Immunological heterogeneity of multiple sclerosis in Sardinia and Sweden

Subjects from Sardinia, Italy, are relatively homogeneous compared to Swedes. Although ethnically distant, both populations have similarly high multiple sclerosis (MS) incidence rates. Pro- and anti-inflammatory cytokines and their receptors, signalling molecules and other immune response-associated factors might influence MS pathogenesis, though definite proof is missing. The study of populations with similar MS incidence but different genetic and environmental background could make possible the definition of factors that relate to such background differences. We selected untreated female MS patients from Sassari, Sardinia, and Stockholm, Sweden, and corresponding sexand age-matched healthy controls (HC), to study blood mononuclear cells (MNC) for mRNA expression of 20 immune response-related genes considered relevant in MS, employing real-time PCR. Higher expression of IL-12p40 mRNA was confined to MS from both Sassari and Stockholm, compared to corresponding HC. MS patients from Sassari, but not Stockholm, expressed higher TNF-a compared to corresponding HC. MS patients from Stockholm, but not Sassari, expressed higher IL-6. Indoleamine 2,3 dioxygenase (IDO), a molecule necessary in tolerance induction, was lower in MS from Stockholm compared to corresponding HC. This was not observed in Sassari. No differences were detected for other members of the IL-12 family, other Th1 and Th2 cytokines, and the signalling molecules Stat 4 and 6. The results corroborate a pro-inflammatory state in MS as reflected by high expression of IL-12, TNF-a and IL-6, although the extent of expression of TNF-a, IL-6 and IDO differs between strictly matched MS patients from different high-incidence areas. This might result from genetic and/or environmental differences. They may account for some of the discrepancies regarding immune response-related molecules previously reported in MS. In conclusion, a pro-inflammatory state exists in MS patients from Sassari as well as Stockholm. The changes of pro-inflammatory and other immune response-related variables differ however between the two MS populations. This may be attributed to the genetic and/or environmental background.

Interleukin 18 and periodontal disease

Cytokines are of major importance in periodontal disease progression. It is generally agreed that control of the Th1/Th2 balance is central to the immunoregulation of periodontal disease. There is increasing evidence in humans that the stable periodontal lesion is mediated by Th1 cells, while the progressive lesion sees a shift toward Th2 cells. Equally, there is conflicting evidence, mainly in animal models, that bone loss is mediated by Th1 responses, and that Th2 responses are protective. In the presence of IL-12, IL-18 induces Th1 responses while, in the absence of IL-12, it promotes Th2 responses. It is clear, therefore, that since IL-18 has the ability to induce either Th1 or Th2 differentiation, it becomes important to consider its role in periodontal disease. This review endeavors to give an overview of this cytokine and its relevance for periodontal disease.

A potential role for interleukin-18 in inhibition of the development of Cryptosporidium parvum

Accumulating evidence suggests that intestinal epithelial cells (IECs) constitutively express the immunoregulatory cytokine interleukin (IL)-18. IECs also serve as the host cell for the intracellular parasitic protozoan Cryptosporidium parvum. In the present study, C. parvum infection of a human enterocyte cell-line HCT-8 resulted in increased expression of IL-18 mRNA as measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR). IL-18 protein was detected in control uninfected cells and following infection there was increased expression as measured by enzyme-linked immunosorbent assay (ELISA). Gene expression revealed the presence of the IL-18 receptor subunits not only in cell-lines but also in freshly isolated IECs, suggesting that IL-18-mediated signalling events may contribute to epithelial host defence during infection. Recombinant IL-18 inhibited intracellular development of the parasite in HCT-8 and HT-29 cells. Increased expression of bactericidal antibiotic peptides LL-37 and alpha-defensin 2 by IL-18 in HCT-8 and HT-29 cells may represent one mode of action by which this pluripotent cytokine aids in limiting the development of intracellular pathogens such as C. parvum in the gastrointestinal tract.

Interleukin-18 system messenger RNA and protein expression in human endometrium during the menstrual cycle

OBJECTIVE

To investigate the IL-18 system, including IL-18, IL-18 receptor (IL-18R), IL-18 binding protein (IL-18BP), and IL-18 precursor (proIL-18), mRNA and protein expression in human endometrium during the menstrual cycle.

DESIGN

Controlled study.

SETTING

Clinical and academic research setting in a university medical center.

PATIENT(S)

Human endometrium was obtained from surgical specimens of normal cycling women undergoing hysterectomy for benign reasons.

INTERVENTION(S)

A total of 24 human endometrium samples were obtained at proliferative and secretory phase from surgical specimens of normal cycling women undergoing hysterectomy. Quantitative competitive polymerase chain reaction (QC PCR) and immunohistochemistry were performed.

MAIN OUTCOME MEASURE(S)

The differences of IL-18 system mRNA and the ratio of antagonist to agonist in both proliferative and secretory phases of endometrium were analyzed.

RESULT(S)

Our results showed a complete IL-18 system, including mRNA expression and protein production in both proliferative and secretory phases of the endometrium. The QC PCR demonstrated that both IL-18 and IL-18R decreased and IL-18BP increased mRNA expression in human endometrium in secretory phase compared with proliferative phase. A positive correlation of IL-18 and IL-18R in human endometrium was demonstrated in proliferative phase but not in secretory phase. In addition, there is a significantly higher ratio of IL-18BP to IL-18 mRNA levels in secretory endometrium compared with proliferative phase endometrium (P<.05).

CONCLUSION(S)

The expression and ratio of IL-18 antagonist to agonist may be responsible for embryo implantation.

Role of interleukin-18 in modulation of oral carcinoma cell proliferation

Interleukin-18 (IL-18), a proinflammatory cytokine, is produced by oral epithelia and carcinoma cells and implicated in tumor regression. Since its direct biological effect on oral cancer cells is not well defined, in this study, we employed a KB cell line to test IL-18 activity. Recombinant human IL-18 significantly inhibited KB cell proliferation in a dose-dependent fashion (P < .05) without increasing cytotoxicity. Analysis of its mode of action showed that IL-18 induced cell cycle arrest in the S phase; however, it did not trigger apoptotic cell death. Findings in this study indicate that the suppression of KB cell proliferation was attributed to the modulation of cell cycle progression, providing a new role of this cytokine in antitumor mechanisms.

IL-18 bridges innate and adaptive immunity through IFN-gamma and the CD134 pathway

IL-18 induces inflammation resulting in either enhanced protection from pathogens or exacerbation of autoimmunity, and T cells are profoundly activated during these responses. How IL-18 influences T cell activation is unknown, but this study in mice shows that IL-18 boosted Ag-specific T cell clonal expansion of effector T cells and induced a subpopulation of IFN-gamma superproducing T cells. Commitment to IFN-gamma production through IL-18 was independent of NK cells and IL-12 but dependent on host-derived IFN-gamma. To determine how expansion of these effectors occurred, IL-18 was shown to induce OX40L on dendritic cells, whereas peptide stimulation induced CD134 (OX40) on specific T cells. CD134 blockade inhibited T cell effector expansion thereby reducing the number of IFN-gamma superproducers by 12-fold. Thus, independent of IL-12, IL-18 impacts T cell immunity throughout lymphoid and nonlymphoid tissue by bridging the innate and adaptive arms of the immune system through IFN-gamma and the CD134 costimulatory pathway.

Deficiency of interleukin-18 in mice leads to hyperphagia, obesity and insulin resistance

Here we report the presence of hyperphagia, obesity and insulin resistance in knockout mice deficient in IL-18 or IL-18 receptor, and in mice transgenic for expression of IL-18 binding protein. Obesity of Il18-/- mice resulted from accumulation of fat tissue based on increased food intake. Il18-/- mice also had hyperinsulinemia, consistent with insulin resistance and hyperglycemia. Insulin resistance was secondary to obesity induced by increased food intake and occurred at the liver level as well as at the muscle and fat-tissue level. The molecular mechanisms responsible for the hepatic insulin resistance in the Il18-/- mice involved an enhanced expression of genes associated with gluconeogenesis in the liver of Il18-/- mice, resulting from defective phosphorylation of STAT3. Recombinant IL-18 (rIL-18) administered intracerebrally inhibited food intake. In addition, rIL-18 reversed hyperglycemia in Il18-/- mice through activation of STAT3 phosphorylation. These findings indicate a new role of IL-18 in the homeostasis of energy intake and insulin sensitivity.

Tumor necrosis factor-alpha-induced protein 1 and immunity to hepatitis B virus

AIM

To compare the gene expression profile in a pair of HBV-infected twins.

METHODS

The gene expression profile was compared in a pair of HBV-infected twins.

RESULTS

The twins displayed different disease outcomes. One acquired natural immunity against HBV, whereas the other became a chronic HBV carrier. Eighty-eight and forty-six genes were found to be up- or down-regulated in their PBMCs, respectively. Tumor necrosis factor-alpha-induced protein 1 (TNF-alphaIP1) that expressed at a higher level in the HBV-immune twins was identified and four pairs of siblings with HBV immunity by RT-PCR. However, upon HBV core antigen stimulation, TNF-alphaIP1 was downregulated in PBMCs from subjects with immunity, whereas it was slightly upregulated in HBV carriers. Bioinformatics analysis revealed a K+ channel tetramerization domain in TNF-alphaIP1 that shares a significant homology with some human, mouse, and C elegan proteins.

CONCLUSION

TNF-alphaIP1 may play a role in the innate immunity against HBV.

Cellular localization of IL-18 and IL-18 receptor in pig anterior pituitary gland

Pro-inflammatory cytokine interleukin 18 (IL-18) has been proposed to have a role in modulating immuno-endocrine functions. Our previous study showed that IL-18 and IL-18 receptor (IL-18R) colocalized in somatotrophs of the bovine anterior pituitary gland, and the possibility that IL-18 acts on somatotrophs as an autocrine factor. In the present study, we investigated the localization of IL-18 and IL-18R in the pig anterior pituitary gland. RT-PCR analysis showed the expression of IL-18 and IL-18R mRNAin the pig anterior pituitary gland. Immunohistochemistry of IL-18 and specific hormones revealed the presence of IL-18 in somatotrophs, mammotrophs, thyrotrophs and gonadotrophs. IL-18R was localized in somatotrophs and thyrotrophs. Furthermore, the somatotrophs immunoreactive for IL-18 did not contain IL-18R. Thus, IL-18R and IL-18 were not colocalized in an identical somatotroph. These findings suggest that the localization of IL-18 in pig somatotrophs is different from that in bovine somatotrophs, although IL-18 closely associates with somatotrophs in the anterior pituitary glands in both species.

Enhanced expression of interleukin-18 receptor alpha chain by CD4+ T cells in sarcoidosis

STUDY OBJECTIVES

To investigate the expression of interleukin-18 receptor alpha chain (IL-18Ralpha) in BAL and peripheral blood (PB) T cells in patients with sarcoidosis compared with control subjects, to evaluate the relationship between the expression and clinical manifestations, and to clarify the mechanisms of altered expression.

SUBJECTS AND METHODS

The study subjects consisted of 21 patients with sarcoidosis and 8 normal control subjects. The expression of IL-18Ralpha was examined by flow cytometry.

RESULTS

The proportions of BAL CD4+ and PB CD4+ T cells expressing IL-18Ralpha were significantly increased in patients with sarcoidosis compared to control subjects. BAL CD4+ T cells expressed IL-18Ralpha in a higher proportion than did paired CD8+ T cells in patients with sarcoidosis but not in control subjects. Greater proportions of BAL CD4+ T cells and BAL CD8+ T cells than of their PB counterparts expressed IL-18Ralpha in both patients and control subjects. CD4+ T cells were more sensitive to the induction of IL-18Ralpha by cytokines in vitro, such as interleukin (IL)-2, IL-12, and tumor necrosis factor-alpha than were CD8+ T cells. Increased expression of IL-18Ralpha by BAL T cells commonly observed in patients and control subjects was associated with the expansion of CD45RO+ cells in BAL T cells. However, there were no significant correlations between the expression of IL-18Ralpha by any cell populations and BAL findings, serum angiotensin-converting enzyme activities, radiograph stages, or clinical courses.

CONCLUSION

The overexpression of IL-18Ralpha predominantly by CD4+ T cells in sarcoidosis emphasizes crucial roles played by T-helper type 1 cells in the IL-18/IL-18Ralpha system in sarcoidosis.

Human Anti–Human IL-18 Antibody Recognizing the IL-18–Binding Site 3 with IL-18 Signaling Blocking Activity

IL-18 is an important regulator in both innate and acquired immune responses. The aberrant expression of IL-18 is associated with severe inflammatory conditions, such as autoimmune diseases and allergies. Thus, human antibodies with inhibitory activity on IL-18 signaling may be useful for therapeutic applications. We report here the first establishment of an antagonistic anti-IL-18 complete human antibody, h18-108, employing a human single chain antibody (scFv)-displaying phage library. The h18-108 scFv inhibited the IFN-gamma production of a human myelomonocytic cell line, KG-1. Flow cytometry analysis showed that h18-108 blocked the binding of IL-18 to KG-1 cells. Epitope mapping analysis using two kinds of random peptide-displaying phage libraries and an IL-18 alanine mutant (D98A) demonstrated that the h18-108 scFv binds to the site 3 of IL-18, which is suggested to be an association site with the IL-18 receptor beta. The complete human Fab and IgG forms of h18-108 have been successfully constructed to attain increases in both binding affinity and inhibitory activity.

Role of interleukin-18 and its receptor in hepatocellular carcinoma associated with hepatitis C virus infection

Interleukin (IL)-18 is a proinflammatory cytokine that is up-regulated in patients with hepatitis C virus (HCV) infection, which is the most common underlying disease in hepatocellular carcinoma (HCC). The purpose of our study was to investigate the role of IL-18 in HCC associated with HCV infection. Sixty-five patients with HCC and HCV infections who received curative surgical resections were examined in our study. The expression of the IL-18 receptor was investigated in HCC tissues obtained from these patients and in 2 HCC cell lines. Nuclear factor (NF)-kappaB activity and the expression of Bcl-xL and xIAP mRNA were tested in the cell lines using recombinant human (rh) IL-18. The IL-18 receptor was expressed in both the HCC tissues and the cell lines. NF-kappaB activation and the expression of Bcl-xL and xIAP mRNA were increased by rhIL-18. Moreover, rhIL-18 suppressed the apoptosis of HCC cells which was induced by etoposide in vitro. The overall survival rate (55.4%) was significantly worse in the IL-18 receptor-positive patients than in the IL-18 receptor-negative patients (p = 0.015). In a Cox multivariate analysis, the expression of the IL-18 receptor was found to be a significant predictor of a poor outcome in HCC patients. The expression of the IL-18 receptor and an antiapoptotic mechanism involving NF-kappaB activation in HCC cells may be implicated in a poor patient outcome.

Estrogen inhibits interleukin-18 mRNA expression in the mouse uterus

Interleukin-18 (IL-18) is a proinflammatory cytokine expressed in female reproductive organs in humans, rats and mice. The physiological roles of uterine IL-18 and the regulatory mechanisms of IL-18 gene expression are unclear. The present study aimed to clarify the effects of estradiol-17beta (E2) and progesterone (P4) on IL-18 mRNA expression in the mouse uterus. Distribution and expression levels of IL-18 mRNA were studied using an RNase protection assay. Expression of IL-18 mRNA was observed in all organs studied, including testes, ovaries and uteri. The uterine IL-18 mRNA level of estrous mice was higher than that of diestrous mice. E2 treatment (1, 5, 25 or 250 ng/mouse) decreased uterine IL-18 mRNA levels in ovariectomized mice dose-dependently. E2 treatment acutely decreased IL-18 mRNA levels 3 h after injection, but these levels returned to the initial level after 48 h. P4 treatment (1 mg/mouse) decreased uterine IL-18 mRNA levels after 12 h, but levels returned to the initial level after 48 h. Both uterine IL-18 and IL-18Ralpha mRNAs were detected in cultured endometrial epithelial and stromal cells. These results suggest that uterine IL-18 expression is reduced by sex steroid hormones and that IL-18 acts on endometrial cells in a paracrine or autocrine manner.

Localization of interleukin-18 and its receptor in somatotrophs of the bovine anterior pituitary gland

A pro-inflammatory cytokine, interleukin 18 (IL-18), induces intracellular expression of IL-1 and the release of IL-6. IL-1 and IL-6 has been detected in anterior pituitary cells, suggesting that IL-18 is produced in anterior pituitary cells and may serve to aid immuno-endocrine regulation. In the present study, we addressed this hypothesis by investigating the intracellular localization of IL-18 and its receptor in bovine anterior pituitary gland. IL-18 mRNA and its protein were detected in the anterior pituitary gland by RT-PCR and Western blotting. In situ hybridization showed that IL-18 mRNA was expressed in the anterior pituitary cells. Immunohistochemistry of IL-18 and specific hormones revealed the presence of IL-18 in somatotrophs. Furthermore, the expression of GH mRNA in IL-18 immunoreactive cells was confirmed by immuno-laser microdissection. These results first demonstrated that somatotrophs produced IL-18. Subsequently, the distribution of the IL-18 receptor alpha (IL-18Ralpha) was investigated in order to understand IL-18 signaling among the anterior pituitary cells. Bovine IL-18Ralpha cDNA was partially sequenced and detected in the anterior pituitary gland by RT-PCR. Immunohistochemistry of IL-18Ralpha, IL-18 and GH showed that IL-18Ralpha was co-localized in IL-18 immunoreactive cells or somatotrophs. These data suggest that IL-18 acts on somatotrophs as an immuno-endocrine mediator through the autocrine pathway.

Pathophysiological roles for IL-18 in inflammatory arthritis

IL-18 is a unique cytokine with prominently wide spectrum biological actions. Among these, its IFN-gamma/TNF-alpha-inducing activity primarily contributes to the development of various inflammatory diseases including inflammatory arthritis. IL-18 levels correlate with the disease activity of rheumatoid arthritis (RA) and osteoarthritis (OA). IL-18 is spontaneously released from RA synovial cells and OA chondrocytes and seems to participate in the development of the inflammatory and destructive alterations of joints via induction of TNF-alpha, a potent effector molecule. TNF-alpha, in turn, increases IL-18 expression in RA synovial cells. Recent clinical trials have revealed the efficacy of TNF-alpha in RA with a reduction in circulatory IL-18 levels. These may implicate the positive circuit between IL-18 and TNF-alpha for development of RA. As IL-18-deficient mice evade collagen-induced arthritis in a mouse RA model, therapeutics targeting IL-18 may be beneficial against RA/OA. Here, the authors review the possible roles of IL-18 in inflammatory arthritis.

Human Keratinocytes Respond to Interleukin-18: Implication for the Course of Chronic Inflammatory Skin Diseases

Interleukin (IL)-18 has been described to play a role in several inflammatory skin diseases such as eczema and psoriasis. In this study, we aimed to elucidate keratinocytes as potential targets for IL-18 effects. In human primary keratinocytes expression of IL-18Ralpha as well as responses to IL-18 were determined. In keratinocytes freshly isolated from skin biopsies of lesional atopic dermatitis or psoriasis, we observed a significantly higher expression of the IL-18Ralpha as compared with keratinocytes from normal donors. A marked upregulation was induced in vitro upon stimulation with interferon (IFN)gamma+tumor necrosis factor (TNF)alpha or poly I:C. IL-4 led to downregulation of IL-18Ralpha. IL-18-induced CXCL10/IP-10 production in freshly isolated keratinocytes from lesional psoriasis as well as in cultured normal keratinocytes. Furthermore, IL-18 upregulated major histocompatibility complex (MHC) class II expression on IFNgamma-stimulated keratinocytes. This was of functional significance as verified in coculture experiments with CD4+ T cells in the presence of superantigen. T cells produced significant amounts of IFNgamma after coculture with IL-18-induced MHC class II expressing keratinocytes. In conclusion, we have shown that keratinocytes functionally respond to IL-18 with upregulation of MHC II and production of the chemokine CXCL10/IP-10. These findings further support an important role of IL-18 in inflammatory skin diseases in the epidermal compartment.

Angiotensin II Enhances Interleukin-18 Mediated Inflammatory Gene Expression in Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) express functional interleukin-18 receptors (IL-18Rs), composed of α and β subunits. These subunits are elevated in VSMCs of atherosclerotic plaques and can be induced by inflammatory agents in cultured VSMC. Because both IL-18 and Angiotensin II (Ang II) are implicated in atherosclerosis, our objective was to analyze the role of IL-18 signaling and potential cross-talk with Ang II in VSMC. We observed that IL-18 activated Src kinase, protein kinase C, p38 and JNK MAPKs, Akt kinase, transcription factors NF-kB and AP-1, and induced expression of pro-inflammatory cytokines in VSMC. Pretreatment of VSMC with Ang II enhanced IL-18-induced NF-kB activation and cytokine gene expression. Interestingly, Ang II directly increased mRNA and cell surface protein levels of the IL-18Rα subunit. Functional relevance in an organ culture model was demonstrated by the observation that incubation of intact mouse aortas ex vivo with Ang II also significantly increased IL-18Rα expression. Furthermore, Ang II significantly stimulated transcription from a minimal IL-18Rα promoter containing putative binding sites for STAT and AP-1. Ang II also increased in vivo recruitment of STAT-3 on the IL-18Rα promoter. Finally, dominant negative STAT-3 mutant blocked Ang II-induced IL-18Rα promoter activation in CHO cells overexpressing AT1a receptor and IL-18Rα mRNA expression in HVSMC. Thus, Ang II enhances IL-18 induced inflammatory genes by increasing IL-18Rα expression. These results illustrate a novel mechanism wherein Ang II- mediated increases in inflammatory genes and proatherogenic effects in the vasculature are enhanced by a vicious loop and cross-talk with the IL-18 signaling pathway.

Differential expression of the cytokine receptors for human interleukin (IL)-12 and IL-18 on lymphocytes of both CD45RA and CD45RO phenotype from tonsils, cord and adult peripheral blood

The objective of this study was to demonstrate the variable expression of cytokine receptors on naive versus memory human CD4+ T cell subpopulations in tonsillar tissue, cord blood and adult blood. We prove that the receptors for both interleukin (IL)-12 and IL-18 are expressed exclusively on memory T cells. This observation was seen not only on the CD45RO+ memory T cells but also on a significant percentage of the CD45RA+, CD62L-, CD27- and CCR7- populations. Furthermore, CD45RA+ CD62L+, CD27+ or CCR7+ CD4+ T cells that expressed IL-12Rbeta1 and IL-18Ralpha did not express CD31, a marker for recent thymic emigrants. We reveal that cord blood lymphocytes do not express IL-12Rbeta1 whereas IL-18Ralpha expression was detected at low levels. Importantly, the IL-12Rbeta2 signalling chain, which is absent in all resting T cells, was up-regulated in both CD45RA+ and CD45RO+ T cells as a result of stimulation with anti-CD3 and anti-CD28 in vitro. This observed up-regulation was, however, restricted to 80% of the total CD4+ population. Finally, a very small proportion of the CD4+ CD45RO+ tonsillar T cells expressed the IL-12 and IL-18 receptors, thereby establishing the differential expression of these receptors between peripheral and tonsillar memory T cell subpopulations.

Prototype Alzheimer's disease vaccine using the immunodominant B cell epitope from beta-amyloid and promiscuous T cell epitope pan HLA DR-binding peptide

Immunization of amyloid precursor protein transgenic mice with fibrillar beta-amyloid (Abeta) prevents Alzheimer's disease (AD)-like neuropathology. The first immunotherapy clinical trial used fibrillar Abeta, containing the B and T cell self epitopes of Abeta, as the immunogen formulated with QS21 as the adjuvant in the vaccine. Unfortunately, the clinical trial was halted during the phase II stage when 6% of the participants developed meningoencephalitis. The cause of the meningoencephalitis in the patients that received the vaccine has not been definitively determined; however, analysis of two case reports from the AN-1792 vaccine trial suggest that the meningoencephalitis may have been caused by a T cell-mediated autoimmune response, whereas production of anti-Abeta Abs may have been therapeutic to the AD patients. Therefore, to reduce the risk of an adverse T cell-mediated immune response to Abeta immunotherapy we have designed a prototype epitope vaccine that contains the immunodominant B cell epitope of Abeta in tandem with the synthetic universal Th cell pan HLA DR epitope, pan HLA DR-binding peptide (PADRE). Importantly, the PADRE-Abeta(1-15) sequence lacks the T cell epitope of Abeta. Immunization of BALB/c mice with the PADRE-Abeta(1-15) epitope vaccine produced high titers of anti-Abeta Abs. Splenocytes from immunized mice showed robust T cell stimulation in response to peptides containing PADRE. However, splenocytes from immunized mice were not reactivated by the Abeta peptide. New preclinical trials in amyloid precursor protein transgenic mouse models may help to develop novel immunogen-adjuvant configurations with the potential to avoid the adverse events that occurred in the first clinical trial.

Functional role played by the glycosylphosphatidylinositol anchor glycan of CD48 in interleukin-18-induced interferon-gamma production

Interleukin (IL)-18 induces T cells and natural killer cells to produce not only interferon-gamma but also other cytokines by binding to the IL-18 receptor (IL-18R) alpha and beta subunits. However, little is known about how IL-18, IL-18Ralpha, and IL-18Rbeta form a high-affinity complex on the cell surface and transduce the signal. We found that IL-18 and IL-18Ralpha bind to glycosylphosphatidylinositol (GPI) glycan via the third mannose 6-phosphate diester and the second beta-GlcNAc-deleted mannose 6-phosphate of GPI glycan, respectively. To determine which GPI-anchored glycoprotein is involved in the complex of IL-18 and IL-18Ralpha, IL-18Ralpha of IL-18-stimulated KG-1 cells was immunoprecipitated together with CD48 by anti-IL-18Ralpha antibody. More than 90% of CD48 was detected as beta-GlcNAc-deleted GPI-anchored glycoprotein, and soluble recombinant human CD48 without GPI glycan bound to IL-18Ralpha, indicating that CD48 is associated with IL-18Ralpha via both the peptide portion and the GPI glycan. To investigate whether the carbohydrate recognition of IL-18 is involved in physiological activities, KG-1 cells were digested with phosphatidylinositol-specific phospholipase C before IL-18 stimulation. Phosphatidylinositol-specific phospholipase C treatment inhibited the phosphorylation of tyrosine kinases and the following IL-18-dependent interferon-gamma production. These observations suggest that the complex formation of IL-18.IL-18Ralpha. CD48 via both the peptide portion and GPI glycan triggers the binding to IL-18Rbeta, and the IL-18.IL-18Ralpha.CD48.IL-18Rbeta complex induces cellular signaling.

Therapeutic potential of targeting IL-1 and IL-18 in inflammation

Interleukin (IL)-1 and IL-18 are cytokines that play a major role in autoimmune and inflammatory human disease. Both cytokines drive a wide range of pro-inflammatory effector networks in many cell types and use common signal transduction cascades. IL-1, IL-18 and other members of the IL-1 superfamily are expressed at elevated levels in tissue and fluid samples isolated from patients with many chronic inflammatory diseases. These cytokines are primary drivers in acute and chronic animal models of inflammation and their blockade has been shown to ameliorate disease in preclinical studies. Biological agents that target IL-1 have demonstrated efficacy in patients with rheumatoid arthritis, and further agents targeting IL-1 or IL-18 neutralisation are in clinical development. The potential for such agents spans human disease where tissue destruction is a primary end point of cytokine action.

Epstein-Barr virus nuclear antigen 2 induces interleukin-18 receptor expression in B cells

Epstein-Barr virus (EBV) latently infects and immortalizes B lymphocytes and causes lymphoproliferative malignancies. We show here that the EBV nuclear antigen EBNA2 induces expression of the 2 chains of the interleukin-18 receptor (IL-18R) in Burkitt lymphoma (BL) cell lines and in nontransformed B cells. Activation of IL-18R expression by EBNA2 is independent of its interaction with the transcriptional repressor RBPJ kappa. It occurs in the absence of any other viral protein but requires de novo synthesis of cellular proteins. IL-18R induction is a highly specific function of EBNA2, because neither other EBV latent proteins nor the cellular proteins c-myc or Notch can exert this effect. Using cDNA microarray expression profiling, we find that the IL-18 receptor expressed in EBV-infected BL cells has signaling capacity, because IL-18 significantly modified gene expression. We report that EBNA2 expression is associated with IL-18R expression in vivo in EBV-positive B-lymphomas from AIDS patients.

IL-18 Receptor Expression on Epithelial Cells is Upregulated by TNF Alpha

IL-18 is a multifunctional cytokine that augments both innate and acquired immunity and potentiates Th1 and Th2 reactions. We studied the expression of IL-18 receptor (IL-18R) on renal and respiratory epithelial cell lines. Both cell lines upregulated IL-18R mRNA and IL-18R membrane expression in response to TNF alpha and other proinflammatory cytokines. The function of IL-18R was confirmed by induction of IL-8 release from epithelial cells in response to recombinant IL-18. Epithelial cells may represent an important target for IL-18, mainly under inflammatory conditions associated with TNF alpha release.

An early imbalance of interleukin 12 influences the adjuvant effect of mannoproteins of Cryptococcus neoformans

Mannoprotein from Cryptococcus neoformans induces protective response against a lethal challenge with this fungus or with Candida albicans. This phenomenon is largely related to early production of interleukin 12 (IL-12) and induction of T helper 1 response. Our study assesses whether the early absence of this critical cytokine could account for the incomplete activation of cellular response and whether the immune system compensates this imbalance. The results show that the neutralization of early IL-12 enhanced IL-18 production but decreased IFN-gamma secretion and IL-12R expression by splenic CD4 T cells. In contrast, IL-18R was not augmented despite an increase in IL-18 production. The co-stimulatory pathway was partially dysregulated because splenic macrophages showed unmodified B7-2, and a decrease of B7-1 expression. This dysregulation led to incomplete proliferative response of T cells in response to Cryptococcus neoformans and to increased fungal load in the brain 21 days post infection. The inability to dispose early IL-12, forced the immune system to compensate the imbalance and produced a series of long-lasting dysregulations involving the co-stimulatory pathway and T cell activation.

Activation of virus-specific CD8+ T cells by lipopolysaccharide-induced IL-12 and IL-18

Virus-specific T cells represent a hallmark of Ag-specific, adaptive immunity. However, some T cells also demonstrate innate functions, including non-Ag-specific IFN-gamma production in response to microbial products such as LPS or exposure to IL-12 and/or IL-18. In these studies we examined LPS-induced cytokine responses of CD8(+) T cells directly ex vivo. Following acute viral infection, 70-80% of virus-specific T cells will produce IFN-gamma after exposure to LPS-induced cytokines, and neutralization experiments indicate that this is mediated almost entirely through production of IL-12 and IL-18. Different combinations of these cytokines revealed that IL-12 decreases the threshold of T cell activation by IL-18, presenting a new perspective on IL-12/IL-18 synergy. Moreover, memory T cells demonstrate high IL-18R expression and respond effectively to the combination of IL-12 and IL-18, but cannot respond to IL-18 alone, even at high cytokine concentrations. This demonstrates that the synergy between IL-12 and IL-18 in triggering IFN-gamma production by memory T cells is not simply due to up-regulation of the surface receptor for IL-18, as shown previously with naive T cells. Together, these studies indicate how virus-specific T cells are able to bridge the gap between innate and adaptive immunity during unrelated microbial infections, while attempting to protect the host from cytokine-induced immunopathology and endotoxic shock.

MyD88-deficient mice develop severe intestinal inflammation in dextran sodium sulfate colitis

BACKGROUND

Gut commensal microbes affect the development and activation of the mucosal and systemic immune systems. However, the exact molecular mechanism of these microbes that is involved in the development of colitis remains unclear.

METHODS

The present study was conducted to determine the distinct role of the innate immune system in the development of a dextran sulfate sodium (DSS) colitis model in MyD88(-/-) mice, because myeloid differentiation protein (MyD88) is a major adaptor molecule essential for signaling via Toll-like receptors (TLRs). To this end, MyD88(-/-) and wild-type (WT) mice received sterile distilled water containing 1.2% DSS for 8 days. The survival rate, total clinical score (body weight loss, stool consistency, and rectal bleeding), colon length, and histological score were assessed. The expression of surface markers (F4/80 and CD4) on infiltrating lamina propria mononuclear cells was analyzed immunohistochemistrically.

RESULTS

MyD88(-/-) mice exhibited increased susceptibility to DSS-induced colitis, as reflected by significantly higher lethality and higher clinical and histological scores, and more severe colonic shortening compared to WT mice. Immunohistochemical analysis revealed a significant increase of both F4/80+ macrophages and CD4+ T cells in the inflamed mucosa in DSS-fed MyD88(-/-) mice compared to DSS-fed WT mice.

CONCLUSIONS

These findings suggest that, via MyD88 signaling, the innate immune system in the gut plays an important protective role in colitis.

Reduced expression of IL-12 receptor beta2 and IL-18 receptor alpha genes in natural killer cells and macrophages derived from B6-mi/mi mice

The mi transcriptional factor (MITF) is a basic helix-loop-helix leucine zipper-type transcriptional factor. The mi mutant allele encodes an abnormal MITF, in which one out of four consecutive arginines is deleted in the basic domain. The VGA-9-tg (tg) allele is another mutant allele and considered to be a null mutant allele. C57BL/6 (B6)-mi/mi mice showed abnormal phenotypes of natural killer (NK) cells and macrophages, whereas B6-tg/tg mice did not. The expression levels of the genes for the interleukin-12 receptor (IL-12R) beta2 and IL-18Ralpha were reduced in both the NK cells and macrophages of B6-mi/mi mice, while the expression levels of the corresponding genes in B6-tg/tg mice were unaffected. The B6-mi/mi NK cells and B6-mi/mi macrophages showed impaired responses to stimulation with IL-12, IL-18, and IL-12 plus IL-18 stimulation. The abnormal NK cell and macrophage of B6-mi/mi mice appear to be due to decreased expression of the IL-12Rbeta2 and IL-18Ralpha genes.

Enhanced Expression of Interleukin-18 and its Receptor in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP) is a major interstitial lung disease (ILD). Recently, we established a new mouse model for ILD in which daily administration of interleukin (IL)-18 with IL-2 induces lethal lung injury, suggesting that IL-18 is involved in the pathogenesis of ILD. Here, utilizing immunohistochemistry, we have analyzed IL-18 and IL-18 receptor (IL-18R) alpha expression in the lungs of 18 patients with IPF/UIP and 13 control subjects by using monoclonal anti-IL-18 antibodies and a new monoclonal antibody for IL-18Ralpha (H44). IL-18 was expressed in bronchoalveolar epithelium, alveolar macrophages, and the endothelium of small vessels in control subjects, and was abundantly expressed in the majority of pulmonary cells in patients with IPF. IL-18Ralpha was expressed in bronchoalveolar epithelium and alveolar macrophages in control subjects, and was strongly expressed in interstitial cells in patients with IPF, especially in the fibroblastic foci (FF). Interestingly, IL-18Ralpha expression was only weakly observed in areas showing established fibrosis. Semiquantitative analysis revealed that the histologic FF score was significantly correlated with the IL-18Ralpha expression level in FF lesions. Moreover, IL-18 levels in the serum and bronchoalveolar lavage fluid of patients with IPF were significantly higher than those in control subjects. Our findings suggest IL-18 and IL-18R are involved in the pathogenesis of IPF/UIP.

Interleukin-18 is a pro-hypertrophic cytokine that acts through a phosphatidylinositol 3-kinase-phosphoinositide-dependent kinase-1-Akt-GATA4 signaling pathway in cardiomyocytes

In patients with congestive heart failure, high serum levels of the proinflammatory cytokine interleukin (IL)-18 were reported. A positive correlation was described between serum IL-18 levels and the disease severity. IL-18 has also been shown to induce atrial natriuretic factor (ANF) gene expression in adult cardiomyocytes. Because re-expression of the fetal gene ANF is mostly associated with hypertrophy, a hallmark of heart failure, we hypothesized that IL-18 induces cardiomyocyte hypertrophy. Treatment of the cardiomyocyte cell line HL-1 with IL-18 induced hypertrophy as characterized by increases in protein synthesis, phosphorylated p70 S6 kinase, and ribosomal S6 protein levels as well as cell surface area. Furthermore, IL-18 induced ANF gene transcription in a time-dependent manner as evidenced by increased ANF secretion and ANF promoter-driven reporter gene activity. Investigation into possible signal transduction pathways mediating IL-18 effects revealed that IL-18 activates phosphoinositide 3-kinase (PI3K), an effect that was blocked by wortmannin and LY-294002. IL-18 induced Akt phosphorylation and stimulated its activity, effects that were abolished by Akt inhibitor or knockdown. IL-18 stimulated GATA4 DNA binding activity and increased transcription of a reporter gene driven by multimerized GATA4-binding DNA elements. Pharmacological inhibition or knockdown studies revealed that IL-18 induced cardiomyocyte hypertrophy and ANF gene transcription via PI3K, PDK1, Akt, and GATA4. Most importantly, IL-18 induced ANF gene transcription and hypertrophy of neonatal rat ventricular myocytes via PI3K-, Akt-, and GATA4-dependent signaling. Together these data provide the first evidence that IL-18 induces cardiomyocyte hypertrophy via PI3K-dependent signaling, defines a mechanism of IL-18-mediated ANF gene transcription, and further supports a role for IL-18 in inflammatory heart diseases including heart failure.

Involvement of Interleukin-18 in Acute Graft-Versus-Host Disease in Mice

BACKGROUND

Interleukin (IL)-18 stimulates T helper 1 (Th1)-mediated immune responses and the development of cytotoxic T lymphocytes (CTLs). Antihost CTLs are major effectors in acute graft-versus-host disease (aGvHD), a potentially fatal complication after allogeneic stem-cell transplantation. We investigated the relevant role of IL-18 in the development of aGvHD in mice.

METHODS

Irradiated (C57BL/6x DBA/2) F1 (BDF1) mice transplanted with wild-type (WT) C57BL/6 (B6) splenocytes were compared with those transplanted with IL-18Ralpha-deficient B6 splenocytes with respect to Th1 development, CTL activity, severity of aGvHD, and survival.

RESULTS

Transplantation of WT B6 spleen cells into BDF1 mice induced aGvHD that was accompanied by elevation of both serum IL-18 levels and IL-18 receptor alpha chain (IL-18Ralpha) expression on engrafted T cells. The transplantation of WT B6 cells also induced high antihost CTL activity in host spleen, whereas transplantation of IL-18Ralpha-deficient B6 cells exhibited significantly reduced antihost-specific CTL activity, indicating that IL-18Ralpha-deficient CTLs were less cytotoxic than IL-18Ralpha-expressing CTLs. Moreover, the hosts receiving transplants with the IL-18Ralpha-deficient B6 cells had fewer fatal tissue injuries and increased their survival rates as compared with those receiving transplants with WT cells. Nevertheless, Th1 development in the hosts was the same, regardless of the type of donor cells.

CONCLUSIONS

These results suggest that Th1 induction and baseline CTL activity in aGvHD occur in the absence of IL-18, but endogenous IL-18 further accelerates aGvHD reaction to its full-blown manifestation. Thus, IL-18 may be involved in the development aGvHD by enhancing CTL activity.

IL-1 receptor-associated kinase 1 mediates protection against Staphylococcus aureus infection

The interleukin-1 receptor-associated kinase-1 (IRAK-1) mediates signal transduction from Toll-like/IL-1/IL-18 receptors. Though a critical protective role against Staphylococcus aureus infection has been previously attributed to myeloid differentiation factor 88 (MyD88) and IRAK-4, both also involved in TLR/IL-1/IL-18 signaling, the role of IRAK-1 is unknown. IRAK-1-deficient (IRAK-1-/-) and wild-type mice were inoculated i.v. with 2 x 10(7) or 1 x 10(6) S. aureus per mouse to evaluate the role of IRAK-1 in S. aureus sepsis. Since IRAK-1 transduces IL-1R signals, IL-1R-/- mice were also included in experiments. IRAK-1-/- mice are susceptible to a high dose of S. aureus compared to wild-type controls. In contrast to the high mortality and extensive weight loss seen in IL-1R-deficient mice in response to 1 x 10(6) S. aureus, IRAK-1-/- mice are resistant to this low dose of S. aureus. Thus IRAK-1 plays an important role in the host response to staphylococcal sepsis.

De-novo design of complementary (antisense) peptide mini-receptor inhibitor of interleukin 18 (IL-18)

Complementary (antisense) peptide mini-receptor inhibitors are complementary peptides designed to be receptor-surrogates that act by binding to selected surface features of biologically important proteins thereby inhibiting protein-cognate receptor interactions and subsequent biological effects. Previously, we described a complementary peptide mini-receptor inhibitor of interleukin-1beta (IL-1beta) that was designed to bind to an external surface loop (beta-bulge) of IL-1beta (Boraschi loop) clearly identified in the X-ray crystal structure of this cytokine. Here, we report the de-novo design and rational development of a complementary peptide mini-receptor inhibitor of cytokine interleukin-18 (IL-18), a protein for which there is no known X-ray crystal structure. Using sequence homology comparisons with IL-1beta, putative IL-18 surface loops are identified and used as a starting point for design, including a loop region 1 thought to be equivalent with the Boraschi loop of IL-1beta. Only loop region 1 complementary peptides are found to be promising leads as mini-receptor inhibitors of IL-18 but these are prevented from being properly successful owing to solubility problems. The application of "M-I pair mutagenesis" and inclusion of a C-terminal arginine residue are then sufficient to solve this problem and convert one lead peptide into a functional complementary peptide mini-receptor inhibitor of IL-18. This suggests that the biophysical and biological properties of complementary peptides can be improved in a rational and logical manner where appropriate, further strengthening the potential importance of complementary peptides as inhibitors of protein-protein interactions, even when X-ray crystal structural information is not readily available.

Inhibition by interleukin-18 of the growth of Dunn osteosarcoma cells

To examine the usefulness of interleukin-18 (IL-18) in the treatment of osteosarcomas, the effect of IL-18 on the growth of Dunn osteosarcoma cells was investigated. Daily intraperitoneal (i.p.) injection of mouse recombinant IL-18 (2 microg/mouse) suppressed the growth of Dunn osteosarcoma cells transplanted subcutaneously (s.c.) into syngeneic C3H mice. This IL-18-induced suppression was not affected by simultaneous treatment with anti-asialo GM1 serum, which inactivates natural killer (NK) cells. However, IL-18 failed to suppress the growth of Dunn osteosarcoma cells transplanted into BALB/c-nude mice devoid of T lymphocytes or C3H-gld/gld mice deficient in functional Fas ligand (FasL). IL-18 also failed to suppress the growth of Dunn osteosarcoma cells in vitro, although expression of IL-18 receptor mRNA and MyD88 mRNA as well as Fas mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). On the other hand, antimouse Fas antibody showed cytotoxicity against Dunn osteosarcoma cells in a dose-dependent manner in vitro. In addition, treatment of C3H mice with IL-18 enhanced the cytotoxic activity of CD8(+) T lymphocytes against Dunn osteosarcoma cells. These results indicate that IL-18 inhibits the growth of Dunn osteosarcoma cells in vivo by enhancing the cytotoxic activity of CD8(+) T lymphocytes through the FasL-Fas system.

Blockade of IL-18 Receptor Signaling Delays the Onset of Autoimmune Disease in MRL-Faslpr Mice

Autoimmune disease in Fas-deficient MRL-Faslpr mice is dependent on infiltrating autoreactive leukocytes and autoantibodies, and IFN-gamma plays an important role in the pathogenesis. As IL-18 is capable of inducing IFN-gamma production in T cells, we hypothesized that signaling through IL-18R is involved in the pathogenesis. To investigate the impact of IL-18 in this autoimmune disease, we generated an MRL-Faslpr strain deficient in IL-18Ralpha. Compared with the wild-type strain, IL-18Ralpha-deficient MRL-Faslpr mice survived longer and showed a significant reduction in renal pathology, including glomerular IgG deposits, proteinuria, and serum anti-DNA Abs. Intrarenal transcripts encoding IFN-gamma, TNF-alpha, IL-12, and IL-10, which have been linked to nephritis, were all markedly reduced. Skin lesions, lymphadenopathy, and lung pathology characteristic of the MRL-Faslpr mouse disease were diminished in IL-18Ralpha-deficient MRL-Faslpr mice. Thus, we conclude that IL-18Ralpha signaling is critical to the pathogenesis of autoimmune disease in MRL-Faslpr mice.

Evidence for altered interleukin 18 (IL)-18 pathway in human heart failure

Interleukin (IL)-18 is the interferon-gamma-inducing factor and has potent proinflammatory activities. IL-18 has been recently implicated in atherosclerotic plaque instability and myocardial ischemia-reperfusion injury. However, it is unknown whether IL-18 expression is increased in human myocardium or if it has any role in heart failure. We analyzed the expression of IL-18, its receptor IL-18Ralpha, and its endogenous inhibitor, IL-18 binding protein (IL-18BP) in myocardial tissue from patients with end-stage heart failure (ischemic or dilated cardiomyopathy) and controls by use of quantitative real-time reverse transcriptase polymerase chain reaction, Western blot or immunohistochemical techniques. Plasma levels of IL-18 were also determined in 48 patients with heart failure. IL-18 mRNA and protein levels were up-regulated in the myocardium of patients with ischemic cardiomyopathy. Both ischemic and dilated myocardium showed increased IL-18Ralpha levels, suggesting potential biological effects. In addition, mRNA levels of IL-18 BP were down-regulated in the failing myocardium. Finally, plasma IL-18 levels were significantly elevated in patients with heart failure and were higher in those who died at follow-up than in survivors. The results suggest a potential role for the immunoinflammatory IL-18 signaling pathway in the pathophysiology of heart failure and identify novel therapeutic targets for future testing.

Heterogeneous expression of interleukin-18 and its receptor in B-cell lymphoproliferative disorders deriving from naive, germinal center, and memory B lymphocytes

PURPOSE

Dysregulated cytokine/cytokine receptor expression may occur in B-cell lymphoproliferative disorders. Little information is available on interleukin-18 receptor (IL-18R) and IL-18 expression in normal and malignant B cells. Our purpose was to investigate this issue in human naive, germinal center (GC) and memory B cells, and in their neoplastic counterparts.

EXPERIMENTAL DESIGN

We have evaluated IL-18 expression and production in tonsil naive, GC, and memory B cells and in their presumed neoplastic counterparts by reverse transcription-PCR and ELISA. Moreover, IL-18Ralpha and beta expression was investigated in the same cells by reverse transcription-PCR, flow cytometry, and immunohistochemistry.

RESULTS

We found that: (a) IL-18 mRNA was expressed in tonsil naive, GC, and memory B cells. Bioactive IL-18 was secreted by naive and GC, but not by memory B cells; (b) IL-18Ralpha and beta transcripts were expressed in the three B-cell subsets. IL-18Ralpha was detected on the surface of naive, GC, and memory B lymphocytes, and IL-18Rbeta was detected on GC and memory, but not naive, B cells; (c) mantle zone, follicular, marginal zone, Burkitt lymphoma (BL), and B-cell chronic lymphocytic leukemia (B-CLL) cells expressed IL-18 mRNA. B-CLL and BL cells did not produce bioactive IL-18; and (d) lymphoma B cells displayed heterogeneous expression of either or both IL-18R chain mRNA. In contrast, B-CLL cells expressed both IL-18R chains at the mRNA and protein levels.

CONCLUSIONS

Dysregulated expression of IL-18 and/or IL-18R in chronic B-cell lymphoproliferative disorders may sometimes contribute to tumor escape from the host immune system.

Paradoxical effects of interleukin-18 on the severity of acute graft-versus-host disease mediated by CD4+ and CD8+ T-cell subsets after experimental allogeneic bone marrow transplantation

Administration of exogenous interleukin-18 (IL-18) regulates experimental acute graft-versus-host disease (GVHD) in a Fas-dependent manner when donor CD4(+) T cells are required for mortality after experimental allogeneic bone marrow transplantation (BMT). However, CD4(+) and CD8(+) T cells can induce acute GVHD after clinical allogeneic BMT, and the role of IL-18 in CD8(+)-mediated acute GVHD is unknown. We, therefore, determined the role of IL-18 in GVHD mediated by CD4(+) or CD8(+) T cells across major histocompatibility complex (MHC) class II- and class I-disparate allogeneic BMT, respectively. Administering IL-18 significantly increased survival in CD4(+)-mediated GVHD but reduced survival in CD8(+)-mediated GVHD. This increase in deaths was associated with significantly greater clinical, biochemical, and histopathologic parameters of GVHD damage and was independent of Fas expression on donor T cells. Administering IL-18 significantly enhanced allospecific cytotoxic function and expansion of CD8(+) cells. Endogenous IL-18 was critical to GVHD mediated by CD8(+) donor T cells because IL-18 receptor-deficient donors caused significantly less GVHD but exacerbated CD4(+)-mediated, GVHD-related death. Furthermore, administering anti-IL-18 monoclonal antibody significantly reduced CD8(+)-mediated, GVHD-related death. Together these findings demonstrate that IL-18 has paradoxical effects on CD4(+) and CD8(+) cell-mediated GVHD.

Discrete roles for histone acetylation in human T helper 1 cell-specific gene expression

To better understand the control of T helper (TH) 1-expressed genes, we compared and contrasted acetylation and expression for three key genes, IFNG, TBET, and IL18RAP and found them to be distinctly regulated. The TBET and the IFNG genes, but not the IL18RAP gene, showed preferential acetylation of histones H3 and H4 during TH1 differentiation. Analysis of acetylation of specific histone residues revealed that H3(Lys-9), H4(Lys-8), and H4(Lys-12) were preferentially modified in TH1 cells, suggesting a possible contribution of acetylation of these residues for induction of these genes. On the other hand, the acetylation of IL18RAP gene occurred both in TH1 and TH2 cells the similar kinetics and on the same with residues, demonstrating that selective histone acetylation was not universally the case for all TH1-expressed genes. Histone H3 acetylation of IFNG and TBET genes occurred with different kinetics, however, and was distinctively regulated by cytokines. Interleukin (IL)-12 and IL-18 enhanced the histone acetylation of the IFNG gene. By contrast, histone acetylation of the TBET gene was markedly suppressed by IL-4, whereas IL-12 and IL-18 had only modest effects suggesting that histone acetylation during TH1 differentiation is a process that is regulated by various factors at multiple levels. By treating Th2 cells with a histone deacetylase inhibitor, we restored histone acetylation of the IFNG and TBET genes, but it did not fully restore their expression in TH2 cells, again suggesting that histone acetylation explains one but not all the aspects of TH1-specific gene expression.

Constitutive expression of interleukin-18 and interleukin-18 receptor mRNA in tumour derived human B-cell lines

Interleukin-18 (IL-18) is a pro-inflammatory cytokine involved in the Th1 immune response and expressed by a variety of cell types. IL-18 is a member of the IL-1 family and plays an important role in autoimmune diseases and inflammation. Using reverse transcriptase-polymerase chain reaction (RT-PCR) mRNA expression of IL-18, IL-18 receptor alpha (IL-18R alpha), and beta (IL-18R beta) were studied in tumour derived human B-cell lines. Furthermore, we investigated IL-18 protein secretion by using enzyme linked immunosorbent assay (ELISA). The results, as presented in this report, suggest that IL-18, IL-18R alpha, and IL-18R beta mRNA are constitutively and ubiquitously expressed in human B-cell lines, but secretion of the functional protein does not occur. We therefore speculate that IL-18 possibly affects B-cells through paracrine actions.

Sustained T-bet expression confers polarized human TH2 cells with TH1-like cytokine production and migratory capacities

BACKGROUND

The transcription factor T-bet mediates IFN-gamma production by T(H)1 cells and suppresses T(H)2 cytokine production when ectopically expressed in polarized murine T(H)2 cells. Thus T-bet-mediated inhibition of T(H)2 cytokine production might be beneficial for the treatment of allergic diseases like asthma or atopic dermatitis.

OBJECTIVE

We sought to investigate the effects of ectopic T-bet expression in highly polarized human T(H)2 cells obtained from skin biopsy specimens of patients with atopic dermatitis.

METHODS

The cytokine production of T(H)2 cells retrovirally transfected with a vector expressing human T-bet was determined by means of intracellular FACS staining and ELISA. The effects of T-bet transfection were analyzed at the mRNA level by means of real-time PCR and DNA microarrays and confirmed by using functional chemokine response assays.

RESULTS

Transfection of T-bet into T(H)2 cells induced high levels of IFN-gamma and suppressed IL-5, but IL-2 and IL-4 production remained unchanged. T-bet transfection also induced IL-12Rbeta2 and CXCR3 expression on human T(H)2 cells, whereas the IL-18 receptor was only induced as a consequence of T-bet-mediated increased responsiveness to IL-12. Furthermore, sustained T-bet expression in human T(H)2 cells induced IL-2 production and decreased the secretion of IL-4. In addition, the chemokine receptor repertoire of these cells was changed toward a T(H)1-like profile.

CONCLUSION

The combined switch in cytokine pattern and migratory potential of highly polarized human T(H)2 cells mediated by T-bet might provide an additional advantage for the treatment of allergic diseases.

The IL-1 receptor accessory protein is essential for PI 3-kinase recruitment and activation

Interleukin-1 (IL-1) binds to its type I receptors (IL-1R), which in complex with IL-1R accessory protein (IL-1R AcP) induces various intracellular signaling events. We report here that IL-1 triggers the recruitment of phosphoinositide 3-kinase (PI 3-kinase) to a signaling complex and induces its lipid kinase activity in a biphasic manner. This IL-1-induced complex consists of IL-1R, IL-1R AcP, PI 3-kinase, and the IL-1-receptor-associated kinase (IRAK). Deletion of the C-terminus 27 amino acids of IL-1R AcP resulted in a mutant, CDelta27, that could not recruit PI 3-kinase to the signalsome nor stimulate PI3-kinase activity. Moreover, CDelta27 functioned as a dominant-negative mutant that inhibited IL-1-induced PI 3-kinase and NFkappaB activation. CDelta27, however, had no effect on IL-1-dependent activation of the Jun N-terminal kinase (JNK), indicating that distinct regions of IL-1R AcP mediate the activation of PI 3-kinase and JNK. Thus, our results identified a functional region in the IL-1R AcP required for the recruitment and activation of PI 3-kinase.

Distinct modulatory effects of LPS and CpG on IL-18-dependent IFN-gamma synthesis

Innate cellular production of IFN-gamma is suppressed after repeated exposure to LPS, whereas CpG-containing DNA potentiates IFN-gamma production. We compared the modulatory effects of LPS and CpG on specific cellular and cytokine responses necessary for NK-cell dependent IFN-gamma synthesis. C3H/HeN mice pretreated with LPS for 2 days generated 5-fold less circulating IL-12 p70 and IFN-gamma in response to subsequent LPS challenge than did challenged control mice. In contrast, CpG-pretreated mice produced 10-fold more circulating IFN-gamma without similar changes in IL-12 p70 levels, but with 10-fold increases in serum IL-18 relative to LPS-challenged control or endotoxin-tolerant mice. The role of IL-18 in CpG-induced immune potentiation was studied in splenocyte cultures from control, LPS-conditioned, or CpG-conditioned mice. These cultures produced similar amounts of IFN-gamma in response to rIL-12 and rIL-18. However, only CpG-conditioned cells produced IFN-gamma when cultured with LPS or CpG, and production was ablated in the presence of anti-IL-18R Ab. Anti-IL-18R Ab also reduced in vivo IFN-gamma production by >2-fold in CpG-pretreated mice. Finally, combined pretreatment of mice with LPS and CpG suppressed the production of circulating IFN-gamma, IL-12 p70, and IL-18 after subsequent LPS challenge. We conclude that CpG potentiates innate IFN-gamma production from NK cells by increasing IL-18 availability, but that the suppressive effects of LPS on innate cellular immunity dominate during combined LPS and CpG pretreatment. Multiple Toll-like receptor engagement in vivo during infection can result in functional polarization of innate immunity dominated by a specific Toll-like receptor response.

The molecular evolution of the interleukin-1 family of cytokines; IL-18 in teleost fish

The cytokine network is an important homeostatic system with potent activities in immune surveillance, growth, developmental and repair processes. Although interleukin-1beta (IL-1beta) is considered a pivotal pro-inflammatory cytokine, merely focussing on its inflammatory role would be too narrow an approach. Elucidation of the human, the mouse and the Fugu rubripes (pufferfish) genome now enables a more comprehensive overview of this cytokine family and its receptors in several vertebrate classes. Phylogenetic analyses of the IL-1 family members, comprising over 80 sequences of various fish, amphibian, avian and mammalian species, reveal that for only a few mammalian IL-1 family members unambiguous orthologues have been found in fish, indicating a recent origin of some of the mammalian IL-1 family members. Interestingly, the Fugu genome did reveal teleost orthologues for IL-18 and its putative receptor complex. All teleost IL-1beta sequences cluster separately from IL-1beta sequences of other species. In contrast, a number of IL-1 receptor family members have well conserved fish orthologues. This supports the concept of an ancestral role of this family, possibly in the brain.

The interleukin 1 receptor family

Interleukin-1 is a key inflammatory cytokine that mediates its effects through a type I receptor and a receptor accessory protein. These two molecules are members of a wider family of proteins that have in common the presence of immunoglobulin domains in the extracellular region of the protein and a TIR domain in the cytoplasmic region. The nature of this family of proteins and their signal transduction pathway is discussed in this review.

Differential Upregulation of Interleukin-18 Receptor α Chain Between CD4+ and CD8+ T Cells During Acute Graft-Versus-Host Disease in Mice

Interleukin-18 (IL-18), a unique cytokine that stimulates both T helper 1 (Th1) and Th2 responses, is associated with acute graft-versus-host disease (aGVHD), the major limiting toxicity following allogeneic stem cell transplantation. Here, we investigated the mechanism underlying the upregulation of IL-18 receptor (IL-18R) expression on T cells in murine aGVHD models. The induction of aGVHD elevated host serum IL-12 levels and increased expression of IL-18Ralpha chain (IL-18Ralpha) on engrafted T cells, in particular on CD8+ T cells. However, IL-18Ralpha expression did not increase on the CD4+ T cells of an IL-12-deficient host, indicating the IL-12-dependent upregulation of IL-18Ralpha expression on CD4+ T cells during aGVHD. Purified donor CD8+ T cells transferred in the host increased IL-18Ralpha expression. In vitro experiments showed that IL-18Ralpha expression upregulated on CD8+ T cells but not on CD4+ T cells on stimulation through the T cell receptor (TCR). These results suggest that IL-18Ralpha expression is differentially upregulated between CD4+ and CD8+ T cells during aGVHD, depending on endogenous IL-12 and TCR engagement, respectively.

Generation of highly stable IL-18 based on a ligand–receptor complex structure

Human interleukin-18 (hIL-18), initially cloned as an IFN-gamma-inducing factor, has a key role in many inflammatory diseases. We have previously developed a high production system for correctly folded active hIL-18 protein, leading to the revelation of the 3D-structure and the receptor binding mode. These findings can strongly indicate the experimental and medical applications of IL-18; however, the recombinant protein is prone to be inactivated forming multimers. Recently, therapeutic approaches using recombinant IL-18 have shown the effectiveness for treatment of cancer; indicating the necessity of a more stable protein for therapy with intertrial reliability. Here we have generated a highly stable hIL-18 with replacement of cysteine by serine based on the tertiary structure and the binding mechanism, retaining the biological activity. Similar rational designs can be applied to develop new therapeutic molecules of other cytokines.

Interleukin-18 induces serum amyloid A (SAA) protein production from rheumatoid synovial fibroblasts

Interleukin-18 (IL-18) is a novel proinflammatory cytokine that was recently found in synovial fluids and synovial tissues from patients with rheumatoid arthritis (RA). To investigate the role of IL-18 in rheumatoid synovitis, the levels of IL-18 and serum amyloid A (SAA) were measured in synovial fluids from 24 patients with rheumatoid arthritis (RA) and 13 patients with osteoarthritis (OA). The levels of IL-18 and SAA in the synovial fluids were elevated in RA patients. In contrast, the levels of IL-18 in synovial fluids from OA patients were significantly lower compared to those of RA patients. SAA was not detected in synovial fluids from OA patients. The expression of SAA mRNA in rheumatoid synovial cells was also examined. SAA4 mRNA, which was constitutively expressed by rheumatoid synovial cells, was not affected by IL-18 stimulation. Although acute phase SAA (A-SAA, SAA1 + 2) mRNA was not detected in unstimulated synovial cells, its expression was induced by IL-18 stimulation. By immunoblot, we demonstrated that IL-18 induced the SAA protein synthesis from rheumatoid synovial cells in a dose-dependent manner. These results indicate a novel role for IL-18 in rheumatoid inflammation through the synovial SAA production.