Regulation of human IL-18 mRNA expression

Mechanistic insights from inflammasome structures

Inflammasomes are supramolecular complexes that form in the cytosol in response to pathogen-associated and damage-associated stimuli, as well as other danger signals that perturb cellular homoeostasis, resulting in host defence responses in the form of cytokine release and programmed cell death (pyroptosis). Inflammasome activity is closely associated with numerous human disorders, including rare genetic syndromes of autoinflammation, cardiovascular diseases, neurodegeneration and cancer. In recent years, a range of inflammasome components and their functions have been discovered, contributing to our knowledge of the overall machinery. Here, we review the latest advances in inflammasome biology from the perspective of structural and mechanistic studies. We focus on the most well-studied components of the canonical inflammasome - NAIP-NLRC4, NLRP3, NLRP1, CARD8 and caspase-1 - as well as caspase-4, caspase-5 and caspase-11 of the noncanonical inflammasome, and the inflammasome effectors GSDMD and NINJ1. These structural studies reveal important insights into how inflammasomes are assembled and regulated, and how they elicit the release of IL-1 family cytokines and induce membrane rupture in pyroptosis.

Increased Interleukin 18-Dependent Immune Responses Are Associated With Myopericarditis After COVID-19 mRNA Vaccination

Myocarditis and myopericarditis may occur after COVID-19 vaccination with an incidence of two to twenty cases per 100,000 individuals, but underlying mechanisms related to disease onset and progression remain unclear. Here, we report a case of myopericarditis following the first dose of the mRNA-1273 COVID-19 vaccine in a young man who had a history of mild COVID-19 three months before vaccination. The patient presented with chest pain, elevated troponin I level, and electrocardiogram abnormality. His endomyocardial biopsy revealed diffuse CD68⁺ cell infiltration. We characterized the immune profile of the patient using multiplex cytokine assay and flow cytometry analysis. Sex-matched vaccinated individuals and healthy individuals were used as controls. IL-18 and IL-27, Th1-type cytokines, were highly increased in the patient with COVID-19 vaccine-related myopericarditis compared with vaccinated controls who experienced no cardiac complications. In the patient, circulating NK cells and T cells showed an activated phenotype and mRNA profile, and monocytes expressed increased levels of IL-18 and its upstream NLRP3 inflammasome. We found that recombinant IL-18 administration into mice caused mild cardiac dysfunction and activation of NK cells and T cells in the hearts, similar to the findings in the patient with myopericarditis after COVID-19 mRNA vaccination. Collectively, myopericarditis following COVID-19 mRNA vaccination may be associated with increased IL-18-mediated immune responses and cardiotoxicity.

Evaluation the ability of acellular ovine small intestine submucosa to load and release of mineral pitch and its anti-inflammatory effects

Injury from the severe burn is exacerbated by a persistent inflammatory response. This response is mediated by cytokines and chemokines, which are released from various immune cells, including mast cells. In this study, the ability of the acellular ovine small intestine submucosa (AOSIS) to load and release of Mineral Pitch (MP) was first investigated, and it was found that the preparation of the scaffold by a modified method enables it to load and release water-soluble drugs. Then, 32 male Wistar rats were divided into four groups, a third-degree burn was created, and except for the control group, the others were treated with: AOSIS, WJ-MSCs seeded AOSIS, or AOSIS loaded with WJ-MSCs and MP. Wound sampling on the 5th day after treatment showed that the number of intact and degranulated mast cells in the treatment groups was associated with a decrease compared to the control group. In the last group, this decrease was the largest (and statically significant (p < 0.05)). Also, by measuring the level of inflammatory factors in blood serum, it was found that in the treatment groups compared to the control group, IL-10 was associated with an increase, and TNF-α was associated with a decrease. The changes in inflammatory factors were more significant (p < 0.05) in the last group. So, our results indicate that AOSIS loaded with WJ-MSCs and MP could be used as an innovative tissue-engineered device to control inflammatory condition during burn wound healing.

Proteomics reveals distinct mechanisms regulating the release of cytokines and alarmins during pyroptosis

A major pathway for proinflammatory protein release by macrophages is inflammasome-mediated pyroptotic cell death. As conventional secretion, unconventional secretion, and cell death are executed simultaneously, however, the cellular mechanisms regulating this complex paracrine program remain incompletely understood. Here, we devise a quantitative proteomics strategy to define the cellular exit route for each protein by pharmacological and genetic dissection of cellular checkpoints regulating protein release. We report the release of hundreds of proteins during pyroptosis, predominantly due to cell lysis. They comprise constitutively expressed and transcriptionally induced proteins derived from the cytoplasm and specific intracellular organelles. Many low-molecular-weight proteins including the cytokine interleukin-1β, alarmins, and lysosomal-cargo proteins exit cells in the absence of cell lysis. Cytokines and alarmins are released in an endoplasmic reticulum (ER)-Golgi-dependent manner as free proteins rather than by extracellular vesicles. Our work provides an experimental framework for the dissection of cellular exit pathways and a resource for pyroptotic protein release.

Synergistic Signaling of TLR and IFNα/β Facilitates Escape of IL-18 Expression from Endotoxin Tolerance

Rationale: IL-18 is a member of the IL-1 cytokine family, and elevated blood IL-18 concentrations associate with disease activity in macrophage activation syndrome (MAS) and poor clinical outcomes in severe inflammatory and septic conditions.

Objectives: Although recent investigations provide mechanistic evidence for a contribution of IL-18 to inflammation and hyperinflammation in sepsis and MAS, we sought to study regulatory mechanisms underlying human IL-18 expression.

Methods: Samples from in vivo and in vitro endotoxin rechallenge experiments, patients with inflammatory disease, and isolated human monocytes treated with various stimulants and drugs were tested for cytokine gene and protein expression. Serum IL-18 expression with or without JAK/STAT inhibition was analyzed in two MAS mouse models and in a patient with recurrent MAS.

Measurements and Main Results: Peripheral blood and monocytic IL-18 expression escaped LPS-induced immunoparalysis. LPS-stimulated primary human monocytes revealed specific IL-18 expression kinetics controlled by IFNα/β signaling. JAK/STAT inhibition or IFNβ neutralization during LPS stimulation blunted cytokine expression. Similarly, microtubule-destabilizing drugs abrogated LPS-induced IL18 expression, but this effect could be fully reversed by addition of IFNα/β. Ex vivo analysis of inflammatory disease patients’ whole blood revealed strong correlation of type I IFN score and IL18 expression, whereas JAK/STAT inhibition strongly reduced IL-18 serum levels in two MAS mouse models and in a patient with recurrent MAS.

Conclusions: Our data indicate that IL-18 (but not IL-1β) production from human monocytes requires cooperative Toll-like receptor and IFNα/β signaling. Interference with IFNα/β expression or signaling following JAK/STAT inhibition may control catastrophic hyperinflammation in MAS.

Toward targeting inflammasomes: insights into their regulation and activation

Inflammasomes are multi-component signaling complexes critical to the initiation of pyroptotic cell death in response to invading pathogens and cellular damage. A number of innate immune receptors have been reported to serve as inflammasome sensors. Activation of these sensors leads to the proteolytic activation of caspase-1, a proinflammatory caspase responsible for the cleavage of proinflammatory cytokines interleukin-1β and interleukin-18 and the effector of pyroptotic cell death, gasdermin D. Though crucial to the innate immune response to infection, dysregulation of inflammasome activation can lead to the development of inflammatory diseases, neurodegeneration, and cancer. Therefore, clinical interest in the modulation of inflammasome activation is swiftly growing. As such, it is imperative to develop a mechanistic understanding of the regulation of these complexes. In this review, we divide the regulation of inflammasome activation into three parts. We discuss the transcriptional regulation of inflammasome components and related proteins, the post-translational mechanisms of inflammasome activation, and advances in the understanding of the structural basis of inflammasome activation.

Defective Inflammatory Pathways in Never-Treated Depressed Patients Are Associated with Poor Treatment Response

Inflammation has been involved in the pathophysiology and treatment response of major depressive disorder (MDD). Plasma cytokine profiles of 171 treatment-naive MDD patients (none of the MDD patients received an adequate trial of antidepressants or evidence-based psychotherapy) and 64 healthy controls (HCs) were obtained. MDD patients exhibited elevated concentrations of 18 anti- and proinflammatory markers and decreased concentrations of 6 cytokines. Increased inflammasome protein expression was observed in MDD patients, indicative of an activated inflammatory response. The plasma of MDD patients was immunosuppressive on healthy donor peripheral blood mononuclear cells, inducing reduced activation of monocytes/dendritic cells and B cells and reduced T cell memory. Comparison between 33 non-responders and 71 responders at baseline and 12 weeks revealed that after treatment, anti-inflammatory cytokine levels increase in both groups, whereas 5 proinflammatory cytokine levels were stabilized in responders, but continued to increase in non-responders. MDD patients exhibit remodeling of their inflammatory landscape.

Cutting Edge: Distinct Regulatory Mechanisms Control Proinflammatory Cytokines IL-18 and IL-1β

Interleukin-18 and IL-1β, which are cytokines of the IL-1 family, are synthesized as precursor proteins and activated by the inflammasome via proteolytic processing. IL-1β is only induced in response to inflammatory stimuli, but IL-18 is constitutively expressed. However, how IL-18 and IL-1β expression is regulated by different inflammatory signals remains poorly studied. In this study, we found that IL-18 and IL-1β are differentially regulated. Despite being constitutively expressed, IL-18 expression was increased and sustained after stimulation of TLRs. In contrast, IL-1β was induced but not sustained after chronic treatment. Furthermore, type I IFN signaling was essential for induction of IL-18 and macrophages lacking type I IFN signaling were impaired in their ability to promote IL-18 induction. Thus, our findings reveal a fundamental difference in IL-18 and IL-1β regulation and uncover novel mechanisms that are relevant to the inflammatory settings where these proinflammatory cytokines play a critical role.

Effects of the stem extracts of Schisandra glaucescens Diels on collagen-induced arthritis in Balb/c mice

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra glaucescens Diels (SGD) is used in a subclass of traditional Chinese medicine known as "Tujia drugs". It has been long used for the treatment of rheumatoid arthritis (RA), cough with dyspnea, spontaneous sweating, night sweating, chronic diarrhea, and neurasthenia. As a woody liana growing in mountain jungles at the altitudes of 750-1800m, it is mainly distributed in Sichuan and Hubei Provinces of China.

AIM OF THE STUDY

To evaluate the antiarthritic activity of acetate (EA) and n-butanol (Bu) fractions of SGD extract on a collagen-induced arthritis mice model.

MATERIALS AND METHODS

Acute toxicity of EA and Bu fractions of SGD extract was evaluated by gavage on normal mice. Pharmacological investigations were conducted on arthritis male Balb/c mice. The animal model was induced by immunization with type II bovine collagen (CII) on the 1st and the 14th day of the experimental schedule. EA fraction (104, 312, 936mg/kg), Bu fraction (156, 469, 1407mg/kg) of SGD extract was orally administered every two days since the 15th day for 3 weeks. Progression of edema in the paws was measured using a vernier caliper every 3 days since the 10th day. At the end of the experiment, the spleen index and histological changes of the hind knee joints were investigated. Additionally, to explore the possible antirheumatic mechanisms of the EA and Bu fractions, ELISA was carried out to analyze TNF-α, IL-10, IL-6 and IL-1β in the serum.

RESULTS

The half lethal doses of both EA and Bu fractions were much higher than the dose administered in the pharmacological investigations. Oral administration of EA fraction and Bu fraction of SGD extract significantly and does-dependently inhibited type ІІ collagen induced arthritis (CIA) in mice, as indicated by the effects on paws swelling and spleen index. Histopathological examinations demonstrated that SGD effectively protected the bones and cartilages of knee joints from erosion, lesion and deformation. Besides, the serum concentrations of cytokines TNF-α, IL-1β and IL-6 were significantly lower than the ones from the vehicle control group. Respectively, while cytokine IL-10 was remarkably higher compare with the vehicle control group.

CONCLUSIONS

SGD might be a safe and effective candidate for the treatment of RA, and deserves further investigation on the chemical components in both EA and Bu fractions of SGD extract.

Cytokines and Chemokines in Mycobacterium tuberculosis Infection

Chemokines and cytokines are critical for initiating and coordinating the organized and sequential recruitment and activation of cells into Mycobacterium tuberculosis-infected lungs. Correct mononuclear cellular recruitment and localization are essential to ensure control of bacterial growth without the development of diffuse and damaging granulocytic inflammation. An important block to our understanding of TB pathogenesis lies in dissecting the critical aspects of the cytokine/chemokine interplay in light of the conditional role these molecules play throughout infection and disease development. Much of the data highlighted in this review appears at first glance to be contradictory, but it is the balance between the cytokines and chemokines that is critical, and the "goldilocks" (not too much and not too little) phenomenon is paramount in any discussion of the role of these molecules in TB. Determination of how the key chemokines/cytokines and their receptors are balanced and how the loss of that balance can promote disease is vital to understanding TB pathogenesis and to identifying novel therapies for effective eradication of this disease.

Interleukin 18: a biomarker for differential diagnosis between adult-onset Still's disease and sepsis

OBJECTIVE

The differential diagnosis between rheumatic diseases and infectious conditions is a great challenge in clinical practice. Adult-onset Still's disease (AOSD) is a rare systemic inflammatory syndrome that shares several clinical and laboratory variables with sepsis. Interleukin (IL)-18 is overexpressed in AOSD, suggesting a possible role as a disease biomarker. The aim of our study was to detect IL-18 serum levels in a cohort of patients with AOSD and sepsis and to address its possible role as a biomarker for differential diagnosis.

METHODS

A group of unselected patients with AOSD diagnosed according to the Yamaguchi criteria and consecutive patients with sepsis diagnosed according to the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference criteria were enrolled. The clinical and laboratory data were collected. In the AOSD group, disease activity was assessed by Pouchot's and Rau's criteria. IL-18 serum levels were detected by ELISA.

RESULTS

Thirty-nine patients with AOSD and 18 patients with sepsis were enrolled. Two out of 18 patients with sepsis (11.1%) also fulfilled the Yamaguchi criteria. A significant difference was found in IL-18 serum levels between patients with active and inactive disease (p < 0.001), and it positively correlated with disease activity (p = 0.0003), ferritin serum level (p = 0.016), and erythrocyte sedimentation rate (p = 0.041). IL-18 was significantly increased in patients with AOSD when compared with sepsis (p = 0.014). For a cutoff of 148.9 pg/ml, this test had a specificity of 78.3% and a sensitivity of 88.6%.

CONCLUSION

We have demonstrated that IL-18 can be a biomarker for differential diagnosis between AOSD and sepsis.

Association of interleukin-18 (-137G/C) polymorphism with rheumatoid arthritis and systemic lupus erythematosus: a meta-analysis

BACKGROUND

Recent studies have suggested that interleukin (IL)-18 gene (-137G/C) polymorphism is associated with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, other studies did not confirm this correlation.

OBJECTIVE

The objective of this study was to evaluate the relationships of IL-18 -137G/C and RA and SLE using a meta-analysis.

METHODS

Pubmed, Embase and Cochrane library databases were systemically searched. Data were extracted by two independent reviewers and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated.

RESULTS

In RA, the overall ORs and 95% CIs of -137C were 1.03, 0.88-1.22 (p=0.391); 1.22, 0.89-1.68 (p=0.020) and 1.06, 0.93-1.21 (p=0.110) in dominant, recessive, and additive models, respectively. Furthermore, in SLE, the overall ORs and 95% CIs of -137C were 1.10, 0.94-1.29 (p=0.980); 1.21, 0.91-1.60 (p=0.010) and 1.10, 0.97-1.24 (p=0.454) in dominant, recessive, and additive models, respectively. IL-18 -137G/C could increase the risk of RA and SLE. No publication bias was found in this meta-analysis. After population stratification analysis, under recessive model, the pooled ORs and 95% CIs of -137C were 1.14, 0.82-1.60 (p=0.008) and 1.01, 0.66-1.55 (p=0.004) in European RA patients and Asian SLE patients, respectively.

CONCLUSIONS

This meta-analysis showed that IL-18 -137G/C was a risk factor for RA and SLE, especially for RA in Europeans and SLE in Asians.

Inflammatory cell response to calcium phosphate biomaterial particles: an overview

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite (HA) and amorphous calcium phosphate (CaP) crystals deposited in an organic matrix. One objective of bone tissue engineering is to mimic the chemical and structural properties of this complex tissue. CaP ceramics, such as sintered HA and beta-tricalcium phosphate, are widely used as bone substitutes or prosthesis coatings because of their osteoconductive properties. These ceramic interactions with tissues induce a cell response that can be different according to the composition of the material. In this review, we discuss inflammatory cell responses to CaP materials to provide a comprehensive overview of mechanisms governing the integration or loosening of implants, which remains a major concern in tissue engineering. A focus on the effects of the functionalization of CaP biomaterials highlights potential ways to increase tissue integration and limit rejection processes.

Long-term dynamic profiling of inflammatory mediators in double-hit burn and sepsis animal models

Burn injuries together with its subsequent complications, mainly bacterial infections originating from gastrointestinal tract, activate the host immune system through stimulation of a series of local and systemic responses, including the release of inflammatory mediators. To gain a more comprehensive understanding of these complex physiological changes and to propose therapeutic approaches to combat the deleterious consequences of burn and septic shocks, it is essential to analyze animal models of burn and sepsis. In this study, we analyzed the long term profiles of cytokines and chemokines in rat models which received burn injury followed 2 days later by cecal ligation and puncture (CLP) to induce sepsis and were sacrificed at different time points within 10 days (0, 1, 2, 3, 4, 7 and 10 days). It was observed that MCP-1 concentrations were elevated in all animal models following the burn injury or CLP treatment. IP-10 concentration was persistently decreased after CLP or sham-CLP treatments. GRO/KC concentration was also increased following the burn injury and CLP. It was elucidated that, in more severe injury model which received both burn and CLP treatments, GMCSF and MIP-1α (chemokines), IL-1α (a pro-inflammatory cytokine) and IL-6 (exhibiting both pro- and anti-inflammatory behaviors) were upregulated on the 7th and 10th days, which might be to protect the host system from the subsequent complications caused by burn and sepsis. In order to elucidate critical regulatory interactions, putative transcription factors of the inflammatory mediators which have been significantly changed following the injuries were further identified by analyzing the conserved regions of the promoters of cytokines and chemokines. In conclusion, the long term profiles of the inflammatory mediators were profoundly characterized in this study to gain a comprehensive understanding of inflammatory mediators' behaviors in various injury models.

Comparison of the cytokine and chemokine dynamics of the early inflammatory response in models of burn injury and infection

The inflammatory response, and its subsequent resolution, are the result of a very complex cascade of events originating at the site of injury or infection. When the response is severe and persistent, Systemic Inflammatory Response Syndrome can set in, which is associated with a severely debilitating systemic hypercatabolic state. This complex behavior, mediated by cytokines and chemokines, needs to be further explored to better understand its systems properties and potentially identify multiple targets that could be addressed simultaneously. In this context, short term responses of serum cytokines and chemokines were analyzed in two types of insults: rats receiving a "sterile" cutaneous dorsal burn on 20% of the total body surface area (TBSA); rats receiving a cecum ligation and puncture treatment (CLP) to induce infection. Considering the temporal variability observed in the baseline corresponding to the control group, the concept of area under the curve (AUC) was explored to assess the dynamic responses of cytokines and chemokines. MCP-1, GROK/KC, IL-12, IL-18 and IL-10 were observed in both burn and CLP groups. While IL-10 concentration was only increased in the burn group, Eotaxin was only elevated in CLP group. It was also observed that Leptin and IP-1 concentrations were decreased in both CLP and sham-CLP groups. The link between the circulating protein mediators and putative transcription factors regulating the cytokine/chemokine gene expression was explored by searching the promoter regions of cytokine/chemokine genes in order to characterize and differentiate the inflammatory responses based on the dynamic data. Integrating multiple sources together with the bioinformatics tools identified mediators sensitive to type and extent of injury, and provided putative regulatory mechanisms. This is essential to gain a better understanding for the important regulatory points that can be used to modulate the inflammatory state at molecular level.

Increased Spontaneous But Decreased Mitogen-stimulated Expression and Excretion of Interleukin 18 by Mononuclear Cells in Patients with Active Systemic Lupus Erythematosus

Objective.

To measure serum concentration and analyze the expression of interleukin 18 (IL-18) mRNA in mononuclear cells of patients with systemic lupus erythematosus (SLE).

Methods.

IL-18 concentrations in sera and culture supernatants of peripheral blood mononuclear cells (PBMC) from healthy controls and patients with active SLE were measured by ELISA. PBMC and polymorphonuclear leukocytes (PMN) purified from patients with active SLE were stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM), and lipopolysaccharide (LPS). Expression of IL-18 mRNA in cells was analyzed by RT-PCR.

Results.

Serum IL-18 levels were significantly higher in SLE patients than in controls, and correlated with disease activity in SLE patients (r2 = 0.602). Two patients receiving intravenous methylprednisolone therapy (1.0 g/day for 3 days) showed profound decreases in serum IL-18 levels after therapy. The quiescent PBMC from SLE patients (30/30) expressed IL-18 transcript more frequently than control PBMC (20/30). PBMC from SLE patients produced more IL-18 than control PBMC after 72 hours of incubation, by RT-PCR. PHA and PWM inhibited the production of IL-18 in PBMC from both SLE patients and controls. Inhibition by PWM was more pronounced than that by PHA, especially in SLE-PBMC. Control and SLE-PMN with or without LPS stimulation produced negligible IL-18.

Conclusion.

IL-18 is involved in the autoimmune derangement of leukocyte function in patients with active SLE.

Postoperative suppression of inflammatory cytokines after distal gastrectomy in elderly patients

PURPOSE

Surgical procedures are being performed on elderly people with increasing frequency, but accordingly, postoperative complications and mortality rates are higher than for younger patients. We conducted this study to establish if cytokine responses after distal gastrectomy in elderly patients differ from those in younger patients.

METHODS

Twenty-one patients undergoing distal gastrectomy were divided into two groups based on age: the elderly group consisted of 10 patients aged >/=75 years, and the younger group consisted of 11 patients aged <65 years. Blood samples were collected from the patients preoperatively, and then on postoperative days (PODs) 1, 3, and 7, for analysis of interleukin (IL)-6, IL-8, IL-10, soluble tumor necrosis factor receptors (sTNF-R), and IL-1 receptor antagonist (IL-1ra); and also to measure TNF-alpha and IL-1beta after incubation with Escherichia coli lipopolysaccharide.

RESULTS

The IL-6 concentration and TNF-alpha on POD 1 were both significantly lower in the elderly group than in the younger group (P = 0.0058 and P = 0.022, respectively).

CONCLUSION

Cytokine profiles after distal gastrectomy in elderly patients differ from those in younger patients, with lower pro-inflammatory and inflammatory cytokine responses evident in the elderly.

Interleukin-18 gene 105A/C genetic polymorphism is associated with the susceptibility of Kawasaki disease

Interleukin-18 (IL-18)-656T/G, -607A/C, and -137C/G promoter polymorphisms had been reported associated with Kawasaki disease (KD). An IL-18 genetic A/C polymorphism at coding position 105 (rs549908) has been linked with asthma, rheumatoid, and systemic lupus erythematosus. We tested a hypothesis that the IL-18 105A/C genetic polymorphism confers KD susceptibility. Study participants were Taiwanese KD patients and a healthy control group. Our data indicated that the frequency of C allele was significantly higher in the patient group (13.9%) than in the control group (2.7%; P<0.0001, odds ratio [OR]=5.93; 95% confidence interval [CI]=2.57-13.73). Therefore, persons with the C allele may have higher risk of developing KD. In addition, compared with the haplotype frequencies between case and control groups, the KD patients with TACC haplotype appeared to be a significant "at-risk" haplotype compared with other haplotypes (OR: 4.62, 95% CI: 1.71-12.43; P=0.001). KD patient with the TAGA haplotype appeared to be a significant "protective" haplotype compared with other haplotypes (OR: 0.51, 95% CI:0.29-0.89; P=0.017). Our results suggest that 105A/C polymorphism and the haplotypes in IL-18 gene are associated with the risk of KD in Taiwanese population.

Autocrine role of endogenous interleukin-18 on inflammatory cytokine generation by human neutrophils

Neutrophils are key players of innate immunity and influence inflammatory and immune reactions through the production of numerous cytokines. Interleukin-18 (IL-18) is known to stimulate several neutrophil responses, and recent evidence suggests that neutrophils might represent a source of IL-18. Here, we show that neutrophils constitutively produce both IL-18 and its antagonist, IL-18BP. Cell activation does not affect IL-18BP release but leads to an increased gene expression and secretion of IL-18, a process that depends on NF-kappaB activation. Moreover, endogenous IL-18 feeds back on the neutrophils to augment cytokine generation in lipopolysaccharide-treated cells. Accordingly, exogenous IL-18 can induce the gene expression and release of several inflammatory cytokines in neutrophils, including its own expression. We finally report that IL-18 activates the p38 MAPK, MEK/ERK, and PI3K/Akt pathways in neutrophils. The IKK cascade is also activated by IL-18, resulting in IkappaB-alpha degradation, NF-kappaB activation, and RelA phosphorylation. Accordingly, these pathways contribute to the generation of inflammatory cytokines in IL-18-stimulated neutrophils. By contrast, the phosphorylation and DNA-binding activity of various STAT proteins were not induced by IL-18. Collectively, our results unveil new interactions between IL-18 and neutrophils and further support a role for these cells in influencing both innate and adaptive immunity.

Disease association of the interleukin-18 promoter polymorphisms in Taiwan Chinese systemic lupus erythematosus patients

Interleukin (IL)-18, an important mediator of innate and adaptive immunity, plays multiple roles in chronic inflammation, in autoimmune diseases, in a variety of cancers and in number of infectious diseases. IL-18 promoter polymorphisms have been also noted associated with various inflammatory diseases. We investigated the association of IL-18 promoter polymorphisms (-656T/G, -607A/C and -137C/G) with systemic lupus erythematosus (SLE) in Taiwan Chinese patients and controls. Six haplotypes (hts) were identified from the three promoter polymorphisms. The genotype distribution of the ht1 (GCC), ht2 (TAC), ht4 (GAC) and ht5 (TCC) were different in patients and controls (P<0.002). Moreover, the haplotype and genotype frequencies of ht1 were significantly increased in patients with discoid rash (P=0.045, odds ratio (OR): 2.01, 95% confidence interval (CI): 1.01-4.00; P=0.027, OR: 5.13, 95% CI: 1.41-18.68). In addition, the homozygous genotype ht1/ht1 was significant increased in patients with serositis (P=0.015, OR: 9.78, 95% CI: 1.55-61.73). These observations suggest that the three promoter polymorphisms contribute to the genetic background of SLE pathogenesis.

Immunomodulatory activity of the rhizomes of Impatiens pritzellii var. hupehensis on collagen-induced arthritis mice

Impatiens pritzellii Hook. f. var. hupehensis Hook. f. (Balsaminaceae) has been well-known and widely used in China as an anti-rheumatoid arthritis (anti-RA) herb. In this present study, mice with collagen-induced arthritis (CIA) have been treated with the methanol (MeOH) extract (0.56, 1.12, 1.68 and 2.24 g/kg body weight) and the n-butanol (BuOH) fraction (0.13, 0.27, 0.40 and 0.53 g/kg body weight) of the rhizomes of Impatiens pritzellii orally for 3 weeks. The progression of CIA was evaluated by macroscopic scoring. Administration of the MeOH extract at dose of 1.12 g/kg and the BuOH fraction at 0.53 g/kg suppressed the development of CIA in mice significantly. The spleen and thymus indexes were measured and the levels of IgG, IL-10, INF-gamma and IL-18 in the serum of CIA mice were examined after the treatment of the MeOH extract (1.12 and 1.68 g/kg body weight) and the BuOH fraction (0.40 and 0.53 g/kg body weight). Administration of the MeOH extract and the BuOH fraction of Impatiens pritzellii decreased the spleen and thymus indexes, down-regulated the levels of IgG, INF-gamma, IL-18, and up-regulated the concentration of IL-10 in the serum of mice with CIA. From the results, it was concluded that administration of Impatiens pritzellii had obviously therapeutic effects on RA including immunomodulatory activity. Moreover, the BuOH fraction exerted the activity of anti-RA of Impatiens pritzellii.

Interleukin-18: a novel prognostic cytokine in bacteria-induced sepsis

OBJECTIVE

Severe inflammation and sepsis remain a serious clinical challenge worldwide. Despite modern supportive medicine and an improved understanding of the underlying pathophysiology, mortality rates remain high in patients suffering from this severe inflammatory process. The often excess production of pro- and anti-inflammatory cytokines frequently found in the circulation of septic patients has stimulated the search for reliable inflammatory mediators that can be used for the diagnosis and prediction of clinical outcome. Interleukin (IL)-18, formerly termed interferon-gamma inducing factor, is a pro-inflammatory and Th1 cytokine suggested to play a significant role in the pathogenesis of this disease. This review focuses on our current understanding of the pro-inflammatory cytokine, IL-18, and its potentially unique role in sepsis.

METHODS

Bibliographic search of the most recent literature (1995-2005) relating to IL-18 and its role in inflammatory diseases, with emphasis on its pathophysiological importance in sepsis. In addition, a summary of the author's own experimental data from this particular field of research set in the context of current knowledge regarding IL-18.

RESULTS AND CONCLUSIONS

Several studies have shown elevated plasma IL-18 concentrations to be associated with poor clinical outcome in severe inflammatory and septic conditions. Moreover, a significant increase in IL-18 concentrations has been shown to discriminate between Gram-positive and Gram-negative related sepsis, and, thus, may potentially augment existing diagnostic tools. Biological neutralization of IL-18 via caspase-1 intervention or through the administration of IL-18-binding protein has been promulgated as a promising therapeutic approach, but additional studies are required to evaluate its full potential in acute inflammatory diseases.

In primary human monocyte-derived macrophages exposed to Human immunodeficiency virus type 1, does the increased intracellular growth of Leishmania infantum rely on its enhanced uptake?

Concurrent uncontrolled development of human immunodeficiency virus type 1 (HIV-1) and Leishmania spp. is regarded as an emerging pathogenic combination in countries where human beings are exposed to these two micro-organisms. The present study was aimed at exploring whether HIV-1 development within a culture of human monocyte-derived macrophages (MDMs) affected the further development of luciferase-encoding Leishmania infantum using the luciferase activity as a readout assay. It was demonstrated that, in cultures of HIV-1-loaded MDMs exposed to axenic amastigotes, the luciferase activity was higher than in HIV-1-free MDMs. As a preliminary approach to deciphering the possible mechanism through which HIV-1 can affect Leishmania infantum, attention was focused on the very early processes that could underlie this increased luciferase activity. Using GFP-labelled parasites, it was possible to establish that, in HIV-1-infected MDMs, the percentage of GFP-expressing MDMs was higher (10-20 %) than in cell cultures not exposed to HIV-1 (5 %). Two-colour immunofluorescence staining suggested that HIV-1 indirectly affects the uptake of parasites inside MDMs. Thus, the observed phenomenon seems to be linked with a higher uptake of parasites within MDMs. Taken together, the data reported here may contribute to our understanding of disseminated Leishmania infection in HIV-1-infected individuals.

Establishment and characterization of SRIK-NKL: a novel CD8+ natural killer/T cell line derived from a patient with leukemic phase of acute lymphoblastic lymphoma

The distinction between T cells and NK cells is difficult, and becoming more complex, as the diversity of the human lymphocyte repertoire is evident. We report the establishment of a permanent CD8+ NK/T cell line (SRIK-NKL) from a patient with leukemic phase of acute lymphoblastic lymphoma having characteristics of both NK and T cells, and extensively describe its phenotype, including cytotoxic activity, NK cell receptor expression, and other molecules critical for immune function. We further compare SRIK-NKL to other available NK/NK-T cell lines. SRIK-NKL may be useful for studying NK cell development, functions, and modulation, leading to novel strategies for treatment of autoimmune disease, infection, and cancer.

Immunology of Cutaneous Vasculitis Associated with both Etanercept and Infliximab

Targeted inhibition of tumour necrosis factor-alpha (TNF-alpha) is an effective therapy in rheumatoid arthritis and Crohn's disease (CD). Infliximab, a monoclonal murine-human chimeric antibody to TNF-alpha, and etanercept, a fusion protein of two p75 chains of the TNF receptor II and the Fc portion of IgG1, are generally well tolerated. Rarely does clinically significant autoimmunity, including drug-induced lupus and vasculitis occur. Immunologic mechanisms underlying the development of autoimmunity in the presence of such powerful immunosuppressants are unknown. We describe a patient with CD, who developed cutaneous vasculitis on etanercept, which worsened significantly with switch to infliximab. Investigation of the associated systemic and local immune response demonstrated the absence of human antichimera antibodies, but mRNA for T-helper 1 cytokines, chemokines and defensins in the skin and elevated angiogenesis factors in the serum, as determined by reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. Histopathology revealed a lymphocytic vasculitis composed of T cells. A permanent B-cell line (MD-B) producing extremely high amounts of chemokines and interleukin-6 was established from this patient's peripheral blood. Lesions progressed despite discontinuation of the drugs and (40 mg/day) prednisone but almost completely resolved with single dose of (0.1 mg/kg) intravenous dexamethasone, which may be therapy of choice for this reaction. A few lesions (<10) have recurred intermittently over 4 years of follow-up, suggesting possible persistence of this TNF-inhibitor-triggered autoimmune disease.

The effect of the physical characteristics of hydroxyapatite particles on human monocytes IL-18 production in vitro

Hydroxyapatite (HA) is widely used to coat the metal parts of prosthetic implants in order to improve their biocompatibility and as a bone defect filling material. HA has been demonstrated to produce particles at the prosthetic interface that lead to an activation of phagocytic cells that induce a cascade reaction leading to bone resorption and aseptic loosening. Monocytes/macrophages are commonly observed in the interface tissue, and are among the first cells to colonize the inflammatory site where they play a key role in the immune response. IL-18 is a pro-inflammatory cytokine. Monocytes/macrophages were described as IL-18 producing cells. IL-18 works antagonistically to IL-6, which activates osteoclastogenesis. In the present study, we investigated the ability of HA particles to induce the production of active IL-18 by human monocytes according to particle characteristics (size, sintering temperature and shape). Our study demonstrates, for the first time, that HA particles are capable of stimulating the production of the proinflammatory cytokine IL-18 in human monocytes according to their particle characteristics. The expression and the production of IL-18 was modified by the parameter studied. The difference observed between the expression and the production could be explain by the production of ICE. The needle shaped particles induced the larger production of IL-18.

Reduced nasal IL-10 and enhanced TNFalpha responses during rhinovirus and RSV-induced upper respiratory tract infection in atopic and non-atopic infants

Rhinovirus and respiratory syncytial virus (RSV) are the most prevalent inducers of upper respiratory tract infections (URTI) in infants and may stimulate immune maturation. To estimate the amount of immune stimulation, nasal immune responses were examined during rhinovirus and RSV‐induced URTI in infants. Nasal brush samples were taken from infants (2–26 months; 57% atopic family) with rhinovirus‐induced URTI (N = 20), with RSV‐induced URTI (N = 7), and with rhinovirus‐induced rhinitis (N = 11), from children with asymptomatic rhinovirus infection (N = 7) and from eight non‐infected children. Numbers of nasal brush cells positive for Th1‐, Th2‐, regulatory and proinflammatory cytokines were measured by immunohistochemistry or by measuring protein levels using a cytometric bead array analysis. During rhinovirus and RSV‐induced URTI, fewer regulatory cytokine IL‐10 positive cells were found compared to non‐infected children. This fall was accompanied by an increase in levels of the Th1 cytokine TNFα. IL‐10 responses were inversely related to TNFα responses. No enhanced responses were observed for IFNγ, IL‐12 and IL‐18. Cytokine responses were comparable in children with rhinovirus‐induced URTI and in children with rhinitis, while responses in asymptomatic rhinovirus‐infected children were located between those for symptomatic and asymptomatic rhinovirus‐infected children. Cytokine responses did not depend on the age of the child or atopy in the family. In conclusion, reduced nasal IL‐10 responses during URTI in infants could facilitate the induction of a TNFα response. TNFα in turn could replace the immature production of IL‐12, IL‐18 and IFNγ during URTI to induce an effective clearance of the viral infection and which could stimulate the maturation of Th1 cytokine production in infancy. J. Med. Virol. 75:348–357, 2005. © 2004 Wiley‐Liss, Inc.

Decreased interleukin-18 expression in BAL cells and peripheral blood mononuclear cells in adult cystic fibrosis patients

Lymphocytes from cystic fibrosis (CF) patients secrete less interferon-gamma (IFN-gamma) upon stimulation compared to controls. Expression of interleukin (IL)-18 as an IFN-gamma inducing factor and of IL-10 as an IL-18 inhibiting factor were determined in bronchoalveolar lavage (BAL) cells from CF patients (n=5) and from normal control subjects (n=9) as well as in peripheral blood mononuclear cells (PBMC) from patients (n=12) and from control subjects (n=9) with RT-PCR. IL-18 and IL-10 serum protein levels were measured using ELISA. BAL cells and PBMC of CF patients expressed significantly less IL-18 compared to controls (p<0.05). There was no significant difference for IL-10 in BAL cells. However, PBMC from patients expressed significantly more IL-10 mRNA (p<0.05). IL-18 serum protein levels were decreased in the patient group, whereas IL-10 serum concentrations were elevated. Stimulation with rhIL-10 reduced IL-18 expression in PBMC from CF patients. Decreased IL-18 expression in CF patients may contribute to decreased IFN-gamma production. IL-10 may contribute to inhibit IL-18 expression in PBMC in CF.

Changes of inflammation-associated cytokine expressions during early phase of experimental endotoxic shock in macaques

AIM: To study changes of inflammation-associated cytokine expressions during early phase of endotoxic shock in macague.

METHODS: Experiments were performed in Macaque mulatta treated with LPS 2.8 mg/kg in shock model group or with normal saline in control group. Blood samples were collected before, or 60 min, or 120 min after LPS injection, respectively. Liver and spleen tissues were obtained at 120 min after LPS injection. The plasma levels of TNF-α , IL-1 β , IL-10 and IL-12P40 were determined by double-antibody sandwich ELISA with antibodies against human cytokines. The mRNA levels of TNF-α , IL-1 β , and IL-18 in peripheral blood mononuclear cells (PBMCs), liver and spleen were examined by real-time fluorescence semi-quantitative RT-PCR with the primers based on human genes.

RESULTS: Mean systemic arterial pressure (MAP), systemic vascular resistance index (SVRI) and left ventricular work index (LVWI) of macaques were significant declined in shock model group on average 60 min after LPS injection. The plasma levels of TNF-α and IL-10 were significantly increased 60 min after LPS injection and then decreased. The plasma levels of IL-1 β and IL-12P40 were significantly increased at 120 min after LPS injection. The mRNA levels of TNF-α and IL-1 β were significantly increased 60 min after LPS stimulation in PBMCs and 120 min after LPS stimulation in livers. The mRNA level of IL-18 was significantly increased 120 min after LPS stimulation in PBMCs and livers. But in spleen, only TNF-α mRNA level in LPS group was significantly higher 120 min after LPS stimulation, compared with that in control group.

CONCLUSION: An endotoxic shock model of Macaque mulatta was successfully established. Both antibodies for ELISA and PCR primers based on human cytokine assays were successfully applied to detect macaque cytokines. In the model, inflammatory cytokines, such as TNF-α , IL-1 β , IL-12 and IL-18 as well as anti-inflammation cytokine IL-10, were released at very early phase of endotoxic shock within 120 min after LPS injection. PBMCs and liver cells might be the important sources of these cytokines.

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.

Single-nucleotide polymorphisms of the interleukin-18 gene promoter region in rheumatoid arthritis patients: protective effect of AA genotype

Rheumatoid arthritis (RA) is a chronic arthritic condition that can lead to deformities and disabilities. Although numerous studies reported the association of human leukocyte antigen (HLA)-DRB1*04 and RA, other genes, e.g. cytokines genes, may contribute towards disease susceptibility. Interleukin-18 (IL-18) is a proinflammatory cytokine postulated to play a role in the acute and chronic inflammatory phases of RA. The IL-18 protein expression seems to be regulated by two single-nucleotide polymorphisms (SNPs) located at positions -607 and -137 in the promoter region of the gene. It is postulated that specific alleles may be associated with susceptibility to the development of RA. In the present study, we described the IL-18 gene promoter region genotypes and combined genotypes (-607/-137) in 106 RA patients and 273 unrelated healthy controls to evaluate the contributions of these alleles to RA predisposition in Chinese, Malays, and Indians. The genotyping were performed using sequence-specific polymerase chain reactions. Rheumatoid factors were assayed by enzyme-linked immunosorbent assay. Biodata were obtained through chart review. The controls had significantly higher frequency of AA genotype at position -607 when compared to RA patients. No significant differences were observed in the distribution of either allelic or genotypic frequencies at position -137. There was no association between the genotypes and the presence of rheumatoid factors. This study did not find evidence of a genetic susceptibility factor but demonstrated the novel finding that the AA genotype at position -607 is associated with a protective effect against development of RA in Chinese individuals. This protection may be mediated through inhibition of cyclic (Adenosine 3', 5'-cyclic monophosphate) AMP-responsive element (CRE)-binding protein by the disruption of the CRE consensus sequence.

Interleukin-18 expression in BAL cells of sarcoidosis patients is decreased in vivo but protein secretion is not impaired in vitro

Recently, increased expression of interleukin-18 (IL-18) has been shown in sarcoid airway epithelium. However, IL-18 expression has not been investigated extensively in bronchoalveolar lavage (BAL) cells in sarcoidosis yet. Expression of IL-18 and tumour necrosis factor-alpha (TNFalpha) mRNA in cells of the BAL of 23 patients with sarcoidosis and nine healthy volunteers was determined using semiquantitative RT-PCR. IL-18 protein in BAL cells was investigated by immunocytochemistry (ICC). IL-18 protein levels in BAL cell culture supernatants from patients and controls with and without LPS stimulation were measured by enzyme-linked immuno-sorbent assay. BAL cells from patients were stimulated with either IL-10 or IL-13 and IL-18 protein levels were determined. IL-18 mRNA expression was significantly decreased in BAL cells of patients compared to control subjects (1.62 +/- 0.27 vs. 4.29 +/- 0.77, P < 0.05). TNFalpha mRNA expression was significantly increased in BAL cells of patients in comparison to control subjects (0.63 +/- 0.09 vs. 0.11 +/- 0.08, P < 0.05). ICC showed less positive alveolar macrophages in sarcoidosis patients than in control subjects (26 vs. 53%). IL-18 protein levels did not differ significantly between both groups. Stimulation with IL-10 significantly reduced IL-18 protein concentration in sarcoidosis patients. Our results suggest that BAL cells may not be the main source of IL-18 production in sarcoidosis in vivo. Since IL-18 production of BAL cells was not impaired in culture antiinflammatory cytokines might contribute to decreased IL-18 expression in vivo.

Serum cytokine concentrations do not parallel Mycobacterium tuberculosis-induced cytokine production in patients with tuberculosis

We measured serum cytokine concentrations and Mycobacterium tuberculosis-stimulated cytokine production by peripheral blood mononuclear cells (PBMCs) obtained from persons infected with M. tuberculosis. Serum interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) concentrations were elevated in patients with tuberculosis compared with healthy persons who had reactions to tuberculin skin tests, but IL-18 concentrations were not. In contrast, M. tuberculosis-stimulated PBMCs from patients with tuberculosis produced less IFN-gamma and IL-18 but similar amounts of IL-10, compared with PBMCs from healthy subjects who had reactions to tuberculin skin tests. Pretreatment of PBMCs from healthy subjects with reaction to tuberculin with serum from patients with tuberculosis inhibited IFN-gamma production in response to M. tuberculosis, and inhibition was blocked by anti-IL-10. Thus, serum concentrations of IFN-gamma, IL-18, and IL-10 do not parallel M. tuberculosis-induced cytokine levels, and increased IL-10 serum levels in patients with tuberculosis inhibit IFN-gamma production in response to mycobacterial antigens.

Association of single nucleotide polymorphisms in the IL-18 gene with sarcoidosis in a Japanese population

Interleukin-18 (IL-18) and interleukin-12 (IL-12) synergistically stimulate interferon-gamma (IFN-gamma) production from Th1 cells. The levels of serum IL-18 and IFN-gamma and bronchoalveolar lavage fluid IL-18 were elevated in patients with sarcoidosis. The polymorphisms of the IL-18 gene may play a possible role in expression regulation of the gene. We investigated the roles of the polymorphisms in the development of sarcoidosis. We examined two single nucleotide polymorphisms of the IL-18 gene in 119 patients with sarcoidosis and 130 healthy control subjects. Our results showed that the frequency of sarcoidosis patients with the CA genotype at position -607 was significantly higher than that with the AA genotype (OR = 2.200) and a significantly higher proportion of patients had the C allele at -607 compared with that of the controls (OR = 2.123). No significant differences were seen in the distribution of the genotypes or phenotype frequencies at position -137. There was no specific organ involvement associated with a certain genotype or phenotype. In IL-18 gene polymorphisms, the C allele at position -607 might be a genetic risk factor for sarcoidosis in this Japanese population.

Participation of contrasting changes in IL-10 and IL-12 production in the reduction of Th1-predominance by Hachimi-jio-gan in autoimmune MRL/MP-lpr/lpr mice

Hachimi-jio-gan (Chinese name: Ba-Wei-Di-Huang-Wan, HMG), a traditional Japanese herbal medicine, has been used for disorders accompanying aging. Our previous studies suggested that HMG ameliorated Thl-predominant autoimmune diseases in MRL/lpr mice through inhibition of IL-12 production. In the present study, the oral administration of HMG down-regulated phosphorylated STAT4 and up-regulated phosphorylated STAT6 in CD4 T cells. In the T cells, IL-12Rbeta1 and IL-12Rbeta2 mRNA expression levels were suppressed. In antigen-presenting cells (CD45R- MHC class II+ cells) which control Th1 and Th2 immune responses, the total cell number and the percentage of cells expressing co-stimulatory molecules decreased in the HMG-treated group. In addition, the levels of IL-12 and 18 mRNA expression increased and conversely, IL-10 mRNA expression decreased. Further, the production of IL-10 was up-regulated and that of IL-12 was down-regulated by HMG in the presence of anti-CD40 antibody. These results suggest that the opposite effects on IL-10 production and, IL-12 or IL-18 production in antigen-presenting cells of oral administration of HMG are due a decline in IL-12R expression, and consequently, amelioration of MRL/lpr autoimmune diseases occurs through the suppression of Th1 predominance via STAT4/STAT6 signaling.

Semi-quantitative analysis of multiple cytokines in canine peripheral blood mononuclear cells by [correction of zby] a single tube RT-PCR

Cytokines play an important role in the regulation of the immune system, but low circulating levels in plasma make routine measurement a difficult task. A new methodology based on single tube RT-PCR has been developed to determine the expression of multiple canine cytokines (TNF-alpha, IL-2, IFN-gamma, IL-18, IL-4, IL-6 and IL-10) using primers and protocols designed allow specific amplification of the mRNAs. The technique is performed in one tube in two consecutive steps, a specific transcription of the mRNA of a given cytokine and amplification of the corresponding gene by PCR. The technique was used to analyse the mRNA cytokine profile of peripheral blood mononuclear cells (PBMCs) from healthy dogs using two approaches: (i) analysis of PBMC isolated ex vivo; (ii) analysis of PBMC after in vitro cultures with or without the mitogen ConA. The samples were separated in agarose gels and the intensity of ethidium bromide signals quantified using standard video imaging equipment. Results were interpreted as the ratio of cytokine to GAPDH expression. The results obtained show that the method is easy to use and reproducible. Therefore, this method of monitoring the mRNA cytokine expression might be an useful tool for understanding the immune response in dogs.

Differential induction of cellular responses by live and dead Leishmania promastigotes in healthy donors

The most effective protection against human leishmaniasis has been achieved following vaccination with live promastigotes. Killed promastigotes + BCG can protect, albeit to a lower degree. To explore what mechanisms may be involved in these differences, the ability of live and dead promastigotes to induce immune responses were evaluated in vitro. The data showed that live and dead promastigotes differ in their ability to induce proliferation and cytokine production. Cytokine gene expression of Th1 related cytokines (IL-12, IFNgamma and TNFalpha) in adult PBMC was more evident to live than to heat killed promastigotes. This was coupled with significantly higher number of IFNgamma secreting cells induced by live than killed promastigotes. However, alpha-IL-12 antibodies did not block the IFNgamma response induced by live promastigotes. Proliferative responses were variable. In contrast to adult PBMC no IFNgamma secreting MNC could be detected in cord blood. However, in these cells the live promastigotes consistently induced higher proliferative response compared to dead. Implications of these findings are discussed.

T Cells Enhance Production of IL-18 by Monocytes in Response to an Intracellular Pathogen

We studied the effect of T cells on IL-18 production by human monocytes in response to Mycobacterium tuberculosis. Addition of activated T cells markedly enhanced IL-18 production by monocytes exposed to M. tuberculosis. This effect was mediated by a soluble factor and did not require cell-to-cell contact. The effect of activated T cells was mimicked by recombinant IFN-gamma and was abrogated by neutralizing Abs to IFN-gamma. IFN-gamma also enhanced the capacity of alveolar macrophages to produce IL-18 in response to M. tuberculosis, suggesting that this mechanism also operates in the lung during mycobacterial infection. IFN-gamma increased IL-18 production by increasing cleavage of pro-IL-18 to mature IL-18, as it enhanced caspase-1 activity but did not increase IL-18 mRNA expression. These findings suggest that activated T cells can contribute to the initial immune response by augmenting IL-18 production by monocytes in response to an intracellular pathogen.

Bacterially induced activation of interleukin-18 in porcine intestinal mucosa

Interleukin (IL)-18 is a cytokine with structural and functional properties similar to IL-1beta and IL-12, respectively. It is activated by caspase-1 cleavage, like IL-1beta, and induces interferon (IFN)-gamma, like IL-12. In order to study the role of IL-18 in the immune response to infectious diseases of mucosal surfaces we cloned and expressed porcine IL-18 and developed antibodies to the protein. Porcine IL-18 retains the caspase-1 cleavage site present in other mammalian IL-18 proteins, but has two potential N-linked glycosylation sites not found in those proteins. Porcine interleukin-18 mRNA and protein are expressed in immune tissues including lymph nodes and gut associated lymphoid tissues. Specific cell types containing IL-18 include lung and splenic macrophages, nonadherent spleen cells and intestinal epithelial cells. Although IL-18 transcription is moderately induced by lipopolysaccharide, the magnitude and total expression level are small compared to those of interleukin-1beta. In vivo and ex vivo infection of intestinal mucosa with Salmonella choleraesuis resulted in a decrease in size of IL-18, consistent with cleavage of the preprotein by caspase-1. Thus, IL-18 is present in mucosal tissues where it could play a role in the immune response to invading pathogens.

Cloning and mutation analysis of the human IL-18 promoter: a possible role of polymorphisms in expression regulation

Interleukin-18 is a proinflammatory cytokine, which strongly induces IFN-gamma production. We have cloned the human IL-18 promoter and screened for possible polymorphisms. Three single nucleotide polymorphisms were detected in the promoter and two polymorphisms in the 5'-nontranslated region of the gene. Three combinations of these polymorphisms were observed in the Swedish population. All IL-18 promoter alleles were found to have clear promoter activity when inserted into a luciferase reporter vector. There were no significant differences in promoter activity between alleles without stimulation, but after stimulation with PMA/ionomicin one of the alleles had clearly lower activity than the other (P<0.01). Measurement of IL-18 and IFN-gamma production in 48 multiple sclerosis patients by RT-PCR showed slightly higher expression of IL-18 in individuals homozygous for the most frequent haplotype. Two IL-18 promoter polymorphisms were analyzed by sequence specific PCR in 208 multiple sclerosis patients and 139 healthy controls, however, no significant differences were found. In summary, our data indicate that common IL-18 promoter polymorphisms influence the expression of IL-18 and potentially also of IFN-gamma.

Lipopolysaccharide/endotoxin induces IL-18 via CD14 in human peripheral blood mononuclear cells in vitro

IL-18 shares activities with IL-12 in generating T-helper 1 cells and cytokine response. It mediates LPS/endotoxin lethality by IL-12 independent interferon-gamma synthesis and it induces bacteria-related organ failure. As peripheral blood mononuclear cells (PBMC) are potent producers of IL-18, we studied the regulation of IL-18 upon exposure to LPS and Staphylococcus aureus (SAC) in vitro. Freshly isolated PBMC constitutively expressed IL-18 mRNA. After unstimulated preincubation for 48 h, however, IL-18 transcripts were nearly not detectable by RT-PCR, but inducible by LPS or SAC (P<0.01). Both LPS and SAC were potent stimuli of IL-18 protein secretion (P<0.01). LPS-mediated IL-18 gene expression and secretion was CD14-dependent and significantly inhibited by co-incubation of PBMC with neutralizing CD14 antibody (P<0.01). We conclude that LPS-driven IL-18 is dependent on the expression of costimulatory factors and that IL-18 inhibition might attenuate IL-18-related toxic effects.

Increased levels of serum interleukin-18 in Graves' disease

We have previously reported that serum soluble interleukin-2 receptor (sIL-2R) and IL-12 levels were significantly increased in hyperthyroid Graves' disease. In this study, we investigated serum IL-18 levels in patients with either Graves' disease or Hashimoto's thyroiditis. The serum IL-18 levels in Graves' disease were significantly increased in the hyperthyroid state and were decreased during treatment with methimazole or propylthiouracil. On the other hand, the levels in Hashimoto's thyroiditis in the hypothyroid state showed no significant differences from those in healthy subjects. When liothyronine sodium was administered orally to healthy subjects, serum IL-18 levels were not changed. Positive correlations between serum IL-18 and IL-12, IL-12 and sIL-2R, and sIL-2R and IL-18 levels were noted in Graves' disease. These results suggest that Th1 cytokines might play an important regulatory role in Graves' disease.

Expression of interleukin-18 in the lung after endotoxemia or hemorrhage-induced acute lung injury

Hemorrhage and endotoxemia are important risk factors for the development of acute lung injury. Interleukin (IL)-18 is a recently described cytokine released in its mature, active form after pro-IL-18 is cleaved by the IL-1 converting enzyme (ICE). IL-18 has multiple immunomodulating properties, including induction of interferon-gamma (IFN-gamma), IL-1beta, tumor necrosis factor-alpha, and intercellular adhesion molecule-1. To examine the possible involvement of IL-18 in acute lung injury, we examined its expression, as well as that of IFN-gamma, IL-12, and ICE, using murine hemorrhage or endotoxemia models. The amounts of IL-18 messenger RNA (mRNA) increased in the lung after hemorrhage or endotoxemia. However, only endotoxemia was associated with elevations in lung and plasma concentrations of IL-18 protein. ICE expression was increased in the lungs after endotoxemia but not after hemorrhage. Although IFN-gamma expression increased in the lungs after hemorrhage or endotoxemia, elevations in lung IL-12 mRNA levels were found only after endotoxemia. These results indicate that hemorrhage and endotoxemia induce different patterns of immunomodulatory cytokine expression in the lungs. In particular, differences in the expression of ICE after hemorrhage or endotoxemia may affect generation of the active forms of downstream cytokines, including IL-18. IFN-gamma expression in the lungs after hemorrhage appears to occur through a pathway independent of IL-12 and IL-18. IL-18 may play a role in modulating the development of acute lung injury after endotoxemia but not after hemorrhage.

HIV-1 alters T helper cytokines, interleukin-12 and interleukin-18 responses to the protozoan parasite Leishmania donovani

OBJECTIVE

To investigate the in vitro and in vivo effect of HIV-1 on lymphoproliferative and T helper (Th) cytokine responses in leishmaniasis.

METHODS

Th1 [interleukin (IL)-2 and interferon (IFN)-gamma] and Th2 (IL-4 and IL-10) as well as IFN-gamma-inducing cytokines (IL-12 and IL-18) were measured in antigen and mitogen-stimulated culture supernatants of peripheral blood mononuclear cells (PBMC) of healthy donors, HIV-infected and visceral leishmaniasis (VL) patients with or without HIV co-infection.

RESULTS

Proliferative responses to phytohaemagglutinin (PHA) were significantly lower in PBMC from VL and asymptomatic HIV-infected persons compared with responses in healthy individuals. VL-HIV co-infected patients showed the lowest responses. Although there was no significant difference in the Leishmania-induced proliferative responses among the healthy group and those infected with HIV only, VL patients (with or without HIV) exhibited very low proliferation. When cultured with PHA or Leishmania, PBMC from healthy donors produced high levels of a Th1 cytokine (IFN-gamma) and low levels of Th2 cytokines (IL-4 and IL-10). In addition, co-culturing PBMC from healthy donors with a killed HIV preparation abrogated the production of IFN-gamma induced by Leishmania and augmented IL-4 and IL-10 production. Cells from HIV-infected patients produced low levels of IFN-gamma, but high levels of IL-10. The addition of anti-IL-10 did not increase Leishmania-induced proliferative responses or IFN-gamma production. Both IL-12 and/or IL-18 responses were lower in VL patients, HIV-infected, or VL-HIV co-infected patients as compared with those of healthy donors.

CONCLUSION

The data suggest that the inhibitory effect of HIV and VL on proliferation and IFN-gamma production is not due to IL-10 alone, but that the defect induced by HIV and VL probably operates at the level of regulation of IFN-gamma-inducing factors, such as IL-12 and IL-18.