In vitro organ culture model for mucous membrane pemphigoid

Autoimmunity against laminin 332

Laminin 332 is a heterotrimeric structural protein of the basal membrane zone (BMZ) of the skin and adjacent mucosal tissues. The importance of laminin 332 for the structural integrity of the BMZ is demonstrated by mutations in any of the three genes encoding for its three chains causing variants of junctional epidermolysis bullosa. Autoimmunity against laminin 332 is observed in mucous membrane pemphigoid (MMP) and in the rare patients with orf-induced pemphigoid. MMP is an autoimmune blistering disease with predominant mucosal manifestations and autoantibodies against the BMZ of the skin and orifice-close mucous membranes. The main autoantigens of MMP are type XVII collagen (BP180) and laminin 332 targeted in about 80% and 10-20% of patients, respectively. An increasing number of studies has highlighted the association of anti-laminin 332 MMP and malignancies that can be revealed in about a quarter of these patients. This data has led to the recommendation of current guidelines to assay for anti-laminin 332 reactivity in all MMP patients. The present review focuses on anti-laminin 332 MMP describing clinical features, its pathophysiology, and detection of serum anti-laminin 332 IgG. In addition, the available data about the occurrence of malignancies in anti-laminin 332 MMP, the underlying tumor entities, and its biology are detailed.

Mucous membrane pemphigoid

Mucous membrane pemphigoid (MMP) is a clinically and immunopathologically heterogenous disease with an incidence of about 2/million inhabitants/year in central Europe. Pemphigoid diseases are characterized by autoantibodies against structural proteins of the epidermis and/or surface-close epithelia. MMP has been defined as pemphigoid disease with predominant mucosal lesions. Most frequently, the oral cavity and the conjunctivae are affected. Lesions outside the mouth tend to heal with scarring leading to visual impairment and finally blindness, as well as, more rarely, impairment of breathing and food intake. Autoantibodies target BP180 (collagen type XVII), laminin 332, BP230 (nearly always in conjunction with other antigens), and type VII collagen in about 75%, 10-20%, 10-30%, and <5% of MMP patients, respectively. While the main autoantibody isotype is IgG, additional, and less frequently, exclusive IgA autoantibodies can be detected in the majority of patients. Assaying for anti-laminin 332 reactivity is pivotal, since in about a quarter of patients with anti-laminin 332 MMP, a malignancy, mainly solid cancers, is associated. The pathophysiology of MMP is yet incompletely understood. A recent mouse model of anti-laminin 332 MMP replicating characteristic clinical and immunopathological findings of the human disease may be helpful to close this knowledge gap. Diagnosis is established by the clinical picture with predominant mucosal lesions and visualization of tissue-bound anti-basement membrane zone antibodies by direct immunofluorescence microscopy. In recent S3 guidelines initiated by the European Academy of Dermatology and Venereology, the clinical spectrum and diagnostic strategies are detailed. In addition, treatment regimens for different clinical situations including patients with exclusive oral or ocular involvement are outlined. Future studies are needed to better understand the clinal complexity and associations as well as to establish widely available diagnostic assays and evidence-based therapeutic strategies.

European Guidelines (S3) on diagnosis and management of mucous membrane pemphigoid, initiated by the European Academy of Dermatology and Venereology - Part II

This guideline has been initiated by the task force Autoimmune Blistering Diseases of the European Academy of Dermatology and Venereology, including physicians from all relevant disciplines and patient organizations. It is a S3 consensus-based guideline that systematically reviewed the literature on mucous membrane pemphigoid (MMP) in the MEDLINE and EMBASE databases until June 2019, with no limitations on language. While the first part of this guideline addressed methodology, as well as epidemiology, terminology, aetiology, clinical presentation and outcome measures in MMP, the second part presents the diagnostics and management of MMP. MMP should be suspected in cases with predominant mucosal lesions. Direct immunofluorescence microscopy to detect tissue-bound IgG, IgA and/or complement C3, combined with serological testing for circulating autoantibodies are recommended. In most patients, serum autoantibodies are present only in low levels and in variable proportions, depending on the clinical sites involved. Circulating autoantibodies are determined by indirect IF assays using tissue substrates, or ELISA using different recombinant forms of the target antigens or immunoblotting using different substrates. The major target antigen in MMP is type XVII collagen (BP180), although in 10-25% of patients laminin 332 is recognized. In 25-30% of MMP patients with anti-laminin 332 reactivity, malignancies have been associated. As first-line treatment of mild/moderate MMP, dapsone, methotrexate or tetracyclines and/or topical corticosteroids are recommended. For severe MMP, dapsone and oral or intravenous cyclophosphamide and/or oral corticosteroids are recommended as first-line regimens. Additional recommendations are given, tailored to treatment of single-site MMP such as oral, ocular, laryngeal, oesophageal and genital MMP, as well as the diagnosis of ocular MMP. Treatment recommendations are limited by the complete lack of high-quality randomized controlled trials.

[Mucous membrane pemphigoid with ocular involvement. Part I: Clinical manifestations, pathogenesis and diagnosis]

Mucous membrane pemphigoid is a subepidermal blistering autoimmune disorder characterized by predominant involvement of mucous membranes and the presence of autoantibodies against proteins of the dermal-epidermal junction. Lesions most frequently develop in the oral cavity followed, in descending order of frequency, by conjunctiva, nasopharynx, the anogenital region, skin, larynx, and oesophagus. When the lesions are restricted to the conjunctiva, the term ocular pemphigoid may be applied. Cicatrization of the plica is considered a pathognomonic sign in early disease. Recurrent conjunctival inflammation results in subepithelial fibrosis, which leads to fornix shortening, symblepharon formation and subsequent trichiasis and entropion. Even in the absence of conjunctival inflammation, ankyloblepharon may occur. In end stage disease, limbal stem cell deficiency, tear deficiency, and lid malpositions may occur and result in a total keratinization of the ocular surface. The diagnosis is based on clinical findings and the detection of linear deposits of IgG and/or IgA and/or C3 at the dermal-epidermal junction by direct immunofluorescence microscopy of a perilesional biopsy. Autoantibodies (against type XVII and VII collagen, laminin 5 and 6, alpha6beta4 integrin, BP230) have been detected in patient serum. In the case of ocular involvement, preferential reactivity against beta4 integrin has been described.

Immunopathology and molecular diagnosis of autoimmune bullous diseases

Autoimmune bullous diseases are associated with autoimmunity against structural components maintaining cell-cell and cell matrix adhesion in the skin and mucous membranes. Pemphigus diseases are characterized by autoantibodies against the intercellular junctions and intraepithelial blisters. In pemphigoid diseases and epidermolysis bullosa acquisita, sub-epidermal blistering is associated with autoantibodies targeting proteins of the hemidesmosomal anchoring complex. The autoantigens in autoimmune blistering diseases have been extensively characterized over the past three decades. In general, the pathogenicity of autoantibodies, already suggested by clinical observations, has been conclusively demonstrated experimentally. Detection of tissue-bound and circulating serum autoantibodies and characterization of their molecular specificity is mandatory for the diagnosis of autoimmune blistering diseases. For this purpose, various immunofluorescence methods as well as immunoassays, including immunoblotting, enzyme-linked immunosorbent assay and immunoprecipitation have been developed. This review article describes the immunopathological features of autoimmune bullous diseases and the immunological and molecular tests used for their diagnosis and monitoring.

Pathogenic human monoclonal antibody against desmoglein 3

Pemphigus vulgaris (PV) is a potentially fatal autoimmune mucocutaneous disease associated with production of IgG autoantibodies to desmoglein 3 (Dsg3), a 130-kDa epidermal cadherin protein. The binding of pathogenic antibody to Dsg3 on epidermal keratinocytes leads to loss of intercellular adhesion and results in intraepithelial blister formation. Here, we describe a human monoclonal antibody, PVMAB786, a Dsg3-specific IgG4 antibody, from an untreated patient with active PV. The antibody reacts with a 130-kDa protein on keratinocyte cell surfaces and recombinant Dsg3 protein, but not desmoglein 1 protein. PVMAB786 induces acantholysis in normal human skin and mucous membranes and induces a clinical and histological profile similar to human PV when injected into neonatal mice. PVMAB786 will be a valuable tool in identifying the role of Dsg3 in epithelial cell adherence and acantholysis, mechanisms of Dsg3 processing/presentation and V gene and isotype usage in PV pathogenesis.

Autoantibodies to human alpha6 integrin in patients with bullous pemphigoid

Bullous pemphigoid (BP) is characterized immunologically by tissue-bound and circulating autoantibodies targeting the hemidesmosomal proteins BP230 and BP180. Recent evidence suggests a pathophysiological role for autoantibodies against alpha6 integrin in the subepidermal blister formation of oral pemphigoid. The objective of our study was to investigate the presence of anti-alpha6 integrin antibodies in patients with classical BP. The autoantibody profiles of 30 patients with BP, 10 patients with pemphigus vulgaris, and 20 healthy persons were identified. With the use of PeptideStructure and PlotStructure software, four different antigenic epitopes for alpha6 integrin were predicted, and their fusion recombinant constructs were prepared in an E. coli expression system. Sera were tested for alpha6 integrin autoantibodies by an ELISA technique. Altogether, 52% of the patients with BP displayed circulating antibodies against at least one recombinant protein. Our findings provide the first evidence for the presence of anti-alpha6 integrin antibodies in patients with classical BP.

Bullous pemphigoid antigen II (BP180) and its soluble extracellular domains are major autoantigens in mucous membrane pemphigoid: the pathogenic relevance to HLA class II alleles and disease severity

BACKGROUND

Mucous membrane pemphigoid (MMP), a chronic autoimmune subepithelial blistering disease, is associated with circulating IgG and/or IgA autoantibodies against several basement membrane zone antigens. The heterogeneity of clinical presentation and diversity of target autoantigens have contributed to difficulties in characterizing this condition immunologically.

OBJECTIVES

To analyse serum autoantibody profile and HLA class II alleles in MMP patients and to correlate this with the clinical presentation of disease.

METHODS

Well-defined subgroups consisting of 124 patients with MMP were examined for IgG and IgA reactivity with immunoblotting using human epidermal, dermal and placental amnion proteins. The results were further analysed on the basis of detailed clinical (sites of involvement and disease severity) and immunopathological criteria (immunofluorescence study and HLA class II alleles).

RESULTS

Immunoblot assay revealed that the majority of MMP patients had IgG (93 of 124, 75%) and/or IgA autoantibodies (63 of 124, 51%) to BP180 (including its soluble ectodomains, 120-kDa LAD-1 and 97-kDa LABD97 antigens). Other antigens targeted predominantly by IgG autoantibodies included: BP230 in 34 (27%), beta4 integrin in 26 (21%), and laminin 5 in three (2%). All the BP230+ sera and 23 (88%) beta4 integrin+ sera also reacted with at least one of the BP180 antigens. Over 85% of patients with reactivity to beta4 integrin had ocular involvement. In most cases of MMP, more severe clinical features were associated with antibody reactivity to multiple basement membrane zone antigens, as well as reactivity to multiple BP180 component antigens. Dual BP180/LAD-1 reactivity with IgG and IgA was associated with a more severe phenotype. In addition, the subset-dependent autoantibody reactivity correlated well with specific HLA class II alleles, DQB1*0301, DRB1*04 and DRB1*11.

CONCLUSIONS

Our results confirmed that BP180 is a major autoantigen targeted by the sera of patients with MMP. The disease-prevalent HLA class II alleles and humoral autoimmune response against the particular subsets of antigenic epitope(s) within BP180 ectodomain may contribute to the clinicopathological significance and disease severity of MMP.

Mechanisms of blister induction by autoantibodies

Autoimmune diseases are characterized by defined self-antigens, organ specificity, autoreactive T cells and/or autoantibodies that can transfer disease. Autoimmune blistering diseases are organ-specific autoimmune diseases associated with an immune response directed to structural proteins mediating cell-cell and cell-matrix adhesion in the skin. While both autoreactive T and B cells have been detected and characterized in patients with autoimmune blistering diseases, current evidence generally supports a pathogenic role of autoantibodies for blister formation. The immunopathology associated with blisters induced by autoantibodies relies on several mechanisms of action. Autoantibodies from patients with pemphigus diseases can exert a direct effect just by binding to their target mediated by steric hindrance and/or by triggering the transduction of a signal to the cell. In most subepidermal autoimmune blistering conditions, in addition to the binding to their target antigen, autoantibodies need to interact with factors of the innate immune system, including the complement system and inflammatory cells, in order to induce blisters. Generally, decisive progress has been made in the characterization of the mechanisms of blister formation in autoimmune skin diseases. However, various aspects, including the exact contribution of steric hindrance and signal transduction for pemphigus IgG-induced acantholysis or the fine tuning of the inflammatory cascade triggered by autoantibodies in some subepidermal blistering diseases, still need to be addressed. Understanding the mechanisms by which autoantibodies induce blisters should facilitate the development of more specific therapeutic strategies of autoimmune blistering diseases.

Autoantibodies against human epithelial cells and endothelial cells after severe acute respiratory syndrome (SARS)-associated coronavirus infection

The severe acute respiratory syndrome (SARS) is caused by infection with the SARS‐associated coronavirus (SARS‐CoV) and characterized by severe pulmonary inflammation and fibrosis. In this study, the development of autoantibodies against human epithelial cells and endothelial cells in patients with SARS at different time periods (the first week: phase I, 1 month after the disease onset: phase II/phase III) were investigated. Antibodies in sera of patients and healthy controls against: (1) A549 human pulmonary epithelial cell‐line, (2) human umbilical venous endothelial cells (HUVEC), (3) primary human pulmonary endothelial cells (HPEC) were detected by cell‐based ELISA and indirect immunofluorescence staining. The results revealed that serum levels of IgG anti‐A549 cells antibodies, IgG anti‐HUVEC antibodies, and IgM anti‐HPEC antibodies were significantly higher in SARS patients at phase II/phase III than those in healthy controls. Sera from SARS patients at phase II/phase III could mediate complement dependent cytotoxicity against some A549 cells and HPEC. It is concluded that some autoantibodies against human epithelial cells and endothelial cells would be developed after SARS‐CoV infection and this phenomenon may indicate post‐infectious cellular injury and also induce SARS‐induced immunopathology. J. Med. Virol. 77:1–7, 2005. © 2005 Wiley‐Liss, Inc.

Profile of autoantibody to basement membrane zone proteins in patients with mucous membrane pemphigoid: long-term follow up and influence of therapy

Mucous membrane pemphigoid (MMP) is an autoimmune mucocutaneous blistering disease characterized by autoantibodies to components within the basement membrane zone. In this study, we report the titers of autoantibodies to antigens in the BMZ, in the sera of 13 patients, treated with intravenous immunoglobulin as monotherapy over a consecutive 18-month period. Using bovine gingiva lysate as substrate in an immunoblot assay, autoantibodies to human bullous pemphigoid antigens (BPAg1 and BPAg2), human beta4 integrin, and laminin 5 were measured. A statistically significant (P < 0.05) decline in the autoantibody titers to beta4-integrin was observed after 3.42 months of initiating the IVIg therapy. These titers were undetectable after 13 months of therapy. The titers of antibodies to BPAg1 and BPAg2 did not correlate with disease activity or response to therapy. Antibodies to laminins were not detected. In patients with MMP, autoantibody titers to beta4-integrin correlate with disease activity and response to therapy.

Treatment of oral pemphigoid with intravenous immunoglobulin as monotherapy. Long-term follow-up: influence of treatment on antibody titres to human alpha6 integrin

SUMMARY

Oral pemphigoid (OP) is a chronic autoimmune disease, involving the oral cavity, characterized by a homogenous linear deposition of immunoglobulins, complement, or both along the basement membrane zone (BMZ) and a subepithelial blister formation. The alpha6/beta4 heterodimer is an integrin family of adhesion receptors, which mediates basal cell to matrix interactions. Recent evidence suggests a pathophysiologic role for antibodies against human alpha6 integrin in blister formation in OP, in organ culture studies. Fifty percent of OP patients have been reported to experience disease progression to involve other mucosal tissues, including the eye and larynx. To prevent this extension of disease, systemic therapy with systemic corticosteroids, dapsone, and immunosuppressive agents has been recommended. The use of intravenous immunoglobulin (IVIg) in the treatment of pemphigoid has been recently described. In this study, we present the use of IVIg, in a group of seven patients, with severe OP, in whom systemic conventional treatment was contraindicated. To determine the influence of treatment on antibodies to human alpha6 integrin in OP, seven patients with OP treated with IVIg therapy and a comparable control group of seven patients with OP, treated with conventional therapy, were evaluated at monthly intervals, for a 12 consecutive month treatment period. An effective clinical response was observed in all seven patients treated with IVIg therapy, after a mean treatment period of 4.5 months. IVIg therapy induced a prolonged and sustained clinical remission in all seven patients after a mean treatment period of 26.9 months. A statistically significant difference was observed in the quality of life pre- and post-IVIg therapy (P < 0.001). Both the study and the control groups had a very similar initial serological response to treatment. A statistically significant reduction in the antibody titres was observed after four months of treatment, in both groups (P = 0.015). Thereafter, patients treated with IVIg therapy had a faster rate of decline in the antibody titres, and the difference in the rate of decline between the study and control groups became statistically significant after six months of treatment (P = 0.03). The use of IVIg therapy resulted in reduction of antialpha6 antibody titres and in inducing and maintaining both a sustained, clinical and serological remission.

Cicatricial pemphigoid with circulating autoantibodies to beta4 integrin, bullous pemphigoid 180 and bullous pemphigoid 230

Cicatricial pemphigoid is a heterogeneous group of autoimmune subepidermal blistering diseases associated most commonly with autoantibodies to bullous pemphigoid (BP)180 and less frequently with those to laminin 5 or type VII collagen. In addition, a few cases have been described with autoantibodies to the beta4 subunit of alpha6beta4 integrin. We describe a patient with extensive disease of ocular, oral, pharyngeal, laryngeal and genital mucous membranes that healed with scarring of conjunctivae. IgG autoantibodies bound to the dermal-epidermal junction on direct immunofluorescence (IF) microscopy and to the epidermal side of 1 mol L(-1) NaCl-split skin on indirect IF microscopy. Our patient's circulating IgG recognized a 205-kDa protein in extracts of 293T cells transfected with the beta4 subunit of alpha6beta4 integrin and in the cell extract of DJM-1 cells. Our patient's IgG and IgA autoantibodies also reacted with full-length BP180 derived from epidermal extracts and the ectodomain of BP180 (LAD-1) derived from culture supernatant of keratinocytes. In addition, a weak IgG reaction with BP230 was noted. The disease rapidly responded to dexamethasone-cyclophosphamide pulse therapy, and immunoblot reactivity to both beta4 integrin and BP180 decreased according to disease activity.