The possible and intriguing relationship between bullous pemphigoid and melanoma: speculations on significance and clinical relevance.

Bullous pemphigoid (BP) is the most common autoimmune bullous disease: it most commonly affects individuals over 70 years old and impacts severely on their quality of life. BP represents a paradigm for an organ-specific autoimmune disease and is characterized by circulating IgG autoantibodies to hemidesmosomal components: BP180 and BP230. While the crucial role of these autoantibodies in triggering BP inflammatory cascade is fully acknowledged, many ancillary etiological mechanisms need to be elucidated yet. Cutaneous melanoma is due to a malignant transformation of skin melanocytes, that produce and distribute pigments to surrounding keratinocytes. Melanoma is the most fatal skin cancer because of its increasing incidence and its propensity to metastasize. Several data such as: i) reported cases of concomitant melanoma and BP; ii) results from association studies; iii) BP onset following immune check-point inhibitors therapy; iv) expression of BP antigens in transformed melanocytes; and vi) circulating autoantibodies to BP antigens in melanoma patients suggest an intriguing, although unproven, possible association between melanoma and BP. However, a possible causative link is still debated and the putative pathogenetic mechanism underlying this association is unclear. This review aims to describe and discuss the possible relationship between BP and melanoma and give an overview of the speculations for or against this association. Of note, if demonstrated, this association could unwrap considerations of clinical relevance that represent new research frontiers.

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.

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.

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.

A case of bullous pemphigoid following administration of anti-IL-31 receptor A antibody.

Bullous pemphigoid (BP), an autoimmune bullous dermatosis, occurs predominantly in older individuals. Nemolizumab, a humanized monoclonal antibody against the interleukin (IL)-31 receptor A, is used to treat severe atopic dermatitis (AD) in Japan. However, it can cause several adverse events, such as exacerbation of AD, erythema, and eosinophilia. Herein, we describe a case of prurigo-type AD developing BP after nemolizumab administration. A 62-year-old man with prurigo-type AD and asthma presented with serious, refractory itching. After nemolizumab injection, his pruritus was relieved for 2 days. However, on day 3, erythema with blisters and erosions suddenly appeared throughout his body. Pathological examination showed typical BP and the patient's serum anti-BP180-NC16a antibody level was 882.5 U/mL. Oral prednisolone (PSL) was initiated and nemolizumab was never used again. Despite high-dose PSL, new blisters continued to develop, with a rapid elevation of anti-BP180-NC16a antibodies to 6930 U/mL. Adding high-dose cyclosporine and intravenous gamma globulin reduced new blister formation after 9 weeks, and PSL and cyclosporine were gradually tapered. Dupilumab, an anti-IL-4 receptor antibody, was initiated after 16 weeks, resulting in continued remission without PSL and cyclosporine. The sudden occurrence of BP in this case suggested that the patient had occult BP before the nemolizumab initiation and that nemolizumab exacerbated BP and made it overt. Blocking the IL-31 pathway may exacerbate inflammation in AD or BP, resulting in the acceleration of blister formation. This may be countered by blocking the IL-4/13 pathway with dupilumab. To our knowledge, this is the first case of nemolizumab-exacerbated BP.

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.

Evaluation of the immune colloidal gold technique for BP180-NC16A-specific antibodies in the quick diagnosis and monitoring of bullous pemphigoid.

BACKGROUND: Bullous pemphigoid (BP) mostly involves elderly patients. The diagnosis of BP requires special immunological tests, which makes some patients unable to be diagnosed and treated timely. OBJECTIVE: The accuracy and application value of immune colloidal gold technique (ICGT) in BP were evaluated. The colloidal gold was conjugated with recombinant BP180 NC16A protein and mouse IgG antibody. As the test and control lines, the mouse-anti-human IgG and goat-anti-mouse IgG, respectively, were blotted on the nitrocellulose membrane. METHODS: 414 serum samples of consecutive patients with suspected BP and 15 samples from healthy donors were recruited. The consistency between ICGT and ELISA, and between serum and plasma/whole blood were evaluated. Subgroup analyses were performed in terms of clinical characteristics. We also followed up 65 BP patients' strip results to explore the predictive value of ICGT. RESULTS: Strong agreements between ICGT and ELISA(κ = 0.902) and between plasma/whole blood and serum samples (κ = 0.980) with good stability were observed. The ICGT achieved sensitivity of 93.9%, and specificity of 97.6%. In subgroup analysis, the sensitivity was significantly higher in older patients (96.3%), and with more typical lesions such as blisters (96.2%) and erosions (92.4%). In follow-up, we also found BP patients who kept ICGT-negative in remission state all got consecutive positive strips 1-3 weeks prior to mild new activity or flare. CONCLUSION: ICGT shows high potential as a rapid and stable option for the diagnosis and monitoring of BP. Further investigations are needed to re-evaluate this technique in a prospective study with a multicenter design.

BP180/Collagen XVII: A Molecular View.

BP180 is a type II collagenous transmembrane protein and is best known as the major autoantigen in the blistering skin disease bullous pemphigoid (BP). The BP180 trimer is a central component in type I hemidesmosomes (HD), which cause the adhesion between epidermal keratinocytes and the basal lamina, but BP180 is also expressed in several non-HD locations, where its functions are poorly characterized. The immunological roles of intact and proteolytically processed BP180, relevant in BP, have been subject to intensive research, but novel functions in cell proliferation, differentiation, and aging have also recently been described. To better understand the multiple physiological functions of BP180, the focus should return to the protein itself. Here, we comprehensively review the properties of the BP180 molecule, present new data on the biochemical features of its intracellular domain, and discuss their significance with regard to BP180 folding and protein-protein interactions.

Plasma levels of D-dimer and fibrin degradation products correlate with bullous pemphigoid severity: a cross-sectional study.

Bullous pemphigoid (BP), the most frequent blistering dermatosis in the elderly, is associated with increased mortality. The severity of BP can be assessed by detecting the anti-BP180 immunoglobulin G (IgG) concentration, but the lab test is not available in many community clinics. BP patients are usually in a hypercoagulable state with increased levels of D-dimer and fibrin degradation products (FDPs). We aimed to evaluate the use of D-dimer and FDPs in assessing BP severity. We compared the levels of plasma D-dimer, plasma FDPs, eosinophil counts, eosinophil cationic protein, and serum anti-BP180 IgG concentration between 48 typical BP patients and 33 Herpes zoster (HZ) patients (control group). Correlational analyses were conducted to determine the relationships between the lab values and common BP severity markers. The plasma D-dimer and FDP levels were higher in BP patients than in HZ controls (D-dimer: 3297 ± 2517 µg/L vs. 569.70 ± 412.40 µg/L; FDP: 9.74 ± 5.88 mg/L vs. 2.02 ± 1.69 mg/L, respectively, P < 0.0001). Significant positive correlations were found between D-dimer/FDP levels and BP severity markers (i.e. anti-BP180 IgG concentration [D-dimer: r = 0.3928, P = 0.0058; FDP: r = 0.4379, P = 0.0019] and eosinophil counts [D-dimer: r = 0.3625, P = 0.0013; FDP: r = 0.2880, P = 0.0472]) in BP patients. We also found an association between FDP and urticaria/erythema lesions (r = 0.3016, P = 0.0372), but no other BPDAI components. In 19 BP patients with complete remission after systemic glucocorticoid treatment, D-dimer and FDP levels decreased post-therapy (D-dimer: 5559 ± 7492 µg/L vs. 1738 ± 1478 µg/L; P < 0.0001; FDP: 11.20 ± 5.88 mg/L vs. 5.13 ± 3.44 mg/L; P = 0.0003), whereas they did not in BP patients with treatment resistant. Plasma D-dimer and FDP are convenient markers to evaluate BP severity assistant on BPDAI and eosinophil counts. FDP is also helpful for inflammatory lesions in BP patients.

Autoreactive Peripheral Blood T Helper Cell Responses in Bullous Pemphigoid and Elderly Patients With Pruritic Disorders.

Bullous pemphigoid (BP) is a prototypic autoimmune disorder of the elderly, characterized by serum IgG autoantibodies, namely anti-BP180 and anti-BP230, directed against components of the basal membrane zone that lead to sub-epidermal loss of adhesion. Pruritus may be indicative of a pre-clinical stage of BP, since a subset of these patients shows serum IgG autoantibodies against BP230 and/or BP180 while chronic pruritus is increasingly common in the elderly population and is associated with a variety of dermatoses. Clinical and experimental evidence further suggests that pruritus of the elderly may be linked to autoimmunity with loss of self-tolerance against cutaneous autoantigens. Thus, the objective of this study was to determine autoreactive T cell responses against BP180 in elderly patients in comparison to patients with BP. A total of 22 elderly patients with pruritic disorders, 34 patients with bullous or non-bullous BP and 34 age-matched healthy controls were included in this study. The level of anti-BP180 and anti-BP230 IgG serum autoantibodies, Bullous Pemphigoid Disease Area Index (BPDAI), and pruritus severity were assessed for all patients and controls. For characterization of the autoreactive T cell response, peripheral blood mononuclear cells were stimulated ex vivo with recombinant BP180 proteins (NH2- and COOH-terminal domains) and the frequencies of BP180-specific T cells producing interferon-γ, interleukin (IL)-5 or IL-17 were subsequently determined by ELISpot assay. Patients with BP showed a mixed Th1/Th2 response against BP180 while autoreactive Th1 cells were identified in a minor subset of elderly patients with pruritic disorders. Furthermore, our T cell characterization revealed that therapeutic application of topical clobetasol propionate ointment in BP patients significantly reduced peripheral blood BP180-specific T cells, along with clinically improved symptoms, strongly suggesting a systemic immunosuppressive effect of this treatment.

More Severe Erosive Phenotype Despite Lower Circulating Autoantibody Levels in Dipeptidyl Peptidase-4 Inhibitor (DPP4i)-Associated Bullous Pemphigoid: A Retrospective Cohort Study.

BACKGROUND: The clinical and immunological profile of patients with dipeptidyl peptidase-4 inhibitor (DPP4i)-associated bullous pemphigoid (BP) is inconsistent in the current literature. OBJECTIVES: The aims were to investigate the clinical and immunological features of patients with DPP4i-associated BP and to examine whether there are intraclass differences between different DPP4i agents. METHODS: A retrospective cohort study was conducted, including all consecutive patients diagnosed with BP throughout the years 2009-2019 in a tertiary referral center. RESULTS: The study encompassed 273 patients with BP (mean age at diagnosis 79.1 ± 9.9 years), of whom 24 (8.8%) were associated with DPP4i. Sitagliptin was the prescribed agent for 17 patients (70.8%), and vildagliptin was prescribed in seven patients (29.2%). Relative to other patients with BP, patients with DPP4i-associated BP had more prominent truncal involvement (95.8% vs. 73.9%; P = 0.017), greater erosion/blister Bullous Pemphigoid Disease Area Index (BPDAI) subscore (29.8 ± 17.4 vs. 20.6 ± 14.4; P = 0.018), and lower levels of anti-BP180 NC16A (279.2 ± 346.1 vs. 572.2 ± 1352.0 U/ml; P = 0.009) and anti-BP230 (25.5 ± 47.8 vs. 128.6 ± 302.9 U/ml; P = 0.009) antibodies. Relative to patients with sitagliptin-associated BP, those with vildagliptin-associated BP had a lower seropositivity rate (57.1% vs. 94.1%, P = 0.031) and lower levels (96.7 ± 139.0 vs. 354.5 ± 376.5; P = 0.023) of anti-BP180 NC16A antibodies, and tended to present with higher erosion/blister BPDAI subscore (36.3 ± 9.6 vs. 25.8 ± 19.7; P = 0.095). CONCLUSIONS: DPP4i-associated BP is characterized by a more severe blistering and erosive presentation despite lower levels of typically pathogenic antibodies.

Autoantibodies Against the Immunodominant Bullous Pemphigoid Epitopes Are Rare in Patients With Dermatitis Herpetiformis and Coeliac Disease.

Dermatitis herpetiformis (DH) is an extraintestinal manifestation of coeliac disease (CD). Patients with DH have an elevated risk of development of another autoimmune blistering skin disease, bullous pemphigoid (BP). In this study we investigated whether patients with DH and CD (mean age for both 49 years) have circulating autoantibodies against BP180, the major BP autoantigen. ELISA tests showed that only a few DH (3/46) and CD (2/43) patients had BP180-NC16A IgG autoantibodies. Immunoblotting found that more than half of the DH samples contained IgG autoantibodies against full-length BP180. Epitope mapping with 13 fusion proteins covering the BP180 polypeptide revealed that in DH and CD patients, IgG autoantibodies did not target the NC16A or other epitopes typical of BP but recognized other intracellular and mid-extracellular regions of BP180. None of the analyzed DH and CD patients with either ELISA or immunoblotting positivity had IgG or IgA reactivity against the cutaneous basement membrane in indirect immunofluorescence analysis or skin symptoms characteristic of BP. Although only a minority of middle-aged DH patients had IgG autoantibodies against the immunodominant epitopes of BP180, our results do not exclude the possibility that intermolecular epitope spreading could explain the switch from DH to BP in elderly patients.