Catalytic antibodies in arrhythmogenic cardiomyopathy patients cleave desmoglein 2 and N-cadherin and impair cardiomyocyte cohesion.

AIMS: Arrhythmogenic cardiomyopathy (AC) is a severe heart disease predisposing to ventricular arrhythmias and sudden cardiac death caused by mutations affecting intercalated disc (ICD) proteins and aggravated by physical exercise. Recently, autoantibodies targeting ICD proteins, including the desmosomal cadherin desmoglein 2 (DSG2), were reported in AC patients and were considered relevant for disease development and progression, particularly in patients without underlying pathogenic mutations. However, it is unclear at present whether these autoantibodies are pathogenic and by which mechanisms show specificity for DSG2 and thus can be used as a diagnostic tool. METHODS AND RESULTS: IgG fractions were purified from 15 AC patients and 4 healthy controls. Immunostainings dissociation assays, atomic force microscopy (AFM), Western blot analysis and Triton X-100 assays were performed utilizing human heart left ventricle tissue, HL-1 cells and murine cardiac slices. Immunostainings revealed that autoantibodies against ICD proteins are prevalent in AC and most autoantibody fractions have catalytic properties and cleave the ICD adhesion molecules DSG2 and N-cadherin, thereby reducing cadherin interactions as revealed by AFM. Furthermore, most of the AC-IgG fractions causing loss of cardiomyocyte cohesion activated p38MAPK, which is known to contribute to a loss of desmosomal adhesion in different cell types, including cardiomyocytes. In addition, p38MAPK inhibition rescued the loss of cardiomyocyte cohesion induced by AC-IgGs. CONCLUSION: Our study demonstrates that catalytic autoantibodies play a pathogenic role by cleaving ICD cadherins and thereby reducing cardiomyocyte cohesion by a mechanism involving p38MAPK activation. Finally, we conclude that DSG2 cleavage by autoantibodies could be used as a diagnostic tool for AC.

A gene-centric approach to biomarker discovery identifies transglutaminase 1 as an epidermal autoantigen.

Autoantigen discovery is a critical challenge for the understanding and diagnosis of autoimmune diseases. While autoantibody markers in current clinical use have been identified through studies focused on individual disorders, we postulated that a reverse approach starting with a putative autoantigen to explore multiple disorders might hold promise. We here targeted the epidermal protein transglutaminase 1 (TGM1) as a member of a protein family prone to autoimmune attack. By screening sera from patients with various acquired skin disorders, we identified seropositive subjects with the blistering mucocutaneous disease paraneoplastic pemphigus. Validation in further subjects confirmed TGM1 autoantibodies as a 55% sensitive and 100% specific marker for paraneoplastic pemphigus. This gene-centric approach leverages the wealth of data available for human genes and may prove generally applicable for biomarker discovery in autoimmune diseases.

Anti-laminin 332 antibodies in graft-versus-host disease-associated bullous pemphigoid after allogeneic peripheral blood stem cell transplantation.

We report a 48-year-old woman with bullous pemphigoid (BP) with antibodies against the B3 subunit of laminin 332 after the development of graft-versus-host disease (GVHD). She was diagnosed with recurrent acute lymphoblastic leukemia at 40 years of age and underwent two rounds of allogeneic peripheral blood stem cell transplantations (PBST). Two and a half years after the second PBST, multiple tense blisters appeared on her face, hands, and lower legs. The diagnosis of BP was based on hematoxylin eosin and immunofluorescence staining and immunoblotting analyses. A combination regimen of topical corticosteroids (clobetasol propionate) and tetracycline/niacinamide was administered. Complete clinical resolution was achieved after four weeks of therapy without the use of immunosuppressive drugs. To maintain the graft-versus-tumor effect, topical corticosteroids and immunomodulatory drugs are preferred for BP after hematopoietic stem cell transplantation considering the risk of recurrence of hematologic malignancies. To date, there have been no reports of successful treatment of GVHD-associated BP without immunosuppressive drugs. Chronic GVHD is characterized by the production of autoantibodies. Furthermore, this autoimmune subepidermal blistering disease, BP, may be a manifestation of chronic GVHD. However, the precise mechanism of autoantibody production in chronic GVHD is not yet fully elucidated.

[Refractory esophageal stricture of esophageal mucous membrane pemphigoid after allogeneic hematopoietic stem cell transplantation].

Haploidentical allogeneic hematopoietic stem cell transplantation from her brother was performed on a 41-year-old lady with no prior history of pemphigoid to treat recurrent AML. On day 59 following transplantation, she experienced esophageal stenosis. During immunosuppressive therapy for graft vs. host disease, this condition was controlled with periodic esophageal dilatation (GVHD). Her esophageal stricture, which required periodic dilatation, grew worse after she stopped immunosuppressive therapy because of recurrent AML. The esophageal mucosa was easily hemorrhagic and desquamative. Histologic analysis revealed that the squamous cell layers had been divided. Indirect immunofluorescence was negative for IgG and positive for IgA on the epidermal layers, while direct immunofluorescence showed a linear deposition of IgG on the basement membrane zone. It was determined through immunoblotting utilizing recombinant protein of BP180 C-terminal domain that both IgG and IgA antibodies were present, supporting the diagnosis of mucous membrane pemphigoid with anti-BP180. After allogeneic transplantation, basal epidermal cell destruction by GVHD may result in autoimmune blistering disorders, which expose basement membrane proteins and antigen presentation. A similar mechanism could apply to our situation. For rare GVHD cases, a thorough histological diagnosis is required.

Anti-human serum albumin autoantibody may be involved in the pathogenesis of autoimmune bullous skin diseases.

Although effective immunological diagnostic systems for autoimmune bullous skin diseases (AIBD) have been established, there are still unidentified cutaneous autoantigens. The purpose of this study is to investigative whether anti-human serum albumin (HSA) autoantibodies exist in AIBD sera and their potential pathogenesis. By immunoprecipitation-immunoblotting, immunofluorescence assay, anti-HSA autoantibodies could be detected in AIBD sera; by ELISAs, positive rates of AIBD sera for IgG and IgA anti-HSA autoantibodies were 29% and 34%, respectively. The IgG anti-HSA autoantibodies in ABID sera recognized a number of HSA antigen epitopes and therefore a polyclonal antibody against HSA were next employed to study its pathogenesis. In vitro cell and tissue culture models, anti-HSA antibody could influence DNA damage-related signaling proteins, via activation of phospho-p38 signaling pathway. This is the first report that an autoantibody may influence DNA damage-related signaling proteins. Statistical analyses also proved that anti-HSA autoantibodies were positively correlated with various known autoantibodies and clinical features of ABID patients. In summary, IgG and IgA autoantibodies to HSA may have diagnosis values for AIBD. DNA damage-related signaling proteins might be involved in the pathogenic role of anti-HSA autoantibodies in AIBD. Phospho-p38 signaling pathway is a potential target for treatment of AIBD positive for serum anti-HSA autoantibodies.

Linear IgA bullous dermatosis associated with ulcerative colitis: A case report and literature review.

We report the case of a 59-year-old Japanese woman who developed linear IgA bullous dermatosis during treatment for ulcerative colitis that manifested as pruritic vesicles with erythema on the trunk and scalp. Histopathological examination revealed subepidermal bulla with neutrophil and eosinophil infiltration in the upper dermis. Direct immunofluorescence revealed linear IgA deposits at the basement membrane zone, and indirect immunofluorescence using split skin revealed IgA reaction to the epidermal side (lamina lucida type). We reviewed 33 reported cases of linear IgA bullous dermatosis associated with ulcerative colitis and found that ulcerative colitis preceded the onset of linear IgA bullous dermatosis in 94% of the patients and that IgA-positive patients in split skin indirect immunofluorescence all showed the lamina lucida type, indicating that target antigens for serum IgA antibodies may reside in the lamina lucida. Regarding the pathogenetic association of ulcerative colitis and linear IgA bullous dermatosis, intestinal inflammation may induce the exposure and presentation of intestinal antigens that are cross-reactive to cutaneous antigens, stimulating autoimmune response to antigens of cutaneous basement membrane zones.

Nonclassical pemphigus with exclusively IgG anti-desmocollin 3-specific antibodies.

We describe a patient with nonclassical clinical and histopathological features of pemphigus with exclusively IgG antibodies against desmocollin (Dsc) 3 detected by enzyme-linked immunosorbent assay of recombinant eukaryotic protein of Dsc1-Dsc3. The absence of antibodies against other known targets, such as desmogleins, reinforces the role of anti-Dsc antibodies in the pathophysiology of atypical pemphigus.

Vegetating erosive cutaneous lesions and pyogenic granuloma in the course of mucous membrane pemphigoid: a case report and review of literature.

Mucous membrane pemphigoid (MMP) is a group of chronic autoimmune sub-epithelial blistering disorders, which mostly affect the oral mucosa and the conjunctiva. MMP is very diverse in terms of both the clinical and immunological features (IgG and IgA autoantibodies may react with different antigens). MMP can be induced by infections and medication, including ophthalmologic medication, which may lead to the development of eye lesions. In contrast, a vegetating variant of MMP is extremely rare. Here, we report an MMP case that demonstrated unusual clinical features, that is, pyogenic granulomas on the conjunctivae and extensive vegetating erosions on the skin of intertriginous regions. All these lesions were considered to be induced by unconventional medication containing arsenic.

Unique mouse monoclonal antibodies reactive with maturation-related epitopes on type VII collagen.

In this study, we generated a new set of monoclonal antibodies (mAbs) to bovine and human type VII collagen (COL7) by immunizing mice with bovine cornea-derived basement membrane zone (BMZ) fraction. The four mAbs, tentatively named as COL7-like mAbs, showed speckled subepidermal staining in addition to linear BMZ staining of normal human skin and bovine cornea, a characteristic immunofluorescence feature of COL7, but showed no reactivity with COL7 by in vitro biochemical analyses. Taking advantage of the phenomenon that COL7-like mAbs did not react with mouse BMZ, we compared immunofluorescence reactivity between wild-type and COL7-rescued humanized mice and found that COL7-like mAbs reacted with BMZ of COL7-rescued humanized mice. In ELISAs, COL7-like mAbs reacted with intact triple-helical mammalian recombinant protein (RP) of COL7 but not with bacterial RP. Furthermore, COL7-like mAbs did not react with COL7 within either cultured DJM-1 cells or basal cells of skin of a bullous dermolysis of the newborn patient. These results confirmed that COL7-like mAbs reacted with human and bovine COL7. The epitopes for COL7-like mAbs were considered to be present only on mature COL7 after secretion from keratinocytes and deposition to BMZ and to be easily destroyed during immunoblotting procedure. Additional studies indicated association of the speckled subepidermal staining with both type IV collagen and elastin. These unique anti-COL7 mAbs should be useful in studies of both normal and diseased conditions, particularly dystrophic epidermolysis bullosa, which produces only immature COL7.