Serum levels of IgE anti-BP180 and anti-BP230 autoantibodies in patients with bullous pemphigoid

Pathophysiology of Bullous Pemphigoid: Role of Type 2 Inflammation and Emerging Treatment Strategies (Narrative Review)

Bullous pemphigoid (BP) is an autoimmune blistering disease that most often affects elderly individuals and has a significant negative impact on quality of life. The disease is characterized primarily by autoantibodies to hemidesmosomal proteins BP180 and/or BP230, and an inflammatory reaction with notable features of type 2 inflammation, including elevated serum IgE, increased numbers of eosinophils in lesions and peripheral blood, and elevated expression of type 2 cytokines and chemokines in skin lesions. In this review, we present what is known about BP pathophysiology, including the role of type 2 inflammation, and discuss how findings from studies of biologics targeting type 2 immune mediators have helped to clarify the biological mechanisms driving BP pathophysiology. Future studies of these targeted therapies and others in development will help to further elucidate the mechanisms underlying BP pathophysiology and potentially provide better treatment options for patients.

Bullous Pemphigoid Severity and Levels of Antibodies to BP180 and BP230: A Systematic Review and Meta-Analysis

Importance

The correlation between serum levels of autoantibodies against bullous pemphigoid (BP) antigens 180 (BP180) and 230 (BP230) with BP disease severity is unclear.

Objective

To investigate the correlation of anti-BP180 and anti-BP230 immunoglobulin G (IgG) antibody levels with BP disease severity.

Data Sources

A search was performed of the Cochrane Central Register of Controlled Trials, Embase, and PubMed databases from their respective inception to April 11, 2024.

Study Selection

Studies evaluating the correlation between serum levels of anti-BP180 or anti-BP230 IgG measured using enzyme-linked immunosorbent assay (ELISA) and disease severity assessed per the Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) or BP Disease Area Index (BPDAI) were included. No language or geographic restrictions were imposed. Nearly 0.4% of initially identified studies met the selection criteria.

Data Extraction and Synthesis

One researcher extracted data and another researcher confirmed data. The risk of bias was independently assessed by these researchers using the Quality Assessment of Diagnostic Accuracy Studies 2 tool, with discrepancies resolved by discussion with a third researcher. A random-effects model meta-analysis and a subgroup analysis were conducted based on the ELISA kit manufacturers.

Main Outcomes and Measures

Pooled correlation coefficients of antibody levels with ABSIS and BPDAI.

Results

In all, 14 studies with 1226 participants were analyzed. The risk of bias of included studies was generally low. The meta-analysis found anti-BP180 autoantibody levels showed moderate correlation with objective BPDAI (r = 0.56; 95% CI, 0.46-0.64) at baseline, strong correlation (r = 0.63; 95% CI, 0.39-0.79) at 3-month follow-up, and moderate correlation (r = 0.53; 95% CI, 0.25-0.72) at 6-month follow-up. Anti-BP180 autoantibody levels also showed moderate correlation (r = 0.52; 95% CI, 0.39-0.62) with ABSIS at baseline, strong correlation (r = 0.62; 95% CI, 0.39-0.79) at 3-month follow-up, and moderate correlation (r = 0.53; 95% CI, 0.25-0.72) at 6-month follow-up. By contrast, anti-BP230 autoantibody levels showed no association with objective BPDAI and ABSIS at diagnosis and follow-up. The subgroup analysis found similar results when using different ELISA kits.

Conclusions and Relevance

The findings of this systematic review and meta-analysis indicated that anti-BP180 autoantibody levels may serve as an adjunctive tool for monitoring BP disease severity and guiding clinical care for patients with BP.

Systemic Implications of Bullous Pemphigoid: Bridging Dermatology and Internal Medicine

Background: Bullous pemphigoid is an autoimmune bullous disease that frequently affects a large skin surface area, but it can also present in localized areas. It has been hypothesized that bullous pemphigoid affects the systemic functioning of different organs because inflammatory cells and cytokines circulate throughout numerous organs. Results: Recent clinical and experimental studies have revealed an association between bullous pemphigoid and systemic organ disorders. To avoid the emergence of systemic organ diseases, the significance of systemic treatment in cases of severe bullous pemphigoid should be emphasized. Conclusions: Here, we discuss the specific molecular processes underlying typical systemic organ inflammatory diseases associated with bullous pemphigoids.

Association of bullous pemphigoid with acquired hemophilia A: a case report

Acquired hemophilia A, a rare condition resulting in spontaneous bleeding without prior bleeding disorders, arises due to autoantibody-mediated inhibition of coagulation factor VIII and is typically associated with autoimmune, neoplastic, drug, or obstetric factors. We present the case of a 31-year-old woman with bullous pemphigoid, managed with corticosteroids since 2013, who presented spontaneous hemorrhagic manifestations. Upon admission, laboratory tests revealed hypochromic microcytic anemia, prolonged activated partial thromboplastin time, and a factor VIII level < 1%, indicative of acquired hemophilia A. Further assessments showed elevated Ristocetin cofactor activity, von Willebrand factor antigen, and a factor VIII inhibitor level of 665 BU. This underscores the importance of considering acquired hemophilia A in autoimmune dermatological conditions like bullous pemphigoid, highlighting the association between autoimmune disorders and coagulation abnormalities, particularly in cases of spontaneous hemorrhagic events.

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.

Advancements in Bullous Pemphigoid Treatment: A Comprehensive Pipeline Update

ABASTRACT

Bullous pemphigoid (BP) is a common autoimmune bullous disease affecting mainly the elderly, with rising incidence due to increased life expectancy. This disease is characterized by tense bullous lesions on normal or erythematous skin, accompanied by pruritus. BP pathogenesis involves autoantibodies against hemidesmosomal proteins BP180 and BP230, leading to detachment at the dermo-epidermal junction as well as blister formation. BP is associated with coexisting comorbidities and drug exposure, and its management often requires high doses or chronic use of systemic glucocorticoids, posing risks of adverse effects. This review focuses on novel treatment options for BP, exploring therapies targeting different immune pathways. Rituximab, a CD20 monoclonal antibody, depletes B-lymphocytes and has shown efficacy in severe cases. Dupilumab, targeting interleukin (IL)-4 receptor α and thus blocking IL-4 and IL-13, downregulates type 2 helper (Th2) responses and has demonstrated promising results. Targeting eosinophil-related molecules using bertilimumab and AKST4290 has yielded positive results in clinical trials. Omalizumab, an immunoglobulin (Ig) E antibody, can reduce disease severity and allows corticosteroid tapering in a number of cases. Complement inhibitors such as nomacopan and avdoralimab are being investigated. IL-17 and IL-23 inhibitors such as secukinumab and tildrakizumab have shown potential in a limited number of case reports. Neonatal Fc receptor antagonists such as efgartigimod are under investigation. Additionally, topical therapies and Janus kinase inhibitors are being explored as potential treatments for BP. These novel therapies offer promising alternatives for managing BP, with potential to improve outcomes and reduce high cumulative doses of systemic corticosteroids and related toxicities. Further research, including controlled clinical trials, is needed to establish their efficacy, safety, and optimal dosing regimens for BP management.

Autoreactive IgE: Pathogenic role and therapeutic target in autoimmune diseases

Autoimmunity is the break of tolerance to self-antigens that leads to organ-specific or systemic diseases often characterized by the presence of pathogenic autoreactive antibodies (AAb) produced by plasmablast and/or plasma cells. AAb are prevalent in the general population and not systematically associated with clinical symptoms. In contrast, in some individuals, these AAb are pathogenic and drive the development of signs and symptoms of antibody-mediated autoimmune diseases (AbAID). AAb production, isotype profiles, and glycosylations are promoted by pro-inflammatory triggers linked to genetic, environmental, and hormonal parameters. Recent evidence supports a role for pathogenic AAb of the IgE isotype in a number of AbAID. Autoreactive IgE can drive the activation of mast cells, basophils, and other types of FcεRI-bearing cells and may play a role in promoting autoantibody production and other pro-inflammatory pathways. In this review, we discuss the current knowledge on the pathogenicity of autoreactive IgE in AbAID and their status as therapeutic targets. We also highlight unresolved issues including the need for assays that reproducibly quantify IgE AAbs, to validate their diagnostic and prognostic value, and to further study their pathophysiological contributions to AbAID.

Advancing Treatment in Bullous Pemphigoid: A Comprehensive Review of Novel Therapeutic Targets and Approaches

Bullous pemphigoid is one of the most common autoimmune bullous diseases occurring primarily in the elderly. Pathogenic autoantibodies against BP180 and BP230 at the dermal-epidermal junction cause subepidermal blisters, erosions, and intense pruritus, all of which adversely affect the patients' quality of life and may increase their morbidity and mortality. Current systemic treatment options for bullous pemphigoid are limited to corticosteroids and immunosuppressants, which can have substantial side effects on these vulnerable patients that even exceed their therapeutic benefits. Therefore, more precisely, targeting therapies to the pathogenic cells and molecules in bullous pemphigoid is an urgent issue. In this review, we describe the pathophysiology of bullous pemphigoid, focusing on autoantibodies, complements, eosinophils, neutrophils, proteases, and the T helper 2 and 17 axes since they are crucial in promoting proinflammatory environments. We also highlight the emerging therapeutic targets for bullous pemphigoid and their latest discoveries in clinical trials or experimental studies. Further well-designed studies are required to establish the efficacy and safety of these prospective therapeutic options.

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.

Neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio are positively correlated with disease activity of bullous pemphigoid

Bullous pemphigoid (BP) is a complex inflammatory process with elevated levels of autoantibodies, eosinophils, neutrophils, and various cytokines. Hematological inflammatory biomarkers can reflect inflammatory state in various diseases. Up to now, the correlations of hematological inflammatory biomarkers and disease activity of BP remain unknown. The purpose of this study was to clarify the associations between hematological inflammatory biomarkers and disease activity of BP. The levels of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), platelet-to-neutrophil ratio (PNR) and mean platelet volume (MPV) of 36 untreated BP patients and 45 age and gender matched healthy controls were detected by routine blood tests. The correlations between hematological inflammatory markers and clinical characteristics of BP were statistically analyzed. The Bullous Pemphigoid Disease Area Index (BPDAI) was used to measure disease activity of BP. The mean levels of NLR, PLR, PNR and MPV in 36 untreated BP patients were 3.9, 157.9, 45.7 and 9.4 fl, respectively. Increased NLR (p < 0.001), PLR (p < 0.01), and MPV (p < 0.001) but decreased PNR (p < 0.001) were observed in BP patients when compared with healthy controls. In BP patients, the levels of NLR were positively correlated to BPDAI Erosion/Blister Scores (p < 0.01); and the levels of NLR and PLR were both positively correlated to BPDAI without Damage Score (both p < 0.05) and BPDAI Total Score (both p < 0.05). No correlation was found in other statistical analyses between hematological inflammatory markers and clinical characteristics in BP patients involved in the present study. Therefore, NLR and PLR are positively correlated with disease activity of BP.

Urticaria and mimickers of urticaria

Urticaria is a common skin condition encountered across various specialties in medicine, especially in dermatology and allergy/immunology practice. It has a heterogeneous presentation hence it is unsurprising that many skin conditions may be confused with urticaria. Urticaria may present as acute or chronic urticaria, the latter can be further categorised into chronic spontaneous and chronic inducible. In this article, we explore, explain, and summarise various skin lesions that are considered mimickers of urticaria, to promote understanding of each of the conditions highlighted, improve recognition, and reduce misdiagnosis.

Extracellular matrix in skin diseases: The road to new therapies

BACKGROUND

The extracellular matrix (ECM) is a vital structure with a dynamic and complex organization that plays an essential role in tissue homeostasis. In the skin, the ECM is arranged into two types of compartments: interstitial dermal matrix and basement membrane (BM). All evidence in the literature supports the notion that direct dysregulation of the composition, abundance or structure of one of these types of ECM, or indirect modifications in proteins that interact with them is linked to a wide range of human skin pathologies, including hereditary, autoimmune, and neoplastic diseases. Even though the ECM's key role in these pathologies has been widely documented, its potential as a therapeutic target has been overlooked.

AIM OF REVIEW

This review discusses the molecular mechanisms involved in three groups of skin ECM-related diseases - genetic, autoimmune, and neoplastic - and the recent therapeutic progress and opportunities targeting ECM.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This article describes the implications of alterations in ECM components and in BM-associated molecules that are determinant for guaranteeing its function in different skin disorders. Also, ongoing clinical trials on ECM-targeted therapies are discussed together with future opportunities that may open new avenues for treating ECM-associated skin diseases.

Interventions for bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune blistering disease. Oral steroids are the standard treatment. We have updated this review, which was first published in 2002, because several new treatments have since been tried.

OBJECTIVES

To assess the effects of treatments for bullous pemphigoid.

SEARCH METHODS

We updated searches of the following databases to November 2021: Cochrane Skin Specialised Register, CENTRAL, MEDLINE, and Embase. We searched five trial databases to January 2022, and checked the reference lists of included studies for further references to relevant randomised controlled trials (RCTs).

SELECTION CRITERIA

RCTs of treatments for immunofluorescence-confirmed bullous pemphigoid.

DATA COLLECTION AND ANALYSIS

At least two review authors, working independently, evaluated the studies against the review's inclusion criteria and extracted data from included studies. Using GRADE methodology, we assessed the certainty of the evidence for each outcome in each comparison. Our primary outcomes were healing of skin lesions and mortality.

MAIN RESULTS

We identified 14 RCTs (1442 participants). The main treatment modalities assessed were oral steroids, topical steroids, and the oral anti-inflammatory antibiotic doxycycline. Most studies reported mortality but adverse events and quality of life were not well reported. We decided to look at the primary outcomes 'disease control' and 'mortality'. Almost all studies investigated different comparisons; two studies were placebo-controlled. The results are therefore based on a single study for each comparison except azathioprine. Most studies involved only small numbers of participants. We assessed the risk of bias for all key outcomes as having 'some concerns' or high risk, due to missing data, inappropriate analysis, or insufficient information. Clobetasol propionate cream versus oral prednisone Compared to oral prednisone, clobetasol propionate cream applied over the whole body probably increases skin healing at day 21 (risk ratio (RR 1.08, 95% confidence interval (CI) 1.03 to 1.13; 1 study, 341 participants; moderate-certainty evidence). Skin healing at 21 days was seen in 99.8% of participants assigned to clobetasol and 92.4% of participants assigned to prednisone. Clobetasol propionate cream applied over the whole body compared to oral prednisone may reduce mortality at one year (RR 0.73, 95% CI 0.53 to 1.01; 1 study, 341 participants; low-certainty evidence). Death occurred in 26.5% (45/170) of participants assigned to clobetasol and 36.3% (62/171) of participants assigned to oral prednisone. This study did not measure quality of life. Clobetasol propionate cream may reduce risk of severe complications by day 21 compared with oral prednisone (RR 0.65, 95% CI 0.50 to 0.86; 1 study, 341 participants; low-certainty evidence). Mild clobetasol propionate cream regimen (10 to 30 g/day) versus standard clobetasol propionate cream regimen (40 g/day) A mild regimen of topical clobetasol propionate applied over the whole body compared to the standard regimen probably does not change skin healing at day 21 (RR 1.00, 95% CI 0.97 to 1.03; 1 study, 312 participants; moderate-certainty evidence). Both groups showed complete healing of lesions at day 21 in 98% participants. A mild regimen of topical clobetasol propionate applied over the whole body compared to the standard regimen may not change mortality at one year (RR 1.00, 95% CI 0.75 to 1.32; 1 study, 312 participants; low-certainty evidence), which occurred in 118/312 (37.9%) participants. This study did not measure quality of life. A mild regimen of topical clobetasol propionate applied over the whole body compared to the standard regimen may not change adverse events at one year (RR 0.94, 95% CI 0.78 to 1.14; 1 study, 309 participants; low-certainty evidence). Doxycycline versus prednisolone Compared to prednisolone (0.5 mg/kg/day), doxycycline (200 mg/day) induces less skin healing at six weeks (RR 0.81, 95% CI 0.72 to 0.92; 1 study, 213 participants; high-certainty evidence). Complete skin healing was reported in 73.8% of participants assigned to doxycycline and 91.1% assigned to prednisolone. Doxycycline compared to prednisolone probably decreases mortality at one year (RR 0.25, 95% CI 0.07 to 0.89; number needed to treat for an additional beneficial outcome (NNTB) = 14; 1 study, 234 participants; moderate-certainty evidence). Mortality occurred in 2.4% (3/132) of participants with doxycycline and 9.7% (11/121) with prednisolone. Compared to prednisolone, doxycycline improved quality of life at one year (mean difference 1.8 points lower, which is more favourable on the Dermatology Life Quality Index, 95% CI 1.02 to 2.58 lower; 1 study, 234 participants; high-certainty evidence). Doxycycline compared to prednisolone probably reduces severe or life-threatening treatment-related adverse events at one year (RR 0.59, 95% CI 0.35 to 0.99; 1 study, 234 participants; moderate-certainty evidence). Prednisone plus azathioprine versus prednisone It is unclear whether azathioprine plus prednisone compared to prednisone alone affects skin healing or mortality because there was only very low-certainty evidence from two trials (98 participants). These studies did not measure quality of life. Adverse events were reported in a total of 20/48 (42%) participants assigned to azathioprine plus prednisone and 15/44 (34%) participants assigned to prednisone. Nicotinamide plus tetracycline versus prednisone It is unclear whether nicotinamide plus tetracycline compared to prednisone affects skin healing or mortality because there was only very low-certainty evidence from one trial (18 participants). This study did not measure quality of life. Fewer adverse events were reported in the nicotinamide group. Methylprednisolone plus azathioprine versus methylprednisolone plus dapsone It is unclear whether azathioprine plus methylprednisolone compared to dapsone plus methylprednisolone affects skin healing or mortality because there was only very low-certainty evidence from one trial (54 participants). This study did not measure quality of life. A total of 18 adverse events were reported in the azathioprine group and 13 in the dapsone group.

AUTHORS' CONCLUSIONS

Clobetasol propionate cream applied over the whole body is probably similarly effective as, and may cause less mortality than, oral prednisone for treating bullous pemphigoid. Lower-dose clobetasol propionate cream applied over the whole body is probably similarly effective as standard-dose clobetasol propionate cream and has similar mortality. Doxycycline is less effective but causes less mortality than prednisolone for treating bullous pemphigoid. Other treatments need further investigation.

Comorbidity in bullous pemphigoid: up-date and clinical implications

Bullous pemphigoid is the most common autoimmune blistering disease in industrialized countries and particularly affects the elderly. In this patient population, comorbid diseases are frequent and may complicate management and treatment of bullous pemphigoid. A better understanding why distinct diseases are more frequent in bullous pemphigoid patients may lead to new pathophysiological insights and - as a consequence - result in better patient care. The association of bullous pemphigoid with neurological and psychiatric diseases is well known and confirmed by several case-control studies. Association with further diseases such as malignancy and metabolic diseases are still discussed controversially. In recent years new relationships between bullous pemphigoid and autoimmune as well as inflammatory skin diseases have been reported. This review provides a systematic overview on studies addressing comorbidity in bullous pemphigoid patients. Increasing the awareness of both, common and rare comorbid diseases, may enable clinicians to optimize patient support and individualized treatment of bullous pemphigoid.

Management of eosinophil-associated inflammatory diseases: the importance of a multidisciplinary approach

Elevated eosinophil counts in blood and tissue are a feature of many pathological processes. Eosinophils can migrate and accumulate in a wide variety of tissues and, by infiltrating a target organ, can mediate the development of several inflammatory diseases. The normalization of eosinophilia is a common biomarker of a treatable trait and can also be used as a prognostic and predictive biomarker since it implies a reduction in type 2 inflammation that contributes to disease pathogenesis. Biological therapies targeting this cell type and its proinflammatory mediators have been shown to be effective in the management of a number of eosinophilic diseases, and for this reason they constitute a potential common strategy in the treatment of patients with various multimorbidities that present with type 2 inflammation. Various biological options are available that could be used to simultaneously treat multiple target organs with a single drug, bearing in mind the need to offer personalized treatments under the umbrella of precision medicine in all patients with eosinophil-associated diseases (EADs). In addition to reviewing these issues, we also discuss a series of perspectives addressing the management of EAD patients from a multidisciplinary approach, with the collaboration of health professionals from different specialties who manage the different multimorbidities that frequently occur in these patients. We examine the basic principles of care that this multidisciplinary approach must cover and present a multidisciplinary expert opinion regarding the ideal management of patients with EADs, from diagnosis to therapeutic approach and follow-up.

Association between bullous pemphigoid and atopic dermatitis: a population-based case-control study in Taiwan

Although bullous pemphigoid (BP) and atopic dermatitis (AD) share pathogenic mechanisms, their relationship remains controversial. Therefore, we conducted a population-based case-control study to investigate the association between BP and AD in Taiwan. Based on the Taiwan National Health Insurance Research Database, 9344 patients with BP and 18,688 age- and sex-matched controls were enrolled between 2000 and 2013. Furthermore, the study included 7,196 BP patients and 14,392 controls, matched for age, sex, and propensity score of comorbidities, with a case to controls ratio of 1:2. Logistic regression analysis was performed to examine the association between AD and BP. In the age- and sex-matched cohorts, AD (odds ratio [OR], 1.71; 95% confidence interval [CI], 1.50-1.95) was independently associated with BP. In the age, sex, and comorbidities-matched cohorts, AD (OR 1.76, 95% CI 1.55-2.00) remained a significant risk factor for BP. Other significant risk factors included psoriasis, hypertension, diabetes mellitus, chronic kidney disease, chronic obstructive pulmonary disease, neuropsychiatric diseases, and autoimmune connective tissue disease. Limitations of this study include the lack of information on disease severity and phenotypes of BP and misclassification of diseases as potential sources of bias. In conclusion, AD increased the risk of developing BP by 76%, and this association was independent of many BP comorbidities. Further studies are warranted to investigate the clinical and pathophysiological relevance of factors contributing to BP and AD.

Adaptive and innate immune pathogenesis of bullous pemphigoid: A review

Bullous pemphigoid (BP) is an autoimmune blistering disease that primarily affects elderly individuals. The presentation of BP is heterogeneous, typically manifesting as microscopic subepidermal separation with a mixed inflammatory infiltrate. The mechanism of pemphigoid development is unclear. B cells play a major role in pathogenic autoantibody production, and T cells, type II inflammatory cytokines, eosinophils, mast cells, neutrophils, and keratinocytes are also implicated in the pathogenesis of BP. Here, we review the roles of and crosstalk between innate and adaptive immune cells in BP.

Self-reactive IgE and anti-IgE therapy in autoimmune diseases

Growing evidence indicates the pathogenic role of autoreactive IgE in autoimmune diseases. Incidence of autoimmune and allergic diseases in the industrialized countries is consistently icreasing, thus leading to concerted efforts to comprehend the regulation of IgE-mediated mechanisms. The first reports of a presence of IgE autoantibodies in patients with autoimmune diseases have been published a long time ago, and it is now recognized that self-reactive IgE can mediate inflammatory response in bullous pemhigoid, systemic lupus erythematosus, chronic urticaria, and atopic dermatitis. The advances in understanding the pathomechanisms of these disorders brought to a successful use of anti-IgE strategies in their management. The present review discusses the current state of knowledge on the IgE-mediated autoimmunity and anti-IgE treatment, and pave the way for further exploration of the subject.

Bullous pemphigoid: The role of type 2 inflammation in its pathogenesis and the prospect of targeted therapy

Bullous pemphigoid (BP) is an autoimmune disease that mainly occurs in the elderly, severely affecting their health and life quality. Traditional therapy for BP is mainly based on the systemic use of corticosteroids, but long-term use of corticosteroids results in a series of side effects. Type 2 inflammation is an immune response largely mediated by group 2 innate lymphoid cells, type 2 T helper cells, eosinophils, and inflammatory cytokines, such as interleukin (IL)-4, IL-5 and IL-13. Among patients with BP, the levels of immunoglobulin E and eosinophils are significantly increased in the peripheral blood and skin lesions, suggesting that the pathogenesis is tightly related to type 2 inflammation. To date, various targeted drugs have been developed to treat type 2 inflammatory diseases. In this review, we summarize the general process of type 2 inflammation, its role in the pathogenesis of BP and potential therapeutic targets and medications related to type 2 inflammation. The content of this review may contribute to the development of more effective drugs with fewer side effects for the treatment of BP.

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.

Type XVII collagen: Relevance of distinct epitopes, complement-independent effects, and association with neurological disorders in pemphigoid disorders

Pemphigoid diseases (PD) are autoimmune skin blistering diseases characterized by autoantibodies directed against proteins of the cutaneous basement membrane zone (BMZ). One of the major antigens is type XVII collagen (BP180), a transmembrane glycoprotein, which is targeted in four PDs: bullous pemphigoid, mucous membrane pemphigoid, linear IgA dermatosis, and pemphigoid gestationis. To date, different epitopes on BP180 have been described to be recognized by PD disease patients’ autoantibodies. Different BP180 epitopes were associated with distinct clinical phenotypes while the underlying mechanisms are not yet fully understood. So far, the main effects of anti-BP180 reactivity are mediated by Fcγ-receptors on immune cells. More precisely, the autoantibody–antigen interaction leads to activation of complement at the BMZ and infiltration of immune cells into the upper dermis and, by the release of specific enzymes and reactive oxygen species, to the degradation of BP180 and other BMZ components, finally manifesting as blisters and erosions. On the other hand, inflammatory responses independent of Fcγ-receptors have also been reported, including the release of proinflammatory cytokines and internalization and depletion of BP180. Autoantibodies against BP180 can also be found in patients with neurological diseases. The assumption that the clinical expression of PD depends on epitope specificity in addition to target antigens, autoantibody isotypes, and antibody glycosylation is supported by the observation that epitopes of PD patients differ from those of PD patients. The aim of the present review is to describe the fine specificities of anti-BP180 autoantibodies in different PDs and highlight the associated clinical differences. Furthermore, the direct effects after binding of the autoantibodies to their target are summarized.

Deciphering the Contribution of BP230 Autoantibodies in Bullous Pemphigoid

Bullous pemphigoid (BP) is a subepidermal autoimmune blistering disease predominantly affecting elderly patients and carries significant morbidity and mortality. Patients typically suffer from severe itch with eczematous lesions, urticarial plaques, and/or tense blisters. BP is characterized by the presence of circulating autoantibodies against two components of the hemidesmosome, BP180 and BP230. The transmembrane BP180, also known as type XVII collagen or BPAG2, represents the primary pathogenic autoantigen in BP, whereas the intracellular BP230 autoantigen is thought to play a minor role in disease pathogenesis. Although experimental data exist suggesting that anti-BP230 antibodies are secondarily formed following initial tissue damage mediated by antibodies targeting extracellular antigenic regions of BP180, there is emerging evidence that anti-BP230 IgG autoantibodies alone directly contribute to tissue damage. It has been further claimed that a subset of patients has a milder variant of BP driven solely by anti-BP230 autoantibodies. Furthermore, the presence of anti-BP230 autoantibodies might correlate with distinct clinical features. This review summarizes the current understanding of the role of BP230 and anti-BP230 antibodies in BP pathogenesis.

Gliptin-associated bullous pemphigoid shows peculiar features of anti-BP180 and -BP230 humoral response: results from a multicenter study

BACKGROUND

Recently, several case-control studies demonstrated an association between gliptins and bullous pemphigoid (BP) occurrence. Data on clinical and immunological features of gliptin-associated bullous pemphigoid (GABP) are controversial.

OBJECTIVE

This study aims to clinically and immunologically characterize a large cohort of GABP patients to get insight into the pathophysiology of this emerging drug-induced variant of BP.

METHODS

Seventy-four GABP patients were prospectively enrolled and characterized from nine different Italian Dermatology Units between 2013 and 2020.

RESULTS

Our findings demonstrate that in GABP patients: i) the non-inflammatory phenotype which is characterized by low amounts of circulating and skin infiltrating eosinophils is frequently found; ii) IgG, IgE and IgA humoral response to BP180 and BP230 antigens is reduced in frequency and titers when compared with idiopathic BP; iii) IgG reactivity targets multiple BP180 epitopes other than NC16A.

LIMITATIONS

A limitation of the study is the control group that did not comprise only type 2 diabetes mellitus BP patients.

CONCLUSIONS

GABP patients show peculiar features of anti-BP180 and -BP230 humoral response laying the foundations for diagnostic improvements and to get novel insights into understanding the mechanism of BP onset.

A blistering new era for bullous pemphigoid: A scoping review of current therapies, ongoing clinical trials, and future directions

Bullous pemphigoid (BP) is a severe autoimmune blistering skin disorder that primarily causes disease in the older population and is the most prevalent subepidermal variant of the pemphigoid diseases. It manifests as exquisitely pruritic vesiculobullous eruptions and is associated with significant morbidity and mortality. Studies are reporting an increase in prevalence, and, among the elderly, BP is no longer considered to be as rare as previously thought. The pathogenesis involves autoantibodies directed against proteinaceous components of hemidesmosomes, with consequent autoimmune destruction of the dermal-epidermal junction. In recent times, more complex elements of the underlying inflammatory orchestra have been elucidated and are being used to develop targeted immunotherapies. The primary treatment modalities of BP include the use of topical and systemic corticosteroids, certain non-immunosuppressive agents (tetracyclines, nicotinamide, and sulfone), and immunosuppressants (methotrexate, azathioprine, cyclophosphamide, and Mycophenolate). However, in the long term, most of these agents are associated with substantial toxicities while recurrence rates remain high. Such egregious prospects led to significant efforts being directed towards developing newer targeted therapies which work by attenuating specific newly discovered pillars of the inflammatory pathway, and these efforts have garnered hope in providing safer alternatives. Our review focuses on presenting the various therapeutic options that are currently in trial since December 2019, as well as on summarizing presently established treatment guidelines to provide readers with the latest exciting updates.

BP230 IgE autoantibodies in topical-steroid-resistant bullous pemphigoid

BACKGROUND

IgE autoantibodies targeting BP230 can be identified in 38%-68% of bullous pemphigoid (BP) patients, yet the diagnostic and pathogenic value of anti-BP230 IgE still remains inconclusive.

OBJECTIVE

We intend to investigate the clinical and immunological characteristics of anti-BP230 IgE in BP patients.

METHODS AND RESULTS

Fifty-four BP patients were divided into two groups based on the responsiveness of a topical steroid. We investigated clinical features and IgE autoantibodies profiles by indirect immunofluorescence, ELISA and western blot between the two groups. BP disease area index (BPDAI) scores, total IgE, peripheral eosinophil counts, and anti-BP230 IgE level were significantly higher in the topical-steroid-resistant group. The majority of topical-steroid-resistant patients present with blister/erythematous phenotype (64.3%) and anti-BP230 IgE (59.5%), which correlates with total IgE levels. ELISAs of domain-specific BP230 recombinant proteins indicated that IgE in the topical-steroid-resistant group can react with all seven domains of BP230 and more frequently with the BP230-R1 epitope.

CONCLUSION

Anti-BP230 IgE is more frequently observed in topical-steroid-therapy-resistant patients and the prefers R1 domain of BP230, which is not included in commercially available testing kits. Our study further suggests the pathogenic role of anti-BP230 IgE in BP. Performing anti-BP230 IgE detection can serve as an indicator for initiating systemic steroid therapy.

IgE autoantibodies in serum and skin of non-bullous and bullous pemphigoid patients

BACKGROUND

Non-bullous pemphigoid (NBP) is a pemphigoid variant which frequently resembles other pruritic skin diseases. In contrast with bullous pemphigoid (BP), blisters are absent. In BP, previous studies showed that IgE autoantibodies may be involved in its pathogenesis. IgE-activated mast cells, basophils and eosinophils may participate in BP by inducing pruritus and possibly blister formation, although the differential role of IgE in NBP compared with BP has not yet been described.

OBJECTIVE

To assess IgE in serum and skin of NBP and BP patients.

METHODS

We examined total IgE and pemphigoid-specific IgE in the serum of 68 NBP and 50 BP patients by enzyme-linked immunosorbent assay (ELISA). Sera of 25 pemphigus patients and 25 elderly patients with pruritus were included as controls. Skin biopsies of 14 NBP and 14 BP patients with the highest IgE titres to NC16A were stained for IgE by immunofluorescence techniques.

RESULTS

Total IgE was elevated in 63% of NBP and 60% of BP patients, and in 20% of pemphigus controls, as well as 60% of elderly controls. IgE ELISAs were more frequently positive in BP than in NBP (NC16A 18% vs. 9%, P = 0.139; BP230 34% vs. 22%, P = 0.149). IgE ELISAs for NC16A and BP230 were positive in 8% and 20% of elderly controls, respectively, while all pemphigus controls were negative. Two of 28 biopsies (7%; one NBP, one BP) showed linear IgE along the basement membrane zone, while in most biopsies (71% NBP; 86% BP) IgE was bound to dermal cells.

CONCLUSION

Since IgE was present in the serum and skin of both NBP and BP patients, this supports IgE-dependent mechanisms common to both diseases, such as pruritus. However, it remains to be elucidated whether IgE contributes to blister formation in BP.

Complete Remission in a Patient with Treatment Refractory Bullous Pemphigoid after a Single Dose of Omalizumab

Bullous pemphigoid (BP) is an autoimmune disorder known to be mediated by immunoglobulin G (IgG) autoantibodies. The role of immunoglobulin E (IgE) antibodies is being investigated as their presence has been described in severe cases. Herein, we report a patient of BP who was refractory to most conventional agents and developed hypotension after rituximab but achieved lasting remission after a single dose of the anti-IgE monoclonal antibody omalizumab.

Role of BP230 autoantibodies in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune disease associated with subepidermal blistering due to autoantibodies directed against BP180 and BP230. BP180 is currently considered as the major pathogenic autoantigen. However, previous clinical findings suggested that anti-BP230 autoantibodies alone can cause skin lesions in animal models and many BP patients. The characteristics of BP230 and the pathogenic roles of anti-BP230 antibodies have been proposed. First, at the molecular level, BP230 mediates the attachment of keratin intermediate filaments to the hemidesmosomal plaque and interacts with other constituents of hemidesmosomes. Second, the presence of BP230 autoantibodies may correlate with specific clinical features of BP. The immunoglobulin (Ig)G autoantibodies from BP patients react mainly against the C-terminus of BP230, while the IgE autoantibodies are still inconclusive. Third, in vivo, autoantibodies against BP230 involved in the disease may not only induce the inflammatory response but also impair the structural stability of hemidesmosomes. This article reviews recently published work about the role of BP230 and its antibodies, including IgG and IgE, aiming to find clues of its clinical association and lay the foundation for the research on the pathogenicity of antibodies against BP230.

Correlation of dermal and blood eosinophilia with bullous pemphigoid disease severity

Background

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease associated with immune response against BP-180 and BP-230. Peripheral blood eosinophilia and dermal infiltration of eosinophils are common findings in BP.

Objective

The aim of our study was to demonstrate a statistical correlation between dermal and peripheral blood eosinophilia, anti BP-180, and anti BP-230 IgG and clinical severity of BP.

Methods

A total of 27 patients with newly diagnosed BP were included. Severity of disease was assessed according to the bullous pemphigoid disease activity index (BPDAI). Anti-BP-180 and anti-BP-230 titers, peripheral blood eosinophilia, and dermal eosinophil infiltration and tissue inflammation severity were assessed for each patient.

Results

A significant correlation was found between the serum levels of anti-BP-180 and anti-BP-230, and dermal eosinophilia and tissue inflammation severity with objective and subjective BPDAI scores. In addition, there was a significant correlation between the percentage of peripheral blood eosinophils and subjective BPDAI scores and urticarial/eczematous lesions. Moreover, the mucosal component did not show any correlation with autoantibody levels and inflammation severities.

Conclusion

Anti-BP-180 and anti-BP-230 levels, tissue inflammation severity, and dermal eosinophilia had a strong and significant correlation with BP severity. In addition, percentage of peripheral blood eosinophilia showed a correlation with subjective BPDAI scores.

Resolution in bullous pemphigoid

Pemphigoid diseases are a group of autoimmune blistering skin diseases defined by an immune response against certain components of the dermal-epidermal adhesion complex. They are prototypical, autoantibody-driven, organ-specific diseases with the emergence of inflammatory skin lesions dependent on the recruitment of immune cells, particularly granulocytes, into the skin. During an acute flare of disease, inflammatory skin lesions typically progressing from erythema through urticarial plaques to subepidermal blisters erosions erupt and, finally, completely resolve, thus illustrating that resolution of inflammation is continuously executed in pemphigoid disease patients and can be directly monitored on the skin. Despite these superb conditions for examining resolution in pemphigoid diseases as paradigm diseases for antibody-induced tissue inflammation, the mechanisms of resolution in pemphigoid are underinvestigated and still largely elusive. In the last decade, mouse models for pemphigoid diseases were developed, which have been instrumental to identify several key pathways for the initiation of inflammation in these diseases. More recently, also protective pathways, specifically IL-10 and C5aR2 signalling on the molecular level and Tregs on the cellular level, counteracting skin inflammation have been highlighted and may contribute to the continuous execution of resolution in pemphigoid diseases. The upstream orchestrators of this process are currently under investigation. Pemphigoid disease patients, particularly bullous pemphigoid patients, who are predominantly above 75 years of age, often succumb to the side effects of the immunosuppressive therapeutics nowadays still required to suppress the disease. Pemphigoid disease patients may therefore represent a group of patients benefiting most substantially from the introduction of non-immunosuppressive, proresolving therapeutics into the treatment regimens for their disease.

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.

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.

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.

Immunoglobulin E-Mediated Autoimmunity

The study of autoimmunity mediated by immunoglobulin E (IgE) autoantibodies, which may be termed autoallergy, is in its infancy. It is now recognized that systemic lupus erythematosus, bullous pemphigoid (BP), and chronic urticaria, both spontaneous and inducible, are most likely to be mediated, at least in part, by IgE autoantibodies. The situation in other conditions, such as autoimmune uveitis, rheumatoid arthritis, hyperthyroid Graves’ disease, autoimmune pancreatitis, and even asthma, is far less clear but evidence for autoallergy is accumulating. To be certain of an autoallergic mechanism, it is necessary to identify both IgE autoantibodies and their targets as has been done with the transmembrane protein BP180 and the intracellular protein BP230 in BP and IL-24 in chronic spontaneous urticaria. Also, IgE-targeted therapies, such as anti-IgE, must have been shown to be of benefit to patients as has been done with both of these conditions. This comprehensive review of the literature on IgE-mediated autoallergy focuses on three related questions. What do we know about the prevalence of IgE autoantibodies and their targets in different diseases? What do we know about the relevance of IgE autoantibodies in different diseases? What do we know about the cellular and molecular effects of IgE autoantibodies? In addition to providing answers to these questions, based on a broad review of the literature, we outline the current gaps of knowledge in our understanding of IgE autoantibodies and describe approaches to address them.

BPDAI and ABSIS correlate with serum anti-BP180 NC16A IgG but not with anti-BP230 IgG in patients with bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous disease characterized by autoantibody production against BP180 and BP230. Two scoring systems have been validated for BP including: Bullous Pemphigoid Disease Area Index (BPDAI) and Autoimmune Bullous Skin Disorder Intensity Score (ABSIS). In this study, we investigated correlations between both scoring systems and either anti-BP180 NC16A or anti-BP230 values. BPDAI and ABSIS were used to measure disease activity in 95 BP patients at Razi Hospital in Tehran, Iran. ELISA was performed on patient sera to identify any significant relationship between anti-BP180 NC16A/anti-BP230 values and BP disease activity. The two scores showed a strong correlation (ρ = 0.73; p value < 0.0001). Anti-BP180 NC16A values correlated with BPDAI (ρ = 0.49, p value = 0.0001), ABSIS (ρ = 0.47, p value < 0.0001), and BPDAI-Pruritus scores (ρ = 0.29, p value < 0.005). There was a strong correlation between anti-BP180 NC16A values and the ABSIS Skin score (ρ = 0.58, p value < 0.0001), and a moderate correlation with erosion/blister BPDAI score (ρ = 0.48, p value < 0.001) and urticaria/erythema BPDAI score (ρ = 0.27, p value = 0.009). Anti-BP230 values did not demonstrate any relationship with either scores or their subcomponents. Both scoring systems demonstrated moderate validity. Mucosal components did not show any correlation with anti-BP antibodies and are disproportionately presented in both BP scoring tools.

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.

Association of HLA class I and class II alleles with bullous pemphigoid in Chinese Hans

BACKGROUND

Bullous pemphigoid (BP) is one of the most common autoimmune skin diseases. Associations of genes, especially human leukocyte antigen (HLA)-DQ alleles, with BP indicate that genetic predisposition contributes to the disease.

OBJECTIVES

To evaluate the association of HLA class I and HLA class II alleles with susceptibility to BP in the northern Chinese Han population.

METHODS

We performed genotype for HLA-A, -B, -C, -G, -DPA1, -DPB1, -DQA1, -DQB1 and -DRB1 loci in 105 patients with BP by Sanger sequence-based typing (SBT) method. These data were compared with a local control cohort of 420 age- and sex-matched cases.

RESULTS

Among the HLA alleles described herein, the susceptibility alleles associated with a high prevalence of BP were A*11:01 (OR = 1.9 Pc = 0.017); B*37:01 (OR = 8, Pc = 1.811 × 10^-6); G*01:01 (OR = 3.61, Pc = 2.839 × 10^-15) and G*01:06 (OR = 2.22, Pc = 0.025); DQA1*01:05 (OR = 4.87, Pc = 5.822 × 10^-5), DQA1*05:05 (OR = 2.64, Pc = 9.114 × 10^-4), and DQA1*05:08 (OR = 10.2, Pc = 0.016); DQB1*03:01 (OR = 1.69, Pc = 0.048) and DQB1*05:01 (OR = 3.42, Pc = 7.28 × 10^-6); and DRB1*10:01 (OR = 6.85, Pc = 2.63 × 10^-6). To the contrary, HLA-DQA1*01:02 (OR = 0.46, Pc = 8.603 × 10^-4) and DQA1*01:03 (OR = 0.38, Pc = 0.048); DQB1*02:02 (OR = 0.28, Pc = 0.016); and DRB1*07:01 (OR = 0.26, Pc = 0.004) had significant associations with protection against BP. In addition, the frequency of haplotype HLA-DRB1*13-DQA1*05-DQB1*03 (OR = 12.32, Pc = 0.026) in BP patients was significantly higher than those in controls.

CONCLUSION

Our data demonstrated that the alleles and haplotypes found in this study may be important differential genetic markers for susceptibility to or protection against BP in individuals of northern Chinese Han population.

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.

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.

A multi-hit hypothesis of bullous pemphigoid and associated neurological disease: Is HLA-DQB1*03:01, a potential link between immune privileged antigen exposure and epitope spreading?

Bullous pemphigoid (BP) is the most common autoimmune blistering disease and is linked to IgG recognition of 2 hemidesmosomal antigens, that is, BP230 (BP antigen 1) and BP180 (BP antigen 2, collagen XVII). The association of BP with other systemic diseases, particularly neurocognitive diseases, provides a potential clue in the underlying pathogenesis of BP. The role of HLA-DQB1*03:01 binding to the immunogenic portion of BP180 provides a potential mechanism by which exposure to neuronal collagen BP180 may lead to cutaneous disease. In our proposed multi-hit hypothesis, patients with underlying neuronal disease are exposed to previously sequestered self-antigen, most importantly BP180. Patients with the HLA-DQB1*03:01 allele show an increased T-cell avidity to several epitopes of BP180, particularly the BP180-NC16a domain. Thus, they have a genetic susceptibility to developing BP upon exposure to the target antigen. In a patient with dysregulation of Th1/Th2 balance, anergy is lost and T-cells are subsequently primed resulting in the development of functional autoimmunity against the BP180-NC16a domain leading to clinically overt disease.

Autoreactive IgE in Chronic Spontaneous/Idiopathic Urticaria and Basophil/Mastocyte Priming Phenomenon, as a Feature of Autoimmune Nature of the Syndrome

Recent years of research have shed a new light on the role of IgE in immune reactions. It seems to be more than just a contribution to immediate type of allergic response. It appears that monomeric IgE may enhance mast cell activity without cross-linking of FcεRI by IgE specific allergen or autoreactive IgG anti-IgE antibodies. Monomeric IgE molecules are heterogeneous concerning their ability to induce survival and activation of mast cells only by binding the IgE to FcεRI, but not affecting degranulation of cells. It also turned out that IgE may react to autoantigens occurring in the blood not only in chronic spontaneous urticaria (CSU) but also in other autoimmune diseases. The aforementioned phenomena may promote the activity of mast cells/basophils in CSU that easily degranulate when influenced by various inner (autoreactive IgG against IgE and FcεRI, autoreactive IgE for self-antigens) and outer factors (cold, heat, pressure) or allergens. These findings forced the new approach to the role of autoimmunity, self-antigens and IgE autoantibodies in the pathology of CSU. CSU put in the scheme of autoreactive IgG and autoreactive IgE seems to be either a kind of an autoimmune disease or a clinical manifestation of some other defined autoimmune diseases or both.

A role for auto-immunity in chronic rhinosinusitis? Lessons learned from sub-epidermal bullous disorders of the skin

Chronic rhinosinusitis (CRS) is a frequent chronic condition, which has origins in complex interactions between genetic, immunological and microbial factors. The role of auto-immunity in CRS remains unclear, although recent studies have started to emerge in CRS patient refractory to maximal medical management. We discuss the possible auto-immunity link between CRS and other skin diseases, in particular acquired bullous dermatoses, and review the current evidence. We raise additional considerations for auto-immunity from both research and clinical standpoints.