Pathogenesis of epidermolysis bullosa acquisita, an autoimmune subepidermal bullous disease

Luteolin peracetate and gossypolone inhibit immune complex-mediated neutrophil activation in vitro and dermal-epidermal separation in an ex vivo model of epidermolysis bullosa acquisita

Introduction

Natural products have been shown to an important source of therapeutics for human disease. In this study, we aimed to identify natural compounds as potential therapeutics for epidermolysis bullosa acquisita (EBA), an autoimmune disease caused by autoantibodies to type VII collagen (COL7).

Methods

Utilizing an in vitro experimental system, we screened a natural product library composed of 800 pure compounds for their inhibitory effect on COL7-anti-COL7 IgG immune complex (IC)-mediated neutrophil activation and on neutrophil-mediated tissue damage.

Results

Three natural compounds, namely luteolin peracetate, gossypol, and gossypolone were capable in inhibiting the IC-induced neutrophil adhesion and oxygen burst in vitro. Furthermore, luteolin peracetate and gossypolone were able to inhibit the anti-COL7 IgG induced dermal-epidermal separation in an ex vivo model for EBA.

Discussion

In summary, this study demonstrates that luteolin peracetate and gossypolone are potential therapeutics for experimental EBA, which deserves further investigation.

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.

Fcγ Receptor IIB Controls Skin Inflammation in an Active Model of Epidermolysis Bullosa Acquisita

Epidermolysis bullosa acquisita (EBA) is an autoimmune skin blistering disease characterized by IgG autoantibodies (aAb) against type VII collagen (COL7). The mechanisms controlling the formation of such aAbs and their effector functions in the skin tissue are incompletely understood. Here, we assessed whether the inhibitory IgG Fc receptor, FcγRIIB, controls the development of autoimmune skin blistering disease in an active model of EBA. For this purpose, we immunized congenic EBA-susceptible B6.SJL-H2s (B6.s) and B6.s-Fcgr2b^−/− mice with the immunodominant vWFA2 region of COL7. B6.s-Fcgr2b^−/− mice developed a strong clinical phenotype with 15 ± 3.3% of affected body surface area at week 4. In contrast, the body surface area in B6.s mice was affected to a maximum of 5% at week 6 with almost no disease signs at week 4. Surprisingly, we already found strong but similar COL7-specific serum IgG1 and IgG2b aAb production at week 2. Further, aAb and C3b deposition in the skin of B6.s and B6.s-Fcgr2b^−/− mice increased between weeks 2 and 6 after vWFA2 immunization. Importantly, neutrophil skin infiltration and activation was much stronger in B6s-Fcgr2b^−/− than in B6.s mice and already present at week 2. Also, the early aAb response in B6.s-Fcgr2b^−/− mice was more diverse than in wt B6.s mice. Reactive oxygen species (ROS) release from infiltrating neutrophils play a crucial role as mediator of skin inflammation in EBA. In line, sera from B6.s and B6.s-Fcgr2b^−/− mice induced strong ROS release from bone marrow-neutrophils in vitro. In contrast to the antibody-transfer-induced EBA model, individual targeting of FcγRIII or FcγRIV decreased ROS release to 50%. Combined FcγR blocking abrogated ROS release from BM neutrophils. Also, ROS release induced by COL7-specific serum IgG aAbs was significantly higher using BM neutrophils from B6.s-Fcgr2b^−/− than from B6.s mice. Together, our findings identified FcγRIIB as a suppressor of skin inflammation in the active EBA model through inhibition of early epitope spreading, protection from strong early neutrophil infiltration to and activation of neutrophils in the skin and suppression of FcγRIII activation by IgG1 aAbs which drive strong ROS release from neutrophils leading to tissue destruction at the dermal-epidermal junction.

Epidermolysis Bullosa Acquisita: The 2019 Update

Epidermolysis bullosa acquisita (EBA) is an orphan autoimmune disease. Patients with EBA suffer from chronic inflammation as well as blistering and scarring of the skin and mucous membranes. Current treatment options rely on non-specific immunosuppression, which in many cases, does not lead to a remission of treatment. Hence, novel treatment options are urgently needed for the care of EBA patients. During the past decade, decisive clinical observations, and frequent use of pre-clinical model systems have tremendously increased our understanding of EBA pathogenesis. Herein, we review all of the aspects of EBA, starting with a detailed description of epidemiology, clinical presentation, diagnosis, and current treatment options. Of note, pattern analysis via direct immunofluorescence microscopy of a perilesional skin lesion and novel serological test systems have significantly facilitated diagnosis of the disease. Next, a state-of the art review of the current understanding of EBA pathogenesis, emerging treatments and future perspectives is provided. Based on pre-clinical model systems, cytokines and kinases are among the most promising therapeutic targets, whereas high doses of IgG (IVIG) and the anti-CD20 antibody rituximab are among the most promising "established" EBA therapeutics. We also aim to raise awareness of EBA, as well as initiate basic and clinical research in this field, to further improve the already improved but still unsatisfactory conditions for those diagnosed with this condition.

Meta-analysis of the clinical and immunopathological characteristics and treatment outcomes in epidermolysis bullosa acquisita patients

Background

Epidermolysis bullosa acquisita (EBA) is an orphan autoimmune disease. Several clinical phenotypes have been described, but subepidermal blistering is characteristic of all variants. Limited data on clinical and immunopathological characteristics and treatment outcomes in EBA are available. To fill this gap, we collected this information from EBA cases, meeting current diagnostic criteria, published between 1971 and 2016.

Results

We identified 1159 EBA cases. This number must be, however, interpreted with caution, as it is not possible to check for multiple reporting. The analysis of all cases indicated that EBA affects all age groups (median: 50 years, range: 1 to 94 years) at an equal gender distribution. Non-mechanobullous (non-MB) forms of EBA were observed in 55% of patients, whereas the mechanobullous variant (MB-EBA) or a combination of both variants was described in 38 or 7% of patients, respectively. Type VII collagen (COL7)-specific autoantibodies were primarily of the IgG isotype, but anti-COL7 IgA, IgM and IgE were also documented. Comparison of the 2 clinical EBA types showed a higher frequency of IgA deposits in non-MB EBA as opposed to MB EBA. Mucous membrane involvement was observed in 23% of patients, and 4.4% of cases were associated with other chronic inflammatory diseases. Of note, IgA deposits were more frequently observed in cases with mucous membrane involvement. Our analysis indicated that EBA is difficult to treat and that the choice of treatment varies widely. Chi square was applied to identify medications associated with complete remission (CR). Considering all EBA cases, intravenous immunoglobulin (IVIG, p = 0.0047) and rituximab (p = 0.0114) were associated with CR. Subgroup analysis demonstrated that no treatment was associated with CR for non-MB EBA, while IVIG (p = 0.003) was associated with CR in MB EBA.

Conclusions

Within the limitations of the study, we here document the clinical and immunopathological characteristics and treatment outcomes in a large cohort of EBA patients. The observed associations of single drugs with treatment outcome may serve as a guide to develop clinical trials.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0896-1) contains supplementary material, which is available to authorized users.

Clinical and Immunological Study of 30 Cases With Both IgG and IgA Anti-Keratinocyte Cell Surface Autoantibodies Toward the Definition of Intercellular IgG/IgA Dermatosis

Several sporadic cases, in which direct and indirect immunofluorescence studies simultaneously detected IgG and IgA autoantibodies to keratinocyte cell surfaces, have been reported mainly under the name of IgG/IgA pemphigus. However, there have been no systematic studies for this condition. In this study, we collected 30 cases of this condition from our cohort of more than 5,000 autoimmune bullous disease cases, which were consulted for our diagnostic methods from other institutes, and summarized their clinical and immunological findings. Clinically, there was no male-female prevalence, mean age of disease onset was 55.6 years, and mean duration before this condition was suspected was 18 months. The patients showed clinically bullous and pustular skin lesions preferentially on the trunk and extremities, and histopathologically intraepidermal pustules and blisters with infiltration of neutrophils and eosinophils. Immunologically, ELISAs frequently detected IgG and IgA autoantibodies to both desmogleins and desmocollins. From the characteristic clinical, histopathological, and immunological features, which are considerably different from those in classical IgG types of pemphigus, we propose this disease as a new disease entity with preferential name of intercellular IgG/IgA dermatosis (IGAD). This was the largest study of IGAD to date.

Anti-FcγRIIB mAb suppresses murine IgG-dependent anaphylaxis by Fc domain targeting of FcγRIII

BACKGROUND

The inhibitory receptor FcγRIIB is expressed on human and murine bone marrow-derived cells and limits inflammation by suppressing signaling through stimulatory receptors.

OBJECTIVE

We sought to evaluate the effects of K9.361, a mouse IgG_2a alloantibody to mouse FcγRIIB, on murine anaphylaxis.

METHODS

Wild-type and FcγR-deficient mice were used to study anaphylaxis, which was induced by injection of 2.4G2 (rat IgG_2b mAb that binds both FcγRIIB and the stimulatory receptor FcγRIII), by actively immunizing IgE-deficient mice and then challenging with the immunizing antigen, and by passive immunization with IgG or IgE anti-2,4,6-trinitrophenyl mAb, followed by injection of 2,4,6-trinitrophenyl-ovalbumin. Pretreatment with K9.361 was assessed for its ability to influence anaphylaxis.

RESULTS

Unexpectedly, K9.361 injection induced mild anaphylaxis, which was both FcγRIIB and FcγRIII dependent and greatly enhanced by β-adrenergic blockade. K9.361 injection also decreased expression of stimulatory Fcγ receptors, especially FcγRIII, and strongly suppressed IgG-mediated anaphylaxis without strongly affecting IgE-mediated anaphylaxis. The F(ab')₂ fragment of K9.361 did not induce anaphylaxis, even after β-adrenergic blockade, and did not deplete FcγRIII or suppress IgG-mediated anaphylaxis but prevented intact K9.361-induced anaphylaxis without diminishing intact K9.36 suppression of IgG-mediated anaphylaxis.

CONCLUSION

Cross-linking FcγRIIB to stimulatory FcγRs through the Fc domains of an anti-FcγRIIB mAb induces and then suppresses IgG-mediated anaphylaxis without affecting IgE-mediated anaphylaxis. Because IgG- and IgE-mediated anaphylaxis can be mediated by the same cell types, this suggests that desensitization acts at the receptor rather than cellular level. Sequential treatment with the F(ab')₂ fragment of anti-FcγRIIB mAb followed by intact anti-FcγRIIB safely prevents IgG-mediated anaphylaxis.

Rituximab Monotherapy and Rituximab-Containing Chemotherapy Were Effective for Paraneoplastic Pemphigus Accompanying Follicular Lymphoma, but not for Subsequent Bronchiolitis Obliterans

A 60-year-old male patient suffered from mild exertional dyspnea, wheezing, and systemic blisters. He was diagnosed with paraneoplastic pemphigus (PNP) with follicular lymphoma in the pancreas head and pelvic cavity. He was first treated with eight cycles of rituximab; his blisters and erosions gradually improved and highly elevated levels of auto-antibodies related to PNP gradually decreased to normal levels. However, obstructive and restrictive respiratory failure still progressed. Computed tomography of the inspiratory and expiratory phases revealed obstructive pulmonary disorder, leading to a diagnosis of bronchiolitis obliterans (BO). The patient underwent plasma exchange and was repeatedly treated with rituximab monotherapy and rituximab-containing chemotherapies, but died 7 months after the diagnosis of BO. Early introduction of rituximab-containing regimens may be necessary to prevent the development of BO accompanying PNP. However, when a diagnosis of PNP-related BO is made, lung transplantation may also be considered for patients in whom rituximab-containing regimens are effective for PNP.

Rapid desensitization of mice with anti-FcγRIIb/FcγRIII mAb safely prevents IgG-mediated anaphylaxis

BACKGROUND

Stimulatory IgG receptors (FcγRs) on bone marrow-derived cells contribute to the pathogenesis of several autoimmune and inflammatory disorders. Monoclonal antibodies that block FcγRs might suppress these diseases, but they can induce anaphylaxis.

OBJECTIVE

We wanted to determine whether a rapid desensitization approach can safely suppress IgG/FcγR-mediated anaphylaxis.

METHODS

Mice were injected with serially increasing doses of 2.4G2, a rat mAb that blocks the inhibitory FcγR, FcγRIIb, and the stimulatory receptor, FcγRIII. Rectal temperature was used to detect the development of anaphylaxis. Passive and active IgG-mediated anaphylaxis were evaluated in mice that had been rapidly desensitized with 2.4G2 or mock-desensitized in mice in which monocyte/macrophages, basophils, or neutrophils had been depleted or desensitized and in mice in which FcγRI, FcγRIII, and/or FcγRIV had been deleted or blocked.

RESULTS

Rapid desensitization with 2.4G2 prevented 2.4G2-induced shock and completely suppressed IgG-mediated anaphylaxis. Rapid desensitization of ovalbumin-sensitized mice with 2.4G2 was safer and more effective than rapid desensitization with ovalbumin. 2.4G2 treatment completely blocked FcγRIII and removed most FcγRI and FcγRIV from nucleated peripheral blood cells. Because IgG(2a)-mediated anaphylaxis was partially FcγRI and FcγRIV dependent, the effects of 2.4G2 on FcγRI and FcγRIV were probably crucial for its complete inhibition of IgG(2a)-mediated anaphylaxis. IgG(2a)-mediated anaphylaxis was partially inhibited by depletion or desensitization of monocyte/macrophages, basophils, or neutrophils.

CONCLUSION

IgG-mediated anaphylaxis can be induced by ligation of FcγRI, FcγRIII, or FcγRIV on monocycte/macrophages, basophils, or neutrophils and can be safely suppressed by rapid desensitization with anti-FcγRII/RIII mAb. A similar approach may safely suppress other FcγR-dependent immunopathology.