Identifying genes predisposing to atopic eczema

Pathophysiology and Management of Atopic Dermatitis: A Laconic Review

Conclusion:

Atopic Dermatitis (AD) is long-lasting degenerating skin disease with a characteristic phenotype and stereotypically spread skin lesions. The AD results due to a complex interface among genetic factors, host’s surroundings, pharmacological anomalies and immunological factors. In previous decades, researchers had shown marked interest due to increased prevalence in developed countries. In this review, basics along with the advances in pathogenesis and management of AD have been discussed. The immunological factors i.e. Innate Lymphoid Cells, IL-22 and Toll-like receptors have an important role in the pathogenesis. The proactive topical therapy by skincare, topical glucocorticosteroids and calcineurin inhibitors have improved effect in the management of AD. The human monoclonal antibody-based systemic drug (Duplimab) is a considerable advancement in the management of AD. Other monoclonal antibody-based drugs (Lebrikizumab, Tralokinumab, Apremilast and Nemolizumab) are in different phases of clinical trials. A better understanding of genetics and immunoregulatory cascade will lead to the development of efficacious drugs and better management therapy preventing the relapse of flares and improved life quality of AD patients.

Mechanisms of gastrointestinal allergic disorders

Gastrointestinal (GI) allergic disease is an umbrella term used to describe a variety of adverse, food antigen-driven, immune-mediated diseases. Although these diseases vary mechanistically, common elements include a breakdown of immunologic tolerance, a biased type 2 immune response, and an impaired mucosal barrier. These pathways are influenced by diverse factors such as diet, infections, exposure to antibiotics and chemicals, GI microbiome composition, and genetic and epigenetic elements. Early childhood has emerged as a critical period when these factors have a dramatic impact on shaping the immune system and therefore triggering or protecting against the onset of GI allergic diseases. In this Review, we will discuss the latest findings on the molecular and cellular mechanisms that govern GI allergic diseases and how these findings have set the stage for emerging preventative and treatment strategies.

Probiotics and Atopic Dermatitis: An Overview

Atopic dermatitis (AD) is a common, recurrent, chronic inflammatory skin disease that is a cause of considerable economic and social burden. Its prevalence varies substantially among different countries with an incidence rate proclaimed to reach up to 20% of children in developed countries and continues to escalate in developing nations. This increased rate of incidence has changed the focus of research on AD toward epidemiology, prevention, and treatment. The effects of probiotics in the prevention and treatment of AD remain elusive. However, evidence from different research groups show that probiotics could have positive effect on AD treatment, if any, that depend on multiple factors, such as specific probiotic strains, time of administration (onset time), duration of exposure, and dosage. However, till date we still lack strong evidence to advocate the use of probiotics in the treatment of AD, and questions remain to be answered considering its clinical use in future. Based on updated information, the processes that facilitate the development of AD and the topic of the administration of probiotics are addressed in this review.

HPV16 E7 expression in skin induces TSLP secretion, type 2 ILC infiltration and atopic dermatitis-like lesions

Atopic dermatitis is a common pruritic and inflammatory skin disorder with unknown etiology. Most commonly occurring during early childhood, atopic dermatitis is associated with eczematous lesions and lichenification, in which the epidermis becomes hypertrophied resulting in thickening of the skin. In this study, we report an atopic dermatitis-like pathophysiology results in a murine model following the expression of the high-risk Human Papillomavirus (HPV) 16 oncoprotein E7 in keratinocytes under the Keratin 14 promoter. We show that HPV 16 E7 expression in the skin is associated with skin thickening, acanthosis and light spongiosis. Locally, HPV 16 E7 expressing skin secreted high levels of TSLP and contained increased numbers of ILCs. High levels of circulating IgE were associated with increased susceptibility to skin allergy in a model of cutaneous challenge, and to airway bronchiolar inflammation, enhanced airway goblet cell metaplasia and mucus production in a model of atopic march. Surprisingly, skin pathology occurred independently of T-cells and mast cells. Thus, our findings suggest that the expression of a single HPV oncogene in the skin can drive the onset of atopic dermatitis-like pathology through the induction of TSLP and type 2 ILC infiltration.

Atopic dermatitis patients carrying G allele in -1082 G/A IL-10 polymorphism are predisposed to higher serum concentration of IL-10

INTRODUCTION

Atopic dermatitis (AD) is a chronic skin inflammatory disease in which Th2-derived cytokines play an essential role. Aim of the study was to assess interleukin 4, 10 and 13 (IL-4, IL-10 and IL-13) serum concentrations in AD patients and to correlate the values with the occurrence of genotypes of selected polymorphisms in genes encoding these cytokines.

MATERIAL AND METHODS

Seventy-six AD patients (mean age 11.4 years) and 60 healthy controls were enrolled in the study. Blood samples were analyzed for IL-4, IL-10 and IL-13 concentrations with ELISA assay and genotyping for -590C/T IL-4, -1082A/G IL-10 and -1055C/T IL-13 polymorphisms with PCR-RFLP.

RESULTS

The obtained results revealed statistically higher serum concentration of IL-10 and IL-13 in AD patients when compared to healthy controls (10.30 pg/ml vs. 8.51 pg/ml for IL-10 and 5.67 pg/ml vs. 4.98 pg/ml for IL-13). There were no significant differences between AD patients and controls in regard to IL-4 serum level (5.10 pg/ml vs. 7.1 pg/ml). Analyzing the association between level of the examined cytokines and genotype polymorphisms -590 C/T for the IL-4 gene, -1082 A/G for the IL-10 gene and -1055 C/T for the IL-13 gene, we found a statistically higher IL-10 serum level among carriers of the G allele in the -1082 G/A IL-10 polymorphism both in AD and control groups. We did not find any significant differences between serum level of IL-4 and IL-13 in regard to genotype occurrence in examined polymorphisms: -590 C/T for the IL-4 gene and -1055 C/T for the IL-13 gene.

CONCLUSIONS

The obtained results confirm the genetic background of IL-10 synthesis in the Polish population.

Allergic skin disease

The two most common allergic skin diseases in the world are often the least familiar to practicing surgeons: atopic dermatitis and contact dermatitis. When unrecognized, these disorders can cause great discomfort and decreased quality of life. This is only made worse by a surgical procedure which can exacerbate the disease process. Through proper recognition, management, and peri-surgical prophylaxis flares of these diseases can be avoided, leading to decreased morbidity and improved patient satisfaction. This article summarizes the pathophysiology and management of both atopic and contact dermatitis, with attention to implications for the surgeon.

Protocadherin-1 polymorphisms are associated with eczema in two Dutch birth cohorts

BACKGROUND

  Eczema and asthma share a common genetic background and show linkage to chromosome 5q31-33. Protocadherin-1 (PCDH1) is located in this region and was identified as a susceptibility gene for bronchial hyper-responsiveness (BHR), a hallmark of asthma. PCDH1 encodes an adhesion molecule, expressed in airway and skin epithelium. We determined whether PCDH1 polymorphisms, previously associated with asthma or BHR, also associated with questionnaire and UK Working Party (UKWP) defined eczema.

METHODS

  Four PCDH1 polymorphisms were genotyped in two Dutch birth cohorts, PIAMA (n = 967) and KOALA Birth Cohort Study (n = 1560). Association with eczema was determined by chi-square tests and generalized estimating equations (GEE).

RESULTS

  Insertion deletion IVS3-116 was associated with development of UKWP eczema in PIAMA [age 4, OR = 1.90 (1.14-3.18)] and borderline with questionnaire-reported eczema in PIAMA [GEE, OR = 1.33 (0.98-1.81)]. Furthermore, IVS3-116 was associated with questionnaire-reported eczema in KOALA [age 1, OR = 1.44 (1.00-2.07)]. Pooled analysis of questionnaire-reported eczema of both cohorts resulted in a significant association of IVS3-116 with eczema [OR = 1.26 (1.01-1.58)]. Rs3822357 (A-allele) associated with protection for eczema in PIAMA only [questionnaires, OR = 0.19 (0.06-0.63)].

CONCLUSION

  PCDH1 gene variant IVS3-116 associates with eczema in two independent birth cohorts. Combined with previous observations, this indicates a shared genetic susceptibility to BHR, asthma and eczema.

Association analysis of single nucleotide polymorphisms at five loci: comparison between atopic dermatitis and asthma in the Chinese Han population

Atopic diseases, such as atopic dermatitis (AD) and asthma, are closely related to clinical phenotypes with hypersensitivity, and often share some similar genetic and pathogenic bases. Our recent GWAS identified three susceptibility gene/loci FLG (rs11204971 and rs3126085), 5q22.1 (rs10067777, rs7701890, rs13360927 and rs13361382) and 20q13.33 (rs6010620) to AD. The effect of these AD associated polymorphisms in asthma is so far unknown. To investigate whether AD relevant genetic variants is identical to asthma and reveal the differences in genetic factors between AD and asthma in Chinese Han population, seven AD associated single nucleotide polymorphisms (SNPs) as well as 3 other SNPs (rs7936562 and rs7124842 at 11q13.5 and rs4982958 at 14q11.2) from our previous AD GWAS were genotyped in 463 asthma patients and 985 controls using Sequenom MassArray system. We found rs4982958 at 14q11.2 was significantly associated with asthma (P = 3.04×10⁻⁴, OR = 0.73). We also detected one significant risk haplotype GGGA from the 4 SNPs (rs10067777, rs7701890, rs13360927 and rs13361382) at 5q22.1 in AD cases (P_correction = 3.60×10⁻¹⁰, OR = 1.26), and the haplotype was suggestive of risk in asthma cases in this study (P = 0.014, P_correction = 0.084, OR = 1.38). These SNPs (rs11204971, rs3126085, rs7936562, rs712484 and rs6010620) at AD susceptibility genes/loci FLG, 11q13.5 and 20q13.33 were not associated with asthma in this study. Our results further comfirmed that 14q11.2 was an important candidate locus for asthma and demonstrated that 5q22.1 might be shared by AD and asthma in Chinese Han population.

The differences in the involvements of loci of promoter region and Ile50Val in interleukin-4 receptor α chain gene between atopic dermatitis and Japanese cedar pollinosis

BACKGROUND

Atopic dermatitis (AD) and Japanese cedar pollinosis (JCP) are common chronically allergic diseases associated with the activation of T-helper 2 cells. Recent studies have shown that polymorphisms in the genes for IL-4 receptor α chain (IL4RA) may contribute to susceptibility of AD and JCP, although the differences in the involvements of loci of IL4RA gene between AD and JCP are unclear. In this study, we investigated the role of polymorphisms in IL-4RA gene in conferring susceptibility to the development of AD and/or JCP using a family analysis and an association analysis in a Japanese population.

METHODS

Five polymorphisms in the IL-4RA gene, C-3223T, T-1914C, T-890C, Ile50Val and Glu375Ala, have been genotyped using PCR-based methods in 75 trios families, including 15 AD families, 30 JCP families, and 30 families with combination of AD and JCP in the family analysis. Forty-five AD, 60 JCP and 125 control children constituted the association study.

RESULTS

The transmission disequilibrium test showed that the allele of Ile50 was significantly transmitted to children with JCP alone (p < 0.05). Haplotype analysis showed that the -3223T/Ile50 haplotype was preferentially transmitted to both AD (p < 0.01) and JCP children (p < 0.01), while that the C-3223/Ile50 haplotype was preferentially transmitted to only JCP children (p < 0.01). The association study showed that -3223T and haplotype of -3223T/Ile50 were associated with AD children, but not with JCP. Ile50 was associated with both AD and JCP.

CONCLUSIONS

Our data suggest that -3223T and the -3223T/Ile50 haplotype were risk factors for AD. Ile50 allele seems to be involved in both JCP and AD. Interactions of the IL-4RA loci may play a role both conferring susceptibility and modulating severity of AD.

IL-6, VEGF, KC and RANTES are a major cause of a high irritant dermatitis to phthalic anhydride in C57BL/6 inbred mice

BACKGROUND

In previous studies, several strains of mice were used as chemical-induced skin irritation models to identify immunological hazards and elucidate the molecular and cellular mechanisms by which irritant dermatitis disease occur. BALB/c and C57BL/6 mice have been used for most of these experiments. Although there are some differences in the immune response to chemical allergens between these strains, few studies have been conducted to determine what regulatory factors contribute to these variations.

METHODS

To investigate the cause of high responses to skin irritation in C57BL/6 mice that are widely used to study atopic dermatitis, changes in various immune-related factors such as ear thickness, myeloperoxidase activity, lymph node weight, IgE concentration and cytokine concentration were measured in C57BL/6 and BALB/c mice following phthalic anhydride (PA) treatment.

RESULTS

Based on analysis of the skin irritation, C57BL/6 mice showed a greater skin irritation to PA than BALB/c mice, although the IgE concentration and auricular lymph node weight did not contribute to this difference in the response. However, the concentration of several cytokines and chemokines (interleukin [IL]-6 and vascular endothelial growth factor [VEGF], keratinocyte-derived chemokine [KC] and regulated on activation normal T cell expressed and secreted [RANTES]) were significantly higher in C57BL/6 mice than BALB/c mice following treatment with PA.

CONCLUSIONS

Our results suggest that several of the cytokines and chemokines secreted from irritant site could contribute to the regulation mechanism responsible for the difference in the skin irritation among various strains of mice following exposure to PA.

Atopic dermatitis

Atopic dermatitis (AD) is a chronic and relapsing disease affecting an increasing number of patients. Usually starting in early childhood, AD can be the initial step of the so-called atopic march, i.e. followed by allergic rhinitis and allergic asthma. AD is a paradigmatic genetically complex disease involving gene-gene and gene-environment interactions. Genetic linkage analysis as well as association studies have identified several candidate genes linked to either the epidermal barrier function or to the immune system. Stress, bacterial or viral infections, the exposure to aero- or food-allergens as well as hygienic factors are discussed to aggravate symptoms of AD. Athough generalized Th2-deviated immune response is closely linked to the condition of AD, the skin disease itself is a biphasic inflammation with an initial Th2 phase and while chronic lesions harbour Th0/Th1 cells. Regulatory T cells have been shown to be altered in AD as well as the innate immune system in the skin. The main treatment-goals include the elimination of inflammation and infection, preserving and restoring the barrier function and controlling exacerbating factors. The overall future strategy in AD will be aimed to control skin inflammation by a more proactive management in order to potentially prevent the emergence of sensitization as well as to design customized management based on genetic and pathophysiologic information.

Polymorphisms within the C3 gene are associated with specific IgE levels to common allergens and super-antigens among atopic dermatitis patients

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Twin and family studies suggest a strong genetic component of the disease. The keratinocytes secrete high amounts of C3 after stimulation with pro-inflammatory cytokines, which may play a functional role in skin inflammation. In this study, we genotyped four different single nucleotide polymorphisms (SNPs) by melting curve analysis using sequence specific hybridization probes in a well-characterized cohort of AD patients. Among four SNPs within C3 gene, higher frequencies of rs10410674 (23.5% vs 12.2%) and rs366510 (13.8% vs 6.5%) were observed in AD patients as compared with control group. None of the tested polymorphisms showed significant association with the risk of the disease phenotype. Analysis of rs10402876 SNP revealed its association with less severe AD disease expression (low SCORAD). Total serum IgE levels were not different among AD patients having any of the four SNPs. However, we observed significantly less serum-specific IgE levels to common allergens (Dermatophagoides pteronyssinus and birch pollens) and Staphylococcal enterotoxin B in AD patients having rs366510 SNP. Thus, associations of polymorphism within C3 gene with less severe AD disease expression and a weaker sensitization to common allergens suggest the role of these SNPs in the development of AD.

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.

Confirmation of the association between high levels of immunoglobulin E food sensitization and eczema in infancy: an international study

BACKGROUND

Studies of Australian infants have reported that more than 80% of those with moderate atopic eczema (AE) have high levels of IgE food sensitization (IgE-FS) that are commonly associated with IgE food allergy.

OBJECTIVES

To explore the relationship between high levels of IgE-FS and AE in a large cohort of young children with eczema participating in a multi-centre, international study.

METHODS

Two thousand one hundred and eighty-four subjects (mean age 17.6 months, range 11.8-25.4; 1246 males) with active eczema from atopic families from 94 centres in 12 countries were studied. Clinical history, Scoring Atopic Dermatitis index as a measure of eczema severity and CAP-FEIA measurements for total IgE and IgE antibody levels to cow milk, egg and peanut were entered into a database. If CAP-FEIA levels exceeded previously reported age-specific cut-off levels for 95% positive predictive values (PPVs) for food allergy, subjects were defined as having high-risk IgE-FS (HR-IgE-FS).

RESULTS

Serum was available from 2048 patients; 55.5% were atopic. The frequency of HR-IgE-FS to milk, egg and/or peanut was the greatest in patients whose eczema developed in the first 3 months of life and the least in those whose eczema developed after 12 months (P<0.0001). In a regression analysis to allow for potential confounding factors, children with HR-IgE-FS had the most severe eczema and the youngest age of onset (P<0.001); 64% of infants with severe eczema of onset-age <3 months had HR-IgE-FS.

CONCLUSION

Early-onset severe eczema in infancy was associated with HR-IgE-FS. Clinical implications Food allergies should be routinely assessed in infants with moderate or severe eczema. Capsule summary In eczematous infants, the earlier the age of onset, and the greater the severity of eczema, the greater the frequency of associated high levels of IgE-FS.

Temperament and character dimensions in patients with atopic dermatitis

The aim of this study was to assess the personality traits of young male patients with atopic dermatitis (AD), and to examine the correlations between temperament and character dimensions with clinical and other psychological factors. Fifty young adult male AD patients and 83 healthy controls were examined using the temperament and character inventory, the Beck depression inventory and the state-trait anxiety inventory. The AD patients scored higher on harm avoidance and lower on reward dependence, self-directedness and cooperativeness than the healthy controls. The illness duration and anxiety correlated negatively with the self-directedness score, and depression correlated negatively with reward dependence and the persistence scores in AD patients. These results suggest that AD patients have distinctive temperament and character dimensions compared to healthy controls. Moreover, illness duration and anxiety might be associated with some personality problems, and some temperament dimensions (e.g. reward dependence, persistence) may be linked to depressive symptoms in AD patients.

Increased Expression of RANTES, CCR3 and CCR5 in the Lesional Skin of Patients with Atopic Eczema

BACKGROUND

Atopic eczema (AE) is a relapsing inflammatory disease based on IgE sensitization and characterized by peripheral blood eosinophilia and eosinophil infiltration into the lesional skin. In the patch test reaction of AE by allergens, an increased infiltration of activated eosinophils has been demonstrated peaking at 24-48 h. Regulated on activation normal T cell expressed and secreted (RANTES/CCL5) is a chemokine that induces eosinophil migration, and CCR3 and CCR5 are the receptors of RANTES.

OBJECTIVE

In order to further clarify the pathomechanisms of eosinophil infiltration in ongoing chronic inflammation in the skin of patients with AE and its relation to disease severity, we examined the expression of RANTES and its receptors CCR3 and CCR5 in challenged and unchallenged lesional skin of AE.

METHODS

We examined the number of RANTES+ cells, CCR3+ cells, CCR5+cells, activated (EG2+) eosinophils and CD3+ T cells in normal skin of healthy volunteers, and in challenged lesional skin (24 h after mite patch test) as well as unchallenged lesional skin of AE patients by immunohistochemistry. The cellular source of RANTES, CCR3 and CCR5 was analyzed by double immunohistochemistry using specific antibodies to RANTES, CCR3 or CCR5, and antibodies to ECP (EG2) or CD3.

RESULTS

The numbers of RANTES+ cells, CCR3+ cells, CCR5+ cells, EG2+ cells and CD3+ cells were all significantly increased in challenged (mite patch-tested) lesional skin of AE patients as compared to those in unchallenged lesional skin and normal skin. The numbers of these cells in unchallenged lesional skin were greater than those in normal skin. The number of EG2+ cells in the unchallenged lesional skin correlated with both the peripheral blood eosinophil count and the SCORAD index. The number of EG2+ cells in challenged lesional skin correlated with the number of CCR5+ cells. Activated eosinophils and T cells expressed RANTES and various proportions of these cells were CCR3+ and CCR5+ in both challenged and unchallenged lesional skin.

CONCLUSION

Taken together, these results suggest that RANTES as well as its receptors CCR3 and CCR5 may play important roles in the orchestration of eosinophil infiltration in ongoing chronic inflammation in AE, and also reflect the severity of disease.

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.

Atopic dermatitis

Atopic dermatitis (AD) is commonly associated with immunoglobulin E (IgE) antibody-related mechanisms, which are the focus of this article. The vast majority of patients with AD exhibit hyperproduction of IgE, particularly during disease onset or flare. IgE-dependent late-phase reactions may influence the chronic inflammatory response in AD. Clearly, genetics plays a major role in determining who develops AD. However, the recent increase in AD prevalence suggests that a complex interaction between environmental factors and susceptibility genes results in clinical expression of the disorder. These immunologic "triggers" differ among individuals and include various foods, airborne allergens, irritants and contactants, hormones, stress, climate, and microorganisms. Although much about AD remains to be elucidated, our current understanding of its pathophysiology has provided clinicians with the ability to construct more rational therapeutic interventions, including multiple-agent regimens that provide both immediate relief and effective long-term management. Future advances will come from identification of the genes causing this disease and further elucidation of the immunoregulatory mechanisms involved in the pathogenesis of AD.

Interleukin-10 haplotype associated with total serum IgE in atopic dermatitis patients

BACKGROUND

The genetic background of atopic dermatitis (AD) is not clearly understood. Interleukin (IL)-10 is a powerful Th-2 cell cytokine produced by lymphoid cells that exerts its function by inhibiting macrophage/monocyte and T-cell lymphocyte replication and secretion of inflammatory cytokines [IL-1, tumour necrosis factor-alpha (TNFA), IL-6, IL-8 and IL-12].

OBJECTIVE

In an effort to discover additional polymorphism(s) in genes whose variant(s) have been implicated in total immunoglobulin E (IgE) level in AD patients, we scrutinized the single nucleotide polymorphisms (SNPs) in the IL10 gene as a potent candidate for contributing to the level of IgE in serum.

METHODS

We recruited 334 AD patients and assayed their serum total IgE levels using the LIPA-200 system. Four SNPs in the IL10 gene were genotyped using the single-base extension (SBE) method. Logistic regression analyses were performed with single polymorphisms and haplotypes (ht) to determine their association with the level of serum total IgE.

RESULTS

Genetic association analysis of total serum IgE in AD patients revealed that one of the IL10 ht, IL10-ht2, was associated with decreased serum total IgE in gene dose-dependent manner (P = 0.02-0.001).

CONCLUSIONS

It was predicted that the inhibition of innate immunity by increased IL-10 production in IL10-ht2-bearing individuals might be associated with decreased total serum IgE levels among AD patients. The greater effects of IL10 ht on decreased total serum IgE levels suggest that the effect of IL-10 polymorphism might be the result of a combined genotype (ht) rather than single polymorphisms.

Polymorphisms within the PHF11 gene at chromosome 13q14 are associated with childhood atopic dermatitis

Atopic dermatitis is an increasingly common and debilitating childhood disorder that is often accompanied by asthma and allergic rhinitis. Although the pathology of these disorders is distinct, the majority of cases are atopic, typified by elevated serum IgE. A new locus at chromosome 13q14 centred on the genes SETDB2 and PHF11 and associated with increased total serum IgE has recently been identified. Although the precise functions of SETDB2 and PHF11 are not known, both proteins are expressed in cells of the immune system and include conserved domains that suggest a role in chromatin remodelling or transcriptional regulation, respectively. In a family-based association study across the SETDB2 and PHF11 genes, we have identified two single-nucleotide polymorphisms in the PHF11 gene significantly associated with childhood atopic dermatitis in an Australian cohort. These results provide further evidence that this locus is a novel and important regulator of human atopic disease.

A novel (TG)n(GA)m repeat polymorphism 254 bp downstream of the mast cell chymase (CMA1) gene is associated with atopic asthma and total serum IgE levels

The gene for mast cell chymase (CMA1) is an ideal candidate for investigating genetic predisposition to atopic asthma, as it is an important mediator of inflammation and remodeling in the asthmatic lung. Various studies have examined the association between -1903 G/A polymorphism and allergic phenotypes, but inconsistent results have been obtained. We investigated the association of this SNP and a novel (TG)(n)(GA)(m) repeat polymorphism (accession no. BV210164) 254 bp downstream of the gene with asthma and its associated traits in a case-control study in two independent cohorts recruited from the Indian population. A significant association was observed for the (TG)(n)(GA)(m) repeat with asthma (p<0.05) in both the cohorts. Although no association was observed for the -1903 G/A SNP with asthma, a significant association was observed between the genotypes and serum IgE levels (p=0.003 and 0.0004 for cohort A and B). When haplotypes were compared between patients and controls, the haplotype G_43 was found at higher frequency in controls (p=0.05). Also, on comparing major haplotypes (>5%) with respect to log total serum IgE levels, a significant difference was obtained (p=0.018 and p=0.046 for cohorts A and B). These results suggest that the CMA1 gene contributes to asthma susceptibility and may be involved in regulating IgE levels in atopic asthma.

Recent Highlights in the Pathophysiology of Atopic Eczema

Atopic eczema (AE) belongs to the group of atopic diseases that have become increasingly prevalent over the last decades. The pathophysiology of AE has long remained enigmatic, but much scientific effort has been invested in elucidating the genetic background and the immunological mechanisms underlying AE, leading to a better understanding of this complex disease and to new therapeutic strategies. This review provides an update on the scientific progress that has been achieved in clarifying the pathophysiological mechanisms of AE.

Mast cell chymase is increased in chronic atopic dermatitis but not in psoriasis

Mast cell chymase is a chymotrypsin-like serine proteinase primarily stored in secretory mast cell granules. Mast cell chymase has various effects on angiotensin, metalloproteases, lipoproteins, procollagen, neuropeptides and cytokines. Recent studies have demonstrated that chymase inhibitors inhibit skin inflammation. In this study we sought to determine the role of mast cell chymase in atopic dermatitis (AD) in comparison with its role in psoriasis and normal skin. Skin biopsy specimens were obtained from non-lesional and lesional skin of patients with chronic AD and psoriasis and from normal skin of non-atopic and non-psoriatic controls. The number of mast cells containing chymase was determined by immunohistochemistry using a chymase-specific monoclonal antibody. A significantly (P < 0.05) enhanced number of chymase-positive cells was found in lesional AD skin as compared to normal skin as well as to lesional and non-lesional skin of patients with psoriasis. A significant (P < 0.05) increase in the number of chymase-positive cells was also found in non-lesional AD skin in comparison to psoriasis. An enhanced, albeit not statistically significant difference was noted in non-lesional AD skin as compared to normal skin. In conclusion, these results suggest that mast cell chymase may play an integral part in eliciting and maintaining cutaneous inflammation in AD but not in psoriasis. The increased proteinase activity of mast cell chymase may also be involved in promoting a skin barrier defect in AD, which subsequently enhances the skin's permeability to allergens and microbes and thereby aggravates the eczema.

Polymorphism of the mast cell chymase gene (CMA1) promoter region: lack of association with asthma but association with serum total immunoglobulin E levels in adult atopic dermatitis

BACKGROUND

Mast cell chymase has the potential to be an important mediator of inflammation and remodelling in the asthmatic lung. Previous studies have examined association between promoter polymorphism of the chymase gene (CMA1) and allergic phenotypes but the significance of this polymorphism is unclear. We have examined association of a CMA1 variant in relation to asthma in a large UK Caucasian family cohort.

METHODS

A polymorphism of the CMA1 gene promoter (-1903G/A) was genotyped in 341 asthmatic families and in 184 non-asthmatic adults recruited from the UK PCR-RFLP based genotyping. Association with asthma diagnosis, atopy, specific and total IgE, and atopy and asthma severity was examined.

RESULTS

Case-control studies did not reveal a significant difference in allele frequency between asthmatics and controls. A significant association was found between CMA1 genotypes and total IgE levels in subjects with self-reported eczema that remained significant after correction for multiple testing (median total serum IgE GG 297 kU/L, GA 144 kU/L, AA 48.4 kU/L, Pc=0.0032).

CONCLUSION

These data suggest that CMA1 promoter polymorphism does not contribute to asthma susceptibility or severity but may be involved in regulating IgE levels in patients with eczema.

Canine atopic dermatitis: new targets, new therapies

Atopic dermatitis is a common allergic skin disease of complex etiopathogenesis in both humans and dogs. Immediate-type hypersensitivity to environmental allergens that arises as a result of environmental and genetic factors is a major part of the pathogenesis in most but not all patients. Alterations in epidermal barrier function, priming of cutaneous antigen-presenting cells with IgE, intrinsic keratinocyte defects, and even development of autoimmunity are also factors that contribute to the primary disease. Secondary factors, especially infections with Staphylococcus and yeast organisms, strongly influence the course of this skin disease. The relatively recent understanding of the complexities of atopic dermatitis has resulted in changes in diagnostic and therapeutic strategies for the disease. We now know that the best therapeutic approach is to use combinations of multiple modalities individualized for each patient over the course of his or her lifetime.

Dendritic cells and atopic eczema/dermatitis syndrome

PURPOSE OF REVIEW

The manifestation of atopic eczema/dermatitis syndrome is believed to result from a complex interrelationship of environmental factors, pharmacological abnormalities, skin barrier defects, and immunological phenomena. Although we are only beginning to understand the molecular basis of this disease, much progress has been made in defining key events leading to the manifestation of allergic inflammation. Here, we review recent findings that underscore the importance of dendritic cells as being central to shape these proinflammatory responses.

RECENT FINDINGS

Evidence for a differential regulation of the high affinity receptor for IgE, Fc epsilon RI, on the surface of atopic dendritic cells compared with non-atopic dendritic cells became apparent. In atopic donors, in contrast to non-atopic donors, the intracellular expression of the gamma-chains of Fc epsilon RI is sufficient, thus leading to the assembly with the alpha-chain and surface expression of the receptor. This finding is of considerable interest for an understanding of the pathophysiology of IgE-mediated dendritic cell functions in atopic eczema/dermatitis syndrome. In addition, it has been shown that keratinocytes from the epidermal skin of individuals with atopic eczema/dermatitis syndrome express human thymic stromal lymphopoietin, which activates dendritic cells to attract T helper type 2 cells into the skin. Furthermore, these activated dendritic cells prime naïve T cells into T helper type 2 cells.

SUMMARY

The past few years have seen a remarkable process of refocusing in atopy. Dendritic cells in particular have been at the centre of this process. It has become unequivocally clear that these cells have the power of shaping the allergic response.

High contribution contrast between the genes of eosinophil peroxidase and IL-4 receptor α-chain in Japanese cedar pollinosis

BACKGROUND

Japanese cedar pollinosis is the most common form of hayfever in Japan in spring and has remarkably increased since 1960.

OBJECTIVE

We sought to clarify the candidate genes for cedar pollinosis using a case-control study.

METHODS

After diagnosing 351 subjects on the basis of an intradermal test, nasal provocation test, and questionnaire regarding nasal and conjunctival symptoms, we determined the blood-specific IgE values and genotypes of eosinophil peroxidase (EPO) and interleukin-4 receptor alpha-chain (IL4RA) in 145 patients with pollinosis and 206 healthy subjects, including 75 healthy subjects with higher specific IgE values.

RESULTS

We found significant differences in the frequencies of Pro358Leu in EPO and of Ile50Val and Glu375Ala in IL4RA between patients and healthy subjects. There was a significantly higher frequency of 358Leu in EPO in patients than in healthy subjects showing a higher specific IgE value. In contrast, we recognized significant changes in the prevalence of Ile50Val and Glu375Ala in IL4RA in healthy subjects with a normal IgE value compared with those in healthy subjects with a higher specific IgE value. The relationship between EPO polymorphisms and the onset of symptoms was exactly opposite that for IL4RA.

CONCLUSIONS

These results suggest that Pro358Leu in EPO is strongly involved in the development of cedar pollinosis. Ile50Val and Glu375Ala in IL4RA seem to be related to cedar pollen sensitization. Subjects with Ile50 or Glu375 might develop cedar pollinosis with increased exposure to cedar pollen.

Association between novel GM-CSF gene polymorphisms and the frequency and severity of atopic dermatitis

BACKGROUND

Genetic factors are known to be important in determining an individual's predisposition to atopic dermatitis. The specific genes that are clinically important in this process are still largely unknown.

OBJECTIVE

Because dendritic cells initiate immune responses and thus are critical to the priming of an individual to potential allergens, we hypothesized that genetic factors controlling the activity of these cells determine an individual's propensity to atopic dermatitis.

METHODS

We studied known functional polymorphisms of the IL-1beta and TNF-alpha genes and describe novel polymorphisms of the GM-CSF gene in 113 children with atopic dermatitis and 114 controls. All 3 factors are known to be important modulators of the function of skin Langerhans' (dendritic) cells.

RESULTS

The inheritance of a homozygous GM-CSF -677*C/C genotype was associated with complete absence of severe atopic dermatitis within this cohort of children (P <.001). Furthermore, the odds ratio of having atopic dermatitis in children who were not of this genotype was 7.5 (2.2-25).

CONCLUSION

The GM-CSF genotype is an important genetic marker predicting an individual's predisposition to atopic dermatitis.

Immunoregulation in the tissues by gammadelta T cells

For a T-cell subset to be classified as immunoregulatory, it might reasonably be predicted that in its absence, animals would experience pathological immune dysregulation. Moreover, reconstitution of the subset should restore normal immune regulation. So far, these criteria have been satisfied by only a few of the candidate regulatory T-cell subsets, but among them is the intraepithelial gammadelta T-cell receptor (TCR)+ subset of mouse skin. In this article, we look at immunoregulatory gammadelta T cells, and the growing evidence for tissue-associated immunoregulation mediated by both gammadelta T cells and alphabeta T cells.

Atopic dermatitis

Atopic dermatitis is a highly pruritic chronic inflammatory skin disorder affecting 10-20% of children worldwide. Symptoms can persist or begin in adulthood. It is also the most common cause of occupational skin disease in adults. This disease results from an interaction between susceptibility genes, the host's environment, pharmacological abnormalities, skin barrier defects, and immunological factors. New management approaches have evolved from advances in our understanding of the pathobiology of this common skin disorder.

Interleukin-13 gene polymorphism G4257A is associated with atopic dermatitis in Japanese patients

Interleukin (IL)-13 plays an important role in the induction of immunoglobulin E (IgE) and in the pathogenesis of atopic dermatitis (AD). We investigated the allele and genotype frequencies of three IL-13 single nucleotide polymorphisms (SNPs) (A704C and C1103T in the promoter region and G4257A in exon 4) in Japanese patients with AD. For A704C and C1103T SNPs, there were no significant differences in allele or genotype frequencies between AD patients and controls. For G4257A SNP, A allele was significantly increased in AD patients (39.5%) compared with controls (29.4%) (P = 0.016). The same proportion of each genotype and allele was observed in the patient subgroup with and without asthma. Serum IgE levels and peripheral eosinophil counts were not significantly different among genotypes in G4257A SNP. There was also no significant difference in allele or genotype frequencies between AD patients with mild disease and those with severe disease, between those with family history of AD and those without it, or between those with family history of atopic disorders and those without it. This result suggests that 4257A allele is associated with susceptibility to AD and that it may function in the pathogenesis of AD itself, presumably by other mechanisms than inducing IgE production.

Interleukin-12 p40 gene (IL12B) 3'-untranslated region polymorphism is associated with susceptibility to atopic dermatitis and psoriasis vulgaris

Interleukin-12 (IL-12) is believed to play an important role in inducing Th1-type cytokine profiles. Atopic dermatitis (AD) and psoriasis vulgaris (PsV) are considered to be Th2 and Th1 type disease, respectively. The IL-12 p40 subunit gene (IL12B) is located at chromosome 5q31-33 and linkage findings of AD on 5q31 were reported. Recently single nucleotide polymorphism (SNP) (1188A/C) of IL12B has been reported. In function, it has been reported that this SNP is associated with IL12B mRNA expression levels. To learn whether this SNP is associated with susceptibility to AD or PsV, we investigated the genotype and allele frequencies of the SNP in AD patients, in PsV patients and in controls, examining 164 AD patients, 143 PsV patients and 100 healthy individuals in Japanese population. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. The A allele was decreased in AD patients (40.9%, p = 0.031) and increased in PsV patients (60.1%, p = 0.035) compared with controls (50.5%). This suggests that IL12B SNP is associated with susceptibility to AD and PsV, presumably by affecting the Th1/Th2 balance.

Dichotomic nature of atopic dermatitis reflected by combined analysis of monocyte immunophenotyping and single nucleotide polymorphisms of the interleukin-4/interleukin-13 receptor gene: the dichotomy of extrinsic and intrinsic atopic dermatitis

Patients with atopic dermatitis display substantial immunologic abnormalities, among which elevated total IgE is considered as a hallmark; however, a subgroup of atopic dermatitis patients exhibits normal IgE levels, but mechanisms contributing to the so-called "intrinsic" or "nonallergic" form of atopic dermatitis are obscure. In order to unravel similarities and differences of both atopic dermatitis subtypes, the phenotype of monocytes, total serum IgE levels, and serum levels of cytokines regulating the IgE production from nonatopic individuals and patients with allergic rhinitis, and extrinsic and intrinsic atopic dermatitis were measured. Concomitantly, genomic DNA probes of all subjects were analyzed for single nucleotide polymorphisms of candidate genes of structures involved in the regulation of the IgE synthesis, such as interleukin-4 and the interleukin-4R/interleukin-13R. Our data show that the surface expression of the high- and low-affinity receptor for IgE (FcepsilonRI and FcepsilonRII/CD23) and the interleukin-4Ralpha chain were significantly elevated in monocytes from patients with extrinsic atopic dermatitis. Furthermore, serum levels of interleukin-13 were significantly increased in patients with intrinsic atopic dermatitis. In addition, the frequency of the interleukin-4Ralpha polymorphism C3223T and the interleukin-4 polymorphism C590T tended to be higher in extrinsic atopic dermatitis than in intrinsic atopic dermatitis. Altogether our findings indicate that intrinsic atopic dermatitis patients exhibit phenotypic and immunologic features, which differ from those of patients with extrinsic atopic dermatitis or other atopic disorders.

Atopiform dermatitis

It is proposed to introduce the term 'atopiform dermatitis' to describe patients who have dermatitis with many of the characteristics of true atopic dermatitis, but who are not atopic. Atopy should be defined as the genetically determined and environmentally influenced syndrome in which the primary immunological abnormality is the production of allergen-specific IgE. It is suggested that by making a distinction between atopiform dermatitis and true atopic dermatitis, subsequent genetic, immunological and therapeutic studies will be improved. Furthermore, atopiform dermatitis would be a more appropriate diagnosis for the atopic dermatitis-like skin diseases that may occur in syndromes such as phenylketonuria, Schwachman's syndrome, Wiskott-Aldrich syndrome, Netherton's syndrome, Job's syndrome, selective IgA deficiency, agammaglobulinaemia and ataxia telangiectasia. In contrast to patients with true atopy, patients with atopiform dermatitis can logically be advised that allergen avoidance is not required, as they have no allergen-specific IgE.

Eotaxin gene single nucleotide polymorphisms in the promoter and exon regions are not associated with susceptibility to atopic dermatitis, but two of them in the promoter region are associated with serum IgE levels in patients with atopic dermatitis

Eotaxin is believed to play an important role in atopic dermatitis (AD) as a potent chemoattractant and activator of eosinophils and Th2 lymphocytes. The eotaxin gene is located at chromosome 17q21.1-q21.2, and linkage findings of AD on chromosome 17 were reported. Recently we have identified single nucleotide polymorphisms (SNPs) of eotaxin gene (-426C > T, -384A > G, 67G > A). To learn whether eotaxin gene SNPs are associated with susceptibility to AD or phenotypes of AD, we investigated the genotype frequencies at each SNP of the gene in AD patients and in controls. We examined 140 Japanese AD patients and 140 healthy Japanese individuals. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. No significant difference was observed in allele or genotype frequencies of any SNP between AD patients and controls. Serum immunoglobulin E (IgE) levels were significantly lower in CT and TT genotype than in CC (P = 0.038) in -426C > T SNP, and lower in GG than in AA and AG with borderline significance (P = 0.053) in -384A > G SNP in AD patients. Eotaxin gene SNPs in the promoter and exon regions are not associated with susceptibility to AD, but two of them in the promoter region are associated with phenotype of AD.

Asthma and atopy - a total genome scan for susceptibility genes

BACKGROUND

Allergic asthma is an increasingly common disease of complex inheritance. Several studies have suggested candidate regions, but genetic heterogeneity, ethnic differences and varying study designs may in part explain the lack of identified and confirmed susceptibility genes. Investigation of different populations will further clarify the topic. We therefore evaluated allergic asthma and increased total and specific IgE in 39, 45 and 57 sib-pairs from 100 Danish allergy families.

METHODS

Affected sib-pairs meeting a narrow phenotype definition were selected for the three phenotypes atopy, allergic asthma and increased total IgE. We performed a total genome scan using 446 microsatellite markers and obtained nonparametric linkage results from the MAPMAKER/SIBS computer program.

RESULTS

Our study revealed four candidate regions (MLS > 2) on chromosome 1p36, 3q21-q22, 5q31 and 6p24-p22, and 15 candidate regions (1 < MLS < 2) that may contain susceptibility genes for asthma and atopy. We did not find linkage to the candidate genes TNF-beta, FcER1beta and Il4R-alpha, except for weak support for linkage of the asthma phenotype to TNF-beta (MLS = 1.18).

CONCLUSIONS

We found evidence for two new asthma and atopy loci, 1p36 and 3q21-q22, and supported linkage in the Danish population to seven previously reported candidate regions.

Asthma and IL-4 receptor alpha gene variants

Linkage of allergy to chromosome 16 has been described in several studies, together with a positive association with interleukin 4 receptor alpha gene variants. Our aim was to replicate these findings in a sample of German and Swedish families recruited through sib-pairs affected by bronchial asthma. None of the markers showed linkage with the main phenotype of asthma or with total serum IgE. Seropositivity to D. pteronyssinus showed borderline significance in a region flanking the IL4Ralpha location. Single nucleotide polymorphisms (SNPs) leading to the protein exchanges I50V, E375A, C406R, S478P and Q551R in the IL-4 receptor alpha were examined for allele sharing in sibs with asthma. Multiple regression analysis was performed for association with total serum IgE and specific IgE. Allele sharing of IL4Ralpha SNPs in asthmatic children was not significantly increased for any of the examined SNPs except for the intracytoplasmatic polymorphism 551R (0.79 vs. 0.84 expected, P = 0.044). The variants 50V, 478P and 551R were associated with slightly increased, and 375A and 406R with decreased total IgE levels, all at a non-significant level. None of the examined IL4Ralpha variants were correlated to asthma severity. In summary, a single gene effect of IL4Ralpha variants or any other gene on chromosome 16 could not be shown in this selected population of children with asthma. As there could be interactions with multiple genetic and environmental factors, IL4Ralpha could still be involved in asthma pathogenesis.

Resident skin-specific gammadelta T cells provide local, nonredundant regulation of cutaneous inflammation

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) gammadelta(+) (Vgamma5(+)) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in gammadelta T cells (delta(-/-) mice), and in delta(-/-) mice reconstituted with DETC or with different gammadelta cell subpopulations. NOD.delta(-/-) and FVB.delta(-/-) mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.delta(-/-) strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.delta(-/-) mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.delta(-/-), but not in C57BL/6.delta(-/-) mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.beta(-/-) delta(-/-) mice lacking all T cells, indicating that alphabeta T cell-mediated inflammation is the target for gammadelta-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.delta(-/-) mice were down-regulated by Vgamma5(+) DETC, but not by epidermal T cells expressing other gammadelta TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-gammadelta(+) IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs.

Interactions between genes and environmental factors in asthma and atopy: new developments

Asthma and associated phenotypes are complex traits most probably caused by an interaction of multiple disease susceptibility genes and environmental factors. Major achievements have occurred in identifying chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma, atopic dermatitis, IgE levels and response to asthma therapy. The aims of this review are to explain the methodology of genetic studies of multifactorial diseases, to summarize chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma and associated traits, to list genetic alterations that may alter response to asthma therapy, and to outline genetic factors that may render individuals more susceptible to asthma and atopy due to environmental changes.