also clear that the acute inflammatory response is carefully regulated by the endogenous gene expression of both pro-inflammatory and anti-inflammatory mediators. Control of acute inflammation seems to relate to activation of the transcription factor NFkappaB. To appreciate the interrelationship between multiple contributing factors of inflammatory vascular injury, one must first have an understanding of the inflammatory mediator cascades which bring about the recruitment of neutrophils to the site of inflammation. In this review it is discussed how inflammatory mediators, as well as the products of activated neutrophils, affect the outcome of the acute inflammatory response.

Requirement for interleukin-12 in the pathogenesis of warm hepatic ischemia/reperfusion injury in mice.

Hepatic ischemia and reperfusion causes neutrophil-dependent liver injury. Although the mechanisms of ischemia/reperfusion-induced liver neutrophil recruitment are somewhat understood, less is known regarding the early events that initiate the inflammatory injury. Using a murine model of partial hepatic ischemia and reperfusion, we evaluated the role of endogenous interleukin (IL)-12 in this inflammatory response. Hepatic ischemia for 90 minutes and reperfusion for up to 4 hours resulted in hepatocyte expression of IL-12. By 8 hours of reperfusion there were large increases in serum levels of interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha). In addition, hepatic ischemia/reperfusion caused significant increases in liver neutrophil recruitment, hepatocellular injury, and liver edema, as defined by liver myeloperoxidase content, serum alanine aminotransferase, and liver wet to dry weight ratios, respectively. In mice treated with neutralizing antibody to IL-12 and in mice deficient in the IL-12 p40 gene, ischemia/reperfusion-induced increases in IFNgamma and TNFalpha were greatly diminished. These conditions also caused significant reductions in liver myeloperoxidase content and attenuated the parameters of liver injury. The data suggest that IL-12 is required for the full induction of injury after hepatic ischemia and reperfusion.