A perspective of pemphigus from bedside and laboratory-bench

Pregnancy‐triggered pemphigus vulgaris with favorable fetal outcomes: A case report

Pemphigus vulgaris is an autoimmune bullous dermatosis which if occurred during pregnancy may result in neonatal complications. In this study we report a 41 years old woman with pemphigus vulgaris that triggered by pregnancy in first trimester of pregnancy followed by the premature birth of a healthy neonate.

IgG4, complement, and the mechanisms of blister formation in pemphigus and bullous pemphigoid

Autoimmune bullous diseases are at the forefront of the research field on autoimmune diseases. Pemphigus and pemphigoid were historical entities in the world of descriptive dermatology for a long time. Recently, however, dermatologists and skin biologists have elegantly explained the novel pathomechanism of pemphigus and pemphigoid diseases. IgG4 is the major subclass of autoantibodies in autoimmune bullous diseases and is known to have little activity to activate complement. It is quite acceptable for pemphigus, because acantholysis in pemphigus has been demonstrated to be complement-independent. On the other hand, subepidermal blister formation in bullous pemphigoid has been believed to be complement-dependent. Therefore, the role of IgG4 autoantibodies on blister formation in bullous pemphigoid remains controversial. Here, we examine the progress of research on the mechanisms of blister formation in autoimmune bullous diseases. We focus on the complement-dependent and independent blistering in bullous pemphigoid using comparisons between pemphigus diseases. In addition, we review the current understanding of the role of IgG4 antibodies in bullous pemphigoid.

Pemphigus and pregnancy. Analysis and summary of case reports over 49 years

Pemphigus is a group of immune-mediated bullous disorders, which often cause fragile blisters and extensive lesions of the skin or mucous membranes, such as in the mouth. This disease could be life-threatening in some cases. During pregnancy, its condition will become more complicated due to the change in the mother’s hormone level and the effect of drug therapy on both the mother and her fetus. Thus, it will be more difficult to identify the clinical manifestations and to establish the treatment plan. In this article, we present a comprehensive review of pemphigus and pregnancy by analyzing 47 cases of pemphigus reported between 1966 and 2014, with diagnosis before or during pregnancy. The aim of this study is to make a comprehensive review of pemphigus and pregnancy, provide organized and reliable information for obstetricians, dermatologists, physicians, and oral medicine specialists.

Bullous diseases: Kids are not just little people

Bullous diseases may be rare; however, this does not preclude the clinician from being familiar with their manifestations and treatment. After ruling out infection, genetically inherited blistering diseases are more likely to be the cause of blistering or erosions in the neonatal period, whereas immunobullous diseases are more common in adults. Published literature on immunobullous disorders reflects information gleaned from case reports and open-label case series; prospective studies and evidence-based treatments are limited. Although there may be overlapping clinical features, significant clinical differences exist between adults and children. Evidence-based treatment guidelines are limited, and information from the adult literature cannot be readily generalized to the pediatric population. This paper reviews the approach to blistering conditions and the differences among bullous pemphigoid, linear immunoglobulin A disease, dermatitis herpetiformis, pemphigus foliaceus, pemphigus vulgaris, and paraneoplastic pemphigus in adult versus pediatric patients.

Non-classical forms of pemphigus: pemphigus herpetiformis, IgA pemphigus, paraneoplastic pemphigus and IgG/IgA pemphigus

The pemphigus group comprises the autoimmune intraepidermal blistering diseases classically divided into two major types: pemphigus vulgaris and pemphigus foliaceous. Pemphigus herpetiformis, IgA pemphigus, paraneoplastic pemphigus and IgG/IgA pemphigus are rarer forms that present some clinical, histological and immunopathological characteristics that are different from the classical types. These are reviewed in this article. Future research may help definitively to locate the position of these forms in the pemphigus group, especially with regard to pemphigus herpetiformis and the IgG/ IgA pemphigus.

150(th) anniversary series: Desmosomes and autoimmune disease, perspective of dynamic desmosome remodeling and its impairments in pemphigus

Desmosomes are the most important intercellular adhering junctions that adhere two adjacent keratinocytes directly with desmosomal cadherins, that is, desmogleins (Dsgs) and desmocollins, forming an epidermal sheet. Recently, two cell-cell adhesion states of desmosomes, that is, "stable hyper-adhesion" and "dynamic weak-adhesion" conditions have been recognized. They are mutually reversible through cell signaling events involving protein kinase C (PKC), Src and epidermal growth factor receptor (EGFR) during Ca(2+)-switching and wound healing. This remodeling is impaired in pemphigus vulgaris (PV, an autoimmune blistering disease), caused by anti-Dsg3 antibodies. The antibody binding to Dsg3 activates PKC, Src and EGFR, linked to generation of dynamic weak-adhesion desmosomes, followed by p38MAPK-mediated endocytosis of Dsg3, resulting in the specific depletion of Dsg3 from desmosomes and acantholysis. A variety of pemphigus outside-in signaling may explain different clinical (non-inflammatory, inflammatory, and necrolytic) types of pemphigus. Pemphigus could be referred to a "desmosome-remodeling disease involving pemphigus IgG-activated outside-in signaling events".

Plakophilin-1 protects keratinocytes from pemphigus vulgaris IgG by forming calcium-independent desmosomes

Plakophilin-1 (PKP-1) is an armadillo family protein critical for desmosomal adhesion and epidermal integrity. In the autoimmune skin-blistering disease pemphigus vulgaris (PV), autoantibodies (IgG) target the desmosomal cadherin desmoglein 3 (Dsg3) and compromise keratinocyte cell-cell adhesion. Here, we report that enhanced expression of PKP-1 protects keratinocytes from PV IgG-induced loss of cell-cell adhesion. PKP-1 prevents loss of Dsg3 and other desmosomal proteins from cell-cell borders and prevents alterations in desmosome ultrastructure in keratinocytes treated with PV IgG. Using a series of Dsg3 chimeras and deletion constructs, we find that PKP-1 clusters Dsg3 with the desmosomal plaque protein desmoplakin in a manner dependent on the plakoglobin-binding domain of the Dsg3 tail. Furthermore, PKP-1 expression transforms desmosome adhesion from a calcium-dependent to a calcium-independent and hyperadhesive state. These results demonstrate that manipulating the expression of a single desmosomal plaque protein can block the pathogenic effects of PV IgG on keratinocyte adhesion.

Pathological findings of pemphigus vulgaris showing giant cobblestone-like conjunctival papillae

Purpose

To describe the pathophysiological findings of a patient with pemphigus vulgaris (PV) showing giant conjunctival papillae.

Methods

A 64-year-old man who had mucosal-dominant PV with giant conjunctival papillae, resembling those of vernal keratoconjunctivitis (VKC), underwent an ophthalmological workup. The clinical and pathological findings were investigated.

Results

Ophthalmic interventions were unable to provide the desired beneficial effects, and multiple excisions were necessary to remove the proliferative conjunctival lesions. Histopathological investigations of the excised tissues demonstrated acantholysis and a subconjunctival infiltration with numerous inflammatory cells such as lymphocytes, plasma cells, and neutrophils. However, in contrast to typical VKC, mast cells and eosinophils were rarely found in the subconjunctival tissues. Direct immunofluorescent staining showed a significant deposition of immunoglobulin G and complement component 3 in the epithelial intercellular substance, consistent with mucosal-dominant PV. Then, the patient was hospitalized because of oral erosion exacerbation and malnutrition. Because of the patient's declining general condition, we administered an increasing dose of a systemic steroid with an intravenous immunoglobulin, after which his ocular lesions and symptoms improved.

Conclusions

The histological conjunctival papilla findings were quite different from those of VKC papillae. If PV causes a lesion in a patient, systemic immunosuppression might be more effective than topical ophthalmic treatment because of overall immunological involvement.

Cytokine networks in Pemphigus vulgaris: An integrated viewpoint

Pemphigus vulgaris (PV) is an autoimmune bullous skin disease where tolerance to the desmosomal protein desmoglein 3 (Dsg3), and perhaps additional epidermal targets, is lost, leading to the production of autoantibodies directed against cellular adhesion molecules. As auto-reactive T cells are involved in the induction and maintenance of antibody production, it has been hypothesized that cytokines play a crucial role in disease pathogenesis. Qualitative and quantitative alterations in cytokine profiles have been previously reported; however, despite recent advancements, the characterization of the disease supporting cytokine network in PV has yet to be fully elucidated. It is overwhelmingly suggested that PV is a TH2-mediated disease, confirmed by the majority of studies demonstrating an increase in TH2-type cytokines. Recently, a focus has been placed on the contribution of the newly discovered TH17 subset to autoimmune states, and current evidence suggests that this inflammatory pathway may play a role in PV as well. Anti-cytokine medications are on the forefront as potential therapeutic options, and the growing number of reports of clinical benefit serves to confirm the major contribution of various inflammatory mediators in the development of disease phenotype. This work aimed to comprehend the complexity of cytokine and T cell involvement in pemphigus, taking account of known information and emphasizing the areas where additional research would be of great benefit, particularly in pharmacological development and expansion of the pemphigus therapeutic armamentarium.

Diagnosis and treatment of pemphigus

Pemphigus is an autoimmune bullous disease, in which autoantibodies react with the cell–cell adhesion structures, desmosomes, causing blisters and erosions on the oral mucosa and skin. Pemphigus is divided into two major subtypes: pemphigus vulgaris and pemphigus foliaceus. Oral corticosteroids are the primary treatment modality for pemphigus, while other therapeutic options, such as steroid pulse therapy, immunosuppressants, intravenous immunoglobulins, plasmapheresis and anti-CD20 monoclonal antibody therapy, are occasionally employed. Immunosuppressants used to treat pemphigus include azathioprine, cyclophosphamide, cyclosporine, mycophenolate mofetil and mizoribine. In this review, we summarize the current concepts of immunotherapy for the treatment of pemphigus in the Japanese population.

Detection of antibodies against the non-calcium-dependent epitopes of desmoglein 3 in pemphigus vulgaris and their pathogenic significance

BACKGROUND

Antidesmoglein (anti-Dsg) 3 serum antibody titres are usually correlated with the disease activity of pemphigus vulgaris (PV), but some patients retain high titres even in remission.

OBJECTIVES

The aim of our study was to determine whether anti-Dsg3 antibodies in PV sera recognized calcium (Ca(2+) )-dependent or non-Ca(2+) -dependent epitopes, and to evaluate their pathogenicity.

METHODS

Dsg3 baculoprotein-coated enzyme-linked immunosorbent assay (ELISA) plates were treated with 0.5 mmol L(-1) ethylenediaminetetraacetic acid (EDTA). The binding ability of anti-Dsg3 monoclonal antibodies (mAbs) was analysed. Eight of the 83 patients with PV who were screened had elevated Dsg3 ELISA index values > 00 in remission. The binding ability of these PV sera was analysed. We evaluated the pathogenicity of anti-Dsg3 serum antibodies against the non-Ca(2+) -dependent epitopes using a dissociation assay.

RESULTS

The reactivity of pathogenic anti-Dsg3 mAbs against the Ca(2+) -dependent epitopes diminished markedly in the EDTA-treated ELISA, whereas no such reduction was observed in mAbs against the non-Ca(2+) -dependent epitopes. The sera of all the patients contained antibodies against both Ca(2+) -dependent and non-Ca(2+) -dependent epitopes. In six out of the eight patients, the ratio of antibodies against Ca(2+) -dependent to non-Ca(2+) -dependent epitopes decreased in remission. EDTA-treated Dsg3 baculoproteins adsorbed anti-Dsg3 serum antibodies against the non-Ca(2+) -dependent epitopes, but the remnant PV antibodies retained the ability to induce acantholysis in the dissociation assay.

CONCLUSIONS

We have established an assay to measure indirectly the titres of anti-Dsg3 serum antibodies against the Ca(2+) -dependent epitopes, based on the differences between EDTA-untreated and EDTA-treated ELISA index values, as a routine laboratory test to reflect the pathogenic anti-Dsg3 serum antibody titres more accurately.

Pathogenic relevance of IgG and IgM antibodies against desmoglein 3 in blister formation in pemphigus vulgaris

Pemphigus vulgaris is an autoimmune disease caused by IgG antibodies against desmoglein 3 (Dsg3). Previously, we isolated a pathogenic mAb against Dsg3, AK23 IgG, which induces a pemphigus vulgaris-like phenotype characterized by blister formation. In the present study, we generated a transgenic mouse expressing AK23 IgM to examine B-cell tolerance and the pathogenic role of IgM. Autoreactive transgenic B cells were found in the spleen and lymph nodes, whereas anti-Dsg3 AK23 IgM was detected in the cardiovascular circulation. The transgenic mice did not develop an obvious pemphigus vulgaris phenotype, however, even though an excess of AK23 IgM was passively transferred to neonatal mice. Similarly, when hybridoma cells producing AK23 IgM were inoculated into adult mice, no blistering was observed. Immunoelectron microscopy revealed IgM binding at the edges of desmosomes or interdesmosomal cell membranes, but not in the desmosome core, where AK23 IgG binding has been frequently detected. Furthermore, in an in vitro dissociation assay using cultured keratinocytes, AK23 IgG and AK23 IgM F(ab')(2) fragments, but not AK23 IgM, induced fragmentation of epidermal sheets. Together, these observations indicate that antibodies must gain access to Dsg3 integrated within desmosomes to induce the loss of keratinocyte cell-cell adhesion. These findings provide an important framework for improved understanding of B-cell tolerance and the pathophysiology of blister formation in pemphigus.

New non-invasive method for evaluation of the stratum corneum structure in diseases with abnormal keratinization by immunofluorescence microscopy of desmoglein 1 distribution in tape-stripped samples

The corneodesmosomes in the stratum corneum are critical for the maintenance of stratum corneum integrity. To evaluate the normal and diseased keratinization states in the epidermis, we studied the distribution of desmoglein 1 (DSG1), a major component of corneodesmosomes, in samples of the stratum corneum obtained by tape stripping, a non-invasive method. Samples were collected from lesional skin of four patients with psoriasis and three with lichen planus, and from non-lesional skin of three volunteers. Upper stratum corneum cells were obtained by tape stripping and skin biopsies were obtained from adjacent sites. Tape-stripped samples were examined by immunofluorescence microscopy using anti-DSG1 monoclonal antibody, in combination with histopathology of skin biopsies. In normal human stratum corneum, which shows basket-woven orthokeratosis, DSG1-containing fluorescent dots were distributed on the lateral cell-cell contact areas of plasma membrane, but not on the dorsal/ventral plasma membrane, and formed a well-ordered hexagonal network structure. In psoriatic stratum corneum, fluorescent dots were distributed throughout the cell membrane at ventral aspects of corneocytes as well as at the lateral cell-cell contacts. In lichen planus, fluorescent dots were distributed homogeneously and/or heterogeneously on the ventral surface in some cells. Adjacent cells lacked DSG1 at the lateral cell-cell contacts, but were instead separated by distinctive black-gap lines. These results suggest that the intercellular adhesion by DSG1 may depend on the lateral plasma membrane in normal human stratum corneum, on the dorsal/ventral plasma membrane in lichen planus, and on both lateral and dorsal/ventral plasma membranes in psoriatic stratum corneum. Tape stripping and DSG1 immunofluorescence visualizes adhesion features of corneocytes and has considerable potential for evaluation of abnormal keratinization and the process of healing in response to treatment.

Plakoglobin rescues adhesive defects induced by ectodomain truncation of the desmosomal cadherin desmoglein 1: implications for exfoliative toxin-mediated skin blistering

Desmoglein 1 (Dsg1) is a desmosomal cadherin that is essential to epidermal integrity. In the blistering diseases bullous impetigo and staphylococcal scalded-skin syndrome, pathogenesis depends on cleavage of Dsg1 by a bacterial protease, exfoliative toxin A, which removes residues 1 to 381 of the Dsg1 ectodomain. However, the cellular responses to Dsg1 cleavage that precipitate keratinocyte separation to induce blister formation are unknown. Here, we show that ectodomain-deleted Dsg1 (Δ381-Dsg1) mimics the toxin-cleaved cadherin, disrupts desmosomes, and reduces the mechanical integrity of keratinocyte sheets. In addition, we demonstrate that truncated Dsg1 remains associated with its catenin partner, plakoglobin, and causes a reduction in the levels of endogenous desmosomal cadherins in a dose-dependent manner, leading us to hypothesize that plakoglobin sequestration by truncated Dsg1 destabilizes other cadherins. Accordingly, a triple-point mutant of the ectodomain-deleted cadherin, which is uncoupled from plakoglobin, does not impair adhesion, indicating that this interaction is essential to the pathogenic potential of truncated Dsg1. Moreover, we demonstrate that increasing plakoglobin levels rescues cadherin expression, desmosome organization, and functional adhesion in cells expressing Δ381-Dsg1 or treated with exfoliative toxin A. Finally, we report that histone deacetylase inhibition up-regulates desmosomal cadherins and prevents the loss of adhesion induced by Dsg1 truncation. These findings further our understanding of the mechanism of exfoliative toxin-induced pathology and suggest novel strategies to suppress blistering in bulbous impetigo and staphylococcal scalded-skin syndrome.

The Thomsen-Friedenreich antigen-binding lectin jacalin interacts with desmoglein-1 and abrogates the pathogenicity of pemphigus foliaceus autoantibodies in vivo

Pemphigus foliaceus (PF) is an autoimmune skin blistering disease mediated by pathogenic autoantibodies against the desmosomal core glycoprotein desmoglein-1 (Dsg1). This study demonstrated that the O-glycan-specific plant lectin jacalin binds Dsg1 and inhibits the interaction of Dsg1/PF IgG. N-glycosylation is not involved in the interaction of Dsg1/jacalin or Dsg1/PF IgG. Subcutaneous injection of jacalin into neonatal mice drastically reduced PF IgG deposition at the epidermal cell surface and blocked PF IgG-induced skin blisters, both clinically and histologically. Interestingly, another plant lectin, peanut agglutinin, which shares the same carbohydrate specificity toward the O-linked carbohydrate structure known as Thomsen-Friedenreich antigen (TF antigen, Galβ1-3GalNAcα-O-Ser/Thr), also bound Dsg1 and blocked the skin blistering. In contrast, the plant lectin vicia villosa-B4 (VVL-B4), which shares the carbohydrate specificity toward the O-linked monosaccharide known as Thomsen-nouveau antigen (GalNAc-α1-O-Ser/Thr), did not bind Dsg1 and did not show a protective effect against the disease induced by the autoantibodies. Collectively, these results suggest that the binding of jacalin to O-linked TF carbohydrate motifs on Dsg1 impairs the Dsg1/PF autoantibody interactions and abrogates its pathogenicity in vivo. TF-specific binding ligands may have a potential therapeutic value for PF.

Herpes Simplex Virus Infection and Pemphigus

Pemphigus is a group of autoimmune blistering diseases of skin and/or mucous membranes caused by the presence of antibodies against adhesion molecules on the cell surface of keratinocytes. In genetically predisposed patients, several factors, including drugs, physical agents, neoplasms, hormones, and viruses, notably herpes simplex virus (HSV), have been hypothesized to trigger or exacerbate the disorder. To clarify whether HSV infection represents an aetiopathogenetic factor for pemphigus or a consequence of the immunosuppressive treatment, skin and/or mucosal swabs from 35 patients with pemphigus vulgaris or pemphigus foliaceus were tested for HSV by polymerase chain reaction. Twenty-three of these patients were newly diagnosed, while the remaining 12 had had a previous diagnosis and were under treatment with low-dosage oral corticosteroids. Repeat swabs were taken two weeks after starting intensive immunosuppressive therapy in 8 HSV-negative patients. All skin swabs (n = 27) resulted negative for both HSV-1/2, while oral swabs (n = 30) were positive for HSV-1 in 5 out of the 12 patients who were being treated with oral corticosteroids, but in none (n = 19) of the non-treated group (p = 0.0067, χ2 test). Five out of the 8 patients with repeat swabs became positive for HSV-1, prompting us to start antiviral therapy. In conclusion, HSV is unlikely to be a triggering factor for pemphigus, but its presence in pemphigus lesions seems to be a frequent and early complication of immunosuppression.