Abnormal IL-4 gene expression by atopic dermatitis T lymphocytes is reflected in altered nuclear protein interactions with IL-4 transcriptional regulatory element

Preclinical immunological characterization of rademikibart (CBP-201), a next-generation human monoclonal antibody targeting IL-4Rα, for the treatment of Th2 inflammatory diseases

Rademikibart (CBP-201) is a next-generation human monoclonal antibody targeting IL-4Rα, undergoing evaluation in Phase 2 clinical trials for the treatment of moderate-to-severe Th2 inflammatory diseases. We report the immunological characterization of rademikibart. Rademikibart and dupilumab were associated with K_D of 20.7 pM and 45.8 pM, respectively, when binding to distinct human IL-4Rα epitopes. Rademikibart did not bind to IL-4Rα from other species. Rademikibart inhibited IL-4 and IL-13-mediated STAT6 signaling (mean ± SD IC₅₀: 7.0 ± 2.5 and 6.6 ± 1.5 ng/mL, respectively), TF-1 cell proliferation (IC₅₀: 8.0 ± 1.6 and 9.7 ± 0.8 ng/mL, respectively) and TARC production in PBMCs (IC₅₀: 59.2 ± 3.9 and 13.5 ± 0.2 ng/mL, respectively). Rademikibart versus dupilumab was more potent in the STAT6 assays (IL-4, p < 0.01; IL-13, p = 0.03), with non-significant trends towards greater potency in the TF-1 cell assays (IL-4, p = 0.09; IL-13, p = 0.20), and similar potency in the TARC assays. In experiments with mice expressing human IL-4Rα and IL-4, rademikibart and dupilumab demonstrated similar potency; both monoclonal antibodies eliminated IL-4 (p < 0.0001) and IL-13 (p < 0.05) mediated B cell activation in vitro and ovalbumin-induced IgE (p < 0.01) and eosinophilic lung infiltration (p < 0.0001) in vivo. In Th2-stimulated human skin explants, rademikibart rapidly downregulated IL-4, IL-13, and TARC gene expression, with greater effectiveness than dupilumab for IL-4 (p < 0.01) and a non-significant trend towards superiority for IL-13. In summary, rademikibart bound to a distinct IL-4Rα epitope with high affinity and demonstrated reductions in Th2 inflammatory biomarkers with at least similar and potentially superior potency to dupilumab.

Fixed-Combination Halobetasol Propionate and Tazarotene in the Treatment of Psoriasis: Narrative Review of Mechanisms of Action and Therapeutic Benefits

Psoriasis is a lifelong disease associated with cycles of remission and relapse. Topical treatments are the front line of psoriasis therapy for most patients and have antiproliferative, anti-inflammatory, and immunosuppressive mechanisms of action. Novel fixed-dose combinations of topical therapeutic agents are becoming increasingly available, leveraging multiple mechanisms of action to improve safety and efficacy with formulations that are easier to use and may allow for the use of lower doses of active ingredients. A fixed-combination lotion containing the potent-to-superpotent corticosteroid halobetasol propionate (HP) and the retinoid tazarotene (HP 0.01%/TAZ 0.045%) was recently developed using polymeric emulsion technology. This new formulation technology allows for more uniform and efficient delivery of the active ingredients at lower doses than conventional monotherapy formulations of either ingredient while providing enhanced hydration and moisturization. This review provides an up-to-date overview of the therapeutic mechanisms of action of HP and TAZ, the rationale behind the development of HP 0.01%/TAZ 0.045% lotion, and clinical trials data on the efficacy, safety and tolerability, and maintenance of therapeutic effect with HP 0.01%/TAZ 0.045% lotion in the treatment of moderate-to-severe plaque psoriasis.

Emerging Systemic Therapeutic Biologics and Small Molecules for Atopic Dermatitis: How to Decide Which Treatment Is Right for Your Patients

The evolving discoveries in atopic dermatitis (AD) broaden our understanding of the pathogenesis of the disease and, above all, enable better management for patients. Dupilumab was the first biologic for AD, and since its approval, many new treatments have emerged in both late- and early-stage clinical trials. These trials have led to a further understanding of the pathogenesis of AD and to the identification of additional potential therapeutic targets. This review will highlight the emerging therapies and provide approaches on how to choose the right treatment for your patients.

Inverse Correlation of TRIM32 and Protein Kinase C ζ in T Helper Type 2-Biased Inflammation

Atopic dermatitis (AD) is a T helper (Th)2-biased disease with elevated expression of Th2 cytokines that responds to Th2 signaling blockade. TRIM32 is an E3 ubiquitin ligase with innate antiviral activity. In our previous studies, we showed that Trim32 null mice developed Th2-biased skin inflammation in response to imiquimod and associated a low level of TRIM32 with AD. In this study, we provide evidence that TRIM32 deficiency contributes to enhanced Th2 cell differentiation in vitro. Analysis of TRIM32-associated proteins from public databases identified protein kinase C (PKC)ζ as a TRIM32-associated protein that contributes to the regulation of Th2 signaling. We demonstrated that PKCζ was specifically ubiquitinated by TRIM32 and, further, that PKCζ stability tended to be increased in Th2 cells with a Trim32 null background. Furthermore, Prkcz null mice showed compromised AD-like phenotypes in the MC903 AD model. Consistently, a high PKCζ and low TRIM32 ratio was associated with CD4+ cells in AD human skin compared with those in healthy controls. Taken together, these findings suggest that TRIM32 functions as a regulator of PKCζ that controls the differentiation of Th2 cells important for AD pathogenesis.

Psychoneuroimmunology

Psychoneuroimmunology (PNI) is a discipline that has evolved in the last 40 years to study the relationship between immunity, the endocrine system, and the central and peripheral nervous systems. In this manner, neurotransmitters, hormones, and neuropeptides have been found to regulate immune cells, and these in turn are capable of communicating with nervous tissue through the secretion of a wide variety of cytokines. Of critical importance is the effect of products of the CNS and nerves on the maintenance of the delicate balance between cell-mediated (Th1) and humoral (Th2) immune responses. A good example of how this concept operates in vivo becomes evident when analyzing the effects of stressors. Chronic stress affects significantly the function of the immune system as well as modifies the evolution of a variety of skin diseases, as psychosocial interventions have proved to be effective in their therapy.

IL-16 serum level in children with atopic dermatitis

IL-16 is a natural ligand of CD4 molecules and induces chemotaxis in CD4-expressing cells. It amplifies the inflammatory reaction by stimulating cytokine production in monocytes and activating T-cells. There is evidence that IL-16 plays a role in the pathogenesis of atopic dermatitis, and increased serum levels of IL-16 have been detected in allergic diseases. However, few data are available on IL-16 serum levels in atopic dermatitis. The aim of our study is to measure IL-16 serum levels in childhood atopic dermatitis before and after treatment and to evaluate a possible correlation between IL-16 serum levels and disease severity. IL-16 serum levels were measured by an ELISA approach in 34 children (19 males and 15 females; mean age 6.8 years) with moderate to severe atopic dermatitis, at their first visit and after 3 months of treatment, and in 10 non-atopic healthy controls of the same age group. The severity of atopic dermatitis was measured by SCORAD index. IL-16 serum levels were significantly higher in patients affected by atopic dermatitis than in controls before and after treatment with tacrolimus ointment. No clear correlation was found between IL-16 serum levels and atopic dermatitis severity. IL-16 serum levels are increased in atopic dermatitis but do not seem to correlate with disease severity.

Involvement of human natural killer cells in asthma pathogenesis: natural killer 2 cells in type 2 cytokine predominance

BACKGROUND

T H 2 cells play a pivotal role in the pathogenesis of human asthma. Natural killer (NK) cells are also thought to divide into NK1 and NK2 subsets.

OBJECTIVE

Whether NK1 or NK2 cells are involved in asthma remains unclear.

METHODS

Triple-color flow cytometry for detecting intracellular cytokine and NK cell surface phenotype from asthmatic patients was used. The NK cell cloning and analysis with RT-PCR for cytokine expression and Western blotting for signal transducer and activator of transcription activation were performed.

RESULTS

For the first time, we observed that the ratio of IL-4 + CD56 + NK2 cells in PBMCs of 8 asthmatic patients were higher than in healthy individuals. NK cell clones were then obtained by means of limited dilution, and the average mean of the relative intensity of PCR products for type 2 cytokines significantly increased in the asthmatic patients. Signal transducer and activator of transcription 6, a key transcript factor of type 2 phenotype, was constitutively activated in NK2 clones from asthmatic patients. We cocultured freshly purified NK cells from asthmatic patients with IFN-gamma and anti-IL-4 antibody in the presence of IL-15 and found that the content of IL-4 + NK2 cells significantly decreased after treatment. Interestingly, NK2-biased status in asthmatic patients was reversed when patients recovered from regular therapy.

CONCLUSION

The results suggest that the NK2 cell subset is involved in the pathogenesis of asthma.

Early up-regulation of Th2 cytokines and late surge of Th1 cytokines in an atopic dermatitis model

We investigated cytokine profiles in interleukin (IL)-4 transgenic (Tg) mice with a skin inflammatory disease resembling human atopic dermatitis. cDNA microarray revealed that the mRNAs encoding IL-1beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IL-12p40, IL-13, tumour necrosis factor (TNF)-alpha, TNF-beta and interferon (IFN)-gamma were up-regulated in the skin of late lesion Tg mice and to a lesser degree in non-lesion Tg mice when compared to those of non-Tg mice. Real time reverse transcription-polymerase chain reaction (RT-PCR) analyses indicated that the cDNA copy numbers of IL-1beta, IL-4, IL-6, IL-10, TNF-alpha and IFN-gamma from the skin of late, early and non-lesions increased significantly compared to non-Tg mice. IL-2 and IL-12p40 cDNA copy numbers were increased significantly in early, but not late, lesions. Interestingly, IL-1beta, IL-3, IL-4, IL-5, IL-6, IL-10, IL-13, TNF-alpha, and IFN-gamma cDNAs were increased significantly the skin of before-onset and/or non-lesion mice. Flow cytometry analyses demonstrated an increased percentage of keratinocytes producing IL-4 as the disease progressed. The percentage of IL-2, IL-4, IL-10 and IFN-gamma-producing T cells and IL-12-producing antigen-presenting cells in skin-draining lymph nodes and inflammatory skin also increased, particularly in mice with late lesion. These results suggest that disease induction is primarily triggered by Th2 cytokines and that Th1, Th2 and non-Th proinflammatory cytokines are all involved in the disease process.

Anti-interleukin-4 therapy

Interleukin 4 (IL-4) mediates important pro-inflammatory functions in asthma, including T helper cell type 2 lymphocyte differentiation, induction of IgE production, up-regulation of IgE receptors, expression of vascular cell-adhesion molecule 1, promotion of eosinophil transmigration into the lungs, inhibition of T-lymphocyte apoptosis, and mucus hypersecretion. The role of IL-4 in the pathogenesis of asthma is supported by identification of polymorphisms linked to asthma in the IL-4 gene promoter and proteins involved in IL-4 signaling. Several approaches to IL-4 antagonism are or have been in clinical development. This article examines IL-4 and the antagonists that have been developed. Early trial results and the future of anti-IL-4 therapy are discussed.

Exposure to 4-tert-octylphenol, an environmentally persistent alkylphenol, enhances interleukin-4 production in T cells via NF-AT activation

4-tert-Octylphenol (OP) is a representative endocrine disruptor that may have adverse effects on human health. The influence of this compound on allergic immune responses remains unclear. In this study, we have examined the effects of OP on production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune responses. OP significantly enhanced IL-4 production in antigen-primed T cells in a dose-dependent manner. Treatment with OP in vivo resulted in significant increase of IL-4 production in T cells and of IgE levels in sera of antigen-primed mice. Furthermore, OP enhanced the activation of IL-4 gene promoter in EL4 T cells transiently transfected with IL-4 promoter/reporter constructs, and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for nuclear factor of activated T cell (NF-AT). Activation of T cells by phorbol-12-myristate-13-acetate (PMA) resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of OP, indicating that the transcription factor NF-AT was involved in the enhancing effect of OP on IL-4 production. The enhancement of IL-4 production by OP was blocked by FK506, a calcineurin inhibitor, but not by the estrogen receptor (ER) antagonist ICI 182780. FK506 inhibited the NF-AT-DNA binding activity and IL-4 gene promoter activity enhanced by OP in a dose-dependent manner. These findings demonstrate that OP enhances IL-4 production in T cells via the stimulation of calcineurin-dependent NF-AT activation.

Terfenadine antagonism against interleukin-4-modulated gene expression of T cell cytokines

Here, we investigated whether an anti-allergy drug, terfenadine, affects interleukin-4-modulated cytokine expression in peripheral T cells. Peripheral blood T cells were first stimulated with recombinant interleukin-4 and then tested for modulation of the mRNA of a panel of cytokines using the reverse transcription-polymerase chain reaction followed by Southern blot analysis. It was found that T cells constitutively expressed mRNA specific to T helper 1 cytokines (interleukin-2, interferon-gamma, tumor necrosis factor-alpha), which was markedly downregulated upon stimulation with interleukin-4, whereas mRNA for T helper 2 cytokines such as interleukins 4, 5, and 6 was induced in response to interleukin-4. Interestingly, the interleukin-4-induced expression of all T helper 2 cytokines examined was markedly downregulated by terfenadine. Among T helper 1 cytokines, interleukin-4-mediated suppression of tumor necrosis factor-alpha was not affected by terfenadine, which, however, markedly restored mRNA expression of interferon-gamma or interleukin-2. Electrophoretic mobility shift assays using [32P]-labeled synthetic oligonucleotides encoding the consensus binding motif of activator protein-1 demonstrated that interleukin-4-induced binding of activator protein-1 composed of JunB was interfered by terfenadine. This study indicates that terfenadine, at least partially, interferes with interleukin-4-activated signaling, leading to terfenadine antagonism against the modulatory impact of interleukin-4 on T cell cytokines.

Cytomegalovirus M43 gene modulates T helper cell response

Role of viral genes in modulating T helper 1 (Th1) and T helper 2 (Th2) balance is of principal interest in the study of cytomegalovirus (CMV) immunity. Murine CMV (MCMV) mutants were used to explore a possible mechanism for the ability of virus to induce a predominant Th1 response and to suppress Th2 response by examining the production of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-10) cytokines by the splenocytes of mice infected with wild type (WT) and MCMV mutants. Results (n=6) show that as compared with WT, the MCMV mutant with specific disruption of M43 gene upregulates the production of IL-4 (P=0.0002) and to a lesser extent IL-10 (P=0.015) at 14 days post infection. This indicates that M43 gene may play a role in suppressing Th2 (IL-4) production, especially in the later stage of infection. The IL-4 and IL-10 production during infection with M43 mutant occurs in the presence of a strong IFN-gamma (Th1) response, overriding the cross-regulatory effects of these cytokines within the Th1/Th2 paradigm and suggesting that the predominant response during CMV infection is still a Th1 type response.

Enhanced interleukin-4 production in CD4+ T cells and elevated immunoglobulin E levels in antigen-primed mice by bisphenol A and nonylphenol, endocrine disruptors: involvement of nuclear factor-AT and Ca2+

Bisphenol A (BPA) and p-nonylphenol (NP) are representative endocrine disruptors (EDs) that may have adverse effects on human health. The influence of these compounds on allergic immune responses remains unclear. In this study, we have examined the effects of BPA and NP on production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune responses. Both BPA and NP significantly enhanced IL-4 production in keyhole limpet haemocyanin (KLH)-primed CD4+ T cells in a concentration-dependent manner. Treatment with BPA or NP in vivo resulted in significant increase of IL-4 production in CD4+ T cells and of antigen-specific immunoglobulin E (IgE) levels in the sera of KLH-primed mice. Furthermore, BPA and NP enhanced the activation of IL-4 gene promoter in EL4 T cells transiently transfected with IL-4 promoter/reporter constructs, and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for nuclear factor (NF)-AT. Activation of T lymphocytes by phorbol 12-myristate 13-acetate/ionomycin resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of BPA or NP, as demonstrated by the electrophoretic mobility shift assay, indicating that the transcription factor NF-AT was involved in the enhancing effect of BPA and NP on IL-4 production. The enhancement of IL-4 production by BPA or NP was significantly reduced by nitrendipine, a blocker of Ca2+ influx, and by FK506, a calcineurin inhibitor. FK506 inhibited the NF-AT-DNA binding activity and IL-4 gene promoter activity enhanced by BPA or NP. These results represent the first report describing possible enhancement of allergic response by EDs through increasing IL-4 production in CD4+ T cells and antigen-specific IgE levels in the sera via the stimulation of Ca2+/calcineurin-dependent NF-AT activation.

Atopic dermatitis: the role of recombinant interferon-gamma therapy

Atopic dermatitis is a common, chronic, relapsing cutaneous disease with typical cellular and humoral immunologic abnormalities that can result in significant physical and psychological morbidity to the patient. Atopic dermatitis typically begins in childhood and can often persist through adolescence into adulthood. Although there are a variety of treatments for atopic dermatitis, many patients' symptoms do not improve or they have adverse reactions to medications, requiring the search for other, effective therapeutic agents. A number of inflammatory and immunological abnormalities have long been noted in patients with atopic dermatitis. Although great strides have been made in understanding the causes, the complex pathophysiology of atopic dermatitis is still not completely understood. Most notably, patients with atopic dermatitis often have an elevation of serum immunoglobulin (Ig) E levels, depressed cellular immunity, elevated blood eosinophilia, and increased interleukin (IL)-4 production. In addition, peripheral blood mononuclear cells of patients with atopic dermatitis produce reduced levels of interferon-gamma spontaneously and in response to stimuli. Due to this constellation of features, atopic dermatitis was initially viewed as a prototypical type 2 helper T lymphocyte (T(h2)) disease. These immunological findings led to a number of clinical trials with recombinant interferon-gamma in patients who had severe, unremitting atopic dermatitis. Treatment with recombinant interferon-gamma was postulated to be able to correct the immunological imbalances in patients with atopic dermatitis by decreasing serum IgE levels, IL-4 levels, restoring immune balance, and thereby leading to clinical improvement. Initial open-label studies, a double-blind placebo trial, and long-term open-label studies have demonstrated the clinical efficacy and tolerability of recombinant interferon-gamma in a subset of patients with severe, unremitting atopic dermatitis. Patients receiving treatment often had marked decreases in severity of clinical parameters: erythema, edema/indurations, pruritus, excoriations, dryness, lichenification and associated reduction in total body surface area involvement. Surprisingly, treatment with recombinant interferon-gamma did not lower serum IgE levels refuting the hypothesized mechanism by which interferon-gamma would bring about clinical improvement in patients with atopic dermatitis. Instead, decreases were noted in absolute white blood cell and eosinophil counts that tended to correlate with clinical improvement. Although the exact mechanism by which recombinant interferon-gamma brings about clinical changes in patients with atopic dermatitis is unknown, recombinant interferon-gamma should be considered a possible therapy for patients with atopic dermatitis.

Th1/Th2 biasing effects of vaccination in cattle as determined by real-time PCR

Real-time polymerase chain reaction (PCR) is now becoming an accepted tool for measuring gene expression at the transcriptional level. In this study, a direct comparison between real-time PCR, enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunosorbent spot (ELISPOT) assay was performed. When interferon-gamma (IFN-gamma) gene expression was assessed, both ELISA and ELISPOT data strongly correlated to results obtained by real-time PCR. Real-time PCR was subsequently used to measure bovine IFN-gamma (bIFN-gamma) and bovine interleukin-4 (bIL-4) gene expression by antigen stimulated peripheral blood mononuclear cells (PBMC), isolated from bovine herpesvirus-1 (BHV-1) infected animals. BHV-1-infected animals were either non-vaccinated or vaccinated using one of two adjuvants prior to infection. With non-vaccinated infected animals, a Th1 bias occurred, based on IFN-gamma expression exceeding IL-4 expression. The level of cytokine expression, and the IFN-gamma/IL-4 ratio could be significantly affected, depending on the manner in which animals were vaccinated.

Histone deacetylation inhibits IL4 gene expression in T cells

BACKGROUND

Dysregulated expression of IL-4 has been linked with allergic diseases. IL-4 expression is controlled at the level of gene transcription by the coordinated action of multiple factors that bind regulatory promoter elements. In addition, alterations in chromatin structure are thought to play a role in regulating the expression of cytokines in the T(H)2 gene cluster, although the biochemical basis for these alterations in human T cells is not well understood.

OBJECTIVE

We sought to define the role of histone acetylation in the regulation of IL4 gene expression in human T cells.

METHODS

IL-4 protein production was measured by means of ELISA. IL-4 promoter activity was measured with luciferase-based reporter constructs transiently transfected into Jurkat T cells. The acetylation status of histones associated with the IL4 gene was analyzed with chromatin immunoprecipitation assays.

RESULTS

IL-4 production from activated peripheral blood T cells was enhanced by the histone deacetylase inhibitor trichostatin A. Overexpression of the type 1 histone deacetylases 1, 2, and 3 inhibited transcription driven by the IL-4 promoter in Jurkat T cells, whereas cotransfection of the histone acetyltransferase CREB-binding protein potentiated IL-4 promoter activity. Using chromatin immunoprecipitation assays, we show that nucleosomes in the proximal IL-4 promoter are acetylated on T-cell activation.

CONCLUSION

Our results demonstrate that the acetylation state of histones associated with the IL-4 promoter is a key regulator of IL4 gene expression.

Th2 cytokines and asthma. Interleukin-4: its role in the pathogenesis of asthma, and targeting it for asthma treatment with interleukin-4 receptor antagonists

Interleukin-4 (IL-4) mediates important pro-inflammatory functions in asthma including induction of the IgE isotype switch, expression of vascular cell adhesion molecule-1 (VCAM-1), promotion of eosinophil transmigration across endothelium, mucus secretion, and differentiation of T helper type 2 lymphocytes leading to cytokine release. Asthma is a complex genetic disorder that has been linked to polymorphisms in the IL-4 gene promoter and proteins involved in IL-4 signaling. Soluble recombinant IL-4 receptor lacks transmembrane and cytoplasmic activating domains and can therefore sequester IL-4 without mediating cellular activation. We report the results of initial clinical trials, which demonstrate clinical efficacy of this naturally occurring IL-4 antagonist as a therapeutic agent in asthma.

Expression of interleukin-4 in the epidermis of transgenic mice results in a pruritic inflammatory skin disease: an experimental animal model to study atopic dermatitis

Atopic dermatitis, a common, chronic, inflammatory skin disease that occurs with increasing prevalence, is characterized by hyperactivated cytokines of helper T cell subset 2 and is frequently associated with staphylococcal infection. An experimental animal model of atopic dermatitis induced by transgenically introduced cytokine is not available. We generated a transgenic mouse line expressing epidermal interleukin-4, a critical cytokine of helper T cell subset 2. Here we show that transgenic mice spontaneously developed a pruritic inflammatory skin disease reproducing all key features of human atopic dermatitis, including xerosis, conjunctivitis, inflammatory skin lesions, Staphylococcus aureus infection, histopathology of chronic dermatitis with T cell, mast cell, macrophage-like mononuclear cell, and eosinophil infiltration, and elevation of total serum IgE and IgG1. The onset and early progression of skin disease coincided with increased total serum IgE and IgG1. The mouse disease occurred at a 43% annual incidence rate and primarily affected the poorly haired skin: ear (100%), neck (65%), eye (53%), face (29%), tail (12%), leg (12%), and torso (6%). As a group the affected transgenic mice manifested with a skin disorder that fulfilled the clinical diagnostic criteria established for atopic dermatitis in human patients. Pending further characterization to authenticate it as a model of atopic dermatitis, this experimental animal model of pruritic inflammatory skin disease may facilitate investigations for the roles of interleukin-4 in cutaneous inflammation and skin infection in human patients.

The ACVD task force on canine atopic dermatitis (I): incidence and prevalence

There is an increasing incidence of atopic diseases (asthma, allergic rhinitis and atopic dermatitis) in humans, especially in developed countries. Although there is a genetic predisposition to the development of these diseases, the rapid rise in incidence is suspected to be caused by environmental rather than genetic factors. Neither the incidence nor the prevalence of atopic dermatitis in the general canine population has been studied. As many of the environmental factors associated with the increasing incidence of atopic dermatitis in humans are consistently found in the environment of dogs, it would seem likely that a similar increase in the incidence of this disease would be occurring also in dogs. Epidemiological studies of canine atopic dermatitis are needed to characterize the incidence and prevalence of atopic dermatitis, and to further study the factors that contribute to the development of this disease.

Environmental factors favoring the allergen-specific Th2 response in allergic subjects

Allergen-reactive type 2 helper T cells (Th2) play a triggering role in the activation and/or recruitment of IgE antibody-producing B cells, mast cells, and eosinophils, i.e., the cellular triad involved in the allergic inflammation. Interleukin (IL)-4 production at the time of antigen presentation to the Th cell is critical for the development of Th2 cells. Other cytokines, such as IL-1 and IL-10, and hormones, such as calcitriol and progesterone, also play a positive role. In contrast, cytokines such as interferon (IFN)-alpha, IFN-gamma, IL-12, and transforming growth factor (TGF)-beta, and relaxin play a negative regulatory role on the development of Th2 cells. However, the mechanisms underlying the preferential activation by environmental allergens of Th2 cells in atopic individuals still remain obscure. Some gene products selectively expressed in Th2 cells or selectively controlling the expression of IL-4 have recently been described. Moreover, cytokines and other gene products that dampen the production of IL-4, as well as the development and/or the function of Th2 cells, have been identified. These findings allow us to suggest that the upregulation of genes controlling IL-4 expression and/or abnormalities of regulatory mechanisms of Th2 development and/or function may be responsible for Th2 responses against common environmental allergens in atopic subjects.

Cellular and immunologic mechanisms in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease that is frequently associated with respiratory allergies. Atopic dermatitis develops as a result of a complex interrelationship of environmental, immunologic, genetic, and pharmacologic factors. Efforts to understand the relative contributions of these factors have led to research seeking to identify the relevant effector cells and mediators involved in the pathogenesis of atopic dermatitis. These factors include the pattern of local cytokine release, the differentiation of helper T cells, multiple roles of IgE, skin-directed cell responses, infectious agents, and superantigens. This article reviews these cellular and immunologic mechanisms underlying atopic dermatitis and discusses how an understanding of their role in the inflammatory process may lead to improved treatments for atopic dermatitis.

Dysregulated activation of activator protein 1 in keratinocytes of atopic dermatitis patients with enhanced expression of granulocyte/macrophage-colony stimulating factor

Keratinocytes of patients with atopic dermatitis produce high amounts of granulocyte/macrophage colony-stimulating factor, a factor essential for dendritic cell function and thus for the development of skin immune responses. In contrast to keratinocytes cultured from nonatopic, healthy individuals, granulocyte/macrophage colony-stimulating factor mRNA could be detected in unstimulated cultures of atopic dermatitis keratinocytes, and phorbol myristate acetate induced much greater granulocyte/macrophage colony-stimulating factor mRNA levels in these cells, although the decay kinetics were not altered. Using reporter gene (chloramphenicol acetyl transferase) analysis, a minimal granulocyte/macrophage colony-stimulating factor promoter was shown to confer constitutive and phorbol-myristate-acetate-induced regulation of transcriptional activity in keratinocytes, and significantly higher levels of chloramphenicol acetyl transferase activity were measured in lysates of unstimulated and phorbol-myristate-acetate-treated atopic dermatitis keratinocytes than in control keratinocyte cultures. Electrophoretic mobility shift assays showed that low levels of NF-kappa B binding activity could be induced by phorbol myristate acetate in both normal and atopic dermatitis keratinocytes. By contrast, activator protein 1 complexes were efficiently induced, and they were invariably present at higher levels in nuclear lysates of atopic dermatitis keratinocytes. Atopic dermatitis keratinocyte nuclear lysates had higher constitutive levels of c-Jun, and phorbol myristate acetate promoted an earlier and stronger expression of c-Jun, JunB, and of the phosphorylated forms of c-Fos. A dysregulated activation of activator protein 1 may be implicated in the molecular mechanisms leading to increased granulocyte/macrophage colony-stimulating factor expression in atopic dermatitis keratinocytes. J Invest Dermatol 115:1134-1143 2000

Characterization of P5, a novel NFAT/AP-1 site in the human IL-4 promoter

Interleukin 4 (IL-4) gene expression is controlled at the level of transcription by the complex interactions of multiple factors that bind to a proximal promoter region. Nuclear factor of activated T cells (NFAT) can bind up to five purine-rich sequences in the IL-4 promoter termed the P elements (P0-P4). In this paper, we characterize a novel P element in the upstream region of the human IL-4 promoter that we term P5. P5 shares a core NFAT motif ((-353)GGAAA(-357)) and additional sequence similarity with the other P elements and supported strong interactions between the NFATp DNA-binding domain (DBD) and the AP-1 proteins cFos and cJun in DNA-binding assays. Inducibility of the IL-4 promoter was significantly impaired in a reporter construct in which the P5 element was mutated in the context of the full-length promoter. We conclude that P5 represents a novel IL-4 promoter P element that contributes to IL-4 promoter inducibility.

Glucocorticoids inhibit calcium- and calcineurin-dependent activation of the human IL-4 promoter

The mechanism by which glucocorticoids (GC) inhibit IL-4 gene expression is currently unknown. In T lymphocytes, IL-4 gene expression is regulated at the level of transcription by increases in intracellular calcium concentration and by the calcium-activated phosphatase calcineurin. In this paper we report that dexamethasone (Dex) inhibits calcium ionophore-induced activation of the human IL-4 promoter in transiently transfected Jurkat T cells. Inhibition of the promoter by Dex is dependent on expression of the GC receptor (GR), because it does not occur in GR-deficient cells. Dex also represses activation of the promoter induced by cotransfecting cells with a constitutively active mutant of calcineurin. Using a series of deletion constructs, we show that the proximal 95 bp of the IL-4 promoter contain a Dex-sensitive regulatory element. This region contains the P1 sequence, a proximal binding site for NF-AT. A calcium-induced but Dex-inhibited nuclear complex containing NF-AT binds to the P1 element in EMSA. Using immunoprecipitation under nondenaturing conditions, we found that the GRalpha isoform coprecipitates with NF-ATc in nuclear extracts of calcium ionophore- and Dex-treated cells. Taken together, our results show that GC inhibit IL-4 gene expression by interfering with NF-AT-dependent transactivation of the proximal human IL-4 promoter.

Cicatricial pemphigoid: serial titres of circulating IgG and IgA antibasement membrane antibodies correlate with disease activity

We have recently shown in a cohort of patients (n = 67) with mucous membrane pemphigoid, 63 of whom had cicatricial pemphigoid (CP), that the presence of both IgG and IgA circulating antibasement membrane zone antibodies was associated with a more severe and persistent disease. In this study we sought to ascertain whether in CP, serial titres of IgG and IgA might provide a reliable marker of disease activity. Serum titres for IgG and IgA antibodies were assayed at 6- to 12-monthly intervals in 56 patients over 32.2 +/- 20.3 (mean +/- SD) months. Antibody titres were correlated with the clinical score recorded at each follow-up visit. Sequential titres for both IgG (P < 0.001) and IgA (P = 0.015) were significantly associated with variations in disease activity. Greatest improvement was seen in patients with the greatest change in either IgG or IgA antibody titre. We suggest that serial antibody titres may therefore be useful in the assessment and management of CP.

Evidence for suppressed activity of the transcription factor NFAT1 at its proximal binding element P0 in the IL-4 promoter associated with enhanced IL-4 gene transcription in T cells of atopic patients

Allergen-specific T cells in atopic patients are polarized IL-4-producing Th2 cells, promoting IgE synthesis by B cells. The molecular basis for increased IL-4 gene expression in atopy is not fully understood. IL-4 gene regulation in general involves the nuclear factor of activated T cells (NFAT) family of transcription factors, of which NFAT1 and NFAT2 are most prominent in peripheral T cells. Recently, a unique inhibitory role of NFAT1 in IL-4 gene control was shown in the mouse. In a series of electrophoretic mobility shift assays with protein extracts of highly polarized Th2 clones from atopics and Th1 clones from controls we compared DNA-binding activities at the two NFAT-binding elements P0 and P1 of the crucial proximal human IL-4 promoter. At the most proximal P0 site, NFAT-containing complexes devoid of NFAT2 were readily inducible in the Th1 clones, but hardly or not in the Th2 clones. In contrast, both in Th1 and Th2 clones NFAT-containing complexes were strongly inducible at the P1 site, consisting of NFAT2 and a P0-compatible NFAT activity, without apparent differences between Th1 and Th2 clones. Like in Th2 clones, suppressed NFAT-P0 complex formation was observed also at the polyclonal level in peripheral blood mononuclear cells (PBMC) of three of five severe atopic dermatitis patients with strongly elevated serum IgE levels, but not in control PBMC. These findings suggest that high-level IL-4 production in atopic Th2 cells is associated with selective reduction of suppressive NFAT1 activity at the IL-4 P0 element and that some patients with this multifactorial disease may have a putative systemic disorder at this level.

Regulation of Allergic Inflammation and Eosinophil Recruitment in Mice Lacking the Transcription Factor NFAT1: Role of Interleukin-4 (IL-4) and IL-5

Transcription factors of the NFAT (nuclear factor of activated T cells) family regulate the expression of many genes encoding immunoregulatory cytokines and cell surface proteins during the immune response. The NFAT protein NFAT1 (NFATp) is expressed and functional in T cells, B cells, mast cells, and natural killer cells. Here we report a detailed analysis of the enhanced eosinophil responses of NFAT1-deficient mice, observed in an in vivo model of allergic inflammation. In addition to the pleural eosinophilia described previously, NFAT1−/− mice that have been sensitized with antigen display a significant increase, relative to wild-type mice, in the numbers of eosinophils in bone marrow and peripheral blood. After restimulation with antigen in vitro, antigen-responsive T cells from the draining lymph nodes of NFAT1−/− mice show increased expression of mRNA encoding the Th2 cytokines interleukin-4 (IL-4), IL-5, and IL-13. Consistent with this finding, there is a pronounced increase in the levels of IL-5 and IL-13 in the pleural cavities of sensitized NFAT1−/− mice after allergen challenge in vivo. Furthermore, development of eosinophilia depends on overexpression of IL-4 and IL-5, because it is strongly inhibited by administration of neutralizing antibodies to either of these cytokines. These results indicate that NFAT1-deficient mice are prone to develop a classically allergic phenotype characterized by eosinophilia and increased production of Th2 cytokines. Thus, the presence of NFAT1 might inhibit the allergic response, perhaps by interfering with the development of Th2 immune responses, and the lack or dysfunction of NFAT1 could potentially underlie certain cases of atopic disease.

Regulation of Allergic Inflammation and Eosinophil Recruitment in Mice Lacking the Transcription Factor NFAT1: Role of Interleukin-4 (IL-4) and IL-5

Transcription factors of the NFAT (nuclear factor of activated T cells) family regulate the expression of many genes encoding immunoregulatory cytokines and cell surface proteins during the immune response. The NFAT protein NFAT1 (NFATp) is expressed and functional in T cells, B cells, mast cells, and natural killer cells. Here we report a detailed analysis of the enhanced eosinophil responses of NFAT1-deficient mice, observed in an in vivo model of allergic inflammation. In addition to the pleural eosinophilia described previously, NFAT1−/− mice that have been sensitized with antigen display a significant increase, relative to wild-type mice, in the numbers of eosinophils in bone marrow and peripheral blood. After restimulation with antigen in vitro, antigen-responsive T cells from the draining lymph nodes of NFAT1−/− mice show increased expression of mRNA encoding the Th2 cytokines interleukin-4 (IL-4), IL-5, and IL-13. Consistent with this finding, there is a pronounced increase in the levels of IL-5 and IL-13 in the pleural cavities of sensitized NFAT1−/− mice after allergen challenge in vivo. Furthermore, development of eosinophilia depends on overexpression of IL-4 and IL-5, because it is strongly inhibited by administration of neutralizing antibodies to either of these cytokines. These results indicate that NFAT1-deficient mice are prone to develop a classically allergic phenotype characterized by eosinophilia and increased production of Th2 cytokines. Thus, the presence of NFAT1 might inhibit the allergic response, perhaps by interfering with the development of Th2 immune responses, and the lack or dysfunction of NFAT1 could potentially underlie certain cases of atopic disease.

Long-term therapy with recombinant interferon-gamma (rIFN-gamma) for atopic dermatitis

BACKGROUND

Interferon-gamma (IFN-gamma) is a potent cytokine that modulates IL-4-induced immune responses. Atopic dermatitis is associated with increased IgE levels and decreased IFN-gamma production. Recent phase I and phase II studies have suggested that short-term rIFN-gamma therapy is effective in the treatment of severe atopic dermatitis.

OBJECTIVE

We evaluated the safety and efficacy of long-term use of rIFN-gamma for severe atopic dermatitis.

METHODS

Fifteen patients were treated for a minimum of 22 months with 50 micrograms/m2 rIFN-gamma qd or qod. Patients were monitored every 3 months for safety, efficacy, and linear growth in pediatric patients.

RESULTS

Data represented a total of 47 patient years, which included 29 pediatric patient years. There was a statistically significant decrease in mean total body surface area involvement over time (P < .001, ANOVA). Mean total body surface area involvement was 61.6% at baseline and decreased to 18.5% at 24 months (P < .001). Likewise, there was a statistically significant decrease in the clinical severity parameters. The mean total clinical severity score was 11.4 at baseline and decreased to 6.3 at 24 months (P < .001). Statistically significant decreases in WBC, neutrophil counts, and eosinophil counts were observed compared with baseline counts. No other significant laboratory abnormalities or growth problems were seen.

CONCLUSIONS

We conclude that rIFN-gamma appears to be a safe long-term therapy for patients with severe atopic dermatitis.

Influence of both TCR repertoire and severity of the atopic status on the cytokine secretion profile of Parietaria officinalis-specific T cells

Peripheral blood mononuclear cells (PBMC) from both nonatopic and Parietaria officinalis-sensitive donors proliferated in response to the allergen Par o 1 and developed into Par o 1-specific T cell lines and clones, which also showed reactivity for Par o 1-derived peptides. Virtually all Par o 1-specific T cell lines and large numbers of Par o 1-specific T cell clones proliferated in response to two Par o 1 nonapeptides (p92 and p96), which probably contain immunodominant epitopes of the Par o 1 allergen. Both p92- and p96-specific T cell clones showed the ability to produce IFN-gamma, but p92-specific T cell clones produced significantly lower amounts of IL-4 and IL-5 than p96-specific T cell clones, indicating that distinct epitopes, able to elicit functionally different T helper cell responses, may coexist in Par o 1. However, p92-specific T cell clones derived from atopic subjects with high IgE serum levels (high IgE producers) secreted significantly higher amounts of IL-4 and IL-5 than corresponding T cell clones generated from nonatopic subjects or patients with low IgE serum levels (low IgE producers), whereas p96-specific T cell clones secreted high IL-4 and IL-5 concentrations irrespective of whether they derived from high or low IgE producers. The addition of IL-4 and anti-IL-12 mAb to bulk culture significantly up-regulated the development of p92-specific T cells into IL-4-producing cells, whereas the addition of IL-12 and anti-IL-4 mAb shifted the differentiation of p96-specific T cells towards IFN-gamma-producing cells. Taken together, these results suggest that the cytokine profile of allergen-specific T cells is influenced by both the T cell receptor repertoire and the severity of atopic status and can be modulated, at least in vitro, by stimulation with the specific peptide in the presence, or after removal, of appropriate cytokines.

The TH1/TH2 paradigm in allergy

Recent evidence has been accumulated to suggest that allergen-reactive type 2 helper T cells (Th2) play a triggering role in the activation and/or recruitment of IgE antibody-producing B cells, mast cells and eosinophils, i.e. the cellular triad involved in the allergic inflammation. Interleukin (IL)-4 production by a still unknown cell type (T cell subset, mast cell/basophil?) at the time of antigen presentation to the Th cell is critical for the development of Th2 cells. Other cytokines, such as IL-1 and IL-10, and hormones, such as calcitriol and progesterone, also play a favoring role. In contrast, cytokines such as interferon (IFN-alpha, IFN-gamma, IL-12 and transforming growth factor (TGF)-beta, and hormones, play a negative regulatory role on the development of Th2 cells. However, the mechanisms underlying the preferential activation by environmental allergens of Th2 cells in atopic individuals still remain obscure. Some gene products selectively expressed in Th2 cells or selectively controlling the expression of IL-4 have recently been described. Moreover, cytokines and other gene products that dampen the production of IL-4, as well as the development and/or the function of Th2 cells, have been identified. These findings allow us to suggest that the up-regulation of genes controlling IL-4 expression and/or abnormalities of regulatory mechanisms of Th2 development and/or function may be responsible for Th2 responses against common environmental allergens in atopic people. The new insights in the pathophysiology of T cell responses in atopic diseases provide exciting opportunities for the development of novel immunotherapeutic strategies. They include the induction of nonresponsiveness in allergen-specific Th2 cells by allergen peptides or redirection of allergen-specific Th2 responses by Th1-inducing cytokines, altered peptide ligands, allergens incorporated into recombinant microorganisms or bound to appropriate adjuvants, and plasmid DNA vaccination. In severe atopic patients, the possibility of nonallergen-specific immunotherapeutic regimens designed to target Th2 cells or Th2-dependent effector molecules, such as specific IL-4 transcription factors, IL-4, IL-5 and IgE, may also be suggested.

Biology and genetics of atopic disease

Several immunological disorders including allergic rhinitis, bronchial asthma, atopic dermatitis, food allergies, urticaria, nonhereditary angioedema, systemic anaphylaxis, and allergic conjunctivitis are associated with a positive family history, and share a positive response in the Prausnitz-Kuster (wheal and flare) reaction. Studies have shown that 20-30% of the population has a strong genetic predisposition for this condition, termed atopy, whose hallmark is a greatly elevated serum IgE concentration. A great deal is known about the cellular interactions that mediate the sensitization, immediate and late-phase reactions that follow encounters with allergen, as well as about the cell surface and signaling events that result in mediator release from inflammatory cells. Less is known of the genes that confer genetic predisposition for atopy; however, a worldwide effort to identify atopy genes is making significant progress.

Human keratin diseases: hereditary fragility of specific epithelial tissues

Keratins are heteropolymeric proteins which form the intermediate filament cytoskeleton in epithelial cells. Since 1991, mutations in several keratin genes have been found to cause a variety of human diseases affecting the epidermis and other epithelial structures. Epidermolysis bullosa simplex (EBS) was the first mechanobullous disease for which the underlying genetic lesion was found, with mutations in both the K5 and K14 genes rendering basal epidermal keratinocytes less resilient to trauma, resulting in skin fragility. The site of mutation in the keratin protein correlates with phenotypic severity in this disorder. Since mutations were identified in the basal cell keratins, the total number of keratin genes associated with diseases has risen to eleven. The rod domains of suprabasal keratins K1 and K10 are mutated in bullous congenital ichthyosiform erythroderma (BCIE; also called epidermolytic hyperkeratosis, EH) and mosaicism for K1/K10 mutations results in a nevoid distribution of EH. An unusual mutation in the VI domain of K1 has also been found to cause diffuse non-epidermolytic palmoplantar keratoderma (DNEPPK). Mutations in palmoplantar specific keratin K9 cause epidermolytic palmoplantar keratoderma (EPPK) and mutations in the late differentiation suprabasal keratin K2e cause ichthyosis bullosa of Siemens (IBS). In the last year or so, mutations were discovered in differentiation specific keratins K6a and K16 causing pachyonychia congenita type 1 and K17 mutations occur in pachyonychia congenita type 2. K16 and K17 mutations have also been reported to produce phenotypes with little or no nail changes: K16 mutations can present as focal non-epidermolytic palmoplantar keratoderma (NEPPK) and K17 mutations can result in a phenotype resembling steatocystoma multiplex. Recently, mutation of mucosal keratin pair K4 and K13 has been shown to underlie white sponge nevus (WSN). This year, the first mutations in a keratin-associated protein, plectin, were shown to cause a variant of epidermolysis bullosa associated with late-onset muscular dystrophy (MD-EBS). An unusual mutation has been identified in K5 which is responsible for EBS with mottled pigmentation and genetic linkage analysis suggests that the hair disorder monilethrix is likely to be due to a mutation in a hair keratin. The study of keratin diseases has led to a better understanding of the importance of the intermediate filament cytoskeleton and associated connector molecules in maintaining the structural integrity of the epidermis and other high stress epithelial tissues, as well as allowing diagnosis at the molecular level thus facilitating prenatal testing for this heterogeneous group of genodermatoses.