A pathogenic role for IgE in autoimmunity: bullous pemphigoid IgE reproduces the early phase of lesion development in human skin grafted to nu/nu mice

Anti-BP230 IgE autoantibodies in bullous pemphigoid intraindividually correlate with disease activity

BACKGROUND

Bullous pemphigoid (BP), the most common subepidermal autoimmune blistering disease, is classically defined by the presence of IgG autoantibodies directed against the hemidesmosomal proteins BP180 (type XVII collagen) and BP230 and the predominance of skin lesions. Several studies have addressed the role of anti-BP180 IgE in patients and experimental models, while data on anti-BP230 IgE are scarce.

OBJECTIVE

To assess anti-BP230 IgE level by ELISA in BP sera and to correlate it with disease severity and clinical characteristics.

METHODS

BP sera underwent anti-BP230 IgE ELISA and Western blotting against human BP230 fragments.

RESULTS

We demonstrate that 36/154 (23%) of BP sera were positive for anti-BP230 IgE. Anti-BP230 IgE levels had no correlation with clinical phenotype or disease activity per se. Interestingly, anti-BP230 IgE was significantly associated with disease activity within individuals during the course of the disease. Additionally, anti-BP230 IgE and total IgE levels showed a significant correlation. Notably, anti-BP230 IgG correlated interindividually with disease activity. By Western blotting, the C-terminal domain of BP230 fragments (C2; amino acids 2024-2349 and C3; amino acids 2326-2649), provided the best serological assay for anti-BP230 IgE detection.

CONCLUSION

As a complementary tool, IgE immunoblotting is recommended to obtain an optimal serological diagnosis, particularly in patients with severe disease without IgG reactivity by BP180- or BP230-specific ELISA. Although the detection of serum anti-BP230 IgE is not of major diagnostic significance, it may be relevant for therapeutic decisions, e.g., for anti-IgE-directed treatment, which has been successfully used in case series of BP.

Single-Cell Profiling Unveils the Inflammatory Heterogeneity within Cutaneous Lesions of Bullous Pemphigoid

Bullous pemphigoid (BP) is a subepidermal blistering skin disease with a complex pathogenesis involving various immune cells. However, the transcriptional features of these cells remain poorly defined. In this study, we constructed a comprehensive and single-cell resolution atlas of various immune cells within BP skin lesions through integrative single-cell analysis, flow cytometry, and multiplex immunohistochemistry. We observed prominent expansion and transcriptional changes in mast cells, macrophages, basophils, and neutrophils within BP lesions. Mast cells within the lesions adopted an active state and exhibited an elevated capacity for producing proinflammatory mediators. We observed an imbalance of macrophages/dendritic cells within BP lesions. Two macrophage subpopulations (NLRP3+ and C1q+) with distinct transcriptional profiles were identified and upregulated effector programs. T-peripheral helper-like T helper 2 cells were expanded in skin lesions and peripheral blood of patients with BP and were capable of promoting B-cell responses. In addition, we observed clonally expanded granzyme B-positive CD8+ T cells within BP lesions. Chemokine receptor mapping revealed the potential roles of macrophages and mast cells in recruiting pathogenic immune cells and underlying mechanisms within BP lesions. Thus, this study reveals key immune pathogenic features of BP lesions, thereby providing valuable insights for potential therapeutic interventions in this disease.

The Eotaxin-1/CCR3 Axis and Matrix Metalloproteinase-9 Are Critical in Anti-NC16A IgE-Induced Bullous Pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune bullous skin disease of humans and is characterized by eosinophilic inflammation and circulating and tissue-bound IgG and IgE autoantibodies directed against two hemidesmosomal proteins: BP180 and BP230. The noncollagenous 16A domain (NC16A) of BP180 has been found to contain major epitopes recognized by autoantibodies in BP. We recently established the pathogenicity of anti-NC16A IgE through passive transfer of patient-derived autoantibodies to double-humanized mice that express the human high-affinity IgE receptor, FcεRI, and human NC16A domain (FcεRI/NC16A). In this model, anti-NC16A IgEs recruit eosinophils to mediate tissue injury and clinical disease in FcεRI/NC16A mice. The objective of this study was to characterize the molecular and cellular events that underlie eosinophil recruitment and eosinophil-dependent tissue injury in anti-NC16A IgE-induced BP. We show that anti-NC16A IgEs significantly increase levels of key eosinophil chemoattractants, eotaxin-1 and eotaxin-2, as well as the proteolytic enzyme matrix metalloproteinase-9 (MMP-9) in the lesional skin of FcεRI/NC16A mice. Importantly, neutralization of eotaxin-1, but not eotaxin-2, and blockade of the main eotaxin receptor, CCR3, drastically reduce anti-NC16A IgE-induced disease activity. We further show that anti-NC16A IgE/NC16A immune complexes induce the release of MMP-9 from eosinophils, and that MMP-9-deficient mice are resistant to anti-NC16A IgE-induced BP. Lastly, we find significantly increased levels of eotaxin-1, eotaxin-2, and MMP-9 in blister fluids of BP patients. Taken together, this study establishes the eotaxin-1/CCR3 axis and MMP-9 as key players in anti-NC16A IgE-induced BP and candidate therapeutic targets for future drug development and testing.

Targeting type 2 inflammation in bullous pemphigoid: current and emerging therapeutic approaches

Bullous pemphigoid (BP) is one of the most common autoimmune bullous diseases and mainly affects an elderly population with multi-morbidity. Due to the frailty of many BP patients, existing treatment options are limited. The blisters associated with BP result from IgG and IgE autoantibodies binding to the central components of hemidesmosome, BP180, and BP230, stimulating a destructive inflammatory process. The known characteristic features of BP, such as intense pruritus, urticarial prodrome, peripheral eosinophilia, elevated IgE, as well as recent expanding evidence from in vitro and in vivo studies implicate type 2 inflammation as an important driver of BP pathogenesis. Type 2 inflammation is an inflammatory pathway involving a subset of CD4+ T cells that secrete IL-4, IL-5, and IL-13, IgE-secreting B cells, and granulocytes, such as eosinophils, mast cells, and basophils. It is believed that effectors in type 2 inflammation may serve as novel and effective treatment targets for BP. This review focuses on recent understandings of BP pathogenesis with a particular emphasis on the role of type 2 inflammation. We summarize current clinical evidence of using rituximab (B-cell depletion), omalizumab (anti-IgE antibody), and dupilumab (anti-IL-4/13 antibody) in the treatment of BP. The latest advances in emerging targeted therapeutic approaches for BP treatment are also discussed.

Research progress of omalizumab in the treatment of bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease associated with anti-BP180 and anti-BP230 antibodies. The pathogenic action mechanism of immunoglobulin E (IgE) antibodies in BP has been studied since the 1970s, and IgE antibodies have gradually been confirmed as being important in BP; therefore, anti-IgE therapy may be a new option for the treatment of BP. Omalizumab, as an IgE monoclonal antibody, has been increasingly used clinically to treat BP in recent years. Here, we collected 35 papers investigating omalizumab for BP treatment in a total of 83 patients, and the vast majority of patients showed varying degrees of improvement after treatment, except for a small number of patients with poor clinical outcomes. The patients were then divided into three groups according to dosing frequency and number of doses. Statistical analysis indicated that dosing frequency had little effect on clinical efficacy. While the groups with different numbers of doses were evaluated, the results concluded that clinical efficacy was affected by the number of doses, but there was no positive correlation between the number of doses and clinical efficacy.

Elevated levels of sCD48 are inversely correlated with markers of disease activity in bullous pemphigoid

sCD48 is elevated in diseases characterized by IgE and eosinophilia. Thus, serum levels sCD48 were evaluated in relation to clinical characteristics of Bullous pemphigoid (BP) patients. sCD48 levels were determined by ELISA in sera from 26 patients with classic BP and 26 healthy controls. Disease severity scores, differential blood counts, and circulating autoantibody levels were obtained. A correlation analysis was performed to establish relationships between sCD48 and clinical and laboratory markers of disease severity. Overall, circulating levels of sCD48 were significantly elevated in BP patients; however, when stratified based on disease severity, patients with mild-moderate disease had higher levels of sCD48 than those with severe disease. A Spearman's correlation analysis identified an inverse relationship between sCD48 and disease activity, serum BP180 IgE and peripheral eosinophil numbers. Further studies are needed to determine the pathologic relevance of these findings.

Understanding CD4+ T cells in autoimmune bullous diseases

Autoimmune bullous diseases (AIBDs) are a group of life-threatening blistering diseases caused by autoantibodies that target proteins in the skin and mucosa. Autoantibodies are the most important mediator in the pathogenesis of AIBDs, and various immune mechanisms contribute to the production of these pathogenic autoantibodies. Recently, significant progress has been made in understanding how CD4⁺ T cells drive autoantibody production in these diseases. Here, we review the critical role of CD4⁺ T cells in the production of pathogenic autoantibodies for the initiation and perpetuation of humoral response in AIBDs. To gain an in-depth understanding of CD4⁺ T-cell pathogenicity, antigen specificity, and mechanisms of immune tolerance, this review covers comprehensive mouse and human studies of pemphigus and bullous pemphigoid. Further exploration of pathogenic CD4⁺ T cells will potentially provide immune targets for improved treatment of AIBDs.

Clinical effect of omalizumab as an adjuvant treatment to rituximab in patient with refractory bullous pemphigoid

Patients with refractory bullous pemphigoid (BP) achieve remission after rituximab treatment but require high-dose systemic corticosteroids until the remission. The aim of this retrospective study was to examine the clinical efficacy of omalizumab as an adjuvant treatment to rituximab in patients with refractory BP. Patients with BP receiving treatment with either rituximab monotherapy or rituximab plus omalizumab were considered for the study. The total dose of corticosteroids received for 60 days after administration of rituximab, mortality and relapse rates, and median time to relapse were also investigated. Of 49 patients included in the study, 25 received rituximab monotherapy and 17 received the combination therapy with rituximab and omalizumab. The rituximab plus omalizumab group showed shorter time to disease control with minimal treatment (15 days vs. 67.5 days, p < 0.001) and lower corticosteroid dose for 60 days after administration of rituximab (698.4 mg vs. 1087.4 mg of methylprednisolone, p < 0.001) compared to the rituximab monotherapy group. The results of this study suggest that combination therapy with rituximab and omalizumab can achieve disease control status faster than the rituximab monotherapy, reducing the total dose of corticosteroids.

Omalizumab as a corticosteroid-sparing agent in the treatment of bullous pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune blistering skin disease, characterized by the development of autoantibodies against hemidesmosomal components BP180 and BP230. The mainstay of therapy is topical and systemic corticosteroids (CS) and immunosuppressors. As this pathology mainly involves the elderly, subjects often have numerous comorbidities that influence the clinical management. Omalizumab is a recombinant humanized monoclonal anti-IgE antibody which has recently emerged as a promising treatment for BP in patients for whom CS are contraindicated or conventional treatments have failed to control the disease. For this study, we selected five patients who presented with corticosteroid-dependent BP with a contraindication to the use of other immunosuppressive treatments. The objectives of our study were to evaluate the effectiveness of omalizumab in controlling BP and allowing to decrease the dosage of systemic CS, assessing the effects of omalizumab on the clinical manifestations and the titers of circulating anti-BP180 and BP230 antibodies, IgE and eosinophils. A reduction in the dose of systemic CS was possible in 100% of the patients and complete resolution of the clinical picture was seen in 100% for skin lesions and in 40% for pruritus. A reduction of circulating IgE was found in 40%, anti-BP180 and BP230 IgGs were decreased in 60% and eosinophils in 80%.

Bullous pemphigoid-What do we know about the most recent therapies?

INTRODUCTION

Bullous pemphigoid (BP) is the most common subtype of autoimmune blistering diseases that primarily affects the elderly and is classically defined by the presence of IgG and/or complement C3 against the BP180 and BP230 hemidesmosome proteins. However, most recent studies have introduced the role of specific eosinophil receptors and chemokine mediators in the pathogenesis of BP which are helpful in identifying new targets for future treatments.

AREAS COVERED

This review will focus on the involvement of eosinophils in BP, including the processes that lead to their recruitment, activation, and regulation. Subsequently, covering new therapeutic options in relation to the role of eosinophils. Eotaxin enhances the recruitment of eosinophils in BP, with CCR3 chemoreceptor that is expressed on eosinophils being identified as a key binding site for eotaxin-1. The pathogenic role of IgE and IL-4 in BP is corroborated by successful treatments with Omalizumab and Dupilumab, respectively. IL-5, IL-17 and IL-23 inhibitors may be effective given their roles in promoting eosinophilia.

EXPERT OPINION

Further research into inhibitors of eotaxin, IL-4, IL-5, IL-17, IL-23, CCR3, and specific complement factors are warranted as preliminary studies have largely identified success in treating BP with these agents. Learning from novel treatments for other IgG-mediated autoimmune diseases may be beneficial.

The relevance of complement in pemphigoid diseases: A critical appraisal

Pemphigoid diseases are autoimmune chronic inflammatory skin diseases, which are characterized by blistering of the skin and/or mucous membranes, and circulating and tissue-bound autoantibodies. The well-established pathomechanisms comprise autoantibodies targeting various structural proteins located at the dermal-epidermal junction, leading to complement factor binding and activation. Several effector cells are thus attracted and activated, which in turn inflict characteristic tissue damage and subepidermal blistering. Moreover, the detection of linear complement deposits in the skin is a diagnostic hallmark of all pemphigoid diseases. However, recent studies showed that blistering might also occur independently of complement. This review reassesses the importance of complement in pemphigoid diseases based on current research by contrasting and contextualizing data from in vitro, murine and human studies.

Insights Into the Pathogenesis of Bullous Pemphigoid: The Role of Complement-Independent Mechanisms

Bullous pemphigoid is an autoimmune blistering disease caused by autoantibodies targeting BP180 and BP230. While deposits of IgG and/or complement along the epidermal basement membrane are typically seen suggesting complement -mediated pathogenesis, several recent lines of evidence point towards complement-independent pathways contributing to tissue damage and subepidermal blister formation. Notable pathways include macropinocytosis of IgG-BP180 complexes resulting in depletion of cellular BP180, direct induction of pro-inflammatory cytokines from keratinocytes, as well as IgE autoantibody- and eosinophil-mediated effects. We review these mechanisms which open new perspectives on novel targeted treatment modalities.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.

A Review of the Immunologic Pathways Involved in Bullous Pemphigoid and Novel Therapeutic Targets

Bullous pemphigoid (BP) is a rare, chronic antibody-mediated autoimmune blistering disease primarily affecting the elderly, with an age of onset over 60. Current treatment options are limited and involve the use of corticosteroids and immunosuppressants, but their long-term use is associated with significant morbidity and mortality. In Japan, human intravenous immunoglobin is approved for the treatment of corticosteroid-refractory BP. However, no treatment option is approved by the Food and Drug Administration for the management of BP. Therefore, developing effective therapies free of debilitating side effects is imperative. In this review, we summarize the main immunologic pathways involved in the pathogenesis of BP, with an emphasis on the role of eosinophils, immunoglobulins, cytokines such as the interleukin (IL)-4 and IL-5, and complements. We further discuss the latest advances with novel therapeutic targets tested for the management of BP. Ongoing efforts are needed to run well-designed controlled trials and test the efficacy and safety of investigational drugs while providing much-needed access to these medications for refractory patients who will not otherwise be able to afford them as off-label prescriptions.

Mast cell‐deficient mice Mcpt5Cre/Dicer fl/fl redefine the role of mast cells in experimental bullous pemphigoid

Background

Bullous pemphigoid (BP) is the most frequent autoimmune blistering disease of the skin affecting the elderly. BP is immunopathologically characterized by autoantibodies against BP180 and BP230. With the growing evidence of cell‐mediated autoimmunity in the pathogenesis of BP, it still remains unclear whether mast cells (MCs) are involved, due to conflicting data obtained from Kit‐dependent MC‐deficient mouse models.

Objectives

To clarify the role of MCs in experimental BP; the dynamics in cutaneous MC numbers, associated immune cells and the development of disease in Kit‐independent MC‐deficient mouse model.

Methods

Employing a recently established murine adult passive transfer model of BP induced by the transfer of pathogenic immunoglobulin G (IgG), lesional skin biopsies were investigated histologically and immunohistochemically for the time‐dependent MC accumulation and dermal infiltration.

Results

The numbers of cutaneous MCs increased following the induction of BP, in part, maintained by MC proliferation. Numbers of T cells, neutrophils and eosinophils in the skin also increased after BP induction, with eosinophils showing a preferential co‐localization with MCs. Furthermore, clinical disease manifestation in MC‐deficient Mcpt5Cre/Dicer^fl/fl mice remained unchanged compared to MC‐sufficient Dicer^fl/fl mice. The composition of the immune cell infiltration including as T cells, neutrophils and eosinophils was largely unaffected by the absence of MCs.

Conclusion

MCs do not play a pivotal role in the pathogenesis of passive IgG‐transfer mediated BP model. Their increase in number may be a bystander effect following tissue injury. We therefore suggest caution regarding the selection of MCs as sole targets for the development of novel drugs for BP.

Immunopathology and Immunotherapy of Inflammatory Skin Diseases

Recently, there have been impressive advancements in understanding of the immune mechanisms underlying cutaneous inflammatory diseases. To understand these diseases on a deeper level and clarify the therapeutic targets more precisely, numerous studies including in vitro experiments, animal models, and clinical trials have been conducted. This has resulted in a paradigm shift from non-specific suppression of the immune system to selective, targeted immunotherapies. These approaches target the molecular pathways and cytokines responsible for generating inflammatory conditions and reinforcing feedback mechanisms to aggravate inflammation. Among the numerous types of skin inflammation, psoriasis and atopic dermatitis (AD) are common chronic cutaneous inflammatory diseases. Psoriasis is a IL-17–mediated disease driven by IL-23, while AD is predominantly mediated by Th2 immunity. Autoimmune bullous diseases are autoantibody-mediated blistering disorders, including pemphigus and bullous pemphigoid. Alopecia areata is an organ-specific autoimmune disease mediated by CD8⁺ T-cells that targets hair follicles. This review will give an updated, comprehensive summary of the pathophysiology and immune mechanisms of inflammatory skin diseases. Moreover, the therapeutic potential of current and upcoming immunotherapies will be discussed.

Mouse Models for Human Skin Transplantation: A Systematic Review

Immunodeficient mouse models with human skin xenografts have been developed in the past decades to study different conditions of the skin. Features such as follow-up period and size of the graft are of different relevance depending on the purpose of an investigation. The aim of this study is to analyze the different mouse models grafted with human skin. A systematic review of the literature was performed in line with the PRISMA statement using MEDLINE/PubMed databases from January 1970 to June 2020. Articles describing human skin grafted onto mice were included. Animal models other than mice, skin substitutes, bioengineered skin, postmortem or fetal skin, and duplicated studies were excluded. The mouse strain, origin of human skin, graft dimensions, follow-up of the skin graft, and goals of the study were analyzed. Ninety-one models were included in the final review. Five different applications were found: physiology of the skin (25 models, mean human skin graft size 1.43 cm2 and follow-up 72.92 days), immunology and graft rejection (17 models, mean human skin graft size 1.34 cm2 and follow-up 86 days), carcinogenesis (9 models, mean human skin graft size 1.98 cm2 and follow-up 253 days), skin diseases (25 models, mean human skin graft size 1.55 cm2 and follow-up 86.48 days), and would healing/scars (15 models, mean human skin graft size 2.54 cm2 and follow-up 129 days). The follow-up period was longer in carcinogenesis models (253 ± 233.73 days), and the skin graft size was bigger in wound healing applications (2.54 ± 3.08 cm2). Depending on the research application, different models are suggested. Careful consideration regarding graft size, follow-up, immunosuppression, and costs should be analyzed and compared before choosing any of these mouse models. To our knowledge, this is the first systematic review of mouse models with human skin transplantation.

Clinical characteristics of pruritus in patients with bullous pemphigoid: a preliminary questionnaire-based study

Introduction

Bullous pemphigoid (BP) is the most common autoimmune blistering disease. Although pruritus is a leading symptom in BP, its specific characteristics have not been explored.

Aim

To determine the itch characteristics in newly diagnosed BP patients by using the Questionnaire of Descriptive Assessment of Pruritus and visual analogue scale (VAS) and to correlate itch with disease severity.

Material and methods

The study included 32 patients with BP (mean age: 75.4 ±12.2 years; 20 women, 12 men), who filled in the questionnaire. Bullous Pemphigoid Disease Area Index (BPDAI) was assessed.

Results

In 78.1% of BP patients pruritus occurred at least once daily. Pruritus was most frequent in the evening and at night and frequently persisted for more than 10 min in more than a half of patients (long itch episodes). Aggravating factors were sweating (50.0%), heat (59.4%) and stress (46.9%), but the major relieving factor was cold (34.4%). Itch intensity in BP was assessed as moderate (mean VAS score: 5.8 points) and did not correlate with disease severity (BPDAI). BP patients declared difficulties caused by pruritus: falling asleep (53.1%) and awakening at night (50%).

Conclusions

This study provided detailed characteristics in BP patients confirming that pruritus is classified as an important troublesome symptom. Therefore there is a need to search for therapeutic solutions.

The pathogenesis of bullous skin diseases

Bullous skin diseases are a group of dermatoses characterized by blisters and bullae in the skin and mucous membranes. The etiology and pathogenesis of bullous skin diseases are not completely clear. The most common are pemphigus and bullous pemphigoid (BP). Autoantibodies play critical roles in their pathogenesis. Abnormalities in the adhesion between keratinocytes in patients with pemphigus leads to acantholysis and formation of intra-epidermal blisters. Anti-desmoglein autoantibodies are present both in the circulation and skin lesions of patients with pemphigus. The deficient adhesion of keratinocytes to the basement membrane in BP patients gives rise to subepidermal blisters. Autoantibodies against the components of hemidesmosome can be detected in BP patients. Many novel therapeutics based on knowledge of the pathogenesis have emerged in recent years.

The Intersection of IgE Autoantibodies and Eosinophilia in the Pathogenesis of Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized by autoantibodies targeting cellular adhesion molecules. While IgE autoantibodies are occasionally reported in other autoimmune blistering diseases, BP is unique in that most BP patients develop an IgE autoantibody response. It is not known why BP patients develop self-reactive IgE and the precise role of IgE in BP pathogenesis is not fully understood. However, clinical evidence suggests an association between elevated IgE antibodies and eosinophilia in BP patients. Since eosinophils are multipotent effector cells, capable cytotoxicity and immune modulation, the putative interaction between IgE and eosinophils is a primary focus in current studies aimed at understanding the key components of disease pathogenesis. In this review, we provide an overview of BP pathogenesis, highlighting clinical and experimental evidence supporting central roles for IgE and eosinophils as independent mediators of disease and via their interaction. Additionally, therapeutics targeting IgE, the Th2 axis, or eosinophils are also discussed.

Characteristic Pattern of IL-17RA, IL-17RB, and IL-17RC in Monocytes/Macrophages and Mast Cells From Patients With Bullous Pemphigoid

Inflammation is largely implicated in bullous pemphigoid (BP), the most frequent skin auto-immune blistering disease. IL-17, essentially IL-17A/F, has been involved in blister formation through regulation of protease production, and its specific serum profile within BP was related to disease outcome. However, relationships between IL-17 family ligands and receptors are quite complex with six different IL-17 isoforms, and five different receptors. We here aimed at clarifying the contribution of the IL-17 axis in BP by characterizing not only the expression of IL-17 receptor (IL-17R) members within immune cells isolated from BP patients (PMNs, n = 9; T-lymphocytes, n = 10; and monocytes, n = 10) but also the expression of IL-17 isoforms in sera (n = 83), and blister fluid (n = 31) of BP patients. We showed that at diagnosis, IL-17RA and IL-17RC expression were significantly increased in monocytes isolated from BP patients as compared to those from control subjects (p = 0.006 and p = 0.016, respectively). Notably, both IL-17RA and IL-17RC mRNA expression remained elevated in BP monocytes at time of relapse. We further demonstrated a significant increase of all IL-17 isoforms tested in BP blister fluid compared with BP serum (IL-17A, p < 0.0001; IL-17A/F, p < 0.0001; IL-17B, p = 0.0023; IL-17C, p = 0.0022; IL-17E, p < 0.0001). Among all, IL-17B was the only cytokine for which a significant decreased concentration within blister fluid was observed in BP patients with severe disease compared to patients with moderate disease (p = 0.012). We further evidenced a significant negative correlation between IL-17B levels and blister/erosion BPDAI subscore (r = −0.52, p = 0.003). We finally identified mast cells as a potential target of IL-17B in lesional skin of BP patients. In conclusion, we showed here that IL-17RA and IL-17RC expression in monocyte was associated with disease activity and evidenced in situ a negative correlation between BP disease activity and IL-17B, whose effects could be mediated by IL-17RB expressed by mast cell in BP lesional skin.

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.

Learning From Success and Failure: Biologics for Non-approved Skin Diseases

The impressive potential of biologics has been demonstrated in psoriasis, hidradenitis suppurativa, and urticaria. Numerous biologicals are entering the field for a restricted number of skin disorders. Off-label use of biologics in other recalcitrant skin diseases has increased. Mounting data point to the potential of already existing biologics acting on the IL-17/IL-23 pathway in skin disorders with epidermal hyperkeratosis (e.g., pityriasis rubra pilaris), acneiform inflammation (e.g., hidradenitis suppurativa), and loss of mucosal integrity (e.g., aphthosis). TNF-α blockers are also effective in the latter conditions but seem of particular value in granulomatous (e.g., granuloma annulare) and neutrophilic disorders (e.g., pyoderma gangrenosum). Failure of IL-17 blockade in skin diseases resulting from immune-mediated cell destruction (e.g., alopecia areata and vitiligo) illustrates its limited involvement in Th1-dependent skin immunology. Overall, disappointing results of TNF-α blockers in alopecia areata and vitiligo point to the same conclusion although promising results in toxic epidermal necrolysis suggest TNF-α exerts at least some in vivo Th1-related activities. Acting on both the Th1 and Th17 pathway, ustekinumab has a rather broad potential with interesting results in lupus and alopecia areata. The efficacy of omalizumab in bullous pemphigoid has revealed an IgE-mediated recruitment of eosinophils leading to bullae formation. Reconsidering reimbursement criteria for less common but severe diseases seems appropriate if substantial evidence is available (e.g., pityriasis rubra pilaris). For other disorders, investigator- and industry-initiated randomized clinical trials should be stimulated. They are likely to improve patient outcome and advance our understanding of challenging skin disorders.

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

New Insights Into the Pathogenesis of Bullous Pemphigoid: 2019 Update

There are several lines of evidence indicating that the physiopathological bases of bullous pemphigoid (BP), the most common subepidermal autoimmune bullous disease, are hallmarked by the production of autoantibodies directed against the hemidesmosomal anchoring proteins BP180 and BP230. In contrast to the robustness of the latter assumption, the multifaceted complexity of upstream and downstream mechanisms implied in the pathogenesis of BP remains an area of intense speculation. So far, an imbalance between T regulatory cells and autoreactive T helper (Th) cells has been regarded as the main pathogenic factor triggering the autoimmune response in BP patients. However, the contributory role of signaling pathways fostering the B cell stimulation, such as Toll-like receptor activation, as well as that of ancillary inflammatory mechanisms responsible for blister formation, such as Th17 axis stimulation and the activation of the coagulation cascade, are still a matter of debate. In the same way, the pathomechanisms implied in the loss of dermal-epidermal adhesion secondary to autoantibodies binding are not fully understood. Herein, we review in detail the current concepts and controversies on the complex pathogenesis of BP, shedding light on the most recent theories emerging from the literature.

Detection of anti-type VII collagen IgE antibodies in epidermolysis bullosa acquisita

BACKGROUND

Epidermolysis bullosa acquisita (EBA) is a rare pemphigoid disease involving autoantibodies to type VII collagen (COL7), a major structural component of anchoring fibrils. IgE autoantibodies to type XVII collagen (BP180) have been identified in bullous pemphigoid (BP), the prototype of pemphigoid diseases. Although the pathogenic relevance of IgG anti-COL7 has been investigated, that of IgE in EBA remains unclear.

OBJECTIVES

To reveal the presence and pathogenic relevance of IgE anti-COL7 in EBA.

METHODS

We examined IgE antibodies in 109 patients with EBA by indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

IIF with normal human skin revealed IgE reactivity in the basement membrane zone in 29 (26·6%) cases. To verify whether the IgE antibodies were specific to COL7, we performed IIF with 21 clearly positive cases and the skin of a patient with dystrophic EBA, which does not involve COL7. All cases showed negative results, indicating that IgE antibodies were specific to COL7. In a modified IgG COL7 ELISA for IgE, 16 (14·7%) cases were positive (three and 13 cases were negative and positive on IIF, respectively). We compared anti-COL7 IgG and IgE, and found a weak but significant correlation (r = 0·459, P < 0·001). EBA is clinically divided into a mechanobullous (MB; noninflammatory) type and an inflammatory (INF) type resembling BP. Of the IIF-positive cases, 11 of 30 (37%) had INF and nine of 48 (19%) had MB.

CONCLUSIONS

This study is the first to demonstrate the presence of circulating anti-COL7 IgE in patients with EBA, which may correlate with the clinical phenotype.

Biological therapy of autoimmune blistering diseases

INTRODUCTION

Autoimmune blistering skin diseases are a group of disorders subdivided according to the location of blister formation: intraepidermal blistering in the pemphigus group and subepidermal in the pemphigoid group. These conditions are clinically heterogeneous and are treated with systemic corticosteroids and/or other forms of immunosuppression on the basis of clinical subtype and disease severity. These approaches may not be effective for the induction and maintenance of clinical response or need to be stopped because of intolerable side effects.

AREAS COVERED

Biological therapies can represent a valid alternative strategy in various autoimmune blistering disorders and this review article will address this issue with a special focus on pemphigus vulgaris and bullous pemphigoid. These biological approaches are designed to target B cells, autoantibodies, complement proteins, and several cytokines.

EXPERT OPINION

Innovative strategies for the treatment of autoimmune blistering conditions primarily depend on the use of drugs with a high degree of specificity targeting crucial steps in the immunopathology of these disorders. Novel biological agents offer treatment alternatives to patients with autoimmune blistering conditions by targeting B cells, pathogenic autoantibodies, complement and cytokines.

Biomarkers related to bullous pemphigoid activity and outcome

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disease of the skin. Investigation of the BP-associated pathophysiological processes during the last decades showed that the generation of autoantibodies directed against the hemidesmosome proteins BP180 and BP230, a hallmark of the BP-associated autoimmune response, leads to the recruitment of inflammatory immune cells at the dermal-epidermal junction, and subsequently to the release of a large amount of inflammatory molecules involved in blister formation. Analysis in transversal and longitudinal studies of autoantibodies and inflammatory molecules production both at the time of diagnosis and under treatment was mainly performed within the serum but also in the blister fluid. Some autoimmune or inflammatory molecules expression was related to the presence of clinical signs, while others were mere bystanders. In this review, we focused on the autoimmune and inflammatory molecules that have been identified as potential biomarkers of BP development and outcome.

IgE blockade in autoimmunity: Omalizumab induced remission of bullous pemphigoid

Bullous pemphigoid (BP) is a blistering dermopathy and a prototypic antibody-mediated autoimmune disease. Detection of IgG autoantibodies against hemidesmosomal proteins BP180 and/or BP230 are diagnostic and levels can correlate with disease activity. Therapies include corticosteroids and oral immunosuppressants, while intravenous immunoglobulin and rituximab are reserved for treatment resistant cases. Here we describe a patient with severe BP which was refractory to standard first line therapy, intravenous immunoglobulin and rituximab induced depletion of peripheral B cells. Use of the monoclonal anti-IgE antibody omalizumab resulted in rapid resolution of blistering despite ongoing high levels of anti-skin IgG antibodies. To our knowledge this is the first case of BP responsive to omalizumab after failure of rituximab to be reported. This case adds to emerging data on omalizumab as a novel BP treatment as well as providing new evidence of an independent role for autoreactive IgE-mediated inflammation in the formation of BP skin lesions.

Detection of IgE autoantibodies in mucous membrane pemphigoid and their association with disease severity

BACKGROUND

Mucous membrane pemphigoid (MMP) is an autoimmune disease characterized by scarring lesions at mucosal sites. Although the pathogenic role of specific IgG and/or IgA has been already demonstrated and the detection of these immunoglobulins is a criterion in the diagnosis of MMP, little is known about IgE role in this disease. Therefore, the main purpose of this study was to assess the presence of circulating and tissue bound IgE in patients with MMP and their possible correlations with clinical presentation and disease course.

METHODS

We conducted a retrospective study on 29 patients affected by MMP, recruited from a single center. Direct and indirect immunofluorescence studies were assessed to analyze the presence of specific IgE directed against the basal membrane zone. For each patient, fluorescence data were compared to clinical features.

RESULTS

Linear deposits of C3, IgG and IgA were present in 86.2%, 62% and 37.9% of cases respectively, while IgE linear deposits were detected in 17 out of 29 patients (58.6%) including one case with isolated IgE positivity. Circulating IgE and IgA anti-BMZ were present in 7 (24.1%) and 5 (17.2%) patients, respectively. Both the presence of circulating IgA and of tissue bound IgE deposits correlated with disease activity index (P<0.014).

CONCLUSIONS

Our results demonstrated the presence of IgE autoantibodies in MMP, particularly in more severe cases. Thus, IgE detection may represent an additional useful diagnostic tool in this disease.

IL-17A is functionally relevant and a potential therapeutic target in bullous pemphigoid

IL-17A has been identified as key regulatory molecule in several autoimmune and chronic inflammatory diseases followed by the successful use of anti-IL-17 therapy, e.g. in ankylosing spondylitis and psoriasis. Bullous pemphigoid (BP) is the most frequent autoimmune blistering disease with a high need for more specific, effective and safe treatment options. The aim of this study was to clarify the pathophysiological importance of IL-17A in BP. We found elevated numbers of IL-17A⁺ CD4⁺ lymphocytes in the peripheral blood of BP patients and identified CD3⁺ cells as major source of IL-17A in early BP skin lesions. IL17A and related genes were upregulated in BP skin and exome sequencing of 51 BP patients revealed mutations in twelve IL-17-related genes in 18 patients. We have subsequently found several lines of evidence suggesting a significant role of IL-17A in the BP pathogenesis: (i) IL-17A activated human neutrophils in vitro, (ii) inhibition of dermal-epidermal separation in cryosections of human skin incubated with anti-BP180 IgG and subsequently with anti-IL-17A IgG-treated leukocytes, (iii) close correlation of serum IL-17A levels and diseases activity in a mouse model of BP, (iv) IL17A-deficient mice were protected against autoantibody-induced BP, and (v) pharmacological inhibition of lL-17A reduced the induction of BP in mice. Our data give evidence for a pivotal role of IL-17A in the pathophysiology of BP and advocate IL-17A inhibition as potential novel treatment for this disease.

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.

Immunoglobulin G; structure and functional implications of different subclass modifications in initiation and resolution of allergy

IgE and not IgG is usually associated with allergy. IgE lodged on mast cells in skin or gut and basophils in the blood allows for the prolonged duration of allergy through the persistent expression of high affinity IgE receptors. However, many allergic reactions are not dependent on IgE and are generated in the absence of allergen specific and even total IgE. Instead, IgG plasma cells are involved in induction of, and for much of the pathogenesis of, allergic diseases. The pattern of IgG producing plasma cells in atopic children and the tendency for direct or further class switching to IgE are the principle factors responsible for long-lasting sensitization of mast cells in allergic children. Indirect class switching from IgG producing plasma cells has been shown to be the predominant pathway for production of IgE while a Th2 microenvironment, genetic predisposition, and the concentration and nature of allergens together act on IgG plasma cells in the atopic tendency to undergo further immunoglobulin gene recombination. The seminal involvement of IgG in allergy is further indicated by the principal role of IgG4 in the natural resolution of allergy and as the favourable immunological response to immunotherapy. This paper will look at allergy through the role of different antibodies than IgE and give current knowledge of the nature and role of IgG antibodies in the start, maintenance and resolution of allergy.

The Autoimmune Skin Disease Bullous Pemphigoid: The Role of Mast Cells in Autoantibody-Induced Tissue Injury

Bullous pemphigoid (BP) is an autoimmune and inflammatory skin disease associated with subepidermal blistering and autoantibodies directed against the hemidesmosomal components BP180 and BP230. Animal models of BP were developed by passively transferring anti-BP180 IgG into mice, which recapitulates the key features of human BP. By using these in vivo model systems, key cellular and molecular events leading to the BP disease phenotype are identified, including binding of pathogenic IgG to its target, complement activation of the classical pathway, mast cell degranulation, and infiltration and activation of neutrophils. Proteinases released by infiltrating neutrophils cleave BP180 and other hemidesmosome-associated proteins, causing DEJ separation. Mast cells and mast cell-derived mediators including inflammatory cytokines and proteases are increased in lesional skin and blister fluids of BP. BP animal model evidence also implicates mast cells in the pathogenesis of BP. However, recent studies questioned the pathogenic role of mast cells in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and epidermolysis bullosa acquisita. This review highlights the current knowledge on BP pathophysiology with a focus on a potential role for mast cells in BP and mast cell-related critical issues needing to be addressed in the future.

The Role of Mast Cells in Autoimmune Bullous Dermatoses

Skin mast cells (MCs), a resident immune cell type with broad regulatory capacity, play an important role in sensing danger signals as well as in the control of the local immune response. It is conceivable to expect that skin MCs regulate autoimmune response and are thus involved in autoimmune diseases in the skin, e.g., autoimmune bullous dermatoses (AIBD). Therefore, exploring the role of MCs in AIBD will improve our understanding of the disease pathogenesis and the search for novel therapeutic targets. Previously, in clinical studies with AIBD, particularly bullous pemphigoid, patients' samples have demonstrated that MCs are likely involved in the development of the diseases. However, using MC-deficient mice, studies with mouse models of AIBD have obtained inconclusive or even discrepant results. Therefore, it is necessary to clarify the observed discrepancies and to elucidate the role of MCs in AIBD. Here, in this review, we aim to clarify discrepant findings and finally elucidate the role of MCs in AIBD by summarizing and discussing the findings in both clinical and experimental studies.

Pathogenic mechanisms of IgE-mediated inflammation in self-destructive autoimmune responses

Autoantibodies of the IgG subclass are pathogenic in a number of autoimmune disorders such as systemic lupus erythomatosus. The presence of circulating IgE autoantibodies in autoimmune patients has also been known for almost 40 years. Despite their role in allergies, IgE autoantibodies are not associated with a higher rate of atopy in these patients. However, recently they have been recognized as active drivers of autoimmunity through mechanisms involving the secretion of Type I interferons by plasmacytoid dendritic cells (pDC), the recruitment of basophils to lymph nodes, and the activation of adaptive immune responses through B and T cells. Here, we will review the formation, prevalence, affinity, and roles of the IgE autoantibodies that have been described in autoimmunity. We also present novel evidence supporting that triggering of IgE receptors in pDC induces LC3-associated phagocytosis, a cellular process also known as LAP that is associated with interferon responses. The activation of pDC with immune complexes formed by DNA-specific IgE antibodies also induce potent B-cell differentiation and plasma cell formation, which further define IgE's role in autoimmune humoral responses.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.

IgE autoreactivity in bullous pemphigoid: eosinophils and mast cells as major targets of pathogenic immune reactants

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune disease characterized by tense blisters that are usually preceded by urticarial eruptions. Affected patients exhibit IgG and/or IgE autoantibodies against BP180 and/or BP230. Their relative importance in disease pathogenesis has not been fully elucidated.

OBJECTIVES

The aim of this study was to provide a better characterization of the circulating and tissue-resident IgE in patients with BP at the serological, structural and functional levels.

METHODS

Sera (n = 19) and skin (n = 33) from patients with BP were analysed via enzyme-linked immunosorbent assay (ELISA) and immunofluorescence, respectively.

RESULTS

The results obtained show that many patients with BP exhibit elevated IgE levels in the serum and in the skin. In the skin, it is very rarely and only sparsely found along the basement membrane zone, but is prominently present on mast cells and eosinophils. At least a portion of these IgE antibodies are BP-specific, as evidenced by serum ELISA and by the colocalization of BP180 and FcεRI-bound IgE on mast cells and/or eosinophils. An important role of these immune reactants can be inferred from our additional finding that cross-linking of IgE, derived from BP sera, on FcεRI-expressing rat basophils with BP180 results in robust degranulation of these cells.

CONCLUSIONS

We propose the existence of a disease pathway alternative to IgG and complement that may well be responsible for some of the clinical features of this autoimmune disease.

Eosinophils as putative therapeutic targets in bullous pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering skin disease and is characterized by the presence of autoantibodies directed against the hemidesmosomal proteins BP180 and BP230 that can be detected in the skin and serum of BP patients. Histologically, the dermal infiltration of eosinophils is obvious. The objective of this review was to present evidence that eosinophils play a key role in the pathogenesis of BP. Eosinophils, together with cytokines and chemokines regulating their production, recruitment and activation, are abundantly present in lesional skin, in blisters and in peripheral blood of patients with BP. Recently, using a cryosection model, eosinophils were demonstrated to induce dermal-epidermal separation in the presence of BP antibodies. Thus, eosinophils and their products, as well as mediators regulating their function, present promising targets for the treatment of BP.

IgE autoantibodies and their association with the disease activity and phenotype in bullous pemphigoid: a systematic review

Bullous pemphigoid (BP) is the most common autoimmune skin disease of blistering character. The underlying pathophysiological mechanism involves an immune attack, usually by IgG class autoantibodies, on the autoantigen BP 180/BPAg2, which is a type XVII collagen (COL17) protein acting as the adhesion molecule between the epidermis and the basement membrane of the dermis. About 40 years ago, following consistent findings of elevated total serum IgE levels in BP patients, it was hypothesized that IgE may be involved in the pathophysiology of BP. Our objective was to determine whether there is strong evidence for an association between IgE class autoantibodies and the clinical severity or phenotype of BP. Three databases were searched for relevant studies and appropriate exclusion and inclusion criteria were applied. Data was extracted and assessed in relation to the study questions concerning the clinical significance of IgE autoantibodies in BP. Nine studies found that anti-BP180 autoantibodies of IgE class are associated with increased severity of BP, whereas two studies did not find such an association. The number of studies which found an association between higher IgE autoantibody levels and the erythematous urticarial phenotype of BP (5) was equal in number to the studies which found no such association (5). In conclusion, higher serum IgE autoantibody levels are associated with more severe clinical manifestations of BP. There is insufficient evidence to support higher IgE autoantibody levels being associated with specific clinical phenotypes of BP.

Comorbidity of chronic spontaneous urticaria and autoimmune thyroid diseases: A systematic review

Patients with chronic spontaneous urticaria (CSU) are widely held to often have other autoimmune disorders, including autoimmune thyroid disease. Here, we systematically evaluated the literature on the prevalence of thyroid autoimmunity in CSU and vice versa. There is a strong link between CSU and elevated levels of IgG antithyroid autoantibodies (AAbs), with most of a large number of studies reporting rates of ≥10%. Levels of IgG against thyroid peroxidase (TPO) are more often elevated in CSU than those of other IgG antithyroid AAbs (strong evidence). Levels of IgG antithyroid AAbs are more often elevated in adult patients with CSU than in children (strong evidence). Patients with CSU exhibit significantly higher levels of IgG antithyroid AAbs (strong evidence) and IgE-anti-TPO (weak evidence) than controls. Elevated IgG antithyroid AAbs in CSU are linked to the use of glucocorticoids (weak evidence) but not to disease duration or severity/activity, gender, age, or ASST response (inconsistent evidence). Thyroid dysfunction rates are increased in patients with CSU (strong evidence). Hypothyroidism and Hashimoto's thyroiditis are more common than hyperthyroidism and Graves' disease (strong evidence). Thyroid dysfunction is more common in adult patients with CSU than in children (strong evidence) and in female than in male patients with CSU (weak evidence). Urticaria including CSU is more prevalent in patients with thyroid autoimmunity than in controls (weak evidence). CSU can improve in response to treatment with levothyroxine or other thyroid drugs (strong evidence). Pathogenic mechanisms in CSU patients with thyroid autoimmunity may include IgE against autoantigens, immune complexes, and complement.

Detection of IgE autoantibodies to BP180 and BP230 and their relationship to clinical features in bullous pemphigoid

BACKGROUND

IgE autoantibodies are considered to be involved in the pathogenesis of bullous pemphigoid (BP), particularly inflammatory and erythematous phenotypes.

OBJECTIVES

To develop reliable enzyme-linked immunosorbent assays (ELISAs) for the detection of IgE autoantibodies to both BP180 and BP230 in BP sera, and to compare the ELISA results with clinical features.

METHODS

We used commercially available IgG ELISAs to develop IgE ELISAs for both BP180 and BP230. To determine the influence of excess amounts of IgG autoantibodies, all normal and BP sera were tested before and after IgG adsorption. The results of the IgE ELISAs were statistically compared with various ELISAs and various clinical parameters, including our own severity scores and BP phenotypes.

RESULTS

IgG adsorption generally showed no changes in sensitivity and specificity for IgE ELISAs, although slight cross-reactivity of anti-IgE secondary antibody to IgG and interference of excess amounts of IgG autoantibodies to IgE reactivity were suggested. IgE autoantibodies to BP180 were found in 21 of 36 BP sera and IgE autoantibodies to BP230 were found in 18 of 36 BP sera. The results of IgG and IgE ELISAs for both BP180 and BP230 were well correlated. IgG and IgE anti-BP180 antibodies correlated with disease activity but IgG and IgE anti-BP230 autoantibodies did not. IgE anti-BP230 autoantibodies correlated with nodular phenotype but not erythematous phenotype.

CONCLUSIONS

The results of this study indicated that IgE autoantibodies to both BP180 and BP230 are frequently detected in BP sera. IgE anti-BP180 autoantibodies seemed to be pathogenic, while an association between IgE autoantibodies and inflammatory BP phenotype was not indicated.

Shifting Focus in the Therapeutics of Immunobullous Disease

Therapeutics of autoimmune bullous disease has seen a major shift of focus from more global immunosuppression to targeted immunotherapy. Anti CD 20 monoclonal antibody Rituximab revolutionized the therapeutics of autoimmune bullous disease particularly pemphigus. Though it is still being practiced off-label, evidences in the form of RCT and meta analysis are now available. Other novel anti CD 20 monoclonal antibodies like ofatumumab, veltuzumab, and ocrelizumab, tositumomab or obinutuzumab/GA101 may add to the therapeutic options in coming days. Beyond anti CD 20 monoclonal antibodies other options that show promise at least in select scenario are omalizumab, TNF inhibitors plasmapheresis and intravenous immunoglobulin. The present article will discuss the role of rituximab and other newer therapeutics in the treatment of autoimmune blistering disease, especially pemphigus and suggests their positions in the therapeutic ladder.