Eosinophils Mediate Tissue Injury in the Autoimmune Skin Disease 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.

Type XVII Collagen-Specific CD4+ T Cells Induce Bullous Pemphigoid by Producing IL-5

Bullous pemphigoid is an autoimmune subepidermal blistering disease caused by anti-type XVII collagen (COL17) antibodies. Bullous pemphigoid has some immunological features such as eosinophilic infiltration and the deposition of IgE autoantibodies in the skin; however, the mechanism behind such features remains largely unclear. We focused on the autoantigen-specific CD4+ T cells, which are considered to regulate immune response. We established COL17-specific CD4+ T cell lines in vitro. Wild-type mice were immunized with synthesized peptides that include a pathogenic epitope of COL17, and lymphocytes were subjected to a limiting dilution assay. We established 5 T cell lines and examined the pathogenicity by transferring them with COL17-primed B cells into Rag-2-/-/COL17-humanized mice that express human COL17 but not mouse COL17 in the skin. Notably, 3 lines induced bullous pemphigoid-like skin changes associated with subepidermal separation and eosinophilic infiltration histologically and the production of anti-COL17 antibodies. The other 2 lines did not induce such phenotypes. RNA-sequencing analysis revealed that T helper 2 cytokines, particularly IL-5, were highly expressed in the pathogenic T-cell lines. Anti-IL-5 antibody administration significantly reduced the skin changes and attenuated the production of autoantibodies. Thus, the production of IL-5 is critical for COL17-specific CD4+ T cells to induce bullous pemphigoid phenotypes in vivo.

Recent Applications of Amphiphilic Copolymers in Drug Release Systems for Skin Treatment

Amphiphilic copolymers (ACs) are versatile systems with self-assembling and aggregating properties, enabling the formation of nanomaterials (NMs) such as micelles, vesicles, nanocapsules, and nanogels. These materials have been extensively explored for the delivery of various drugs and active compounds, enhancing the solubility and permeation of poorly water-soluble drugs into skin tissue. This improvement facilitates the treatment of skin diseases, including chronic conditions like cancer, as well as infections caused by bacteria, fungi, and viruses. This review summarizes recent applications of ACs in skin treatment, with a particular focus on their use in anti-cancer drug therapy. It covers the synthesis, classification, and characterization of ACs using various experimental techniques. Additionally, it discusses recent research on different drug delivery pathways using ACs, including encapsulation efficiency, release behavior, characteristics, applications, and responses to various chemical and physical stimuli (both in vivo and in vitro). Furthermore, this review provides a comprehensive analysis of the effects of ACs NMs on several skin diseases, highlighting their potential as alternative treatments.

A case of eosinophilic granulomatosis with polyangiitis preceded by allergic bullous lesions

A 62-year-old man with a history of diabetes mellitus was hospitalised with numbness of lower limbs, bullous lesions of the whole body, kidney dysfunction, presence of eosinophils, and elevated antineutrophil cytoplasmic antibodies to myeloperoxidase and anti-bullous pemphigoid 180 antibodies and was diagnosed with mononeuritis multiplex. Kidney and muscle biopsies showed vasculitis with fibrinoid necrosis, whereas skin biopsies showed only blister formation between the epidermis and dermis; a high eosinophilic infiltrate was present in all three tissues. These findings led to a diagnosis of eosinophilic granulomatosis with polyangiitis combined with allergic bullous lesions. Immunohistological examination indicated cytolytic eosinophils and extracellular traps, suggesting the presence of eosinophil extracellular trap cell death (eosinophil ETosis) in diseased tissue.

Characterization of the immune suppressive functions of eosinophils

Eosinophils account for a significant portion of immune cells in the body. It is well known that eosinophils play a role in the pathogenesis of many diseases. In which the interaction between eosinophils and other immune cells is incompletely understood. The aim of this study is to characterize the immune suppressive functions of eosinophils. In this study, an irway allergy mouse model was established. Eosinophils were isolated from the airway tissues using flow cytometry cell sorting. The RAW264.7 cell line was used to test the immune suppressive functions of eosinophils. We observed that eosinophils had immune suppressive functions manifesting inhibiting immune cell proliferation and cytokine release from other immune cells. The eosinophil's immune suppressive functions were mediated by eosinophil-derived molecules, such as eosinophil peroxidase (EPX) and major basic protein (MBP). The expression of Ras-like protein in the brain 27a (Rab27a) was detected in eosinophils, which controlled the release of MBP and EPX by eosinophils. Eosinophil mediators had two contrast effects on inducing inflammatory responses or rendering immune suppressive effects, depending on the released amounts. Administration of an inhibitor of Rab27a at proper dosage could alleviate experimental airway allergy. To sum up, eosinophils have immune suppressive functions and are also inflammation inducers. Rab27a governs the release of EPX and MBP from eosinophils, which leads to immune suppression or inflammation. Modulation of Rab27a can alleviate airway allergy responses by modulating eosinophil's immune suppressive functions, which has the translational potential for the management of eosinophil-related diseases.

Frequency and Correlation of Peripheral and Tissue Eosinophilia with Clinical Manifestations in Patients with Bullous Pemphigoid

INTRODUCTION

Bullous pemphigoid (BP) is an autoimmune disease involving the sub-epidermal layer. Eosinophilia may play a role in the pathogenesis of BP.

OBJECTIVES

We aimed to investigate the correlation between dermal or peripheral eosinophilia with clinical presentations in patients with BP.

METHODS

This cross-sectional study was conducted on 108 BP patients from January 2010 to September 2019. Clinical data were recovered. Skin biopsies were re-evaluated, and the Bullous Pemphigoid Disease Area Index (BPDAI) severity score was calculated. Finally, the relationship between clinical features of BP and dermal or peripheral eosinophilia was analyzed.

RESULTS

A total number of 108 patients were included in this study. Thirty-five were excluded due to our exclusion criteria. Finally, data from 73 patients were analyzed. Fifty-seven point five percent of the population was female. There was a significant direct correlation (r = 0.33) between BPDAI severity score and tissue eosinophilia (P = 0.03). No significant relationship was found between BPDAI severity score and peripheral eosinophilia (P = 0.52). There were significant positive correlations between tissue eosinophilia with absolute serum eosinophil count (P = 0.002; r = 0.49) and percentage (P < 0.0001; r = 0.89).

CONCLUSIONS

This study revealed significant relationships between tissue eosinophilia and BP severity. These findings could be useful in clinical practice. The possible role of eosinophils in BP clinical features should be considered as a promising help for better diagnosis and treatment.

Immune cells in skin inflammation, wound healing, and skin cancer

Given the self-evident importance of cutaneous immunity in the maintenance of body-surface homeostasis, disturbance of the steady-state skin is inextricably intertwined with dysfunction in cutaneous immunity. It is often overlooked by people that skin, well-known as a solid physical barrier, is also a strong immunological barrier, considering the abundant presence of immune cells including lymphocytes, granulocytes, dendritic cells, and macrophages. What's more, humoral immune components including cytokines, immunoglobulins, and antimicrobial peptides are also rich in the skin. This review centers on skin inflammation (acute and chronic, infection and aseptic inflammation), wound healing, and skin cancer to elucidate the elaborate network of immune cells in skin diseases.

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.

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.

Dupilumab effectively and rapidly treats bullous pemphigoid by inhibiting the activities of multiple cell types

Background

Bullous pemphigoid (BP) is an autoimmune skin-blistering disease. Systemic corticosteroids remain the first line treatment for moderate-to-severe BP with the potential for severe adverse events. Dupilumab has emerged as an alternative option for BP patients.

Objective

We evaluated the efficiency and safety of dupilumab on BP treatment and explored a mode of drug action in depth.

Methods and results

A multicenter retrospective cohort included 20 BP patients who received dupilumab with or without systemic corticosteroid in dupilumab group, and 20 matched BP patients who received corticosteroid alone in conventional group. Serum samples were collected from 20 patients (10 from dupilumab group and 10 from conventional group) at baseline and week 4. Compared to systemic corticosteroid alone, dupilumab with or without systemic corticosteroid was similarly efficacious in clinical remission at week4 (complete remission plus partial remission: 100%) and week24 (complete remission plus partial remission:100%), but allowing significant decreases in the cumulative doses of corticosteroids with reducing the incidence of adverse events. However, dupilumab did not decrease BP180 antibody despite an obvious clinical improvement. Comparative plasma proteomic analysis performed before and after treatment in 3 BP patients from dupilumab group revealed that drug use was associated with 30 differentially expressed proteins, including 26 down-regulated and 4 up-regulated proteins. The former consisted of immune related proteins involved in T/B cell interactions (inducible T-cell co-stimulator ligand, ICOSL) and in the activation of eosinophils (PRG2), mast cells (S100A12), and complement (CR2). TARC and ICOSL levels correlated with BP severity in patients who received either dupilumab or conventional treatment.

Conclusion

Dupilumab has similar efficacy in treating BP as conventional drugs, by inhibiting the activities of many types of immune cells and complement, and regulating the interactions between T and B cells.

Concomitant use of dupilumab with glucocorticoid in bullous pemphigoid reduces disease severity: A preliminary study

OBJECTIVE

To retrospectively analyze the efficacy and safety of dupilumab in the treatment of bullous pemphigoid.

METHODS

From October 2020 to October 2022, the medical records of patients with bullous pemphigoid who were treated with dupilumab in our department were collected retrospectively to analyze the therapeutic effect and changes in laboratory indexes.

RESULTS

The records of a total of 11 patients with bullous pemphigoid who were treated with dupilumab was reviewed. Within 2 weeks of the treatment, 10 (90.9%) of the 11 patients had complete or substantial control of the disease. The BPDAI scores of the patients decreased from baseline 113 (62, 181) to 37 (6, 130) at 2 weeks (p = .001) and 4 (0, 37) at 12 weeks after treatment (p < .001). In the 11 patients treated with dupilumab, the relief time of pruritus was 0-3 days (0.5, 7) days, and the pruritus was significantly alleviated after 2 weeks (t = 15.925, p < .001). The DLQI score decreased from (25.5 ± 2.5) before treatment, to (11.8 ± 4.4) at 2 weeks (t = 10.764, p < .001) and (2.1 ± 1.9) at 12 weeks (t = 30.038, p < .001). The patients had high eosinophil counts, high serum IgE levels, low serum total protein levels, and abnormal blood coagulation function. The aforementioned indicators gradually returned to normal after treatment. No adverse reactions occurred during the treatment.

CONCLUSION

Dupilumab can effectively control the condition of bullous pemphigoid, efficiently relieve pruritus symptoms, and is relatively safe.

Eosinophils, Basophils, and Neutrophils in Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering skin disease, of which the incidence has increased in recent years. BP is characterized by circulating IgG and IgE autoantibodies against the hemidesmosomal proteins BP180 and BP230. Although autoantibodies trigger inflammatory cascades that lead to blister formation, effector cells and cell-mediated autoimmunity must also be considered as important factors in the pathogenesis of BP. The aim of this review is to outline the current knowledge on the role of eosinophils, basophils, and neutrophils in BP.

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.

Interleukin-36 cytokines are overexpressed in the skin and sera of patients with bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous disease, characterized by autoantibodies targeting BP180 and BP230. The role of interleukin (IL)-36, a potent chemoattractant for granulocytes, in BP remains elusive.The expression of IL-36 cytokines (IL-36α, β, γ) and their antagonists (IL-36Ra and IL-38) was analysed in the skin and serum samples of patients with BP (n = 31), psoriasis (n = 10) and healthy controls (HC) (n = 14) by quantitative polymerase chain reaction and enzyme linked immunosorbent assay, respectively. Skin and serum levels of all cytokines were correlated with the Bullous Pemphigoid Disease Area Index (BPDAI) score and with the serum concentration of pathogenic antibodies.IL-36α, IL-36β, IL-36γ and IL-36Ra were significantly (p < 0.05) overexpressed in BP skin compared to HC, without remarkable differences relative to psoriasis skin. The expression of IL-38 was significantly (p < 0.05) higher in BP compared to psoriasis skin.IL-36α and γ, but not β, serum concentrations were significantly (p < 0.05) higher in BP compared to HC. IL-36γ was significantly (p < 0.05) more expressed in the serum of psoriasis patients than BP. The serum concentration of IL-36Ra and IL-38 were similar between BP and HC, while IL-38 serum levels were significantly (p < 0.05) higher in BP compared to psoriasis patients. Serum IL-36α correlated significantly with BPDAI (r = 0.5 p = 0.001).IL-36 agonists are increased in BP patients, both locally and systemically. Serum IL-36α might represent a potential biomarker for BP. An inefficient balance between IL-36 agonists and antagonists is likely to occur during BP inflammation.

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.

Associations between bullous pemphigoid and hematological diseases: Literature review on mechanistic connections and possible treatments

Bullous pemphigoid is an autoimmune blistering disorder that primarily occurs in elderly patients. Reports indicate that BP coexists with various hematological diseases, including acquired hemophilia A, hypereosinophilic syndrome, aplastic anemia, autoimmune thrombocytopenia, and hematological malignancies. Early identification of these comorbidities contributes to a better control and reduced mortality. This article details the atypical clinical manifestations of BP when associated with hematological diseases, specific diagnostic strategies, underlying mechanistic connections, and possible treatments. Cross-reactivity between autoantibodies and exposed abnormal epitopes, shared cytokines and immune cells, together with genetic susceptibility are the most common connections between BP and hematological diseases. Patients were most often successfully treated with oral steroids combined with medications specifically targeting the hematological disorders. However, the individual comorbidities require specific considerations.

The cytokine milieu of bullous pemphigoid: Current and novel therapeutic targets

Bullous pemphigoid (BP) is the most common autoimmune bullous disease, characterized by severe pruritus and skin blistering. The loss of tolerance against Collagen XVII, also referred to as BP180, is the main pathogenic event of BP, leading to production of IgG autoantibodies which mainly target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. A complex inflammatory network is activated upon autoantibody binding to the basement membrane zone; this inflammatory loop involves the complement cascade and the release of several inflammatory cytokines, chemokines and proteases from keratinocytes, lymphocytes, mast cells and granulocytes. Collectively, these events disrupt the integrity of the dermal-epidermal junction, leading to subepidermal blistering. Recent advances have led to identify novel therapeutic targets for BP, whose management is mainly based on the long-term use of topical and systemic corticosteroids. As an example, targeting type-2 T-helper cell-associated cytokines, such as Interleukin-4 and interleukin-13 has shown meaningful clinical efficacy in case series and studies; targeting IL-17 and IL-23 has also been tried, owing to an important role of these cytokines in the chronic maintenance phase of BP. In this review article, we discuss the complex cytokine milieu that characterized BP inflammation, highlighting molecules, which are currently investigated as present and future therapeutic targets for this life-threatening disease.

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.

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.

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.

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.

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.

Eosinophils and associated parameters in different types of skin diseases related to elevated eosinophil levels

Background

Eosinophils, basophils, white blood cells (WBC), and immunoglobulin E (IgE) play major roles in the pathogenesis of atopic dermatitis (AD), bullous pemphigoid (BP), drug reaction with eosinophilia and systemic symptoms (DRESS), and hypereosinophilic syndrome (HES). This study aimed to describe these parameters in different skin diseases and provide further information concerning the underlying pathogenesis.

Methods

A cross-sectional study of blood test results, including WBC count, peripheral eosinophil count, peripheral basophil/WBC percentage, and IgE level, from 115 cases of AD, 75 cases of BP, 55 cases of DRESS, 119 cases of HES, and 621 healthy volunteers was performed in China. Data from before and after treatment and the population distribution of different diseases were compared and described.

Results

All participants showed increased peripheral eosinophil counts, eosinophil/WBC ratios, IgE levels, and decreased peripheral basophil counts, with variance among the different disease groups. Peripheral eosinophil counts in HES patients and IgE level in AD patients increased the most prominently. No significant correlation existed among eosinophils, basophils, and IgE. An obvious decrease in eosinophil count was demonstrated after treatment in all 4 diseases.

Conclusions

Eosinophils, basophils, and IgE exert functions in diverse skin diseases, presenting altered peripheral blood test results. In some cases, these changes are demonstrated only in the skin and not in the blood. Compared with the other parameters considered in this study, eosinophils seemed to be a better biomarker for treatment effects, regardless of the disease type.

Successful induction treatment of bullous pemphigoid using reslizumab: a case report

Background

Bullous pemphigoid (BP) is a potentially life-threatening autoimmune blistering disease which is characterized by autoantibodies against hemidesmosomal proteins of the skin and mucous membranes. In recent years, the role of eosinophil and immunoglobulin E autoantibodies have been further elucidated in BP, and have been considered potential therapeutic targets.

Case presentations

A 67-year-old male presented with erythematous bullous eruption. The skin eruption was located on whole body, and suggested BP. Peripheral blood eosinophil count and total immunoglobulin E markedly elevated in initial laboratory findings. Topical and systemic steroid (methylprednisolone 2 mg/kg/day) treatment was started, and his skin symptoms worsened repeatedly, whenever systemic steroid were reduced. On admission day 29, reslizumab (anti-interleukin-5) 3.5 mg/kg was administered intravenously to the patients. The bullous skin lesion began to improve rapidly, and methylprednisolone (8 mg/day) was reduced without any worsening of symptoms during two doses of reslizumab.

Conclusions

We report a case of successful treatment response to reslizumab administration in a patient with BP. Further studies are needed to confirm the role of anti-interleukin-5 as a treatment for BP in the future.

The Association of Bullous Pemphigoid With Atopic Dermatitis and Allergic Rhinitis-A Population-Based Study

BACKGROUND

Although bullous pemphigoid (BP), atopic dermatitis (AD), and allergic rhinitis (AR) are associated with shared pathogenic mechanisms the epidemiological relationship between these conditions remains to be investigated.

OBJECTIVE

To evaluate the bidirectional association of BP with AD and AR.

METHODS

A population-based retrospective cohort study was performed comparing BP patients (n = 3924) with age-, sex-, and ethnicity-matched control subjects (n = 19,280), with respect to incident cases of AD and AR. A case-control design was additionally adopted to assess the odds of BP in individuals with a preexisting diagnosis of AD and AR.

RESULTS

The odds of BP was increased after a preexisting diagnosis of AD (fully adjusted odds ratio, 1.76; 95% confidence interval [CI], 1.44-2.15; P < 0.001) and AR (fully adjusted odds ratio, 1.13; 95% CI, 1.01-1.28; P = 0.047). Patients with BP were at an increased risk of subsequent AD (fully adjusted hazard ratio, 2.00; 95% CI, 1.60-2.51; P < 0.001) but not AR (fully adjusted hazard ratio, 1.00; 95% CI, 0.83-1.20; P = 0.997). Compared with other patients with BP, those with BP and comorbid AD and AR were more frequently managed by adjuvant drugs and long-term systemic and topical corticosteroids and had decreased all-cause mortality.

CONCLUSIONS

A history of AD and AR confers susceptibility to the development of BP. Awareness of this association may be of help for physicians managing patients with these diseases.

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.

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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.

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In recent times, more complex elements of the underlying inflammatory orchestra have been elucidated and are being used to develop targeted immunotherapies.

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The present 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.

The impact of lesional inflammatory cellular infiltrate on the phenotype of bullous pemphigoid

BACKGROUND

The influence of cutaneous cellular infiltration on the phenotype of bullous pemphigoid (BP) remains to be established.

OBJECTIVES

To evaluate the main histopathological characteristics of patients with BP and to assess the association between the composition of lesional inflammatory infiltrate and the various clinical, immunological and immunopathological aspects of the disease.

METHODS

Retrospective study encompassing patients diagnosed with BP throughout the years 2009-2020 in a specialized tertiary referral centre.

RESULTS

The study encompassed 136 patients with BP, of whom 27 (19.9%) demonstrated a cell-poor inflammatory infiltrate in lesional skin specimens. Overall, 78 (57.4%), 71 (52.2%) and 5 (3.7%) specimens were found to include eosinophil-predominant, lymphocyte-predominant and neutrophil-predominant inflammatory infiltrates, respectively. Relative to the remaining patients with BP, those with an eosinophil-predominant inflammatory infiltrate had higher (90.8% vs. 77.2%; P = 0.030) whilst those with a cell-poor inflammatory infiltrate lower (70.3% vs. 88.7%; P = 0.017) seropositivity of anti-BP180 NC16A IgG. The latter subgroup presented with higher prevalence of mucosal involvement (25.9% vs. 8.3%; P = 0.011) and a non-inflammatory clinical phenotype (50.0% vs. 17.1%; P = 0.041). Patients with lymphocyte-predominant inflammatory infiltrate manifested with higher severity BPDAI scores and a lower frequency of the non-inflammatory subtype (11.1% vs. 36.4%; P = 0.035), whilst those with a neutrophilic infiltrate presented with lower mean (SD) levels of anti-BP180 NC16A IgG [269.3 (227.6) vs. 722.7 (1499.6) U/mL; P = 0.003].

CONCLUSIONS

Eosinophil-predominance and high cellularity in the lesional inflammatory infiltrate of BP skin are associated with increased seropositivity of anti-BP180 NC16A IgG. Lymphocyte-predominant infiltrates predict a more severe phenotype, pointing towards a pathogenic role of autoreactive lymphocytes.

Recent developments in the pathogenesis of pruritus in bullous pemphigoid

Bullous pemphigoid (BP) is a common autoimmune bullous disease which mainly affects the elderly. The incidence of BP is gradually increasing and associated with high mortality. This disease is clinically characterized by intensely pruritic and widespread bullous lesions. Alternative therapy options for pruritus in patients with BP are limited primarily because pathophysiological mechanisms of itching in BP are still unclear. This review aims to explain crucial concepts of the pathogenesis of pruritus in BP. Vital findings in recent years will be summarized, and cofactors of the pathogenesis of pruritus will be discussed in detail. We will summarize knowledge on pathogenic factors in the immunologic level conducing to skin pruritus in BP.

What does elevated TARC/CCL17 expression tell us about eosinophilic disorders?

Eosinophilic disorders encompass a large spectrum of heterogeneous diseases sharing the presence of elevated numbers of eosinophils in blood and/or tissues. Among these disorders, the role of eosinophils can vary widely, ranging from a modest participation in the disease process to the predominant perpetrator of tissue damage. In many cases, eosinophilic expansion is polyclonal, driven by enhanced production of interleukin-5, mainly by type 2 helper cells (Th2 cells) with a possible contribution of type 2 innate lymphoid cells (ILC2s). Among the key steps implicated in the establishment of type 2 immune responses, leukocyte recruitment toward inflamed tissues is particularly relevant. Herein, the contribution of the chemo-attractant molecule thymus and activation-regulated chemokine (TARC/CCL17) to type 2 immunity will be reviewed. The clinical relevance of this chemokine and its target, C-C chemokine receptor 4 (CCR4), will be illustrated in the setting of various eosinophilic disorders. Special emphasis will be put on the potential diagnostic, prognostic, and therapeutic implications related to activation of the TARC/CCL17-CCR4 axis.

A Review of Acquired Autoimmune Blistering Diseases in Inherited Epidermolysis Bullosa: Implications for the Future of Gene Therapy

Gene therapy serves as a promising therapy in the pipeline for treatment of epidermolysis bullosa (EB). However, with great promise, the risk of autoimmunity must be considered. While EB is a group of inherited blistering disorders caused by mutations in various skin proteins, autoimmune blistering diseases (AIBD) have a similar clinical phenotype and are caused by autoantibodies targeting skin antigens. Often, AIBD and EB have the same protein targeted through antibody or mutation, respectively. Moreover, EB patients are also reported to carry anti-skin antibodies of questionable pathogenicity. It has been speculated that activation of autoimmunity is both a consequence and cause of further skin deterioration in EB due to a state of chronic inflammation. Herein, we review the factors that facilitate the initiation of autoimmune and inflammatory responses to help understand the pathogenesis and therapeutic implications of the overlap between EB and AIBD. These may also help explain whether corrections of highly immunogenic portions of protein through gene therapy confers a greater risk towards developing AIBD.

Eosinophil Knockout Humans: Uncovering the Role of Eosinophils Through Eosinophil-Directed Biological Therapies

The enigmatic eosinophil has emerged as an exciting component of the immune system, involved in a plethora of homeostatic and inflammatory responses. Substantial progress has been achieved through experimental systems manipulating eosinophils in vivo, initially in mice and more recently in humans. Researchers using eosinophil knockout mice have identified a contributory role for eosinophils in basal and inflammatory processes and protective immunity. Primarily fueled by the purported proinflammatory role of eosinophils in eosinophil-associated diseases, a series of anti-eosinophil therapeutics have emerged as a new class of drugs. These agents, which dramatically deplete eosinophils, provide a valuable opportunity to characterize the consequences of eosinophil knockout humans. Herein, we comparatively describe mouse and human eosinophil knockouts. We put forth the view that human eosinophils negatively contribute to a variety of diseases and, unlike mouse eosinophils, do not yet have an identified role in physiological health; thus, clarifying all roles of eosinophils remains an ongoing pursuit.

A History of Asthma Increases the Risk of Bullous Pemphigoid: Insights from a Large Population-Based Study

BACKGROUND

Bullous pemphigoid (BP) and asthma both share a pathogenic role of eosinophils and immunoglobulin E (IgE) and favorable response for corticosteroids and omalizumab. However, the association between these conditions is yet to be investigated. We sought to estimate the risk of having BP among patients previously diagnosed with asthma and to characterize patients with coexistent BP and asthma.

METHODS

Utilizing the dataset of Clalit Health Services, a population-based case-control study was conducted comparing BP patients (n = 3,924) with age-, sex-, and ethnicity-matched control subjects (n = 19,280) regarding the presence of asthma. Logistic regression models were utilized for univariate and multivariate analyses.

RESULTS

The prevalence of preceding asthma was higher in patients with BP than in control subjects (11.1 vs. 7.9%, respectively; p < 0.001). A history of asthma was associated with a 50% increase in the risk of BP (OR 1.45; 95% CI 1.30-1.62). The association was not altered greatly after adjusting for demographics (adjusted OR 1.43; 95% CI 1.28-1.61) as well as for demographics and comorbidities (adjusted OR 1.40; 95% CI 1.25-1.57). The average (SD) latency between the diagnosis of asthma and the development of BP was 12.5 (14.7) years. When compared with other patients with BP, those with a dual diagnosis of BP and asthma were older, had higher BMI, and were more frequently managed by corticosteroids and immunosuppressive and immunomodulatory adjuvants.

CONCLUSIONS

Asthma confers a predisposition to the development of BP. Awareness of this association may be of help for physicians managing patients with BP and asthma. Further research is required to elucidate the mechanism underlying this observation.

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.

Psychiatric comorbidity in individuals with bullous pemphigoid and all bullous disorders in the Danish national registers

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune blistering skin disease that takes a profound physical and mental toll on those affected. The aim of the study was to investigate the bidirectional association between BP and all bullous disorders (ABD) with a broad array of psychiatric disorders, exploring the influence of prescribed medications.

METHODS

This nationwide, register-based cohort study encompassed 6,470,450 individuals born in Denmark and alive from 1994 to 2016. The hazard ratios (HRs) of a subsequent psychiatric disorder in patients with BP/ABD and the reverse exposure and outcome were evaluated.

RESULTS

Several psychiatric disorders were associated with increased risk of subsequent BP (4.18-fold for intellectual disorders, 2.32-fold for substance use disorders, 2.01-fold for schizophrenia and personality disorders, 1.92-1.85-1.49-fold increased risk for organic disorders, neurotic and mood disorders), independent of psychiatric medications. The association between BP and subsequent psychiatric disorders was not significant after adjusting for BP medications, except for organic disorders (HR 1.27, CI 1.04-1.54). Similar results emerged with ABD.

CONCLUSION

Psychiatric disorders increase the risk of a subsequent diagnosis of BP/ABD independent of medications, whereas medications used for the treatment of BP/ABD appear to account for the subsequent onset of psychiatric disorders. Clinically, an integrated approach attending to both dermatological and psychiatric symptoms is recommended, and dermatologists should remain vigilant for early symptoms of psychiatric disorders to decrease mental health comorbidity.

Eosinophilic Dermatoses: Recognition and Management

Eosinophilic dermatoses encompass a broad spectrum of diseases of different etiologies hallmarked by eosinophilic infiltration of the skin and/or mucous membranes, with or without associated blood eosinophilia. The wide range of dermatological manifestations of this spectrum, including nodules and plaques, pustules, blisters, ulcers, and urticarial lesions, is reflected in a non-univocal classification system. We identified six groups of eosinophilic dermatoses based on the predominant anatomic level of involvement: (1) epidermal; (2) of the dermal-epidermal junction; (3) dermal; (4) of the hypodermis and muscle fascia; (5) of the pilosebaceous unit; and (6) vascular/perivascular. We review clinicopathologic features and management of diseases belonging to each group, particularly: (1) pemphigus herpetiformis and atopic dermatitis as prototypes of the epidermal group; (2) bullous pemphigoid as prototypic eosinophilic dermatosis of the dermal-epidermal junction; (3) eosinophilic cellulitis (Wells syndrome), hypereosinophilic syndromes, Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, eosinophilic dermatosis of hematologic malignancy and chronic spontaneous urticaria as paradigmatic dermal eosinophilic dermatoses; (4) eosinophilic fasciitis as an eosinophilic dermatosis with predominant involvement of the hypodermis and muscle fascia; (5) eosinophilic pustular folliculitis as a model of the pilosebaceous unit involvement; and (6) granuloma faciale, angiolymphoid hyperplasia with eosinophilia, and eosinophilic granulomatosis with polyangiitis, belonging to the vascular/perivascular group.

Total IgE, eosinophils, and interleukins 16, 17A, and 23 correlations in severe bullous pemphigoid and treatment implications

Bullous pemphigoid (BP) patients are predominantly above 70 years of age, with limited tolerance to the side effects of the immunosuppressive drugs. Advancements in our understanding of the pathophysiology of BP have led to the development of molecules which target specific pathways involved in induction and perpetuation of disease. Patients with BP Disease Area Index above 60 and less than 100 were split into two groups-one with high and the other with normal levels of IgE. The tested parameters included eosinophils' count, total IgE serum level, and interleukins (IL) 16, 17A, and 23 counts in the peripheral blood and skin bulla serum, before any therapeutic intervention. Thirty individuals fulfilled the criteria for enrollment. Patients with high IgE blood serum levels had significantly higher levels of IL17A and normal IL23 levels in blood and bulla serum. Patients with normal serum IgE levels had slightly higher IL23 levels in blood and bulla serum. The eosinophil count was positively related to IL17 blood serum level and negatively related to IL23. IL16 did not differ in the two groups. BP patients may represent a group of patients benefiting most substantially from the introduction of nonimmunosuppressive therapeutics into the treatment regimens for their disease. Clinical criteria and immune biomarkers are needed for making the best therapeutic choice.

Eosinophils in Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disorder with substantial morbidity and mortality. BP is regarded as a disorder driven by IgG due to BP180 and BP230 IgG autoantibodies, yet, new advances highlight the function of eosinophils and IgE autoantibodies in BP. Evidence supports that eosinophils are involved in BP pathogenesis, notably, these include the presence of IL-5, eotaxin, and eosinophil-colony stimulating factor in blister fluid, peripheral blood eosinophilia is present in nearly 50% of affected patients, eosinophils are found against the dermo-epidermal junction (DEJ) when BP serum is present, metalloprotease-9 is secreted by eosinophils at blister sites, blister fluid of BP patients contains eosinophil granule proteins which are located along the lamina lucida of the BMZ in patients with BP and correspond with disease clinically, eosinophil extracellular traps (EET) have been linked to DEJ splitting, IL-5 activated eosinophils cause DEJ separation when BP serum is present, and eosinophils are requisite to drive anti-BP180 IgE mediated blistering of the skin. Yet, the mechanism whereby eosinophils contribute to the pathogenesis of BP remains to be explored. In this review, we examine the role of eosinophils in BP while offering a basis to explain the pathomechanisms of eosinophils in BP.

Neutrophil-predominant bullous pemphigoid induced by checkpoint inhibitors: A case series

Checkpoint inhibitors have been revolutionary in the treatment of metastatic melanoma, non-small-cell lung cancer, and renal cell carcinoma. By restricting negative feedback of T-cells, checkpoint inhibitors allow the immune system to identify and destroy malignant cells. This enhanced immune response is efficacious in the treatment of the aforementioned malignancies; however, it may lead to immune-related adverse events. Bullous pemphigoid (BP) is a well-documented cutaneous adverse reaction of checkpoint inhibitors, with a majority of cases reporting an eosinophil-predominant or mixed inflammatory infiltrate. We report two cases of neutrophil-predominant BP presenting in patients on checkpoint inhibitors.

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.