Research Techniques Made Simple: Mouse Models of Autoimmune Blistering Diseases

      Autoimmune blistering diseases are examples of autoantibody-mediated, organ-specific autoimmune disorders. Based on a genetic susceptibility, such as a strong HLA-class II association, as yet unknown triggering factors induce the formation of circulating and tissue-bound autoantibodies that are mainly directed against adhesion structures of the skin and mucous membranes. Compared with other autoimmune diseases, especially systemic disorders, the pathogenicity of autoimmune blistering diseases is relatively well described. Several animal models of autoimmune blistering diseases have been established that helped to uncover the immunological and molecular mechanisms underlying the blistering phenotypes. Each in vivo model focuses on specific aspects of the autoimmune cascade, from loss of immunological tolerance on the level of T and B cells to the pathogenic effects of autoantibodies upon binding to their target autoantigen. We discuss current mouse models of autoimmune blistering diseases, including models of pemphigus vulgaris, bullous pemphigoid, epidermolysis bullosa acquisita, and dermatitis herpetiformis.

      Abbreviations:

      AIDB (autoimmune blistering disease), BP (bullous pemphigoid), COL-17 (type XVII collagen), COL-7 (type VII collagen), DH (dermatitis herpetiformis), EBA (epidermolysis bullosa acquisita), MHC (major histocompatibility complex), PV (pemphigus vulgaris)
      CME Activity Dates: December 20, 2016
      Expiration Date: December 20, 2017
      Estimated Time to Complete: 1 hour
      Planning Committee/Speaker Disclosure: All authors, planning committee members, CME committee members and staff involved with this activity as content validation reviewers have no financial relationship(s) with commercial interests to disclose relative to the content of this CME activity.
      Commercial Support Acknowledgment: This CME activity is supported by an educational grant from Lilly USA, LLC.
      Description: This article, designed for dermatologists, residents, fellows, and related healthcare providers, seeks to reduce the growing divide between dermatology clinical practice and the basic science/current research methodologies on which many diagnostic and therapeutic advances are built.
      Objectives: At the conclusion of this activity, learners should be better able to:
      • Recognize the newest techniques in biomedical research.
      • Describe how these techniques can be utilized and their limitations.
      • Describe the potential impact of these techniques.
      CME Accreditation and Credit Designation: This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education through the joint providership of William Beaumont Hospital and the Society for Investigative Dermatology. William Beaumont Hospital is accredited by the ACCME to provide continuing medical education for physicians.
      William Beaumont Hospital designates this enduring material for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
      Method of Physician Participation in Learning Process: The content can be read from the Journal of Investigative Dermatology website: http://www.jidonline.org/current. Tests for CME credits may only be submitted online at https://beaumont.cloud-cme.com/RTMS-Jan17 – click ‘CME on Demand’ and locate the article to complete the test. Fax or other copies will not be accepted. To receive credits, learners must review the CME accreditation information; view the entire article, complete the post-test with a minimum performance level of 60%; and complete the online evaluation form in order to claim CME credit. The CME credit code for this activity is: 21310. For questions about CME credit email [email protected] .

      Introduction

      Autoimmune blistering diseases (AIBDs) are a group of rare acquired blistering skin diseases that are divided into four major groups based on clinical appearance and pathology: pemphigus diseases, including the most common clinical subtypes pemphigus vulgaris (PV) and pemphigus foliaceus, the pemphigoid diseases like bullous pemphigoid (BP), epidermolysis bullosa acquisita (EBA), and dermatitis herpetiformis (DH). These diseases share the common feature of being caused by circulating autoantibodies targeting disease-specific autoantigens in the human skin, resulting in painful blisters of the skin and/or mucous membranes. Several mouse models of AIBD have been generated, allowing researchers to investigate key pathophysiological mechanisms. These models are either passive, based on the transfer of previously generated autoantibodies into mice to generate a blistering phenotype in vivo, or active, based on immunization of wild-type or genetically modified mice with the autoantigen to induce an autoimmune response (see
      • Iwata H.
      • Bieber K.
      • Hirose M.
      • Ludwig R.J.
      Animal models to investigate pathomechanisms and evaluate novel treatments for autoimmune bullous dermatoses.
      for a comprehensive review).
      In this article we will describe current active mouse models for AIBD that use immunization of wild-type or genetically modified mice (Figure 1 and Table 1). The models help to show certain key elements of disease pathogenesis as follows: (a) the loss of tolerance to self-antigens leading to the generation of autoreactive immune cells, (b) the T- and B-cell–dependent production of autoantibodies, and (c) autoantibody-dependent tissue damage. Genetic modification of mice can be defined as (i) the introduction of exogenous genes, like human autoantigens, into the genome of mice (gain of function); (ii) the knockout of endogenous genes in mice (loss of function), and (iii) the knockin of modified endogenous genes (change of function). These techniques have been described comprehensively in previous Research Techniques Made Simple articles (
      • Griffin R.L.
      • Kupper T.S.
      • Divito S.J.
      Humanized mice in dermatology research.
      ,
      • Günschmann C.
      • Chiticariu E.
      • Garg B.
      • Hiz M.M.
      • Mostmans Y.
      • Wehner M.
      • et al.
      Transgenic mouse technology in skin biology: inducible gene knockout in mice.
      ,
      • Scharfenberger L.
      • Hennerici T.
      • Király G.
      • Kitzmüller S.
      • Vernooij M.
      • Zielinski J.G.
      Transgenic mouse technology in skin biology: generation of complete or tissue-specific knockout mice.
      ,
      • Tellkamp F.
      • Benhadou F.
      • Bremer J.
      • Gnarra M.
      • Knüver J.
      • Schaffenrath S.
      • et al.
      Transgenic mouse technology in skin biology: generation of knockin mice.
      ).
      Figure 1
      Figure 1Mouse models of autoimmune blistering diseases. Autoantigens and mouse strains used for immunization are shown for each respective autoimmune blistering disease. (a) Current animal models for PV, BP, EBA, and DH use wild-type or humanized HLA-transgenic mice. Some models are limited because of weak homology between human and mouse proteins and established self-tolerance to autoantigens in mice. (b) To avoid the difficulty of self-tolerance, preventing the mouse immune system from reacting destructively against autoantigens of the skin, enhanced models for PV and BP use immunization of mice lacking the autoantigen. After subsequent adoptive transfer of splenocytes (containing autoreactive T and B cells) in Rag2-knockout recipient animals expressing the autoantigen, an autoimmune response is initiated that resembles certain aspects of the human disease. BP, bullous pemphigoid; COL7, type VII collagen; COL17, type XVII collagen; DH, dermatitis herpetiformis; Dsg3, desmoglein 3; EBA, epidermolysis bullosa acquisita; PV, pemphigus vulgaris.
      Table 1Models of AIBD using active immunization with the respective antigens
      Blistering DiseasePurpose of ModelMethods Used in the ModelReferences
      PVGeneration of mouse Dsg3-specific T and B cells and characterization of produced autoantibodies; induction of a clinical phenotype in mouseImmunization of Dsg3 knockout mice with mouse Dsg3 and subsequent transfer of splenocytes into Dsg3-competent immunodeficient Rag2-knockout recipients
      • Amagai M.
      • Tsunoda K.
      • Suzuki H.
      • Nishifuji K.
      • Koyasu S.
      • Nishikawa T.
      Use of autoantigen-knockout mice in developing an active autoimmune disease model for pemphigus.
      ;
      • Tsunoda K.
      • Ota T.
      • Aoki M.
      • Yamada T.
      • Nagai T.
      • Nakagawa T.
      • et al.
      Induction of pemphigus phenotype by a mouse monoclonal antibody against the amino-terminal adhesive interface of desmoglein 3.
      ;
      • Takahashi H.
      • Amagai M.
      • Nishikawa T.
      • Fujii Y.
      • Kawakami Y.
      • Kuwana M.
      Novel system evaluating in vivo pathogenicity of desmoglein 3-reactive T cell clones using murine pemphigus vulgaris.
      Transfer of Dsg3 knockout splenocytes into immunodeficient Rag2-knockout, Dsg3-competent recipients
      • Aoki-Ota M.
      • Tsunoda K.
      • Ota T.
      • Iwasaki T.
      • Koyasu S.
      • Amagai M.
      • et al.
      A mouse model of pemphigus vulgaris by adoptive transfer of naive splenocytes from desmoglein 3 knockout mice.
      ;
      • Kawasaki H.
      • Tsunoda K.
      • Hata T.
      • Ishii K.
      • Yamada T.
      • Amagai M.
      Synergistic pathogenic effects of combined mouse monoclonal anti-desmoglein 3 IgG antibodies on pemphigus vulgaris blister formation.
      Study the role of HLA molecules in loss of self-tolerance against human Dsg3Immunization of humanized HLA-transgenic, MHC class II knock-out DBA/1J mice with human Dsg3
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      ;
      • Schmidt T.
      • Willenborg S.
      • Hünig T.
      • Deeg C.A.
      • Sonderstrup G.
      • Hertl M.
      • et al.
      Induction of T regulatory cells by the superagonistic anti-CD28 antibody D665 leads to decreased pathogenic IgG autoantibodies against desmoglein 3 in a HLA-transgenic mouse model of pemphigus vulgaris.
      BPCharacterize human COL17-specific T and B cells in initiation and effector phases of diseaseHuman COL17 immunization of wild-type mice by skin grafting from humanized COL17-transgenic mice
      • Olasz E.B.
      • Roh J.
      • Yee C.L.
      • Arita K.
      • Akiyama M.
      • Shimizu H.
      • et al.
      Human bullous pemphigoid antigen 2 transgenic skin elicits specific IgG in wild-type mice.
      Human COL17 immunization of wild-type mice by skin grafting from humanized COL17-transgenic mice and subsequent transfer of splenocytes in COL17-humanized Rag2-knockout mice
      • Ujiie H.
      • Shibaki A.
      • Nishie W.
      • Sawamura D.
      • Wang G.
      • Tateishi Y.
      • et al.
      A novel active mouse model for bullous pemphigoid targeting humanized pathogenic antigen.
      EBACharacterize loss of self-tolerance against COL7 and the mechanisms of autoantibody-induced tissue damageImmunization of SJL/J mice with mouse GST-tagged COL7C
      • Ludwig R.J.
      • Recke A.
      • Bieber K.
      • Müller S.
      • de Castro Marques A.
      • Banczyk D.
      • et al.
      Generation of antibodies of distinct subclasses and specificity is linked to H2s in an active mouse model of epidermolysis bullosa acquisita.
      ;
      • Sitaru C.
      • Chiriac M.T.
      • Mihai S.
      • Büning J.
      • Gebert A.
      • Ishiko A.
      • et al.
      Induction of complement-fixing autoantibodies against type VII collagen results in subepidermal blistering in mice.
      DHStudy the role of HLA molecules in disease induction after gluten-sensitizationGluten-sensitization of HLA-DQ8–transgenic, MHC class II knockout NOD mice
      • Marietta E.
      • Black K.
      • Camilleri M.
      • Krause P.
      • Rogers R.S.
      • David C.
      • et al.
      A new model for dermatitis herpetiformis that uses HLA-DQ8 transgenic NOD mice.
      Abbreviations: BP, bullous pemphigoid; COL, collagen; DH, dermatitis herpetiformis; Dsg, desmoglein; EBA, epidermolysis bullosa acquisita; GST, glutathione S-transferase; MHC, major histocompatibility complex; NOD, nonobese diabetic; PV, pemphigus vulgaris.

      Mouse Models for PV

      In PV, autoantibodies directed against desmogleins (Dsg3 and Dsg1) cause loss of keratinocyte adhesion, resulting in blisters and erosions of the skin and mucous membranes. In most PV patients, autoantibody titers correlate with the clinical activity, indicating a critical role of autoantibodies in disease pathogenesis. Moreover, several in vitro and in vivo studies have clearly shown the pathogenic relevance of Dsg3-reactive IgG autoantibody (
      • Amagai M.
      • Stanley J.R.
      Desmoglein as a target in skin disease and beyond.
      ). To study the mechanisms leading to generation of pathogenic autoantibodies in PV,
      • Amagai M.
      • Tsunoda K.
      • Suzuki H.
      • Nishifuji K.
      • Koyasu S.
      • Nishikawa T.
      Use of autoantigen-knockout mice in developing an active autoimmune disease model for pemphigus.
      developed an active disease model using Dsg3–/– mice (
      • Koch P.J.
      • Mahoney M.G.
      • Ishikawa H.
      • Pulkkinen L.
      • Uitto J.
      • Shultz L.
      • et al.
      Targeted disruption of the pemphigus vulgaris antigen (desmoglein 3) gene in mice causes loss of keratinocyte cell adhesion with a phenotype similar to pemphigus vulgaris.
      ) that lack an established self-tolerance against Dsg3. Isolated splenocytes from Dsg3-immunized or naïve Dsg3–/– mice were transferred into Rag2-knockout, but Dsg3-competent, recipients to induce a Dsg3-specific autoimmune response in vivo (
      • Amagai M.
      • Tsunoda K.
      • Suzuki H.
      • Nishifuji K.
      • Koyasu S.
      • Nishikawa T.
      Use of autoantigen-knockout mice in developing an active autoimmune disease model for pemphigus.
      ,
      • Aoki-Ota M.
      • Tsunoda K.
      • Ota T.
      • Iwasaki T.
      • Koyasu S.
      • Amagai M.
      • et al.
      A mouse model of pemphigus vulgaris by adoptive transfer of naive splenocytes from desmoglein 3 knockout mice.
      ). This model allowed the stable production of a panel of Dsg3-specific autoantibodies that bind to Dsg3 in vivo. Some of these autoantibodies were also able to induce a PV-like phenotype in wild-type mice.
      Using this active mouse model, the same group demonstrated that single Dsg3-specific CD4+ T-cell clones are able to induce a clinical phenotype in recipient mice by activating Dsg3-reactive B cells (
      • Takahashi H.
      • Amagai M.
      • Nishikawa T.
      • Fujii Y.
      • Kawakami Y.
      • Kuwana M.
      Novel system evaluating in vivo pathogenicity of desmoglein 3-reactive T cell clones using murine pemphigus vulgaris.
      ). Further work with monoclonal autoantibodies isolated from B-cell hybridomas that were generated in this model showed that each Dsg3-specific autoantibody has distinct pathogenic potencies (
      • Tsunoda K.
      • Ota T.
      • Aoki M.
      • Yamada T.
      • Nagai T.
      • Nakagawa T.
      • et al.
      Induction of pemphigus phenotype by a mouse monoclonal antibody against the amino-terminal adhesive interface of desmoglein 3.
      ). Among the different isolated monoclonal autoantibodies, AK23 could induce blister formation after passive transfer of AK23 into neonatal wild-type mouse or by inoculation of AK23-producing hybridoma cells into Rag-2–/– recipient mice. AK23 recognizes a calcium-dependent conformational epitope located at the adhesive interface in the N-terminal domain of Dsg3 (
      • Tsunoda K.
      • Ota T.
      • Aoki M.
      • Yamada T.
      • Nagai T.
      • Nakagawa T.
      • et al.
      Induction of pemphigus phenotype by a mouse monoclonal antibody against the amino-terminal adhesive interface of desmoglein 3.
      ), indicating that one highly potent pathogenic autoantibody alone can induce a blistering phenotype in PV. However, in another study by Kawasaki et al. a combination of several weakly pathogenic autoantibodies generated in the same model was shown to also induce a PV phenotype in mice, pointing to potential synergistic effects of polyclonal Dsg3-specific autoantibodies in disease induction (Figure 2) (
      • Kawasaki H.
      • Tsunoda K.
      • Hata T.
      • Ishii K.
      • Yamada T.
      • Amagai M.
      Synergistic pathogenic effects of combined mouse monoclonal anti-desmoglein 3 IgG antibodies on pemphigus vulgaris blister formation.
      ).
      Figure 2
      Figure 2Dsg3-specific autoantibodies show a synergistic effect when used in combination. In an active disease model of PV established by
      • Amagai M.
      • Tsunoda K.
      • Suzuki H.
      • Nishifuji K.
      • Koyasu S.
      • Nishikawa T.
      Use of autoantigen-knockout mice in developing an active autoimmune disease model for pemphigus.
      , Dsg3–/– mice were immunized with mouse Dsg3, and splenocytes were subsequently transferred into Rag2 immunodeficient knockout mice to generate B cells producing a panel of polyclonal Dsg3-specific antibodies. Mice inoculated with hybridoma cells producing a weakly pathogenic Dsg3-specific antibody (NAK1) did not develop an apparent PV phenotype. In contrast, when mice were inoculated with a combination of several hybridoma cells (NAK1 + NAK2 + NAK7 + NAK11) they developed a phenotype similar to PV including patchy hair loss, IgG deposition in the oral mucosa, and suprabasilar acantholysis in the skin. Scale bar = 50 μm. Adapted from
      • Kawasaki H.
      • Tsunoda K.
      • Hata T.
      • Ishii K.
      • Yamada T.
      • Amagai M.
      Synergistic pathogenic effects of combined mouse monoclonal anti-desmoglein 3 IgG antibodies on pemphigus vulgaris blister formation.
      with permission from Elsevier. Dsg3, desmoglein 3; PV, pemphigus vulgaris.
      Because PV patients show a high prevalence of distinct HLA-DRB1 alleles such as HLA-DRB1*04:02, DRB1*14:04, and DQB1*05:03,
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      generated a humanized HLA-class II–transgenic mouse in which antigen presentation to CD4+ T cells is restricted to human HLA alleles, which are highly prevalent in PV, thus allowing characterization of the loss of self-tolerance against human Dsg3 by CD4+ T cells in an HLA-restricted in vivo model system (
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      ). Mice were generated by introducing transgenic constructs containing HLA-DRA1*01:01, -DRB1*04:02, and HLA-DQA1*03:01, -DQB1*03:02 (DQ8) into mice lacking functional endogenous murine major histocompatibility complex (MHC) class II (I-Aß–/–) (Figure 3). After immunization of HLA-DRB1*04:02-transgenic mice with immunodominant Dsg3 peptides, a CD4+ T cell-dependent immune response against human Dsg3 with the production of pathogenic Dsg3 reactive IgG antibodies was observed. However, immunization of mice transgenic for a PV-unrelated HLA-molecule (HLA-DRB1*04:01) did not induce a Dsg3-specific antibody response, indicating that recognition of distinct Dsg3 peptides by CD4+ T cells is highly specific for certain HLA molecules that are highly prevalent in PV (
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      ). With the same model it was recently shown that CD4+CD25+FoxP3+ T regulatory cells exert a down-regulatory effect on the humoral Dsg3-specific immune response, which supports the hypothesis that the Dsg3-specific CD4+ T-cell–dependent immune pathogenesis of PV is modulated by T regulatory cells (
      • Schmidt T.
      • Willenborg S.
      • Hünig T.
      • Deeg C.A.
      • Sonderstrup G.
      • Hertl M.
      • et al.
      Induction of T regulatory cells by the superagonistic anti-CD28 antibody D665 leads to decreased pathogenic IgG autoantibodies against desmoglein 3 in a HLA-transgenic mouse model of pemphigus vulgaris.
      ).
      Figure 3
      Figure 3Genotypying of HLA transgenes in a humanized PV mouse model.
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      established an HLA-transgenic mouse model by introducing HLA-DRB1, HLA-DQB1, and human CD4 co-receptor into mice lacking endogenous expression of mouse major histocompatibility complex class II (I-Aβ). Transgene expression on the immune cell surface was validated by flow cytometric analysis. Transgenic mice (solid line) express human CD4, HLA-DR, and HLA-DQ but do not express I-Aβ compared with wild-type mice (dotted line), which showed no transgene expression.
      Adapted with permission from
      • Eming R.
      • Hennerici T.
      • Bäcklund J.
      • Feliciani C.
      • Visconti K.C.
      • Willenborg S.
      • et al.
      Pathogenic IgG antibodies against desmoglein 3 in pemphigus vulgaris are regulated by HLA-DRB1* 04: 02–restricted T cells.
      , Copyright 2014. The American Association of Immunologists, Inc. FITC, fluorescein isothiocyanate; PE, phycoerythrin; PV, pemphigus vulgaris.

      Animal Models for BP

      BP is a subepidermal blistering disease characterized by autoantibodies against antigens in the epidermal basement membrane, mainly type XVII collagen (COL-17)/BP180 (BP antigen II of 180 kDa) and the intracellular plakin BP230 (BP antigen I of 230 kDa). Autoantibodies from BP patients fail to recognize mouse COL-17 in passive transfer models due to of differences in the amino acid sequences between humans and mice. Therefore, humanized mouse models for BP have been used to study disease mechanisms in vivo (
      • Nishie W.
      • Sawamura D.
      • Goto M.
      • Ito K.
      • Shibaki A.
      • McMillan J.R.
      • et al.
      Humanization of autoantigen.
      ).
      • Olasz E.B.
      • Roh J.
      • Yee C.L.
      • Arita K.
      • Akiyama M.
      • Shimizu H.
      • et al.
      Human bullous pemphigoid antigen 2 transgenic skin elicits specific IgG in wild-type mice.
      established an active BP model using transgenic mice expressing human COL-17 in the murine basement membrane. Transgenic mice were generated by crossing COL-17 knockout mice with animals expressing human COL-17 under the control of the human keratin-14 promotor, allowing tissue-specific expression of human COL-17 only in the basement membrane of transgenic mice (
      • Olasz E.B.
      • Roh J.
      • Yee C.L.
      • Arita K.
      • Akiyama M.
      • Shimizu H.
      • et al.
      Human bullous pemphigoid antigen 2 transgenic skin elicits specific IgG in wild-type mice.
      ). Skin grafts from COL-17-transgenic mice were then transplanted onto syngeneic wild-type recipients to induce a strong COL-17–specific IgG response with autoantibodies able to induce subepidermal blistering in the skin graft.
      The model was further developed by
      • Ujiie H.
      • Shibaki A.
      • Nishie W.
      • Sawamura D.
      • Wang G.
      • Tateishi Y.
      • et al.
      A novel active mouse model for bullous pemphigoid targeting humanized pathogenic antigen.
      , who transferred splenocytes from human COL-17-immunized wild-type mice into immunodeficient Rag-2–/–/COL17–humanized recipients. In this model, the depletion of CD4+ T cells from the COL-17–immunized mice suppressed the production of COL-17–specific IgG antibodies, whereas the depletion of CD8+ T cells showed no effects, indicating that CD4+ T cells, but not CD8+ T cells, are essential for the production of antibodies against human COL-17 in the humanized BP model.

      Animal Models for EBA

      In EBA, autoantibodies bind to type VII collagen (COL-7), an anchoring fibril protein of the dermal-epidermal junction, leading to skin fragility and blistering of the skin and mucous membranes. Most EBA sera recognizes the noncollagenous-1 domain of COL-7. Animal models for EBA are mainly based either on the passive transfer of COL-7–specific antibodies (derived from human or other species like rabbits) or on the direct immunization of mice with the autoantigen (see
      • Kasperkiewicz M.
      • Sadik C.D.
      • Bieber K.
      • Ibrahim S.M.
      • Manz R.A.
      • Schmidt E.
      • et al.
      Epidermolysis bullosa acquisita: from pathophysiology to novel therapeutic options.
      for review). In the active immunization-induced EBA mouse model, wild-type mice are immunized with an immunogenic peptide of the COL-7 epitope from the murine noncollagenous-1 domain. After 4–8 weeks mice start showing a phenotype similar to EBA, with subepidermal blister formation mainly located at the ears, snout, and around the eyes (
      • Ludwig R.J.
      Model systems duplicating epidermolysis bullosa acquisita: a methodological review.
      ,
      • Sitaru C.
      • Chiriac M.T.
      • Mihai S.
      • Büning J.
      • Gebert A.
      • Ishiko A.
      • et al.
      Induction of complement-fixing autoantibodies against type VII collagen results in subepidermal blistering in mice.
      ). This model is used to study both the initial autoimmune events in loss of self-tolerance leading to development of autoreactive COL-7–specific T and B cells and to study mechanisms of autoantibody-induced tissue damage and inflammation. For instance,
      • Ludwig R.J.
      • Recke A.
      • Bieber K.
      • Müller S.
      • de Castro Marques A.
      • Banczyk D.
      • et al.
      Generation of antibodies of distinct subclasses and specificity is linked to H2s in an active mouse model of epidermolysis bullosa acquisita.
      showed that the induction and the severity of the EBA-like phenotype strongly depends on the mouse’s MHC haplotype, because mouse strains carrying the H2s haplotype are more prone to develop experimental EBA after COL-7 immunization and show the highest disease severity compared with other inbred mouse strains (
      • Ludwig R.J.
      • Recke A.
      • Bieber K.
      • Müller S.
      • de Castro Marques A.
      • Banczyk D.
      • et al.
      Generation of antibodies of distinct subclasses and specificity is linked to H2s in an active mouse model of epidermolysis bullosa acquisita.
      ) (Figure 4).
      Figure 4
      Figure 4Disease severity is dependent on MHC haplotype in an immunization-induced mouse model of EBA. Different mouse strains were immunized with an immunogenic peptide from the murine collagen type VII (COL7C) to induce experimental EBA with erosions, crusts, and alopecia mainly localized at the ears, snout, and around the eyes. Representative phenotypes from three different strains are shown. After COL7C immunization of SJL/J mice carrying the MHC haplotype H2s a severe disease phenotype was induced, whereas C57Bl/6 mice carrying a different MHC haplotype showed no clinical signs of EBA. Female MRL/MpJ mice carrying the H2k haplotype were also susceptible to EBA induction.
      Adapted from
      • Ludwig R.J.
      • Recke A.
      • Bieber K.
      • Müller S.
      • de Castro Marques A.
      • Banczyk D.
      • et al.
      Generation of antibodies of distinct subclasses and specificity is linked to H2s in an active mouse model of epidermolysis bullosa acquisita.
      , with permission from Elsevier. EBA, epidermolysis bullosa aquisita; MHC, major histocompatibility complex.

      Mouse Models for DH

      DH is a blistering skin disease strongly associated with gluten intolerance that is clinically characterized by an intensively pruritic papulovesicular rash on the skin. Immunofluorescence shows IgA deposition at the tips of the papillary dermis, and gluten-induced IgA autoantibodies are directed against transglutaminase-2 and -3 (
      • Kárpáti S.
      Dermatitis herpetiformis.
      ). On the basis of the strong genetic association of DH with HLA-DQ2 and HLA-DQ8,
      • Marietta E.
      • Black K.
      • Camilleri M.
      • Krause P.
      • Rogers R.S.
      • David C.
      • et al.
      A new model for dermatitis herpetiformis that uses HLA-DQ8 transgenic NOD mice.
      used autoimmune-prone nonobese diabetic mice lacking the endogenous murine MHC class II (I-Aß–/–) and introduced the human HLA-DQ8 transgene to establish a transgenic model in which antigen presentation to CD4+ T cells is restricted to HLA-DQ8. Blister formation, neutrophil infiltration in the dermis, and deposition of IgA antibodies at the dermal-epidermal junction were observed in 16% of HLA-DQ8–transgenic nonobese diabetic mice that were sensitized to gluten, whereas no blistering or IgA deposition was observed in non–HLA-DQ8–transgenic mice, indicating that HLA-DQ8 is required for blister formation (
      • Marietta E.
      • Black K.
      • Camilleri M.
      • Krause P.
      • Rogers R.S.
      • David C.
      • et al.
      A new model for dermatitis herpetiformis that uses HLA-DQ8 transgenic NOD mice.
      ).

      Conclusion

      The current understanding of the pathophysiology of AIBDs has been greatly increased by studies that have been performed in mouse models for these disorders. The current models summarized in this article are based on the active immunization with recombinant autoantigens. The mouse models focus on various aspects of the autoimmune cascade finally resulting in the production of antibodies directed against the antigen of interest. In most cases, the mice develop a clinical phenotype resembling certain aspects of the human disease. However, so far there is no spontaneous mouse model for AIBD, which limits the significance of the established in vivo systems with regard to modeling the human situation.

      Multiple Choice Questions

      • 1.
        Which of the following is not characteristic of all autoimmune blistering diseases?
        • A.
          Blisters on the skin and/or mucous membranes
        • B.
          IgG autoantibodies
        • C.
          Autoantibodies against autoantigens in the skin
        • D.
          Loss of self-tolerance
      • 2.
        Which knockout mice are immunized with autoantigen in the active disease model of pemphigus vulgaris?
        • A.
          Dsg1–/– mice
        • B.
          COL7–/– mice
        • C.
          Dsg3–/– mice
        • D.
          Dsg2–/– mice
      • 3.
        Which domain of type VII collagen is used for the immunization-induced model for epidermolysis bullosa acquisita?
        • A.
          NC1
        • B.
          NC2
        • C.
          NC3
        • D.
          NC4
      • 4.
        What is/are the main autoantigen(s) in bullous pemphigoid?
        • A.
          COL17/BP180
        • B.
          BP230
        • C.
          COL17/BP180 and BP230
        • D.
          COL17/BP180 and BP250
      • 5.
        Which Dsg3-specific antibody can induce a pemphigus vulgaris-resembling phenotype in wild-type mice?
        • A.
          AK7
        • B.
          AK47
        • C.
          AK3
        • D.
          AK23

      Conflict of Interest

      The authors state no conflict of interest.

      Supplementary Material

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