Effects of intravenous immunoglobulins on mice with experimental epidermolysis bullosa acquisita

Case Report: Biological treatment of epidermolysis bullosa acquisita: report on four cases and literature review

Epidermolysis bullosa acquisita (EBA) is a chronic, recurrent autoimmune subepidermal bullous disease characterized by the presence of autoantibodies targeting type VII collagen -- basement membrane zone antigen. Standard therapy for EBA includes a combination of systemic corticosteroids and dapsone; however, severe cases may require advanced treatment. The current article reports on four EBA cases in which biologics: infliximab, rituximab (Rtx), and intravenous immunoglobulin (IVIG) were applied. All patients fulfilled the clinical and immunological criteria of EBA: they presented tense blisters healing with atrophic scars on the skin on traumatized areas and in mucous membranes. The diagnosis of EBA was established using numerous techniques: direct and indirect immunofluorescence, salt split skin, ELISA, Fluorescence Overlay Antigen Mapping using Laser Scanning Confocal Microscopy. Since all the patients did not achieve long-term remission on standard treatment (prednisone, dapsone) due to ineffectiveness or side effects of drugs, they eventually were treated with biologics leading to extraordinary skin improvement and stopping the disease for 1-3 years. Biologics in all patients were tolerated very well. No side effects were observed during application as well as multi-month follow-up. The presented cases provide a premise that biological drugs can be a valuable component of EBA therapy.

T Regulatory Cell-Associated Tolerance Induction by High-Dose Immunoglobulins in an HLA-Transgenic Mouse Model of Pemphigus

Pemphigus vulgaris (PV) is a potentially lethal autoimmune bullous skin disorder caused by IgG autoantibodies against desmoglein 3 (Dsg3) and Dsg1. During the last three decades, high-dose intravenous immunoglobulins (IVIgs) have been applied as an effective and relatively safe treatment regime in severe, therapy-refractory PV. This prompted us to study T- and B- cell polarization by IVIg in a human-Dsg3-dependent mouse model for PV. Using humanized mice transgenic for HLA-DRB1*04:02, which is a highly prevalent haplotype in PV, we employed IVIg in two different experimental approaches: in prevention and quasi-therapeutic settings. Our data show that intraperitoneally applied IVIg was systemically distributed for up to 42 days or longer. IVIg-treated Dsg3-immunized mice exhibited, in contrast to Dsg3-immunized mice without IVIg, significantly less Dsg3-specific IgG, and showed induction of T regulatory cells in lymphatic tissue. Ex vivo splenocyte analysis upon Dsg3-specific stimulation revealed an initial, temporarily reduced antigen-induced cell proliferation, as well as IFN-γ secretion that became less apparent over the course of time. Marginal-zone B cells were initially reduced in the preventive approach but re-expanded over time. In contrast, in the quasi-therapeutic approach, a robust down-regulation in both spleen and lymph nodes was observed. We found a significant down-regulation of the immature transitional 1 (T1) B cells in IVIg-treated mice in the quasi-therapeutic approach, while T2 and T3, representing a healthy stage of B-cell development, appeared to be up-regulated by IVIg. In summary, in two experimental settings employing an active PV mouse model, we demonstrate distinct alterations of T- and B-cell populations upon IVIg treatment, compatible with a tolerance-associated polarization in lymphatic tissue. Our data suggest that the clinical efficacy of IVIg is at least modulated by distinct alterations of T- and B-cell populations compatible with a tolerance-associated polarization in lymphatic tissue.

IgG subclass and Fc glycosylation shifts are linked to the transition from pre- to inflammatory autoimmune conditions

A crucial factor for the development of inflammatory autoimmune diseases is the occurrence of antibodies directed against self-tissues and structures, which leads to damage and inflammation. While little is known about the cause of the development of mis-directed, disease-specific T and B cells and resulting IgG autoantibody responses, there is increasing evidence that their induction can occur years before disease symptoms appear. However, a certain proportion of healthy individuals express specific IgG autoantibodies without disease symptoms and not all subjects who generate autoantibodies may develop disease symptoms. Thus, the development of inflammatory autoimmune diseases seems to involve two steps. Increasing evidence suggests that harmless self-directed T and B cell and resulting IgG autoantibody responses in the pre-autoimmune disease stage might switch to more inflammatory T and B cell and IgG autoantibody responses that trigger the inflammatory autoimmune disease stage. Here, we summarize findings on the transition from the pre-disease to the disease stage and vice versa, e.g. by pregnancy and treatment, with a focus on low-/anti-inflammatory versus pro-inflammatory IgG autoantibody responses, including IgG subclass and Fc glycosylation features. Characterization of biomarkers that identify the transition from the pre-disease to the disease stage might facilitate recognition of the ideal time point of treatment initiation and the development of therapeutic strategies for re-directing inflammatory autoimmune conditions.

Cutaneous kinase activity correlates with treatment outcomes following PI3K delta inhibition in mice with experimental pemphigoid diseases

Chronic blistering at the skin and/or mucous membranes, accompanied by a varying degree of inflammation, is the clinical hallmark of pemphigoid diseases that impose a major medical burden. Pemphigoid diseases are caused by autoantibodies targeting structural proteins of the epithelial basement membrane. One major pathogenic pathway of skin blistering and inflammation is activation of myeloid cells following Fc gamma receptor-dependent binding to the skin-bound immune complexes. This process requires activation of specific kinases, such as PI3Kδ, which have emerged as potential targets for the treatment of pemphigoid diseases. Yet, it is unknown if global cutaneous kinase activity present in lesional pemphigoid disease correlates with therapeutic effects following treatment with a given target-selective kinase inhibitor. To address this, we here first determined the kinase activity in three different mouse models of pemphigoid diseases: Antibody transfer-induced mucous membrane pemphigoid (MMP), antibody transfer-induced epidermolysis bullosa acquisita (EBA) and immunization-induced EBA. Interestingly, the kinome signatures were different among the three models. More specifically, PI3Kδ was within the kinome activation network of antibody transfer-induced MMP and immunization-induced EBA, but not in antibody transfer-induced EBA. Next, the therapeutic impact of the PI3Kδ-selective inhibitor parsaclisib was evaluated in the three model systems. In line with the kinome signatures, parsaclisib had therapeutic effects in antibody transfer-induced MMP and immunization-induced EBA, but not in autoantibody-induced EBA. In conclusion, kinase activation signatures of inflamed skin, herein exemplified by pemphigoid diseases, correlate with the therapeutic outcomes following kinase inhibition, demonstrated here by the PI3Kδ inhibitor parsaclisib.

Intravenous Ig Regulates Anti-Desmoglein 3 IgG Production in B220- Antibody-Producing Cells in Mice with Pemphigus Vulgaris

Intravenous Ig (IVIG) is a treatment option for intractable cases of pemphigus vulgaris (PV), an autoimmune blistering disease caused by autoantibodies against desmoglein 3 (DSG3). To investigate the efficacy of IVIG on autoantibody secretion, we produced PV model mice by adoptive transfer of immunized Dsg3^-/- splenocytes to Rag2^-/- mice. We found that circulating anti-DSG3 IgG ELISA titer decreased in PV model mice after 5 days of treatment with IVIG compared with PBS-treated mice, whereas the F(ab')₂ fragment did not suppress the anti-DSG3 IgG titer. enzyme-linked immunospot assay revealed that IVIG treatment reduced the frequency of anti-DSG3 antibody-secreting cells in the spleen but not in lymph nodes and bone marrow. Moreover, this reduction was observed only in the splenic B220^- fraction but not in the B220⁺ fraction. Furthermore, IVIG decreased the serum levels of anti-DSG3 IgG, even after a significant reduction of its titer, owing to antibody-mediated CD20⁺ B cell depletion. In addition, IVIG suppressed anti-DSG3 IgG production in B220^-CD138⁺ plasma cells derived from PV model mice ex vivo. These results indicate that IVIG reduced autoantibody production in B220^- cells containing plasma cells in PV model mice, and this function may indicate one of the mechanisms of action of IVIG on PV.

Multiple modes of action mediate the therapeutic effect of IVIg in experimental epidermolysis bullosa acquisita

Substitution of IgG in antibody deficiency or application of high-dose intravenous IgG (IVIg) in patients with autoimmunity are well-established treatments. Data on the mode of action of IVIg are, however, controversial and may differ for distinct diseases. In this study, we investigated the impact and molecular mechanism of high-dose IgG treatment in murine autoantibody-induced skin inflammation, namely, epidermolysis bullosa acquisita (EBA). EBA is caused by antibodies directed against type VII collagen (COL7) and is mediated by complement activation, release of reactive oxygen species, and proteases by myeloid cells. In murine experimental EBA the disease can be induced by injection of anti-COL7 IgG. Here, we substantiate that treatment with high-dose IgG improves clinical disease manifestation. Mechanistically, high-dose IgG reduced the amount of anti-COL7 in skin and sera, which is indicative for an FcRn-dependent mode-of-action. Furthermore, in a non-receptor-mediated fashion, high-dose IgG showed antioxidative properties by scavenging extracellular reactive oxygen species. High-dose IgG also impaired complement activation and served as substrate for proteases, both key events during EBA pathogenesis. Collectively, the non-receptor-mediated anti-inflammatory properties of high-dose IgG may explain the therapeutic benefit of IVIg treatment in skin autoimmunity.

Epidermolysis bullosa acquisita: an uncommon cause of esophageal stricture

Epidermolysis bullosa acquisita (EBA) encompasses a wide spectrum of rare diseases with a common genetic origin transmitted in an autosomal recessive fashion. Mild forms of non-inflammatory EBA are characterized by skin lesions and have gained great relevance in the literature. However, resistant inflammatory EBA with widespread mucosal involvement remains a rare entity given its low prevalence. It commonly represents a great burden for the patient's quality of life with most cases being resistant to different therapeutic modalities. We present a case of resistant inflammatory EBA with esophageal strictures that improved after therapy with intravenous immunoglobulin and rituximab.

Treatment with anti-neonatal Fc receptor (FcRn) antibody ameliorates experimental epidermolysis bullosa acquisita in mice

Background and Purpose

Pemphigus and pemphigoid diseases are characterized and caused predominantly by IgG autoantibodies targeting structural proteins of the skin. Their current treatment relies on general and prolonged immunosuppression that causes severe adverse events, including death. Hence, novel safe and more effective treatments are urgently needed. Due to its' physiological functions, the neonatal Fc receptor (FcRn) has emerged as a potential therapeutic target for pemphigus and pemphigoid, primarily because IgG is protected from proteolysis after uptake into endothelial cells. Thus, blockade of FcRn would reduce circulating autoantibody concentrations. However, long‐term effects of pharmacological FcRn inhibition in therapeutic settings of autoimmune diseases are unknown.

Experimental Approach

Therapeutic effects of FcRn blockade were investigated in a murine model of the prototypical autoantibody‐mediated pemphigoid disease, epidermolysis bullosa acquisita (EBA). B6.SJL‐H2s C3c/1CyJ mice with clinically active disease were randomized to receive either an anti‐FcRn monoclonal antibody (4470) or an isotype control over 4 weeks.

Key Results

While clinical disease continued to worsen in isotype control‐treated mice, overall disease severity continuously decreased in mice injected with 4470, leading to almost complete remission in over 25% of treated mice. These clinical findings were paralleled by a reduction of autoantibody concentrations. Reduction of autoantibody concentrations, rather than modulating neutrophil activation, was responsible for the observed therapeutic effects.

Conclusion and Implications

The clinical efficacy of anti‐FcRn treatment in this prototypical autoantibody‐mediated disease encourages further development of anti‐FcRn antibodies for clinical use in pemphigoid diseases and potentially in other autoantibody mediated diseases.

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

Drug Discovery for Pemphigoid Diseases

Pemphigoid diseases (PDs) are a group of autoimmune bullous diseases characterized and caused by autoantibodies targeting structural proteins of the skin and mucous membranes. Chronic inflammation, subepidermal blistering, and often scaring are the clinical characteristics of PDs. Itching and, in severe cases, disabilities resulting from scaring (i.e., blindness, esophageal strictures) are the leading subjective symptoms. Treatment of PDs, which is based on nonspecific immunosuppression, is challenging because of frequent relapses, lack of efficacy, and numerous adverse events. In addition, the incidence of PDs is increasing. Given the high morbidity, limited therapeutic options, and increasing incidence, there is a growing urgency for drug discovery to help treat this condition. The recent development of PD model systems has added to the understanding of PD pathogenesis and, based on these insights, new clinical trials will soon be launched. The (auto-)antibody transfer PD models allow for investigations into autoantibody-mediated tissue pathology, while immunization-induced PD models more closely resemble the clinical situation. The latter duplicate all aspects of the human disease and are useful for investigating PD pathogenesis and testing therapeutic interventions. This article describes antibody transfer and immunization-induced PD mouse models currently employed for translational PD research. © 2019 by John Wiley & Sons, Inc.

Sweet SIGNs: IgG glycosylation leads the way in IVIG-mediated resolution of inflammation

A hallmark of many chronic inflammatory and autoimmune diseases is that there is an impaired resolution of inflammation and return to the steady state. The infusion of high doses of pooled serum IgG preparations from thousands of donors [intravenous immunoglobulin (IVIG) therapy] has been shown to induce resolution of inflammation in a variety of chronic inflammatory and autoimmune diseases, suggesting that IgG molecules can instruct the immune system to stop inflammatory processes and initiate the return to the steady state. The aim of this review is to discuss how insights into the mechanism of IVIG activity may help to understand the molecular and cellular pathways underlying resolution of inflammation. We will put a special emphasis on pathways dependent on the IgG FC domain and IgG sialylation, as several recent studies have provided new insights into how this glycosylation-dependent pathway modulates innate and adaptive immune responses through different sets of C-type or I-type lectins.

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.

Therapeutic Effect of a Novel Phosphatidylinositol-3-Kinase δ Inhibitor in Experimental Epidermolysis Bullosa Acquisita

Epidermolysis bullosa acquisita (EBA) is a rare, but prototypical, organ-specific autoimmune disease, characterized and caused by autoantibodies against type VII collagen (COL7). Mucocutaneous inflammation, blistering, and scarring are the clinical hallmarks of the disease. Treatment of EBA is difficult and mainly relies on general immunosuppression. Hence, novel treatment options are urgently needed. The phosphatidylinositol-3-kinase (PI3K) pathway is a putative target for the treatment of inflammatory diseases, including EBA. We recently discovered LAS191954, an orally available, selective PI3Kδ inhibitor. PI3Kδ has been shown to be involved in B cell and neutrophil cellular functions. Both cell types critically contribute to EBA pathogenesis, rendering LAS191954 a potential drug candidate for EBA treatment. We, here, demonstrate that LAS191954, when administered chronically, dose-dependently improved the clinical phenotype of mice harboring widespread skin lesions secondary to immunization-induced EBA. Direct comparison with high-dose corticosteroid treatment indicated superiority of LAS191954. Interestingly, levels of circulating autoantibodies were unaltered in all groups, indicating a mode of action independent of the inhibition of B cell function. In line with this, LAS191954 also hindered disease progression in antibody transfer-induced EBA, where disease develops dependent on myeloid, but independent of B cells. We further show that, in vitro, LAS191954 dose-dependently impaired activation of human myeloid cells by relevant disease stimuli. Specifically, immune complex-mediated and C5a-mediated ROS release were inhibited in a PI3Kδ-dependent manner. Accordingly, LAS191954 also modulated the dermal–epidermal separation induced in vitro by co-incubation of immune complexes with polymorph nuclear cells, thus pointing to an important role of PI3Kδ in EBA effector functions. Altogether, these results suggest a new potential mechanism for the treatment of EBA and potentially also other autoimmune bullous diseases.

Anti-idiotypic Antibodies against BP-IgG Prevent Type XVII Collagen Depletion

Bullous pemphigoid (BP) mainly targets type XVII collagen (COL17). Intravenous immunoglobulin (IVIg) is used to treat numerous autoimmune diseases, including BP. The major mechanism of action for IVIG is thought to be its immunomodulatory effect. However, little is known about the precise mechanisms of IVIg in BP. We investigate the cellular effects of IVIg, toward treatments for BP. Keratinocytes were treated with IgG from BP patients (BP-IgG) and with IVIg, and then the COL17 expression was detected by Western blotting. Cell adhesion and ex vivo dermal-epidermal separation were also investigated for the condition with BP-IgG and IVIg. BP-IgG targeting the non-collagenous 16A domain induces the depletion of COL17 in cultured keratinocytes (DJM-1 cells). The COL17 levels in DJM-1 cells were decreased by 50% after 4 h of BP-IgG stimulation as determined by Western blotting. By contrast, BP-IgG with IVIg was found to result in 70-90% increases in COL17 and to restore adhesion to the plate. Interestingly, IVIg significantly inhibited the binding of BP-IgG to the COL17-enzyme-linked immunosorbent assay plate, and this was due to anti-idiotypic antibodies against BP-IgG. When anti-idiotypic antibodies against BP-IgG in 0.02% of IVIg were depleted from IVIg, those antibodies did not exhibit inhibitory effects on COL17 depletion. When cryosections of human skin were incubated with BP-IgG in the presence of leukocytes, dermal-epidermal separation was observed. BP-IgG treatment with IVIg or anti-idiotypic antibodies did not induce such separation. These findings strongly suggest the presence of anti-idiotypic antibodies against anti-COL17 IgG in IVIg. This mechanism of IVIg could be a target for therapies against BP.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Immune mechanism-targeted treatment of experimental epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is an autoimmune bullous dermatosis characterized by chronic mucocutaneous blistering caused by autoantibodies directed against type VII collagen. EBA causes a high morbidity and is difficult to treat. Model systems have significantly broadened our understanding of EBA pathogenesis, leading to the identification of numerous therapeutic targets. Of these, so far, a few have been evaluated for their therapeutic potential in preclinical models. In mice, EBA can be induced by transfer of anti-type VII collagen antibodies or by immunization with the protein. The latter model, immunization-induced EBA, is ideal to test drugs for their therapeutic efficacy. Here, mice with already established disease can be treated for prolonged periods. Albeit time consuming, results from immunization-induced EBA will pave the way for clinical application in patients. As the key pathogenic principle, that is, autoantibody-induced, leukocyte-mediated tissue injury and inflammation, is shared by other diseases, these findings may have translational applications beyond EBA.

Radiosensitive Hematopoietic Cells Determine the Extent of Skin Inflammation in Experimental Epidermolysis Bullosa Acquisita

Animal models have enhanced our understanding of the pathogenesis of autoimmune diseases. For these models, genetically identical, inbred mice have commonly been used. Different inbred mouse strains, however, show a high variability in disease manifestation. Identifying the factors that influence this disease variability could provide unrecognized insights into pathogenesis. We established a novel Ab transfer-induced model of epidermolysis bullosa acquisita (EBA), an autoimmune disease characterized by (muco)-cutaneous blistering caused by anti-type VII collagen (COL7) autoantibodies. Blistering after anti-COL7 IgG (directed against the von Willebrand factor A-like domain 2) transfer showed clear variability among inbred mouse strains, that is, severe cutaneous blistering and inflammation in C57BL/6J and absence of skin lesions in MRL/MpJ mice. The transfer of anti-COL7 IgG into irradiated, EBA-resistant MRL/MpJ mice, rescued by transplantation with bone marrow from EBA-susceptible B6.AK-H2k mice, induced blistering. To the contrary, irradiated EBA-susceptible B6.AK-H2k mice that were rescued using MRL/MpJ bone marrow were devoid of blistering. In vitro, immune complex activation of neutrophils from C57BL/6J or MRL/MpJ mice showed an impaired reactive oxygen species release from the latter, whereas no differences were observed after PMA activation. This finding was paralleled by divergent expression profiles of immune complex-activated neutrophils from either C57BL/6J or MRL/MpJ mice. Collectively, we demonstrate that radiosensitive cells determine the varying extent of skin inflammation and blistering in the end-stage effector phase of EBA.