Reactivity against the BP180 ectodomain in patients with bullous pemphigoid, mucous membrane pemphigoid, multiple sclerosis and Parkinson disease.

The 16th non-collagenous domain (NC16A) of BP180 is the main antigenic target of autoantibodies in bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP). Commercially available assays detect serum autoantibodies against NC16A in the majority of BP (80%-90%) and in approximately 50% of MMP patients. However, a standardized test system for detecting antibodies against other regions of BP180 is still lacking. Moreover, anti-BP180 autoantibodies have been found in neurological conditions such as multiple sclerosis and Parkinson disease. This study aimed at identifying primary epitopes recognized by BP autoantibodies on the BP180 ectodomain. Serum samples of 51 BP and 30 MMP patients both without anti-NC16A reactivity were included along with 44 multiple sclerosis and 75 Parkinson disease sera. Four overlapping His-tagged proteins covering the entire BP180 ectodomain (BP180(ec)1-4) were cloned, expressed, purified and tested for reactivity by immunoblot. IgG antibodies to BP180(ec)3 were detected in 98% of BP, 77% of MMP and 2% of normal human sera. Only weak reactivity was detected for neurological diseases against BP180(ec)1, BP180(ec)2 and BP180(ec)4, in 3%, 11% and 7% of tested multiple sclerosis sera, respectively. 8% of Parkinson disease sera reacted with BP180(ec)2 and 9% with BP180(ec)4. In conclusion, this study successfully identified epitopes recognized by BP autoantibodies outside the NC16A domain in pemphigoid diseases. These findings contribute to a better understanding of the immune response in BP and MMP with potential implications for a future diagnostic assay for NC16A-negative pemphigoid patients.

Single-cell transcriptomics analysis of bullous pemphigoid unveils immune-stromal crosstalk in type 2 inflammatory disease.

Bullous pemphigoid (BP) is a type 2 inflammation- and immunity-driven skin disease, yet a comprehensive understanding of the immune landscape, particularly immune-stromal crosstalk in BP, remains elusive. Herein, using single-cell RNA sequencing (scRNA-seq) and in vitro functional analyzes, we pinpoint Th2 cells, dendritic cells (DCs), and fibroblasts as crucial cell populations. The IL13-IL13RA1 ligand-receptor pair is identified as the most significant mediator of immune-stromal crosstalk in BP. Notably, fibroblasts and DCs expressing IL13RA1 respond to IL13-secreting Th2 cells, thereby amplifying Th2 cell-mediated cascade responses, which occurs through the specific upregulation of PLA2G2A in fibroblasts and CCL17 in myeloid cells, creating a positive feedback loop integral to immune-stromal crosstalk. Furthermore, PLA2G2A and CCL17 contribute to an increased titer of pathogenic anti-BP180-NC16A autoantibodies in BP patients. Our work provides a comprehensive insight into BP pathogenesis and shows a mechanism governing immune-stromal interactions, providing potential avenues for future therapeutic research.

Pemphigoid diseases in patients with end-stage kidney diseases: pathogenesis and treatment.

Background: Pemphigoid diseases constitute a group of autoimmune blistering disorders characterized by subepithelial blistering. The association between pemphigoid diseases and both end-stage kidney disease (ESKD) and its treatment is notable. However, there is limited evidence about the management of pemphigoid diseases in patients with ESKD. This systematic review compiled case reports and relevant studies, summarized the underlying mechanisms of pemphigoid diseases in patients with ESKD, and summarized the efficacy of various therapies. Methods: A systematic search of PubMed and Embase was performed for articles published between 1982 to June 2, 2024. Results: Fifty-three case reports and eight relevant studies were included. Triggers for pemphigoids in patients with ESKD included materials used to treat ESKD, immune dysregulation of patients with ESKD, and rejection of renal allograft. Treatment for these patients included removing triggers, as well as administering of corticosteroids, mycophenolate mofetil (MMF), tetracyclines, rituximab, methotrexate, dapsone, azathioprine, cyclosporine, intravenous immunoglobin (IVIG), plasmapheresis, and Janus kinase inhibitors. Conclusion: Removing triggers is the most effective strategy. Despite their suboptimal efficacy, corticosteroids remain the most commonly used agents in this patient population. MMF, tetracyclines, and rituximab are less used but with benefits. There are significant adverse effects associated with methotrexate treatment. Other treatment may also be beneficial and require further investigation. These findings may enable clinicians to optimize the therapeutic approach for these patients.

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

BACKGROUND: Bullous pemphigoid (BP), the most common subepidermal autoimmune blistering disease, is classically defined by the presence of IgG autoantibodies directed against the hemidesmosomal proteins BP180 (type XVII collagen) and BP230 and the predominance of skin lesions. Several studies have addressed the role of anti-BP180 IgE in patients and experimental models, while data on anti-BP230 IgE are scarce. OBJECTIVE: To assess anti-BP230 IgE level by ELISA in BP sera and to correlate it with disease severity and clinical characteristics. METHODS: BP sera underwent anti-BP230 IgE ELISA and Western blotting against human BP230 fragments. RESULTS: We demonstrate that 36/154 (23%) of BP sera were positive for anti-BP230 IgE. Anti-BP230 IgE levels had no correlation with clinical phenotype or disease activity per se. Interestingly, anti-BP230 IgE was significantly associated with disease activity within individuals during the course of the disease. Additionally, anti-BP230 IgE and total IgE levels showed a significant correlation. Notably, anti-BP230 IgG correlated interindividually with disease activity. By Western blotting, the C-terminal domain of BP230 fragments (C2; amino acids 2024-2349 and C3; amino acids 2326-2649), provided the best serological assay for anti-BP230 IgE detection. CONCLUSION: As a complementary tool, IgE immunoblotting is recommended to obtain an optimal serological diagnosis, particularly in patients with severe disease without IgG reactivity by BP180- or BP230-specific ELISA. Although the detection of serum anti-BP230 IgE is not of major diagnostic significance, it may be relevant for therapeutic decisions, e.g., for anti-IgE-directed treatment, which has been successfully used in case series of BP.

Single-cell sequencing reveals distinct immune cell features in cutaneous lesions of pemphigus vulgaris and bullous pemphigoid.

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are two common subtypes of autoimmune bullous disease (AIBD). The key role of circulating autoreactive immune cells contributing to skin damage of AIBD has been widely recognized. Nevertheless, the immune characteristics in cutaneous lesions remain unclear. Here, we performed single-cell RNA sequencing (scRNA-seq) and single-cell VDJ sequencing (scRNA-seq) to generate transcriptional profiles for cells and T/B cell clonetype in skin lesions of BP and PV. We found that the proportions of NK&T, macrophages/ dendritic cells, B cells, and mast cells increased in BP and PV lesions. Then, BP and PV cells constituted over 75% of all myeloid cell subtypes, CD4+ T cell subtypes and CD8+ T cell subtypes. Strikingly, CD8+ Trm was identified to be expanded in PV, and located in the intermediate state of the pseudotime trajectory from CD8+ Tm to CD8+ Tem. Interestingly, CD8+ Tem and CD4+ Treg highly expressed exhaustion-related genes, especially in BP lesions. Moreover, the enhanced cell communication between stromal cells and immune cells like B cells and macrophages/ dendritic cells was also identified in BP and PV lesions. Finally, clone expansion was observed in T cells of BP and PV compared with HC, while CD8+ Trm represented the highest ratio of hyperexpanded TCR clones among all T cell subtypes. Our study generally depicts a large and comprehensive single-cell landscape of cutaneous lesions and highlights immune cell features in BP and PV. This offers potential research targets for further investigation.

Lichen planus pemphigoides with predominant mucous membrane involvement: a series of 12 patients and a literature review.

Background: Lichen planus pemphigoides (LPP), an association between lichen planus and bullous pemphigoid lesions, is a rare subepithelial autoimmune bullous disease. Mucous membrane involvement has been reported previously; however, it has never been specifically studied. Methods: We report on 12 cases of LPP with predominant or exclusive mucous membrane involvement. The diagnosis of LPP was based on the presence of lichenoid infiltrates in histology and immune deposits in the basement membrane zone in direct immunofluorescence and/or immunoelectron microscopy. Our systematic review of the literature, performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, highlights the clinical and immunological characteristics of LPP, with or without mucous membrane involvement. Results: Corticosteroids are the most frequently used treatment, with better outcomes in LPP with skin involvement alone than in that with mucous membrane involvement. Our results suggest that immunomodulators represent an alternative first-line treatment for patients with predominant mucous membrane involvement.

Targeting antibody-mediated complement-independent mechanism in bullous pemphigoid with diacerein.

BACKGROUND: Bullous pemphigoid (BP) is an antibody-mediated blistering disease predominantly affecting the elderly. The pathogenesis involves both complement-dependent and complement-independent mechanisms. The therapeutic potential of targeting complement-independent mechanism has not yet been determined. The mainstay of treatment, corticosteroid, has many side effects, indicating the needs of better treatments. OBJECTIVE: We tempted to establish an in vitro model of BP which resembles complement-independent mechanism and to examine the therapeutic potential of a novel anti-inflammatory agent, diacerein. METHODS: Cultured HaCaT cells were treated with purified antibodies from BP patients, with or without diacerein to measure the cell interface presence of BP180, protein kinase C, and the production of proinflammatory cytokines. An open-label, randomized, phase 2 trial was conducted to compare topical diacerein and clobetasol ointments in patients with mild-to-moderate BP (NCT03286582). RESULTS: The reduced presentation of BP180 at cell interface after treating with BP autoantibodies was noticed in immunofluorescence and western blotting studies. The phenomenon was restored by diacerein. Diacerein also reduced the autoantibody-induced increase of pro-inflammatory cytokines. Reciprocal changes of BP180 and protein kinase C at the cell interface were found after treating with BP autoantibodies. This phenomenon was also reversed by diacerein in a dose-dependent manner. The phase 2 trial showed that topical diacerein reduced the clinical symptoms which were comparable to those of topical clobetasol. CONCLUSION: Diacerein inhibited BP autoantibody-induced reduction of BP180 and production of proinflammatory cytokines in vitro and showed therapeutic potential in patients with BP. It is a novel drug worthy of further investigations.

Low pH condition impairs BP-IgG binding to the basement membrane zone.

Bullous pemphigoid (BP), an autoimmune subepidermal blistering disease, shows tense blisters associated with urticarial erythema. Tissue-bound Immunoglobulin G (IgG) at the basement membrane zone (BMZ) detected by direct immunofluorescence (DIF) is strong evidence for a diagnosis of BP. The sensitivity of DIF is higher in complement component 3 (C3) than in IgG, but the reason for this different sensitivity is not fully understood. In this study, we performed several ex vivo studies to investigate the possible mechanism of IgG negativity and C3 positivity at the BMZ by DIF in some BP cases. First, sera from BP patients showing IgG negativity by DIF were found to clearly react to the BMZ in their own DIF skin samples. Next, indirect immunofluorescence (IIF) was performed using sera diluted with different pH phosphate-buffered saline (PBS), pH 7.4, 6.0, and 3.0. Patients' sera diluted with pH 7.4 PBS showed linear staining at the BMZ, but sera diluted with pH 6.0 PBS and pH 3.0 PBS showed lower fluorescence intensities. Finally, sections of skin from BP patients were pre-incubated with different pH PBS (pH 3.0, 6.0, and 7.4), followed by staining with anti-human IgG and C3. The fluorescence intensities were notably lower for IgG and C3 that had been pre-incubated with pH 3.0 PBS and pH 6.0 PBS than for IgG and C3 that had been pre-incubated with pH 7.4 PBS. These results suggest that a low pH condition hinders the binding of autoantibodies to the BMZ, that is, the drop in tissue pH induced by inflammation inhibits autoantibodies from depositing at the BMZ. Furthermore, the drop in tissue pH causes tissue-bound autoantibodies to detach from the BMZ. Complement fragments are activated not only on IgG but also on the cell surface of cells close to IgG during complement activation. IgG may detach from the BMZ under low pH condition induced by inflammation, but some complement fragments remain at the BMZ. These phenomena may help to explain why C3 is more sensitive than IgG when DIF is used to diagnose BP.

A case of anti-laminin γ1 (p200) pemphigoid developed after dipeptidyl peptidase-4 inhibitor administration.

A 73-year-old man with diabetes mellitus was referred to our department for ultraviolet treatment for erythematous skin lesions with itching. On dipeptidyl peptidase-4 inhibitor (DPP-4i) sitagliptin (Januvia®) for diabetes mellitus, the erythematous skin lesions appeared and spread to the whole body. At the initial visit, erythema multiforme-like skin lesions with crusts were observed on the trunk and extremities, and the patient was suspected to have drug eruption. Histopathology demonstrated eosinophilic infiltration in the superficial dermis and inflammatory cell infiltration in the epidermis. Sitagliptin was discontinued, and erythematous lesions improved with oral prednisolone. Thereafter the patient was treated with phototherapy and  betamethasone sodium phosphate infusion for residual prurigo. However, blistering skin lesions appeared 5 months later. Histopathological findings were subepidermal blisters with eosinophilic abscess, and bullous pemphigoid was suspected. CLEIAs for autoantibodies to desmoglein 1 (Dsg1), Dsg3 and BP180 were negative. Direct immunofluorescence showed linear depositions of immunoglobulin G (IgG) and C3 at the epidermal basement membrane zone, and indirect immunofluorescence detected IgG anti-epidermal basement membrane zone antibodies, reacting with the dermal side of 1M NaCl-split normal human skin. IgG antibodies reacted with 200 kDa laminin γ1 (p200) by immunoblotting using dermal extracts. These results indicated that this patient was diagnosed with anti-laminin γ1 (p200) pemphigoid developed after DPP-4i administration. Although reports of DPP-4i-related bullous pemphigoid have accumulated, cases of anti-laminin γ1 (p200) pemphigoid developed after DPP-4i administration are rarely reported.

The Syk Inhibitor Entospletinib Abolishes Dermal-Epidermal Separation in a Fully Human Ex Vivo Model of Bullous Pemphigoid.

Bullous pemphigoid (BP) is an autoantibody-mediated blistering skin disease characterized by local inflammation and dermal-epidermal separation, with no approved targeted therapy. The Syk tyrosine kinase is critical for various functions of the immune response. Second-generation Syk inhibitors such as entospletinib are currently being tested for hematological malignancies. Our aim was to test the effect of entospletinib in a fully human model system of BP. Incubating BP serum-treated human frozen skin sections with normal human granulocytes and fresh plasma triggered dermal-epidermal separation that was dependent on complement, NADPH oxidase, and protease activity. Entospletinib dramatically reduced dermal-epidermal separation with a half-maximal inhibitory concentration of ≈16 nM. Entospletinib also reduced ROS production, granule release, and spreading of human granulocytes plated on immobilized immune complexes consisting either of a generic antigen-antibody pair or of recombinant collagen type XVII (BPAg2) and BP serum components (supposedly autoantibodies). However, entospletinib did not affect the chemotactic migration of human granulocytes or their responses to nonphysiological stimulation by phorbol esters. Entospletinib had no effect on the survival of granulocytes either. Taken together, entospletinib abrogates dermal-epidermal separation, likely through inhibition of granulocyte responsiveness to deposited immune complexes. Entospletinib or other Syk inhibitors may provide therapeutic benefits in BP.

Bullous pemphigoid and diabetes mellitus: a systematic review and meta-analysis.

We aimed to systematically review and meta-analyze the association between diabetes mellitus (DM) and bullous pemphigoid (BP). Bullous pemphigoid (BP) is a prevalent autoimmune subepidermal blistering disease. Comorbid health conditions like neurological diseases and malignancies have been associated with BP. Growing evidence suggests that type 2 diabetes mellitus (T2DM) may increase the risk of developing BP. This review aims to synthesize this evidence. A systematic literature review was performed using Medline, PubMed, and Scopus in March 2022. Studies exploring the association between BP and DM were included. Data were extracted, and quality was assessed using the Newcastle-Ottawa scale. Meta-analysis was conducted to identify the odds ratio (OR) and 95% confidence intervals (CI) of the association. Seventeen studies were included, most being case-control studies from Europe and Asia. The pooled OR was 2.06 (95% CI: 1.61-2.62), suggesting a significant association between DM and BP. However, strong heterogeneity (I2 = 88%) was observed. Evidence consolidates a significant relationship between DM and BP, potentially due to alterations in the immune system and skin properties caused by diabetes. Strengths of this review include a comprehensive search, rigorous methodology, large sample size, and heterogeneity evaluation. However, varying study quality, potential publication bias, and unaccounted confounding factors present limitations. There is a potential link between T2DM and an increased risk of BP. Further studies are required to understand this association and the underlying mechanisms.

What's new in the pathogeneses and triggering factors of bullous pemphigoid.

Bullous pemphigoid (BP) is a subepidermal blistering disease induced by autoantibodies to type XVII collagen (COL17, also called BP180) and BP230. Previous studies using patients' samples and animal disease models elucidated the complement-dependent and complement-independent pathways of blister formation, the pathogenic roles of immune cells (T and B cells, macrophages, mast cells, neutrophils, eosinophils), and the pathogenicity of IgE autoantibodies in BP. This review introduces the recent progress on the mechanism behind the epitope-spreading phenomenon in BP, which is considered to be important to understand the chronic and intractable disease course of BP, and the pathogenicity of anti-BP230 autoantibodies, mainly focusing on studies that used active disease models. To clarify the pathogenesis of BP, the mechanism behind the breakdown of immune tolerance to BP antigens should be investigated. Recent studies using various experimental models have revealed important roles for regulatory T cells in the maintenance of self-tolerance to COL17 and BP230 as well as in the suppression of inflammation triggered by the binding of antibodies to COL17. Notably, physical stresses such as trauma, thermal burns, bone fractures, irradiation and ultraviolet exposure, some pathologic conditions such as neurological diseases and hematological malignancies, and the use of dipeptidyl peptidase-IV inhibitors and immune checkpoint inhibitors have been reported as triggering factors for BP. These factors and certain underlying conditions such as genetic background, regulatory T-cell dysfunction or aging might synergistically affect some individuals and eventually induce BP. Further studies on the breakdown of self-tolerance and on the identification of key molecules that are relevant to blister formation and inflammation may expand our understanding of BP's etiology and may lead to the development of novel therapeutic approaches.

IL-13 Genetic Susceptibility to Bullous Pemphigoid: A Potential Target for Treatment and a Prognostic Marker.

Background: Bullous pemphigoid (BP) is a senile chronic autoimmune bullous skin disease with a high relapse rate, which significantly impairs patients' quality of life and contributes to disease mortality. This observational case-control study explores the gene polymorphisms of cytokines and their clinical significance in Chinese patients with BP. Methods: IL-1α (rs1800587), IL-1ß (rs16944, rs1143627, rs1143634), IL-4 (rs2243250), IL-6 (rs1800795), IL-10 (rs1800896, rs1800871, rs1800872), IL-13 (rs1800925, rs20541), TNF-α (rs1799964, rs1800630, rs1799724, rs361525), IFN-γ (rs1799964, rs1800630, rs361525, rs1800629, rs4248160, rs1800750), and TGF-ß1 (rs2317130, rs1800469, rs4803457) genes were genotyped in the healthy controls and BP patients, respectively. Expression of these cytokines in serum was measured. Medical profiles of patients, including baseline characteristics and prognosis, were statistically analyzed. Results: We found that IL-1 ß and IL-13 concentrations were higher in the BP patients' sera compared to those in the controls. For IL-13, significant differences were found in the nucleotide ratio/genotype/haploid frequency/haplotype, respectively. IL-13 (rs20541, rs1800925) is related to gender, and the IL-13 genotype was significantly associated with recurrence. Conclusions: BP is associated with IL-13 gene polymorphism and IL-13 concentration is elevated in blood circulation in patients with BP. Our results support that IL-13 is relevant in the pathogenesis of BP, suggesting that IL-13 could potentially represent a promising target for BP therapy and a prognostic marker.

Efficacy and Safety of Dupilumab in Moderate-to-Severe Bullous Pemphigoid.

Background: Bullous pemphigoid (BP) is an autoimmune blistering disorder that predominantly affects the elderly. As the main treatment for BP, systemic corticosteroids are often limited by their side effects. Safer treatment modalities are therefore needed. Dupilumab is a biologic agent used to treat BP in recent years. Methods: Medical records of patients with moderate-to-severe BP were retrospectively reviewed. Twenty-four patients were included (follow-up period: 32 weeks), eight of whom received dupilumab in combination with methylprednisolone and azathioprine (dupilumab group) while the other 16 patients received methylprednisolone and azathioprine (conventional group). Response to dupilumab was evaluated by comparison of several parameters (time to stop new blister formation, time to reduce the systemic glucocorticoids to minimal dose, and total amount of methylprednisolone). Results: The median age of patients in the dupilumab and conventional groups were 64.50 years (range: 22-90 years) and 64.50 years (range: 17-86 years), respectively. The median duration of disease before admission in the dupilumab group was 2 months (range: 1-240 months) and 2.5 months (range: 1-60 months) in the conventional group. The median time to stop new blister formation was 8 days (range: 1-13 days) and 12 days (range: 5-21 days) in patients of the dupilumab and conventional groups, respectively (p = 0.028 by Kaplan-Meier analysis). In addition, the median time to reduce the systemic glucocorticoids to minimal dose (methylprednisolone 0.08 mg/kg/day) was 121.5 and 148.5 days for the dupilumab and conventional therapy groups, respectively (p = 0.0053 by Kaplan-Meier analysis). The median total amount of methylprednisolone (at the time of reaching the minimal dose) used in the dupilumab group was 1,898 mg (range: 1,624-2,932 mg) while the cumulative dose of conventional group was 2,344 mg (range: 1,708-4,744 mg) (p = 0.036 by Mann-Whitney U test). The median total amount of azathioprine (at the time of reaching the minimal dose) used in dupilumab group was 8,300 mg (range: 7,100-10,400 mg) while the total dose of conventional group was 10,300 mg (range: 8,900-14,400 mg) (p = 0.0048 by Mann-Whitney U test). No adverse event related to dupilumab was recorded. Conclusions: Dupilumab in addition to methylprednisolone and azathioprine seems superior to methylprednisolone/azathioprine alone in controlling disease progression and accelerating the tapering of glucocorticoids.