PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Interleukin-18 Receptor alpha Subunit”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1998

Selective expression and functions of interleukin 18 receptor on T helper (Th) type 1 but not Th2 cells.

Interleukin (IL)-18 induces interferon (IFN)-gamma synthesis and synergizes with IL-12 in T helper type 1 (Th1) but not Th2 cell development. We report here that IL-18 receptor (IL-18R) is selectively expressed on murine Th1 but not Th2 cells. IL-18R mRNA was expressed constitutively and consistently in long-term cultured clones, as well as on newly polarized Th1 but not Th2 cells. IL-18 sustained the expression of IL-12Rbeta2 mRNA, indicating that IL-18R transmits signals that maintain Th1 development through the IL-12R complex. In turn, IL-12 upregulated IL-18R mRNA. Antibody against an IL-18R-derived peptide bound Th1 but not Th2 clones. It also labeled polarized Th1 but not Th2 cells derived from naive ovalbumin-T cell antigen receptor-alphabeta transgenic mice (D011.10). Anti-IL-18R antibody inhibited IL-18- induced IFN-gamma production by Th1 clones in vitro. In vivo, anti-IL-18R antibody reduced local inflammation and lipopolysaccharide-induced mortality in mice. This was accompanied by shifting the balance from Th1 to Th2 responses, manifest as decreased IFN-gamma and proinflammatory cytokine production and increased IL-4 and IL-5 synthesis. Therefore, these data provide a direct mechanism for the selective effect of IL-18 on Th1 but not Th2 cells. They also show that the synergistic effect of IL-12 and IL-18 on Th1 development may be due to the reciprocal upregulation of their receptors. Furthermore, IL-18R is a cell surface marker distinguishing Th1 from Th2 cells and may be a therapeutic target.

Animals↗
PubMed1999

Defective interleukin (IL)-18-mediated natural killer and T helper cell type 1 responses in IL-1 receptor-associated kinase (IRAK)-deficient mice.

Interleukin (IL)-18 is functionally similar to IL-12 in mediating T helper cell type 1 (Th1) response and natural killer (NK) cell activity but is related to IL-1 in protein structure and signaling, including recruitment of IL-1 receptor-associated kinase (IRAK) to the receptor and activation of c-Jun NH2-terminal kinase (JNK) and nuclear factor (NF)-kappaB. The role of IRAK in IL-18-induced responses was studied in IRAK-deficient mice. Significant defects in JNK induction and partial impairment in NF-kappaB activation were found in IRAK-deficient Th1 cells, resulting in a dramatic decrease in interferon (IFN)-gamma mRNA expression. In vivo Th1 response to Propionibacterium acnes and lipopolysaccharide in IFN-gamma production and induction of NK cytotoxicity by IL-18 were severely impaired in IRAK-deficient mice. IFN-gamma production by activated NK cells in an acute murine cytomegalovirus infection was significantly reduced despite normal induction of NK cytotoxicity. These results demonstrate that IRAK plays an important role in IL-18-induced signaling and function.

Animals↗
PubMed1999

Impairment of natural killer cytotoxic activity and interferon gamma production in CCAAT/enhancer binding protein gamma-deficient mice.

We have investigated in vivo roles of CCAAT/enhancer binding protein gamma (C/EBPgamma) by gene targeting. C/EBPgamma-deficient (C/EBPgamma(2/-)) mice showed a high mortality rate within 48 h after birth. To analyze the roles of C/EBPgamma in lymphoid lineage cells, bone marrow chimeras were established. C/EBPgamma(2/-) chimeras showed normal T and B cell development. However, cytolytic functions of their splenic natural killer (NK) cells after stimulation with cytokines such as interleukin (IL)-12, IL-18, and IL-2 were significantly reduced as compared with those of control chimera NK cells. In addition, the ability of C/EBPgamma(-/-) chimera splenocytes to produce interferon (IFN)-gamma in response to IL-12 and/or IL-18 was markedly impaired. NK cells could be generated in vitro with normal surface marker expression in the presence of IL-15 from C/EBPgamma(2/-) newborn spleen cells. However, they also showed lower cytotoxic activity and IFN-gamma production when stimulated with IL-12 plus IL-18 than control NK cells, as observed in C/EBPgamma(2/-) chimera splenocytes. In conclusion, our study reveals that C/EBPgamma is a critical transcription factor involved in the functional maturation of NK cells.

Animals↗
PubMed1998

Cloning and expression of a single-chain Fv fragment specific for the human interleukin 18 receptor.

We have recently reported the successful purification and characterization of the human interleukin 18 (IL-18) receptor (R) using a monoclonal antibody (MAb) of the IgM kappa class (117-10C) after immunizing mice with cells of the Hodgkin's disease-derived cell line L428. This antibody is specific for the human IL-18R and inhibits the bioactivity of IL-18. Here we report on the polymerase chain reaction (PCR)-assisted cloning and sequencing of cDNAs encoding the variable regions of the light and heavy chains of 117-10C. We expressed the antibody in the form of a single-chain Fv fragment (scFv) in Chinese Hamster Ovary (CHO) cells and purified it from culture supernatants by chromatography. The purified scFv has an affinity for IL-18R of 5.6 x 10(8) M(-1), whereas 117-10C binds to the receptor with an affinity constant of 3.6 x 10(9) M(-1). Since 117-10C is of the IgM class, it is expected to be in the pentamer form and should theoretically therefore bind IL-18R with 10 times the affinity of the single-chain fragment may explain the difference in the affinity constants for the two molecules. The inhibitory efficiency of 117-10C was found to be 6-fold that of scFv in an interferon gamma (IFN-gamma)-inducing assay on the IL-18-responsive cell line KG-1. In conclusion, we have produced a single-chain fragment of a murine anti-human IL-18R antibody that is as potent at binding IL-18 as the parent antibody, and may be useful in neutralizing the cytokine in human conditions associated with high production of IL-18.

Amino Acid Sequence↗
PubMed2000

IL-12 synergizes with IL-18 or IL-1beta for IFN-gamma production from human T cells.

IL-18 is a proinflammatory cytokine that plays an important role in NK cell activation and T(h)1 response. IL-18 has a structural homology to IL-1, particularly IL-1beta. IL-18R, composed of IL-1R-related protein (IL-18Ralpha) and IL-1R accessory protein-like (IL-18Rbeta), belongs to the IL-1R family. Furthermore, IL-18R at least partly shares the signal transducing system with IL-1R. Thus, the IL-18-IL-18R system has a striking similarity to the IL-1-IL-1R system. For this reason, we regarded it important to investigate whether, like IL-18, IL-1beta synergizes with IL-12 in inducing IFN-gamma production from human T cells and plays an important role in the T(h)1 response. Here we show that IL-12 and IL-1beta synergistically induce T cells to proliferate and produce IFN-gamma without their TCR engagement. IL-12 stimulation induced an increase in the proportion of T cells positive for IL-18R. Then, IL-12-stimulated T cells responded to IL-18 or IL-1beta by their proliferation and IFN-gamma production, although levels of IL-1beta-induced responses were lower. CD4(+)CD45RA(+) T cells, although they constitutively expressed IL-18Rbeta mRNA, did not express IL-18Ralpha mRNA. Phytohemagglutinin (PHA) stimulation alone induced IL-18Ralpha mRNA without affecting the expression of IL-18Rbeta mRNA. T(h)1-inducing conditions (PHA, IL-12 and anti-IL-4) further increased this expression. We also show that T(h)1 cells but not T(h)2 cells have increased expression of IL-18R and IL-1R, and produce IFN-gamma in response to IL-18 and/or IL-1beta.

Drug Synergism↗
PubMed1999

Neuroblastoma cells expressing mature IL-18, but not proIL-18, induce a strong and immediate antitumor immune response.

Retroviral constructs were designed to express the novel cytokine interleukin 18 (IL-18), also known as interferon-gamma-inducing factor, in a murine neuroblastoma cell line [neuro-2a (N-2a)] to examine the effects of IL-18 expression on tumorigenicity. N-2a cells expressing proIL-18 (N-2a/IL-18p) were as tumorigenic as parental N-2a cells, whereas N-2a cells engineered to secrete mature IL-18 (N-2a/IL-18m) were nontumorigenic. Inoculation of mice with N-2a/IL-18m generated immediate immunity to parental N-2a. N-2a/IL-18m formed tumors in mice depleted of CD4+ and CD8+ T cells, suggesting that the antitumor immune response was T cell mediated. The resulting T-helper (Th) immune response was also characterized in vitro and had a large Th1 component based on in vitro production of the cytokines IFN-gamma and granulocyte macrophage colony-stimulating factor in response to tumor cells and IL-18.

Animals↗
PubMed1999

A proinflammatory role for IL-18 in rheumatoid arthritis.

IL-18 is a novel cytokine with pleiotropic activities critical to the development of T-helper 1 (Th1) responses. We detected IL-18 mRNA and protein within rheumatoid arthritis (RA) synovial tissues in significantly higher levels than in osteoarthritis controls. Similarly, IL-18 receptor expression was detected on synovial lymphocytes and macrophages. Together with IL-12 or IL-15, IL-18 induced significant IFN-gamma production by synovial tissues in vitro. IL-18 independently promoted GM-CSF and nitric oxide production, and it induced significant TNF-alpha synthesis by CD14(+) macrophages in synovial cultures; the latter effect was potentiated by IL-12 or IL-15. TNF-alpha and IFN-gamma synthesis was suppressed by IL-10 and TGF-beta. IL-18 production in primary synovial cultures and purified synovial fibroblasts was, in turn, upregulated by TNF-alpha and IL-1beta, suggesting that monokine expression can feed back to promote Th1 cell development in synovial membrane. Finally, IL-18 administration to collagen/incomplete Freund's adjuvant-immunized DBA/1 mice facilitated the development of an erosive, inflammatory arthritis, suggesting that IL-18 can be proinflammatory in vivo. Together, these data indicate that synergistic combinations of IL-18, IL-12, and IL-15 may be of importance in sustaining both Th1 responses and monokine production in RA.

Animals↗
PubMed2000

A poxvirus protein that binds to and inactivates IL-18, and inhibits NK cell response.

IL-18 induces IFN-gamma and NK cell cytotoxicity, making it a logical target for viral antagonism of host defense. We demonstrate that the ectromelia poxvirus p13 protein, bearing homology to the mammalian IL-18 binding protein, binds IL-18, and inhibits its activity in vitro. Binding of IL-18 to the viral p13 protein was compared with binding to the cellular IL-18R. The dissociation constant of p13 for murine IL-18 is 5 nM, compared with 0.2 nM for the cellular receptor heterodimer. Mice infected with a p13 deletion mutant of ectromelia virus had elevated cytotoxicity for YAC-1 tumor cell targets compared with control animals. Additionally, the p13 deletion mutant virus exhibited decreased levels of infectivity. Our data suggest that inactivation of IL-18, and subsequent impairment of NK cell cytotoxicity, may be one mechanism by which ectromelia evades the host immune response.

Amino Acid Sequence↗
PubMed1999

Differential cytokine and chemokine gene expression by human NK cells following activation with IL-18 or IL-15 in combination with IL-12: implications for the innate immune response.

NK cells constitutively express monocyte-derived cytokine (monokine) receptors and secrete cytokines and chemokines following monokine stimulation, and are therefore a critical component of the innate immune response to infection. Here we compared the effects of three monokines (IL-18, IL-15, and IL-12) on human NK cell cytokine and chemokine production. IL-18, IL-15, or IL-12 alone did not stimulate significant cytokine or chemokine production in resting NK cells. The combination of IL-18 and IL-12 induced extremely high amounts of IFN-gamma protein (225 +/- 52 ng/ml) and a 1393 +/- 643-fold increase in IFN-gamma gene expression over those in resting NK cells. IL-15 and IL-12 induced less IFN-gamma protein (24 +/- 10 ng/ml; p < 0.007) and only a 45 +/- 19-fold increase in IFN-gamma gene expression over those in resting NK cells. The CD56bright NK cell subset produced significantly more IFN-gamma following IL-18 and IL-12 compared with CD56dim NK cells (p < 0.008). However, the combination of IL-15 and IL-12 was significantly more potent than that of IL-18 and IL-12 for NK cell production of IL-10, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, and TNF-alpha at the protein and transcript levels. Granulocyte-macrophage CSF was optimally induced by IL-15 and IL-18. Resting CD56+ NK cells expressed IL-18R transcript that was up-regulated by IL-12 or IL-15. Our results show that distinct cytokine and chemokine patterns are induced in NK cells in response to different costimulatory signals from these three monokines. This suggests that NK cell cytokine production may be governed in part by the monokine milieu induced during the early proinflammatory response to infection and by the subset of NK cells present at the site of inflammation.

CD56 Antigen↗
PubMed1999

Cutting edge: generation of IL-18 receptor-deficient mice: evidence for IL-1 receptor-related protein as an essential IL-18 binding receptor.

IL-18 is a proinflammatory cytokine that plays an important role in NK cell activation and Th1 cell response. Recently IL-1R-related protein (IL-1Rrp) has been cloned as the receptor for IL-18. However, the functional role of IL-1Rrp is still controversial due to its low affinity to IL-18 as well as the possibility of the presence of another high-affinity binding receptor. In the present study, we have generated and characterized IL-1Rrp-deficient mice. The binding of murine rIL-18 was not detected in Th1-developing splenic CD4+ T cells isolated from IL-1Rrp-deficient mice. The activation of NF-kappa B or c-Jun N-terminal kinase were also not observed in the Th1 cells. NK cells from IL-1Rrp-deficient mice had defects in cytolytic activity and IFN-gamma production in response to IL-18. Th1 cell development was also impaired in IL-1Rrp-deficient mice. These data demonstrate that IL-1Rrp is a ligand-binding receptor that is essential for IL-18-mediated signaling events.

Animals↗
PubMed2000

Interleukin-18: biological properties and clinical implications.

IL-18, originally identified as interferon-gamma inducing factor (IGIF), is related to the IL-1 family in terms of its structure, processing, receptor, signal transduction pathway and pro-inflammatory properties. IL-18 is also functionally related to IL-12, as it induces the production of Th1 cytokines and participates in cell-mediated immune cytotoxicity. This review summarizes the recent advances in the understanding of IL-18 structure, processing, receptor expression and immunoregulatory functions, and focuses on the role of IL-18 modulation in tumours, infections, and autoimmune and inflammatory diseases.

Animals↗
PubMed2000

Interleukin-18 mRNA, but not interleukin-18 receptor mRNA, is constitutively expressed in islet beta-cells and up-regulated by interferon-gamma.

Interleukin-18 (IL-18) mRNA is expressed in islets of NOD mice during the early stages of insulitis and IL-18 has therefore been implicated as a contributing factor in immune-mediated beta-cell destruction. However, a recent study failed to show any effect of human IL-18 on the function of isolated rat islets. Since species differences have been shown between human and murine IL-18, the aims of this study were to investigate 1) if species homologous IL-18 alone or following IL-12 pre-exposure affected rat islet function, 2) if IL-18 dose-dependently modulated IL-1 beta or interferon-gamma (IFN-gamma) + tumor necrosis factor-alpha (TNF-alpha) actions on islet function, and 3) if IL-18 and IL-18 receptor (IL-18R) were expressed in rat islet beta-cells. Insulin release and nitric oxide (NO) production from isolated rat islets were measured after incubation with or without cytokines. RT-PCR was used to quantitate mRNA expression of IL-18 and the IL-18R signaling chain (IL-18R beta). There were no significant effects of 0.625-10 nM recombinant murine (rm) IL-18 alone on accumulated or glucose-challenged insulin release or NO production after 24 hours. Fifteen pg/ml of recombinant human (rh) IL-1 beta as well as 200 U/ml recombinant rat (rr) IFN-gamma + 250 U/ml rhTNF-alpha significantly increased islet NO production and inhibited both accumulated and glucose-challenged islet insulin release. However, rmIL-18 failed to modulate these effects of IL-1 beta or IFN-gamma + TNF-alpha. Although IL-12 induces IL-18R expression in Th1 and B lymphocytes, 24-hours rmIL-12 preincubation neither sensitized islets to effects of 10 nM of rm or rrIL-18 alone nor primed the islets to IL-1 beta actions on insulin release and NO production. IL-18R beta mRNA, which was expressed in human peripheral blood mononuclear cells (PBMC), was not expressed in rat insulinoma (RIN) cells or in isolated rat islets, even after exposure to IL-1 beta and/or IFN-gamma + TNF-alpha or IL-12. IL-18 mRNA was constitutively expressed in RIN cells, in FACS-purified rat beta-cells and in intact rat and mouse islets, and was up-regulated by IFN-gamma in an interferon regulatory factor-1- IRF-1) and NO - independent manner. However, IL-18 protein was undetectable in lysates and supernates of RIN cells by ECL, Western blotting and immunoprecipitation. In conclusion, we show for the first time that IL-18 but not IL-18R is expressed in rodent islet beta-cells. The physiological importance and pathological role of IL-18 originating from islet beta-cells deserve further investigation.

Animals↗
PubMed1998

Differential capacities of CD4+, CD8+, and CD4-CD8- T cell subsets to express IL-18 receptor and produce IFN-gamma in response to IL-18.

IL-12 and IL-18 have the capacity to stimulate IFN-gamma production by T cells. Using a T cell clone, we reported that IL-18 responsiveness is generated only after exposure to IL-12. Here, we investigated the induction of IL-18 responsiveness in resting CD8+, CD4+, and CD4-CD8- T cells. Resting T cells respond to neither IL-12 nor IL-18. After stimulation with anti-CD3 plus anti-CD28 mAbs, CD8+, CD4+, and CD4-CD8- T cells expressed IL-12R, but not IL-18R, and produced IFN-gamma in response to IL-12. Cultures of T cells with anti-CD3/anti-CD28 in the presence of rIL-12 induced IL-18R expression and IL-18-stimulated IFN-gamma production, which reached higher levels than that induced by IL-12 stimulation. However, there was a substantial difference in the expression of IL-18R and IL-18-stimulated IFN-gamma production among T cell subsets. CD4+ cells expressed marginal levels of IL-18R and produced small amounts of IFN-gamma, whereas CD8+ cells expressed higher levels of IL-18R and produced more IFN-gamma than CD4+ cells. Moreover, CD4-CD8- cells expressed levels of IL-18R comparable to those for CD8+ cells but produced IFN-gamma one order higher than did CD8+ cells. These results indicate that the induction of IL-18R and IL-18 responsiveness by IL-12 represents a mechanism underlying enhanced IFN-gamma production by resting T cells, but the operation of this mechanism differs depending on the T cell subset stimulated.

Animals↗
PubMed1998

[IL-18 and IL-18 receptor].

Interleukin-18 (IL-18) is a recently cloned cytokine, produced from activated macrophages, including Kupffer cells. IL-18 is originally called interferon-gamma inducing factor (IGIF), due to its action to induce IFN-gamma production from Th 1 cells and NK cells. However, recent studies suggested that, IL-18 also enhances expression of FasL and NK activity as well as GM-CSF production. These data revealed this novel cytokine is pleiotropic. Recently, cDNA encoding human IL-18 receptor (IL-18R) was cloned. And, we had cloned murine IL-18R cDNA by RT-PCR, using human IL-18R sequence. Northern blot analysis of cytoplasmic RNA from T cells stimulated with IL-12 clearly demonstrated that, T cells stimulated with IL-12 induced high level of IL-18R-mRNA, whereas non-stimulated T cells did not have. Interestingly, we had several reports, indicated the involvement of IL-18 on the progressions of pathogenicity in chronic inflammatory diseases, including endotoxin-shock, hepatitis and autoimmune-diabetes. We need further studies to reveal physiological roles of this novel cytokine in various inflammatory or autoimmune diseases.

Animals↗
PubMed1998

IL-12 up-regulates IL-18 receptor expression on T cells, Th1 cells, and B cells: synergism with IL-18 for IFN-gamma production.

IL-18 is a product of macrophages and with IL-12 strikingly induces IFN-gamma production from T, B, and NK cells. Furthermore, IL-18 and 1L-12 synergize for IFN-gamma production from Th1 cells, although this combination fails to affect Th2 cells. In this study, we show that IL-12 and IL-18 promptly and synergistically induce T and B cells to develop into IFN-gamma-producing cells without engaging their Ag receptors. We also studied the mechanism underlying differences in IL-18 responsiveness between Th1 and Th2 cells. Pretreatment of T or B cells with IL-12 rendered them responsive to IL-18, which induces cell proliferation and IFN-gamma production. These IL-12-stimulated cells had both high and low affinity IL-18R and an increased IL-18R mRNA expression. In particular, IL-12-stimulated T cells strongly and continuously expressed IL-18R mRNA. However, when T cells developed into Th1 cells after stimulation with anti-CD3 and IL-12, they lowered this IL-12-induced-IL-18R mRNA expression. Then, such T cells showed a dominant response to anti-CD3 by IFN-gamma production when they were subsequently stimulated with anti-CD3 and IL-18. In contrast, Th2 cells did not express IL-18R mRNA and failed to produce IFN-gamma in response to anti-CD3 and IL-18, although they produced a substantial amount of IFN-gamma in response to anti-CD3 and IL-12. However, when Th1 and Th2 cells were stimulated with anti-CD3, IL-12, and IL-18, only the Th1 cells markedly augmented IFN-gamma production in response to IL-18, suggesting that IL-18 responsiveness between Th1 and Th2 cells resulted from their differential expression of IL-18R.

Animals↗
PubMed1999

IL-18 up-regulates perforin-mediated NK activity without increasing perforin messenger RNA expression by binding to constitutively expressed IL-18 receptor.

IL-18 is a powerful inducer of IFN-gamma production, particularly in collaboration with IL-12. IL-18, like IL-12, also augments NK activity. Here we investigated the molecular mechanism underlying the up-regulation of killing activity of NK cells by IL-18. IL-18, like IL-12, dose dependently enhanced NK activity of splenocytes. This action was further enhanced by costimulation with IL-12. Treatment with anti-IL-2R Ab did not affect IL-18- and/or IL-12-augmented NK activity, and splenocytes from IFN-gamma-deficient mice showed enhanced NK activity following stimulation with IL-12 and/or IL-18. Splenocytes from the mice deficient in both IL-12 and IL-18 normally responded to IL-18 and/or IL-12 with facilitated NK activity, suggesting that functional NK cells develop in the absence of IL-12 and IL-18. IL-18R, as well as IL-12R mRNA, was constitutively expressed in splenocytes from SCID mice, which lack T cells and B cells but have intact NK cells, and in those from IL-12 and IL-18 double knockout mice. NK cells isolated from SCID splenocytes expressed IL-18R on their surface. IL-18, in contrast to IL-12, did not enhance mRNA expression of perforin, a key molecule for exocytosis-mediated cytotoxicity. However, pretreatment with concanamycin A completely inhibited this IL-18- and/or IL-12-augmented NK activity. Furthermore, IL-18, like IL-12, failed to enhance NK activity of splenocytes from perforin-deficient mice. These data suggested that NK cells develop and express IL-12R and IL-18R in the absence of IL-12 or IL-18, and that both IL-18 and IL-12 directly and independently augment perforin-mediated cytotoxic activity of NK cells.

Animals↗
PubMed1999

Modulation of the gene network connected to interferon-gamma in liver regeneration from oval cells.

Suppression subtractive hybridization was used to clone genes associated with proliferation of oval cells in rat liver regenerating after a 70% partial hepatectomy combined with the feeding of 2-acetylaminofluorene. A subset of the identified genes comprised interferon-gamma receptor alpha subunit (IFN-gammaRalpha), gp91phox, interleukin-1beta (IL-1beta), lymphocyte function-associated molecule-1alpha (LFA-1), eukaryotic initiation factor-2-associated 67-kd protein (eIF-2-associated 67-kd protein), and alpha-fetoprotein, which constitute part of the cellular program modulated by IFN-gamma. Therefore, expression analysis performed by Northern blotting and immunohistochemistry were extended to include IFN-gamma, the IFN-gamma receptor beta subunit (IFN-gammaRbeta), three secondary response genes induced by interaction of IFN-gamma with IFN-gamma receptor complexes, ie, IL-1beta-converting enzyme (ICE), intercellular adhesion molecule-1 (ICAM-1), and urokinase-type plasminogen activator receptor (uPAR), and a cytokine inducing IFN-gamma expression, ie, interleukin-18 (IL-18). The Northern blot analysis showed that all examined genes were modulated when progenitor-like oval cells were activated and recruited for liver regeneration. Immunohistochemistry localized the subunits of the IFN-gamma receptor complex, IFN-gammaRalpha and IFN-gammaRbeta, the secondary response genes uPAR and ICAM-1, the IFN-gamma-inducing factor IL-18, and ICE to the ductular structures of oval cells. In contrast, during liver regeneration after a 70% partial hepatectomy, only modulation of IL-1beta and ICE was observed. Our results, therefore, indicate that IFN-gamma-mediated events may be particularly important when cells in the bile ductules must respond to liver damage by production of ductular oval cells.

2-Acetylaminofluorene↗