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.

Laminin ß4 is a constituent of the cutaneous basement membrane zone and additional autoantigen of anti-p200 pemphigoid.

BACKGROUND: Anti-p200 pemphigoid is a subepidermal autoimmune blistering disease (AIBD) characterized by autoantibodies against a 200 kDa protein. Laminin γ1 has been described as target antigen in 70% to 90% of patients. No diagnostic assay is widely available for anti-p200 pemphigoid, which might be due to the unclear pathogenic relevance of anti-laminin γ1 autoantibodies. OBJECTIVE: To identify a target antigen with higher clinical and diagnostic relevance. METHODS: Immunoprecipitation, mass spectrometry, and immunoblotting were employed for analysis of skin extracts and sera of patients with anti-p200 pemphigoid (n = 60), other AIBD (n = 33), and healthy blood donors (n = 29). To localize the new antigen in skin, cultured keratinocytes and fibroblasts, quantitative real-time polymerase chain reaction and immunofluorescence microscopy were performed. RESULTS: Laminin ß4 was identified as target antigen of anti-p200 pemphigoid in all analyzed patients. It was located at the level of the basement membrane zone of the skin with predominant expression in keratinocytes. LIMITATIONS: A higher number of sera needs to be tested to verify that laminin ß4 is the diagnostically relevant antigen of anti-p200 pemphigoid. CONCLUSION: The identification of laminin ß4 as an additional target antigen in anti-p200 pemphigoid will allow its differentiation from other AIBD and as such, improve the management of these rare disorders.

Serum reactivity in dermatitis herpetiformis: an international multicentre study.

BACKGROUND: Dermatitis herpetiformis (DH) is a rare gluten-induced skin disorder characterized predominantly by IgA autoantibodies against endomysium, tissue transglutaminase (TG2/tTG), epidermal transglutaminase (TG3/eTG) and deamidated gliadin. To date, circulating autoantibody reactivity has not been systematically described. OBJECTIVES: Characterization of serum reactivities in DH. METHODS: This multicentre international study analysed sera from 242 patients with DH taken at the time of initial diagnosis. DH-specific IgA and IgG serum autoantibodies were analysed by indirect immunofluorescence (IF) on monkey oesophagus, and by enzyme-linked immunosorbent assay (ELISA) based on recombinant TG2/tTG, TG3/eTG and deamidated gliadin (GAF3X). RESULTS: IgA indirect IF microscopy on monkey oesophagus revealed the highest reactivity (84.3%; specificity 100%) followed by IgA TG2/tTG ELISA (78.5%, specificity 99.0%), IgA TG3/eTG ELISA (72.7%, specificity 95.0%) and IgA GAF3X ELISA (69.0%, specificity 98.5%). CONCLUSIONS: Serum IgA and IgG autoantibodies against endomysium, TG2/tTG, TG3/eTG and deamidated gliadin are highly prevalent in DH. Indirect IF microscopy on monkey oesophagus (IgA) provides the highest diagnostic accuracy that can be further enhanced by 4.5% when combined with IgA TG2/tTG ELISA.

Immunoglobulin M pemphigoid.

BACKGROUND: Pemphigoid diseases are a heterogeneous group of autoimmune blistering disorders characterized by predominant deposition of immunoglobulin G or immunoglobulin A autoantibodies against structural proteins of the dermoepidermal junction (DEJ). Sole linear immunoglobulin M (IgM) deposits at the DEJ in pemphigoid diseases have been observed; however, IgM-specific target antigens have not been identified. OBJECTIVE: Characterization of patients with IgM pemphigoid. METHODS: Skin biopsy specimens and sera from IgM-positive patients were assessed using histopathology, direct and indirect immunofluorescence microscopy, enzyme-linked immunosorbent assays, immunoblotting, cryosection assay, complement fixation test, and internalization assays. RESULTS: Tissue-bound linear IgM deposits along the DEJ and circulating IgM autoantibodies against type XVII collagen (Col17) were detected. These circulating IgM autoantibodies showed no complement activating or blister inducing capacity, but the ability of Col17 internalization ex vivo. LIMITATIONS: Limited number of patients. CONCLUSION: This study provides further evidence for the role of IgM autoantibodies in pemphigoid disease and highlights Col17 as a target antigen in IgM pemphigoid.

Survival of Adjuvant Drugs for Treatment of Pemphigus: A Population-based Cohort Study.

Drug survival reflects the real-life efficacy and safety of therapeutic agents. Evidence regarding the durability of adjuvant agents in the treatment of pemphigus is sparse. The aims of this study were to investigate the survival of adjuvant agents used to manage patients with pemphigus, and to identify predictors of treatment dropout. A retrospective population-based cohort study was designed to follow patients with pemphigus managed by adjuvant agents. The study population included 436 patients with pemphigus managed by 608 adjuvant agent courses. The highest median drug survival time was observed for rituximab (43.6 months, 95% confidence interval (95% CI) 5.3-81.9), followed by cyclophosphamide (30.5 months; 95% CI 10.5-50.5), azathioprine (22.9 months; 95% CI 15.6-30.2), and mycophenolate mofetil (20.2 months; 95% CI 10.0-30.4). Compared with azathioprine, cyclosporine (adjusted hazard ratio 2.98; 95% CI 1.57-5.62; p = 0.005) and dapsone (adjusted hazard ratio 1.83; 95% CI 1.07-3.15; p = 0.027) were associated with a significantly increased risk of drug discontinuation. To conclude, rituximab, azathioprine, and mycophenolate mofetil demonstrated better durability, whilst dapsone and cyclosporine were associated with low drug survival and high dropout.

Immunomodulator Galectin-9 is Increased in Blood and Skin of Patients with Bullous Pemphigoid.

Massive recruitment of eosinophils into the dermis is a hallmark of bullous pemphigoid pathogenesis. Identifying the chemoattractant(s) guiding eosinophils into the skin in bullous pemphigoid is a prerequisite to thera-peutic targeting of eosinophil recruitment. Galectin -9 is a potent chemoattractant for eosinophils, but its potential role in bullous pemphigoid is unknown. The aim of this study was to determine the expression levels of galectin-9 in serum and skin of patients with bullous pemphigoid. Galectin-9 levels were significantly elevated in serum of patients with bullous pemphigoid compared with age- and sex-matched controls, but did not correlate with disease activity assessed with the Bullous Pemphigoid Disease Area Index. Galectin-9 expression was also increased in lesional skin of patients with bullous pemphigoid, and was expressed predominantly in eosinophils, neutrophils and keratinocytes. In conclusion, these results support the notion that galectin-9 may play a role in the patho-genesis of bullous pemphigoid.

In situ detection of PR3-ANCA+ B cells and alterations in the variable region of immunoglobulin genes support a role of inflamed tissue in the emergence of auto-reactivity in granulomatosis with polyangiitis.

Circulating anti-neutrophilic cytoplasmic autoantibodies targeting proteinase 3 (PR3-ANCA) are a diagnostic and pathogenic hallmark of granulomatosis with polyangiitis (GPA). It is, however, incompletely understood if inflamed tissue supports presence or emergence of PR3-ANCA+ B cells. In search of such cells in inflamed tissue of GPA, immunofluorescence staining for IgG and a common PR3-ANCA idiotype (5/7 Id) was undertaken. Few 5/7 Id+/IgG+ B cells were detected in respiratory and kidney tissue of GPA. To gain more insight into surrogate markers possibly indicative of an anti-PR3-response, a meta-analysis comprising IGVH and IGVL genes derived from respiratory tract tissue of GPA (231 clones) was performed. Next generation sequencing-based IGHV genes derived from peripheral blood of healthy donors (244.353 clones) and previously published IGLV genes (148 clones) served as controls. Additionally, Ig genes of three murine and five known human monoclonal anti-PR3 antibodies were analyzed. Primary and probably secondary rearrangements led to altered VDJ usage and an extended complementarity determining region 3 (CDR3) of IGHV clones from GPA tissue. Selection against amino acid exchanges was prominent in the framework region of IGHV clones from GPA tissue. The comparison of V(D)J rearrangements and deduced amino acid sequences of the CDR3 yielded no identities and few similarities between clones derived from respiratory tissue of GPA and anti-PR3 antibodies, arguing against a presence of B cells that carry PR3-ANCA-prone Ig genes among the clones. In line with the scarcity of 5/7 Id+ B lymphocytes in GPA tissue, the results suggest that with respect to a local anti-PR3 response, methods detecting rare clones are required.

Determinants of VH1-46 Cross-Reactivity to Pemphigus Vulgaris Autoantigen Desmoglein 3 and Rotavirus Antigen VP6.

Shared VH1-46 gene usage has been described in B cells reacting to desmoglein 3 (Dsg3) in the autoimmune disease pemphigus vulgaris (PV), as well as B cells responding to rotavirus capsid protein VP6. In both diseases, VH1-46 B cells bearing few to no somatic mutations can recognize the disease Ag. This intriguing connection between an autoimmune response to self-antigen and an immune response to foreign Ag prompted us to investigate whether VH1-46 B cells may be predisposed to Dsg3-VP6 cross-reactivity. Focused testing of VH1-46 mAbs previously isolated from PV and rotavirus-exposed individuals indicates that cross-reactivity is rare, found in only one of seven VH1-46 IgG clonotypes. High-throughput screening of IgG B cell repertoires from two PV patients identified no additional cross-reactive clonotypes. Screening of IgM B cell repertoires from one non-PV and three PV patients identified specific cross-reactive Abs in one PV patient, but notably all six cross-reactive clonotypes used VH1-46. Site-directed mutagenesis studies indicate that amino acid residues predisposing VH1-46 Abs to Dsg3 reactivity reside in CDR2. However, somatic mutations only rarely promote Dsg3-VP6 cross-reactivity; most mutations abolish VP6 and/or Dsg3 reactivity. Nevertheless, functional testing identified two cross-reactive VH1-46 Abs that both disrupt keratinocyte adhesion and inhibit rotavirus replication, indicating the potential for VH1-46 Abs to have both pathologic autoimmune and protective immune functions. Taken together, these studies suggest that certain VH1-46 B cell populations may be predisposed to Dsg3-VP6 cross-reactivity, but multiple mechanisms prevent the onset of autoimmunity after rotavirus exposure.

Skin microbiota-associated inflammation precedes autoantibody induced tissue damage in experimental epidermolysis bullosa acquisita.

Epidermolysis bullosa acquisita (EBA) is a chronic autoimmune blistering skin disease characterized by autoantibodies against type VII collagen (COL7). Immunization of SJL/J mice with recombinant murine COL7 results in break of tolerance and skin blisters. Strikingly, despite circulating autoantibodies, the same genetic background and identical environmental conditions, 20% of mice remain healthy. To elucidate the regulation of the transition from the presence of autoantibodies to overt autoimmune disease, we characterized the innate and adaptive immune response of mice that remain healthy after immunization and compared it to mice that developed skin disease. Both clinically healthy and diseased SJL/J mice showed circulating autoantibodies and deposition of complement-fixing IgG2c autoantibodies and C3 at the dermal-epidermal junction. However, only in diseased animals significant neutrophil infiltration and increase in FcgRIV expression were observed in the skin. In contrast, the expression of T cell signature cytokines in the T cell zone of the draining lymph node was comparable between clinically healthy and diseased animals after immunization. Surprisingly, health was associated with a decreased expression of CD11c, TNFA and KC (CXCL1) in the skin prior to immunization and could be predicted with a negative predictive value of >80%. Furthermore, mice that did not develop clinical disease showed a significantly higher richness and distinctly clustered diversity of their skin microbiota before immunization. Our data indicate that the decision whether blisters develop in the presence of autoantibodies is governed in the skin rather than in the lymph node, and that a greater richness of cutaneous bacterial species appears to be protective.

[Spontaneous remission of urticaria: does it exist and if so, when?] / Spontanremission der Urtikaria: Gibt es das, und wenn ja, wann?

BACKGROUND: Urticaria mostly occurs acutely with a very high probability of spontaneous remission. When it persists for more than 6 weeks a chronic urticaria is manifest, which occurs either spontaneously or inducible by specific triggers. The underlying mechanisms are not fully understood but recent research points to defined pathogenetic factors. QUESTION AND AIM: Whether spontaneous remission is possible in urticaria is summarized descriptively in this review, and suggestions are given for the "step down" of urticaria treatment after remission. The mechanisms including autoallergic, immunoglobulin E (IgE)-dependent type I reactions and autoimmune, activating IgG-dependent type IIb reactions are presented. These are discussed in the context of spontaneous remission and the possibilities of induced remission.

Corrigendum: Blocking soluble Fas Ligand ameliorates pemphigus: PC111 efficacy in ex-vivo human pemphigus models.

[This corrects the article DOI: 10.3389/fimmu.2023.1193032.].

Hereditary epidermolytic palmoplantar keratosis due to a novel desmoglein-1 mutation: A case report.

Key Clinical Message: Keratosis palmoplantaris striata type I (SPPK-I) is a rare autosomal-dominant type of hereditary epidermolytic palmoplantar keratoderma, which can be caused by mutations in desmoglein-1 (DSG-1). Patients suffer from hyperkeratotic plaques and painful palmoplantar fissures. Unfortunately, treatment options including salicylic vaseline, topical corticosteroids, phototherapy, and retinoids are inefficient. Abstract: Hereditary palmoplantar keratodermas (PPKs) represent a heterogeneous group of rare skin disorders with epidermal palmoplantar hyperkeratosis. Mutations in the desmoglein 1 gene (DSG1), a transmembrane glycoprotein, have been reported primarily in striate PPKs. We report a patient with keratosis palmoplantaris striata type I (SPPK-I) with a specific pathogenic variant [c.349C>T, p.(Arg117*)] in DSG1. Despite increased understanding, effective treatment options for PPK, including SPPK-I, remain limited.