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Background: B-cell depletion therapy was demonstrated to be a valid and safe alternative as an adjuvant in oral-pharyngeal pemphigus vulgaris (OPV) patients. We aimed to assess its effects on anti-desmoglein (Dsg) 1 and 3 and leukocytes subsets profile in these patients' population. Methods and Materials: We evaluated the immunologic profile of 10 OPV patients treated with RTX as adjuvant by using the ELISA testing for anti-Dsg-1 and -3 titers and the immunophenotyping for B and T-cell lymphocyte subpopulations and compared them with the PDAI score for clinical remission. Results: A significant difference in medians between baseline, end of RTX therapy, and 6 months after RTX therapy was observed in Dsg-3 titer ( p < 0.001), in the CD8 ( p = 0.009), and CD20 counts ( p < 0.001). Multiple comparisons after Bonferroni adjustment confirmed such significant differences mainly between baseline and the end of RTX therapy and baseline and 6 months after RTX therapy. Only the anti-Dsg-3 titer at the end of RTX therapy demonstrated a slight positive correlation with the PDAI score at baseline ( p = 0.046, r = 0.652). Conclusions: B-cell depletion adjuvant therapy in OPV patients demonstrated a significant impact on anti-Dsg-3 titer and B and T-cell lymphocyte subpopulations profile.

The presence of anti-desmocollin (Dsc) antibodies is rarely described in autoimmune blistering diseases patients. Moreover, several clinical phenotypes of pemphigus may be associated with these antibodies. In this review we analyze clinicopathological, immunologic and outcome features of anti-Dsc autoimmune blistering diseases patients, to improve their diagnosis and management. We conducted a systematic search of PubMed and Embase (1990-present) for studies reporting cases of autoimmune blistering diseases with anti-Dsc antibodies. We classified the selected patients as patients with exclusively anti-Dsc autoantibodies, and patients with anti-Dsc and other autoantibodies. Of 93 cases with anti-Dsc autoantibodies included, 38 (41%) had exclusively these antibodies. Only 18% of patients presented with the typical clinicopathological phenotype of pemphigus vulgaris or pemphigus foliaceous. Mucosal involvement was seen in approximately half of the patients. Up to 18% of cases were associated with neoplasms. Acantholysis was described in 54% of cases with histopathological information. Treatments and outcomes vary in the different clinical phenotypes. The presence of anti-Dsc antibodies must be suspected mainly in those patients with either atypical pemphigus, in special with clinical pustules, or in cases showing intraepithelial or dermal neutrophilic/eosinophilic infiltrate on histological examination and dual pattern by direct immunofluorescence examination., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Bosch-Amate, Iranzo, Ivars, Mascaró Galy and España.)

Pemphigus is an autoimmune blistering disease mediated by autoantibodies directed against desmogleins (DSGs). We recently showed that first-line treatment with rituximab (RTX) enables more patients to achieve long-lasting remission off therapy than corticosteroids alone. To understand the immunological mechanisms that mediate long-lasting clinical remission after RTX treatment, we analyzed the phenotype of DSG-specific memory B cells and DSG-specific T follicular helper cells by flow cytometry and measured antibody-secreting cells by enzyme-linked immune absorbent spot in patients treated with corticosteroids alone or RTX. This post hoc analysis of the RITUX3 trial showed that RTX induced a significant decrease of IgG-switched DSG-specific memory B cells. Accordingly, anti-DSG antibody-secreting cells were no longer detected in patients in complete remission after RTX. In contrast, corticosteroids did not modify the frequency or the phenotype of DSG-specific memory B cells, and anti-DSG antibody-secreting cells were still detected after treatment, even in patients in remission. Using peptide-HLADRB1∗0402 tetramer staining, we identified DSG-3-specific T follicular helper cells, which dramatically decreased after RTX, while remaining stable after corticosteroid treatment. Our findings suggest that long-lasting response to RTX in pemphigus relies on the decrease of DSG-specific circulating T follicular helper cells, which correlates with a sustained depletion of IgG-switched memory autoreactive B cells, leading to the disappearance of anti-DSG antibody-secreting cells., (Copyright © 2021 CHU CHARLES NICOLLE ROUEN. Published by Elsevier Inc. All rights reserved.)

A possible etiological link between the onset of endemic pemphigus in Tunisia and bites of Phlebotomus papatasi, the vector of zoonotic cutaneous leishmaniasis, has been previously suggested. We hypothesized that the immunodominant P. papatasi salivary protein PpSP32 binds to desmogleins 1 and 3 (Dsg1 and Dsg3), triggering loss of tolerance to these pemphigus target autoantigens. Here, we show using far-Western blot that the recombinant PpSP32 protein (rPpSP32) binds to epidermal proteins with a MW of approximately 170 kDa. Coimmunoprecipitation revealed the interaction of rPpSP32 with either Dsg1 or Dsg3. A specific interaction between PpSP32 and Dsg1 and Dsg3 was further demonstrated by ELISA assays. Finally, mice immunized with rPpSP32 twice per week exhibited significantly increased levels of anti-Dsg1 and -Dsg3 antibodies from day 75 to 120. Such antibodies were specific for Dsg1 and Dsg3 and were not the result of cross-reactivity to PpSP32. In this study, we demonstrated for the first time to our knowledge a specific binding between PpSP32 and Dsg1 and Dsg3, which might underlie the triggering of anti-Dsg antibodies in patients exposed to sand fly bites. We also confirmed the development of specific anti-Dsg1 and -Dsg3 antibodies in vivo after PpSP32 immunization in mice. Collectively, our results provide evidence that environmental factors, such as the exposure to P. papatasi bites, can trigger the development of autoimmune antibodies.

Pemphigus vulgaris (PV) is an autoimmune bullous disease of the skin and mucous membranes characterized by the presence of circulating and tissue-bound autoantibodies against keratinocyte cell surface antigens, specifically desmoglein (Dsg) 1 and 3. The pathogenic role of anti-Dsg antibodies is well-established, while the mechanism of blister formation is only partly defined. We have applied a previously developed method for the efficient immortalization of IgG+ memory B cells to identify novel target antigens in PV. A human monoclonal antibody reactive with a hitherto unreported non-Dsg antigen was isolated. Immunoprecipitation and immunoblotting studies with keratinocyte extracts indicated α-catenin as the putative antigen, then confirmed by immunoblotting on the recombinant protein. Four of ten PV sera reacted with recombinant α-catenin. Although the isolated human monoclonal antibody was per se unable to dissociate keratinocyte monolayers and also to synergize with a pathogenic antibody in vitro , further studies are warranted to assess its possible in vivo contribution in the multifactorial pathogenesis and heterogeneous manifestations of PV disease.

Fogo selvagem or endemic pemphigus foliaceus is an autoimmune acantholytic anti-cadherin bullous disease that primarily affects seborrheic areas, which might disseminate. Brazil has the world's largest number of patients, mainly in the Central-West region, but the disease has also been reported in other South American countries. It affects young people and adults who have been exposed to rural areas, with occurrence of familial cases. Anti-desmoglein-1 autoantibodies are directed against desmosomal structures, with loss of adhesion of the upper layers of the epidermis, causing superficial blisters. The etiology is multifactorial and includes genetic, immune, and environmental factors, highlighting hematophagous insect bites; drug-related factors are occasionally involved. Flaccid blisters readily rupture to yield erosive-crusty lesions that sometimes resemble seborrheic dermatitis, actinic keratosis, and chronic cutaneous lupus erythematosus. The clinical presentation varies from localized to disseminated lesions. Clinical suspicion should be confirmed with histopathological and immunofluorescence tests, among others. The progression is usually chronic, and therapy varies according to clinical presentation, but generally requires systemic corticosteroid therapy associated with adjuvant immunosuppressive treatment to decrease the adverse effects of corticosteroids. Once the disease is under control, many patients remain stable on low-dose medication, and a significant proportion achieve remission.

Autoimmune bullous disorders (AIBDs) are a heterogeneous group of rare diseases clinically characterized by erosions and/or blisters on the skin and mucous membranes. AIBDs can be categorized into two groups: pemphigus diseases, characterized by intraepidermal blistering and autoantibodies against desmosomal proteins such as desmoglein (Dsg) 1, Dsg3, members of the plakin family, and subepidermal AIBDs, comprised of pemphigoid diseases and dermatitis herpetiformis. Autoantibodies in dermatitis herpetiformis target transglutaminases 2 and 3, while in pemphigoid disease, autoantibodies are directed against structural proteins of the dermal-epidermal junction. Although analysis of a perilesional biopsy with direct immunofluorescence (IF) microscopy is still the diagnostic gold standard, several assays have become widely available that allow serological diagnosis in the majority of patients. Standard serological diagnosis includes indirect IF on monkey esophagus and salt-split human skin. Assays to further characterize autoantibody specificity include ELISA systems based on recombinant forms of the immunodominant regions of the target antigens as well as multivariant indirect IF microscopy tests with several miniature substrates. These serological assays are complemented by various in-house assays using immunoblotting and ELISA, which are only available in specialized laboratories. Here we review new developments in the diagnosis of AIBDs and describe state-of-the-art diagnostic procedures for this group of diseases., (© 2018 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.)

Several sporadic cases, in which direct and indirect immunofluorescence studies simultaneously detected IgG and IgA autoantibodies to keratinocyte cell surfaces, have been reported mainly under the name of IgG/IgA pemphigus. However, there have been no systematic studies for this condition. In this study, we collected 30 cases of this condition from our cohort of more than 5,000 autoimmune bullous disease cases, which were consulted for our diagnostic methods from other institutes, and summarized their clinical and immunological findings. Clinically, there was no male-female prevalence, mean age of disease onset was 55.6 years, and mean duration before this condition was suspected was 18 months. The patients showed clinically bullous and pustular skin lesions preferentially on the trunk and extremities, and histopathologically intraepidermal pustules and blisters with infiltration of neutrophils and eosinophils. Immunologically, ELISAs frequently detected IgG and IgA autoantibodies to both desmogleins and desmocollins. From the characteristic clinical, histopathological, and immunological features, which are considerably different from those in classical IgG types of pemphigus, we propose this disease as a new disease entity with preferential name of intercellular IgG/IgA dermatosis (IGAD). This was the largest study of IGAD to date.

Pemphigus vulgaris (PV) belongs to an autoimmune disease cluster that includes autoimmune thyroid disease (AITD), suggesting common mechanisms driving autoimmune susceptibility. Our group has shown that PV patients exhibit significant reactivity to AITD-related anti-thyroid peroxidase (anti-TPO), and anti-TPO antibodies affect signaling pathways in keratinocytes similar to anti-desmoglein (Dsg) 3 antibodies. To further assess the relevance of anti-TPO reactivity in PV, we analyzed anti-TPO levels in 280 PV and 167 healthy control serum samples across a comprehensive set of variable and static parameters of disease activity and etiopathogenesis. PV patients have significantly higher activity rates (A.R.s) for anti-TPO than healthy controls, but levels do not differ between phases of clinical activity and remission. Patients that carry both the PV-associated human leukocyte antigen (HLA) alleles DRB1*0402 and DQB1*0503, or DQB1*0503 alone show a low prevalence of anti-TPO (A.R. 9.5 and 4.8%, respectively), while patients that lack expression of these alleles or carry DRB1*0402 alone have a much higher prevalence of anti-TPO (A.R. 23.1 and 15.8%, respectively), suggesting that the absence of DQB1*0503 may predispose patients to the development of anti-TPO antibodies. Similarly, anti-Dsg1 - /3 - patients have a higher anti-TPO A.R. (26.9%) than anti-Dsg1 - /3 + (18.8%), anti-Dsg1 + /3 - (14.3%), and anti-Dsg1 + /3 + (3.9%) patients. Our data suggest that anti-TPO reactivity in PV is driven by genetic markers that may be in linkage disequilibrium with the established PV-susceptibility alleles and that this association drives the selection of a combination of anti-Dsg and anti-TPO antibodies, with anti-TPO filling the gap in active patients that do not carry the established PV-associated autoantibodies and/or are lacking the established PV-HLA-susceptibility alleles.

Pemphigus is a blistering disease characterized by pemphigus autoantibodies (PVIgG) directed mostly against desmogleins (Dsgs), resulting in the loss of keratinocyte adhesion (acantholysis). Yet, the mechanisms underlying blister formation remain to be clarified. We have shown previously that anti-Fas ligand (FasL) antibody (Ab) prevents PVIgG-induced caspase-8 activation and Dsg cleavage in human keratinocytes, and that sera from pemphigus patients contain abnormally increased levels of FasL. Here, we demonstrate that recombinant FasL induces the activation of caspases prior to Dsg degradation, and anti-FasL Ab prevents acantholysis in cultured keratinocytes. Moreover, the silencing of FasL reduces PVIgG-induced caspase-8 activation and Dsg3 cleavage. Following injection of PVIgG into mice, FasL is upregulated at 1-3 h and is followed by caspase-8-mediated keratinocyte apoptosis, before blister formation. The administration of anti-FasL Ab after PVIgG injection blocks blister formation in mice. Furthermore, we injected PVIgG into two different gene-targeted mutant mice that selectively lack either secreted soluble FasL (sFasL), FasL Δs/Δs mice, or the membrane-bound form of FasL (mFasL), FasL Δm/Δm mice. After PVIgG treatment, blisters are only visible in FasL Δm/Δm animals, lacking mFasL, but still producing sFasL, similar to wild-type (C57BL/6) animals. By contrast, a significant decrease in the relative acantholytic area is observed in the FasL Δs/Δs animals. These results demonstrate that soluble FasL plays a crucial role in the mechanisms of blister formation, and blockade of FasL could be an effective therapeutic approach for pemphigus.

Competing Interests: We have read and understood BMJ policy on declaration of interests and declare no competing interests.

The autoimmune blistering skin disease pemphigus is caused by IgG autoantibodies against desmosomal cadherins, but the precise mechanisms are in part a matter of controversial discussions. This review focuses on the currently existing models of the disease and highlights the relevance of desmoglein-specific versus nondesmoglein autoantibodies, the contribution of nonautoantibody factors, and the mechanisms leading to cell dissociation and blister formation in response to autoantibody binding. As the review brings together the majority of laboratories currently working on pemphigus pathogenesis, it aims to serve as a solid basis for further investigations for the entire field., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Pemphigus is a severe autoimmune blistering disease mediated by pathogenic anti-desmoglein antibodies leading to an inter keratinocyte disjunction. Rituximab is a monoclonal antibody that binds to the CD-20 antigen of B lymphocytes, which causes B-cell depletion and a subsequent reduction in pathogenic autoantibodies. Its therapeutic role in pemphigus has been progressively growing with increasing evidence of successful outcomes. Rituximab was initially off-labeled used as an alternative in patients with recalcitrant or relapsing pemphigus and in patients with contraindications to systemic corticosteroids. Recently, a large randomized clinical trial has shown that first-line use of rituximab combined with short-term prednisone regimen was both more effective and potentially safer than a standard regimen of high doses of corticosteroids in patients with moderate to severe pemphigus.

This viewpoint highlights major, partly controversial concepts about the pathogenesis of pemphigus. The monopathogenic theory explains intra-epidermal blistering through the "desmoglein (Dsg) compensation" hypothesis, according to which an antibody-dependent disabling of Dsg 1- and/or Dsg 3-mediated cell-cell attachments of keratinocytes (KCs) is sufficient to disrupt epidermal integrity and cause blistering. The multipathogenic theory explains intra-epidermal blistering through the "multiple hit" hypothesis stating that a simultaneous and synchronized inactivation of the physiological mechanisms regulating and/or mediating intercellular adhesion of KCs is necessary to disrupt epidermal integrity. The major premise for a multipathogenic theory is that a single type of autoantibody induces only reversible changes, so that affected KCs can recover due to a self-repair. The damage, however, becomes irreversible when the salvage pathway and/or other cell functions are altered by a partnering autoantibody and/or other pathogenic factors. Future studies are needed to (i) corroborate these findings, (ii) characterize in detail patient populations with non-Dsg-specific autoantibodies, and (iii) determine the extent of the contribution of non-Dsg antibodies in disease pathophysiology., (© 2016 The Authors Experimental Dermatology Published by John Wiley & Sons Ltd.)

Pemphigus vulgaris (PV) is a rare blistering skin disorder characterized by the disadhesion of keratinocytes due to autoantibody attack against epidermal targets including desmoglein (Dsg) 3, Dsg 1 and possibly other adhesion and non-adhesion molecules. The mechanisms leading to immune-mediated pathology in PV are multifactorial and not fully understood. Recently, oxidative stress (antioxidant/oxidant disequilibrium) has been proposed as a contributory mechanism of autoimmune skin diseases, including PV. In this study, we directly assessed oxidative stress via measurement of total antioxidant capacity (TAC) using ELISA in 47 PV patients, 25 healthy controls and 18 bullous pemphigoid (BP) patients. We also performed microarray gene expression analysis on a separate set of 21 PV patients and 10 healthy controls to evaluate transcriptional dysregulation in oxidative stress-related pathways. Our data indicate that there is a significant reduction in TAC levels in PV patients compared with healthy controls, as well as BP patients. Furthermore, PV patients with active disease have significantly lower TAC levels than PV patients in remission. We also find that HLA allele status has a significant influence on oxidative stress. These findings are corroborated by microarray analysis showing differentially expressed genes involved in oxidative stress between the aforementioned groups. Collectively, our findings provide support for a role of oxidative stress in PV. Whether increased oxidative stress leads to disease manifestation and/or activity, or if disease activity leads to increased oxidative stress remains unknown. Future longitudinal studies may help to further elucidate the relationship between PV and oxidative stress.

Background: The pemphigus group is characterized by the presence of circulating immunoglobulins against desmosomes. IgG/IgA pemphigus is defined by the presence of IgG and IgA cell surface deposits upon direct immunofluorescence (DIF) and/or circulating IgG and IgA autoantibodies upon indirect immunofluorescence. Previous reports of patients with IgG/IgA pemphigus are sparse. Whether IgG/IgA pemphigus is best classified as a subtype of IgG (classic) pemphigus or IgA pemphigus, or as a distinct entity, has yet to be determined., Objectives: We compared the features of patients with IgG/IgA pemphigus to those of IgG pemphigus and IgA pemphigus., Methods: Retrospective clinicopathologic study of patients with IgG, IgG/IgA, and IgA pemphigus evaluated at our clinic (1993-2013)., Results: We included 26, 13, and seven patients with IgG, IgG/IgA, and IgA pemphigus, respectively. Patients with IgG/IgA pemphigus did not differ significantly from patients with IgG pemphigus in terms of clinical and microscopic features, DIF findings, anti-desmoglein antibody values, and treatments required. However, patients with IgG/IgA pemphigus were significantly different from patients with IgA pemphigus regarding intertriginous distribution (P = 0.038) and pustular lesions (P < 0.001), acantholysis (P = 0.043), and presence of intercellular C3 deposits on DIF (P < 0.001)., Conclusion: Comparative clinicopathologic data imply that IgG/IgA pemphigus may best be regarded as a variant of IgG pemphigus and distinct from IgA pemphigus., (© 2015 The International Society of Dermatology.)

Patients with pemphigus vulgaris (PV) harbor antibodies reactive against self-antigens expressed at the surface of keratinocytes, primarily desmoglein (Dsg) 3 and, to a lesser extent, Dsg1. Conventionally, only antibodies targeting these molecules have been thought to contribute to disease pathogenesis. This notion has been challenged by a growing pool of evidence that suggests that antibodies toward additional targets may play a role in disease. The aims of this study were to (i) establish high-throughput protein microarray technology as a method to investigate traditional and putative autoantibodies (autoAbs) in PV and (ii) use multiplexed protein array technology to define the scope and specificity of the autoAb response in PV. Our analysis demonstrated significant IgG reactivity in patients with PV toward the muscarinic acetylcholine receptor subtypes 3, 4, and 5 as well as thyroid peroxidase. Furthermore, we found that healthy first- and second-degree relatives of patients with PV express autoAbs toward desmoglein and non-Dsg targets. Our analysis also identified genetic elements, particularly HLA, as key drivers of autoAb expression. Finally, we show that patients with PV exhibit significantly reduced IgM reactivity toward disease-associated antigens relative to controls. The use of protein microarrays to profile the autoAb response in PV advanced the current understanding of disease and provided insight into the complex relationship between genetics and disease development.

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are two severe autoimmune bullous diseases of the mucosae and/or skin associated with autoantibodies directed against desmoglein (Dsg) 3 and/or Dsg1. These two desmosomal cadherins, typifying stratified epithelia, are components of cell adhesion complexes called desmosomes and represent extra-desmosomal adhesion receptors. We herein review the advances in our understanding of the immune response underlying pemphigus, including human leucocyte antigen (HLA) class II-associated genetic susceptibility, characteristics of pathogenic anti-Dsg antibodies, antigenic mapping studies as well as findings about Dsg-specific B and T cells. The pathogenicity of anti-Dsg autoantibodies has been convincingly demonstrated. Disease activity and clinical phenotype correlate with anti-Dsg antibody titers and profile while passive transfer of anti-Dsg IgG from pemphigus patients' results in pemphigus-like lesions in neonatal and adult mice. Finally, adoptive transfer of splenocytes from Dsg3-knockout mice immunized with murine Dsg3 into immunodeficient mice phenotypically recapitulates PV. Although the exact pathogenic mechanisms leading to blister formation have not been fully elucidated, intracellular signaling following antibody binding has been found to be necessary for inducing cell-cell dissociation, at least for PV. These new insights not only highlight the key role of Dsgs in maintenance of tissue homeostasis but are expected to progressively change pemphigus management, paving the way for novel targeted immunologic and pharmacologic therapies.

Pemphigus vulgaris (PV) is a severe autoimmune disease in which autoantibodies against the desmosomal cell adhesion molecules desmoglein (Dsg) 1 and Dsg3 cause intraepidermal blister formation. Mechanistically, the fundamental question is still unresolved whether loss of cell cohesion is a result of (1) direct inhibition of Dsg interaction by autoantibodies or (2) intracellular signaling events, which are altered in response to antibody binding and finally cause desmosome destabilization. We used atomic force microscopy (AFM) to perform Dsg3 adhesion measurements on living keratinocytes to investigate the contributions of direct inhibition and signaling to loss of cell cohesion after autoantibody treatment. Dsg3 binding was rapidly blocked following antibody exposure under conditions where no depletion of surface Dsg3 was detectable, demonstrating direct inhibition of Dsg3 interaction. Inhibition of p38MAPK, a central signaling molecule in PV pathogenesis, abrogated loss of cell cohesion, but had a minor effect on loss of Dsg3 binding. Similarly, the cholesterol-depleting agent methyl-β-cyclodextrin (β-MCD) fully blocked cell dissociation, but did not restore Dsg3 interactions or prevent the activation of p38MAPK. These results demonstrate that inhibition of Dsg3 binding is not sufficient to cause loss of cell cohesion, but rather alters signaling events which, in lipid raft-dependent manner, induce cell dissociation.

Background: Pemphigus vulgaris (PV) is an autoimmune blistering disease mediated by IgG autoantibodies targeting desmogleins (Dsgs). The anti-CD20 monoclonal antibody rituximab is increasingly used in corticosteroid-resistant PV patients. In a subset of rituximab-treated patients in remission, high ELISA index values have been reported; however, their significance remains so far unclear., Objective: To address the discrepancy between anti-Dsg3 serum antibody titers and disease severity., Materials & Methods: 6 rituximab-treated PV patients were prospectively followed-up for two years and anti-Dsg3 autoantibodies levels and pathogenic activity were measured., Results: All patients achieved complete remission without any serious side effects. Both anti-Dsg3 autoantibodies (p = 0.031) and their pathogenic activity (p = 0.003) were significantly related to disease severity. However, in selected patients, the dissociation index was a more sensitive indicator for PV clinical activity than the ELISA index., Conclusion: Our findings have demonstrated the existence of non-pathogenic autoantibodies in PV patients in remission, establishing the basis for the design of a system able to precisely monitor the course of disease.

Pemphigus vulgaris (PV) is a life-long, potentially fatal IgG autoantibody-mediated blistering disease targeting mucocutaneous keratinocytes (KCs). PV patients develop pathogenic anti-desmoglein (Dsg) 3 ± 1 and antimitochondrial antibodies (AMA), but it remained unknown whether and how AMA enter KCs and why other cell types are not affected in PV. Therefore, we sought to elucidate mechanisms of cell entry, trafficking, and pathogenic action of AMA in PV. We found that PVIgGs associated with neonatal Fc receptor (FcRn) on the cell membrane, and the PVIgG-FcRn complexes entered KCs and reached mitochondria where they dissociated. The liberated AMA altered mitochondrial membrane potential, respiration, and ATP production and induced cytochrome c release, although the lack or inactivation of FcRn abolished the ability of PVIgG to reach and damage mitochondria and to cause detachment of KCs. The assays of mitochondrial functions and keratinocyte adhesion demonstrated that although the pathobiological effects of AMA on KCs are reversible, they become irreversible, leading to epidermal blistering (acantholysis), when AMA synergize with anti-Dsg antibodies. Thus, it appears that AMA enter a keratinocyte in a complex with FcRn, become liberated from the endosome in the cytosol, and are trafficked to the mitochondria, wherein they trigger pro-apoptotic events leading to shrinkage of basal KCs uniquely expressing FcRn in epidermis. During recovery, KCs extend their cytoplasmic aprons toward neighboring cells, but anti-Dsg antibodies prevent assembly of nascent desmosomes due to steric hindrance, thus rendering acantholysis irreversible. In conclusion, FcRn is a common acceptor protein for internalization of AMA and, perhaps, for PV autoantibodies to other intracellular antigens, and PV is a novel disease paradigm for investigating and elucidating the role of FcRn in this autoimmune disease and possibly other autoimmune diseases., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

With their near-universal presence in patients and ease of clinical measurement, anti-desmoglein (Dsg) antibodies serve as primary candidates for creating prognostic tools in Pemphigus vulgaris (PV). Although the desmoglein compensation hypothesis postulates a clear relationship between anti-Dsg autoantibodies and clinical phenotype in PV, recent studies have questioned the fidelity of this hypothesis as a predictor of lesion morphology. Moreover, few studies address the association of anti-Dsg antibodies to other clinical parameters such as disease phase and age at onset. Using the largest patient repository to date in PV, we present a detailed analysis of anti-desmoglein antibody profiles across a comprehensive range of dynamic (disease phase, therapy, lesion morphology) and temporal (disease duration, age at sampling, age at onset) clinical parameters. Our data highlight the non-traditional but key role of anti-Dsg1 levels in tracking disease activity. We show that declining anti-Dsg1 levels may predict progression from active phase to early remission and long-term maintenance of remission, regardless of lesion morphology. In contrast, many remittent patients have elevated levels of anti-Dsg3 without lesional activity. Furthermore, we describe a unique subset of remittent patients that develop chronic transient lesions (lasting <1 week) in the setting of elevated anti-Dsg3 levels but do not meet the consensus criteria for active phase. Re-classification of patients with transient lesions as "active" may shed new light on pathophysiological processes underlying cycles of blister formation and rapid spontaneous healing in PV. Additionally, we provide evidence for the potential attenuation of the immune response with prolonged disease duration. Our data fit into the broader effort of immunoprofiling to promote data-informed decision-making regarding diagnosis, prognosis and treatment of complex diseases.

Background: Mucocutaneous blistering is characteristic of autoimmune bullous dermatoses (AIBD). Blisters are caused by autoantibodies directed against structural components of the skin. Hence, detection of specific autoantibodies has become a hallmark for AIBD diagnosis. Studies on prevalence of AIBD autoantibodies in healthy individuals yielded contradictory results., Methods: To clarify this, samples from 7063 blood donors were tested for presence of anti-BP180-NC16A, anti-BP230 and anti-Dsg1/3 IgG by indirect immunofluorescence (IF) microscopy using a biochip., Results: Cumulative prevalence of these autoantibodies was 0.9 % (CI: 0.7-1.1 %), with anti-BP180-NC16A IgG being most prevalent. Validation of IF findings using ELISA confirmed presence of autoantibodies in 7/15 (anti-Dsg1), 6/7 (anti-Dsg3), 35/37 (anti-BP180-NC16A) and 2/3 (anti-BP230) cases. Moreover, in 16 samples, anti-BP180-NC16A autoantibody concentrations exceeded the cut-off for the diagnosis of bullous pemphigoid. Interestingly, these anti-BP180-NC16A autoantibodies from healthy individuals formed immune complexes with recombinant antigen and dose-dependently activated neutrophils in vitro. However, fine-epitope mapping within NC16A showed a different binding pattern of anti-BP180-NC16A autoantibodies from healthy individuals compared to bullous pemphigoid patients, while IgG subclasses were identical., Conclusions: Collectively, we here report a low prevalence of AIBD autoantibodies in a large cohort of healthy individuals. Furthermore, functional analysis shows differences between autoantibodies from healthy donors and AIBD patients.

Detecting serum-autoantibodies by anti-Desmoglein-1 (anti-Dsg1) and anti-Dsg3 ELISAs as well as indirect immunofluorescence (IIF) are established complementary methods to diagnose pemphigus. Whether autoantibody levels also reflect clinical disease activity is still a matter of debate, as head-to-head comparisons of ELISA values and IIF titres with clinical activity over a longer treatment period are scarce. In our retrospective study, we compared aggregated repetitive intra-patient ELISA values and IIF titres with grades of clinical disease (1 = remission, 2 = moderate activity, 3 = exacerbation) in 47 patients suffering from pemphigus vulgaris (PV, n = 36) and pemphigus foliaceus (PF, n=11). We found that anti-Dsg1 ELISA values in PF and mucocutaneous PV as well as anti-Dsg3 ELISA values in PV best reflect disease activity. IIF titres, by contrast, did not show a significant association with disease severity. From these data we conclude that ELISA index values can be a valuable tool to monitor disease in patients with pemphigus, whereas IIF titres reflect clinical activity only insufficiently.

Background: Pemphigus is an organ-specific autoimmune bullous disease., Objectives: To determine the role of regulatory B cells (Bregs) in patients with pemphigus., Methods: The frequency of the occurrence of CD19(+) CD24(hi) CD38(hi) Bregs was detected from 34 patients with pemphigus and 20 healthy controls. Interleukin (IL)-10 secretion was processed after stimulating B cells. Specific antidesmoglein antibody (Ab) titres and their subclasses were also measured. Ab response and cytokine production from peripheral blood mononuclear cells (PBMCs) with or without Bregs were analysed., Results: The number of Bregs was significantly increased in patients with pemphigus compared with healthy controls (15 ± 7% vs. 9 ± 3%; P < 0·01) and the proportion of Bregs in the active groups (newly diagnosed and chronic active patients) was significantly higher than in remittent individuals (16 ± 7% vs. 13 ± 8%; P = 0·04). The IL-10-producing B cells were significantly increased upon stimulation both in patients and in healthy controls. However, the increase ratio of IL-10-producing B cells between short- and long-term stimulation was significantly lower in patients with pemphigus (1·0-fold vs. 2·6-fold increase in control group; P < 0·01). Strikingly, Bregs from the controls were able to suppress interferon (IFN)-γ expression and T helper cell 1 (Th1) immune response (26% inhibition rate), while the suppressive function of Bregs from patients with pemphigus was significantly decreased (9% inhibition rate). There was no difference in Ab levels from PBMCs with or without Bregs after stimulation., Conclusions: Bregs in patients with pemphigus are elevated but with defective regulatory function on Th1 cells., (© 2014 British Association of Dermatologists.)

Pemphigus herpetiformis is one of the less common forms of pemphigus, first introduced by Jabłońska and colleagues in 1975. This autoimmune bullous disease combines the clinical features of dermatitis herpetiformis and the immunologic characteristics of pemphigus. The target autoantigen is usually desmoglein 1 (or less frequently desmoglein 3), although recently it has become increasingly obvious that patients with pemphigus herpetiformis also demonstrate autoantibodies against desmocollin. Here, we summarize reported cases of pemphigus herpetiformis and describe current knowledge considering epidemiology, clinical manifestations, histologic findings, immunopathology, pathophysiologic concepts, associated diseases, and treatment of this rare disorder., (Copyright © 2013 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Importance: Recently, the clinical pemphigus disease activity indexes of Pemphigus Disease Area Index (PDAI), Autoimmune Bullous Skin Disorder Intensity Score (ABSIS), and Pemphigus Vulgaris Activity Score (PVAS) were validated to correlate with physician global assessment. The antidesmoglein (anti-Dsg) autoantibodies are known to correlate mostly with pemphigus disease activity. The correlation between these indexes and anti-Dsg1 and anti-Dsg3 enzyme-linked immunosorbent assay values has not been previously evaluated., Objectives: To evaluate the PDAI, ABSIS, and PVAS in a large number of patients with pemphigus vulgaris and to compare the interrater reliability of these indexes and the convergent validity according to anti-Dsg values., Design, Setting, and Participants: A cross-sectional study was performed in 2012 in a referral university center for autoimmune bullous diseases. One hundred patients with confirmed diagnoses of pemphigus vulgaris and clinical pemphigus lesions (mean [SD] age, 43.3 [1.7] years; age range, 14-77 years; female-male ratio, 1:3) were studied. Three dermatologists familiar with immunobullous diseases and the indexes rated the patients., Interventions: All 100 patients were evaluated with the PDAI, ABSIS, and PVAS. Three dermatologists independently rated all 3 indexes for each of the patients on the same day. Serum anti-Dsg1 and anti-Dsg3 enzyme-linked immunosorbent assay values were measured simultaneously., Main Outcomes and Measures: Analyses of interrater reliabilities, convergent validities according to anti-Dsg titers, correlation between the distribution and types of lesions with disease activity, predictors of higher titers of antibody (multiple regression analysis), and cutoff values of measures for 2 titers of anti-Dsg with optimal area under the curve, sensitivity, and specificity were performed., Results: The interrater reliabilities were highest for the PDAI, followed by the ABSIS and the PVAS (intraclass correlation coefficients of 0.98 [95% CI, 0.97-0.98], 0.97 [95% CI, 0.96-0.98], and 0.93 [95% CI, 0.90-0.95], respectively). The convergent validity was highest for the PDAI, followed by the PVAS and the ABSIS (Spearman ρ = 0.67, 0.52, and 0.33, respectively). Head, neck, and trunk involvement were predictors of higher titers of anti-Dsg1., Conclusions and Relevance: Among the 3 studied indexes, the PDAI had the highest validity and is recommended for use in multicenter studies for rare diseases, such as pemphigus vulgaris.

Autoantibodies from patients suffering from the autoimmune blistering skin disease pemphigus can be applied as tools to study desmosomal adhesion. These autoantibodies targeting the desmosomal cadherins desmoglein (Dsg) 1 and Dsg3 cause disruption of desmosomes and loss of intercellular cohesion. Although pemphigus autoantibodies were initially proposed to sterically hinder desmosomes, many groups have shown that they activate signaling pathways which cause disruption of desmosomes and loss of intercellular cohesion by uncoupling the desmosomal plaque from the intermediate filament cytoskeleton and/or by interfering with desmosome turnover. These studies demonstrate that desmogleins serve as receptor molecules to transmit outside-in signaling and demonstrate that desmosomal cadherins have functions in addition to their adhesive properties. Two central molecules regulating cytoskeletal anchorage and desmosome turnover are p38MAPK and PKC. As cytoskeletal uncoupling in turn enhances Dsg3 depletion from desmosomes, both mechanisms reinforce one another in a vicious cycle that compromise the integrity and number of desmosomes.

Pemphigus includes a group of autoimmune bullous diseases with intraepithelial lesions involving the skin and Malpighian mucous membranes. Pemphigus vulgaris (PV), the most frequent and representative form of the group, is a prototypical organ-specific human autoimmune disorder with a poor prognosis in the absence of medical treatment. The pathomechanism of PV hinges on autoantibodies damaging cell-cell cohesion and leading to cell-cell detachment (acantholysis) of the epidermis and Malpighian mucosae (mainly oral mucosa). A controversy exists about which subset of autoantibodies is primarily pathogenic: the desmoglein-reactive antibodies or those directed against the acetylcholine receptors of the keratinocyte membrane. The onset and course of PV depend on a variable interaction between predisposing and inducing factors. Genetic predisposition has a complex polygenic basis, involving multiple genetic loci; however, the genetic background alone ("the soil"), although essential, is not by itself sufficient to initiate the autoimmune mechanism, as proven by the reports of PV in only one of two monozygotic twins and in only two of three siblings with an identical PV-prone haplotype. The intervention of inducing or triggering environmental factors ("the seed") seems to be crucial to set off the disease. The precipitating factors are many and various, most of them directly originating from the environment (eg, drug intake, viral infections, physical agents, contact allergens, diet), others being endogenous (eg, emotional stress, hormonal disorders) but somehow linked with the subject's lifestyle. As to certain drugs, their potential of provoking acantholysis may be implemented by their interfering with the keratinocyte membrane biochemistry (biochemical acantholysis) and/or with the immune balance (immunologic acantholysis). Viral infections, especially the herpetic ones, may trigger the outbreak of PV or simply complicate its clinical course. The precipitating effect might be due to interferons and other cytokines released by the host as a consequence of the viral attack, which overactivate the immune response. Inductions of PV by physical agents (ultraviolet or ionizing radiation, thermal or electrical burns, surgery and cosmetic procedures), contact allergens (in particular, organophosphate pesticides), dietary factors (eg, garlic, leek, onion, black pepper, red chili pepper, red wine, tea), and emotional stress are rare, but well-documented events. The possible intervention of the environment in the outbreak of PV has been overlooked in the past, but nowadays clinicians perceive it more frequently. The assumption that genetic factors alone are not sufficient to cause the outbreak of the disease, inevitably instills the idea that PV may not occur spontaneously, but always results from an interaction between an individual predisposing genetic background and environmental precipitating factors, often concealed or apparently harmless., (Copyright © 2013. Published by Elsevier Inc.)

Hypothesis/objectives: To describe the clinical, histological and immunological findings of an equine case of pemphigus vulgaris, including the demonstration of antidesmoglein (anti-Dsg) autoantibodies., Case Report: The diagnosis of pemphigus vulgaris was confirmed in a 9-year-old Welsh pony stallion with both direct and indirect immunofluorescence and immunoprecipitation studies, the latter identifying circulating anti-Dsg3 IgG. Treatment with immunosuppressive medications was initiated. Lesions were seen in the perineal area, sheath, mane, tail, eyelids, coronary bands and mucosa of the mouth and oesophagus. Initial corticosteroid treatment improved the clinical signs, but the onset of laminitis necessitated a reduction in dosage, which was associated with a recurrence of lesions and development of oral ulcers. A corneal ulcer developed after 60 days of treatment. Despite treatment with azathioprine, gold salts and dapsone, the disease progressed and the pony was euthanized. Postmortem examination showed additional lesions of the cardia of the stomach., Conclusions and Clinical Importance: Pemphigus vulgaris is rarely diagnosed in equids. We describe a case that was substantiated by the demonstration of anti-Dsg3 IgG. Response to treatment was poor, with the best response to high doses of prednisolone. Equine pemphigus vulgaris is likely to carry a poor prognosis and if there is no response to treatment, humane euthanasia is warranted., (© 2013 The Authors. Veterinary Dermatology © 2013 ESVD and ACVD.)

Pemphigus is a severe blistering condition of the skin and mucosa caused by autoantibodies directed against desmogleins, which are a type of keratinocyte adhesion protein. B cell depletion by rituximab has short-term efficacy against pemphigus. We aimed to assess the long-term course of pemphigus patients after B cell depletion and to understand the immunological mechanisms that mediate long-lasting remissions. We evaluated the clinical course of 22 pemphigus patients treated with rituximab after a 79-month median follow-up and compared the anti-desmoglein B cell response and B and T lymphocyte subpopulations and repertoire between patients who achieved complete remission (CR) and those who had incomplete remission (IR). Thirteen patients (59%) experienced CR during the study, including 10 patients off treatment and 3 patients with prednisone doses <10 mg/day; 9 patients had IR. A marked increase was observed in the ratio of CD19(+)CD27(-) naïve B cells to CD19(+)CD27(+) memory B cells. Indeed, patients in CR had a fourfold higher number of transitional B cells and interleukin-10-secreting regulatory B cells than those in IR. Furthermore, CR was associated with modification of the initial B cell repertoire and the disappearance of desmoglein-specific circulating immunoglobulin G-positive (IgG(+)) B lymphocytes, whereas a skewed B cell repertoire was observed in patients in IR. Thus, a blockage of B cell maturation, a prolonged repopulation with naïve B cells, and a delayed reappearance of memory B cells, which resulted in the disappearance of circulating desmoglein-specific IgG(+) B lymphocytes, contribute to the long-lasting effectiveness of rituximab for treating pemphigus.

Background: Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are potentially fatal blistering diseases caused by autoantibodies targeting desmoglein (Dsg) adhesion proteins. Previous studies have shown an IgG4 > IgG1 predominance of anti-Dsg antibodies in pemphigus; however, no studies have examined total serum IgG4 levels in pemphigus. IgG4 is induced by chronic antigen stimulation, which could occur with persistent skin blistering and potentially elevate the total serum IgG4 relative to other IgG subclasses in patients with pemphigus., Objectives: The primary aim of the study was to quantitate total and Dsg-specific IgG subclasses in patients with pemphigus., Methods: IgG subclasses and Dsg-specific IgG1 and IgG4 were quantitated in patients with PV and PF, and in sera from age-matched controls using a subclass enzyme-linked immunosorbent assay. The effectiveness of IgG4 depletion in blocking IgG pathogenicity in PV was determined using a keratinocyte dissociation assay., Results: Dsg-specific antibodies comprised a median of 7·1% and 4·2% of total IgG4 in patients with PV and PF, respectively, with eightfold and fourfold enrichment in IgG4 vs. IgG1. Total serum IgG4, but not other IgG subclasses, was enriched in patients with PV and PF compared with age-matched controls (P = 0·004 and P = 0·005, respectively). IgG4 depletion of PV sera reduced pathogenicity in a keratinocyte dissociation assay and showed that affinity-purified IgG4 is more pathogenic than other serum IgG fractions., Conclusions: Dsg-specific autoantibodies are significantly enriched in IgG4, which may explain the enrichment of total serum IgG4 in some patients with pemphigus. By preferentially targeting autoimmune rather than beneficial immune antibodies, IgG4-targeted therapies may offer safer treatment options for pemphigus., (© 2012 The Authors. BJD © 2012 British Association of Dermatologists 2012.)

It is well established that autoantibodies against desmoglein 3 and desmoglein 1 (Dsg1) are relevant in the pathogenesis of pemphigus vulgaris and pemphigus foliaceus, including its endemic form fogo selvagem (FS). Isolated reports have shown that in certain patients with these diseases, autoantibodies against other desmosomal cadherins and E-cadherin may also be present. The goal of this investigation was to determine whether FS patients and normal individuals living in endemic areas possess autoantibodies against other desmosomal cadherins and E-cadherin. By testing a large number of FS and endemic control sera by ELISA, we found a consistent and specific autoantibody response against Dsg1 and other keratinocyte cadherins in these individuals, which is quite different from healthy individuals from the United States (US controls). Overall, the highest correlations among the autoantibody responses tested were in the endemic controls, followed by FS patients, and lowest in the US controls. These findings suggest that multiple, perhaps cross-reactive, keratinocyte cadherins are recognized by FS patients and endemic controls.

Background: Hailey-Hailey disease (HHD) is a rare hereditary disease in which the genetic defect is characterized by mutation in the ATP2C1 gene coding for a transmembrane calcium pump. It is generally considered a non-immunologic acantholytic dermatosis in which direct and indirect immunofluorescence studies are negative, unlike in autoimmune pemphigus., Patients and Methods: We describe a case of HHD associated with antidesmoglein antibodies in a 53-year-old woman. The clinical symptoms and histology were typical of HHD. Antidesmoglein antibody tests were positive on several occasions and a difference was found between the two types of Elisa test performed (positive with the MBL kit, negative with the Euroimmun kit)., Discussion: The positive result for desmoglein antibodies could be due to unmasking of antigens by the mechanism of acantholysis. The specificity of the main desmoglein Elisa tests also requires discussion., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

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.

Pemphigus vulgaris (PV) is a Th2-dominant autoimmune skin disease. We showed that indeed active PV patients had a biased Th2 response and specific IgG4 autoantibodies were dominant. To further investigate the role of antigen-specific Th2 cells in the regulation of pathogenic Dsg3-IgG antibody production, we used recombined Dsg3 protein to immunize wild-type C57BL/6 mice with aluminum hydroxide or complete Freund's adjuvant as adjuvant. CD4(+) T cells from Dsg3-immunized mice were adoptively transferred into TCR-β chain deficient mice. The transferred CD4(+) T cells were readily seen in the peripheral blood and spleen, and interacted with B cells, resulting in B-cell activation. Furthermore, transferred CD4(+) T cells from mice immunized with Dsg3 plus Alum with Th2 phenotype were able to render unprimed B cells to secrete Dsg3-specific IgG1 antibody in vivo. Taken together, these results provide the first demonstration of direct role of Dsg3-reactive CD4(+) T (Th2) cells in the regulation of pathologic anti-Dsg3 antibody production.

Background:   It has been previously shown in a relatively small group of patients that a combination of immunoadsorption (IA) and rituximab with daily use of high-dose oral corticosteroids and azathioprine/mycophenolate mofetil may induce a rapid and durable remission in severe, treatment-resistant pemphigus., Objectives: To achieve a more rapid reduction of serum autoantibody levels by a more frequent use of IA in the initial phase of treatment and to reduce the number of severe adverse events of continuous oral corticosteroid therapy by switching to pulsed intravenous applications., Methods: Twenty-three consecutive patients with severe pemphigus were included. IA was performed at initially 3- and later 4-week intervals until lesions healed by 90%; 1000mg rituximab was given at weeks 1 and 3, and intravenous dexamethasone pulses were administered at first every 3weeks and then at increasing intervals in addition to daily azathioprine/mycophenolate mofetil., Results: Along with a fast and durable decline of circulating autoantibody levels, all patients showed improvement of pemphigus lesions within the first weeks of therapy and long-term complete remission was induced in 19 (83%) patients. In the remaining four patients, one (4%) minimal disease and three (13%) partial remissions were observed. Over the long-term follow-up of 11-43 (mean 29) months, six (26%) patients had a recurrence and in two (9%) patients, severe adverse events occurred., Conclusions: This novel protocol treatment induces a fast and long-term remission in severe pemphigus and seems to offer an improved side-effect profile compared with daily use of corticosteroids., (© 2011 The Authors. BJD © 2011 British Association of Dermatologists.)