Single nucleotide polymorphisms of the IL18 gene are associated with atopic eczema

Regulatory polymorphisms in the interleukin-18 promoter are associated with hepatitis C virus clearance

The immune response is critical in determining the outcome of hepatitis C virus (HCV) infection. Interleukin (IL)-18 is a pivotal mediator of the Th1/Th2-driven immune response. Two IL-18 promoter polymorphisms (-607C/A and -137G/C) and their haplotypes were known to affect IL-18 expression. We examined the role played by these polymorphisms in determining HCV clearance or persistence. Genotyping was performed among African American injection drug users with HCV clearance (n = 91) or HCV persistence (n = 182) and among European Americans with hemophilia who were mainly infected through plasma transfusion. Among injection drug users, IL18 -607A (odds ratio [OR], 3.68 [95% confidence interval {CI},1.85-7.34]) and IL18 -137C (OR, 2.33 [95% CI, 1.24-4.36]) were significantly associated with HCV clearance. A haplotype carrying -607A and -137C (OR, 4.53 [95% CI, 1.77-11.6]) was also strongly associated with viral clearance. No association was found among those with hemophilia. These results suggest that IL18 promoter polymorphism may affect the outcome of HCV infection in certain groups.

Association of interleukin-18 polymorphisms and plasma level with the outcome of chronic HCV infection

Hepatitis C virus (HCV) infection is the main cause of chronic liver disease throughout the world, and may progress to cirrhosis and hepatocellular carcinoma (HCC). Immunological factors, especially cytokines and some host genetic variations, rather than direct HCV action, seem to play an important role in the pathogenesis of HCV infection. Elevated levels of interleukin-18 (IL-18) were described previously for chronically (HCV)-infected patients. This study is aimed at investigating IL-18 promoter polymorphisms (-607C/A and -137G/C) in HCV-infected patients with different disease severities (chronic hepatitis C, liver cirrhosis and HCC) and establishing an association between these polymorphisms and IL-18 plasma concentration with the outcome of chronic HCV infection. The carriage of at least one C allele at position -607 (CC + CA) was associated with a higher risk of cirrhosis and HCC (P = 0.032). Compared with controls, HCV-infected patients had significantly higher levels of IL-18 (P = 0.0001) that correlate with disease severity (P = 0.01, P = 0.001, P = 0.0006, respectively). In conclusion, we supposed a possible implication of IL-18 promoter polymorphisms in the pathogenesis of chronic HCV infection.

The genetics of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a complex genetic disorder influenced by environmental factors. The mode of inheritance and genes involved are not clear.

RESULTS

This report here is focusing on the current progress in searching the disease-susceptibility genes of AD via both the linkage studies and candidate gene approaches. Genome-wide linkage studies have identified multiple susceptibility loci on 3q and 17q. Candidate region linkage studies identify other susceptibility loci on 5q23-33, 11q13, and 13q12-14. At least 28 candidate genes have to date been verified in association studies, but only association with genes of interleukin (IL)-4, IL-13, IL-4RA, mast cell chymase, and serine protease inhibitor, kazal-type 5 have been replicated in more than two different studies. More halpotype tests and family-based association studies may help to shed more light for the candidate gene approach.

CONCLUSION

Determining the candidate susceptibility genes for AD is not only helping understanding the pathophysiology but also affecting the response to therapy, which is important in pharmacogenetics. The effect of environmental trigger may also have to be considered to elucidate the real face of the disease.

Genetic susceptibility to atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with an increasing prevalence in industrialized countries. AD belongs to the group of allergic disorders that includes food allergy, allergic rhinitis, and asthma. A multifactorial background for AD has been suggested, with genetic as well as environmental factors influencing disease development. Recent breakthroughs in genetic methodology have greatly augmented our understanding of the contribution of genetics to susceptibility to AD. A candidate gene association study is a general approach to identify susceptibility genes. Fifty three candidate gene studies (50 genes) have identified 19 genes associated with AD risk in at least one study. Significant associations between single nucleotide polymorphisms (SNPs) in chemokines (chymase 1-1903A > G), cytokines (interleukin13 Arg144Gln), cytokine receptors (interleukin 4 receptor 1727G > A) and SPINK 1258G > A have been replicated in more than one studies. These SNPs may be promising for identifying at-risk individuals. SNPs, even those not strongly associated with AD, should be considered potentially important because AD is a common disease. Even a small increase in risk can translate to a large number of AD cases. Consortia and international collaborative studies, which may maximize study efficacy and overcome the limitations of individual studies, are needed to help further illuminate the complex landscape of AD risk and genetic variations.

Promoter polymorphism of the IL-18 gene is associated with atopic asthma in Tunisian children

Several lines of evidence point to a relevant role of IL-18 in the process of asthma. Some studies suggest that the polymorphism in the gene of IL-18 can be involved in many inflammatory and atopic diseases such as asthma. The aim of our study is to estimate the frequency of the IL-18-607 C/A (rs 1946518) promoter polymorphism in Tunisian children with asthma. We investigated whether the presence of this polymorphism -607 C/A was associated with asthma or atopy and whether this polymorphism influenced the severity of asthma in affected children. We examined also the relationship between the IL-18 gene polymorphism and the serum total IgE level. The IL-18/-607 C/A polymorphism was analysed by polymerase chain reaction and restriction fragment-length polymorphism (PCR-RFLP) analysis. A total of 105 asthma patients and 112 controls as part of the whole children population were studied in a case-control study. Among the 105 children with asthma, 40 were also studied for linkage analyses with their respective parents. We noted that the A allele was associated with statistically significant increases in the risk of asthma in the case-control study (odd ratio (OR) = 1.55, 95% confidence interval (CI) 1.03-2.33. Moreover, the A allele was also associated with atopic asthma (P = 0.008), but not with asthma severity. The transmission disequilibrium test (TDT) analysis in this family study did not suggest a preferential transmission of the IL-18/ -607 C/A polymorphism to affected children. There is no correlation between the IgE level and the IL-18 -607 C/A promoter polymorphism. Our data indicate that IL-18 -607 C/A promoter polymorphism is associated with susceptibility to developing asthma in Tunisian population.

Polymorphism of interleukin-18 promoter influences the onset of kidney graft function after transplantation

It has been well recognized that the promoter polymorphisms of interleukin-18 (IL-18) influence the level of cytokine expression. In our previously published data, we showed constitutive IL-18 expression in the epithelium of renal distal tubules in patients after kidney transplantation and significantly elevated IL-18 expression during acute rejection. In this study, we evaluated the clinical significance of two functional promoter polymorphisms of the IL-18 gene at positions -607 A/C (rs1946518) and -137 C/G (rs187238) in patients after kidney transplantation and looked for associations with the onset of graft function and the incidence of rejection episodes. Promoter polymorphisms in 124 patients and 103 unrelated controls were evaluated by sequence-specific primer polymerase chain reaction and the allele, genotype and haplotype frequencies were statistically correlated. We found a statistically different distribution of the allele frequency of -607 A/C polymorphism between patients with immediate or delayed onset of kidney graft function. Data showed that the C allele, which contributes to higher IL-18 expression, is more frequent in patients with delayed onset of function (P = 0.03, odds ratio = 1.93; 95% confidence interval = 1.15-3.25). A/C single nucleotide polymorphisms of the IL-18 promoter at position -607 may influence the onset of early kidney allograft function.

Interleukin (IL)-18 polymorphism 133C/G is associated with severe respiratory syncytial virus infection

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of bronchiolitis in infants. During the course of RSV infection, predominant T helper cell (TH) 2 response is associated with disease progression, whereas predominant TH1 reaction provides convalescence. Interleukin (IL)-18 plays an important role in adjusting the TH1/TH2 immune response to viral infections. Thus, we tested the hypothesis that polymorphisms in IL-18 were associated with severe RSV-associated diseases.

METHODS

We chose to study the promotor polymorphisms -607A/C (rs1946518) and -137G/C (rs187238), the 2 exon polymorphisms 113T/G (rs360718) and 127C/T (rs360717), and 2 intron polymorphisms 5304A/G (rs795467) and 133G/C (rs360721) within the IL-18 gene. Genotyping was performed on 154 children with severe RSV infection as defined by strict clinical criteria and on 270 controls. Statistical analyses of single polymorphisms made use of the Armitage's trend test, haplotypes were calculated with FASTEHPLUS and FAMHAP.

RESULTS

-133G/C showed association with severe RSV infection (P = 0.043). The association was further supported by haplotype analyses with all 6 polymorphisms (P < 0.00001 for association with RSV).

CONCLUSIONS

This study indicates possible involvement of IL-18 in the determination of severe RSV-associated diseases. Defining the genetic basis of RSV bronchiolitis might help us in identifying new drug targets for a more specific therapy. In addition, it might enable an early identification of children at risk for RSV bronchiolitis and thus make a selective prevention feasible.

Association of the single-nucleotide polymorphism and haplotype of the interleukin 18 gene with atopic dermatitis in Koreans

BACKGROUND

IL-18 is a proinflammatory cytokine that plays an important role for T-helper type 1 (Th1) and Th2 cytokine in the presence/absence of IL-12. It has been recently shown that human IL-18 plays a role in atopic dermatitis (AD) by enhancing IL-4 and IL-13 production and by stimulating the synthesis of IgE.

OBJECTIVE

We wanted to evaluate the associations of single-nucleotide polymorphism (SNP) and the haplotype in the IL-18 gene, hence we performed genotyping for the SNPs in the IL-18 gene in AD patients and normal controls.

METHOD

We genotyped three SNPs from the IL-18 gene for the 1120 case-control samples (646 AD patients and 474 normal controls). We measured the serum IL-18, IL-4 and IL-13 concentrations in 74 individuals (25 ADe, 25 ADi and 24 controls) by performing ELISA.

RESULT

The rs795467 SNP and haplotype T-T-C were significantly associated with AD, and especially between the ADe and normal control groups (P=0.03 and 0.01). The serum IL-18 concentration was higher in the AD group than in the normal controls without any correlation with the rs795467 polymorphism. We did not find any correlations between the serum IL-18 levels and the SCORing atopic dermatitis index, the blood eosinophil counts and the ECP, and there was no correlation between the serum IL-18 levels and the serum IL-4 and IL-13 levels.

CONCLUSION

We found that the one SNP and the haplotype T-T-C were strongly associated with the allergic type of AD, but not with the non-allergic intrinsic type. These data support the hypothesis that IL-18 up-regulates IgE production, yet more experiments will be needed to prove the in vivo involvement of Th2 cytokine.

The association of interleukin-18 genotype and serum levels with metabolic risk factors for cardiovascular disease

OBJECTIVE

Circulating levels of interleukin (IL)-18 are associated with the metabolic syndrome and risk for the development of cardiovascular disease (CVD). This study investigated the association between the circulating IL-18 levels and the -137 G/C polymorphism within the IL-18 gene with metabolic risk factors for CVD in normal-weight and obese black South African women.

METHODS

Blood pressure (BP), body composition (dual-energy X-ray absorptiometer), visceral adiposity (computerized tomography), as well as fasting glucose, insulin, lipid profile, IL-18 levels, and IL-18 genotype were measured in 104 normal-weight (body mass index (BMI) < or = 25 kg/m2) and 124 obese (BMI > or = 30 kg/m2) black South African women.

RESULTS

Subjects with a GC genotype (23%) had a greater mean arterial pressure (MAP, 90.6+/-11.1 vs 85.5+/-10.3 mmHg, P<0.001) than the subjects with the GG genotype. Serum IL-18 levels were not associated with IL-18 genotype (P=0.985); however, they significantly correlated with percentage of body fat (r=0.25, P<0.001), visceral adiposity (r=0.32, P<0.001), MAP (r=0.22, P=0.001), HOMA-IR (r=0.33, P<0.001), fasting insulin (r=0.25, P<0.001), triglyceride (r=0.16, P<0.05), and high-density lipoprotein-cholesterol (r=-0.14, P<0.05) levels, after adjusting for age and body fatness.

CONCLUSIONS

We show for the first time that the GC genotype of the IL-18 -137 G/C polymorphism and the circulating IL-18 levels are independently associated with raised BP. Moreover, fasting IL-18 levels are associated with the other metabolic risk factors for CVD in normal-weight and obese black South African women.

Relationship between Kaposi's varicelliform eruption in Japanese patients with atopic dermatitis treated with tacrolimus ointment and genetic polymorphisms in the IL-18 gene promoter region

Kaposi's varicelliform eruption is the most important problem in treating patients with atopic dermatitis (AD) with tacrolimus ointment. It has been considered that Kaposi's varicelliform eruption occurs due to decreased levels of interleukin (IL)-18. The aim of this study was to examine the relationship between Kaposi's varicelliform eruption and genetic polymorphisms in the IL-18 gene. IL-18 gene promoter polymorphisms were analyzed in 21 AD patients treated with tacrolimus ointment and in 100 healthy volunteers. Six AD patients with Kaposi's varicelliform eruption during the treatment with tacrolimus ointment showed significantly higher frequency in G-to-C mutations at the IL-18 gene promoter region -137 compared with 15 AD patients without Kaposi's varicelliform eruption. The 15 AD patients without Kaposi's varicelliform eruption as well as 100 healthy volunteers did not have mutations of G-to-C at the IL-18 gene promoter region -137. These results suggest that the onset of Kaposi's varicelliform eruption following the treatment with tacrolimus ointment is associated with the mutation of G-to-C in the IL-18 gene promoter region -137, and that caution is required when using tacrolimus ointment for treating AD patients with this mutation.

IL-18 gene promoter ?137C/G and ?607C/A polymorphisms in Chinese Han children with type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a heterogeneous autoimmune disease, and both environmental and genetic factors play a role in its pathogenesis. Interleukin (IL)-18 is a potent pro-inflammatory cytokine capable of inducing interferon-gamma production that is associated with the development of T1DM. The gene for IL-18 is located on chromosome 11q22.2-q22.3 and has been reported to be associated with a susceptibility to T1DM. To test the putative involvement between IL-18 gene polymorphism and predisposition to T1DM, we conducted a case-control study in Chinese Han children. The single nucleotide polymorphisms at position -607(C/A) and -137(C/G) in the promoter region of the IL-18 gene were analysed by sequence-specific primers-polymerase chain reaction in 118 patients with T1DM and 150 healthy controls. (1) The allele frequency of -607A was 41.2% and 53.0%, respectively, in patients and in control subjects (P = 0.01), but the allele frequency of -137C/G was not statistically significant (P = 0.37). (2) The distribution of CC genotype at position -607 was significantly different between patients and normal controls (P = 0.03), while the distribution of AA genotype in patients was significantly lower than that in the controls (P = 0.03). (3) Furthermore, there was a significant increase in haplotype (-137C/-607G) and genotype combination (-137GG/ -607CC) in patients compared with controls (P = 0.03 and P = 0.04, respectively). The results of this study show that IL-18 gene promoter polymorphisms confer susceptibility to T1DM in Chinese Han children. Moreover, subjects carrying AA genotype at position -607 of the promoter of IL-18 gene may be a low risk of T1DM development.

Interleukin-18 and its three gene polymorphisms relating to allergic rhinitis

The study aimed to examine an association of three different single nucleotide polymorphisms (SNPs) of the IL-18 gene (-607 C/A, -137 G/C and -133 C/G) on chromosome 11q22 with allergic rhinitis (AR). Genotyping for the SNPs was performed using 539 patients with AR and 312 healthy control volunteers. Positivity to the skin prick test for the fungus Alternaria sp. in patients with AR, and IgE levels according to particular genotypes of selected SNPs, were also determined. There were no significant differences in the distribution of single IL-18 alleles or genotypes between controls and AR patients. However, frequencies of combined IL-18 genotypes arising from combinations of the three common polymorphisms (-607, -137 and -133) were significantly different between both groups (P = 0.009, P (corr) < 0.05, OR = 5.35, 95% CI: 1.9-15.2). There was a marginally significant association of the IL-18-607 variant with IgE levels (P = 0.05) in patients, but not in the case of the other SNPs. Patients allergic to Alternaria, but not those allergic to other antigens, showed a significant association with the IL-18-607 polymorphism (P = 0.0037, P (corr) < 0.05). Results suggest that IL-18 gene variants may be one of the factors participating in the pathogenesis of AR or its intermediary phenotypes.

Interleukin-18 Promoter Polymorphisms in Patients With Behçet’s Disease

Behçet's disease (BD) is an idiopathic systemic inflammatory disease and is considered to be a T helper 1 (Th1) type cytokine driven disorder. Moreover, levels of interleukin-18 (IL-18), a pivotal mediator of Th1 cytokine response, have been reported to be upregulated in BD. Therefore, we investigated the distribution of IL-18 promoter -607 C/A and -137 G/C polymorphisms in 103 BD patients (mean age 41.0 years; 48 male, 55 female) using allele-specific-polymerase chain reaction. As compared with healthy control subjects, BD patients had a significantly higher frequency of the -607 CC genotype (42.7% vs 23.3%, odds ratio [OR] = 2.455, 95% confidence interval [CI] = 1.350-4.461, p(c) = 0.021) and a higher frequency of the -607 C allele (60.7% vs 48.1%, OR = 1.668, 95% CI = 1.129-2.464, p = 0.0101). Haplotype analysis showed that BD patients had significantly less -607A/-137G haplotype (27.3% vs 44.2%, OR = 0.469, 95% CI = 0.268-0.820, p(c) = 0.032) and -607A/-137G haplotype homozygote (5.8% vs 20.4%, OR = 0.242, 95% CI = 0.096-0.612, p(c) = 0.014) than control subjects. In addition, the frequency of -607C/-137G haplotype homozygote was significantly higher in BD patients than control subjects (48.5% vs 20.4%, OR = 3.684, 95% CI = 1.997-6.791, p(c) = 0.0014). Although there were no associations between the polymorphisms and clinical manifestations or severity, patients with the -607 CC genotype or -607C/-137G haplotype homozygote showed significantly earlier symptom development (p = 0.034 by ANOVA; p = 0.009 by t-test, respectively) than those with other genotypes or diplotypes. These results suggest that the IL-18 promoter gene is a candidate susceptibility gene in BD patients.

The common G-allele of interleukin-18 single-nucleotide polymorphism is a genetic risk factor for atopic asthma. The SAPALDIA Cohort Study

BACKGROUND

IL-18 is a pleiotrophic cytokine involved in both, T-helper type 1 (Th1) and Th2 differentiation. Recently genetic variants in the IL-18 gene have been associated with increased risk of atopy and asthma.

OBJECTIVE

To examine the relationship of a genetic, haplotype-tagging promotor variant -137G/C in the IL-18 gene with atopic asthma in a large, well-characterized and population-based study of adults.

METHODS

Prospective cohort study design was used to collect interview and biological measurement data at two examination time-points 11 years apart. Multivariate logistic regression analysis was used to assess the association of genotype with asthma and atopy.

RESULTS

The G-allele of the IL-18 promotor variant (-137G/C) was associated with a markedly increased risk for the prevalence of physician-diagnosed asthma with concomitant skin reactivity to common allergens. Stratification of the asthma cases by skin reactivity to common allergens revealed an exclusive association of IL-18 -137 G-allele with an increased prevalence of atopic asthma (adjusted odds ratio (OR): 3.63; 95% confidence interval: (1.64-8.02) for GC or GG carriers vs. CC carriers), and no according association with asthma and concomitant negative skin reactivity (adjusted OR: 1.13; 0.66-1.94). The interaction between IL-18 -137G/C genotype and positive skin prick test was statistically significant (P=0.029). None of 74 incident asthma cases with atopy at baseline exhibited the CC genotype.

CONCLUSION

Our results strongly suggest that this variant of the IL-18 gene is an important genetic determinant involved in the development of atopic asthma.

Cytokines and chemokines orchestrate atopic skin inflammation

Atopic dermatitis (AD) is a common pruritic and chronically relapsing inflammatory skin disease. The pathophysiology of AD includes disturbed skin barrier functions, frequent allergic responses against allergens, defects in the antimicrobial immune defense, and a genetic predisposition. In this review we summarize advances in our understanding of the complex interdependent network of members of the rapidly growing protein superfamilies of cytokines and chemokines that lead to the development of AD.

Diagnosis and treatment of atopic dermatitis in children and adults: European Academy of Allergology and Clinical Immunology/American Academy of Allergy, Asthma and Immunology/PRACTALL Consensus Report

There are remarkable differences in the diagnostic and therapeutic management of atopic dermatitis practiced by dermatologists and pediatricians in different countries. Therefore, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams who were given the task of finding a consensus to serve as a guideline for clinical practice in Europe as well as in North America. The consensus report is part of the PRACTALL initiative, which is endorsed by both academies.

Contribution of IL-18 to atopic-dermatitis-like skin inflammation induced by Staphylococcus aureus product in mice

Atopic dermatitis (AD) is a common inflammatory skin disease of unknown etiology. Cutaneous infection with microbes such as Staphylococcus aureus and/or skin cleansing with detergent exacerbates clinical AD. Here, we generated an AD animal model by destroying skin barrier function with detergent and subsequent topical application of protein A from S. aureus (SpA). NC/Nga mice, which genetically have reduced skin barrier function, and BALB/c mice having intact skin barrier function, were susceptible to this combination and developed severe and moderate AD, respectively, associated with dermal accumulation of eosinophils and mast cells. Both types of mice showed an increase in serum levels of IL-18, but not IgE. The epidermis of the NC/Nga mice rapidly expressed T helper type 1 (Th1)-associated chemokines, including ligands for CXCR3 and CCR5, after application of both SpA and detergent, but not after application of detergent alone. Although treatment with detergent induced moderate Th1 cell response, additional SpA treatment was a prerequisite for induction of the differentiation of naive T cells toward unique Th1 cells, termed "super Th1 cells," capable of producing both Th1 (IFN-gamma) and T helper type 2 cytokine (IL-13), as well as IL-3, and expressing CXCR3 and CCR5. Induction of super Th1 cells required IL-18 stimulation. Blockade of IL-18 prevented AD development, whereas blockade of IL-3 partially prevented AD development, suggesting a contribution of IL-18-dependent IL-3 production to AD with cutaneous mastocytosis. il18-/-BALB/c mice similarly evaded SDS/SpA-induced AD. Thus, IL-18 might be important for the development of infection-associated AD by induction of IL-3 from super Th1 cells.

A promoter haplotype of the interleukin-18 gene is associated with juvenile idiopathic arthritis in the Japanese population

Recently, we reported that genetic polymorphisms within the human IL18 gene were associated with disease susceptibility to adult-onset Still's disease (AOSD), which is characterized by extraordinarily high serum levels of IL-18. Because high serum IL-18 induction has also been observed in the systemic type of juvenile idiopathic arthritis (JIA), we investigated whether similar genetic skewing is present in this disease. Three haplotypes, S01, S02, and S03, composed of 13 genetic polymorphisms covering two distinct promoter regions, were determined for 33 JIA patients, including 17 with systemic JIA, 10 with polyarthritis, and 6 with oligoarthritis. Haplotypes were also analyzed for 28 AOSD patients, 164 rheumatoid arthritis (RA) patients, 102 patients with collagen diseases, and 173 healthy control subjects. The frequency of individuals carrying a diplotype configuration (a combination of two haplotypes) of S01/S01 was significantly higher in the JIA patients, including all subgroups, than in the healthy controls (P = 0.0045, Fischer exact probability test; odds ratio (OR) = 3.55, 95% confidence interval (CI) = 1.55-8.14). In patients with systemic JIA, its frequency did not differ statistically from that of normal controls. Nevertheless, it is possible that haplotype S01 is associated with the phenotype of high IL-18 production in systemic JIA because the patients carrying S01/S01 showed significantly higher serum IL-18 levels compared with patients with other diplotype configurations (P = 0.017, Mann-Whitney U test). We confirmed that the frequency of the diplotype configuration of S01/S01 was significantly higher in AOSD patients than in healthy control subjects (P = 0.011, OR = 3.45, 95% CI = 1.42-8.36). Furthermore, the RA patients were also more predisposed to have S01/S01 (P = 0.018, OR = 2.00, 95% CI = 1.14-3.50) than the healthy control subjects, whereas the patients with collagen diseases did not. In summary, the diplotype configuration of S01/S01 was associated with susceptibility to JIA as well as AOSD and RA, and linked to significantly higher IL-18 production in systemic JIA. Possession of the diplotype configuration of S01/S01 would be one of the genetic risk factors for susceptibility to arthritis in the Japanese population.

IL-18 gene polymorphisms affect IL-18 production capability by monocytes

We previously demonstrated a significant association between IL-18 gene polymorphism 105A/C and asthma. In this study, we investigated the relationship of IL-18 gene polymorphism to IL-18 production capability by monocytes. The frequency of gene polymorphisms including IL-18-105A/C and IL-18--137G/C was determined by PCR analyses. The IL-18 production by monocytes stimulated without or with LPS or A23187+PMA for 1day was measured by ELISA. The produced IL-18 spontaneously or in response to A23187+PMA by monocytes was significantly higher for volunteers with 105A/A genotype than with 105A/C genotype. Similarly, the production capability of IL-18 by monocytes from volunteers with -137G/G genotype was significantly higher than that with -137G/C genotype and significant linkage disequilibrium was observed between 105A/C and -137G/C polymorphism. Thus, the genetic capacity to produce more IL-18 in response to stimuli may affect the onset of asthma.

T regulatory cells in allergen-specific immunotherapy

A dramatic increase in the prevalence of allergy and asthma has occurred during the past few decades. Although the symptoms of many allergic disorders can be suppressed quite effectively by pharmacological interventions, these do not provide a curative solution and therefore involve lifelong use of medication. Allergen-specific immunotherapy (SIT) on the other hand provides a long-lasting effect on the immune response to common environmental antigens, therefore allowing cessation of the therapy after several years. The changes in the immune response brought about by allergen-SIT are slowly being unveiled and explained. Mechanisms underlying allergen-SIT and in particular the role of regulatory T cells will be discussed in this review, based on recent findings and current concepts.

Analysis of polymorphisms of the interleukin-18 gene in type 1 diabetes and Hardy-Weinberg equilibrium testing

Recently, the interleukin-18 cytokine gene (IL18) was reported to be associated with type 1 diabetes. In the present report, we calculated that the reported genotypes of the two 5' region/promoter single nucleotide polymorphisms (SNPs), -607 (C-->A) (rs1946518) and -137 (G-->C) (rs187238), were not in Hardy-Weinberg equilibrium (HWE). We therefore investigated the association of the -607 and -137 SNPs in a U.K. type 1 diabetic Caucasian case-control collection (1,560 case and 1,715 control subjects tested at -607 and 4,323 case and 4,610 control subjects tested at -137) as well as a type 1 diabetic Caucasian collection comprised of families of European ancestry (1,347 families tested at -137 and 1,356 families tested at -607). No evidence for association with type 1 diabetes was found, including for the -607 A/A and C/A genotypes. To evaluate whether common variation elsewhere in the gene was associated with disease susceptibility, we analyzed eight IL18 tag SNPs in a type 1 diabetic case-control collection (1,561 case and 1,721 control subjects). No evidence for association was obtained (P = 0.11). We conclude that common allelic variation in IL18 is unlikely to contribute substantially to type 1 diabetes susceptibility in the populations tested and recommend routine application of tests for HWE in population-based studies for genetic association.

The pathophysiology of atopic eczema

Atopic eczema (AE) represents a pruritic chronic inflammatory skin disease with a complex background, triggered by genetic and environmental factors. Different dendritic cells subtypes, such as Langerhans cells, inflammatory dendritic epidermal cells and plasmacytoid dendritic cells, play a key role in AE and impact on the mechanisms underlying AE, such as the recruitment of inflammatory cells, T-cell priming, and cytokine and chemokine release. In addition, allergens in combination with bacterial and viral stimuli influence the course and severity of AE. In this review, we highlight the recent progress made in the pathophysiology of AE focusing on the latest research results published in this field.

Association between IL-18 gene promoter polymorphisms and inflammatory bowel disease in a Japanese population

BACKGROUND

Interleukin-18 (IL-18) is a pleiotropic cytokine that induces the production of interferon (IFN)-gamma and also to regulate Th2 cytokines. Recently, association studies between IL-18 gene promoter polymorphisms and several Th1- or Th2-mediated inflammatory diseases were reported. In inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), recent evidence suggests that IL-18 is involved in the pathogenesis.

METHODS

Using DNA direct sequencing, we investigated IL-18 gene promoter polymorphisms at -607C/A and -137G/C. Allele, genotype, and haplotype frequencies were determined in 210 Japanese patients with UC, 205 patients with CD, and 212 controls.

RESULTS

In UC, the -137C allele frequency was significantly higher in the proctitis-type patients than in controls (Pc = 0.0068). The -137 genotype frequency was also significantly different in the proctitis-type patients than in controls (Pc = 0.032). No other allele and genotype frequencies were significantly associated with UC after Bonferroni correction. Furthermore, the frequency of haplotype 2 (-607A, -137C), which had a lower promoter activity and IFN-gamma mRNA level than the other haplotypes as previously reported, was significantly higher in the proctitis-type patients than in controls (Pc = 0.01). In CD, we could not find any significant differences.

CONCLUSIONS

IL-18 gene promoter polymorphisms may not be associated with disease susceptibility but related to the extent of disease in UC.

Association of polymorphisms in the interleukin-18 gene in patients with Crohn's disease depending on the CARD15/NOD2 genotype

An increased expression of interleukin-18 (IL-18), a proinflammatory cytokine inducing interferon-gamma, has been found in Crohn's disease (CD). In the IL-18 gene, several partly functional relevant polymorphisms are known. This study sought to investigate associations of IL-18 polymorphisms in inflammatory bowel disease and CD according to CARD15/NOD2 mutation status and clinical phenotypes.

METHODS

The IL-18 polymorphisms -607, -137, and the third position of codon 35 (c35/3) were genotyped in 210 patients with CD, 140 patients with ulcerative colitis, and 265 healthy controls using polymerase chain reaction and restriction fragment length polymorphism analysis.

RESULTS

Frequencies of alleles and genotypes of the 3 polymorphisms and of the respective haplotypes and diplotypes displayed no significant differences between the whole groups of patients with CD and ulcerative colitis, respectively, compared with the controls. After stratification of patients with CD for CARD15/NOD2 status, significant associations of genotypes -137 CC (P = 0.018) and c35/3 CC (P = 0.010) and of the diplotype 2-2 (P = 0.018) were found in cases carrying CARD15/NOD2 mutations. Associations of genotypes -137 GG (P = 0.015) and c35/3 AA (P = 0.030) with colonic disease only in cases positive for CARD15/NOD2 mutations and of the genotype -607 AA (P = 0.007) with fistulas in cases negative for CARD15/NOD2 mutations were observed.

CONCLUSIONS

In this study, significant differences of several genotypes and diplotypes within the IL-18 gene in CD depending on CARD15/NOD2 status have been found. In context with an increased expression of IL-18 in CD, it remains to be shown whether the expression of IL-18 is influenced by CARD15/NOD2 mutation status.