Evidence for superantigen involvement in skin homing of T cells in atopic dermatitis

CLA+ memory T cells in atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Superantigens, a Paradox of the Immune Response

Staphylococcal enterotoxins are a wide family of bacterial exotoxins with the capacity to activate as much as 20% of the host T cells, which is why they were called superantigens. Superantigens (SAgs) can cause multiple diseases in humans and cattle, ranging from mild to life-threatening infections. Almost all S. aureus isolates encode at least one of these toxins, though there is no complete knowledge about how their production is triggered. One of the main problems with the available evidence for these toxins is that most studies have been conducted with a few superantigens; however, the resulting characteristics are attributed to the whole group. Although these toxins share homology and a two-domain structure organization, the similarity ratio varies from 20 to 89% among different SAgs, implying wide heterogeneity. Furthermore, every attempt to structurally classify these proteins has failed to answer differential biological functionalities. Taking these concerns into account, it might not be appropriate to extrapolate all the information that is currently available to every staphylococcal SAg. Here, we aimed to gather the available information about all staphylococcal SAgs, considering their functions and pathogenicity, their ability to interact with the immune system as well as their capacity to be used as immunotherapeutic agents, resembling the two faces of Dr. Jekyll and Mr. Hyde.

Roles and therapeutic potential of CD1d-Restricted NKT cells in inflammatory skin diseases

Natural killer T (NKT) cells are innate-like T lymphocytes that recognize glycolipid antigens rather than peptides. Due to their immunoregulatory properties, extensive work has been done to elucidate the immune functions of NKT cells in various immune contexts such as autoimmunity for more than two decades. In addition, as research on barrier immunity such as the mucosa-associated lymphoid tissue has flourished in recent years, the role of NKT cells to immunity in the skin has attracted substantial attention. Here, we review the contributions of NKT cells to regulating skin inflammation and discuss the factors that can modulate the functions of NKT cells in inflammatory skin diseases such as atopic dermatitis. This mini-review article will mainly focus on CD1d-dependent NKT cells and their therapeutic potential in skin-related immune diseases.

Exploring the Role of Staphylococcus aureus in Inflammatory Diseases

Staphylococcus aureus is a very common Gram-positive bacterium, and S. aureus infections play an extremely important role in a variety of diseases. This paper describes the types of virulence factors involved, the inflammatory cells activated, the process of host cell death, and the associated diseases caused by S. aureus. S. aureus can secrete a variety of enterotoxins and other toxins to trigger inflammatory responses and activate inflammatory cells, such as keratinocytes, helper T cells, innate lymphoid cells, macrophages, dendritic cells, mast cells, neutrophils, eosinophils, and basophils. Activated inflammatory cells can express various cytokines and induce an inflammatory response. S. aureus can also induce host cell death through pyroptosis, apoptosis, necroptosis, autophagy, etc. This article discusses S. aureus and MRSA (methicillin-resistant S. aureus) in atopic dermatitis, psoriasis, pulmonary cystic fibrosis, allergic asthma, food poisoning, sarcoidosis, multiple sclerosis, and osteomyelitis. Summarizing the pathogenic mechanism of Staphylococcus aureus provides a basis for the targeted treatment of Staphylococcus aureus infection.

Epigenetic alterations in skin homing CD4+CLA+ T cells of atopic dermatitis patients

T cells expressing the cutaneous lymphocyte antigen (CLA) mediate pathogenic inflammation in atopic dermatitis (AD). The molecular alterations contributing to their dysregulation remain unclear. With the aim to elucidate putative altered pathways in AD we profiled DNA methylation levels and miRNA expression in sorted T cell populations (CD4⁺, CD4⁺CD45RA⁺ naïve, CD4⁺CLA⁺, and CD8⁺) from adult AD patients and healthy controls (HC). Skin homing CD4⁺CLA⁺ T cells from AD patients showed significant differences in DNA methylation in 40 genes compared to HC (p < 0.05). Reduced DNA methylation levels in the upstream region of the interleukin-13 gene (IL13) in CD4⁺CLA⁺ T cells from AD patients correlated with increased IL13 mRNA expression in these cells. Sixteen miRNAs showed differential expression in CD4⁺CLA⁺ T cells from AD patients targeting genes in 202 biological processes (p < 0.05). An integrated network analysis of miRNAs and CpG sites identified two communities of strongly interconnected regulatory elements with strong antagonistic behaviours that recapitulated the differences between AD patients and HC. Functional analysis of the genes linked to these communities revealed their association with key cytokine signaling pathways, MAP kinase signaling and protein ubiquitination. Our findings support that epigenetic mechanisms play a role in the pathogenesis of AD by affecting inflammatory signaling molecules in skin homing CD4⁺CLA⁺ T cells and uncover putative molecules participating in AD pathways.

Innate Lymphocyte Mechanisms in Skin Diseases

Innate lymphocyte populations are emerging as key effectors in tissue homeostasis, microbial defense, and inflammatory skin disease. The cells are evolutionarily ancient and carry conserved principles of function, which can be achieved through shared or unique specific mechanisms. Recent technological and treatment advances have provided insight into heterogeneity within and between individuals and species. Similar pathways can extend through to adaptive lymphocytes, which softens the margins with innate lymphocyte populations and allows investigation of nonredundant pathways of immunity and inflammation that might be amenable to therapeutic intervention. Here, we review advances in understanding of innate lymphocyte biology with a focus on skin disease and the roles of commensal and pathogen responses and tissue homeostasis.

Staphylococcus aureus Isolated from Skin from Atopic-Dermatitis Patients Produces Staphylococcal Enterotoxin Y, Which Predominantly Induces T-Cell Receptor Vα-Specific Expansion of T Cells

While investigating the virulence traits of Staphylococcus aureus adhering to the skin of atopic-dermatitis (AD) patients, we identified a novel open reading frame (ORF) with structural similarity to a superantigen from genome sequence data of an isolate from AD skin. Concurrently, the same ORF was identified in a bovine isolate of S. aureus and designated SElY (H. K. Ono, Y. Sato'o, K. Narita, I. Naito, et al., Appl Environ Microbiol 81:7034-7040, 2015, https://doi.org/10.1128/AEM.01873-15). Recombinant SElY_bov had superantigen activity in human peripheral blood mononuclear cells. It further demonstrated emetic activity in a primate animal model, and it was proposed that SElY be renamed SEY (H. K. Ono, S. Hirose, K. Narita, M. Sugiyama, et al., PLoS Pathog 15:e1007803, 2019, https://doi.org/10.1371/journal.ppat.1007803). Here, we investigated the prevalence of the sey gene in 270 human clinical isolates of various origins in Japan. Forty-two strains were positive for the sey gene, and the positive isolates were from patients with the skin diseases atopic dermatitis and impetigo/staphylococcal scalded skin syndrome (SSSS), with a detection rate of ∼17 to 22%. There were three variants of SEY (SEY₁, SEY₂, and SEY₃), and isolates producing SEY variants formed three distinct clusters corresponding to clonal complexes (CCs) 121, 59, and 20, respectively. Most sey ⁺ isolates produced SEY in broth culture. Unlike SEY_bov, the three recombinant SEY variants exhibited stability against heat treatment. SEY predominantly activated human T cells with a particular T-cell receptor (TCR) Vα profile, a unique observation since most staphylococcal enterotoxins exert their superantigenic activities through activating T cells with specific TCR Vβ profiles. SEY may act to induce localized inflammation via skin-resident T-cell activation, facilitating the pathogenesis of S. aureus infection in disrupted epithelial barriers.

Antibiotic choice and methicillin-resistant Staphylococcus aureus rate in children hospitalized for atopic dermatitis

BACKGROUND

Systemic antibiotics are commonly used in hospitalized patients with severe atopic dermatitis (AD) exacerbation. However, the antibiotic prescribing patterns are unclear.

OBJECTIVE

To compare the prescribing patterns of antibiotics for children who were hospitalized for AD exacerbation and infectious complications.

METHODS

Electronic medical records were reviewed for patients younger than 18 years who were hospitalized for AD exacerbation or infectious complications based on International Classification of Diseases, Ninth Revision, Clinical Modification and International Classification of Diseases, Tenth Revision, Clinical Modification codes from 2003 to 2018. The following information was obtained: history, physical examination findings, physician discharge summary, antibiotic treatments, serum tests, and wound cultures. The t test was used to compare clinical and laboratory features.

RESULTS

A total of 174 patients with AD were included. Seventy patients had AD exacerbation and 104 had infectious complications, including cellulitis, abscesses, invasive infections, and eczema herpeticum. The differences between these 2 groups of patients were further verified by length of stay, serum total IgE level, and inflammatory markers (C-reactive protein and erythrocyte sedimentation rate). A total of 56 of 70 patients (80%) with AD exacerbation were treated with a systemic antibiotic. Clindamycin and vancomycin together accounted for 88% of antibiotics on admission for both groups, whereas clindamycin and sulfamethoxazole-trimethoprim were prescribed at similar rates for both groups at discharge. Wound culture results showed that the methicillin-resistant Staphylococcus aureus (MRSA) rate was significantly lower in children with AD exacerbation (22%) vs infectious complications (39%).

CONCLUSION

Children were treated with a high frequency of anti-MRSA antibiotics for inpatient AD exacerbation and infectious complications. However, the rate of MRSA was significantly lower in children with AD exacerbation. Thus, empiric antibiotic choice for infectious complications may not be appropriate for AD exacerbation.

Role of Superantigens in Allergic Inflammation: Their Relationship to Allergic Rhinitis, Chronic Rhinosinusitis, Asthma, and Atopic Dermatitis

OBJECTIVES

Our intention was to review all material published to date regarding superantigens (SAgs) and allergy from an otorhinolaryngological viewpoint to understand this association more clearly.

METHODS

We identified all materials published mentioning both SAg and allergic rhinitis (AR), chronic sinusitis, asthma, and atopic dermatitis (AD) that are indexed on PubMed, Google, or the ProQuest Central databases.

RESULTS

Staphylococcus aureus is a significant bacterial pathogen in humans and has the ability to produce enterotoxins with superantigenic features. The inflammatory response in allergy seen in both B cell and T cell may be attributed to SAgs. Sufferers of both allergic asthma with rhinitis and AR alone produce serological evidence of immunoglobulin E formation to SAgs produced by S. aureus. Perennial AR sufferers carry S. aureus more frequently and the presence of the organism within the nasal cavity may exacerbate perennial AR. SAg produced by S. aureus potentially worsens the asthmatic inflammatory response within the airway and may lead to the airways becoming hyperresponsive, as well as possibly activating T cells if asthmatic control is poor. Staphylococcal SAgs potentially increase the risk of developing chronic rhinosinusitis with nasal polyposis, additionally being a marker for more severe disease. If SAgs bring about chronic inflammatory responses in the nose and sinuses, then T cells excreting interferon-gamma may be a crucial mediator. In allergic dermatitis, S. aureus could be a key player in exacerbation of the condition. Even in younger pediatric patients with allergic dermatitis, allergic hypersensitivity to SAgs is frequent and may be a factor explaining how severe the condition becomes.

CONCLUSION

Just as SAgs are known to feature in many allergic conditions, they play their part in AR, chronic rhinosinusitis, asthma, and AD. Further research is required before the relationship between SAgs and allergy can be adequately explained.

Nonlesional atopic dermatitis skin shares similar T-cell clones with lesional tissues

BACKGROUND

Atopic dermatitis (AD) is characterized by robust immune activation. Various T-cell subsets, including Th2/Th22 cells, are increased in lesional and nonlesional skin. However, there is conflicting literature on the diversity of the T-cell receptor (TCR) repertoire in lesional AD, and its relation to nonlesional skin remains unclear.

METHODS

We performed high-throughput deep sequencing of the β-TCR repertoire in 29 lesional and 19 nonlesional AD biopsies, compared to six healthy control and six cutaneous T-cell lymphoma (CTCL) samples from previously published cohorts.

RESULTS

While greater T-cell infiltrates were observed in lesional vs nonlesional AD, TCR repertoire diversity was similar in lesional and nonlesional tissues, and absolute numbers of unique T-cell clones correlated with respective T-cell counts. Most (87%) top expanded lesional T-cell clones were shared with nonlesional tissues, and they were largely maintained after 16 weeks of successful treatment with topical triamcinolone. Nevertheless, both lesional and nonlesional AD showed a highly polyclonal TCR pattern, without evidence of oligoclonal expansion, or a preferred usage of certain V-β genes in AD skin. Size of the overall T-cell infiltrate, but not the level of clonality, correlated with mRNA levels of key inflammatory mediators (e.g., IL-13, CCL17, IL23p19, CXCL10).

CONCLUSION

While AD harbors a highly polyclonal T-cell receptor repertoire, and despite the lack of information on TCR antigen specificity, the sharing of top abundant clones between lesional and nonlesional skin, and their persistence after months of therapy, points to the continuous presence of potentially pathogenic skin resident memory T cells well beyond clinically inflamed lesions.

Circulating CLA+ T cells in atopic dermatitis and their possible role as peripheral biomarkers

Cutaneous lymphocyte-associated antigen (CLA⁺ ) T cells are specialized for skin homing and represent the main T-cell population in atopic dermatitis (AD) lesions. CLA⁺ is expressed on the surface of circulating CD45RO⁺ memory T cells and most skin-infiltrating T cells. Mechanistic studies and thus treatment advancements are limited by the need of large number of skin biopsies. Circulating CLA⁺ T cells may be a reliable surrogate marker of the inflammatory events occurring in the skin, and thus, the evaluation of CLA⁺ T cells in the blood may eliminate the need for skin biopsies. Preliminary work in AD has established that disease-associated T-cell abnormalities can be approached by either a study of skin lesions or activated CLA⁺ T-cell subsets in peripheral blood. Future studies in adults and children, across different skin disorders, correlating blood and skin phenotypes and determining skin-homing T-cell functional properties are needed to establish whether CLA⁺ memory subsets can be used as biomarkers and a substitute for skin biopsies. This review summarizes the latest advancements reached on circulating CLA⁺ in AD and the great potential they harbor in understanding AD mechanisms.

Lidocaine inhibits staphylococcal enterotoxin-stimulated activation of peripheral blood mononuclear cells from patients with atopic dermatitis

Atopic dermatitis (AD) is an inflammatory, chronically relapsing, pruritic skin disease and lesions associated with AD are frequently colonized with Staphylococcus aureus (S. aureus). Activation of T cells by staphylococcal enterotoxins (SE) plays a crucial role in the pathogenesis of AD. Previous studies have demonstrated that lidocaine could attenuate allergen-induced T cell proliferation and cytokine production in peripheral blood mononuclear cells (PBMCs) from asthma patients. The purpose of this study was to investigate the effects of lidocaine on SE-stimulated activation of PBMCs from AD patients. PBMCs were isolated from ten AD patients and stimulated by staphylococcal enterotoxin A (SEA) or staphylococcal enterotoxin B (SEB) in the presence or absence of lidocaine in various concentrations. Cellular proliferation and the release of representative TH1- and TH2-type cytokines were measured. The effect of lidocaine on filaggrin (FLG) expression in HaCaT cells co-cultured with SE-activated PBMCs was also examined. Our results demonstrated that lidocaine dose-dependently inhibited the proliferative response and the release of IL-4, IL-5, IL-13, TNF-α, and IFN-γ from SEA- and SEB-stimulated PBMCs and also blocked the down-regulation of FLG expression in HaCaT cells co-cultured with SEA- and SEB-activated PBMCs. These results indicate that lidocaine inhibited SEA- and SEB-stimulated activation of PBMCs from patients with AD. Our findings encourage the use of lidocaine in the treatment of AD.

The glucocorticoid receptor: a revisited target for toxins

The hypothalamic-pituitary-adrenal (HPA) axis activation and glucocorticoid responses are critical for survival from a number of bacterial, viral and toxic insults, demonstrated by the fact that removal of the HPA axis or GR blockade enhances mortality rates. Replacement with synthetic glucocorticoids reverses these effects by providing protection against lethal effects. Glucocorticoid resistance/insensitivity is a common problem in the treatment of many diseases. Much research has focused on the molecular mechanism behind this resistance, but an area that has been neglected is the role of infectious agents and toxins. We have recently shown that the anthrax lethal toxin is able to repress glucocorticoid receptor function. Data suggesting that the glucocorticoid receptor may be a target for a variety of toxins is reviewed here. These studies have important implications for glucocorticoid therapy.

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.

Antigen-driven bystander effect accelerates epicutaneous sensitization with a new protein allergen

Exposure to protein allergen epicutaneously, inducing a Th2-dominant immune response, sensitizes the host to the development of atopic disease. Antigen-driven bystander effect demonstrates that polarized T cells could instruct naïve T cells to differentiate into T cells with similar phenotype. In this study, we aimed to determine the contribution of antigen-driven bystander effect on epicutaneous sensitization with a newly introduced protein allergen. BALB/c mice were immunized intraperitoneally with BSA emulsified in alum, known to induce a Th2 response, three weeks before given BSA and OVA epicutaneously. Lymph node cells from these mice restimulated with OVA secreted higher levels IL-4, IL-5 and IL-13 as compared with cells from mice without BSA immunization. In addition, BALB/c mice immunized subcutaneously with BSA emulsified in complete Freund's adjuvant, known to induce a Th1-predominant response, also induced higher Th1 as well as Th2 cytokine response when restimulated with OVA as compared with mice without immunization. We demonstrated that subcutaneous immunization with BSA in CFA induced Th2 as well as Th1 response. The threshold of epicutaneous sensitization to OVA was also reduced, possibly due to increased expressions of IL-4 and IL-10 in the draining lymph nodes during the early phase of sensitization. In conclusion, antigen-driven bystander effect, whether it is of Th1- or Th2-predominant nature, can accelerate epicutaneous sensitization by a newly introduced protein allergen. These results provide a possible explanation for mono- to poly-sensitization spread commonly observed in atopic children.

T(H)2 adjuvants: implications for food allergy

A persistent question for immunologists studying allergic disease has been to define the characteristics of a molecule that make it allergenic. There has been substantial progress elucidating mechanisms of innate priming of T(H)2 immunity in the past several years. These accumulating data demonstrate that T(H)2 immunity is actively induced by an array of molecules, many of which were first discovered in the context of antihelminthic immune responses. Similar intrinsic or associated activities are now known to account for the T(H)2 immunogenicity of some allergens, and may prove to play a role for many more. In this review, we discuss what has been discovered regarding molecules that induce innate immune activation and the pathways that promote T(H)2-polarized immune responses generally, and specifically what role these mechanisms may play in food allergy from models of food allergy and the study of T(H)2 gastrointestinal adjuvants.

Cellular aspects of atopic dermatitis

Atopic dermatitis (AD) is a highly pruritic, chronic, and relapsing inflammatory skin disease. Recent interest in AD has been sparked by reports of its increasing prevalence and its contribution to increasing health care costs. A precise understanding of immunologic mechanisms is crucial for the development of effective treatment strategies for AD. Various studies reveal that AD has a multifactorial cause with the activation of complex immunologic and inflammatory pathways. This review will discuss cellular-mediated immunological pathomechanisms of AD. Emphasis will be given to the role played by T cells, antigen-presenting cells, eosinophils, and keratinocytes. We also examine the immunological effect of superantigens on various inflammatory cells including T regulatory cells.

Role of bacterial pathogens in atopic dermatitis

The skin of atopic dermatitis (AD) patients exhibits a striking susceptibility to colonization and infection with Staphylococcus aureus. This review summarizes our understanding about the role of S. aureus in AD. Indeed, S. aureus colonization is both a cause and a consequence of allergic skin inflammation. The mechanisms that allergic skin inflammation of AD promotes the increase of S. aureus colonization include skin barrier dysfunction, increased synthesis of the extracellular matrix adhesins for S. aureus, and defective innate immune responses due to decreased production of endogenous antimicrobial peptides. On the other hand, the exotoxins secreted by S. aureus are superantigens. Staphylococcal superantigens (SsAgs) may penetrate the skin barrier and contribute to the persistence and exacerbation of allergic skin inflammation in AD through the stimulation of massive T cells, the role of allergens, direct stimulation of antigen-presenting cells and keratinocytes, the expansion of skin-homing cutaneous lymphocyte-associated antigen-positive T cells, and the augmentation of allergen-induced skin inflammation. SsAgs also induce corticosteroid resistance. In therapeutic interventions, anti-inflammatory therapy alone is very effective in reducing S. aureus colonization on the skin, but antibiotic treatment alone is unable to improve the allergic skin inflammation of AD. Therefore, we recommend the combination therapy of anti-inflammatory drugs and antibiotics in the AD patients with secondary bacterial infection, exacerbated AD, or poorly controlled AD. However, when AD is well controlled by anti-inflammatory drugs alone, we do not recommend the antibiotic therapy.

Staphylococcus aureus skin colonization in atopic dermatitis children is associated with decreased IFN-gamma production by peripheral blood CD4+ and CD8+ T cells

Atopic dermatitis (AD) is a chronic inflammatory skin disorder, which is associated with an increased expression of Th2 cytokines with concomitant decrease in IFN-gamma production by circulating CD4+ and CD8+ T cells. The skin of patients with AD is often colonized by Staphylococcus aureus, which may reflect in changes in immunological parameters. The aim of the study was flow cytometric measurement of some peripheral blood lymphocyte subsets expressing naive/memory marker (RA/RO) and activation marker (CD25) as well as intracellular production of IFN-gamma by peripheral blood CD4+ and CD8+ T cells from varied severity AD children and determine the impact of S. aureus skin colonization on cytokines profiles. There was a significant increase in the percentage of CD4+ and CD8+ T cells producing IL-4 and IL-13 and decrease in the percentage of CD4+ and CD8+ T cells producing IFN-gamma upon in vitro stimulation with phorbol 12-myristate 13-acetate and ionomycin in children with AD compared to healthy ones. The absolute number of CD4+ and CD8+ T cells expressing memory marker CD45RO was elevated as compared with controls. The severity of AD was positively correlated with the percentage of lymphocyte subsets: CD45RO+, CD4+CD45RO+, and the percentage of CD3+ and CD4+ expressing CD25 as well as the number of S. aureus on the skin. In conclusion, both CD4+ and CD8+ memory T cells are involved in the immunopathogenesis of AD. S. aureus skin colonization is related with disease severity and changes in expression of CD45RO and CD25 on T cells. A decrease in the percentage of CD4+ and CD8+ T cells producing IFN-gamma in AD children may explain propensity for skin infection.

Superantigen presentation by airway smooth muscle to CD4+ T lymphocytes elicits reciprocal proasthmatic changes in airway function

Microbial products serving as superantigens (SAgs) have been implicated in triggering various T cell-mediated chronic inflammatory disorders, including severe asthma. Given earlier evidence demonstrating that airway smooth muscle (ASM) cells express MHC class II molecules, we investigated whether ASM can present SAg to resting CD4(+) T cells, and further examined whether this action reciprocally elicits proasthmatic changes in ASM responsiveness. Coincubation of CD4(+) T cells with human ASM cells pulsed with the SAg, staphylococcal enterotoxin A (SEA), elicited adherence and clustering of class II and CD3 molecules at the ASM/T cell interface, indicative of immunological synapse formation, in association with T cell activation. This ASM/T cell interaction evoked up-regulated mRNA expression and pronounced release of the Th2-type cytokine, IL-13, into the coculture medium, which was MHC class II dependent. Moreover, when administering the conditioned medium from the SEA-stimulated ASM/T cell cocultures to isolated naive rabbit ASM tissues, the latter exhibited proasthmatic-like changes in their constrictor and relaxation responsiveness that were prevented by pretreating the tissues with an anti-IL-13 neutralizing Ab. Collectively, these observations are the first to demonstrate that ASM can present SAg to CD4(+) T cells, and that this MHC class II-mediated cooperative ASM/T cell interaction elicits release of IL-13 that, in turn, evokes proasthmatic changes in ASM constrictor and relaxant responsiveness. Thus, a new immuno-regulatory role for ASM is identified that potentially contributes to the pathogenesis of nonallergic (intrinsic) asthma and, accordingly, may underlie the reported association between microbial SAg exposure, T cell activation, and severe asthma.

Staphylococcus aureus-derived enterotoxins enhance house dust mite-induced patch test reactions in atopic dermatitis

BACKGROUND

Up to 65% of Staphylococcus aureus strains isolated from the skin of patients with atopic dermatitis (AD) produce exotoxins with superantigenic properties that may also act as allergens leading to an induction of exotoxin-specific IgE antibodies. Staphylococcal enterotoxin B (SEB) applied epicutaneously in a concentration of 10 micro g/cm(2), i.e. 200 micro g/ml, under occlusion induces cutaneous inflammation in patients with AD and healthy individuals.

METHODS

We performed patch tests in 32 adult patients with AD using different concentrations (i.e. 2-200 micro g/ml) of SEA, SEB and house dust mite (HDM) extract (500 micro g/ml). Furthermore, the respective enterotoxins and HDM extract were applied simultaneously to the same patch test site. Specific IgE levels to SEA, SEB and HDM were measured with the CAP FEIA.

RESULTS

The rates of patch test reactions to SEA and SEB increased with rising enterotoxin concentrations. There were no differences in the rates of patch test reactions to SEA and SEB between patients sensitized to the corresponding enterotoxin and non-IgE-sensitized patients. The number of patch test reactions to the mixture of enterotoxin and HDM extract was higher than the number of patch test reactions to either the enterotoxins or HDM extract. We identified 11 patients with AD who reacted neither to the enterotoxins nor to HDM extract, but who showed patch test reactions to the mixture. These reactions were not predicted by the presence of enterotoxin- or HDM-specific IgE.

CONCLUSIONS

Colonization with exotoxin-producing S. aureus may influence the outcome of patch tests in patients with AD.

Effects of Tributyltin on the Development of Atopic Dermatitis-Like Eruptions in DS-Nh Mice

BACKGROUND

In the last few decades, numerous chemical compounds have been produced as a result of industrial development. At the same time, the number of atopic dermatitis (AD) patients has been increasing. It has been reported that tributyltin (TBT) compounds have effects not only on the reproductive system but also on the immune system.

OBJECTIVE

To investigate whether TBT has an effect on AD, we fed a diet containing TBT to DS-Nh mice, which spontaneously developed dermatitis under conventional conditions.

METHODS

DS-Nh mice fed TBT or a control diet were examined for skin changes, number of Staphylococcus aureus on the skin and serum IgE levels. To determine Th1/Th2 cytokine production by lymphocytes, lymphocytes of DS-Nh mice fed TBT and of controls were cultured with staphylococcal enterotoxin B and cytokine levels in the supernatants were measured by ELISA. We observed not only spontaneous dermatitis but also dermatitis induced by sensitization with 2,4,6-trinitrochlorobenzene (TNCB).

RESULTS AND CONCLUSION

The AD-like lesions induced by TNCB sensitization were more severe in the mice fed TBT than in those fed the control diet. A greater increase in S. aureus on the skin was observed in the mice fed TBT than in the mice fed the control diet. A decrease in IFN-gamma production and an increase in IL-5 and IL-13 production were observed in the mice fed the TBT diet and treated with TNCB. These findings suggest that the increase in S. aureus and the enhancement of Th2 response induced by TBT exacerbate the AD-like lesions in mice treated with TNCB.

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.

Atopic dermatitis: beyond the itch that rashes

The prevalence of atopic dermatitis is increasing, and more than 50% of children with atopic dermatitis go on to develop asthma and allergies. A better understanding of the underlying immune abnormalities of this complex chronic relapsing skin disease is needed. Although the optimal treatment approach remains to be defined, several recent studies suggest a rationale for using topical calcineurin inhibitors as early intervention and adding topical corticosteroids as rescue therapy if needed.

Analysis of circulating gammadelta T cells in children affected by IgE-associated and non-IgE-associated allergic atopic eczema/dermatitis syndrome

Recent studies have suggested that not only alphabeta(+) T cells, but also the less common gammadelta(+) T cells may play a role as effectors and immunoregolatory cells in the development and perpetuation of allergic inflammation. The objective of this study was to focus on the role of gammadelta(+) T cells in atopic dermatitis (AD), a chronic relapsing inflammatory disease of the skin, often associated with allergic bronchial asthma. The present study employed flow cytometric analysis to compare numbers and phenotypic characteristics of gammadelta(+) T cells in the peripheral blood of children with atopic dermatitis and age-matched healthy controls. The percentage of circulating Vgamma 9Vdelta2(+) T lymphocytes was significantly increased in AD patients with respect to the age-matched controls, with a positive correlation with clinical score severity. The prevalent phenotype in both AD patients and controls was CD45RO(+), with no differences observed in the percentage of Vdelta2(+) CD45RO(+) between these groups. Conversely, memory CD45RO(+) CD62L(+) Vdelta2(+) lymphocytes were significantly lower in AD patients. Furthermore, naive circulating Vdelta2(+) T lymphocytes were significantly lower in AD children than in aged-matched controls. No correlation was observed between circulating Vgamma 9Vdelta2(+) expansion and IgE serum levels. It was concluded that an association exists between the levels of circulating gammadelta(+) T lymphocytes and atopic dermatitis, with a positive correlation with clinical score but no link with IgE serum levels. The pathophysiological role of gammadelta T lymphocytes in atopic dermatitis awaits further investigation.

In vitro culture of skin-homing T lymphocytes from inflammatory skin diseases

We, in this study, describe how T lymphocytes in a skin biopsy can proliferate in vitro for up to 3 months by using T-cell growth factors - interleukin-2 (IL-2) and IL-4 yielding approximately 100-160 million T lymphocytes within 1 month. We established cell lines from three tuberculin skin tests, four positive patch tests, 15 of 16 biopsies from atopic dermatitis (AD), 15 of 19 biopsies from mycosis fungoides (MF), 12 of 24 biopsies from psoriasis vulgaris, which was significantly less than AD (P < 0.05), and with a reduced cumulative number of lymphocytes (P < 0.05). Omitting IL-2 and IL-4 led to immediate halt of proliferation. Blood mononuclear cells from patients and biopsies from healthy persons never gave cell lines. All cells were T lymphocytes expressing CD45RO+, HLA-DR+ and CD150. The CD7 expression was significantly increased in cell lines from AD (P < 0.05). T-cell receptor beta-chain studies by using reverse transcription-polymerase chain reaction showed that all T lymphocytes had access to the skin compartment. Single-stranded conformational analysis showed clonally expanded T cells numbering between 40 and 60 clones. After approximately 2 months of growth, the mean CD4+ : CD8+ ratio was for AD 1.20, MF 0.65 and psoriasis 0.85. Patients with AD treated with cyclosporin-A had almost no growth of CD8+ cells in vitro. Our findings indicate a changed homeostasis among skin-homing lymphocytes for in vitro culture. Our culture system of skin-homing T lymphocytes leads to a prominent cellular expansion allowing for a range of studies of in vivo activated skin T lymphocytes.

Bactericidal activity of flucloxacillin against Staphylococcus aureus in primary keratinocyte cultures of lesional and unaffected skin of patients suffering from atopic dermatitis

More than 90% of patients with atopic dermatitis (AD) are colonized by Staphylococcus aureus. Due to prevalent multi-resistant strains, it is highly difficult to eliminate S. aureus contamination of primary cell cultures of human AD skin by means of the antibiotics commonly used in cell culture. Therefore, an anti-staphylococcal treatment was investigated by which sterile proliferating keratinocyte cultures are attained from lesional and unaffected skin of AD patients by applying flucloxacillin, which in general is systemically used in vivo. The treatment with 1% flucloxacillin for 20 min included both colonized skin samples and contaminated primary cell cultures. In the case of persistent contamination, this step was repeated as often as required until complete decontamination without any cytotoxic indications was achieved. Antibacterial treatment with flucloxacillin permitted the cultivation of sterile, vital, and proliferating primary cultures of human skin keratinocytes from lesional and unaffected skin of AD patients with S. aureus colonization. The method increased the success rate of isolation of AD keratinocytes from 30 to 90%, representing on average 3 vs. 9 successfully isolated, sterile and proliferating cultures out of 10 contaminated skin biopsies, which is comparable to normal human keratinocyte isolation rates.

Evidence for Restricted Vβ Usage in the Leukemic Phase of Cutaneous T Cell Lymphoma

Antibodies directed against the beta chain of the T cell receptor (anti-Vbeta antibodies) are useful to identify the Vbeta repertoire of T cells in various diseases and to quantify numbers of Vbeta-bearing T cells. The goals of this study were to identify Vbeta+ cases of leukemic phase cutaneous T cell lymphoma (CTCL) and to compare the percentage of positive calls with other measures of blood tumor burden, i.e., lymphocyte subsets with a CD4+CD7- and CD4+CD26- phenotype and Sezary cell counts. Thirty-three of 49 (67%) cases of leukemic CTCL reacted with an anti-Vbeta antibody. When combined with reports from the literature, the frequency of Vbeta5 (probably Vbeta5.1) usage was relatively high when compared with Vbeta2 that is also frequently expressed by normal CD4+ T cells. The percentage of Vbeta+ cells correlated to the percentage of CD4+CD7- and CD4+CD26- cells for cases in which the neoplastic cells were deficient in expression of CD7 and CD26, respectively, but not the Sezary cell count. We hypothesize that the increased Vbeta5.1 usage in CTCL may be the result of depletion of Vbeta2 and other Vbeta-bearing T cells by staphylococcal superantigens prior to neoplastic transformation, resulting in a relative increase in the frequency of Vbeta5.1 usage in CTCL.

Microbial colonization and atopic dermatitis

PURPOSE OF REVIEW

Atopic dermatitis is a chronic relapsing, pruritic inflammation of the skin, affecting 10-20% of children and 1-3% adults worldwide, with increasing prevalence in highly industrialized countries. Here we review relevant studies, published since June 2002, about immunological triggers in atopic dermatitis, with emphasis on the role of microbial colonization.

RECENT FINDINGS

During the past 2 years there has been considerable interest in the mechanisms and trigger factors underlying the increased microbial colonization of atopic skin. Staphylococcus aureus appears to play a significant role as it leads to a worsening of disease severity by producing superantigens that induce a strong proliferation of T cells and favour a T helper type 2-like cytokine profile. In addition, different Malassezia species seem to elicit and maintain skin inflammation after sensitization, but the precise immunological pathway has not yet been described. All these microorganisms are not only perceived as aetiological factors but also as agents responsible either for sustained disease activity or resistance to therapy by modulation of the immune response.

SUMMARY

New insights into the important role of microorganisms and their key immunomodulatory pathways in atopic dermatitis may have important implications from a therapeutic point of view because patients with atopic dermatitis may benefit from more than just anti-inflammatory treatment in the future.

Microbial superantigens induce glucocorticoid receptor beta and steroid resistance in a nasal explant model

OBJECTIVE

To study the role of superantigen (SAg) in inducing glucocorticoid (GC) receptor beta and steroid resistance in an explant model of nasal tissue.

METHODS

Nasal tissue was obtained from inferior turbinates of controls and ragweed (RW)-sensitive patients. Tissue samples were incubated with SAg of staphylococcal enterotoxin B. In addition, tissue samples from RW-sensitive patients were incubated with RW allergen in the presence and absence of both SAg and dexamethasone (DEX). The expression of GC receptor beta was assessed by immunocytochemistry. The expression of interleukin (IL)-2 and IL-4 mRNA was assessed by in situ hybridization.

RESULTS

SAg induced an increase in the expression of GC receptor beta in atopic tissue and to a lesser extent in nonatopic tissue. The most significant induction of GC receptor beta was observed in response to SAg and RW in atopic tissue. Stimulation of atopic tissue with RW alone and SAg alone induced IL-4 and IL-2 mRNA, respectively. Incubation of atopic tissue with both SAg and RW induced both IL-2 and IL-4 mRNA. The increase in IL-4 mRNA expression was blunted by the addition of DEX to atopic tissue stimulated with RW alone but not to tissue stimulated by both RW and SAg.

CONCLUSION

Our results demonstrate that SAgs induce steroid resistance in atopic nasal explant tissue by up-regulating the expression of GC receptor beta. Furthermore, we have shown that the up-regulation of GC receptor beta is a local event that is associated with the coexpression of IL-2 and IL-4 mRNA.

Secondary infections in patients with atopic dermatitis

Clinicians have long since been aware that bacteria and other microorganisms play a role in the etiology of atopic dermatitis. Indeed, the immunological profile of atopy favors colonization by Staphylococcus aureus, and the bacteria are present in most patients with atopic dermatitis, even in the absence of skin lesions. Clinical signs of impetiginization, such as weeping and crusting, periauricular fissuration, or small superficial pustules are a sensitive indicator that the numbers of S. aureus may have increased and a clinical indication of secondary infected dermatitis. However, recent research that has focussed on the role of S. aureus in atopic dermatitis, offers a reversed perspective, by presenting evidence that the underlying pathology of atopic dermatitis, i.e. an alteration of the skin barrier and inflammation of the upper dermis, depends itself on the presence of an infectious process. In other words, secondary infection with S. aureus emerges as a cause of atopic dermatitis. Secondary infections due to fungi have, comparatively, received less attention, but there is evidence for a role for Malassezia spp. as a factor in dermatitis with a head and neck distribution pattern. Viral infections, such as herpes simplex virus, and mixed infections of intertriginous spaces, may complicate an underlying atopic dermatitis, but are not perceived as etiologic factors. Recent research has greatly contributed to our understanding of the pathophysiological potential of S.aureus superantigens in atopic dermatitis, suggesting that antibiotic therapy might be an important element in the therapeutic management of atopic dermatitis. At present, however, the clinical evidence is scarce with regards to demonstrating a clear advantage of combined anti-inflammatory and antibiotic treatment, compared with anti-inflammatory treatment alone. If there is a consensus that the presence of clinically infected lesions in atopic dermatitis warrants a course of specific antibiotic topical therapy, the clinical benefit of antibiotic agents in apparently uninfected atopic dermatitis, as present in the majority of patients, remains an open question.Moreover, the impact of adjuvant skin care on the cutaneous microflora needs to be quantified in order to properly assess the role of specific antibiotic therapy in clinically uninfected atopic dermatitis. In the meantime, secondary infections in atopic dermatitis remain a secondary problem in clinical atopic dermatitis management, and specific anti-infective therapy remains a method of fine-tuning for optimizing individual atopic dermatitis treatment.

Epicutaneous sensitization with superantigen induces allergic skin inflammation

BACKGROUND

Atopic dermatitis (AD) is characterized by skin infiltration with eosinophils and lymphocytes and expression of Th2 cytokines in acute skin lesions. The skin of patients with AD is frequently colonized with enterotoxin-secreting strains of Staphylococcus aureus. Staphylococcal enterotoxins have been implicated in the exacerbations of the inflammatory skin lesions in patients with AD.

OBJECTIVE

We sought to determine whether epicutaneous (EC) sensitization of mice with staphylococcal enterotoxin B (SEB) results in allergic skin inflammation.

METHODS

BALB/c mice were EC-sensitized with SEB. Their skin was examined for allergic inflammation and cytokine expression, and their splenocytes were examined for cytokine secretion in response to SEB.

RESULTS

EC sensitization with SEB elicited a local, cutaneous, inflammatory response characterized by dermal infiltration with eosinophils and mononuclear cells and increased mRNA expression of the Th2 cytokine IL-4 but not of the Th1 cytokine IFN-gamma. EC-sensitized mice mounted a systemic Th2 response to SEB evidenced by elevated total and SEB-specific IgG1 and IgE. Although EC sensitization with SEB resulted in selective depletion of SEB-specific T-cell receptor Vbeta8+ cells from the spleen and sensitized skin, splenocytes from SEB-sensitized mice secreted relatively more IL-4 and less IFN-gamma than did saline-sensitized controls, consistent with Th2 skewing of the systemic immune response to the superantigen.

CONCLUSION

These results suggest that EC exposure to superantigens skews the immune response toward Th2 cells, leading to allergic skin inflammation and increased IgE synthesis that are characteristic of AD.

Prebiotics in infant milk formulas: new perspectives

In recent years it has become accepted that healthy human intestinal microflora may play an important part in priming the infants' systemic and mucosal immunity. Dietary modulation of the gut microbiota is a topical area of nutritional sciences and the main focus of many current functional foods such as non-digestible oligosaccharides (NDOs). Fructo-oligosaccharides (FOS) and trans-beta-galacto-oligosaccharides (TOS) have been claimed to benefit the health of the colon by selectively stimulating the growth of bifidobacteria and lactobacilli (prebiotic effect). It could be of clinical interest to manipulate colonic flora because it is supposed that specific bacteria in the gut microbial microflora could promote potentially antiallergenic processes and play a key part in atopic disease prevention. Supporting this view is the finding that analysis of the composition of the intestinal bacterial populations showed different microbial patterns between healthy and allergic individuals. Assuming that non-digestible TOS and FOS can affect the intestinal ecosystem beneficially, the opportunity for gut flora manipulation arises in bottle-fed infants. New preterm and term infant milk formulas, supplemented with a mixture of TOS and FOS as prebiotic ingredients induced a significantly higher colonization of bifidobacteria and lactobacilli. In the future, selective manipulation of the intestinal microbiota might be an approach to novel prophylactic and therapeutic intervention strategies of atopy, by redirecting allergic Th-2 responses in favour of Th-1 responses.

High prevalence of superantigens associated with the egc locus in Staphylococcus aureus isolates from patients with atopic eczema

The present study was aimed at identifying a possible correlation between disease severity and colonization with superantigen-producing Staphylococcus aureus strains in patients with atopic eczema. To this end, Staphylococcus aureus strains from 91 patients with atopic eczema were screened for various staphylococcal superantigens such as SEA, SEB, SEC, SED, TSST1, the recently described enterotoxin gene cluster egc (which encodes the enterotoxins SEG, SEI, SEK, SEM, and SEO), and the see, seh, and sej loci. Swabs were taken from seven different sites in each patient. The rate of colonization with Staphylococcus aureus was 87.9%. Of those patients colonized, 35% were colonized with more than one different strain. Of the 120 genetically different strains investigated, the egc locus was found in 48.3% and the sej locus in 7.5%. The see and seh loci were not found in any strain. The presence of the classical superantigens SEA-SED or TSST1 was found in 38.3%. Overall, 71.3% of the Staphylococcus aureus-positive patients harbored at least one superantigen-producing strain on their skin. There was no difference in the prevalence of superantigens between atopic eczema patients and healthy volunteers. Moreover, there was no difference in the extent of disease expression between patients colonized by superantigen-positive Staphylococcus aureus strains and those with superantigen-negative strains as measured by the SCORAD system. However, patients colonized with Staphylococcus aureus had a significantly higher SCORAD score than those not colonized.

Alteration in the production of IL-10 and IL-12 and aberrant expression of CD23, CD83 and CD86 by monocytes or monocyte-derived dendritic cells from atopic dermatitis patients

Atopic dermatitis (AD) is characterized by the presence of Th2-type cells in the skin infiltration as well as in the peripheral blood, although a predominant infiltration of interferon-gamma (IFN-gamma)-producing cells is also reported in the chronic skin lesions of AD. Recently it has become clear that the development of Th1 or Th2 is strongly influenced by factors produced by the antigen presenting cells (APCs). To clarify whether APCs from AD patients play a favorable role in the differentiation of Th2 cells, we compared the production of cytokines and the expression of co-stimulatory molecules by monocytes (MOs) and monocyte-derived DCs (MoDCs) after stimulations with various reagents between 13 AD patients and 13 age-matched healthy controls. We examined their production of IL-1 beta, IL-10, IL-12p40, and IL-12p70, and their expression of CD23, CD40, CD54, CD80, CD83, CD86 and HLA-DR. We stimulated them with superantigens, lipopolysaccharide (LPS), agonistic anti-CD40 antibody, phytohemagglutinins (PHA), IL-1beta/TNF-alpha, IL-4, or IFN-gamma. The following results were obtained (1): IL-10 production was significantly enhanced in AD MOs after LPS stimulation. In contrast, IL-12p40 production was significantly lower in AD MOs than in HC MOs after a variety of stimulations (2). IL-12p40 was also significantly lower in AD MoDCs after LPS stimulation (3). The induction of CD23 with IL-4 was significantly higher in AD MOs. and finally (4), AD MoDCs augmented the expression of CD83, CD86, and HLA-DR less significantly than HC MoDCs after anti-CD40 Ab stimulation. These data indicate that AD APCs show some responses different from those observed in HC APCs after several stimulations, such as LPS, IL-1 beta/TNF-alpha, IL-4, or anti-CD40 Ab, and that these responses might play a role in the polarizing process of helper T cells into Th2 cells as recognized in AD patients.

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.

Characterization of two novel pyrogenic toxin superantigens made by an acute rheumatic fever clone of Streptococcus pyogenes associated with multiple disease outbreaks

The pathogenesis of acute rheumatic fever (ARF) is poorly understood. We identified two contiguous bacteriophage genes, designated speL and speM, encoding novel inferred superantigens in the genome sequence of an ARF strain of serotype M18 group A streptococcus (GAS). speL and speM were located at the same genomic site in 33 serotype M18 isolates, and no nucleotide sequence diversity was observed in the 33 strains analyzed. Furthermore, the genes were absent in 13 non-M18 strains tested. These data indicate a recent acquisition event by a distinct clone of serotype M18 GAS. speL and speM were transcribed in vitro and upregulated in the exponential phase of growth. Purified SpeL and SpeM were pyrogenic and mitogenic for rabbit splenocytes and human peripheral blood mononuclear cells in picogram amounts. SpeL preferentially expanded human T cells expressing T-cell receptors Vbeta1, Vbeta5.1, and Vbeta23, and SpeM had specificity for Vbeta1 and Vbeta23 subsets, indicating that both proteins had superantigen activity. SpeL was lethal in two animal models of streptococcal toxic shock, and SpeM was lethal in one model. Serologic studies indicated that ARF patients were exposed to serotype M18 GAS, SpeL, and SpeM. The data demonstrate that SpeL and SpeM are pyrogenic toxin superantigens and suggest that they may participate in the host-pathogen interactions in some ARF patients.

Characterization of a novel staphylococcal enterotoxin-like superantigen, a member of the group V subfamily of pyrogenic toxins

Staphylococcus aureus is an important human pathogen, causing a variety of diseases. Major virulence factors of this organism include staphylococcal enterotoxins (SEs) that cause food poisoning and toxic shock syndrome. Our study identified a novel enterotoxin-like protein that is a member of the new subfamily (group V) of pyrogenic toxin superantigens (PTSAgs) and examined its biochemical and immunobiological properties. The gene encoding the SE-like protein is directly 5' of another recently identified PTSAg, SEK. The SE-like protein had a molecular weight of 26000 and an experimentally determined isoelectric point between 7.5 and 8.0. We demonstrated that the PTSAg had many of the biological activities associated with SEs, including superantigenicity, pyrogenicity, and ability to enhance endotoxin shock, but lacked both lethality in rabbits when administered in subcutaneous miniosmotic pumps and emetic activity in monkeys. Recombinant protein stimulated human CD4 and CD8 T cells in a T cell receptor variable region, beta chain (TCRVbeta) specific manner. T cells bearing TCRVbeta 2, 5.1, and 21.3 were significantly stimulated.

Atopic dermatitis and fungi

Atopic dermatitis (AD) is a chronic, itching, inflammatory skin disease which is associated with asthma and/or hay fever and a familial occurrence of these conditions. Genetic factors are important in the development of AD, but the exact hereditary pathway is still unknown. Dry skin and the weakened barrier function in patients with AD is very important for the patient's reactions to irritants and other external trigger factors including microorganisms. The standard treatments are topical corticosteroids, topical immunomodulating agents, and emollients. If AD cannot be controlled by this type of treatment, systemic immunomodulating agents may be used. UVB, UVA, or psoralen-UVA may also be used for widespread severe lesions. However, some patients do not respond to these standard treatment, and then it is important to consider the role of microorganisms, house dust mites or food. The role of the Malassezia yeasts in AD, especially AD located to the head and neck region, is now documented in several papers. There are also several papers indicating the role of Candida as an aggravating factor in AD. Patients with AD also develop chronic dermatophyte infections more easily, and patients with AD and chronic dermatophyte infections may show improvement in their AD when treated with antifungal drugs.

Hypoproteinemia in severe childhood atopic dermatitis: a serious complication

As a complication of atopic dermatitis (AD), the incidence of hypoproteinemia is increasing among infants with severe AD in Japan. It can be a life-threatening condition owing to hypovolemic shock as a result of hypoproteinemia and vascular infarction as a result of thrombocythemia. However, the pathophysiology of this condition remains unclear. The objectives of the present study were two-fold. The first objective was to determine the main route of protein loss, i.e. through the damaged skin or the gastrointestinal tract, or as a result of insufficient food intake. The second objective was to identify whether allergy or infection was the cause of severe skin inflammation. Fifteen patients with AD were enrolled who had serum protein levels of 3.2-5.8 g/dl. Specific immunoglobulin E (IgE) and skin test to allergens, stool eosinophils, alpha1-antitrypsin clearance, skin Staphylococcus aureus colonization and superantigens (SAgs) produced by the organism, serum SAg-specific IgE antibodies, serum interleukin (IL)-5, IL-6, IL-12, and interferon-gamma (IFN-gamma) were evaluated. Prominent serous skin discharge was seen in all of the patients and was found to have almost the same protein concentration as serum. Marked thrombocytosis, with a maximum of 1,060 x 103/ml, was seen. Skin culture revealed S. aureus colonization in all patients. SAg-producing S. aureus were found in 84.6% of the patients. The concentration of serum IL-5 was significantly increased and correlated well with the blood eosinophil count. Hence, the main route of protein loss was believed to be through damaged skin. The cause of severe inflammation was thought to be a combination of allergic inflammation and skin colonization by SAg-producing S. aureus. Serum cytokines showed a T helper 2 (Th2) T-cell-mediated pattern. To prevent hypovolemic shock, vascular occlusion, and growth retardation, it is of vital importance to diagnose hypoproteinemia at an early stage and start appropriate therapy.

Proteasome inhibition reduces superantigen-mediated T cell activation and the severity of psoriasis in a SCID-hu model

There is increasing evidence that bacterial superantigens contribute to inflammation and T cell responses in psoriasis. Psoriatic inflammation entails a complex series of inductive and effector processes that require the regulated expression of various proinflammatory genes, many of which require NF-kappa B for maximal trans-activation. PS-519 is a potent and selective proteasome inhibitor based upon the naturally occurring compound lactacystin, which inhibits NF-kappa B activation by blocking the degradation of its inhibitory protein I kappa B. We report that proteasome inhibition by PS-519 reduces superantigen-mediated T cell-activation in vitro and in vivo. Proliferation was inhibited along with the expression of very early (CD69), early (CD25), and late T cell (HLA-DR) activation molecules. Moreover, expression of E-selectin ligands relevant to dermal T cell homing was reduced, as was E-selectin binding in vitro. Finally, PS-519 proved to be therapeutically effective in a SCID-hu xenogeneic psoriasis transplantation model. We conclude that inhibition of the proteasome, e.g., by PS-519, is a promising means to treat T cell-mediated disorders such as psoriasis.

Pathophysiologic mechanisms in atopic dermatitis

Atopic dermatitis is a common, chronic inflammatory skin disease that frequently predates the development of asthma and/or allergic rhinoconjunctivitis. Recent studies have provided new insights into how the complex interrelationship of genetic, environmental, and immunologic factors may contribute to the development of atopic dermatitis. This article examines some of the factors involved in chronic cutaneous inflammation in this disease. Greater understanding of the mechanisms that underlie the pathophysiology of atopic dermatitis may lead to improved treatment strategies for this increasingly common skin disease.