Norito Ishii

Epidermolysis bullosa acquisita sera react with distinct epitopes on the NC1 and NC2 domains of type VII collagen: study using immunoblotting of domain-specific recombinant proteins and postembedding immunoelectron microscopy

Background  The sera of epidermolysis bullosa acquisita (EBA) react with type VII collagen, a major component of anchoring fibrils, in which the major epitopes have been considered to be present in the N‐terminal noncollagenous (NC) 1 domain.

Epidermolysis bullosa acquisita: What's new?

Type VII collagen is an adhesion molecule of the extracellular matrix in epithelial basement membranes, and the main constituent of anchoring fibrils at the dermal–epidermal junction (DEJ). Autoimmunity against this protein is causing the rare organ‐specific epidermolysis bullosa acquisita (EBA). EBA is a rare acquired, heterogeneous, chronic blistering disease of skin disease of skin and mucous membranes characterized by subepidermal blisters and tissue‐bound as well as circulating autoantibodies to the DEJ. EBA has several distinct clinical presentations with other subepidermal bullous diseases, such as mainly dystrophic epidermolysis bullosa or bullous pemphigoid. The circulating immunoglobulin G autoantibodies for EBA react with a 290‐kDa dermal protein, type VII collagen, as detected by immunoblot analysis using dermal extracts. The pathogenicity of these autoantibodies has been demonstrated by experimental animal models, in which anti‐type VII collagen antibodies injected into a mouse produced an EBA‐like blistering disease in the animal. EBA cases often require high doses of systemic corticosteroids and a variety of immunosuppressants. Although treatment for EBA is frequently difficult and unsatisfactory, some therapeutic success has been reported with colchicine, dapsone, infliximab and i.v. immunoglobulin. In this review, we will focus on recent progress in our understanding of the clinical manifestations, the etiopathogenesis as well as the management of EBA.

Development of NC1 and NC2 domains of Type VII collagen ELISA for the diagnosis and analysis of the time course of epidermolysis bullosa acquisita patients

BACKGROUND Epidermolysis bullosa acquisita (EBA) is an acquired autoimmune mechanobullous disease. EBA patients possess autoantibodies against type VII collagen which is composed of a collagenous domain flanked by non-collagenous NC1 and NC2 domains. It was reported that major epitopes reside within the NC1 domain and minor epitopes reside within NC2 domain. OBJECTIVE The aim of this study is to develop a sensitive and specific ELISA to facilitate the diagnosis of EBA. METHODS We developed ELISAs using recombinant NC1 domain produced by mammalian expression system and recombinant NC2 domain produced by mammalian or bacterial expression system to characterize autoantibodies in EBA. Next, we developed an ELISA using a combination of the NC1 (mammalian expression) and NC2 (bacterial expression). We tested the ELISAs with 49 EBA sera, 55 normal control sera, 20 pemphigus vulgaris and 20 bullous pemphigoid sera. RESULTS When we evaluated the 49 EBA sera using the NC1 and NC2 ELISAs, 38 (77.5%) reacted with NC1 domain only, 7 sera (14.2%) reacted with both NC1 and NC2 domains, and one serum (2%) reacted with NC2 domain only. Therefore, to increase the sensitivity of the assay, we developed an ELISA coated with a mixture of recombinant NC1 and NC2 domains, resulting in 93.8% sensitivity and 98.1% specificity. By analyzing the time course of two EBA patients, ELISA scores fluctuated in parallel with their disease activity. CONCLUSION We conclude that the NC1+NC2 ELISA can be a practical assay for the diagnosis and follow up of the antibody titers of EBA patients.

From anti-p200 pemphigoid to anti-laminin γ1 pemphigoid

Anti‐laminin γ1 pemphigoid is an autoimmune subepidermal bullous disease first described in 1996, and has been distinct from previously known subepidermal blistering diseases, such as bullous pemphigoid and epidermolysis bullosa acquisita. Circulating autoantibodies of the patients do not react to any known autoantigen of the skin, but react to a 200‐kDa molecule (p200) from dermal extracts. The identity of p200 was unmasked as laminin γ1, an extracellular matrix glycoprotein composing several forms of laminin heterotrimers. We renamed this disease from the previously used anti‐p200 pemphigoid to anti‐laminin γ1 pemphigoid, a new entity of an autoimmune bullous disease. In this decade, we have experienced over 70 cases of this disease. Although the number of the cases of anti‐laminin γ1 pemphigoid is half as many as the number of definitely diagnosed cases of epidermolysis bullosa acquisita in the same duration, a considerable number of the cases could be clinically misdiagnosed as epidermolysis bullosa acquisita. Unveiling the pathogenicity and development of a useful diagnostic method is necessary for appropriate management of this new disease.

IgG Autoantibodies Against Desmocollin 3 in Pemphigus Sera Induce Loss of Keratinocyte Adhesion

Pemphigus is considered an autoimmune bullous skin disorder associated with IgG against the desmosomal components, desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1). This concept is supported by the in vitro and in vivo pathogenicity of anti-Dsg3/Dsg1 IgG and the mucosal blistering phenotype of mice with a genetic deficiency of Dsg3. Mice deficient for another desmosomal adhesion molecule, desmocollin 3 (Dsc3), show a similar pemphigus phenotype, and we investigated the pathogenicity of Dsc3-reactive IgG autoantibodies that were identified previously in a subset of patients with atypical pemphigus. We here demonstrate that IgG against Dsc3 causes loss of adhesion of epidermal keratinocytes. Specifically, IgG against Dsc3 was purified from Dsc3-reactive pemphigus sera by affinity column chromatography using recombinant human Dsc3. Affinity purified IgG was functionally active and did not only react with recombinant Dsc3 but also with epidermis and cultured human keratinocytes. Moreover, Dsc3-reactive IgG induced loss of adhesion of epidermal keratinocytes in a dispase-based keratinocyte dissociation assay that was reversed on pre-adsorption with human Dsc3 but not Dsg3. These findings demonstrate that IgG autoantibodies against an additional component of the desmosomes, Dsc3, induce loss of keratinocyte adhesion and thus may contribute to blister formation in pemphigus.

Lesional Th17 cells and regulatory T cells in bullous pemphigoid

Abstract:  Th17 cells play crucial roles in the pathogenesis of autoimmune diseases. We previously reported that Th17 cells are recruited to the lesional skin in pemphigus vulgaris (PV) and pemphigus foliaceus (PF). The aim of this study was to evaluate lesional Th17 cells and Treg cells in bullous pemphigoid (BP). Correlations between these cells and disease severity of BP were also evaluated. Immunohistochemical studies showed that both IL‐17+ and Foxp3+ cells were present in higher numbers in BP lesions, compared with control skin. IL‐17/CD4 ratio in BP was significantly higher than that in PF. Foxp3/CD4 ratio in BP was significantly less than that in either PV or PF. There were no obvious correlations between these cells and disease severity of BP. This study suggests that, compared with pemphigus, BP shows more Th17 cell‐related inflammation and less Treg‐related regulation.

Autoimmunity to Desmocollin 3 in Pemphigus Vulgaris

Pemphigus vulgaris is a blistering disease associated with autoantibodies to the desmosomal adhesion protein, desmoglein 3. Genetic deficiency of desmoglein 3 in mice mimics autoimmunity to desmoglein 3 in pemphigus vulgaris, with mucosal-dominant blistering in the suprabasal layer of the epidermis. Mice with an epidermal-specific deletion of desmocollin 3, the other major desmosomal cadherin isoform expressed in the basal epidermis, develop suprabasal blisters in skin that are histologically identical to those observed in pemphigus vulgaris, suggesting that desmocollin 3 might be a target of autoantibodies in some pemphigus vulgaris patients. We now demonstrate that desmocollin 3 is an autoantigen in pemphigus vulgaris, illustrated in a patient with mucosal-dominant blistering. Six of 38 pemphigus vulgaris and one of 85 normal serum samples immunoprecipitate desmocollin 3 (P = 0.003). Incubation of patient IgG with human keratinocytes causes loss of intercellular adhesion, and adsorption with recombinant desmocollin 3 specifically prevents this pathogenic effect. Additionally, anti-desmocollin 3 sera cause loss of keratinocyte cell surface desmocollin 3, but not desmoglein 3 by immunofluorescence, indicating distinct cellular pathogenic effects in anti-desmocollin and anti-desmoglein pemphigus, despite their identical clinical presentations. These data demonstrate that desmocollin 3 is a pathogenic autoantigen in pemphigus vulgaris and suggest that pemphigus vulgaris is a histological reaction pattern that may result from autoimmunity to desmoglein 3, desmocollin 3, or both desmosomal cadherins.

Epitope Spreading Is Rarely Found in Pemphigus Vulgaris by Large-Scale Longitudinal Study Using Desmoglein 2–Based Swapped Molecules

Epitope spreading is involved in inducing and maintaining self-reactivity. Epitope spreading in pemphigus vulgaris (PV), caused by IgG autoantibodies to desmoglein 3 (Dsg3) and Dsg1, was previously analyzed using Dsg3/Dsg1 extracellular domain-swapped molecules. However, precise identification of the responsible epitopes in each molecule by using only this method was problematic. In this study, we studied epitope spreading in PV by a novel immunoprecipitation-immunoblot method using Dsg3 (or Dsg1)/Dsg2 domain-swapped molecules, which overcomes the problems associated with the previous approaches. We analyzed the antigenic epitopes recognized by 212 sera collected from 53 PV patients at multiple disease stages. The major epitopes were present at the N-terminal region of Dsgs and were unchanged over the course of the disease in both anti-Dsg3 mucosal dominant-type PV and anti-Dsg3/Dsg1 mucocutaneous-type PV. These N-terminal epitopes were calcium dependent. Circulating antibodies in paraneoplastic pemphigus and pemphigus herpetiformis had unique epitope distributions, although the Dsg N-termini still contained the major epitopes. These results suggest that, after onset, intramolecular and intermolecular epitope spreading among extracellular domains on Dsg3 and Dsg1 is rare in PV and has no correlation with disease course.

Anti-desmocollin autoantibodies in nonclassical pemphigus.

Despite the established pathogenic role of anti‐desmoglein (Dsg) antibodies in classical pemphigus, the significance of autoantibodies to another desmosomal cadherin, desmocollin (Dsc) is at present unknown. No consistent immunoassay for immunoglobulin (Ig) G autoantibodies to Dscs has been developed.

Clinical and immunological findings in 104 cases of paraneoplastic pemphigus

Although there are many reports of sporadic patients with paraneoplastic pemphigus (PNP), only a few systematic studies on large cohorts of patients with PNP have been reported.