IL-4 induces the intracellular expression of the alpha chain of the high-affinity receptor for IgE in in vitro-generated dendritic cells

Topical Application of Galgeunhwanggeumhwangryeon-Tang Recovers Skin-Lipid Barrier and Ameliorates Inflammation via Filaggrin-Thymic Stromal Lymphopoietin-Interleukin 4 Pathway

Background and objectives: The purpose of this study was to confirm the effect of Galgeunhwanggeumhwangryeon-tang (GGRT) on the skin barrier integrity and inflammation in an atopic dermatitis-like animal model. Materials and Methods: The model was established using lipid barrier elimination (LBE) in BALB/c mice. Ceramide 3B, a control drug, and GGRT were applied to the skin of LBE mice. Gross observation and histological examination were combined with measurement of skin score, trans-epidermal water loss, and pH. The expression of filaggrin, kallikrein-related peptidase 7 (KLK7), protease-activated receptor-2 (PAR-2), thymic stromal lymphopoietin (TSLP), and interleukin 4 (IL-4) was examined. Results: The effect of GGRT on atopic dermatitis was estimated in silico using two individual gene sets of human atopic dermatitis. In animal experiments, GGRT treatment reduced atopic dermatitis-like symptoms, as confirmed via gross and histological observations, skin score, pH change, and trans-epidermal water loss. The expression level of filaggrin increased in the skin of GGRT-treated mice compared to that in the LBE group. The expression levels of KLK7, PAR2, TSLP, and IL-4 were decreased in GGRT-treated mice skin compared to those in LBE mice. Conclusions: We demonstrated that GGRT restored the skin barrier and reduced inflammatory reactions in a murine model of atopic dermatitis.

Virus-specific IgE enhances airway responsiveness on reinfection with respiratory syncytial virus in newborn mice

BACKGROUND

Respiratory syncytial virus (RSV)-specific IgE is a component of the host response to RSV infection, but its role in the subsequent enhancement of altered airway responsiveness is unknown.

OBJECTIVE

To define the role of RSV-specific IgE in the enhancement of airway responsiveness on reinfection of newborn mice.

METHODS

Mice were infected as newborns with RSV and were reinfected 5 weeks later. The role of IgE was determined by documenting RSV-specific IgE response after neonatal infection, and by assessing airway responsiveness on reinfection.

RESULTS

After neonatal infection, wild-type (WT) mice developed an RSV-specific IgE response. On reinfection, these mice developed enhanced airway hyperresponsiveness (AHR), airway eosinophilia, and mucus hyperproduction, and their T-cell cytokine response was skewed toward a T(H)2 phenotype. None of these altered responses developed on reinfection of IL-4(-/-)/IL-13(-/-) mice, and no RSV-specific IgE could be detected after neonatal infection of these mice. Fc epsilon RI(-/-) mice did not develop the enhanced AHR on reinfection, and airway eosinophilia and mucus production were significantly attenuated. These responses could be restored in deficient mice reconstituted with WT mast cells. In RSV-infected newborn WT mice, administration of anti-IgE prevented the enhancement of AHR and attenuated eosinophilia and mucus hyperproduction on reinfection, an effect that was associated with diminished T(H)2 cytokine production and increased IFN-gamma production.

CONCLUSION

Respiratory syncytial virus-specific IgE enhances the development of T(H)2-biased airway responsiveness on reinfection of mice initially infected as newborns.

Gender-medicine aspects in allergology

Despite the identical immunological mechanisms activating the release of mediators and consecutive symptoms in immediate-type allergy, there is still a clear clinical difference between female and male allergic patients. Even though the risk of being allergic is greater for boys in childhood, almost from adolescence onwards it seems to be a clear disadvantage to be a woman as far as atopic disorders are concerned. Asthma, food allergies and anaphylaxis are more frequently diagnosed in females. In turn, asthma and hay fever are associated with irregular menstruation. Pointing towards a role of sex hormones, an association of asthma and intake of contraceptives, and a risk for asthma exacerbations during pregnancy have been observed. Moreover, peri- and postmenopausal women were reported to increasingly suffer from asthma, wheeze and hay fever, being even enhanced by hormone replacement therapy. This may be on account of the recently identified oestradiol-receptor-dependent mast-cell activation. As a paradox of nature, women may even become hypersensitive against their own sex hormones, resulting in positive reactivity upon intradermal injection of oestrogen or progesterone. More importantly, this specific hypersensitivity is associated with recurrent miscarriages. Even though there is a striking gender-specific bias in IgE-mediated allergic diseases, public awareness of this fact still remains minimal today.

Anti-IgE and other antibody targets in asthma

Asthma is a heterogeneous disorder of unknown etiology that manifests as recurrent episodes of coughing, wheezing, and breathlessness. These symptoms are often debilitating and exacerbations usually are unexpected, resulting in work or school absences, limitations in activity, reduced quality of life, and personal and economic hardships. Over the past several decades, a great deal has been learned about asthma pathophysiology, and currently available therapies have revolutionized asthma treatment. However, asthma remains a global public health problem, and the hope is that newer therapies targeting specific biological mediators of asthma, particularly antibody-mediated therapies, offer exciting new modes to the control of this disease. We will review some of these therapies, with the majority of attention devoted to anti-IgE therapy which has been approved for treatment of adult and childhood asthma by the US Food and Drug Administration (FDA) since 2003.

Langerhans Cell Receptors

Langerhans cells (LC) are a subtype of dendritic cells, which reside in the epidermis. LCs are antigen-presenting cells that originate in bone marrow and enter the epidermis through blood vessels. LCs exhibit a variety of antigen receptors that are able to respond to a wide range of antigens. Within the last two decades, these receptors have been the subject of considerable research. This article focuses on the rapidly growing body of knowledge with respect to the functions of LC receptors.

New developments in FcepsilonRI regulation, function and inhibition

The high-affinity Fc receptor for IgE (FcepsilonRI), a multimeric immune receptor, is a crucial structure for IgE-mediated allergic reactions. In recent years, advances have been made in several important areas of the study of FcepsilonRI. The first area relates to FcepsilonRI-mediated biological responses that are antigen independent. The second area encompasses the biological relevance of the distinct signalling pathways that are activated by FcepsilonRI; and the third area relates to the accumulated evidence for the tight control of FcepsilonRI signalling through a broad array of inhibitory mechanisms, which are being developed into promising therapeutic approaches.

The high-affinity IgE receptor (FcepsilonRI): a critical regulator of airway smooth muscle cells?

The airway smooth muscle (ASM) has been typically described as a contractile tissue, responding to neurotransmitters and inflammatory mediators. However, it has recently been recognized that ASM cells can also secrete cytokines and chemokines and express cell adhesion molecules that are important for the perpetuation and modulation of airway inflammation. Recent progress has revealed the importance of IgE Fc receptors in stimulating and modulating the function of these cells. In particular, the high-affinity receptor for IgE (FcepsilonRI) has been identified in primary human ASM cells in vitro and in vivo within bronchial biopsies of atopic asthmatic individuals. Moreover, activation of this receptor has been found to induce marked increases in the intracellular calcium concentrations and T helper 2 cytokines and chemokines release. This and other evidence discussed in this review provide an emerging view of FcepsilonR/IgE network as a critical modulator of ASM cell function in allergic asthma.

Transport of the IgE receptor alpha-chain is controlled by a multicomponent intracellular retention signal

The human high affinity IgE receptor (FcepsilonRI) is a central component of the allergic response and is expressed as either a trimeric alphagamma2 or tetrameric alphabetagamma2 complex. It has been previously described that the cytoplasmic domain (CD) of the alpha-chain carries a dilysine motif at positions -3/-7 from the C terminus that functions in intracellular retention prior to assembly with other FcepsilonRI subunits. In this report we have further explored the role of the -3/-7 dilysine signal in controlling steady-state alpha-chain transport by mutational analysis and found little surface expression of a -3/-7 dialanine alpha-chain mutant but significant Golgi localization. We compared the transport properties of a series of alpha-chain cytoplasmic domain truncation mutants and observed that truncation mutants lacking 23 or more C-terminal residues showed a dramatic increase in steady-state transport suggesting a role for the membrane-proximal CD sequence in alpha-chain retention. By performing alanine-scanning mutagenesis we identified a dilysine sequence (Lys(212)-Lys(216)) proximal to the transmembrane domain (TMD) that is important for both alpha-chain cell-surface expression and intracellular stability. Furthermore, co-mutation of the Lys(212)-Lys(216) residues with the -3/-7 dilysine signal produced a dramatic increase in alpha-chain surface expression that was further increased by co-mutation of the lone charged residue (Asp(192)) in the TMD thereby defining three regions that function to regulate alpha-chain transport and in a highly synergistic manner.

Human airway smooth muscle cells express the high affinity receptor for IgE (Fc epsilon RI): a critical role of Fc epsilon RI in human airway smooth muscle cell function

Several reports suggest that activated airway smooth muscle (ASM) cells are capable of generating various proinflammatory mediators, including cytokines and chemokines. However, little is known about the mechanism involved in this process. In this regard, we have examined the expression and the role of the high affinity IgE receptor (Fc epsilonRI) by ASM cells. Human ASM cells were found to constitutively express transcripts coding for alpha, beta, and gamma subunits of Fc epsilonRI. Flow cytometry and Western blot analysis confirmed the expression of Fc epsilonRI alpha-chain protein. Interestingly, Fc epsilonRI alpha-chain immunoreactivity was also demonstrated in smooth muscle within bronchial biopsies of asthmatic subjects. Cross-linking of Fc epsilonRI induced mobilization of free calcium in ASM cells, one of the critical signals to trigger smooth muscle contraction. Furthermore, cultured ASM cells released IL-4, IL-13, IL-5, and eotaxin but not IFN-gamma, when sensitized with IgE followed by anti-IgE Ab cross-linking. The addition of anti-Fc epsilonRI alpha-chain Abs directed against IgE binding site inhibited this release. Taken together, these results suggest a potential new and important mechanism by which ASM cells may participate in airway inflammation and bronchoconstriction associated with allergic asthma.

The role of dendritic cell subtypes in the pathophysiology of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is an inflammatory, immunologically mediated skin disease characterized by a T helper type 2 cell-predominant phenotype initially with additional acquisition of T helper type 1 cell phenotype during the chronic eczematous phase. Compelling evidence presented here suggests that two types of dendritic cells (DC), myeloid DC (mDC) and plasmacytoid DC (pDC), are important in the pathogenesis of AD.

METHODS

We reviewed the current literature and summarized key information about the role of mDC and pDC in the pathogenesis of AD.

RESULTS

Langerhans cells and inflammatory dendritic epidermal cells, which bear the high-affinity receptor for immunoglobulin E on their cell surface, are hypothesized to contribute to the pathogenesis of AD. pDC, Which play an important role in the defence against viral infections, have also been shown to express high-affinity receptor for immunoglobulin E.

CONCLUSION

Immunoglobulin E receptor-bearing mDC and pDC subtypes in the blood and the skin of patients with AD are of critical immunologic importance in the complex pathophysiologic network of AD. Targeting mDC and pDC subtypes may lead to effective new therapies for the management of AD.

Co-cultivation of mast cells and Fc epsilon RI alpha+ dendritic-like cells from human hip bone marrow

BACKGROUND

Mast cells contribute to the pathogenesis of asthma and allergy through the release of a plethora of pro-inflammatory mediators and cytokines. Their study is hampered by the difficult access to human tissue samples. Human mast cells have been cultured from CD34+ progenitors in the bone marrow of normal volunteers following iliac crest bone marrow biopsy but this is invasive. Hip bone marrow could provide a more convenient less invasive source of mast cell progenitors.

OBJECTIVE

To characterize mast cells cultured from human bone marrow obtained at routine hip surgery.

METHODS

Mononuclear cells were isolated from the bone marrow reamings of patients undergoing routine hip replacement surgery and were cultured with recombinant stem cell factor (SCF), IL-6 and IL-10. Cell surface markers were examined using flow cytometry, protease expression monitored using immunohistochemistry, histamine measured by radioenzymic assay, Ca2+ responses analysed using ratiometric Ca2+ imaging, and ion currents recorded via the patch-clamp technique.

RESULTS

Mast cells were absent at baseline, but accounted for 65 +/- 7% of cells after 8-12 weeks of culture, equating to a mean 0.6 +/- 0.14 x 10(6) mast cells per culture. Fifty-three percent of tryptase+ cells also contained chymase. The remaining cells comprised a population of large CD1a+ HLA-DR+ and Fc epsilon RI alpha+ cells, most likely dendritic cells. All mast cells expressed CD117 and the high-affinity IgE receptor alpha-chain (Fc epsilon RI alpha) constitutively, and developed a Ca2+ response following IgE-dependent activation. These cells exhibited 7.8 +/- 2.9% net IgE-dependent histamine release, and demonstrated a similar ion channel profile to human lung mast cells. In particular, the intermediate conductance Ca(2+)-activated K+ channel opened following IgE-dependent activation.

CONCLUSIONS

Mast cells grown from human hip marrow provide a rich non-invasive source of functionally mature mast cells. In addition, this culture system may be useful for the generation of Fc epsilon RI alpha+ dendritic cells.

Anti-IgE antibodies for the treatment of asthma

PURPOSE OF REVIEW

Allergic asthma is a hypersensitivity reaction initiated by immunologic mechanisms mediated by IgE antibodies. IgE plays a central role in the initiation and propagation of the inflammatory cascade and thus the allergic response. Targeting factors involved in the allergic response, such as IgE, is a novel strategy for new therapies. Attenuating allergic disease by specifically inhibiting IgE and the development of the monoclonal anti-IgE antibody, omalizumab, were major breakthroughs in asthma management.

RECENT FINDINGS

Several studies have shown that omalizumab has significant anti-inflammatory effects and that it may act on multiple components of the inflammatory cascade. Specific binding of IgE by omalizumab reduces both the early allergic response and the late allergic response and symptoms of IgE-mediated allergy. The long-term clinical efficacy of omalizumab has been demonstrated along with improvements in quality of life. As add-on therapy in severe asthma, omalizumab reduces the requirement for inhaled corticosteroids and improves disease control. Clinical studies have shown that the patients who benefit most from omalizumab therapy are those at high risk of exacerbations, those with poorly controlled and/or severe asthma, and those with IgE-mediated comorbidities.

SUMMARY

Omalizumab is a significant addition to current asthma treatments and shows great promise as a therapy for allergic asthma and for patients with concomitant allergic rhinitis. This is particularly true for difficult-to-treat patients with moderate to severe allergic asthma who have poorly controlled disease on conventional therapies, experience severe adverse effects secondary to high-dose or prolonged corticosteroid treatment, have frequent exacerbations, and/or are at high risk of hospitalization. Future studies will continue to investigate the anti-inflammatory mechanisms of anti-IgE therapy. Because many of these mechanisms are common to all IgE-mediated allergic diseases, the efficacy of omalizumab in other allergic diseases should be further explored.

Immunoglobulin E-bearing antigen-presenting cells in atopic dermatitis

Human antigen-presenting cells (APCs) bind monomeric immunoglobulin E (IgE) via the high-affinity IgE receptor, Fc epsilon RI. Surface expression of this trimeric structure is strongly associated with the atopic status of the donors, and maximal levels are observed on Langerhans cells (LC) and inflammatory dendritic epidermal cells (IDEC) in atopic dermatitis (AD). Although intracellular expression of the Fc epsilon RI alpha-chain is induced by interleukin-4 (IL-4), the upregulation of surface levels on dendritic cells (DC) from atopics is due to enhanced expression of the Fc epsilon RI gamma-chain and stabilization by binding of its ligand IgE. A characteristic function of Fc epsilon RI-bearing APCs is the specific uptake and processing of IgE-bound allergens, which is followed by T-cell stimulation. In AD, DC-mediated presentation of aeroallergens penetrating the epidermis is thought to induce an IgE-mediated, delayed-type hypersensitivity reaction. In addition, different Fc epsilon RI-bearing APC subsets in AD skin might regulate inflammatory processes through the production of Th1/Th2-polarizing signals, proinflammatory cytokines, chemokines, and factors that are involved in the induction of tolerance.

Regulation of antigen-specific versus by-stander IgE production after antigen sensitization

IgE is critical in the pathogenesis of allergic disorders. In this report, we investigated the differential regulation of antigen-specific and by-stander IgE. Ovalbumin (OVA) immunization did not increase IgE producing cells in the spleen, but significantly enhanced the intracellular IgE content of all IgE+ cells. In contrast, OVA induced a significant increase of IgE+ cells in the draining lymph nodes (LN). Furthermore, OVA-specific IgE was detected only in the ex vivo cultures of the draining LN but not the spleen cells, while total IgE was increased in both cultures. These results indicated that antigen-specific IgE was mainly produced in the draining LN, while the spleen was a major source for by-stander IgE. Anti-IL-4, but not anti-IL-13, antibody blocked the expansion of IgE producing cells in the draining LN as well as systemic OVA-specific and total IgE levels, indicating IL-4 was important in both antigen-specific IgE generation and total IgE upregulation.

Transforming Growth Factor-β1 Regulates the Expression of the High-Affinity Receptor for IgE on CD34+ Stem Cell-Derived CD1a+ Dendritic Cells In Vitro

It has been reported that monocytes, Langerhans cells (LC) and other dendritic cells (DC) express the high-affinity receptor for IgE (FcepsilonRI) in patients with atopic diseases. These cells may be instrumental in the control of the immune response and the allergic inflammation. In this context, transforming growth factor beta 1 (TGF-beta1) has been highlighted as a key cytokine involved in the mechanisms aimed to orchestrate tolerance and has been suggested as a candidate gene in atopic diseases. In this report, we investigate the putative role of TGF-beta1 in the regulation of FcepsilonRI on cord blood CD34+ stem cell-derived CD1a+ DC (CD34-derived CD1a+ DC). Kinetic experiments show that FcepsilonRI spontaneously appears on the surface of CD1a+ DC, but decreases when exogenous TGF-beta1 is added at high doses (10 ng per mL) or when endogenous TGF-beta1 is neutralized in the culture conditions. In contrast, low-dose TGF-beta1 (0.5 ng per mL) stabilizes surface FcepsilonRI expression on DC. Increasing TGF-beta1 concentrations leads to the generation of LC-like DC showing an augmentation in stimulatory capacity towards allogeneic T cells. In view of these data, a picture emerges that FcepsilonRI+ on DC is finely modified by the TGF-beta1 concentration in the microenvironment and could be of primary relevance in the context of atopic diseases.

Why are dendritic cells important in allergic diseases of the respiratory tract?

Increasing evidence points to the role of antigen-presenting dendritic cells (DC) in regulating adaptive immune responses. DC are especially sensitive to signals derived from microbes, allergens, and the airway tissue microenvironment, can polarize naïve T-cells into either Th1 or Th2 effector cells, and are increasingly recognized as having a central role in the establishment of T-cell memory and tolerance to inhaled antigens. DC form a closely meshed network within the respiratory mucosa and are rapidly recruited from the circulation in response to a variety of proinflammatory stimuli. Studies using animal models have highlighted the role of DC in both initiation and maintenance of allergic airway inflammation. Increased numbers of airway mucosal DC are found in both allergic rhinitis and asthma, and an increasing number of investigators have highlighted important functional differences between DC from atopic and normal individuals. This article reviews recent information on the involvement of DC in the pathogenesis of allergic airway disease and the means by which DC could be exploited as targets for therapy in asthma and allergic rhinitis.

Vaccinia virus pathogenicity in atopic dermatitis is caused by allergen-induced immune response that prevents the antiviral cellular and humoral immunity

Atopic dermatitis (AD) serves as a contraindication for the immunization of AD patients with a live vaccinia virus (VV) vaccine. The antiallergen IgE interacts with the Fc receptors (FcepsilonRI) on dendritic cell (DC) membranes and with allergen molecules. The immunological events that lead to AD disease, the activation of the T-helper 2 (Th2) immune response, the synthesis of the cytokines IL-4, IL-5, IL-13, and the inhibition of the T-helper 1 (Th1) damage the capacity of the host to develop anti-VV cytotoxic cells (CTLs). In the presence of Th2-derived cytokine IL-4 in the AD skin and the synthesis of VV proteins that interfere recruitment of DCs by host cytokines, the VV can cause a generalized infection. Conceptually, new VV recombinants may be needed for human immunization. Such VV recombinants should lack the genes that interfere with the host immune system and express a mutated human IL-4 cytokine gene that will prevent negative regulatory mechanisms. Such improved VV recombinants may be used to express genes from pathogenic viruses.

The biology of IGE and the basis of allergic disease

Allergic individuals exposed to minute quantities of allergen experience an immediate response. Immediate hypersensitivity reflects the permanent sensitization of mucosal mast cells by allergen-specific IgE antibodies bound to their high-affinity receptors (FcepsilonRI). A combination of factors contributes to such long-lasting sensitization of the mast cells. They include the homing of mast cells to mucosal tissues, the local synthesis of IgE, the induction of FcepsilonRI expression on mast cells by IgE, the consequent downregulation of FcgammaR (through an insufficiency of the common gamma-chains), and the exceptionally slow dissociation of IgE from FcepsilonRI. To understand the mechanism of the immediate hypersensitivity phenomenon, we need explanations of why IgE antibodies are synthesized in preference to IgG in mucosal tissues and why the IgE is so tenaciously retained on mast cell-surface receptors. There is now compelling evidence that the microenvironment of mucosal tissues of allergic disease favors class switching to IgE; and the exceptionally high affinity of IgE for FcepsilonRI can now be interpreted in terms of the recently determined crystal structures of IgE-FcepsilonRI and IgG-FcgammaR complexes. The rate of local IgE synthesis can easily compensate for the rate of the antibody dissociation from its receptors on mucosal mast cells. Effective mechanisms ensure that allergic reactions are confined to mucosal tissues, thereby minimizing the risk of systemic anaphylaxis.

Airway dendritic cells: co-ordinators of immunological homeostasis and immunity in the respiratory tract

The large quantities and complex mixtures of antigens encountered daily at airway mucosal and alveolar surfaces pose a major challenge to maintenance of immunological homeostasis in the respiratory tract. Amongst this myriad of antigens, the immune system must discriminate between innocuous components that can be tolerated by the host and potentially life-threatening pathogens that require a rapid immune response. Dendritic cells (DC) represent the principal cell type at these sites capable of processing antigens and delivering signals that initiate tolerogenic or immunogenic immune responses. This review will discuss the role of DC at the "front-line" of immune surveillance and homeostasis within the respiratory tract and their role in the pathogenesis of respiratory disease.

The role of dendritic cells in immune regulation and allergic airway inflammation

Dendritic cells (DC) are potent antigen presenting cells that display an extraordinary capacity to present antigen to naïve T-cells and initiate primary immune responses. In the context of the lung and upper airway it is clear that DC play a key role in the regulation of adaptive immune responses to inhaled antigen. DC are particularly sensitive to signals derived from microbes, allergens and the airway tissue microenvironment. By the nature of the signals they provide at the time of antigen presentation, DC can polarize naïve T-cells into either T-helper type 1 (Th1) or Th2 effector cells, and are increasingly recognized as having a central role in the establishment of T-cell memory and peripheral immune tolerance. DC form a network within the upper airway and lung, and are rapidly recruited from the circulation in response to a variety of proinflammatory stimuli. Studies using animal models have highlighted the role of DC in both the initiation and maintenance of allergic airway inflammation. In early childhood, human DC are functionally immature, and this is thought to contribute to the development of allergic sensitization in those children who are genetically at risk for the development of atopy. Increased numbers of airway mucosal DC are found in both allergic rhinitis and asthma, while studies of blood-derived DC have emphasized important differences between the function of DC from atopic and normal individuals. This article reviews recent information on the involvement of DC in allergic airway disease, and the mechanisms by which DC could be exploited as targets for therapy in asthma and allergic rhinitis.

Evidence for a differential expression of the FcepsilonRIgamma chain in dendritic cells of atopic and nonatopic donors

While mast cells and basophils constitutively express the high-affinity IgE receptor (Fc epsilon RI), it is absent or weakly expressed on APCs from normal donors. Fc epsilon RI is strongly upregulated on APCs from atopic donors and involved in the pathophysiology of atopic diseases. Despite its clinical relevance, data about Fc epsilon RI regulation on APCs are scarce. We show that in all donors intracellular alpha chain of the Fc epsilon RI (Fc epsilon RI alpha) accumulates during DC differentiation from monocytes. However, expression of gamma chains of the Fc epsilon RI (Fc epsilon RI gamma), mandatory for surface expression, is downregulated. It is low or negative in DCs from normal donors lacking surface Fc epsilon RI (Fc epsilon RI(neg) DCs). In contrast, DCs from atopics express surface Fc epsilon RI (Fc epsilon RI(pos) DCs) and show significant Fc epsilon RI gamma expression, which can be coprecipitated with Fc epsilon RI alpha. In Fc epsilon RI(neg) DCs lacking Fc epsilon RI gamma, immature and core glycosylated Fc epsilon RI alpha accumulates in the endoplasmic reticulum. In Fc epsilon RI(pos) DCs expressing Fc epsilon RI gamma, an additional mature form of Fc epsilon RI alpha exhibiting complex glycosylation colocalizes with Fc epsilon RI gamma in the Golgi compartment. IgE binding sustains surface-expressed Fc epsilon RI on DCs from atopic donors dependent on baseline protein synthesis and transport and enhances their IgE-dependent APC function. We propose that enhanced Fc epsilon RI on DCs from atopic donors is driven by enhanced expression of otherwise limiting amounts of Fc epsilon RI gamma and is preserved by increased IgE levels.

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

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

Smallpox vaccination: Risk considerations for patients with atopic dermatitis

As the threat of bioterrorism with pathogenic microbes such as smallpox virus (Variola major) increases, the question of widespread voluntary vaccination with smallpox (vaccinia) vaccines is being carefully considered. A major challenge lies in the ability to protect the population from the disease while minimizing the considerable side effects from the vaccine. Individuals with active or quiescent atopic dermatitis are at increased risk for vaccinia complications. The nature of these complications and other considerations are summarized in this rostrum.

The nucleotide sequence of dinitrophenyl-specific IgE and Fc(epsilon)RI alpha-subunit obtained from FE-3 hybridoma cells

FE-3 cells were established by Hanashiro et al. by hybridizing mouse myeloma cells (Sp2/0-Ag14/SF) with rat spleen cells that were freshly isolated from Brown-Norway rats sensitized with DNP-As. FE-3 cells can constitutively secrete IgE without stimulation by cytokines. Our preliminary experiments demonstrated that the IgE secretion was decreased at 3 days after start of culture and the addition of exogenous IgE into culture media depressed the secretion of IgE. Thus, we hypothesized that the IgE production in FE-3 cells may be regulated by a signal transduction through the binding of IgE to its high affinity receptor (Fc(epsilon)RI) or to an IgE binding protein on the cell surface. In this study, we aimed to identify the nucleotide sequence of IgE FE-3 and compared with those of mouse IgE and IgE IR162 to find a structural heterogeneity in the Fc region of IgE FE-3. We also tested if the mRNA of Fc(epsilon)RI was expressed in FE-3 cells using the reverse transcriptase-polymerase chain reaction (RT-PCR) method with the combination of sequencing analysis. Consequently, the cDNA sequence of IgE FE-3 was identical to that of the CH3 and CH4 domains in the epsilon-chain of rat IgE IR162, whereas the cDNA of Fc(epsilon)RI was identical to that of mouse, suggesting that the genes of IgE FE-3 and Fc(epsilon)RI was derived from that of rat spleen cells and mouse myeloma cells, respectively.

Pathophysiologic mechanisms in atopic dermatitis

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

Nedocromil sodium and levocabastine reduce the symptoms of conjunctival allergen challenge by different mechanisms

BACKGROUND

Nedocromil sodium and levocabastine are widely used for the treatment of ocular allergy, but their mechanisms of action are unclear.

OBJECTIVE

We sought to compare the efficacy and mechanisms of action of nedocromil sodium and levocabastine in reducing conjunctival symptoms after ocular allergen challenge.

METHODS

We performed a double-blind, placebo-controlled study in which 48 subjects were randomized to 3 groups to receive nedocromil sodium (2%), levocabastine (0.05%), or placebo eye drops twice daily for 2 weeks before ocular challenge with 10 microL of ryegrass extract. Symptoms and tear histamine and PGD(2) concentrations were determined before challenge and at 10, 20, 30, 60, 180, and 360 minutes after challenge. Bulbar biopsy specimens were taken at 6 and 24 hours after challenge to assess conjunctival inflammatory cell numbers, adhesion molecule expression, and mast cell-associated IL-4, IL-5, IL-6, IL-13, and TNF-alpha levels.

RESULTS

Both drugs significantly reduced total symptom scores (P <.05) at all times after challenge compared with placebo. Itching, hyperemia, and lacrimation were most affected. Nedocromil sodium treatment reduced tear concentrations of histamine (by 77%) and PGD(2) (by 70%) at 30 minutes after challenge (both P <.05). In biopsy specimens nedocromil sodium reduced the number of 3H4-positive mast cells (purportedly the secreted form of IL-4) by 49% at 6 hours and 59% at 24 hours (both P <.05). Levocabastine reduced intercellular adhesion molecule 1 expression by 52% at 6 hours and 45% at 24 hours (both P <.05).

CONCLUSION

Nedocromil sodium and levocabastine both reduced the conjunctival symptoms after ocular allergen challenge but appeared to work by different mechanisms. Nedocromil sodium reduced mast cell function, whereas levocabastine appeared to have primarily antihistaminic actions, although it also reduced the expression of intercellular adhesion molecule 1.

Allergen sensitization through the skin induces systemic allergic responses

The skin is a unique immunologic organ that acts as an interface between the external environment and the systemic immune response. As such, it may react directly with allergens that are applied epicutaneously, thereby influencing the systemic allergic response. It is well known that atopic dermatitis (frequently in association with food allergy) predates the development of asthma and allergic rhinitis by several years. The possibility that atopic dermatitis may influence the course of asthma is suggested by several interesting observations. First, children with atopic dermatitis and positive skin tests to allergens frequently have more severe asthma than asthmatic children without atopic dermatitis. Second, because total serum IgE is strongly associated with the prevalence of asthma, it raises the interesting question of whether allergen sensitization through the skin predisposes to more severe and persistent respiratory disease because of its effects on the systemic allergic response. Indeed, epicutaneous sensitization of mice to a protein antigen induces both a localized allergic dermatitis and hyperresponsiveness to methacholine, which suggests that epicutaneous exposure to antigen in atopic dermatitis may enhance the development of asthma. Finally, systemic immune activation in atopic dermatitis is supported by the observation that these patients have increased numbers of circulating activated T(H)2 cells, eosinophils, macrophages, and IgE. Many of the markers of leukocyte activation have been shown to correlate with the severity of atopic dermatitis disease. This systemic activation might facilitate local infiltration of primed T cells, eosinophils, and macrophages into the respiratory mucosa after inhalation of allergen in genetically predisposed hosts. The systemic aspects of atopic dermatitis, with an emphasis on respiratory effects, are summarized.

Atopic dermatitis: new insights and opportunities for therapeutic intervention

Atopic dermatitis (AD) is a chronic inflammatory skin disease that frequently predates the development of allergic rhinitis or asthma. It is an important skin condition with significant costs and morbidity to patients and their families; the disease affects more than 10% of children. Recent studies have demonstrated the complex interrelationship of genetic, environmental, skin barrier, pharmacologic, psychologic, and immunologic factors that contribute to the development and severity of AD. The current review will examine the cellular and molecular mechanisms that contribute to AD as well as the immunologic triggers involved in its pathogenesis. These insights provide new opportunities for therapeutic intervention in this common skin condition.