Increased levels of interleukin-18 in patients with pulmonary sarcoidosis

Increased serum interferon activity in sarcoidosis compared to that in tuberculosis: Implication for diagnosis?

Objectives

In this study, we measured serum interferon (IFN) levels and activity in patients with sarcoidosis and tuberculosis (TB) with and without uveitis. We aimed to understand the role of IFN in the pathophysiology of both conditions and explore its potential as a discriminating marker for these clinically similar diseases.

Methods

Sera from an Indonesian TB and a Dutch sarcoidosis cohort were used in the analysis. IFNα2 and IFNγ concentrations were measured using Simoa® and Luminex assays, respectively. Serum IFN activity was assessed by incubating THP-1 cells with patient serum and measuring IFN-stimulated gene transcription using qPCR. Anti-IFNα2 and IFNγ autoantibodies were detected via Luminex assay and tested for neutralizing capacity using a flow cytometry-based signal transducer and activator of transcription (STAT) 1 phosphorylation inhibition assay.

Results

IFNα2 was detected in 74 % and 64 % of patients with sarcoidosis and pulmonary TB, respectively, while IFNγ was found in 78 % and 23 % of patients with sarcoidosis and TB, respectively. For uveitis cases specifically, IFNα2 was detected in 85 % of sarcoid uveitis (SU) and 33 % of tubercular uveitis (TBU) cases. Similarly, IFNγ was detected in 69 % of SU and 17 % of TBU cases. IFNγ serum concentrations were higher in sarcoidosis than that in TB patients (p < 0.0001). Focusing on patients with uveitis, SU showed increased IFNα2 (p = 0.004) and IFNγ (p < 0.002) serum concentrations compared to that in TBU. Notably, TBU displayed significantly reduced IFNα2 concentrations compared to that in healthy controls (p = 0.006). These results align with the increased interferon stimulated gene (ISG) transcriptional upregulation observed in THP-1 cells stimulated with serum from patients with sarcoidosis. Elevated levels of non-neutralizing anti-IFN autoantibodies were observed in patients with TB; however, these levels were similar to those observed in geographically matched healthy Indonesian controls.

Conclusion

Our results suggest decreased serum levels and activity of type I and II IFN in TB compared to those in sarcoidosis. This is indicative of distinct pathophysiological processes in these highly clinically similar diseases. We propose that the assessment of serum IFN levels and IFN activity has the potential to distinguish between sarcoidosis/SU and TB/TBU.

FOXP3+ regulatory T cells are associated with the severity and prognosis of sarcoidosis

Rationale

Sarcoidosis is an inflammatory granulomatous disease of unknown etiology with predominant lung involvement. Organ involvement and disease severity, as well as the nature of immune alterations, vary among patients leading to a range of clinical phenotypes and outcomes. Our objective was to evaluate the association of disease course and immune responses in pulmonary sarcoidosis.

Methods

In this prospective cohort study of 30 subjects, most of whom were followed for one year, we evaluated 14 inflammatory markers in plasma, 13 Treg/T cell flow cytometry markers and 8 parameters of FOXP3+ Treg biology, including suppressive function, epigenetic features and stability.

Results

We identified a set of 13 immunological parameters that differ in sarcoidosis subjects in comparison with healthy donors. Five of those were inversely correlated with suppressive function of Tregs in sarcoidosis, and six (TNFα, TNFR I and II, sCD25, Ki-67 and number of Tregs) were particularly upregulated or increased in subjects with thoracic lymphadenopathy. Treg suppressive function was significantly lower in patients with thoracic lymphadenopathy, and in patients with higher burdens of pulmonary and systemic symptoms. A combination of five inflammatory markers, Ki-67 expression, Treg function, and lung diffusion capacity evaluated at study entry predicted need for therapy at one year follow-up in 90% of cases.

Conclusion

Tregs may suppress ongoing inflammation at local and systemic levels, and TNFα, TNFR I and II, sCD25 and Ki-67 emerge as attractive biomarkers for in vivo sarcoid inflammatory activity.

Biologic and advanced immunomodulating therapeutic options for sarcoidosis: a clinical update

Introduction: Sarcoidosis is a multi-organ disease with a wide range of clinical manifestations and outcomes. A quarter of sarcoidosis patients require long-term treatment for chronic disease. In this group, corticosteroids and cytotoxic agents be insufficient to control diseaseAreas covered: Several biologic agents have been studied for treatment of chronic pulmonary and extra-pulmonary disease. A review of the available literature was performed searching PubMed and an expert opinion regarding specific therapy was developed.Expert opinion: These agents have the potential of treating patients who have progressive disease. Many of these agents have different mechanisms of action, response rates, and toxicity profiles.

Models Contribution to the Understanding of Sarcoidosis Pathogenesis: "Are There Good Models of Sarcoidosis?"

Sarcoidosis is a systemic, granulomatous, and noninfectious disease of unknown etiology. The clinical heterogeneity of the disease (targeted tissue(s), course of the disease, and therapy response) supports the idea that a multiplicity of trigger antigens may be involved. The pathogenesis of sarcoidosis is not yet completely understood, although in recent years, considerable efforts were put to develop novel experimental research models of sarcoidosis. In particular, sarcoidosis patient cells were used within in vitro 3D models to study their characteristics compared to control patients. Likewise, a series of transgenic mouse models were developed to highlight the role of particular signaling pathways in granuloma formation and persistence. The purpose of this review is to put in perspective the contributions of the most recent models in the understanding of sarcoidosis.

Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins

We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.

Cytokines of the IL-1 family: recognized targets in chronic inflammation underrated in organ transplantations

Interleukin 1 (IL-1) family is a group of cytokines with multiple local and systemic effects, which regulates both innate and adaptive immune responses. Generally, most IL-1 family cytokines express prevailing pro-inflammatory activities (IL-1α, IL-1β, IL-18, IL-33, IL-36 α, β, γ), whereas others are anti-inflammatory (IL-1Ra (IL-1 receptor antagonist), IL-36Ra, IL-38, IL-37). In addition to their immunomodulatory roles, some of them are also involved in the physiological modulation of homeostatic processes and directly affect mRNA transcription. IL-1 family cytokines bind to specific receptors composed of a ligand-binding chain and an accessory chain. The pro-inflammatory effects of IL-1 family cytokines are regulated on the level of transcription, enzymatic processing of precursors, release of soluble antagonists, and expression of decoy receptors. Members of the IL-1 family regulate the recruitment and activation of effector cells involved in innate and adaptive immunity, but they are also involved in the pathogenesis of chronic disorders, including inflammatory bowel disease, rheumatoid arthritis, and various autoimmune and autoinflammatory diseases. There are only limited data regarding the role of IL-1 cytokines in transplantation. In recent years, targeted therapeutics affecting IL-1 have been used in multiple clinical studies. In addition to the recombinant IL-1Ra, anakinra (highly effective in autoinflammatory diseases and tested for other chronic diseases), the monoclonal antibodies canakinumab, gevokizumab, and rilonacept (a long-acting IL-1 receptor fusion protein) provide further options to block IL-1 activity. Furthermore, new inhibitors of IL-18 (GSK 1070806, ABT-325, rIL-18BP (IL-18 binding protein)) and IL-33 (CNTO-7160) are presently under clinical studies and other molecules are being developed to target IL-1 family cytokines.

Sarcoidosis in celiac disease: A page written by genetic variants in IL-18 miRNAs target site?

Sarcoidosis is a chronic idiopathic granulomatous disease. Interleukin-18 (IL-18) has been strongly implicated in the pathogenesis of sarcoidosis. Sarcoidosis shows characteristic microRNAs (miRNAs) profiles. MiRNAs have recently emerged as a new class of modulators of gene expression. MiRNAs are involved in susceptibility to a number of autoimmune diseases promoting and inhibiting the gene expression of different Th1 pro-inflammatory cytokines including IL18. Sarcoidosis has been connected with a variety of autoimmune disorders including celiac disease (CD). CD is a chronic, immune-mediated condition of the small intestine caused by permanent intolerance to dietary gluten. IL-18 has been reported to play an important role in inducing and maintaining inflammation after gluten exposure. MiRNAs expression is significantly altered in CD patients. We hypothesize that sarcoidosis and CD may be the result of common genetic variants in IL-18 miRNA target site.

Immunogenetics of Disease-Causing Inflammation in Sarcoidosis

Sarcoidosis is a systemic inflammatory disorder characterised by tissue infiltration by mononuclear phagocytes and lymphocytes with associated non-caseating granuloma formation. Originally described as a disorder of the skin, sarcoidosis can involve any organ with wide-ranging clinical manifestations and disease course. Recent studies have provided new insights into the mechanisms involved in disease pathobiology, and we now know that sarcoidosis has a clear genetic basis largely involving human leukocyte antigen (HLA) genes. In contrast to Mendelian-monogenic disorders--which are generally due to specific and relatively rare mutations often leading to a single amino acid change in an encoded protein--sarcoidosis results from genetic variations relatively common in the general population and involving multiple genes, each contributing an effect of varying magnitude. However, an individual may have the necessary genetic profile and yet the disease will not develop unless an environmental or infectious factor is encountered. Genetics appears also to contribute to the huge variability in clinical phenotype and disease behaviour. Moreover, it has been established that sarcoidosis granulomatous inflammation is a highly polarized T helper 1 immune response that starts with an antigenic stimulus followed by T cell activation via a classic HLA class II-mediated pathway. A complex network of lymphocytes, macrophages, and cytokines is pivotal in the orchestration and evolution of the granulomatous process. Despite these advances, the aetiology of sarcoidosis remains elusive and its pathogenesis incompletely understood. As such, there is an urgent need for a better understanding of disease pathogenesis, which hopefully will translate into the development of truly effective therapies.

The relationship between interleukin-18 polymorphisms and allergic disease: a meta-analysis

Recent studies have suggested that IL-18 −607C/A and −137G/C polymorphisms may be associated with the risk of allergic disease; however, individually published results are inconclusive. Therefore, we performed a meta-analysis to clarify whether IL-18 −607C/A and −137G/C polymorphisms were associated with the risk of allergic disease. A total of 21 studies including 5,331 cases and 9,658 controls were involved in this meta-analysis. In the overall analysis and the subgroup analysis according to ethnicity, we did not find significant association between IL-18 −607C/A or −137G/C polymorphism and the risk of allergic disease (all P > 0.05). However, in a stratified analysis by type of allergic disease, our results indicated that IL-18 −607C/A polymorphism was associated with a significantly decreased risk of allergic asthma in heterozygous comparison and IL-18 −137G/C was associated with a significantly decreased risk of allergic dermatitis in recessive model and homozygous comparison. In the stratified analysis by source of control, IL-18−607C/A showed significantly reduced risk in population-based subgroup, and for IL-18 −137G/C only significantly decreased risk was found in the hospital-based subgroup. Our meta-analysis suggests that IL-18 −607C/A and −137G/C polymorphisms may be protective factors for the risk of allergic asthma and allergic dermatitis, respectively.

Cytokine networking of innate immunity cells: a potential target of therapy

Innate immune cells, particularly macrophages and epithelial cells, play a key role in multiple layers of immune responses. Alarmins and pro-inflammatory cytokines from the IL (interleukin)-1 and TNF (tumour necrosis factor) families initiate the cascade of events by inducing chemokine release from bystander cells and by the up-regulation of adhesion molecules required for transendothelial trafficking of immune cells. Furthermore, innate cytokines produced by dendritic cells, macrophages, epithelial cells and innate lymphoid cells seem to play a critical role in polarization of helper T-cell cytokine profiles into specific subsets of Th1/Th2/Th17 effector cells or regulatory T-cells. Lastly, the innate immune system down-regulates effector mechanisms and restores homoeostasis in injured tissue via cytokines from the IL-10 and TGF (transforming growth factor) families mainly released from macrophages, preferentially the M2 subset, which have a capacity to induce regulatory T-cells, inhibit the production of pro-inflammatory cytokines and induce healing of the tissue by regulating extracellular matrix protein deposition and angiogenesis. Cytokines produced by innate immune cells represent an attractive target for therapeutic intervention, and multiple molecules are currently being tested clinically in patients with inflammatory bowel disease, rheumatoid arthritis, systemic diseases, autoinflammatory syndromes, fibrosing processes or malignancies. In addition to the already widely used blockers of TNFα and the tested inhibitors of IL-1 and IL-6, multiple therapeutic molecules are currently in clinical trials targeting TNF-related molecules [APRIL (a proliferation-inducing ligand) and BAFF (B-cell-activating factor belonging to the TNF family)], chemokine receptors, IL-17, TGFβ and other cytokines.

Mollaret meningitis may be caused by reactivation of latent cerebral toxoplasmosis

Mollaret meningitis (MM) occurs mainly in females and is characterized by recurrent episodes of headache, transient neurological abnormalities, and the cerebrospinal fluid containing mononuclear cells. HSV-2 was usually identified as the causative agent. Recently, we found that recurrent headaches in non-HIV-infected subjects were due to acquired cerebral toxoplasmosis (CT). The aim of the study was therefore to focus on molecular pathomechanisms that may lead to reactivation of latent CT and manifest as MM. Literature data cited in this work were selected to illustrate that various factors may affect latent CNS Toxoplasma gondii infection/inflammation intensity and/or host defense mechanisms, i.e., the production of NO, cytokines, tryptophan degradation by indoleamine 2,3-dioxygenase, mechanisms mediated by an IFN-gamma responsive gene family, limiting the availability of intracellular iron to T. gondii, and production of reactive oxygen/nitrogen species, finally inducing choroid plexitis and/or vasculitis. Examples of triggers revealing MM and accompanying disturbances of IFN-gamma-mediated immune responses that control HSV-2 and T. gondii include: female predominance (female mice are more susceptible to T. gondii infection than males); HSV-2 infection (increased IFN-gamma, IL-12); metaraminol (increased plasma catecholamine levels, changes in cytokine expression favoring T(H)2 cells responses); probably cholesterol contained in debris from ruptured epidermoid cysts (decreased NO; increased TNF-alpha, IL-6, IL-8). These irregularities induced by the triggers may be responsible for reactivation of latent CT and development of MM. Thus, subjects with MM should have test(s) for T. gondii infection performed obligatorily.

Allergic sensitisation in tuberculosis patients at the time of diagnosis and following chemotherapy

Background

It is still a matter of debate whether there is an association between infection with Mycobacterium tuberculosis (M. tuberculosis) and allergy. Previously, we have shown higher levels of specific IgE to different inhalant allergens and total IgE in tuberculosis (TB) patients compared to controls. The objectives of this study were to evaluate a possible change in allergic sensitisation after successful TB treatment and to confirm the finding of our previous study of enhanced allergic sensitisation in TB patients compared to controls in a more controlled setting. Additionally, we wanted to determine the cytokine profile in the same groups and finally to evaluate the association between the presence of Bacillus Calmette-Guérin vaccination (BCG) scar and allergic sensitisation among the controls.

Methods

Sera were analysed for specific IgE to inhalant allergens (Phadiatop) and total IgE by the use of ImmunoCAP 1000 (Pharmacia Diagnostics). Thirteen different cytokines were also analysed in the sera by multiplex bead immunoassay (Luminex 100, Luminex Corporation), and clinical symptoms of allergy and BCG scar were reported in a questionnaire.

Results

A reduction in levels of specific and total IgE were observed after successful TB treatment. TB patients also had higher levels of specific and total IgE compared to healthy controls. Both interleukin (IL)-6 and interferon (IFN)γ were higher in TB patients compared to healthy controls. The levels of IL-6 were reduced after successful TB treatment. The presence of a BCG scar was associated with a reduced risk of developing allergic sensitisation.

Conclusion

We observed a reduced level of allergic sensitisation after successful TB treatment. TB patients seem to be more allergically sensitised than healthy controls, confirming our previous finding. Furthermore, we observed an inverse association between allergic sensitisation and visible BCG scar, which adds additional support to the hygiene hypothesis.

Enhanced expression of type 1 helper T-cell cytokines in the myocardium of active cardiac sarcoidosis

BACKGROUND

Various cytokines are involved in the pathogenesis of sarcoidosis, but their expression in the myocardium has not been documented for cardiac sarcoidosis.

METHODS AND RESULTS

Myocardial tissue was obtained from 12 patients with cardiac sarcoidosis at the time of left ventriculoplasty, biopsy or autopsy. mRNA expression of various inflammatory cytokines was analyzed using quantitative real-time polymerase chain reaction, as well as by immunohistochemistry. Ten patients with dilated cardiomyopathy (DCM) served as controls. Enhanced expression of interleukin (IL)-1alpha, IL-2, IL-12 p40 and interferon (IFN)-gamma mRNA was limited to the myocardium of cardiac sarcoidosis patients. Expression of IL-1beta, IL-8, IL-10, IL-15 and TNF-alpha occurred in both cardiac sarcoidosis and DCM patients, but IL-4 and IL-5 were not detected in either disease. Immunohistochemistry of the myocardial tissue of sarcoidosis revealed positive staining for IL-12 and IFN-gamma. IL-12 was localized in multinucleated giant cells and macrophages of the sarcoid granulomas, whereas IFN-gamma was detected in lymphocytes and vascular endothelial cells.

CONCLUSIONS

Type 1 helper T-cell cytokines may be involved in the pathogenesis of cardiac sarcoidosis.

Association of interleukin-18 gene polymorphism with asthma in Chinese patients

Like other allergic diseases, asthma results from multiple conditions. Asthmatic beginning and severity are mediated by both environmental and genetic factors. In asthma studies, important work is realization of the genetic background and identification of genetic factors resulting in asthma development and phenomena. Here, we investigated whether interleukin (IL)-18 single nucleotide polymorphisms (SNPs) are involved in Chinese asthma patients. IL-18 (IL-18) SNP was detected by polymerase chain reaction (PCR)-based restriction analysis in 201 patients with asthma and 60 normal controls. Significant differences were found in the genotype distribution of IL-18 SNP between asthma patients and controls (P=0.000003). Allelic frequency of the IL-18 gene distinguished asthma patients from controls (P=0.000066). The results revealed a significant difference between asthma patients and normal controls in IL-18 SNP and a statistical correlation between IL-18 polymorphisms (105A/C) and asthma formation. We concluded that Chinese who carry the C/C homozygote of the IL-18-105A/C gene polymorphism in coding regions may have a higher risk of developing asthma.

Circulating levels of both Th1 and Th2 chemokines are elevated in patients with sarcoidosis

BACKGROUND

In sarcoidosis, the T helper type 1 (Th1) response tends to predominate at affected disease sites; however, whether Th1/Th2 polarization occurs in the peripheral circulation is unknown.

METHODS

Fifty-two patients with sarcoidosis and 21 healthy volunteers were investigated. The concentrations of interferon-inducible protein 10 (IP-10)/CXCL10 and thymus- and activation-regulated chemokine (TARC)/CCL17 in the serum, bronchoalveolar lavage fluid (BALF) and culture supernatant were measured by an enzyme-linked immunosorbent assay. The circulating CXCR3+ CD4+ T cells and CCR4+ CD4+ T cells were assessed by flow cytometry.

RESULTS

The CXCR3- or CCR4-positive ratios among CD4+ T cells were both higher in sarcoidosis than in healthy volunteers. The serum levels of both IP-10 and TARC of the patients with sarcoidosis were significantly higher than those of the healthy volunteers. In patients with sarcoidosis, a larger amount of IP-10 was generated by the BALF cells, whereas IP-10 production by peripheral blood mononuclear cells did not increase in comparison to the control subjects. The TARC levels produced by peripheral blood mononuclear cells of sarcoidosis patients were significantly higher than those of the controls, while no difference existed between the 2 groups regarding TARC production by BALF cells.

CONCLUSION

IP-10 is mainly produced at the lung and TARC in the peripheral circulation in sarcoidosis patients. Both IP-10 and TARC cooperatively play a role in the pathogenesis of sarcoidosis.

CXCL9 and 11 in patients with pulmonary sarcoidosis: a role of alveolar macrophages

Interferon-inducible protein-10 (IP-10)/CXCL10, which is a ligand for CXC chemokine receptor 3 (CXCR3), is known to be involved in the pathogenesis of pulmonary sarcoidosis. However, the roles of monokine induced by interferon gamma (Mig)/CXCL9 and interferon-inducible T cell alpha chemoattractant (I-TAC)/CXCL11, which are also CXCR3 ligands, remain unclear. Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 in both bronchoalveolar lavage fluid (BALF) and serum in patients with pulmonary sarcoidosis were measured by enzyme-linked immunosorbent assay (ELISA). The expression of these chemokines in alveolar macrophages was examined using ELISA, quantitative real-time polymerase chain reaction and immunostaining. In BALF, Mig/CXCL9 and IP-10/CXCL10 were significantly elevated in stage II sarcoidosis as compared with the levels in healthy volunteers. In serum, Mig/CXCL9 and I-TAC/CXCL11 were increased in stage II of the disease. The levels of all CXCR3 ligands in BALF were correlated with the numbers of both total and CD4(+) lymphocytes. Alveolar macrophages were stained positive for all CXCR3 ligands and produced increased amounts of these chemokines. Positive staining of the three chemokines was also observed in the epithelioid and giant cells in the sarcoid lungs. These findings suggest that Mig/CXCL9 and I-TAC/CXCL11 as well as IP-10/CXCL10 play important roles in the accumulation of Th1 lymphocytes in sarcoid lungs.

Genetics of sarcoidosis: candidate genes and genome scans

Human leukocyte antigen class II allele associations and T-cell receptor beta chain bias in sarcoidosis suggest a specific disease-triggering antigen exposure in a genetically susceptible host. The cause of sarcoidosis has been elusive, but genetics provides one of the few promising avenues to further our understanding. We review the association studies and genome scans used to identify the genes involved in sarcoidosis.

The clinical significance of interleukin 18 assessment in sarcoidosis patients

INTRODUCTION

Sarcoidosis is a multisystemic disease of unknown etiology characterized by the formation of immune granulomas in involved organs. The cytokine profile in inflamed lesions of sarcoidosis is mainly determined by T helper 1 (Th1) cells. Interleukin 18 (IL-18) is primarily a monocyte/macrophage-derived cytokine. IL-18 has been recently identified as an IFNgamma-inducing factor. The cytokine plays an important role in the induction of Th1 response and it may be responsible for sarcoidosis progression. The aim of the study was to assess the usefulness of IL-18 estimation in the sarcoidosis diagnosis and the disease course prognosis.

MATERIAL AND METHODS

The diagnosis of sarcoidosis was established in 88 patients (the mean age of 38.1+/-10.8 years). We measured IL-18 level in plasma and bronchoalveolar lavage fluid (BALF) cell culture supernatant (CCS) using the enzyme-linked immunoassay technique (ELISA). We also performed the flow cytometric analysis of BALF lymphocyte phenotype. Statistica 5.0 and non-parametric tests: the Mann-Whitney U-test and the Spearman correlation test, were used for statistical analysis.

RESULTS

The patient group consisted of 55 subjects without acute symptoms of sarcoidosis, 14 patients with acute Löfgren syndrome and 19 subjects with Löfgren syndrome in the past. Lung hilar lymphadenopathy was diagnosed in 49 patients and lung interstitial changes in 39 subjects. After 6-month-observation, 49 patients were in remission, 20 subjects manifested persistent disease and 19 patients had sarcoidosis progression. Plasma IL-18 level was significantly (P<0.0001) higher in sarcoidosis patients (383+/-250pg/ml) than in control subjects (146+/-72pg/ml). Plasma IL-18 level was similar both in subjects with Löfgren syndrome and in other patients. However, IL-18 level in BALF CCS was significantly (P<0.05) lower in Löfgren syndrome patients than in subjects without acute manifestation of the disease. The highest IL-18 level in plasma was found in patients with disease progression, in subjects with lung interstitial changes and in patients with extrapulmonary manifestation of the disease. We observed a positive correlation between plasma IL-18 level and the percentage of BALF lymphocytes (R=0.202, P=0.06) as well as the percentage of activated HLA DR+T cells (R=0.23, P<0.05). There was a negative correlation between the IL-18 level in BALF CCS and the percentage of BALF CD3-positive and CD4-positive lymphocytes (R=-0.27, -0.23, P<0.05).

CONCLUSION

IL-18 may play a significant role in the prolongation of sarcoidosis course. Its estimation may become a good prognostic factor, which should be analyzed together with other factors useful in sarcoidosis monitoring.

Upregulation of Th1 cytokine profile (IL-12, IL-18) in bronchoalveolar lavage fluid in patients with pulmonary sarcoidosis

Sarcoidosis, a systemic granulomatous disease of unknown etiology, is characterized by a predominantly Th1 cytokine milieu, which is involved in its immunopathogenesis. The role of novel immunologic markers reflecting T cell activity of the sarcoid immunologic response needs to be determined. The present study aims to evaluate the role of the Th1 cytokine pattern by estimating the local and systemic levels of interleukin-12 (IL-12) and IL-18 in bronchoalveolar lavage fluid (BALF), induced sputum, and serum of patients with pulmonary sarcoidosis. We studied prospectively 20 patients (12 women, 8 men) of median age 46 years (range 25-65) with sarcoidosis and 10 normal subjects (5 women, 5 men) of median age 39 years (range 26-60). IL-12 and IL-18 levels were measured using ELISA kits. The IL-12 BALF levels were significantly higher in sarcoidosis patients than in healthy subjects (5.64 +/- 0.21 pg/mL vs. 5.16 +/- 0.15 pg/mL, p < 0.001). In addition, IL-18 levels were significantly increased in BALF samples (47.69 +/- 6.29 pg/mL vs. 16.73 +/- 3.00 pg/mL, p < 0.001). A statistically significant decrease in IL-12 serum levels was detected in the sarcoid population compared with controls (5.77 +/- 0.50 pg/mL vs. 7.87 +/- 2.00 pg/mL, p < 0.001). No significant differences were detected in IL-12 and IL-18 levels between patients and controls in induced sputum samples. Our data suggest a potential role of IL-12 and IL-18 in the local immunologic response in pulmonary sarcoidosis. Further large-scale studies are needed to define the precise role of IL-12 and IL-18 in the immunopathogenesis of this disorder.

Interleukin-18 expression by alveolar epithelial cells type II in tuberculosis and sarcoidosis

The aims of the present study were to characterize the localization of interleukin-18 (IL-18) expression in lung tissue specimens from patients with pulmonary tuberculosis, sarcoidosis and controls, and to determine whether human alveolar epithelial cells type II (AEC-II) are able to generate IL-18 in primary culture. IL-18 was determined using semiquantitative reverse-transcription-PCR and localized in lungs using in situ hybridization. IL-18 protein levels were determined using the enzyme-linked immunosorbent assay and western blot analysis. Alveolar epithelial cells type II (AEC-II) were stimulated in vitro by proinflammatory cytokines, lipopolysaccharides, and whole cell lysate from Mycobacterium tuberculosis. IL-18 mRNA expression was significantly increased in the lungs affected by tuberculosis and sarcoidosis. In situ hybridization revealed different sites of expression in tuberculosis and sarcoidosis lungs, with AEC-II as one major source of IL-18 in the alveolar compartment. Basal IL-18 expression could be detected in normal AEC-II. Whole cell lysate from M. tuberculosis, but not lipopolysaccharide, led to a strong increase of IL-18 mRNA accumulation in AEC-II. Resting AEC-II secreted only small amounts of IL-18, but intracellular IL-18 protein levels increased in a time-dependent manner during culture. Proinflammatory cytokines tumour necrosis factor-alpha, IL-1beta, and interferon-gamma altered IL-18 mRNA expression and mature protein secretion of human AEC-II. These findings indicate a possible role for AEC-II and AEC-II-derived IL-18 in pathomechanisms of granulomatous lung diseases.

Endotoxin Up-regulates Interleukin-18

RATIONALE AND OBJECTIVES

Sarcoidosis is a granulomatous disease of unknown etiology characterized by a helper T-cell type 1-mediated process. Previously we demonstrated a role for interleukin-18 in sarcoidosis. Here we examine the regulation of interleukin-18 in this condition.

METHODS

Cytokine levels in sarcoid epithelial lining fluid were measured by ELISA. We examined interleukin-18 promoter activity and mRNA and protein levels in the epithelial lining fluid of individuals with active sarcoidosis, and of individuals recovered from sarcoidosis, in response to purified protein derivative of Mycobacterium tuberculosis, beryllium sulfate, zirconium sulfate, aluminum sulfate, and lipopolysaccharide. Endotoxin levels in the epithelial lining fluid of individuals with sarcoidosis, individuals recovered from sarcoidosis, and control subjects were assessed by Limulus amebocyte lysate analysis. Allele-specific polymerase chain reaction was used to genotype 94 patients with sarcoidosis and 97 control subjects for the interleukin-18 -607(A/C) polymorphism. Species-specific polymerase chain reaction identified bacterial DNA in fluid samples.

RESULTS

Epithelial lining fluid from active sarcoids contained elevated levels of interleukin-18, interferon-gamma, and interleukin-12 compared with recovered patients and also contained significantly higher levels of endotoxin. Depletion of endotoxin from this epithelial lining fluid reduced its effect on the human interleukin-18 promoter in vitro. There was a higher frequency of the -607C allele and -607(C/C) genotype in the sarcoidosis population compared with control subjects; however, this was not associated with a functional response to endotoxin treatment. Finally, bacterial 16S rRNA from Haemophilus influenzae and Moraxella catarrhalis was detected in sarcoid fluid samples.

CONCLUSIONS

The pathogenesis of sarcoidosis is propagated through the actions of a helper T-cell type 1-driven response. This study shows that gram-negative bacteria may contribute to this effect by upregulating interleukin-18 expression.

Serum IL-18 levels in tuberculosis: comparison with pneumonia, lung cancer and healthy controls

OBJECTIVE

The aim of the present study was to document the serum IL-18 levels in patients with pulmonary tuberculosis (P-TB), extrapulmonary tuberculosis (EP-TB), pneumonia, lung cancer and in healthy controls, and to investigate whether it may assist in the differential diagnosis of P-TB.

METHODOLOGY

A total of 116 patients were included in the study. The study population consisted of patients with P-TB, EP-TB, pneumonia and lung cancer and controls. P-TB patients were graded according to sputum positivity and extent of disease. Serum levels of IL-18 (ELISA) were compared between groups and with other clinical measures of disease.

RESULTS

Compared with the controls, all groups of patients had increased serum levels of IL-18. The highest mean concentration of IL-18 was observed in P-TB. Serum levels of IL-18 in the patients with P-TB correlated well with the extent of disease.

CONCLUSIONS

Although increased serum levels of IL-18 were not specific for TB, the increased levels may favour active TB in radiologically advanced disease where CXR findings are difficult to interpret, and sputum smears or cultures are not helpful.

Expression of a novel cytokine, IL-4delta2, in HIV and HIV-tuberculosis co-infection

BACKGROUND

Correcting the Th2 shift in HIV/AIDS represents a potential intervention strategy. However data on interleukin (IL)-4 expression in HIV or AIDS are un-interpretable because of failure to distinguish between IL-4 and its splice variant and natural antagonist, IL-4delta2.

OBJECTIVE

To determine Th1 [interferon (IFN)-gamma], IL-4delta2 and Th2 (IL-4) expression in whole blood and lung lavage from healthy volunteers and in HIV or HIV-tuberculosis (TB) co-infection.

DESIGN

Cross-sectional with prospective cohort.

METHODS

Expression of IL-4delta2, IL-4 and IFN-gamma were determined by quantitative real-time PCR, using unstimulated cells from whole blood and lung lavage, in 20 HIV-TB (pulmonary) co-infected patients, 20 matched HIV-positive controls and 20 HIV-negative healthy volunteers. Results were correlated with plasma viral load, CD4 cell counts, radiological scores and response to anti-TB treatment.

RESULTS

Compared to HIV negative donors, stable HIV-positive donors did not have increased levels of mRNA encoding IL-4, IL-4delta2 or IFN-gamma in blood or lavage. By contrast, the HIV-TB co-infected donors had increased IL-4 and IFN-gamma in both compartments. However the antagonist, IL-4delta2 was increased only in lavage. Consequently the dominant form was IL-4delta2 in lavage, but IL-4 itself in blood. The lung IL-4/IFN-gamma ratio correlated with radiological disease extent. With anti-TB treatment, IL-4 levels did not change whilst IL-4delta2 levels increased significantly.

CONCLUSIONS

IL-4 and its natural antagonist, IL-4delta2 and are not upregulated in the absence of opportunistic infection. However in HIV-TB co-infection both cytokines increase in lung, but only IL-4 in the periphery. Further studies are required to determine if IL-4 facilitates systemic HIV progression.

In VivoandIn VitroStudies of a Novel Cytokine, Interleukin 4δ2, in Pulmonary Tuberculosis

RATIONALE

Tuberculosis progresses despite potent Th1 responses. A putative explanation is the simultaneous presence of a subversive Th2 response. However, interpretation is confounded by interleukin 4delta2 (IL-4delta2), a splice variant and inhibitor of IL-4.

OBJECTIVE

To study levels of mRNA encoding IL-4 and IL-4delta2, and their relationship to treatment and clinical parameters, in cells from lung lavage and blood from patients with pulmonary tuberculosis.

METHODS

IL-4delta2, IFN-gamma, IL-4, and soluble CD30 (sCD30) levels were measured by polymerase chain reaction and relevant immunoassays in 29 patients and matched control subjects lacking responses to tuberculosis-specific antigens.

RESULTS

mRNA levels for IL-4 and IL-4delta2 were elevated in unstimulated cells from blood and lung lavage of patients versus control subjects (p < 0.005). In control subjects, there were low basal levels of IL-4 and IL-4delta2 mRNA expressed mainly by non-T cells (p < 0.05). However, in patients, there were greater levels of mRNA for both cytokines in both T- and non-T-cell populations (p < 0.05 compared with control subjects). Radiologic disease correlated with the IL-4/IFN-gamma ratio and sCD30 (p < 0.005). After chemotherapy, IL-4 mRNA levels remained unchanged, whereas IL-4delta2 increased in parallel with IFN-gamma (p < 0.05). Sonicates of Mycobacterium tuberculosis upregulated expression of IL-4 relative to IL-4delta2 in mononuclear cell cultures from patients (p < 0.05).

CONCLUSIONS

A Th2-like response, prominent in T cells and driven by tuberculosis antigen, is present in tuberculosis and modulated by treatment, suggesting a role for IL-4 and IL-4delta2 in the pathogenesis of tuberculosis and their ratio as a possible marker of disease activity. The specific antigens inducing the IL-4 response require identification to facilitate future vaccine development strategies.

Prior elevation of IL-18 promotes rapid early IFN-gamma production during staphylococcal infection

Systemic Staphylococcus aureus infection is associated with significant morbidity and mortality arising from both bacterial and host immune factors. IL-18 is a pro-inflammatory cytokine of the IL-1 superfamily that exhibits broad functional effects in innate and acquired immune responses and which has been found in high levels in several chronic inflammatory and autoimmune diseases. Over-expression of IL-18 may promote early resolution of infection or could promote a detrimental exaggerated immune response. This was explored in a model of S. aureus infection. We report increased mortality in Swiss mice that were given recombinant IL-18 prior to inoculation with S. aureus LS-1. IL-18 administration prior to infection induced preferentially enhanced IFN-gamma mRNA expression in peripheral blood leukocytes and spleen, especially splenic NK cells. This correlated with increased IFN-gamma protein detection in serum, and leukocyte and spleen cultures at subsequent discrete time points. These data suggest that increased mortality following gram-positive infection in autoimmune diseases could in part reflect the impact of high levels of pleiotropic pro-inflammatory cytokines such as IL-18 present prior to the onset of infection.

Increased levels of interleukin-18 in bronchoalveolar lavage fluid of patients with idiopathic nonspecific interstitial pneumonia

BACKGROUND

Interleukin-18 (IL-18) is a proinflammatory cytokine that can induce interferon-gamma (IFN-gamma), and it plays an important role in T-helper 1 responses. Among idiopathic interstitial pneumonia (IIP), nonspecific interstitial pneumonia (NSIP) has an increased number of lymphocytes in bronchoalveolar lavage (BAL) fluid compared with usual interstitial pneumonia (UIP). However, the difference in their pathogenesis is unclear.

OBJECTIVE

The present study aims to investigate the roles of IL-18 in patients with idiopathic UIP and idiopathic NSIP.

METHODS

We measured the serum and BAL fluid (BALF) levels of IL-18 and IFN-gamma in 22 patients with IIP (12 with UIP, 10 with NSIP) and 9 healthy volunteers.

RESULTS

Lymphocyte proportions in BALF were significantly higher in NSIP than in UIP and healthy subjects. No significant differences were observed in the serum IL-18 levels of all subjects, while the BALF levels of IL-18 in patients with NSIP were significantly higher than in patients with UIP (p < 0.005) and in healthy subjects (p < 0.005). Among all subjects, the levels of IL-18 in BALF correlated significantly with those in serum and the lymphocyte proportions in BALF. The serum IFN-gamma levels of all subjects were below sensitivity, but there was significant reverse correlation between the levels of IFN-gamma and the lymphocyte proportions in BALF.

CONCLUSION

The lymphocytosis in BALF of patients with idiopathic NSIP and a part of idiopathic UIP might be associated with the high levels of IL-18.

No association between interleukin-18 gene polymorphisms and haplotypes in Dutch sarcoidosis patients

Previously, an association between susceptibility to sarcoidosis and a polymorphism in the interleukin (IL-18) gene (IL-18 -607A/C) has been reported in Japanese. The aim of the present study was to validate this association in a clinically well-characterized population of Dutch Caucasians. Three other polymorphisms at positions -656, -137, and 1248 were included in order to extend the mapping of the IL-18 gene and to enable the construction of haplotypes. Polymorphisms were determined using sequence-specific primers (SSPs) and polymerase chain reaction (PCR). A total of 236 individuals was studied (133 patients and 103 controls). No significant differences were observed in the distribution of the -607 and the other polymorphisms between Dutch sarcoidosis patients and controls. However, significant differences in IL-18 -607 genotype and allele frequency distributions were found between the Dutch and the Japanese. From the investigated IL-18-promoter polymorphisms, we were able to deduce four haplotypes. No differences were observed in haplotype frequencies between Dutch sarcoidosis patients and controls. In conclusion, IL-18 polymorphisms do not appear to influence the susceptibility to sarcoidosis in Dutch Caucasians. Important differences in allele frequencies were observed between Japanese and Dutch sarcoidosis patients and controls.

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.

Elevated interleukin-18 levels in bronchoalveolar lavage fluid of patients with eosinophilic pneumonia

BACKGROUND

Interleukin (IL)-18 can induce Th2 cytokine production particularly in collaboration with IL-2. Accumulation of Th2 cells and increased levels of Th2 cytokines are found in bronchoalveolar lavage fluid (BALF) from patients with eosinophilic pneumonia (EP). To evaluate the role of IL-18 in the pathogenesis of EP, we measured the concentration of IL-2, IL-12, IL-18, and Th2 cytokines in BALF from patients with EP.

METHODS

The concentrations of interferon (IFN)-gamma, IL-2, IL-5, IL-10, IL-12, IL-13, and IL-18 in BALF were measured in patients with idiopathic acute eosinophilic pneumonia (AEP), with idiopathic chronic eosinophilic pneumonia (CEP), with sarcoidosis and healthy volunteers (HV).

RESULTS

The BALF concentrations of Th2 cytokines, IL-5, IL-10, and IL-13, were higher in patients with EP than in sarcoidosis and control. The IL-2 level in BALF was higher in EP than in sarcoidosis and control. The IL-18 and IL-12 (p40 + p70) levels were higher in patients with EP than sarcoidosis, while the level of IL-12 (p70) was below the detection limit in patients with EP. There was a significant correlation between IL-2 level and both IL-5 and IL-13 in BALF of patients with EP.

CONCLUSIONS

Our findings suggest that IL-18 may contribute to Th2 cytokine-dominant responses in patients with EP in collaboration with IL-2.

Characterization of bronchoalveolar lavage T cell subsets in sarcoidosis on the basis of CD57, CD4 and CD8

T cells expressing CD57 (a natural killer cell marker) with interferon-gamma (IFN-gamma) producing capacity increase under various conditions. CD57+ T cells are also present in the bronchoalveolar lavage fluid (BALF) of sarcoidosis, and several phenotypical and functional analyses of these cells have been reported. In the present study, BALF T cells obtained from 52 patients with sarcoidosis were classified further into CD4+CD57+ T cells, CD4+CD57- T cells, CD8+CD57+ T cells and CD8+CD57- T cells and their phenotypes and functional characteristics were assessed. Substantial proportions of these T cell subsets expressed natural killer cell markers CD161 and CD122. The biased expansion of Vbeta2 T cells was observed in both CD4+CD57+ T cells and CD4+CD57- T cells in BALF from most patients, while the expansion of other Vbeta T cells was also observed in some patients. Unexpectedly, the biased expansion of certain Vbeta T cells was also seen in either CD8+CD57+ T cells or CD8+CD57- T cells, while the expanded Vbeta T cells in CD8+ T cells differed substantially among individuals. BALF T cells showed a remarkably lower T cell receptor (TCR) intensity than that of peripheral blood T cells. Both CD8+ T cell subsets in BALF of sarcoidosis expressed the intracellular perforin/granzyme B, while all four subsets expressed intracellular IFN-gamma after in vitro activation, and CD4+ T cells, especially CD4+CD57+ T cells, expressed tumour necrosis factor-alpha. These findings indicate that CD57+ T cells as well as CD57- T cells in the BALF are phenotypically and functionally different from peripheral blood T cells and may play an important role in the Th1 dominant state and inflammation in pulmonary sarcoidosis.

Association between interleukin-18 gene polymorphism 105A/C and asthma

BACKGROUND

IL-18 has been shown to exert anti-allergic or allergy-promoting activities, but the existence of genetic polymorphisms in the coding regions of IL-18 gene has not been demonstrated.

OBJECTIVE

The aim of this study was to investigate whether polymorphism is present in the coding regions of the IL-18 gene and, if so, to further analyse the association between polymorphism and asthma in a case-control study.

METHODS

We screened the coding regions of the IL-18 gene for polymorphisms by using PCRsingle-stranded conformation polymorphism and direct sequencing of PCR products, followed by analysis of the association between polymorphism and asthma.

RESULTS

We identified one polymorphism (105A/C) in the coding regions. The frequency of the 105A allele was significantly higher in asthmatic patients than in controls (P<0.01; odds ratio (OR)=1.83 (1.37-2.26)). Significant linkage disequilibrium was observed between the 105A/C and -137G/C polymorphisms in the 5' flanking region of the IL-18 gene (D=0.58, P<0.0001). However, in asthmatic patients the 105A allele was not associated with either total serum IgE or IL-18 levels.

CONCLUSION

The 105A/C polymorphism of the IL-18 gene may be associated with the pathogenesis of asthma.

Elevated levels of interleukin-18 and tumor necrosis factor-alpha in serum of patients with type 2 diabetes mellitus: relationship with diabetic nephropathy

To compare levels of interleukin (IL)-18, tumor necrosis factor-alpha (TNF-alpha), and IL-6 in serum, we studied 151 type 2 diabetes mellitus patients with various degrees of nephropathy, as well as 80 healthy volunteers. IL-18, TNF-alpha, and IL-6 in serum were measured using an enzyme-linked immunosorbent assay (ELISA) with the respective mouse monoclonal antibodies. Significant differences in serum levels of IL-18 and TNF-alpha were observed between the patients and control subjects (IL-18, 278.0 +/- 11.9 pg/mL v 172.8 +/- 7.7 pg/mL, P <.0001; TNF-alpha, 2.41 +/- 0.18 pg/mL v 0.46 +/- 0.18 pg/mL, P <.0001), whereas that of IL-6 was not different between the two groups (0.73 +/- 0.10 pg/mL v 0.65 +/- 0.08 pg/mL, difference not significant [NS]), although patients with nephropathy showed higher levels. In addition, IL-18 levels were increased in diabetic patients with the development of urinary albumin excretion, with the highest found in those with microalbuminuria (<30 micro g/mg creatinine, 252.7 +/- 16.4 pg/mL; 30 to >300 micro g/mg creatinine, 352.7 +/- 35.2 pg/mL; >>300 micro g/mg creatinine, 350.0 +/- 16.0 pg/mL). Similarly, TNF-alpha and IL-6 in diabetic patients with microalbuminuria or clinical albuminuria were significantly increased as compared with those without albuminuria (TNF-alpha, 3.20 +/- 0.41 pg/mL v 1.94 +/- 0.18 pg/mL; IL-6, 1.64 +/- 1.11 pg/mL v 0.51 +/- 0.05 pg/mL, P <.05, respectively). These results suggest that serum levels of IL-18, TNF-alpha, and IL-6 may have some etiopathogenic roles in diabetic nephropathy.

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.

Infliximab treatment of sarcoidosis

OBJECTIVE

To determine whether there is sufficient evidence in the literature to support the use of infliximab in the treatment of sarcoidosis.

DATA SOURCES AND SELECTION

Literature was accessed through MEDLINE (1966-August 2002), OVID (2001-January 2003), and bibliographic searches. Additional databases were also searched. Published literature relevant to the use of infliximab in the treatment of sarcoidosis was evaluated.

DATA SYNTHESIS

In theory, tumor-necrosis factor-alpha blockade appears to be an optimal strategy for treating sarcoidosis. Case series reporting the use of infliximab in refractory sarcoidosis was reviewed to evaluate its potential role as a treatment option.

CONCLUSIONS

Although there is insufficient evidence suggesting that infliximab is an appropriate alternative to conventional treatment options as first-line therapy for sarcoidosis, the preliminary outlook on its use in treatment-refractory cases is promising.

Interleukin-18

Interleukin-18 (IL-18), a recently described member of the IL-1 cytokine superfamily, is now recognized as an important regulator of innate and acquired immune responses. IL-18 is expressed at sites of chronic inflammation, in autoimmune diseases, in a variety of cancers, and in the context of numerous infectious diseases. This short review will describe the basic biology of IL-18 and thereafter address its potential effector and regulatory role in several human disease states including autoimmunity and infection. IL-18, previously known as interferon-gamma (IFN-gamma)-inducing factor, was identified as an endotoxin-induced serum factor that stimulated IFN-gamma production by murine splenocytes [(1) ]. IL-18 was cloned from a murine liver cell cDNA library generated from animals primed with heat-killed Propionibacterium acnes and subsequently challenged with lipopolysaccharide [(2) ]. Nucleotide sequencing of murine IL-18 predicted a precursor polypeptide of 192 amino acids lacking a conventional signal peptide and a mature protein of 157 amino acids. Subsequent cloning of human IL-18 cDNA revealed 65% homology with murine IL-18 [(3) ] and showed that both contain an unusual leader sequence consisting of 35 amino acids at their N terminus.

The cytokine network in sarcoidosis and its clinical relevance

In recent years, analysis of the cytokine network has substantially improved our knowledge of the immunopathogenesis of sarcoidosis. There is increasing evidence from clinical immunology that analysis of the cytokine network may be helpful for clinicians to assess the extent and activity of sarcoid inflammation. Genetic polymorphisms may contribute to interindividual differences in the regulation of cytokine release. Thus, disease phenotype-associated haplotypes should exist and their analysis might disclose risk profiles of individual patients. Furthermore, serological assessment of cytokines or soluble cytokine receptors may become suitable parameters in clinical practice to detect an ongoing inflammation in chronic sarcoidosis.

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.

Reduced interleukin-18 levels in BAL specimens from patients with asthma compared to patients with sarcoidosis and healthy control subjects

STUDY OBJECTIVES

To investigate whether differing airway interleukin (IL)-18 levels may be implicated in the pathogenesis of asthma and sarcoidosis.

SETTING

University teaching hospital.

PATIENTS AND METHODS

IL-18 levels were measured in BAL fluid and in the supernatant of lipopolysaccharide (LPS)-stimulated alveolar macrophages obtained by BAL from 15 patients with sarcoidosis, 11 patients with asthma, and 13 healthy subjects. We also examined the relationship between IL-18 levels and macrophage and lymphocyte concentrations in BAL fluid. IL-18 was measured using an in-house enzyme-linked immunosorbent assay.

RESULTS

IL-18 levels were significantly lower in BAL fluid from patients with asthma (median, 0.0 pg/mL; interquartile range, 0.0 to 0.0 pg/mL) compared to patients with sarcoidosis (median, 222.0 pg/10(6); interquartile range, 110 to 340 pg/mL; p = 0.009, Mann Whitney rank-sum test) and healthy control subjects (median, 162 pg/mL; interquartile range, 38 to 203 pg/mL; p = 0.025, Mann Whitney rank-sum test). Individual analyses comparing IL-18 levels with BAL macrophage counts, and IL-18 with lymphocyte counts in the three groups showed no correlation between these indexes. The mean levels of IL-18 in unstimulated macrophage supernatants were 410 pg/10(6) cells for patients with asthma, 723.4 pg/10(6) cells for patients with sarcoidosis, and 734.8 pg/10(6) cells for healthy control subjects (p > 0.05). Stimulated macrophages from patients with sarcoidosis responded with increasing amounts of IL-18 at lower doses of LPS than macrophages from healthy control subjects or patients with asthma.

CONCLUSION

Our findings suggest that inherently low levels of IL-18 may be associated with the pathogenesis of asthmatic airway inflammation.

Plasma interleukin-18 levels in patients with psychiatric disorders

There are an increasing number of reports on an association between the alteration of circulating cytokine levels and pathophysiology of psychiatric disorders. Plasma concentrations of interleukin (IL)-18 were measured in 13 nonmedicated patients with psychiatric disorders. There was a significant elevation of IL-18 levels in patients with major depression (n = 8) and panic disorder (n = 5), compared with normal controls. The mean IL-18 value of our psychiatric patients was comparable with that of various somatic disorders reported. We suggest that the elevation of plasma IL-18 levels reflects the increased production and release of IL-18 in the central nervous system under stressful settings. We propose that the measurement of IL-18 plasma levels may provide a useful index for the involvement of immune system in psychiatric disorders.

Circulating levels of interleukin 18 reflect etiologies of heart failure: Th1/Th2 cytokine imbalance exaggerates the pathophysiology of advanced heart failure

BACKGROUND

Proinflammatory cytokines such as tumor necrosis factor alpha play an important role in the pathophysiology of CHF. However, the mechanisms of immune activation in CHF remain unknown. Interleukin (IL)-18, a newly discovered cytokine with pleiotropic activities, is known to induce proinflammatory cytokines, chemokines, nitric oxide, and prostaglandins.

METHODS AND RESULTS

We studied 86 patients with New York Heart Association functional class II-IV heart failure. Mean age was 62 years, 20 were women, and mean left ventricular ejection fraction was 34.8%. Circulating levels of IL-18 and IL-10, high-sensitivity testing for C-reactive protein, and brain natriuretic peptide levels were determined. Serum IL-18 concentrations were significantly higher in patients with NYHA class IV than in patients with classes II and III (P <.001). The serum level of IL-18 and the ratio of IL-18 to IL-10 were greater in patients with ischemic cardiomyopathy than in those with dilated cardiomyopathy.

CONCLUSIONS

Th1/Th2 cytokine imbalance exists in patients with advanced CHF according to various etiologies of CHF. The findings suggest an important role for IL-18 in the pathophysiology of CHF and provide a direction for more specific immunomodulating therapy.