High affinity IgE receptor (Fc epsilon RI) expression on eosinophils infiltrating the lesions and mite patch tested sites in atopic dermatitis

Effects of Omalizumab on FcεRI and IgE Expression in Lesional Skin of Bullous Pemphigoid

Recent studies suggest an important role of immunoglobulin E (IgE) as an alternative pathogenic pathway in the development of bullous pemphigoid (BP), as the most frequent subepidermal blistering disease of the skin Use of IgE targeted therapies, such as omalizumab, has been shown promising in recent studies. The aim of this study was to assess the effect of omalizumab on FcεRI and IgE expression on circulating basophils and on lesional intradermal cells in BP to generate insight into the immunological effects of omalizumab in BP. We report two cases of BP patients treated with omalizumab. Efficacy of treatment was assessed clinically 4 months after initiation of the therapy. Lesional and non-lesional skin biopsies where taken before and 4 weeks after initiation of omalizumab therapy. In addition, FcεRI expression on circulating cells and IgE levels in serum and in the skin samples, as well as anti-BP180 and anti-BP230 in serum and eosinophils and basophils counts in blood were assessed before and during treatment. Both patients showed a marked improvement after 4 months, with no adverse effects. Down-regulation of FcεRI, IgE in lesional skin and on circulating basophils were observed in parallel with clinical improvement. The current case study supports the role of omalizumab in the treatment of a subset of BP patients. Our observations suggest that omalizumab represents a valuable therapeutic option in the management of BP patients. Its efficacy might be related to reduction in FcεRI+ and IgE+ basophils and intradermal cells.

Peripheral eosinophilia in bullous pemphigoid: prevalence and influence on the clinical manifestation

BACKGROUND

Peripheral eosinophilia has been reported in 50-60% of patients with bullous pemphigoid (BP) and correlated positively with disease severity.

OBJECTIVES

To establish an association of peripheral eosinophilia with the different morphological characteristics of BP.

METHODS

The study was designed as a case-control study. Diagnosis of BP was grounded on well-established immunopathological criteria. Five age-, sex- and ethnicity-matched controls were randomly selected for each patient with BP.

RESULTS

Overall, 225 patients with BP and 1125 control participants were enrolled. A total of 113 (50·2%) patients with BP and 49 (4·4%) controls had pathological peripheral eosinophilia (P < 0·001). An independent association between eosinophil count and the diagnosis of BP was observed [odds ratio 59·9 (per 1000 eosinophil μL^-1 increase); P < 0·001]. Patients with BP with eosinophilia were significantly older at presentation (P = 0·003) and had increased palmoplantar involvement (P = 0·005), whereas patients with normal eosinophil counts had greater involvement of mucosal surfaces (P = 0·002) and the head and neck (P = 0·047). Patients with BP with extensive disease had significantly higher eosinophil counts than patients with mild-to-moderate disease (996·5 ± 1052·5 vs. 696·1 ± 962·6 cells μL^-1 ; P < 0·001).

CONCLUSIONS

Patients with BP with serum eosinophilia were significantly older and had higher palmoplantar involvement. Patients with BP with a normal eosinophil count were younger and presented more frequently with atypical clinical manifestations.

Eosinophils Mediate Tissue Injury in the Autoimmune Skin Disease Bullous Pemphigoid

Eosinophils are typically associated with unique inflammatory settings, including allergic inflammation and helminth infections. However, new information suggests that eosinophils contribute more broadly to inflammatory responses and participate in local immune regulation and the tissue remodeling/repair events linked with a variety of diseases. Eosinophilic infiltration has long been a histologic hallmark of bullous pemphigoid (BP), a subepidermal autoimmune blistering disease characterized by autoantibodies directed against basement membrane protein BP180. However, the exact role of eosinophils in disease pathogenesis remains largely unknown. We show here that eosinophils are necessary for IgE autoantibody-mediated BP blister formation in a humanized IgE receptor mouse model of BP. Disease severity is IgE dose dependent and correlates with the degree of eosinophil infiltration in the skin. Furthermore, IgE autoantibodies fail to induce BP in eosinophil-deficient mice, confirming that eosinophils are required for IgE-mediated tissue injury. Thus, eosinophils provide the cellular link between IgE autoantibodies and skin blistering in this murine model of BP. These findings suggest a role for eosinophils in autoimmune disease and have important implications for the treatment of BP and other antibody-mediated inflammatory and autoimmune diseases.

Functional and phenotypic analysis of basophils allows determining distinct subtypes in patients with chronic urticaria

BACKGROUND

Chronic urticaria (CU) is a frequent skin disease characterized by relapsing appearance of pruritic hives. While clinical symptoms are due to the release of histamine by cutaneous mast cells, the underlying pathophysiology is still unknown. However, previous studies indicate that basophils might be of relevance. Besides, the occurrence of autoantibodies against IgE or its receptor, FcεRI, and the therapeutic efficacy of anti-IgE antibodies imply that IgE-mediated mechanisms also play an important role in CU.

METHODS

Reactivity of CU patients' peripheral blood basophils (n=60) to specific anti-FcεRI and IgE-independent fMLP stimulation was determined by basophil activation test in comparison with patients suffering from IgE-mediated allergic rhinitis (n=10) and healthy controls (n=10). In addition, immunoglobulin receptor (FcεRI, FcγRII) expression and surface bound antibodies (IgE, IgG) were quantified on basophils. Furthermore, the autoreactive capacity of CU sera was evaluated and urticaria-related symptoms were assessed by both UCT and CU-Q₂ oL.

RESULTS

Stimulating CU patients' basophils via FcεRI, we identified three distinct immunologic phenotypes. One subgroup of patients' basophils reacted to FcεRI stimulation, whereas the others had anti-FcεRI nonreactive basophils. Among the latter, a subgroup with pronounced basopenia was identified. Of note, this group was characterized by augmented serum-induced basophil activation, increased levels of autoantibodies against thyroid peroxidase, and also exhibited the strongest disease impact on their quality of life.

CONCLUSIONS

Patients with CU can be categorized into three immunologic subgroups based on their basophil reactivity and frequency. These phenotypes are associated with different clinical characteristics, pointing to basophils as important players in CU pathophysiology.

IgE-mediated mechanisms in bullous pemphigoid and other autoimmune bullous diseases

Autoimmune bullous diseases (AIBDs) are characterized by autoantibodies against structural proteins of the dermal-epidermal junction (in pemphigoid diseases) and the epidermal/ epithelial desmosomes (in pemphigus diseases). By far, the most common AIBD is bullous pemphigoid, which is immunopathologically characterized by autoantibodies against BP180 (type XVII collagen) and BP230. IgG and, to a lesser extent, IgA autoantibodies are the major autoantibody isotypes in these disorders. IgE autoantibodies are increasingly reported in particular in bullous pemphigoid. The development of specific and sensitive anti-BP180 IgE ELISA systems, the report of two experimental murine models employing IgE autoantibodies against BP180, and the successful treatment of bullous pemphigoid with the anti-IgE antibody omalizumab have raised interest in the role of IgE autoantibodies and the modulation of their production in AIBDs. Here, the relevance of IgE autoantibodies in the diagnosis, pathophysiology, and treatment decisions of AIBDs, with a focus on bullous pemphigoid, is reviewed.

Fc Receptors in Immune Responses

Antibodies are major molecular effectors of adaptive immune responses. Most, if not all, biological activities of antibodies, however, depend on the functional properties of cells that express receptors for the Fc portion of antibodies (FcR). Most FcR are activating receptors; some are inhibitory. When engaged by antibodies and antigen, the various FcR expressed by a given cell trigger a mixture of positive and negative signals whose integration determines cellular responses. Responses of cell populations can be either protective or pathogenic. As a consequence, FcR are potential target/tools in a variety of diseases including infection, allergy, autoimmune diseases, and cancer.

Fc receptors as adaptive immunoreceptors

Most biological activities of antibodies depend on their ability to engage Receptors for the Fc portion of immunoglobulins (FcRs) on a variety of cell types. As FcRs can trigger positive and negative signals, as these signals control several biological activities in individual cells, as FcRs are expressed by many cells of hematopoietic origin, mostly of the myeloid lineage, as these cells express various combinations of FcRs, and as FcR-expressing cells have different functional repertoires, antibodies can exert a wide spectrum of biological activities. Like B and T Cell Receptors (BCRs and TCRs), FcRs are bona fide immunoreceptors. Unlike BCRs and TCRs, however, FcRs are immunoreceptors with an adaptive specificity for antigen, with an adaptive affinity for antibodies, with an adaptive structure and with an adaptive signaling. They induce adaptive biological responses that depend on their tissue distribution and on FcR-expressing cells that are selected locally by antibodies. They critically determine health and disease. They are thus exquisitely adaptive therapeutic tools.

Abundant immunoglobulin E-positive cells in skin lesions support an allergic etiology of atopic dermatitis in the elderly

Background/Objectives

Atopic dermatitis (AD) in the elderly is gradually increasing in industrialized countries in association with the aging of society. We report herein four cases of elderly AD {three extrinsic [immunoglobulin (Ig)E-mediated allergy]; one intrinsic (non-IgE-allergy)} in which we investigated the presence of IgE+ cells in lesional skin.

Methods/Results

Single immunohistochemical and double immunofluorescence stainings were performed for skin biopsy specimens from AD patients and non-atopic control subjects with chronic eczema. In the lesional lichenified skin of patients with extrinsic elderly AD, numerous IgE+ cells were found among inflammatory cells infiltrates in the upper dermis. Comparative analysis of single immunohistochemistry results using serial paraffin and/or frozen sections found that many IgE+ cells showed identical distributions to tryptase+ mast cells. IgE+ cells coincident with CD1a+ Langerhans cells in the epidermis were found in small numbers only in frozen sections. Double immunofluorescence staining for IgE and CD11c revealed cells coexpressing IgE and CD11c with a dendritic morphology in the papillary and upper dermis. These IgE+ mast cells and IgE+ CD11c+ cells were also found in cured normal-looking skin from a patient with extrinsic elderly AD after successful treatment. Although only a few weakly positive IgE+ cells were detected, no IgE+CD11c+ cells were found in specimens from patients with intrinsic elderly AD or non-atopic chronic eczema.

Conclusion

IgE-mediated allergic inflammation may play an important role in the pathobiology of elderly AD, similar to other age groups of AD.

Comparative analysis of FcεRI expression patterns in patients with eosinophilic and reflux esophagitis

BACKGROUND AND OBJECTIVE

Eosinophilic esophagitis (EoE) is an allergic disease of the esophagus. The IgE receptors on immune cells that infiltrate the esophagus are poorly defined. The high-affinity receptor for IgE, FcεRI, may play a role in EoE. The objective of the present study is to identify and compare the IgE receptors in the esophageal epithelium of patients with EoE, reflux esophagitis (RE), and normal controls.

PATIENTS AND METHODS

A retrospective case-control study of 62 patients (19 EoE, 22 RE, 21 normal controls) was conducted. Biopsies were immunostained for FcεRI, CD23, galectin-3, c-kit, CD1a, and langerin.

RESULTS

FcεRI was the only IgE receptor present in the esophageal epithelium of patients with EoE. The FcεRI-positive cell count varied by diagnosis (proximal biopsies EoE 32.6 ± 19.0 cells/high-power field, RE 26.7 ± 16.6, controls 15.6 ± 8.3, ANOVA P = 0.005; distal biopsies EoE 24.2 ± 16.2, RE 35.7 ± 27.6, controls 15.3 ± 8.4, P = 0.006). In the proximal esophagus, the FcεRI count was higher in EoE than in controls (P = 0.006); in the distal esophagus, the FcεRI count was higher in RE than in controls (P = 0.004). EoE and RE had similar FcεRI-positive cell counts. A subset of FcεRI-positive cells was similar in morphology and distribution to Langerhans cells (CD1a and langerin positive).

CONCLUSIONS

The presence of FcεRI-positive cells in high numbers in the esophageal epithelium implies this receptor must be critical in the IgE-mediated activation of immune cells in the esophagus. Langerhans cells in the esophageal epithelium appear to express FcεRI. The role of Langerhans cells in the pathophysiology of EoE needs to be elucidated.

IgA is a more potent inducer of NADPH oxidase activation and degranulation in blood eosinophils than IgE

Human eosinophils can mediate both beneficial and detrimental responses in parasitic and allergic diseases. Binding of aggregated immunoglobulin to Fc receptors on eosinophils mediates important defence processes, including generation of activated oxygen species resulting from NADPH oxidase activation, and eosinophil peroxidase release following degranulation. The abilities of a matched set of IgA, IgG and IgE antibodies to elicit such responses in blood-derived eosinophils were compared using a chemiluminescence assay. IgA and IgG, but not IgE, were found to trigger NADPH oxidase activation and degranulation in eosinophils. This non-responsiveness to IgE did not result from receptor blockade by endogenous IgE since no blood-derived IgE was detectable on freshly isolated eosinophils. Moreover, while cross-linking of FcalphaRI by specific mAbs triggered NADPH oxidase activation and degranulation in blood-derived eosinophils, equivalent cross-linking of FcvarepsilonRI or FcvarepsilonRII did not elicit such responses. Therefore IgA is more potent at eliciting activated oxygen species release and degranulation in eosinophils than IgE, suggesting that the importance of IgA in eosinophil activation in immune defence and allergy may have been underestimated.

Comparison of an enzyme linked immunosorbent assay (ELISA) and a radioallergosorbent test (RAST) for detection of IgE antibodies to Brugia malayi

The enzyme linked immunosorbent assay (ELISA) for specific IgE antibodies to Brugia malayi was compared with the radioallergosorbent test (RAST) for use in immunoepidemiological studies of lymphatic filariasis. Sera used were from individuals (aged 5-82 years) living in an area endemic for lymphatic filariasis in South Sulawesi, Indonesia. The percentage of positive IgE ELISA reactions (52.6%) among the population was lower than the percentage of positive RAST (94.5%). Although an overall significant concordance was found between the two assays (P < 0.001), 328 (42.7%) individuals with a positive RAST result were negative in the ELISA, whereas only 6 (0.8%) subjects were positive by ELISA, yet negative by RAST. When the population was divided into those with active infection (positive for anti-filarial IgG4) and those not infected (mf-negative and negative for anti-filarial IgG4), the correlation between the two tests was higher in the IgG4-positive (rho = 0.70) than in the IgG4-negative (rho = 0.52) group. These results indicate that in assessment of B. malayi specific IgE antibody, RAST is superior to ELISA. However, given the use of radioactivity in the RAST method and given our results obtained in subjects with high anti-filarial IgG4, one could consider using the IgE-ELISA in areas with high endemicity for filariasis. In areas with low endemicity or where control programs are implemented, sera will have to be tested by RAST.

The clinical spectrum of atopic dermatitis

Updating our clinical concept of atopic dermatitis (AD) evolves from the better understanding of all the immunologic aberrations expressed by the polygenic combinations and permutations associated with the atopic diathesis. Recognizing the immunopathologic features of AD readily underscores that AD without "atopy" is an oxymoron. Appreciating "pruritus" as the impetus to scratch, which isomorphically gives rise to the "eczema," shifts the goal of management from suppressing inflammation to avoiding the triggers of pruritus. Recognizing the full spectrum of dermatologic findings in AD endorses the preferred label as a dermatitis, rather than the inferred restrictive label, atopic eczema. As our knowledge of immunology evolves, our criteria for the diagnosis and management of the atopic diathesis are sure to change.

The high-affinity IgE receptor (Fc epsilon RI): from physiology to pathology

The high affinity receptor for immunoglobulin E (designated Fc epsilon RI) is the member of the antigen (Ag) receptor superfamily responsible for linking pathogen-or allergen-specific IgEs with cellular immunologic effector functions. This review provides background information on Fc epsilon RI function combined with more detailed summaries of recent progress in understanding specific aspects of Fc epsilon RI biology and biochemistry. Topics covered include the coordination and function of the large multiprotein signaling complexes that are assembled when Fc epsilon RI and other Ag receptors are engaged, new information on human receptor structures and tissue distribution, and the role of the FcR beta chain in signaling and its potential contribution to atopic phenotypes.

Human eosinophil-lymphocyte interactions

While the eosinophil's effector functions clearly can contribute to the pathogenesis of allergic diseases, the evolutionary benefit to having eosinophils as a distinct class of leukocyte is not clear, especially if one must reconsider the nominally beneficial role of eosinophils in parasite host defense, Eosinophils are equipped to respond to lymphocytes and their cytokines (and not solely the eosinophil growth factor cytokines), but the functional consequences of such eosinophil responses need to be defined. Conversely, eosinophils, as antigen-presenting cells (APCs) or sources of lymphocyte-active cytokines, may stimulate and affect lymphocyte functioning. Eosinophils share with CD4+ lymphocytes expression of a number of receptors, including CD4 and IL-2R, and specific alpha-4 integrins that may help in their common recruitment and activation. Further, elucidation of the interactions between lymphocytes and eosinophils will contribute to a broader understanding of the functioning of eosinophils in "normal" ongoing immune responses and in allergic disorders.

Increased expression of high affinity IgE (FcepsilonRI) receptor-alpha chain mRNA and protein-bearing eosinophils in human allergen-induced atopic asthma

FcepsilonRI receptors play an important role in allergen-induced mediator release and antigen presentation by mast cells, basophils, and monocyte/macrophages in atopic disorders. The expression of FcepsilonRI by tissue eosinophils in atopic asthma after allergen challenge has not been established. For this reason we attempted to identify mRNA and protein product + FcepsilonRIalpha eosinophils in cytospins made from bronchoalveolar lavage (BAL) from atopic asthmatics (n = 9) and nonatopic normal subjects (n = 4) 24 h after segmental challenge with allergen or diluent. Messenger RNA for FcepsilonRIalpha was determined using in situ hybridization and FcepsilonRIalpha protein expression by immunocytochemistry using a mouse monoclonal antibody 22E7. Colocalization of FcepsilonRIalpha receptors to eosinophils was performed using chromotrope 2R. When compared with a control challenge, segmental challenge with Dermatophagoides pteronyssinus induced significant BAL eosinophilia (p = 0.007). The total number of BAL FcepsilonRIalpha mRNA and protein-positive cells also increased in asthmatics, median values 2 (0.7-7.2) and 11.5 (0.6-65.0) x 10(6) cells (p = 0.02) and 0 (0-0.3 x 10(6)) and 3.1 x 10(6) (0.45 - 162.5 x 10(6)) cells (p = 0.007), respectively, for mRNA and protein. Net increases in FcepsilonRIalpha+ cells correlated with the net increases in BAL eosinophils (r = 0.98, p = 0.0001 for mRNA and r = 0.72, p = 0.02 for protein). Colocalization studies with chromotrope 2R revealed that only 4% of FcepsilonRIalpha+ cells were eosinophils after control challenge and, in contrast, 85 to 95% of FcepsilonRIalpha+ cells were eosinophils after allergen. There were no differences in the numbers of FcepsilonRIalpha+ cells or eosinophils in normal control subjects. Our results demonstrated that local endobronchial allergen provocation in atopic asthmatics results in increased synthesis and expression of FcepsilonRIalpha predominantly on BAL eosinophils.

High-affinity immunoglobulin E receptor (Fc epsilon RI)-bearing eosinophils, mast cells, macrophages and Langerhans' cells in allergen-induced late-phase cutaneous reactions in atopic subjects

We have used in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate the kinetics of the expression for Fc epsilon RI mRNA (alpha-, beta- and gamma-chains), the alpha-chain protein product, as well as the phenotype of the mRNA- or protein-positive cells in allergen-induced late-phase skin reactions in atopic subjects. Compared with diluent controls, there were significant increases in the total number of mRNA+ cells for the alpha-, beta- and gamma-chains for Fc epsilon RI at all time-points (6, 24 and 48 hr) after allergen challenge (P < 0.01). By double IHC/ISH significant increases in alpha-, beta- and gamma-chain mRNA+ macrophages, eosinophils, mast cells and CD1a+ cells were also observed after allergen challenge (P < 0.05). The distribution of Fc epsilon RI subunit (alpha-, beta-, or gamma-chain) mRNA+ co-localization was CD68+ macrophages (42-47%), EG2+ eosinophils (33-39%), tryptase+ mast cells (5-11%) and CD1a+ Langerhans' cells (2-4%). Using single IHC, significant increases in the total number of Fc epsilon RI protein+ cells (P < 0.01) were observed 24 and 48 hr after allergen challenge. Double IHC showed that the distribution of Fc epsilon RI+ cells was tryptase+ mast cells (33%), CD68+ macrophages (36%), EG2+ eosinophils (20%), CD1a+ Langerhans' cells (4%) and unidentified cells (7%), at the 24-hr allergen-challenged sites. These observations suggest that the cutaneous late-phase reaction in man is associated with up-regulation of Fc epsilon RI on eosinophils, macrophages, mast cells and Langerhans' cells.

Allergen-induced recruitment of Fc epsilon RI+ eosinophils in human atopic skin

We have attempted to identify Fc epsilon RI+ eosinophils in cutaneous late-phase reaction in atopic subjects biopsied at 6, 24 and 48 h after the injection of either allergen or a diluent control. Compared to the diluent sites, allergen-injected sites had significantly increased numbers of eosinophils, peaking between 6 and 24 h, of which approximately 20-30% expressed mRNA for the alpha, beta, and gamma chains of Fc epsilon RI, as shown by in situ hybridization. Using either a monoclonal or a polyclonal anti-alpha chain antibody, the Fc epsilon RI alpha protein also co-localized to approximately 50-80% of eosinophils at all time points studied. We also observed a significant correlation (r = 0.89; p = 0.02) between the numbers of Fc epsilon RI+ (997+)/EG2+ eosinophils and the magnitude of the late-phase reaction. Thus, a significant proportion of eosinophils infiltrating the site of allergen-induced allergic tissue reactions in atopic subjects express Fc epsilon. RI. The findings show that high-affinity IgE receptors may play a role in eosinophil secretory processes in vivo.

The high-affinity receptor for IgE is the predominant IgE-binding structure in lesional skin of atopic dermatitis patients

While the skin of most patients with atopic dermatitis (AD) is known to contain IgE-bearing cells, the contribution of the various IgE-binding structures to this phenomenon is not fully understood. To address this issue, we eluted cell-bound IgE from cryostat sections of lesional AD skin by acid treatment and performed reconstitution experiments with IgE in the absence or presence of reagents directed against the currently known IgE-binding structures. We found that incubation of acid-treated sections, with either chimeric or serum IgE, resulted in the appearance of sizable numbers of anti-IgE-reactive cells. This cellular IgE loading could be entirely prevented by preincubation of the sections with the anti-Fc epsilonRI alpha MoAb 15-1 but not with either antibodies against Fc epsilonRII/CD23 and Fc gammaRII/CD32 or with alpha-lactose. To exclude the possibility that acid treatment of tissue sections may have adversely influenced the IgE-binding capacity of IgE receptors other than Fc epsilonRI, we performed an identical series of experiments on AD skin samples that, as an exception, were essentially devoid of anti-IgE-reactive cells. Again, no IgE loading was detected when these sections were preincubated with anti-Fc epsilonRI alpha MoAbs. In contrast, preincubation of the sections with alpha-lactose and/or MoAbs against Fc epsilonRII/CD23 or Fc gammaRII/CD32 did not affect IgE loading. Together with the observations that anti-Fc epsilonRI alpha-reactive and IgE-binding cells are largely overlapping populations and include cells of the Langerhans cell/dendritic cell lineage, mast cells, and a few dermal dendrocytes and eosinophils, our results demonstrate that Fc epsilonRI is the predominant and, perhaps, the only biologically relevant IgE-binding structure on histogenetically and functionally diverse cell populations of AD skin.

Immunoglobulins and their receptors on epidermal Langerhans cells in atopic dermatitis

To elucidate the etiological role of immunoglobulin molecules on Langerhans cells (LCs) in atopic dermatitis, we conducted immuno-histochemical studies on the localization of immunoglobulin G1 (IgG1), IgG2, IgG3, IgG4, IgA and IgM on epidermal LCs from 30 patients with atopic dermatitis (AD) and five non-atopic healthy volunteers. We also investigated the types of receptors for the immunoglobulins (Fc epsilon RI, Fc epsilon RII, Fc gamma RI, Fc gamma RII, and Fc gamma RIII) on epidermal LCs in the patients. IgE positive epidermal LCs were observed in 28 of 30 AD patients, and 46.7% of the epidermal LCs were positive for IgE. Both IgG1- and IgG2-positive epidermal LCs were observed in 70% of AD patients, and 21.8% and 28.7% of the total epidermal LCs were positive for IgG1 and IgG2, respectively. IgG3- or IgG4-positive LCs were present in only small proportions of AD patients. IgA-positive LCs were observed in 8 AD patients; our study suggested that the IgA bound on LCs was secretory IgA (S-IgA). These surface immunoglobulins were observed significantly more frequently on epidermal LCs in the involved skin of AD than in clinically uninvolved skin. No IgM-positive epidermal LCs were observed in the AD patients or healthy volunteers. In non-atopic healthy controls, no immunoglobulin-binding LCs were observed. In receptors for immunoglobulins, Fc epsilon RI and Fc gamma RII were exclusively expressed on nearly all epidermal LCs from all AD patients and all non-atopic controls. These results suggested that not only IgE but also IgG and IgA may play some etiological role in the pathogenesis of AD.