Analysis of CD25hiCD4+ "regulatory" T-cell subtypes in atopic dermatitis reveals a novel T(H)2-like population

Control of Asthma and Allergy by Regulatory T Cells

BACKGROUND

Epithelial barriers, such as the lungs and skin, face the challenge of providing the tissues' physiological function and maintaining tolerance to the commensal microbiome and innocuous environmental factors while defending the host against infectious microbes. Asthma and allergic diseases can result from maladaptive immune responses, resulting in exaggerated and persistent type 2 immunity and tissue inflammation.

SUMMARY

Among the diverse populations of tissue immune cells, CD4+ regulatory T cells (Treg cells) are central to controlling immune responses and inflammation and restoring tissue homeostasis. Humans and mice that are deficient in Treg cells experience extensive inflammation in their mucosal organs and skin. During past decades, major progress has been made toward understanding the immunobiology of Treg cells and the molecular and cellular mechanisms that control their differentiation and function. It is now clear that Treg cells are not a single cell type and that they demonstrate diversity and plasticity depending on their differentiation stages and tissue environment. They could also take on a proinflammatory phenotype in certain conditions.

KEY MESSAGES

Treg cells perform distinct functions, including the induction of immune tolerance, suppression of inflammation, and promotion of tissue repair. Subsets of Treg cells in mucosal tissues are regulated by their differentiation stage and tissue inflammatory milieu. Treg cell dysfunction likely plays roles in persistent immune responses and tissue inflammation in asthma and allergic diseases.

Regulatory T-cell dysfunction and cutaneous exposure to Staphylococcus aureus underlie eczema in DOCK8 deficiency

BACKGROUND

Dedicator of cytokinesis 8 (DOCK8)-deficient patients have severe eczema, elevated IgE, and eosinophilia, features of atopic dermatitis (AD).

OBJECTIVE

We sought to understand the mechanisms of eczema in DOCK8 deficiency.

METHODS

Skin biopsy samples were characterized by histology, immunofluorescence microscopy, and gene expression. Skin barrier function was measured by transepidermal water loss. Allergic skin inflammation was elicited in mice by epicutaneous sensitization with ovalbumin (OVA) or cutaneous application of Staphylococcus aureus.

RESULTS

Skin lesions of DOCK8-deficient patients exhibited type 2 inflammation, and the patients' skin was colonized by Saureus, as in AD. Unlike in AD, DOCK8-deficient patients had a reduced FOXP3:CD4 ratio in their skin lesions, and their skin barrier function was intrinsically intact. Dock8-/- mice exhibited reduced numbers of cutaneous T regulatory (Treg) cells and a normal skin barrier. Dock8-/- and mice with an inducible Dock8 deletion in Treg cells exhibited increased allergic skin inflammation after epicutaneous sensitization with OVA. DOCK8 was shown to be important for Treg cell stability at sites of allergic inflammation and for the generation, survival, and suppressive activity of inducible Treg cells. Adoptive transfer of wild-type, but not DOCK8-deficient, OVA-specific, inducible Treg cells suppressed allergic inflammation in OVA-sensitized skin of Dock8-/- mice. These mice developed severe allergic skin inflammation and elevated serum IgE levels after topical exposure to Saureus. Both were attenuated after adoptive transfer of WT but not DOCK8-deficient Treg cells.

CONCLUSION

Treg cell dysfunction increases susceptibility to allergic skin inflammation in DOCK8 deficiency and synergizes with cutaneous exposure to Saureus to drive eczema in DOCK8 deficiency.

IL-4-induced decrease in both the number and CTLA-4 expression of Treg impairs suppression of Th2 type inflammation in severe atopic dermatitis

BACKGROUND

Treg plays a pivotal role in the suppression of Th2 cell and the maintenance of immune homeostasis. The precise molecular mechanism underlying the disruption of Treg suppression of Th2 cell and the promotion of Th2 type inflammation in allergic diseases remains elusive.

OBJECTIVE

This study aims to investigate the molecular mechanism underlying quantitative and functional changes of Treg in AD.

METHODS

The molecular mechanism was investigated using flow cytometry, mRNA sequencing, co-culture experiments, co-immunoprecipitation, chromatin immunoprecipitation, and bisulfite sequencing in vitro or in AD mice model and patients with AD.

RESULTS

Increased proportion of Treg was detected in mild and moderate AD. Conversely, characteristic decrease in both the number and CTLA-4 expression of Treg was relevant to serum IL-4 level in severe AD patients, which was verified under a high concentration of IL-4 treatment in vitro. The underlying mechanism is that IL-4/pSTAT6 pathway recruits DNMT1 and HDAC2 to inhibit transcriptional regulation of Foxp3 and CTLA-4 loci. High level of IL-4 impaired the suppression of Treg against Th2 cell differentiation mediated by CTLA-4, and blockade of IL-4Rα signaling in Treg restored Treg number and suppression of Th2 cell in AD model mice and patients with AD.

CONCLUSION

The number of Treg is relevant to stratification of severity and serum IL-4 level in patients with AD. Abnormal high level of IL-4 epigenetically triggers a decrease in both the number and CTLA-4 expression of Treg. The reduced expression of CTLA-4 on Treg induced by IL-4 impairs suppression of Th2 cell differentiation.

The Role of Regulatory T Cells in Allergic Diseases: Collegium Internationale Allergologicum (CIA) Update 2024

BACKGROUND

Allergy represents a major health problem of increasing prevalence worldwide with a high socioeconomic impact. Our knowledge on the molecular mechanisms underlying allergic diseases and their treatments has significantly improved over the last years. The generation of allergen-specific regulatory T cells (Tregs) is crucial in the induction of healthy immune responses to allergens, preventing the development and worsening of allergic diseases.

SUMMARY

In the last decades, intensive research has focused on the study of the molecular mechanisms involved in Treg development and Treg-mediated suppression. These mechanisms are essential for the induction of sustained tolerance by allergen-specific immunotherapy (AIT) after treatment discontinuation. Compelling experimental evidence demonstrated altered suppressive capacity of Tregs in patients suffering from allergic rhinitis, allergic asthma, food allergy, or atopic dermatitis, as well as the restoration of their numbers and functionality after successful AIT.

KEY MESSAGE

The better understanding of the molecular mechanisms involved in Treg generation during allergen tolerance induction might well contribute to the development of novel strategies for the prevention and treatment of allergic diseases.

Regulatory T cells in allergic inflammation

Regulatory T (Treg) cells maintain immune tolerance to allergens at the environmental interfaces in the airways, skin and gut, marshalling in the process distinct immune regulatory circuits operative in the respective tissues. Treg cells are coordinately mobilized with allergic effector mechanisms in the context of a tissue-protective allergic inflammatory response against parasites, toxins and potentially harmful allergens, serving to both limit the inflammation and promote local tissue repair. Allergic diseases are associated with subverted Treg cell responses whereby a chronic allergic inflammatory environment can skew Treg cells toward pathogenic phenotypes that both perpetuate and aggravate disease. Interruption of Treg cell subversion in chronic allergic inflammatory conditions may thus provide novel therapeutic strategies by re-establishing effective immune regulation.

Gene signature from cutaneous autoimmune diseases provides potential immunotherapy-relevant biomarkers in melanoma

Immune checkpoint inhibitors (ICIs) are promising agents for treating melanoma. Given that autoimmune skin diseases exhibit hyper immune reaction, investigation of immune cells from autoimmune skin disease is crucial to validate the effectiveness of ICIs in melanoma treatment. We employed multipanel markers to predict the response to immune checkpoint inhibitors by characterizing the gene expression signatures of skin immune cells in systemic lupus erythematosus (SLE), atopic dermatitis (AD), and psoriasis (PS). By analyzing single-cell RNA sequencing data from each dataset, T cell gene signatures from autoimmune skin diseases exhibit a complex immune response in tumors that responded to immunotherapy. Based on that CD86 and CD80 provide essential costimulatory signals for T cell activation, we observed that interaction of CD86 signaling has been enhanced in the T cells of patients with SLE, AD, and PS. Our analysis revealed a common increase in CD86 signals from dendritic cells (DCs) to T cells in patients with SLE, AD, and PS, confirming that dendritic cells produce pro-inflammatory cytokines to activate T cells. Thus, we hypothesize that T cell gene signatures from autoimmune skin diseases exhibit a pro-inflammatory response and have the potential to predict cancer immunotherapy. Our study demonstrated that T cell gene signatures derived from inflammatory skin diseases, particularly SLE and PS, hold promise as potential biomarkers for predicting the response to immune checkpoint blockade therapy in patients with melanoma. Our data provide an understanding of the immune-related characteristics and differential gene expression patterns in autoimmune skin diseases, which may represent promising targets for melanoma immunotherapy.

Antigen-specific T cell balance reveals Why patients with atopic dermatitis fail to achieve immune tolerance

The number of regulatory T cells (Tregs) and how they behave in the pathogenesis of atopic dermatitis (AD) are still controversial. We identified and quantified Tregs, mite-specific Tregs, and mite-specific effector T cells (Teffs) in patients with AD and healthy controls (HCs). We collected peripheral blood and analyzed the cells using flow cytometry after stimulation with mite antigens. Mite-specific Tregs and mite-specific Teffs were recognized by the expression of CD137 and CD154, respectively. Patients with AD had more Tregs than HCs; however, when focusing on a single antigen, the ratio of mite-specific Tregs/Teffs was lower in patients with AD than in HCs. Furthermore, the mite-specific Teffs in patients with AD were more likely to produce proinflammatory cytokines interleukin (IL)-4 and IL-13. This Teff-dominant imbalance is thought to be the cause of development of atopic status in patients with AD without immune tolerance.

T cell co-stimulatory and co-inhibitory pathways in atopic dermatitis

The use of immune checkpoint inhibitors (ICIs) targeting the T cell inhibitory pathways has revolutionized cancer treatment. However, ICIs might induce progressive atopic dermatitis (AD) by affecting T cell reactivation. The critical role of T cells in AD pathogenesis is widely known. T cell co-signaling pathways regulate T cell activation, where co-signaling molecules are essential for determining the magnitude of the T cell response to antigens. Given the increasing use of ICIs in cancer treatment, a timely overview of the role of T cell co-signaling molecules in AD is required. In this review, we emphasize the importance of these molecules involved in AD pathogenesis. We also discuss the potential of targeting T cell co-signaling pathways to treat AD and present the unresolved issues and existing limitations. A better understanding of the T cell co-signaling pathways would aid investigation of the mechanism, prognosis evaluation, and treatment of AD.

Osteopontin and Regulatory T Cells in Effector Phase of Allergic Contact Dermatitis

Studies have shown that osteopontin (OPN) and regulatory T cells play a role in allergic contact dermatitis (ACD), but the mechanisms responsible for their function are poorly understood. The study aimed to determine CD4 T lymphocytes producing intracellular osteopontin (iOPN T cells) and assess the selected T lymphocyte subsets including regulatory T cells in the blood of patients with ACD. Twenty-six patients with a disseminated form of allergic contact dermatitis and 21 healthy controls were enrolled in the study. Blood samples were taken twice: in the acute phase of the disease and during remission. The samples were analyzed by the flow cytometry method. Patients with acute ACD showed significantly higher percentage of iOPN T cells compared with healthy controls which persisted during remission. An increase in the percentage of CD4CD25 and a reduced percentage of regulatory T lymphocytes (CD4CD25highCD127low) were also found in the patients with acute stage of ACD. The percentage of CD4CD25 T lymphocytes showed a positive correlation with the EASI index. The increase in the iOPN T cells can indicate their participation in acute ACD. The decreased percentage of regulatory T lymphocytes in the acute stage of ACD may be related to the transformation of Tregs into CD4CD25 T cells. It may also indicate their increased recruitment to the skin. The positive correlation between the percentage of CD4CD25 lymphocytes and the EASI index may be indirect evidence for the importance of activated lymphocytes-CD4CD25 in addition to CD8 lymphocytes as effector cells in ACD.

Immunization with a Pneumococcal pep27 Mutant Strain Alleviates Atopic Dermatitis through the Upregulation of Regulatory T-Cell Activity and Epithelial Barrier Function and Suppressing TSLP Expression

Atopic dermatitis (AD) is an inflammatory disease driven in part by type 2 helper T (Th2) cytokines and skin barrier disruption alleviating the entry of allergens. Thymic stromal lymphopoietin (TSLP), an epithelial cell‒derived cytokine, is known to aggravate AD symptoms by activating Th2. In addition, regulatory T cells (Tregs) inhibit inflammatory cells such as Th2. However, the relationship between TSLP and Tregs in AD is unclear. A murine dermatitis model was induced by applying oxazolone to the ear skin of mice. Prophylactic and therapeutic responses were analyzed by immunizing mice intranasally with a pneumococcal pep27 mutant (Δpep27 mutant), attenuated strain by reducing the virulence of a pathogen. Intranasal immunization with a pneumococcal pep27 mutant could elicit anti-inflammatory Treg-relevant factors and epithelial barrier genes (loricrin, involucrin, filaggrin, and small proline-rich repeat proteins). Thus, pneumococcal pep27-mutant immunization suppressed epidermal collapse, IgE, TSLP, and upregulation of Th2 expression by upregulating Treg activity. In contrast, Treg inhibition aggravated AD symptoms through the upregulation of TSLP and Th2 and the repression of epithelial barrier function compared with that of the noninhibited pneumococcal Δpep27-mutant group. Taken together, immunization with pneumococcal Δpep27 mutant upregulated Treg and epithelial barrier function and inhibited TSLP and Th2 to relieve AD symptoms.

The expanding impact of T-regs in the skin

As the interface between the body and the environment, the skin functions as the physical barrier against external pathogens and toxic agents. In addition, the skin is an immunologically active organ with a plethora of resident adaptive and innate immune cells, as well as effector molecules that provide another layer of protection in the form of an immune barrier. A major subpopulation of these immune cells are the Foxp3 expressing CD4 T cells or regulatory T cells (T-regs). The canonical function of T-regs is to keep other immune cells in check during homeostasis or to dissipate a robust inflammatory response following pathogen clearance or wound healing. Interestingly, recent data has uncovered unconventional roles that vary between different tissues and we will highlight the emerging non-lymphoid functions of cutaneous T-regs. In light of the novel functions of other immune cells that are routinely being discovered in the skin, their regulation by T-regs implies that T-regs have executive control over a broad swath of biological activities in both homeostasis and disease. The blossoming list of non-inflammatory functions, whether direct or indirect, suggests that the role of T-regs in a regenerative organ such as the skin will be a field ripe for discovery for decades to come.

Cytokine-Mediated Crosstalk Between Keratinocytes and T Cells in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by barrier dysfunction, dysregulated immune response, and dysbiosis with increased Staphylococcus aureus colonization. Infiltration of various T helper cell subsets into lesional skin and subsequent cytokine release are a hallmark of AD. Release of cytokines by both T cells and keratinocytes plays a key role in skin inflammation and drives many AD features. This review aims to discuss cytokine-mediated crosstalk between T cells and keratinocytes in AD pathogenesis and the potential impact of virulence factors produced by Staphylococcus aureus on these interactions.

Expression of Helper and Regulatory T Cells in Atopic Dermatitis: A Meta-Analysis

BACKGROUND

Atopic dermatitis (AD) is a common inflammatory skin disease, with the incidence peaks in infancy. A meta-analysis was performed to assess the levels of T helper type 22 (Th22) cells, T helper type 17 (Th17) cells, interleukin (IL)-17, and Tregs in peripheral blood of patients with AD.

METHODS

A comprehensive literature search was performed in PubMed, Embase, China National Knowledge Internet, and Wan-fang Data from the day of inception of this study to July 2021. Two authors independently extracted the data, which were pooled and calculated using Stata software version 15.

RESULTS

A total of eight studies met the inclusion criteria. Compared with control group, patients with AD had an increased proportion of Th22 cells [weighted mean difference (WMD) = 2.07, 95% CI (1.33, 2.81), p < 0.001], Th17 cells [WMD = 1.04, 95% CI [0.66, 1.43], p < 0.001], IL-17 [WMD = 17.56, 95% CI (11.1, 24.03), p < 0.001], and a decreased proportion of Tregs [WMD = -2.49, 95% CI (-2.93, -2.05), p < 0.001] in peripheral blood. The subgroup analysis showed that patients with higher disease severity had higher levels of Th22 [mild: WMD = 1.33, 95% CI (1.24, 1.41), p < 0.001; moderate: WMD = 1.41, 95% CI (1.36, 1.54), p < 0.001; severe: WMD = 3.46, 95% CI (3.34, 2.81), p < 0.001] and lower levels of Tregs [mild: WMD = -1.43, 95% CI (-1.75, -1.11), p < 0.001; moderate: WMD = -2.16, 95% CI (-2.46, -1.86), p < 0.001; severe: WMD = -2.96, 95% CI (-3.25, -2.67), p < 0.001] in peripheral blood compared to healthy controls.

CONCLUSION

The random effect model of the meta-analysis showed patients with AD had an increased proportion of Th22 cells, Th17 cells, and IL-17, whereas a decreased proportion of Tregs was found in peripheral blood. The results demonstrated that Th22 cells, Th17 cells, IL-17, and Tregs may be involved in the pathogenic mechanisms of AD.

Persistence of mature dendritic cells, TH2A, and Tc2 cells characterize clinically resolved atopic dermatitis under IL-4Rα blockade

Therapeutic options for autoimmune diseases typically consist of broad and targeted immunosuppressive agents. However, sustained clinical benefit is rarely achieved, as the disease phenotype usually returns after cessation of treatment. To better understand tissue-resident immune memory in human disease, we investigated patients with atopic dermatitis (AD) who underwent short-term or long-term treatment with the IL-4Rα blocker dupilumab. Using multi-omics profiling with single-cell RNA sequencing and multiplex proteomics, we found significant decreases in overall skin immune cell counts and normalization of transcriptomic dysregulation in keratinocytes consistent with clearance of disease. However, we identified specific immune cell populations that persisted for up to a year after clinical remission while being absent from healthy controls. These populations included LAMP3 + CCL22+ mature dendritic cells, CRTH2 + CD161 + T helper ("TH2A") cells, and CRTAM + cytotoxic T cells, which expressed high levels of CCL17 (dendritic cells) and IL13 (T cells). TH2A cells showed a characteristic cytokine receptor constellation with IL17RB, IL1RL1 (ST2), and CRLF2 expression, suggesting that these cells are key responders to the AD-typical epidermal alarmins IL-25, IL-33, and TSLP, respectively. We thus identified disease-linked immune cell populations in resolved AD indicative of a persisting disease memory, facilitating a rapid response system of epidermal-dermal cross-talk between keratinocytes, dendritic cells, and T cells. This observation may help to explain the disease recurrence upon termination of immunosuppressive treatments in AD, and it identifies potential disease memory-linked cell types that may be targeted to achieve a more sustained therapeutic response.

Increased Frequency of CTLA-4 and PD-1 Expressing Regulatory T Cells and Basophils With an Activating Profile in Infants With Moderate-to-Severe Atopic Dermatitis Hypersensitized to Food Allergens

Background: Infants with severe atopic dermatitis (AD) may be sensitized to foods that have not been introduced into their diet, posing a risk for developing an immediate hypersensitivity reaction on the first exposure to the food to which they are sensitized. The aim of this work was to perform an analysis of the sensitization profile in infants with moderate-to-severe AD and to identify cellular and molecular markers for food allergy (FA). Methods: Blood samples from healthy donors and children with moderate-to-severe AD were studied. Specific IgE to several allergens were determined using ImmunoCAP FEIA system and ISAC technology. Furthermore, using flow cytometry-based studies, basophils and regulatory T (Treg) cells were phenotypically characterized. Results: 90% of children with AD were sensitized to food antigens before introducing them into the diet, and 100% developed FA. Phenotypic analysis showed a significantly higher percentage of CTLA-4 and PD-1 expressing Treg cells in AD patients than in healthy controls. Basophils from patients exhibited a marked reduction in the expression of CD300a, higher expression of FcεRI and CXCR4, and to some extent higher expression of CD63 and CD300c. Conclusions: Infants with moderate-to-severe AD are at high risk of being sensitized to food allergens. Therefore, to avoid allergic reactions, broad-spectrum sensitization studies are necessary before introducing complementary diet. Increased expression of CTLA-4 and PD-1 suggests greater suppressive potential of Treg cells in infants with AD than healthy controls. Furthermore, our results suggest a role for CD300 molecules on circulating basophils as possible biomarkers for FA susceptibility.

Regulatory T cells in inflammatory skin disease: from mice to humans

The skin is the largest organ in the body and one of the primary barriers to the environment. In order to optimally protect the host, the skin is home to numerous immune cell subsets that interact with each other and other non-immune cells to maintain organ integrity and function. Regulatory T cells (Tregs) are one of the largest immune cell subsets in skin. They play a critical role in regulating inflammation and facilitating organ repair. In doing so, they adopt unique and specialized tissue-specific functions. In this review, we compare and contrast the role of Tregs in cutaneous immune disorders from mice and humans, with a specific focus on scleroderma, alopecia areata, atopic dermatitis, cutaneous lupus erythematosus and psoriasis.

In vitro Conversion into CD4+CD25+Foxp3+ Induced Regulatory T Cells Is Reduced in Atopic Dermatitis Patients

BACKGROUND

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases, with an increasing incidence in clinical practice. AD models have demonstrated that TGF-β signaling is compromised in regulatory T cells (Tregs).

OBJECTIVES

This study aimed to investigate the TGF-β-dependent in vitro conversion of CD4+CD25- T cells derived from AD-patients into CD4+CD25+Foxp3+ induced Tregs (iTregs) in comparison to healthy controls.

METHODS

To analyze in vitro iTreg conversion, human CD4+CD25- T cells were cultured on anti-CD3-coated plates in the presence of TGF-β and IL-2 for up to 3 days. Consequently, the underlying mechanism of impaired CD4+CD25+Foxp3+ iTreg generation was explored by focusing on TGF-β signaling. Finally, the functionality of iTregs was investigated.

RESULTS

Conversion of CD4+CD25-Foxp3- into CD4+CD25+Foxp3+ iTregs was diminished in AD individuals. Impaired iTreg generation was accompanied by a reduced surface expression of GARP (glycoprotein A repetitions predominant), a marker for activated Tregs. A reduced expression of Smad3 mRNA was revealed in CD4+CD25- T cells. Interestingly, the suppressive quality of iTregs was found to be equal in cells derived from AD and healthy donors.

CONCLUSION

The signaling effect of TGF-β receptors on the suppressor quality of iTreg conversion is conserved. Impaired iTreg generation might be a reason for the lack of immune suppression in AD patients and contributes to the chronicity of the disease.

Correlation of Blood FoxP3+ Regulatory T Cells and Disease Activity of Atopic Dermatitis

Objectives

To investigate CD4+CD25+FoxP3+ T regulatory cells (Tregs) in the peripheral blood of patients with atopic dermatitis (AD) and its correlation with disease severity.

Methods

Blood samples from 79 AD patients before and after four-week conventional treatment were collected. Cell counts of CD4+CD25+FoxP3+Tregs, CD4+CD25+FoxP3-T effector cells (Teffs), and CD4+IL-10+Tregs were analyzed by flow cytometry. Serum levels of IL-4, IL-10, IL-12, IL-13, IFN-γ, and TGF-β were measured by ELISA.

Results

The pretreatment cell count of CD4+CD25+FoxP3+Tregs positively correlated with disease severity in all patients (P < 0.0001). However, when that correlation was rechecked based on the treatment response, a much stronger correlation of that was found in those patients with remission after treatment, while no correlation of that was found in patients without remission. Both the cell count and proportions of peripheral CD4+CD25+FoxP3+Tregs and CD4+CD25+FoxP3-Teffs reduced significantly after treatment in patients with remission, but remained unchanged in patients without remission. The cell count and proportion of CD4+IL-10+Tregs did not change after treatment in both groups. In patients with remission, serum levels of IL-4 and IL-13 significantly reduced (all P < 0.05); IL-12 and IFN-γ levels increased significantly (all P < 0.05); IL-10 and TGF-β levels remained unchanged after treatment. None of those cytokine levels changed in patients without remission.

Conclusions

CD4+CD25+FoxP3+Tregs is associated with AD development and severity in some patients but not in others. AD maybe divided into CD4+CD25+FoxP3+Treg-associated subtype, which CD4+CD25+FoxP3+Treg is parallel to the activity of AD, and nonassociated subtype, which CD4+CD25+FoxP3+Treg is not related. This subgroup difference may contribute partly to the nonidentical markers that have been found in AD and should be studied further.

Xenobiotic Receptors and Their Mates in Atopic Dermatitis

Atopic dermatitis (AD) is the most common inflammatory skin disease worldwide. It is a chronic, relapsing and pruritic skin disorder which results from epidermal barrier abnormalities and immune dysregulation, both modulated by environmental factors. AD is strongly associated with asthma and allergic rhinitis in the so-called 'atopic march.' Xenobiotic receptors and their mates are ligand-activated transcription factors expressed in the skin where they control cellular detoxification pathways. Moreover, they regulate the expression of genes in pathways involved in AD in epithelial cells and immune cells. Activation or overexpression of xenobiotic receptors in the skin can be deleterious or beneficial, depending on context, ligand and activation duration. Moreover, their impact on skin might be amplified by crosstalk among xenobiotic receptors and their mates. Because they are activated by a broad range of endogenous molecules, drugs and pollutants owing to their promiscuous ligand affinity, they have recently crystalized the attention of researchers, including in dermatology and especially in the AD field. This review examines the putative roles of these receptors in AD by critically evaluating the conditions under which the proteins and their ligands have been studied. This information should provide new insights into AD pathogenesis and ways to develop new therapeutic interventions.

Filaggrin null mutations are associated with altered circulating Tregs in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a complex pathogenesis. Although regulatory T cells (Tregs) have previously been studied in AD, their role remains controversial, likely owing to patient heterogeneity. Thus, we recruited adult AD patients and age‐matched healthy controls, and assessed their filaggrin (FLG) genotype, serum IgE level, and eczema area and severity index (EASI). We found increased proportions of all circulating Treg subpopulations in AD patients. Moreover, we show positive correlations between circulating Tregs and serum IgE FLG null mutations limited the expansion of both memory and effector Tregs and enhanced that of recently thymus‐emigrated Tregs. Furthermore, proportions of circulating Th2‐ or Th17‐Tregs but not Th1‐Tregs were increased in AD patients, and accentuated by FLG null mutations, thereby mimicking the immune deviation observed in Th cell populations. Moreover, ICOS⁺ Tregs showed reduced production of interleukin‐10, suggesting impaired immunosuppression in AD. The level of demethylation of FOXP3i1, which reflects the stability of FOXP3 expression, was similar in the blood and skin of AD patients and healthy controls. Overall, these results show that Tregs may participate into AD pathogenesis and that FLG null mutations exert further modifications on specific subpopulations of circulating Tregs.

Origin, function and role in the development of skin diseases CLA+T-lymphocytes

The idea of CLA+T-lymphocytes, which are a special subpopulation of cells with a tropic to the skin, is given. The issues of maturation, migration and functional features of CLA+T-cells are considered. Special attention is paid to the different phenotype of memory T-cells. Modern data concerning the role of CLA+T-cells in the pathogenesis of autoimmune and allergic dermatoses, as well as malignant skin tumors are also presented. The conclusion about the necessity of further study of CLA +T-lymphocytes for detailed understanding of pathogenesis and search of variants of targeted therapy in psoriasis, atopic dermatitis, skin lymphomas and other skin diseases is made.

Treatment for moderate to severe atopic dermatitis in alpine and moderate maritime climates differentially affects helper T cells and memory B cells in children

BACKGROUND

Treatment of atopic dermatitis (AD) is focused on topical anti-inflammatory therapy, epidermal barrier repair and trigger avoidance. Multidisciplinary treatment in both moderate maritime and alpine climates can successfully reduce disease activity in children with AD. However, it remains unclear whether abnormalities in B cell and T cell memory normalize and whether this differs between treatment strategies.

OBJECTIVE

To determine whether successful treatment in maritime and alpine climates normalizes B- and T lymphocytes in children with moderate to severe AD.

METHODS

The study was performed in the context of a trial (DAVOS trial, registered at Current Controlled Trials ISCRTN88136485) in which eighty-eight children with moderate to severe AD were randomized to 6 weeks of treatment in moderate maritime climate (outpatient setting) or in the alpine climate (inpatient setting). Before and directly after treatment, disease activity was determined with SA-EASI and serum TARC, and T cell and B cell subsets were quantified in blood.

RESULTS

Both treatment protocols achieved a significant decrease in disease activity, which was accompanied by a reduction in circulating memory Treg, transitional B cell and plasmablast numbers. Alpine climate treatment had a significantly greater effect on disease activity and was accompanied by a reduction in blood eosinophils and increases in memory B cells, CD8+ TemRO, CD4+ Tcm and CCR7+ Th2 subsets.

CONCLUSIONS AND CLINICAL RELEVANCE

Clinically successful treatment of AD induces changes in blood B- and T cell subsets reflecting reduced chronic inflammation. In addition, multidisciplinary inpatient treatment in the alpine climate specifically affects memory B cells, CD8+ T cells and Th2 cells. These cell types could represent good markers for treatment efficacy.

The role of regulatory T cells and genes involved in their differentiation in pathogenesis of selected inflammatory and neoplastic skin diseases. Part II: The Treg role in skin diseases pathogenesis

Regulatory FOXP3+ T cells (Tregs) constitute 5% to 10% of T cells in the normal human skin. They play an important role in the induction and maintenance of immunological tolerance. The suppressive effects of these cells are exerted by various mechanisms including the direct cytotoxic effect, anti-inflammatory cytokines, metabolic disruption, and modulation of the dendritic cells function. The deficiency of Treg cells number or function are one of the basic elements of the pathogenesis of many skin diseases, such as psoriasis, atopic dermatitis, bacterial and viral infections. They also play a role in the pathogenesis of T cell lymphomas of the skin (cutaneous T cell lymphomas - CTCL), skin tumors and mastocytosis. Here, in the second part of the cycle, we describe dysfunctions of Tregs in selected skin diseases.

The Skin as a Route of Allergen Exposure: Part I. Immune Components and Mechanisms

PURPOSE OF REVIEW

To highlight recent contributions in the literature that enhance our understanding of the cutaneous immune response to allergen.

RECENT FINDINGS

Defects in skin barrier function in infancy set the stage for the development of atopic dermatitis (AD) and allergy. Both genetic and environmental factors can contribute to damage of the stratum corneum (SC), with activation of specific protease enzymes under high pH conditions playing a key role. Immune cells and mediators in the dermis and epidermis impair SC repair mechanisms and support allergy development. In barrier-disrupted skin, type 2 innate lymphoid cells (ILC2s), mast cells (MCs), and basophils have been shown to promote AD and pathogenic Th2 responses in murine models. Skin barrier disruption favors induction of systemic Th2-associated inflammatory pathways. A better understanding of the ontogeny and regulation of these complex networks in infant skin is needed to guide future strategies for allergy treatment and prevention.

Defective natural killer cell activity in a mouse model of eczema herpeticum

BACKGROUND

Patients with atopic dermatitis (AD) are susceptible to several viruses, including herpes simplex virus (HSV). Some patients experience 1 or more episodes of a severe skin infection caused by HSV termed eczema herpeticum (EH). There are numerous mouse models of AD, but no established model exists for EH.

OBJECTIVE

We sought to establish and characterize a mouse model of EH.

METHODS

We infected AD-like skin lesions with HSV1 to induce severe skin lesions in a dermatitis-prone mouse strain of NC/Nga. Gene expression was investigated by using a microarray and quantitative PCR; antibody titers were measured by means of ELISA; and natural killer (NK) cell, cytotoxic T-cell, regulatory T-cell, and follicular helper T-cell populations were evaluated by using flow cytometry. The role of NK cells in HSV1-induced development of severe skin lesions was examined by means of depletion and adoptive transfer.

RESULTS

Inoculation of HSV1 induced severe erosive skin lesions in eczematous mice, which had an impaired skin barrier, but milder lesions in small numbers of normal mice. Eczematous mice exhibited lower NK cell activity but similar cytotoxic T-cell activity and humoral immune responses compared with normal mice. The role of NK cells in controlling HSV1-induced skin lesions was demonstrated by experiments depleting or transferring NK cells.

CONCLUSION

A murine model of EH with an impaired skin barrier was established in this study. We demonstrated a critical role of defective NK activities in the development of HSV1-induced severe skin lesions in eczematous mice.

Upregulation of CD47 in Regulatory T Cells in Atopic Dermatitis

PURPOSE

Regulatory T (Treg) cells are key modulators in the immune system. Recent studies have shown that atopic dermatitis (AD) patients have higher numbers of Treg cells; however, little is known about the specific phenotype and function of Treg cells in AD.

MATERIALS AND METHODS

To identify differentially expressed proteins in peripheral induced Treg cells in AD and naturally derived Treg cells in normal controls, CD4⁺CD25⁺ Treg cells were isolated from thymus tissue of normal mice and the spleens of AD mice. Membrane proteins were extracted, and quantitative proteomics labeling with Tandem Mass Tags (TMT) was performed, followed by one-dimensional liquid chromatography/tandem mass spectrometry analysis.

RESULTS

Using TMT labeling, we identified 510 proteins, including 63 membrane proteins and 16 plasma membrane proteins. CD47 was one of the upregulated proteins in Treg cells in AD spleens. Although CD47 was expressed in all CD4⁺ and CD8⁺ T cells, a significantly higher expression of CD47 was observed in the Treg cells of AD mice and AD patients than in those of normal mice and healthy controls. Furthermore, Treg cells from the spleen showed a significantly higher expression of CD47 than those from the thymus.

CONCLUSION

We found that CD47 is highly expressed in the Treg cells of AD mice, particularly in the spleen. Based on our results, we propose that CD47(high) Treg cells are likely induced Treg cells and that upregulated CD47 in the Treg cells of AD patients may play a role in the increased population of Treg cells in AD.

DOCK8: regulator of Treg in response to corticotropin-releasing hormone

BACKGROUND

Atopic dermatitis (AD) is exacerbated by psychological factors, such as stress. We previously reported that corticotrophin-releasing hormone (CRH) treatment in AD patients decreased the proportion of IL-10(+) Tr1 cells, a subset of inducible regulatory T cells (Tregs). However, changes in the function of Tregs in response to CRH have yet to be studied.

METHODS

We analyzed the total proteins taken from CRH-treated and untreated Tregs from AD mice model (NC/Nga mice) using a quantitative proteomic analysis for the different protein expressions.

RESULTS

We found a statistically decreased protein level of DOCK8 in CRH-treated Tregs from AD mice. In human, DOCK8 protein levels were also significantly decreased in CRH-treated Tregs from AD patients. Moreover, the expression of DOCK8 in Tregs was inversely correlated with the anxiety levels in the AD patients. In addition to the clinical correlation of DOCK8 with the stress level of AD patients, the knockdown of DOCK8 in Tregs reduced the inhibitory cytokines, IL-10 and TGF-β, and inhibited the regulatory function of Tregs to suppress the proliferation and TNF-α release of CD4(+) T cells in vitro.

CONCLUSION

This study provides new insights on the mechanisms of stress-induced AD aggravation by showing that CRH downregulated DOCK8 expression in Tregs that not only clinically correlates with anxiety levels of AD patients but also regulates suppressive function of Tregs on CD4(+) T cells.

The impact of langerin (CD207)+ dendritic cells and FOXP3+ Treg cells in the small bowel mucosa of children with celiac disease and atopic dermatitis in comparison to children with functional gastrointestinal disorders

In the present study we aimed to evaluate the impact of langerin (CD207)+ dendritic cells (DCs) and FOXP3+ Treg cells in the intestinal mucosa of children with celiac disease (CD) and atopic dermatitis (AD) in comparison to children with functional gastrointestinal disorders (FGD). Seventy-five children (37 male, mean age 8.4 ± 4.8 years), who randomly underwent small bowel biopsy, were studied. The CD was diagnosed in 14 children, including five persons with concomitant AD (all positive for anti-tissue transglutaminase IgA antibodies and with small bowel atrophy). Normal small bowel mucosa was found in eight patients with AD and in 53 patients with FGD. The sera of all patients were tested for total and specific IgE antibodies to food allergen panels. Staining for CD11c+, langerin (CD207+) DCs, CD4+, and FOXP3+ Treg cells was performed on paraffin-embedded sections of bioptates using immunohistochemistry. The density of CD11c+ DCs, CD4+, and FOXP3+ Treg cells was higher in the CD patients compared to the AD and FGD patients (p = 0.02; p = 0.001). In AD, significantly higher density of CD11c+ DCs was detected in patients positive for specific IgE to food allergen panels (p = 0.02). The FGD patients with elevated total IgE had increased density of langerin (CD207)+ DCs compared to the patients with normal total IgE levels (p = 0.01). The increased density of FOXP3+ Treg cells, CD4+, cells and CD11c+ DCs was associated with CD but not with AD. The elevated level of total IgE or specific IgE to food allergens was associated with more pronounced expression of DCs, indicating a possible link between the presence of these cells in small bowel mucosa with elevated level of serum IgE.

Atopic dermatitis induces the expansion of thymus-derived regulatory T cells exhibiting a Th2-like phenotype in mice

Atopic dermatitis (AD) is a widespread inflammatory skin disease with an early onset, characterized by pruritus, eczematous lesions and skin dryness. This chronic relapsing disease is believed to be primarily a result of a defective epidermal barrier function associated with genetic susceptibility, immune hyper-responsiveness of the skin and environmental factors. Although the important role of abnormal immune reactivity in the pathogenesis of AD is widely accepted, the role of regulatory T cells (Tregs) remains elusive. We found that the Treg population is expanded in a mouse model of AD, i.e. mice topically treated with vitamin D3 (VitD). Moreover, mice with AD-like symptoms exhibit increased inducible T-cell costimulator (ICOS)-, cytotoxic T-lymphocyte antigen-4 (CTLA-4)- and Glycoprotein-A repetitions predominant receptor (GARP)-expressing Tregs in skin-draining lymph nodes. Importantly, the differentiation of Tregs into thymus-derived Tregs is favoured in our mouse model of AD. Emigrated skin-derived dendritic cells are required for Treg induction and Langerhans cells are responsible for the biased expansion of thymus-derived Tregs . Intriguingly, thymus-derived Tregs isolated from mice with AD-like symptoms exhibit a Th2 cytokine profile. Thus, AD might favour the expansion of pathogenic Tregs able to produce Th2 cytokines and to promote the disease instead of alleviating symptoms.

Foxp3(+) regulatory T cells are expanded in severe atopic dermatitis patients

Regulatory T cells (Tregs) are known to play critical roles in homeostasis and immune responses in the skin. Whether Treg frequencies are altered in atopic dermatitis (AD) patients has been addressed by several studies, leading to conflicting results. The detection of Tregs by FOXP3 expression may lead to false-positive results as activated T cells without regulatory function may transiently upregulate this transcription factor. In contrast, measurement of the DNA methylation status of a region within the FOXP3 locus that is selectively demethylated only in bona fide Tregs (Treg-specific demethylated region, TSDR) represents a reliable method to quantify Tregs. Here, we measured circulating Treg frequencies of adult patients and detected a positive correlation with disease severity. Subsequent surface marker analysis revealed higher frequencies of CD45RA(+) CCR7(-) tissue-homing Tregs in the patient group with a tendency of reduced expression of CD39 compared with healthy donors, a marker for the highly suppressive TREM subtype.

Circulating CD4(+) CD25(high) FoxP3(+) T-regulatory cells in patients with atopic dermatitis after narrowband-ultraviolet B phototherapy

BACKGROUND

Previous studies showed controversial results regarding CD4(+) CD25(high) FoxP3(+) T-regulatory cells (Tregs) in atopic dermatitis (AD) and effect of therapy.

METHODS

Circulating CD4(+) CD25(high) FoxP3(+) Tregs were assessed by flow cytometry in 20 controls and 20 patients with AD at baseline and after narrowband ultraviolet B with assessment of disease severity.

RESULTS

Patients showed higher pretreatment T-effector cells (Teffs) (%) and lower pretreatment Tregs FoxP3 expression% than controls (P = 0.003 and 0.01, respectively). Mild AD showed a lower Tregs/Teffs ratio compared to controls (P = 0.013), while moderate group showed higher Teffs%, and lower Tregs FoxP3 expression% and Tregs/Teffs compared to controls (P = 0.016, 0.007, and 0.009 respectively). The severe group had higher Tregs% and Teffs%, yet with a lower Tregs FoxP3 expression% compared to controls (P < 0.001, P = 0.043, P = 0.044, respectively). There was significant reduction of severity after narrowband ultraviolet B (P = 0.007), with overall significant elevation of Tregs FoxP3 expression% in patients (P = 0.004). All patients' post-treatment laboratory findings were statistically matched to each other and to controls whatever their previous severity or therapeutic response. The improvement of severity score correlated with the change in both Tregs% and Tregs/Teffs.

CONCLUSIONS

Significant reduction in AD disease severity is correlated with the change in Tregs% and Tregs/Teffs.

Cytokines and chemokines: At the crossroads of cell signalling and inflammatory disease

Inflammation occurs as a result of exposure of tissues and organs to harmful stimuli such as microbial pathogens, irritants, or toxic cellular components. The primary physical manifestations of inflammation are redness, swelling, heat, pain, and loss of function to the affected area. These processes involve the major cells of the immune system, including monocytes, macrophages, neutrophils, basophils, dendritic cells, mast cells, T-cells, and B-cells. However, examination of a range of inflammatory lesions demonstrates the presence of specific leukocytes in any given lesion. That is, the inflammatory process is regulated in such a way as to ensure that the appropriate leukocytes are recruited. These events are in turn controlled by a host of extracellular molecular regulators, including members of the cytokine and chemokine families that mediate both immune cell recruitment and complex intracellular signalling control mechanisms that characterise inflammation. This review will focus on the role of the main cytokines, chemokines, and their receptors in the pathophysiology of auto-inflammatory disorders, pro-inflammatory disorders, and neurological disorders involving inflammation.

An imbalance between frequency of CD4+CD25+FOXP3+ regulatory T cells and CCR4+ and CCR9+ circulating helper T cells is associated with active perennial allergic conjunctivitis

Allergic conjunctivitis (AC) is one of the most common eye disorders in ophthalmology. In mice models, it has been suggested that control of allergic conjunctivitis is a delicate balance between Tregs and inflammatory migrating effector cells. Our aim was to evaluate the frequency of Tregs and the frequency of homing receptors expressing cells in peripheral blood mononuclear cells (PBMC) from patients with perennial allergic conjunctivitis (PAC). The analyses of phenotypic markers on CD4+ T cells and both soluble or intracellular cytokines were performed by flow cytometry. CD4+CD25+ cells were 15 times more frequent in PBMC from patients than HC; the vast majority of these CD4+CD25+ cells were FOXP3-, and most of CD4+ T cells were CCR4+ and CCR9+ cells. Upon allergen-stimulation, no significant changes were observed in frequency of Treg; however, an increased frequency of CD4+CCR4+CCR9+ cells, CD4+CD103+ cells and CD4+CD108+ cells with increased IL-5, IL-6, and IL-8 production was observed. These findings suggest an immune dysregulation in PAC, characterized by diminished frequency of Tregs and increased frequency of circulating activated CD4+ T cells; upon allergen-stimulation, these cells were expressing cell-surface molecules related to mucosa homing and were able to trigger an inflammatory microenvironment.

Mechanisms of tolerance induction in allergic disease: integrating current and emerging concepts

The prevalence of atopy and allergic disease continues to escalate worldwide. Defining immune mechanisms that suppress the underlying Th2-driven inflammatory process is critical for the rational design of new treatments to prevent or attenuate disease. Allergen immunotherapy has provided a useful framework for evaluating changes in the immune response that occur during the development of tolerance. Despite this, elucidating the phenotypic and functional properties of regulatory cells, has proven challenging in humans with allergic disease. This article provides an overview of our current understanding of the immune pathways that orchestrate allergen tolerance, with an emphasis on emerging concepts related to human disease. A variety of regulatory cell types, including IL-10-secreting T and B cells, play a pivotal role in suppressing allergic responses to inhaled, ingested and injected allergens. These cells may inhibit Th2 effectors directly, or else indirectly, through other cell types and mediators. Protective antibodies, including IgG4, Fc sialylated IgG, and IgA, have the capacity to modulate the response by preventing allergen binding to surface-bound IgE, or inhibiting dendritic cell maturation. Immune cell plasticity may augment suppression of Th2 cells by T regulatory cells, through mechanisms that involve T cell conversion, or else unconventional roles of classical effector cells. These actions depend upon external cues provided by the in vivo milieu. As such, specific anatomical sites may preferentially favour tolerance induction. Recent scientific advances now allow a global analysis of immune parameters that capture novel markers of tolerance induction in allergic patients. Such markers could provide new molecular targets for assessing tolerance, and for designing treatments that confer long-lasting protection in a safe and efficacious fashion.

Pathological mechanisms of skin homing T cells in atopic dermatitis

Skin infiltration of circulating memory T cells with cutaneous tropism is considered one of the pathologic mechanisms in atopic dermatitis (AD). Skin-seeking circulating T lymphocytes can be identified by their expression of the cutaneous lymphocyte-associated antigen on the cell surface. Recent studies have contributed useful new information about the function and recirculation properties of those cells in AD patients. This review integrates the latest findings on peripheral cutaneous lymphocyte-associated antigen memory T cells in AD and highlights the relevance of this cell type and its importance to our understanding of the pathologic mechanisms of AD.

T-regulatory cells in severe atopic dermatitis: alterations related to cytokines and other lymphocyte subpopulations

The changes in lymphocyte subpopulations in atopic dermatitis (AD) concern also T-regulatory cells. We investigated the expression of various surface receptors on CD3⁺CD4⁺CD25^highFoxP3⁺ T-regulatory cells and the activation CD28⁺ receptor and the inhibitory CD152⁺ receptor on helper/inducer as well as cytotoxic/suppressor T cells. Peripheral blood lymphocytes of 15 AD patients and 20 healthy subjects were analyzed by flow cytometry using monoclonal antibodies. The concentrations of IL-6, IL-10 and TGF-β were determined in the serum and the supernatant of ConA-stimulated CD4⁺ lymphocytes. In AD patients the percentage of CD4⁺CD25^highFoxP3⁺ as well as CD3⁺CD8⁺ cells increased, which positively correlated with SCORAD index (r = 0.55, p = 0.03). The concentrations of IL-10 in the CD4⁺ lymphocyte culture supernatants and the concentrations of TGF-β in the sera and the supernatant negatively correlated with the severity of AD (p < 0.01, r = −0.63; p < 0.02, r = −0.64 and p < 0.03, r = −0.58, respectively), whereas the serum concentration of IL-6 correlated positively (p < 0.003, r = 0.71). The regulatory cells expressed more CD62L and CD134 surface markers but less CD95. Reduced expression of the apoptotic CD95 receptor suggests that survival time of these cells is prolonged. Since CD62L and CD134 were upregulated, the enhanced modulatory effect of CD4⁺CD25^highFoxP3⁺ cells seemed to be suggested, which may result in increased co-expression of CD28/CD152 on both CD4⁺ and CD8⁺ subpopulations.

Foxp3+ cells control Th2 responses in a murine model of atopic dermatitis

The role of Foxp3+ regulatory T (Treg) cells in atopic dermatitis (AD) is still unclear. In a murine AD model, the number of Foxp3+ cells increased in the allergen-exposed skin area and in the secondary lymphoid organs. Both Foxp3+ and Foxp3- IL-10+ T cells accumulated at the site of allergen exposure, and CD103+ effector/memory Foxp3+ Treg cells expanded gradually in the lymph nodes throughout the sensitization protocol. The depletion of Foxp3+ Treg cells led to significantly exacerbated skin inflammation, including increased recruitment of inflammatory cells and expression of T helper type 2 cytokines, as well as elevated serum IgE levels. The effect of depleting Treg cells during epicutaneous sensitization was mirrored off by a stronger inflammatory response also in the lungs following airway challenge. Thus, Treg cells have an important role in controlling AD-like inflammation and the transfer of allergic skin inflammation to the lungs.

Mechanisms of subcutaneous allergen immunotherapy

Allergen-specific immunotherapy (SIT) is the only curative approach in the treatment of allergic diseases defined up-to-date. Peripheral T-cell tolerance to allergens, the goal of successful allergen-SIT, is the primary mechanism in healthy immune responses to allergens. By repeated administration of increased doses of the causative allergen, allergen-SIT induces a state of immune tolerance to allergens through the constitution of T regulatory (Treg) cells, including allergen-specific interleukin (IL)-10-secreting Treg type 1 cells and CD4(+)CD25(+)Treg cells; induction of suppressive cytokines, such as IL-10 and transforming growth factor β; suppression of allergen-specific IgE and induction of IgG4 and IgA; and suppression of mast cells, basophils, eosinophils, and inflammatory dendritic cells. This review summarizes the current knowledge on the mechanisms of allergen-SIT with emphasis on the roles of Treg cells in allergen-SIT.

Regulatory T cells in cutaneous immune responses

Regulatory T cells (Treg) are a subset of T cells with strong immunosuppressive activity. In the skin, it has recently been revealed that Treg play important roles not only in the maintenance of skin homeostasis but also in the regulation of the immune responses, such as contact hypersensitivity and atopic dermatitis. Furthermore, the skin plays important roles in the induction of Treg in the periphery. In this review, we will provide an overview of the mechanism of Treg-mediated immunosuppression and discuss the role of Treg in the skin.

Divergence of gut permeability and mucosal immune gene expression in two gluten-associated conditions: celiac disease and gluten sensitivity

BACKGROUND

Celiac disease (CD) is an autoimmune enteropathy triggered by the ingestion of gluten. Gluten-sensitive individuals (GS) cannot tolerate gluten and may develop gastrointestinal symptoms similar to those in CD, but the overall clinical picture is generally less severe and is not accompanied by the concurrence of tissue transglutaminase autoantibodies or autoimmune comorbidities. By studying and comparing mucosal expression of genes associated with intestinal barrier function, as well as innate and adaptive immunity in CD compared with GS, we sought to better understand the similarities and differences between these two gluten-associated disorders.

METHODS

CD, GS and healthy, gluten-tolerant individuals were enrolled in this study. Intestinal permeability was evaluated using a lactulose and mannitol probe, and mucosal biopsy specimens were collected to study the expression of genes involved in barrier function and immunity.

RESULTS

Unlike CD, GS is not associated with increased intestinal permeability. In fact, this was significantly reduced in GS compared with controls (P = 0.0308), paralleled by significantly increased expression of claudin (CLDN) 4 (P = 0.0286). Relative to controls, adaptive immunity markers interleukin (IL)-6 (P = 0.0124) and IL-21 (P = 0.0572) were expressed at higher levels in CD but not in GS, while expression of the innate immunity marker Toll-like receptor (TLR) 2 was increased in GS but not in CD (P = 0.0295). Finally, expression of the T-regulatory cell marker FOXP3 was significantly reduced in GS relative to controls (P = 0.0325) and CD patients (P = 0.0293).

CONCLUSIONS

This study shows that the two gluten-associated disorders, CD and GS, are different clinical entities, and it contributes to the characterization of GS as a condition associated with prevalent gluten-induced activation of innate, rather than adaptive, immune responses in the absence of detectable changes in mucosal barrier function.

Skin-homing CD4+ Foxp3+ T cells exert Th2-like function after staphylococcal superantigen stimulation in atopic dermatitis patients

BACKGROUND

The effect of staphylococcal superantigens (SsAgs) on cutaneous lymphocyte-associated antigen (CLA)(+) CD4(+) Foxp3(+) T cells of atopic dermatitis (AD) patients is unknown.

OBJECTIVE

To compare the effects of SsAgs on the ratio, function, and apoptosis of CCR6(+) subtype and CCR6(-) subtype of CLA(+) CD4(+) Foxp3(+) T cells among AD patients, asthma/allergic rhinitis (AR) patients without AD, and healthy subjects.

METHODS

Using immunofluorescence staining followed by flow cytometric analysis, we analysed peripheral blood mononuclear cells cultured with or without staphylococcal enterotoxin B (SEB) stimulation in 20 AD patients, 20 asthma/AR patients without AD, and 20 healthy subjects.

RESULTS

SEB decreased CCR6(+) /CCR6(-) ratio in CLA(+) CD4(+) Foxp3(+) T cells from AD patients and increased CCR6(+) /CCR6(-) ratio in those from healthy subjects. SEB induced the production of type 2 T helper cell (Th2) cytokine interleukin (IL)-5 in CCR6(-) subtype and anti-inflammatory cytokine IL-10 in CCR6(+) subtype of CLA(+) CD4(+) Foxp3(+) T cells. CLA(+) CD4(+) Foxp3(+) T cells from AD patients produced more IL-5 and less IL-10 after SEB stimulation than those from healthy subjects. CCR6(-) subtype of CLA(+) CD4(+) Foxp3(+) T cells from AD patients and CCR6(+) subtype of those cells from healthy subjects were more resistant to SEB-induced caspase-3 activation than the other subtype and those from other subjects.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite a phenotype of regulatory T cells, skin-homing CD4(+) Foxp3(+) T cells of AD patients exert effector Th2-like function after SsAgs stimulation, which may aggravate allergic skin inflammation.

Flow cytometry imaging identifies rare T(H)2 cells expressing thymic stromal lymphopoietin receptor in a "proallergic" milieu

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is expressed at sites of allergic inflammation, including eczematous skin. This cytokine has been reported to exert its T(H)2-inducing properties through dendritic cells. Expression of TSLP receptor on the surface of activated T(H)2 cells could amplify T(H)2 responses at inflamed sites through the direct actions of TSLP.

OBJECTIVE

To test rigorously whether T(H)2 cells induced by "proallergic" factors express TSLP receptor and characterize these cells using an experimental platform that combines flow cytometry with microscopic capabilities.

METHODS

CD4(+) T cells isolated from patients with atopic dermatitis or normal healthy controls were cocultured with autologous dendritic cells in the presence of T(H)2-promoting stimuli (TSLP ± allergen and staphylococcal enterotoxin B ± TSLP). Surface expression of TSLP receptor was analyzed by image-based flow cytometry, and responsiveness of purified T cells to TSLP was assessed by phosphorylation of signal transducer and activator of transcription-5 and cytokine secretion.

RESULTS

T(H)2-promoting stimuli induced a robust population of activated T(H)2 cells (CD25(+)IL-4(+)). Regardless of the nature of the stimulus, flow cytometry imaging confirmed that T cells expressing TSLP receptor were rare, constituting a minor fraction of the IL-4(+) T cell pool; however, TSLP responsiveness was nonetheless detectable. Analysis of cell size and nuclear morphology revealed preferential expression of TSLP receptor on IL-4-expressing cells undergoing mitosis. Analysis of lesional skin in atopic dermatitis supported the view that rare IL-4(+) T cells expressing TSLP receptor are present at inflamed sites.

CONCLUSION

In a "proallergic" milieu, TSLP receptor is preferentially expressed on rare actively dividing T(H)2 cells. The direct action of TSLP on T cells could amplify T(H)2 responses at sites of allergic inflammation.

3G11 expression in CD4+ T cell-mediated autoimmunity and immune tolerance

3G11 is a sialylated carbohydrate epitope of the disialoganglioside molecule expressed on mouse CD4(+) T cells. Recent research showed that 3G11 expression is related to the modulation of T cell function, i.e., 3G11(-) T cells exhibit anergic/Treg characteristics and efficiently inhibit autoimmunity in the central nervous system. The relationship between 3G11 expression and immune tolerance is summarized in this literature review.

IL-2 and IL-4 stimulate MEK1 expression and contribute to T cell resistance against suppression by TGF-beta and IL-10 in asthma

The T cell-driven airway inflammation in chronic asthma is uninhibited and sustained. We examined the resistance of T cells from asthmatic patients against suppression by TGF-β, IL-10 and glucocorticoids and explored its signaling mechanism. CD4(+)CD25(-) T cells from allergic asthmatic subjects demonstrated increased TCR-stimulated proliferation as compared with healthy and chronic obstructive pulmonary disease controls. This proliferation was resistant to inhibition by TGF-β, IL-10, and dexamethasone and to anergy induction. CD4 T cells from asthmatic patients, but not chronic obstructive pulmonary disease, allergic rhinitis, and healthy subjects, showed increased expression of MEK1, heightened phosphorylation of ERK1/2, and increased levels of c-Fos. IL-2 and IL-4 stimulated the expression of MEK1 and c-Fos and induced T cell resistance. The inhibition of MEK1 reversed, whereas induced expression of c-Fos and JunB promoted T cell resistance against TGF-β- and IL-10-mediated suppression. We have uncovered an IL-2- and IL-4-driven MEK1 induction mechanism that results in heightened ERK1/2 activation in asthmatic T cells and make them resistant to certain inhibitory mechanisms.