The immunogenetics of asthma and eczema: a new focus on the epithelium

ADAM10-mediated E-cadherin release is regulated by proinflammatory cytokines and modulates keratinocyte cohesion in eczematous dermatitis

Acute eczema is an inflammatory skin disease characterized by the formation of small intraepidermal blisters, reduction of the adhesion molecule E-cadherin from the keratinocyte surface, and impaired keratinocyte cohesion. Here, we reveal that the disintegrin and metalloprotease ADAM10 is critically involved in regulating E-cadherin cell-surface expression in cultured primary human keratinocytes and in diseased human skin. Proinflammatory cytokines, transforming growth factor-beta, and lipopolysaccharide led to increased release of soluble E-cadherin by activating mitogen-activated protein kinase signaling in cultured keratinocytes. Moreover, these stimuli decreased the amount of pro-ADAM10 and increased the level of the active protease, leading to loss of E-cadherin from the cell surface and decreased keratinocyte cohesion. In situ examination and immunoblot analyses of E-cadherin and ADAM10 expression in lesional skin of eczema revealed that the reduction of E-cadherin expression in areas of blister formation closely correlated with increased level of ADAM10 expression and elevated E-cadherin shedding. Our data suggest that ADAM10-mediated E-cadherin proteolysis leads to the impaired cohesion of keratinocytes observed in eczematous dermatitis and provide previously unreported insights into the understanding of the molecular mechanisms involved in inflammatory diseases with loss in epithelial integrity.

The role of emollients in the management of diseases with chronic dry skin

Dry skin is a common skin condition as well as a key aspect of a number of diseases such as atopic dermatitis and psoriasis but also of other diseases and systemic conditions. Dry skin has an impact on the patient in terms of discomfort, pruritus and impaired quality of life. Within the overall treatment regimen for these diseases, the use of emollients to manage dry skin plays a considerable role in managing skin conditions. In atopic dermatitis and psoriasis, emollients help to improve skin condition and to reduce pruritus alongside more potent pharmacological agents. It is important to choose an emollient that not only soothes and rehydrates the skin but also offers numerous other dermatological supporting roles, especially induction of proper epidermal differentiation. This review will explain the role of emollients within the management of diseases with dry skin as a major symptom and the components of an ideal emollient.

Immunology and treatment of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory disease hypothesized to be the product of complex interactions among the host's environment, susceptibility genes, skin barrier dysfunction, and immune system dysregulation. The objective of this article is to describe the pathobiology and treatment of AD, with particular focus on the role of immune system dysregulation and therapies designed to target this. Literature review indicates that there are immunologic differences between the lesional and non-lesional skin of atopic individuals, and that the non-lesional skin of atopic individuals presents an immunologic profile distinct from that of the skin of healthy individuals. Thus, immune system dysregulation is postulated to be a key contributing factor to the complex etiology of AD. Immunomodulatory agents such as topical corticosteroids (TCSs) and topical calcineurin inhibitors (TCIs), which address the underlying immunopathology of AD, are the foundation for the pharmacologic treatment of flares. TCSs and TCIs both target the inflammatory response responsible for an AD flare but via two distinct mechanisms of action. Whereas TCSs have a more widespread impact on the immune system, the action of TCIs is targeted to the calcineurin pathway and inhibition of T-cell activation. Together, TCSs and TCIs represent the backbone of a long-term treatment strategy for AD.

Variants in a novel epidermal collagen gene (COL29A1) are associated with atopic dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disorder and a major manifestation of allergic disease. AD typically presents in early childhood often preceding the onset of an allergic airway disease, such as asthma or hay fever. We previously mapped a susceptibility locus for AD on Chromosome 3q21. To identify the underlying disease gene, we used a dense map of microsatellite markers and single nucleotide polymorphisms, and we detected association with AD. In concordance with the linkage results, we found a maternal transmission pattern. Furthermore, we demonstrated that the same families contribute to linkage and association. We replicated the association and the maternal effect in a large independent family cohort. A common haplotype showed strong association with AD (p = 0.000059). The associated region contained a single gene, COL29A1, which encodes a novel epidermal collagen. COL29A1 shows a specific gene expression pattern with the highest transcript levels in skin, lung, and the gastrointestinal tract, which are the major sites of allergic disease manifestation. Lack of COL29A1 expression in the outer epidermis of AD patients points to a role of collagen XXIX in epidermal integrity and function, the breakdown of which is a clinical hallmark of AD.

Atopic dermatitis (AD, eczema) is a common chronic inflammatory skin disorder and a major manifestation of allergic disease. Typically, AD first occurs in early childhood, often preceding the onset of allergic airways disease, such as asthma and hay fever. A family history of allergic disorders is the single strongest predictor for AD, showing that genetic factors play a major role in the disease development. We have previously mapped a disease locus for AD on Chromosome 3q21, Now we have used a dense map of microsatellite markers and single nucleotide polymorphisms (SNPs) to find the underlying disease gene. We identified genetic markers in a subregion that showed association with AD, and replicated this finding in a large independent family cohort. The associated region contained a single gene, COL29A1, which encodes a novel collagen. We demonstrate that AD patients lack COL29A1 expression in the outer epidermis, implicating collagen XXIX in epidermal integrity and function. The gene expression pattern of COL29A1 in other organs, including the lung and the gut, suggests that this gene could have a role in a wider spectrum of allergic diseases and may provide a molecular link between AD and respiratory airways disease and food allergies.

The gene underlying atopic dermatitis susceptibility has been identified by gene mapping as expressing a novel collagen, whose expression is lacking in the outer epidermis of atopic dermatitis patients.

Airway remodeling in asthma

Airway remodeling can be defined as changes in the composition, content, and organization of the cellular and molecular constituents of the airway wall. Airway remodeling is a characteristic feature of asthma, and has important functional implications. These structural changes include epithelial detachment, subepithelial fibrosis, increased airway smooth muscle (ASM) mass, decreased distance between epithelium and ASM cells, goblet cell hyperplasia, mucus gland hyperplasia, proliferation of blood vessels and airway edema and changes in the cartilage. Each can contribute to airway hyperreactivity (AHR), and may eventually lead to irreversible airflow obstruction with disease progression. Structural changes can be observed from early onset of the disease and thus remodeling is thought to be characteristic of asthma. Some aspects of airway remodeling can be explained as a consequence of TH2 inflammation, although it has also been suggested that the exaggerated inflammation and remodeling seen in asthmatic airways is the consequence of abnormal injury and repair responses stemming from the susceptibility of bronchial epithelia to components of the inhaled environment. According to this view, remodeling occurs by way of a noninflammatory mechanism, where inflammation of airways and altered structure and function of the airways are parallel and interacting factors. Airway remodeling in established asthma is poorly responsive to current therapies, such as inhalation of corticosteroids and administration of beta(2)-agonists, antileukotrienes, and theophylline.

Epithelium: at the interface of innate and adaptive immune responses

Several diseases of the airways have a strong component of allergic inflammation in their cause, including allergic rhinitis, asthma, polypoid chronic rhinosinusitis, eosinophilic bronchitis, and others. Although the roles played by antigens and pathogens vary, these diseases have in common a pathology that includes marked activation of epithelial cells in the upper airways, the lower airways, or both. Substantial new evidence indicates an important role of epithelial cells as both mediators and regulators of innate immune responses and adaptive immune responses, as well as the transition from innate immunity to adaptive immunity. The purpose of this review is to discuss recent studies that bear on the molecular and cellular mechanisms by which epithelial cells help to shape the responses of dendritic cells, T cells, and B cells and inflammatory cell recruitment in the context of human disease. Evidence will be discussed that suggests that secreted products of epithelial cells and molecules expressed on their cell surfaces can profoundly influence both immunity and inflammation in the airways.

Genome-wide profiling identifies epithelial cell genes associated with asthma and with treatment response to corticosteroids

Airway inflammation and epithelial remodeling are two key features of asthma. IL-13 and other cytokines produced during T helper type 2 cell-driven allergic inflammation contribute to airway epithelial goblet cell metaplasia and may alter epithelial-mesenchymal signaling, leading to increased subepithelial fibrosis or hyperplasia of smooth muscle. The beneficial effects of corticosteroids in asthma could relate to their ability to directly or indirectly decrease epithelial cell activation by inflammatory cells and cytokines. To identify markers of epithelial cell dysfunction and the effects of corticosteroids on epithelial cells in asthma, we studied airway epithelial cells collected from asthmatic subjects enrolled in a randomized controlled trial of inhaled corticosteroids, from healthy subjects and from smokers (disease control). By using gene expression microarrays, we found that chloride channel, calcium-activated, family member 1 (CLCA1), periostin, and serine peptidase inhibitor, clade B (ovalbumin), member 2 (serpinB2) were up-regulated in asthma but not in smokers. Corticosteroid treatment down-regulated expression of these three genes and markedly up-regulated expression of FK506-binding protein 51 (FKBP51). Whereas high baseline expression of CLCA1, periostin, and serpinB2 was associated with a good clinical response to corticosteroids, high expression of FKBP51 was associated with a poor response. By using airway epithelial cells in culture, we found that IL-13 increased expression of CLCA1, periostin, and serpinB2, an effect that was suppressed by corticosteroids. Corticosteroids also induced expression of FKBP51. Taken together, our findings show that airway epithelial cells in asthma have a distinct activation profile and identify direct and cell-autonomous effects of corticosteroid treatment on airway epithelial cells that relate to treatment responses and can now be the focus of specific mechanistic studies.

Differentiation potential of a basal epithelial cell line established from human bronchial explant

Due to the cellular complexity of the airway epithelium, it is important to carefully define bronchial cell lines that capture the phenotypic traits of a particular cell type. We describe the characterization of a human bronchial epithelial cell line, VA10. It was established by transfection of primary bronchial epithelial cells with retroviral constructs containing the E6 and E7 oncogenes from HPV16. The cell line has been cultured for over 2 yr, a total of 60 passages. Although prolonged culture resulted in increased chromosomal instability, no major phenotypic drift in marker expression was observed. The cells expressed cytokeratins 5, 13, 14, and 17 suggesting a basal-like phenotype. This was further supported by the expression of alpha6beta4 integrins and the basal cell-associated transcription factor p63. The VA10 cell line generated high transepithelial electrical resistance in suspended and air-liquid interface culture, indicating functionally active tight junction (TJ) complexes. Immunocytochemistry showed the typical reticular structures of occludin and TJ-associated F-actin. VA10 produced pseudostratified layer in air-liquid interface culture with expression of p63 restricted to the basal layer. Furthermore, VA10 produced round colonies when cultured in laminin-rich reconstituted basement membrane, and immunostaining of claudin-1 and the basolateral marker beta4 integrin revealed colonies that generated polarization as expected in vivo. These data indicate that VA10 epithelia have the potential to model the bronchial epithelium in vivo and may be useful to study epithelial regeneration and repair and the effect of chemicals and potential drug candidates on TJ molecules in airway epithelia.

Risk of developing asthma in young children with atopic eczema: a systematic review

BACKGROUND

It is commonly believed that the majority of infants and young children with early atopic eczema will develop asthma in later childhood. This belief is mainly based on cross-sectional population studies. Recent evidence suggests a more complex relationship between early eczema and asthma.

OBJECTIVE

This systematic review was conducted to assess the risk of developing asthma in children with atopic eczema during the first 4 years of life.

METHODS

A sensitive search was performed to identify all prospective cohort studies on the topic. By pooling the eligible reports, we calculated the risk of developing asthma at 6 years of age or older in children with atopic eczema in the first 4 years of life.

RESULTS

Thirteen prospective cohort studies were included, with 4 representing birth cohort studies and 9 representing eczema cohort studies. The pooled odds ratio for the risk of asthma after eczema, compared with children without eczema, in birth cohort studies was 2.14 (95% CI, 1.67-2.75). The prevalence of asthma at the age of 6 years in eczema cohort studies was 35.8% (95% CI, 32.2% to 39.9%) for inpatients and 29.5% (95% CI, 28.2% to 32.7%) for a combined group of inpatients and outpatients.

CONCLUSION

Although there is an increased risk of developing asthma after eczema in early childhood, only 1 in every 3 children with eczema develops asthma during later childhood. This is lower than previously assumed.

CLINICAL IMPLICATIONS

Our results may have important consequences for counseling patients with atopic eczema and their parents.

Neuropeptide s receptor 1 gene polymorphism is associated with susceptibility to inflammatory bowel disease

BACKGROUND & AIMS

The neuropeptide S receptor (NPSR1) gene has been associated recently with asthma and maps in a region of chromosome 7 previously linked also to inflammatory bowel disease (IBD). NPSR1 is expressed on the epithelia of several organs including the intestine, and appears to be up-regulated in inflammation. We tested NPSR1 gene polymorphism for association with IBD and verified whether the expression of its 2 major isoforms (NPSR1-A and NPSR1-B) is altered in the intestine of IBD patients.

METHODS

Eight NPSR1 polymorphisms were genotyped in 2490 subjects from 3 cohorts of IBD patients and controls from Italy, Sweden, and Finland. Real-time polymerase chain reaction and immunohistochemistry were used to quantify NPSR1 messenger RNA (mRNA) and protein expression in intestinal biopsy specimens from IBD patients and controls.

RESULTS

Global analysis of the whole dataset identified strong association of a NPSR1 haplotype block with IBD (P = .0018) and its 2 major forms: Crohn's disease (CD) (P = .026) and ulcerative colitis (UC) (P = .003). Genetic effects caused by individual haplotypes were identified mainly for the predisposing haplotype H2 in CD (P = .0005) and the protective haplotype H8 in UC (P = .003). NPSR1 mRNA and protein levels were increased in IBD patients compared with controls, and the risk haplotype H2 correlated with higher expression of both NPSR1-A (P = .024) and NPSR1-B (P = .047) mRNAs.

CONCLUSIONS

NPSR1 polymorphism is associated with IBD susceptibility. Specific NPSR1 alleles might act as genetic risk factors for chronic inflammatory diseases of the epithelial barrier organs.

The prevalence of atopic triad in children with physician-confirmed atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is often associated with comorbidities such as allergic rhinitis and asthma.

OBJECTIVE

We sought to describe the frequency of these comorbidities in children with AD.

METHODS

We conducted a cross-sectional study of the first 2270 children with physician-confirmed AD enrolled in a large postmarketing cohort. All were queried for information on comorbidities using a questionnaire from the International Study of Asthma and Allergies in Childhood.

RESULTS

In all, 71.3% reported at least one additional form of atopy (symptoms of asthma or allergic rhinitis). A total of 33.3% reported only symptoms of asthma or allergic rhinitis whereas 38.0% reported symptoms of asthma and allergic rhinitis. By age 3 years, nearly 66% reported at least one additional form of atopy. A statistically significant trend toward poorer disease control was observed for those with additional atopic illnesses (P < .001).

LIMITATIONS

This is a cross-sectional study.

CONCLUSION

Individuals with AD exhibit a predisposition to additional atopic illnesses by age 3 years and in turn the presence of these illnesses correlates with poor disease control.

Genetic variants regulating ORMDL3 expression contribute to the risk of childhood asthma

Asthma is caused by a combination of poorly understood genetic and environmental factors. We have systematically mapped the effects of single nucleotide polymorphisms (SNPs) on the presence of childhood onset asthma by genome-wide association. We characterized more than 317,000 SNPs in DNA from 994 patients with childhood onset asthma and 1,243 non-asthmatics, using family and case-referent panels. Here we show multiple markers on chromosome 17q21 to be strongly and reproducibly associated with childhood onset asthma in family and case-referent panels with a combined P value of P < 10(-12). In independent replication studies the 17q21 locus showed strong association with diagnosis of childhood asthma in 2,320 subjects from a cohort of German children (P = 0.0003) and in 3,301 subjects from the British 1958 Birth Cohort (P = 0.0005). We systematically evaluated the relationships between markers of the 17q21 locus and transcript levels of genes in Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines from children in the asthma family panel used in our association study. The SNPs associated with childhood asthma were consistently and strongly associated (P < 10(-22)) in cis with transcript levels of ORMDL3, a member of a gene family that encodes transmembrane proteins anchored in the endoplasmic reticulum. The results indicate that genetic variants regulating ORMDL3 expression are determinants of susceptibility to childhood asthma.

The skin barrier, atopic dermatitis and allergy: a role for Langerhans cells?

The skin barrier (stratum corneum) is a major factor for determining the nature of immune response to antigens presented at the skin surface. Genetic abnormalities in skin barrier function are associated with allergy and atopic dermatitis, and removal of the skin barrier by tape stripping results in dominant Th2 responses to protein antigens. Langerhans cells take up antigen applied to skin from which the skin barrier has been removed; they then migrate to draining lymph nodes and initiate typical Th2 responses. These observations lead us to propose that the high frequency of allergic disease in the industrialized world might be due to lifestyle choices that result in loss of integrity of the skin barrier such as excessive washing and exfoliation of the skin.

On the role of the epidermal differentiation complex in ichthyosis vulgaris, atopic dermatitis and psoriasis

Undisturbed epidermal differentiation is crucial for an intact skin barrier function. The epidermal differentiation complex (EDC) is a cluster of genes on chromosome 1q21 encoding proteins that fulfil important functions in terminal differentiation in the human epidermis, including filaggrin, loricrin, S100 proteins and others. Recently, evidence emerged that variation within EDC genes plays an important role in the pathogenesis of three common skin disorders, ichthyosis vulgaris, atopic dermatitis (AD) and psoriasis. Two loss-of-function mutations in the filaggrin (FLG) gene, R501X and 2282del4, were identified as causative for ichthyosis vulgaris in 15 affected European families, and the mode of inheritance was found to be semidominant. As ichthyosis vulgaris and AD often occur concomitantly in affected individuals, these two mutations were subsequently investigated in AD patients and found to be strongly associated with the disease. Following this first report, seven replication studies have been performed that all confirm an association of these two mutations with AD (or AD subtypes) in several European cohorts. Additionally, two unique loss-of-function mutations in the FLG gene were identified in Japanese ichthyosis vulgaris families and found to be associated with AD in a Japanese cohort. Thus, the FLG mutations are among the most consistently replicated associations for AD. Additionally, linkage analysis has suggested that variation within the EDC might also predispose for psoriasis but the exact susceptibility variation(s) have not yet been elucidated. Taken together, these findings convincingly demonstrate the important role of barrier dysfunction in various common skin disorders.

Calcium Channel Blocker Prevents T Helper Type 2 Cell–mediated Airway Inflammation

RATIONALE

Ca(2+) signaling controls the production of T helper (Th) type 2 cytokines known to be deleterious in asthma. Recently, we showed that Ca(2+) signaling was dihydropyridine (DHP)-sensitive in Th2 lymphocytes and that the DHP derivate, nicardipine, used in the treatment of cardiovascular pathologies, prevents Th2-dependent B cell polyclonal activation.

OBJECTIVES

We tested the effect of nicardipine in experimental allergic asthma.

METHODS

BALB/c mice immunized with ovalbumin (OVA) in alum and challenged with intranasal OVA were treated with nicardipine once the Th2 response, or even airway inflammation, was induced. We also tested the effect of nicardipine in asthma induced by transferring OVA-specific Th2 cells in BALB/c mice exposed to intranasal OVA. We checked the impact of nicardipine on T-cell responses and airway inflammation.

MEASUREMENTS AND MAIN RESULTS

Nicardipine inhibited in vitro Ca(2+) response in Th2 cells. In vivo, it impeded the development of Th2-mediated airway inflammation and reduced the capacity of lymphocytes from lung-draining lymph nodes to secrete Th2, but not Th1, cytokines. Nicardipine did not affect antigen presentation to CD4(+) T lymphocytes, nor the initial localization of Th2 cells into the lungs of mice exposed to intranasal OVA; however, it reduced the production of type 2 cytokines and the amplification of the Th2 response in mice with asthma. Conversely, nicardipine had no effect on Th1-mediated airway inflammation.

CONCLUSIONS

Nicardipine improves experimental asthma by impairing Th2-dependent inflammation. This study could provide a rationale for developing drugs selectively targeting DHP receptors of Th2 lymphocytes, potentially beneficial in the treatment of asthma.

The role of innate immunity in asthma: leads and lessons from mouse models

According to the Hygiene Hypothesis, respiratory infections should protect individuals from allergic diseases including asthma, but epidemiologic data on the role of infections or exposure to microbial compounds in asthma are contradictory. Meanwhile, a number of murine models of airway sensitization are available facilitating the elucidation of pathways involved in asthma pathogenesis. Such studies have linked antigen presentation by activated pulmonary dendritic cells (DCs) with airway sensitization. Toll-like receptors (TLRs), which play a major role in innate immunity by sensing various microbial compounds, are expressed on DCs, as well as on mast cells (MCs). Activation of TLRs by administration of specific bacterial ligands, in particular lipopolysaccharide, can augment airway sensitization in mice, and there is evidence that this process involves TLR-dependent activation of DCs. Intriguingly, viral infection has been shown to increase airway inflammation in a murine asthma model via activation of DCs as well. TLR-4-dependent stimulation of MCs may also play a role in allergic sensitization in mice, and in vitro studies in murine cells show that ligation of TLRs expressed on MCs enhances degranulation. Therefore, evidence obtained from studies on mice indicates that innate immune responses may promote, rather than protect from, the development as well as the exacerbation of asthma.

Detection of down-regulated acetaldehyde dehydrogenase 1 in atopic dermatitis patients by two-dimensional electrophoresis

We conducted the proteomic studies to detect the dysregulated proteins in the atopic dermatitis (AD) proteome obtained from the patient-derived primary cultured fibroblasts. Acetaldehyde dehydrogenase 1 (ALDH1) was detected as being significantly down-regulated at the pH ranges of 6-9 and 4-7. The transcriptional levels of ALDH1, as detected by RT-PCR and real-time PCR, further confirmed the down-regulated phenomena for all the AD-fibroblasts (n = 20). The expression levels of ALDH1 in the whole skin tissue samples were further supported by the results of the primary cultured samples. These findings clearly demonstrate that ALDH1 can be a dermal biomarker for AD disease.

Epidemiological and immunological evidence for the hygiene hypothesis

Allergic diseases are inflammatory disorders that develop on the basis of complex gene-environment interactions. The prevalence of allergies is steadily increasing and seems to be associated with modern lifestyle. Therefore, it was hypothesized that high living standards and hygienic conditions are correlated with an increased risk for the development of an allergic disease. This so-called "hygiene hypothesis" states that due to reduced exposure to microbial components, the proposed allergy-preventing potential of these factors is no more present in sufficient qualities and/or quantities, which leads to an imbalance of the immune system with a predisposition to the development of allergic disorders. Meanwhile, several epidemiological studies were conducted supporting this concept and generating novel ideas for the underlying mechanisms that were then followed up by use of well-defined animal models and human studies. The current view of cellular and molecular mechanisms responsible for these phenomena includes changes in the fine balancing of T helper cell 1 (Th1), Th2 and regulatory T cell (Treg) responses which are triggered by altered or missing innate immune cell activation. In fact, proper activation of cells of the innate immune system via their so-called pattern recognition receptors has been demonstrated to play a crucial role in early shaping of the immune system and suppression of the development of Th2-driven allergic immune responses. These processes start already in utero and prenatal as well as early postnatal developmental stages seem to represent a certain "window of opportunity" for allergy-preventing environmental influences.

The epithelium takes centre stage in asthma and atopic dermatitis

Asthma and atopic dermatitis are epithelial disorders in which T helper 2 (Th2)-type inflammation has a prominent role. Thymic stromal lymphopoietin (TSLP) is a cytokine produced by the skin and airway epithelium that is capable of directing dendritic cells towards a Th2 response, thereby providing an essential link between epithelial cell activation and allergic-type inflammation. In addition, TSLP can interact directly with mast cells to initiate Th2 cytokine production to also provide a non-T cell route to mediate its pro-allergic effects. Induction of TSLP production occurs through the activation of epithelial Toll-like receptors to provide an important new link between innate immunity and allergic disease.

Bacterial superantigen facilitates epithelial presentation of allergen to T helper 2 cells

Although clinical and laboratory evidence support roles for both staphylococcal infection and environmental allergens in the pathogenesis of atopic dermatitis, human studies have largely considered these variables independently. We sought to test the hypothesis that staphylococcal superantigen influences the allergen-specific T cell response. We first mapped a Der p 1 epitope and used HLA DRB1*1501 class II tetramer-based cell sorted populations to show that specific CD4(+) T cells were able to recognize the peptide presented by HLA DR-matched keratinocytes. We observed that staphylococcal enterotoxin B (SEB) enhanced the IL-4 Der p 1-specific T cell response. This response was mediated by two synergistic mechanisms: first, SEB-induced IFN-gamma promoted class II and intercellular adhesion molecule-1 expression by presenting keratinocytes; and second, SEB-induced IL-4 directly amplified allergen-specific CD4(+) T cell production of many cytokines. We propose that handling of staphylococcal infection is a critical step in the amplification of the allergen-specific T cell response, linking two common disease associations and with implications for the prevention and treatment of atopic disease.

Early cutaneous gene transcription changes in adult atopic dermatitis and potential clinical implications

Atopic dermatitis (AD) is a common pruritic dermatitis with macroscopically non-lesional skin that is often abnormal. Therefore, we used high-density oligonucleotide arrays to identify cutaneous gene transcription changes associated with early AD inflammation as potential disease control targets. Skin biopsy specimens analysed included normal skin from five healthy non-atopic adults and both minimally lesional skin and nearby or contralateral non-lesional skin from six adult AD patients. Data were analysed on an individual gene basis and to identify biologically relevant gene networks. Transcription levels of selected genes were also analysed by quantitative PCR. Differential transcription occurring early in AD skin was indicated for (i) individual genes such as C-C chemokine ligand (CCL)18, CCL13, and interferon-alpha2 (IFNalpha2), (ii) genes associated with peroxisome proliferator-activated receptor (PPAR)alpha- and PPARgamma-regulated transcription, and possibly for (iii) immunoglobulin J-chain and heavy chain isotype transcripts. These data suggest that local changes in immunoglobulin-associated transcription may favour IgE over secretory immunoglobulin (multimeric IgM and IgA) expression in AD skin. Decreased PPAR activity appears common to both AD and psoriasis, and reduced cutaneous IFNalpha2 transcription also appears characteristic of AD. Identification of these genes and pathways will direct future research towards controlling AD.

Filaggrin mutations in children with severe atopic dermatitis

Atopic dermatitis (AD) results from strong genetic and environmental interactions. AD shows genetic linkage to Chromosome 1q21. This region contains the epidermal differentiation complex (EDC), which consists of genes that form essential components of epidermal surfaces. Filaggrin (FLG) is one of these. Mutations in FLG/(R501X and 2282del4) are reported to be strongly associated with AD and to influence asthma accompanying AD. We investigated these effects in families recruited through a child with severe AD. We genotyped two panels of families, totalling 426, containing 990 affected and unaffected children. We found significant associations with AD (P=0.0001), asthma (P=0.006), and atopy (P=0.002). The FLG mutations were present in 26.7% of patients with AD, but were also present in 14.4% of children without AD. They were weakly associated with disease severity. The variants were not independently associated with asthma. The overall LOD score for genetic linkage of markers to the region was 3.57. This fell to 2.03 after accounting for the FLG mutations, indicating the presence of other genetic variants influencing AD at this locus. Our results provide further confirmation of the importance of mutations in FLG and the skin barrier in AD pathogenesis. The results indicate that investigations of other genes within the EDC should be undertaken.

Exploring host-pathogen interactions at the epithelial surface: application of transcriptomics in lung biology

The epithelial surface of the airways is the largest barrier-forming interface between the human body and the outside world. It is now well recognized that, at this strategic position, airway epithelial cells play an eminent role in host defense by recognizing and responding to microbial exposure. Conversely, inhaled microorganisms also respond to contact with epithelial cells. Our understanding of this cross talk is limited, requiring sophisticated experimental approaches to analyze these complex interactions. High-throughput technologies, such as DNA microarray analysis and serial analysis of gene expression (SAGE), have been developed to screen for gene expression levels at large scale within single experiments. Since their introduction, these hypothesis-generating technologies have been widely used in diverse areas such as oncology and brain research. Successful application of these genomics-based technologies has also revealed novel insights in host-pathogen interactions in both the host and pathogen. This review aims to provide an overview of the SAGE and microarray technology illustrated by their application in the analysis of host-pathogen interactions. In particular, the interactions between epithelial cells in the human lungs and clinically relevant microorganisms are the central focus of this review.

Skin barrier function in atopic dermatitis

PURPOSE OF REVIEW

Whereas much investigation in atopic dermatitis has focused upon the adaptive immune response, new data suggest that allergic sensitization may occur secondary to impairment of skin barrier function.

RECENT FINDINGS

Two common loss-of-function mutations in the FLG gene encoding filaggrin (an important component of terminal keratinocyte differentiation) are strongly associated with the development of atopic dermatitis and asthma associated with atopic dermatitis.

SUMMARY

Genetic defects in skin barrier function should be recognized as major risk factors for the development of atopic dermatitis and asthma.

Network of Myeloid and Plasmacytoid Dendritic Cells in Atopic Dermatitis

Atopic dermatitis (AD) presents as a chronic relapsing skin disease with high prevalence in children. The typical distributed skin lesions make the clinical diagnosis of AD very simple and clear-cut in most of the cases. In contrast, the underlying mechanisms leading to the manifestation of AD are more than complex and consist of genetic components combined with various deficiencies on the level of innate and adaptive immune mechanisms. Challenged by this puzzle, scientific approaches of the last years have made considerable progress in gaining insights into the mechanisms, which cause AD. AD is a biphasic inflammatory skin disease characterized by an initial phase predominated by Th2 cytokines which switches into a second, more chronic Th1-dominated eczematous phase. Two different dendritic cell (DC) subtypes bearing the high-affinity receptor for IgE (FcepsilonRI) have been identified in the epidermal skin of AD patients: FcepsilonRIhigh Langerhans cells (LCs) and FcepsilonRIhigh inflammatory dendritic epidermal cells (IDECs). These two DC subtypes are believed to contribute distinctly to the biphasic nature and the outcome of T cell responses in AD. In contrast, plasmacytoid DCs, which play an important role in the defence against viral infections, have been shown to bear the high-affinity receptor for IgE too but are nearly absent from the epidermal skin lesions of AD patients. In light of recent developments, the picture emerges that different IgE-receptor bearing DC subtypes in the blood and skin of AD patients play a pivotal role in the complex network of DCs, which is highlighted in this review.

Retinol concentrations after birth are inversely associated with atopic manifestations in children and young adults

BACKGROUND

Vitamin A has anti-inflammatory and immunomodulatory effects, and its deficiency results in impaired specific and innate immunity. Vitamin A is essential for inducing the gut-homing specificity on T cells.

OBJECTIVE

As an impaired gut immune response in early infancy may contribute to the development of atopic sensitization, we looked for an association of plasma retinol concentrations and the subsequent development of allergic symptoms in healthy infants.

METHODS

A cohort of 200 unselected, full-term newborns were followed up from birth to age 20 years. The plasma retinol concentration was determined in cord blood (n=97), at ages of 2, 4 and 12 months (n=95), and at ages 5 years (n=155) and 11 years (n=151). The subjects were re-examined at the ages of 5, 11 and 20 years with assessment of the occurrence of allergic symptoms during the preceding year, skin prick testing and measurement of serum total IgE.

RESULTS

subjects with allergic symptoms or a positive skin prick test (SPT) in childhood or adolescence had lower retinol concentrations in infancy and childhood than symptom-free subjects. The difference was most pronounced at age 2 months. Retinol concentration at 2 months correlated inversely with positive SPT at ages of 5 and 20 years, and with allergic symptoms at age 20 years.

CONCLUSION

Retinol concentration in young infants is inversely associated with the subsequent development of allergic symptoms. We propose that an inborn regulation of retinol may play a role in atopic sensitization, possibly through regulating the intestinal T cell responses.

[Advances in the pathogenesis of atopic dermatitis]

The incidence of atopic dermatitis (AD) is noticeably increasing in industrialized countries. New insights into the pathogenesis of this disease are mirrored by a changed terminology suggested by the World Allergy Organization: a distinction between a so-called atopic and non-atopic dermatitis. The pathogenesis of the AD, which this article concentrates on, is highly complex. Genetic and environmental factors play a pivotal role in triggering AD. The complex pattern of cytokines and chemokines, reflecting a deviated immune response in AD patients, is a focus of research, as are the involvement of various cells and the epidermal barrier. Research concerning T cells with regulatory features as well as IgE-mediated autoreactivity will soon give insight into the defective tolerance of atopic patients and might possibly lead to new concepts in the management of the disease.

Hyperresponsive TH2 cells with enhanced nuclear factor-κB activation induce atopic dermatitis–like skin lesions in Nishiki-nezumi Cinnamon/Nagoya mice

BACKGROUND

Nishiki-nezumi Cinnamon/Nagoya (NC/Nga) mice raised in nonair-controlled conventional circumstances spontaneously develop atopic dermatitis-like skin lesions; however, the underlying mechanisms remain unclear.

OBJECTIVE

We wanted to identify the critical intracellular signaling molecules in T cells that induce atopic dermatitis-like skin legions in NC/Nga mice.

METHODS

We examined the levels of signal transduction and cytokine production in T cells, particularly those in atopic dermatitis-like lesions induced by the topical injection of mite antigens in NC/Nga mice under specific pathogen-free conditions.

RESULTS

In NC/Nga mice maintained under specific pathogen-free conditions, the capability of T(H)1/T(H)2 and T cytotoxic 1/T cytotoxic 2 (Tc1/Tc2) cell differentiation increased significantly. T-cell antigen receptor-mediated activation of the extracellular signal-regulated kinase/mitogen-activated protein kinase cascade and nuclear factor-kappaB (NF-kappaB) signaling were enhanced in NC/Nga T cells. The expression of T(H)2 cytokines (IL-4, IL-13, and IL-5) and that of GATA-binding protein 3 (GATA3), avian musculoaponeurotic fibrosarcoma (c-Maf), NF-kappaB, and activator protein 1 (AP1) selectively increased in draining lymph node T cells of NC/Nga mice. Moreover, the cell transfer of inhibitory NF-kappaB mutant-infected T(H)2 cells reduced ear thickness in the mite antigen-induced skin lesion of NC/Nga mice.

CONCLUSION

Hyperresponsive T(H)2 cells with an enhanced activity of NF-kappaB and AP1 play a crucial role in the pathogenesis of atopic dermatitis-like skin lesions in NC/Nga mice.

CLINICAL IMPLICATIONS

These results indicate potential therapeutic usefulness of developing selective inhibitors for NF-kappaB in the treatment of human atopic dermatitis.

Impaired virus-induced interferon-alpha2 release in adult asthmatic patients

BACKGROUND

Interferon-alpha (IFN-alpha) not only serves as a first defence line of the immune system against viral attacks but also interacts with T-helper type 1 (Th1)/ T-helper type 2 (Th2) regulation and various other cell types like basophils and monocytes, thereby linking innate and acquired immunity. Recently, we demonstrated that children with allergic asthma produced significantly lower amounts of virus-induced IFN-alpha2 compared with healthy children or those with intrinsic asthma.

OBJECTIVE

In this study, we extend our analysis to examine in a cohort study whether IFN-alpha2 is also reduced in allergic asthma of adults.

METHODS

Adults with allergic asthma and healthy controls were prospectively recruited. Blood cultures were stimulated with different viruses (respiratory syncytial virus (RSV), newcastle disease virus (NDV)) and analysed for IFN-alpha2 protein release and gene transcription.

RESULTS

Virus-induced IFN-alpha2 release from blood cells of allergic asthmatic patients was significantly reduced compared with healthy controls, independent of the virus used (NDV(asthma)=221+/-134 pg/mL, NDV(healthy)=555+/-341 pg/mL, P=0.003 and RSV(asthma)=46+/-27 pg/mL, RSV(healthy)=108+/-90 pg/mL, P=0.014). Values=mean+/-standard deviation). It was not influenced by medication, especially cortico-steroids. IFN-alpha2 mRNA expression 5 h after NDV stimulation confirmed the ELISA results and correlated well with release data (r=0.397, P=0.033).

CONCLUSION

Like children, adults with allergic asthma show impaired virus-induced IFN-alpha2 release in whole blood, indicating a systemic phenomenon in patients with bronchial asthma and atopic phenotype. Impaired virus-induced IFN-alpha release could be a marker of inflammation in chronic allergic asthma.

Skin barrier function, epidermal proliferation and differentiation in eczema

Skin permeability barrier function is impaired in eczema, particularly in contact and atopic dermatitis (AD). In contact dermatitis disruption of the barrier by irritants and allergens is the primary event, followed by sensitization, inflammation, increased epidermal proliferation and changes in differentiation. Genetically impaired skin barrier function is already present in non-lesional and more pronounced in lesional skin in AD. Increased epidermal proliferation and disturbed differentiation, including changes in lipid composition, cause impaired barrier function in AD. Defective permeability barrier function enables the enhanced penetration of environmental allergens into the skin and initiates immunological reactions and inflammation. Barrier dysfunction is therefore crucially involved in the pathogenesis of AD. The atopic syndrome represents a genetically impaired skin barrier function as well as impaired nasal, bronchial, and intestinal mucous membranes leading to AD, allergic rhinitis, bronchial asthma or aggravation of AD. Common treatment strategies for eczema include the application of lipid-based creams and ointments, which aim toward the restoration of the defective permeability barrier, thus helping to normalize proliferation and differentiation.

Therapie des atopischen Ekzems

Atopic eczema is one of the most common diseases in dermatology. Patients suffer from both the chronic relapsing skin disease and the associated emotional stress. Itching and visible lesions on the face and hands are the most unpleasant features for many often young patients, seriously reducing their quality of life. New therapeutic approaches have changed the management of atopic eczema in recent years. Relatively potent new drugs with fewer side effects than corticosteroids help to control the disease. This review focuses on the basic principles of modern atopic eczema treatment, emphasizing basic emollient therapy and topical therapy with calcineurin inhibitors.

A functional polymorphism in MMP-9 is associated with childhood atopic asthma

Although MMP-9 has been suggested to be important in inflammation and in the connective tissue remodeling associated with asthma, the genetic influences of the polymorphisms of MMP-9 are unclear. To examine whether polymorphisms in MMP-9 are associated with childhood atopic asthma, we identified a total of 17 polymorphisms and conducted an association study with asthma (n = 290) and controls (n = 638). 2127G>T and 5546G>A (R668Q) were significantly associated with the risk of childhood atopic asthma (p = 0.0032 and 0.0016, respectively). In haplotype analysis, we also found a positive association with a haplotype (p = 0.0053). MMP-9 was expressed in cultured human bronchial epithelial cells, and the mRNA expression level was upregulated by dsRNA. Furthermore, the promoter SNP -1590C>T, in strong linkage disequilibrium with 2127G>T, enhanced the transcriptional level of MMP-9. Thus, the MMP-9 gene might be involved in the development of asthma through functional genetic polymorphisms.

Epidermal barrier formation and recovery in skin disorders

Skin is at the interface between the complex physiology of the body and the external, often hostile, environment, and the semipermeable epidermal barrier prevents both the escape of moisture and the entry of infectious or toxic substances. Newborns with rare congenital barrier defects underscore the skin's essential role in a terrestrial environment and demonstrate the compensatory responses evoked ex utero to reestablish a barrier. Common inflammatory skin disorders such as atopic dermatitis and psoriasis exhibit decreased barrier function, and recent studies suggest that the complex response of epidermal cells to barrier disruption may aggravate, maintain, or even initiate such conditions. Either aiding barrier reestablishment or dampening the epidermal stress response may improve the treatment of these disorders. This Review discusses the molecular regulation of the epidermal barrier as well as causes and potential treatments for defects of barrier formation and proposes that medical management of barrier disruption may positively affect the course of common skin disorders.

Loss-of-function variations within the filaggrin gene predispose for atopic dermatitis with allergic sensitizations

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a strong genetic background. One of the characteristic features of AD and causative factor for the disease is an impaired epidermal skin barrier based on a primary defect of epidermal differentiation.

OBJECTIVES

Recently, 2 loss-of-function mutations (R501X and 2282derl4) in the filaggrin gene (FLG) that cause ichthyosis vulgaris, one of the most common inherited skin disorders of keratinization, have been reported to be strong predisposing factors for AD.

METHODS

We evaluated the association of the loss-of-function mutations R501X and 2282del4 within the FLG gene in a large collection of 476 well-characterized white German families with AD by using the transmission-disequilibrium test.

RESULTS

Our family-based approach revealed prominent associations between the 2 loss-of-function FLG mutations and AD, as previously observed in a traditional Mendelian linkage analysis and case-control cohort analysis approach. In addition, we observed associations of the FLG mutations in particular with the extrinsic subtype of AD, which is characterized by high total serum IgE levels and concomitant allergic sensitizations. Furthermore, FLG mutations are significantly associated with palmar hyperlinearity in patients with AD, which represents a shared feature of AD and ichthyosis vulgaris.

CONCLUSION

Together these data implicate that FLG is the first really strong genetic factor identified in a common complex disease.

CLINICAL IMPLICATIONS

These findings underline the crucial role of the skin barrier in preventing allergic sensitization.

Finding the molecular basis of complex genetic variation in humans and mice

I survey the state of the art in complex trait analysis, including the use of new experimental and computational technologies and resources becoming available, and the challenges facing us. I also discuss how the prospects of rodent model systems compare with association mapping in humans.

A brief targeted review of susceptibility factors, environmental exposures, asthma incidence, and recommendations for future asthma incidence research

Relative to research on effects of environmental exposures on exacerbation of existing asthma, little research on incident asthma and environmental exposures has been conducted. However, this research is needed to better devise strategies for the prevention of asthma. The U.S. Environmental Protection Agency (EPA) and National Institute of Environmental Health Sciences held a conference in October 2004 to collaboratively discuss a future research agenda in this area. The first three articles in this mini-monograph summarize the discussion on potential putative environmental exposure; they include an overview of asthma and conclusions of the workshop participants with respect to public health actions that could currently be applied to the problem and research needs to better understand and control the induction and incidence of asthma, the potential role of indoor/outdoor air pollutants in the induction of asthma), and biologics in the induction of asthma. Susceptibility is a key concept in the U.S. EPA "Asthma Research Strategy" document and is associated with the U.S. EPA framework of protecting vulnerable populations from potentially harmful environmental exposures. Genetics, age, and lifestyle (obesity, diet) are major susceptibility factors in the induction of asthma and can interact with environmental exposures either synergistically or antagonistically. Therefore, in this fourth and last article we consider a number of "susceptibility factors" that potentially influence the asthmatic response to environmental exposures and propose a framework for developing research hypotheses regarding the effects of environmental exposures on asthma incidence and induction.

Computer prediction of allergen proteins from sequence-derived protein structural and physicochemical properties

BACKGROUND

Computational methods have been developed for predicting allergen proteins from sequence segments that show identity, homology, or motif match to a known allergen. These methods achieve good prediction accuracies, but are less effective for novel proteins with no similarity to any known allergen.

METHODS

This work tests the feasibility of using a statistical learning method, support vector machines, as such a method. The prediction system is trained and tested by using 1005 allergen proteins from the Allergome database and 22,469 non-allergen proteins from 7871 Pfam families.

RESULTS

Testing results by an independent set of 229 allergen and 6717 non-allergen proteins from 7871 Pfam families show that 93.0% and 99.9% of these are correctly predicted, which are comparable to the best results of other methods. Of the 18 novel allergen proteins non-homologous to any other proteins in the Swissprot database, 88.9% is correctly predicted. A further screening of 168,128 proteins in the Swissprot database finds that 2.9% of the proteins are predicted as allergen proteins, which is consistent with the estimated numbers from motif-based methods.

CONCLUSIONS

Our study suggests that SVM is a potentially useful method for predicting allergen proteins and it has certain capability for predicting novel allergen proteins. Our software can be accessed at .

IL-31 is associated with cutaneous lymphocyte antigen-positive skin homing T cells in patients with atopic dermatitis

BACKGROUND

IL-31 is a newly discovered T-cell cytokine that, when overexpressed in mice, results in pruritus and skin dermatitis resembling human atopic dermatitis (AD).

OBJECTIVE

We sought to investigate the expression of IL-31 and IL-31 receptor A (IL-31RA) in skin biopsy specimens and peripheral blood cells from patients with AD and healthy individuals.

METHODS

Expression of IL-31 and IL-31RA was evaluated in skin biopsy specimens from patients with AD and healthy individuals by means of immunohistochemistry and RT-PCR. IL-31 protein production by skin-homing cutaneous lymphocyte antigen (CLA)-positive T cells was also assessed.

RESULTS

IL-31RA protein was expressed by keratinocytes and infiltrating macrophages in skin biopsy specimens from patients with AD. Comparisons between skin from patients with AD and healthy skin showed IL-31RA expression at higher levels on epidermal keratinocytes in AD samples. Infiltrating cells, more numerous in skin from patients with AD compared with that of healthy individuals, expressed IL31 mRNA. Histomorphometric analysis of these cells indicated they were of the lymphocytic lineage, with the majority of cells staining positive for CLA and CD3. IL31 mRNA and protein expression is largely restricted to CD45RO(+) (memory) CLA(+) T cells in peripheral blood of patients with AD and healthy volunteers. Moreover, circulating CLA(+) T cells from patients with AD, but not from patients with psoriasis, are capable of producing higher levels of IL-31 compared with CLA(+) T cells from healthy individuals. However, the average levels of IL-31 were not significantly different between patients with AD and healthy individuals.

CONCLUSION

We provide evidence that IL-31 expression is associated with CLA(+) T cells and might contribute to the development of AD-induced skin inflammation and pruritus.

Chronic rhinosinusitis and superantigens

This article discusses the potential role of bacterial superantigens (SAgs) in chronic rhinosinusitis with nasal polyposis (CRS/NP). First, it briefly describes SAgs, focusing on how they interact with the immune system by binding to T-cell receptors (TCR) and major histocompatibility complex (MHC) class II molecules. Second, it discusses the role of SAgs in other chronic inflammatory diseases.Finally, it presents evidence for the role of SAgs in the pathogenesis and maintenance of CRS/NP focusing on current research and future considerations.

Two-dimensional electrophoretic profiling of atopic dermatitis in primary cultured keratinocytes from patients

Recently, we reported altered protein expression in primary cultured fibroblasts from atopic dermatitis (AD) patients. As a sequential study, we conducted proteomic analysis of primary keratinocytes derived from AD patients to further identify AD-related proteins. Three pH ranges, 4-7, 6-9, and 7-11, were used to profile the altered protein expression in AD. We obtained 46 candidate spots from the 2-D gel image analysis: 18 proteins were up-regulated and 27 proteins were down-regulated. Among the several important candidate proteins, NCC27 showed the same profile of a defect in PTM in both AD-derived keratinocytes and fibroblasts. On the basis of current and previous reports, real-time PCR was performed on select candidate genes to compare RNA and protein expression levels in AD-derived keratinocytes and fibroblasts. Our results provide new clues to aid in understanding the mechanism of atopic alterations in keratinocytes and suggest new AD-associated proteins that are important in AD pathogenesis.