Evidence that anti-basement membrane zone antibodies in bullous eruption of systemic lupus erythematosus recognize epidermolysis bullosa acquisita autoantigen

Cutaneous manifestations of lupus erythematosus: A practical clinicopathologic review for pathologists

Accurate diagnosis of connective tissue diseases is often challenging and relies on careful correlation between clinical and histopathologic features, direct immunofluorescence studies, and laboratory workup. Lupus erythematosus (LE) is a prototype of connective tissue disease with a variety of cutaneous and systemic manifestations. Microscopically, cutaneous LE is classically characterized by an interface dermatitis, although other histopathologic patterns also exist depending on the clinical presentation, location, and chronicity of the skin lesions. In this article, we review the clinical, serologic, histopathologic, and direct immunofluorescence findings in LE-specific and LE-nonspecific skin lesions, with an emphasis on lesser known variants, newly described features, and helpful ancillary studies. This review will guide general pathologists and dermatopathologists in accurately diagnosing and subclassifying cutaneous LE.

Development of a Neo-Epitope Specific Assay for Serological Assessment of Type VII Collagen Turnover and Its Relevance in Fibroproliferative Disorders

Type VII collagen is the main component of the anchoring fibrils connecting the basement membrane to the underlying interstitial matrix. Mutations in the type VII collagen gene cause dystrophic epidermolysis bullosa. Increased levels of type VII collagen in the skin have been reported in patients with systemic sclerosis (SSc), whereas reduced levels in the airways have been related to asthma. This indicates that type VII collagen plays an important part in upholding tissue integrity and that its remodeling may lead to pathological states. The aim of this study was to investigate the role of type VII collagen remodeling in fibroproliferative disorders. We produced monoclonal antibody targeting a specific fragment of type VII collagen (C7M) released to the systemic circulation and developed a neo-epitope specific competitive enzyme-linked immunosorbent assay (ELISA). Biological relevance was evaluated in serum from patients with SSc or chronic obstructive pulmonary disease (COPD). The C7M ELISA was technically robust and specific for the C7M neo-epitope. Serum C7M levels were significantly elevated in two cohorts of patients with SSc and in patients with COPD as compared with healthy individuals (P < 0.0001). The C7M ELISA enabled quantification of type VII collagen turnover in serum. Elevated serum C7M levels indicated that the turnover rate of type VII collagen was significantly increased in patients with SSc or COPD, suggesting a pathological role. Thus, the C7M ELISA may become useful in future investigations of type VII collagen turnover in fibroproliferative disorders, and it may prove a valuable tool for evaluating novel anti-fibrotic drugs.

Blister-inducing antibodies target multiple epitopes on collagen VII in mice

Epidermolysis bullosa acquisita (EBA) is an autoimmune subepidermal blistering disease of mucous membranes and the skin caused by autoantibodies against collagen VII. In silico and wet laboratory epitope mapping studies revealed numerous distinct epitopes recognized by EBA patients' autoantibodies within the non-collagenous (NC)1 and NC2 domains of collagen VII. However, the distribution of pathogenic epitopes on collagen VII has not yet been described. In this study, we therefore performed an in vivo functional epitope mapping of pathogenic autoantibodies in experimental EBA. Animals (n = 10/group) immunized against fragments of the NC1 and NC2 domains of collagen VII or injected with antibodies generated against the same fragments developed to different extent experimental EBA. Our results demonstrate that antibodies targeting multiple, distinct epitopes distributed over the entire NC1, but not NC2 domain of collagen VII induce blistering skin disease in vivo. Our present findings have crucial implications for the development of antigen-specific B- and T cell-targeted therapies in EBA.

Epidermolysis bullosa acquisita: autoimmunity to anchoring fibril collagen

Epidermolysis bullosa acquisita (EBA) is a rare and acquired autoimmune subepidermal bullous disease of skin and mucosa. EBA includes various distinct clinical manifestations resembling genetic dystrophic epidermolysis bullosa (DEB), Bullous pemphigus, Brunsting-Perry pemphigoid, or cicatricial pemphigoid. These patients have autoantibodies against type VII collagen (C7), an integral component of anchoring fibrils (AFs), which are responsible for attaching the dermis to the epidermis. Destruction or perturbation of the normal functioning AFs clinically results in skin fragility, blisters, erosions, scars, milia, and nail loss, all features reminiscent of genetic dystrophic epidermolysis bullosa. These anti-C7 antibodies are "pathogenic" because when injected into a mouse, the mouse develops an EBA-like blistering disease. Currently, treatment is often unsatisfactory; however, some success has been achieved with colchicine, dapsone, photopheresis, plasmapheresis, infliximab, rituximab, and IVIG.

Epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a rare, acquired, chronic subepidermal bullous disease of the skin and mucosa characterized by autoantibodies to type VII collagen (C7) structures, a major component of anchoring fibrils, which attach the epidermis to the dermis. EBA patients have tissue-bound and circulating antitype C7 autoantibodies that attack type C7 and result in a reduction or perturbation of normally functioning anchoring fibrils. Patients with EBA have skin fragility, blisters, erosions, scars, milia, and nail loss, all features reminiscent of genetic dystrophic epidermolysis bullosa. These immunoglobulin G antitype C7 antibodies are pathogenic, because when they are injected into mice, the mice develop an EBA-like blistering disease. In addition to the classical mechanobullous presentation, EBA also has several other distinct clinical syndromes similar to bullous pemphigoid, Brunsting-Perry pemphigoid, or cicatricial pemphigoid. Although treatment for EBA is often unsatisfactory, some therapeutic success has been achieved with colchicine, dapsone, plasmapheresis, photopheresis, infliximab, and intravenous immunoglobulin.

Bullous systemic lupus erythematosus

Bullous systemic lupus erythematosus (BSLE) is a rare bullous dermatosis in patients with systemic lupus erythematosus. It is characterized by clinical and histologic features, resembling either bullous pemphigoid or dermatitis herpetiformis, and a heterogeneous immunologic profile, characterized by autoimmunity to components of type VII collagen, much like epidermolysis bullosa acquisita. As understanding of the pathology of this interesting dermatologic condition has evolved, so too have criteria and profiling of BSLE. The distinct clinical, histologic, and immunologic features of BSLE represent a unique bullous disease phenotype.

Cutaneous lupus and the Cutaneous Lupus Erythematosus Disease Area and Severity Index instrument

This article provides an overview of cutaneous lupus erythematosus, including classification schemes, disease subtypes, and therapy. It also describes the Cutaneous Lupus Erythematosus Disease Area and Severity Index, a novel clinical outcome instrument that quantifies cutaneous activity and damage in cutaneous lupus erythematosus.

Dermatopathology for the surgical pathologist: a pattern based approach to the diagnosis of inflammatory skin disorders (part I)

The accurate diagnosis of inflammatory conditions in dermatopathology requires integrating the histopathologic findings with the clinical features. This can be difficult when skin biopsies are seen infrequently and the terminology is unfamiliar, as in a general surgical pathology practice. This 2-part review of inflammatory cutaneous conditions presents a pattern-based approach to the diagnosis of dermatologic disorders and reviews the salient clinical and histologic features. Part I will focus on the spongiotic, psoriasiform, interface, and bullous patterns, whereas Part II will review the perivascular, vasculitis, panniculitis, and nodular and diffuse patterns.

The cartilage matrix protein subdomain of type VII collagen is pathogenic for epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is an acquired bullous disease of the skin characterized by IgG autoantibodies against type VII (anchoring fibril) collagen. We previously defined four immunodominant antigenic epitopes within the noncollagenous 1 (NC1) domain of type VII collagen. In this study, we produced an additional recombinant fusion protein from the NC1 domain corresponding to the N-terminal 227 amino acids (residues 1 to 227), which contains homology with cartilage matrix protein (CMP). Using enzyme-linked immunosorbent assay and immunoblot analysis, we tested sera from EBA patients (n = 32), bullous systemic lupus erythematosus patients (n = 3), bullous pemphigoid patients (n = 15), and normal humans (n = 12). Twenty-six of 32 EBA sera and two of three bullous systemic lupus erythematosus sera reacted with the CMP domain, whereas none of the control sera did. Affinity-purified anti-CMP EBA antibodies injected into hairless mice produced the clinical, histological, immunological, and ultrastructural features of EBA. F(ab')(2) fragments generated from anti-CMP EBA autoantibodies did not induce disease. Our studies provide the first evidence that EBA autoantibodies to the CMP subdomain of NC1 are pathogenic and induce blister formation. This is the first antigenic epitope on type VII collagen demonstrated to be a pathogenic target for EBA autoantibodies.

Métodos diagnósticos en las enfermedades ampollosas subepidérmicas autoinmunes

There is considerable clinical and histological overlap among the subepidermal autoimmune bullous diseases. The knowledge at the molecular level of the dermo-epidermal junction is essential to understand this group of diseases. The immune-based techniques have contributed to increase the knowledge of these entities and have been progressively incorporated into clinical practice. In this review of the diagnostic methods of subepidermal autoimmune bullous diseases we summarize the most recent advances on the molecular biology of the dermo-epidermal junction, focusing on the immune-based diagnostic techniques. We distinguish two main groups of diagnostic methods: those that detect autoimmune deposits in the skin (direct immunofluorescence and its variants including confocal microscopy) and those that detect antibodies in serum or in other fluids (indirect immunofluorescence and its variants, ELISA, immunoblot and immunoprecipitation). We explain the methodology and diagnostic keys of the techniques most widely applied in our milieu.

Toxic epidermal necrolysis-like acute cutaneous lupus erythematosus and the spectrum of the acute syndrome of apoptotic pan-epidermolysis (ASAP): a case report, concept review and proposal for new classification of lupus erythematosus vesiculobullous skin lesions

The acute clinical syndrome of toxic epidermal necrolysis (TEN) is currently thought to be a distinct clinical-pathological entity typically resulting from drug hypersensitivity. We describe an adult woman who experienced a fulminate pattern of apoptotic epidermal cell injury following tanning bed exposure while taking naproxen that resulted in a clinical presentation having combined features of drug-induced TEN and an infrequently recognized form of bullous cutaneous lupus erythematosus (LE). This case calls attention to the fact that TEN-like injury can occasionally be seen in settings other than drug hypersensitivity (e.g., LE, acute graft versus host disease) and illustrates the need for a unifying concept in this area. We therefore propose the term 'Acute Syndrome of Apoptotic Pan-Epidermolysis (ASAP)' to designate a clinical syndrome that is characterized by life-threatening acute and massive cleavage of the epidermis resulting from hyperacute apoptotic injury of the epidermis. We also review vesiculobullous skin disorders that can be encountered in LE patients and suggest a new classification scheme for such lesions.

Evidence that Anti-Type VII Collagen Antibodies Are Pathogenic and Responsible for the Clinical, Histological, and Immunological Features of Epidermolysis Bullosa Acquisita

Epidermolysis bullosa acquisita (EBA) is an autoimmune blistering disease characterized by autoantibodies to type VII (anchoring fibril) collagen. Therefore, it is a prototypic autoimmune disease defined by a well-known autoantigen and autoantibody. In this study, we injected hairless immune competent mice with purified immunoglobulin G (IgG) fraction of serum from rabbits immunized with the non-collagenous amino-terminal domain (NC1) of human type VII collagen, the domain known to contain immunodominant epitopes. As a control, identical mice were injected with the IgG fraction of serum from non-immunized rabbits. Mice injected with immune IgG developed subepidermal skin blisters and erosions, IgG deposits at the epidermal-dermal junction of their skin, and circulating anti-NC1 antibodies in their serum-all features reminiscent of patients with EBA. Similar concentrations of control IgG purified from normal rabbits did not induce disease in the mice. These findings strongly suggest that autoantibodies that recognize human type VII collagen in EBA are pathogenic. This murine model, with features similar to the clinical, histological, and immunological features of EBA, will be useful for the fine dissection of immunopathogenic mechanisms in EBA and for the development of new therapeutic interventions.

Bullous systemic lupus erythematosus

Blistering eruptions are rare cutaneous manifestations of lupus erythematosus (LE) that may be caused by different mechanisms. Subepidermal clefting with frank vesiculation may occur in early lesions of chronic-, subacute-, and acute-cutaneous LE due to a severe vacuolar alteration of the dermoepidermal junction (DEJ), dermal edema, and lekocytoclastic vasculitis. An exaggerated example of such changes is rarely seen at the advancing edge of the annular plaques of subacute cutaneous LE with erythema-multiforme (EM)-like appearance, a condition formerly described as Rowell's syndrome. In a recently reported novel variant of LE-associated toxic epidermal necrolysis, dysregulated keratinocyte apoptosis has been proposed as an underlying mechanism. These vesiculobullous lesions are considered to be LE-specific. Blistering may also occur in LE in the context of a coexisting immunobullous disease. Pemphigus, bullous pemphigoid (BP), epidermolysis bullosa acquisita (EBA), dermatitis herpetiformis, and linear IgA bullous dermatosis have been all reported in association with LE. Their differentiation relies upon characteristic clinical, histologic, and immunopathologic features (Table 1). These blistering eruptions are rather non-specific for LE.

The lupus band: do the autoantibodies target collagen VII?

BACKGROUND

Circulating autoantibodies directed against basement membrane zone (BMZ) components from patients with bullous pemphigoid and epidermolysis bullosa acquisita have been used to identify their target antigen in the skin and to confirm pathogenicity. Although the pattern of immunofluorescence in those diseases is similar to the lupus band, little is known about the origin and pathogenesis of the lupus band. Identifying the binding sites of the lupus band could provide a clue to the nature of the autoantigen that stimulates autoantibody formation in the skin of patients with systemic lupus erythematosus (SLE) and might provide valuable insight into the factors that influence the localization and pathogenicity of the lupus band.

OBJECTIVES

To investigate the relation between the lupus band and the main BMZ components and to identify the target epitopes of autoantibodies deposited in the skin of patients with SLE.

METHODS

Colocalization of the main components of the skin BMZ in nonlesional SLE skin with the lupus band was investigated using conventional immunofluorescence and confocal laser scanning microscopy. The effect of collagenase and pepsin on the expression of the lupus band was correlated with the differential sensitivity of these proteases on the collagenous and noncollagenous (NC) domains of collagen VII. Reactivity of sera from patients with SLE to a complete recombinant human NC1 domain of type VII collagen was then investigated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Near complete colocalization of the lupus band with collagen VII was found in this study, and chemical degradation of the skin attenuated the expression of the lupus band. Collectively, the NC1 domain of collagen VII was suggested as the target antigen of the lupus band, but none of the sera from patients with SLE reacted with recombinant NC1 domain-coated ELISA plates. Alternative explanations for the results of the colocalization of the lupus band with collagen VII are discussed.

CONCLUSIONS

The lupus band colocalized with collagen type VII. The findings of this study ruled out the NC1 domain of collagen VII as a target antigen for circulating autoantibodies in SLE patients with no clinical evidence of blistering. Further studies are required to determine if other regions of collagen VII or another BMZ component is the target antigen for the immunoglobulins of the lupus band.

Cutaneous lupus erythematosus: diagnosis and management

Cutaneous lupus erythematosus (CLE) includes a variety of lupus erythematosus (LE)-specific skin lesions that are subdivided into three categories - chronic CLE (CCLE), subacute CLE (SCLE) and acute CLE (ACLE) - based on clinical morphology, average duration of skin lesions and routine histopathologic examination. This paper describes our personal experience in the management of CLE over the last 30 years, with details on preferential therapeutic options related to clinical, histologic and immunopathologic aspects of each clinical subset of the disease. Effective sunscreening and sun protection are considered the first rule in the management of CLE because of the high degree of photosensitivity of the disease. Antimalarial agents are crucial in the treatment of CLE and are the first-line systemic agents, particularly in discoid LE (DLE) and SCLE. Dapsone is the drug of choice for bullous systemic LE (BSLE) as well as for LE in small dermal vessels (e.g. leukocytoclastic vasculitis). Retinoids, known as second-line drugs for systemic therapy, are sometimes used to treat chronic forms of CLE and are particularly successful in treating hypertrophic LE. Systemic immunosuppressive agents are required to manage the underlying systemic LE disease activity in patients with ACLE. These drugs, especially azathioprine, methotrexate, cyclophosphamide and cyclosporine, together with corticosteroids, constitute third-line systemic therapy of CLE. In our experience, oral prednisone or parenteral 'pulsed' methylprednisolone are useful in exacerbations of disease activity. Thalidomide provides one of the most useful therapeutic alternatives for chronic refractory DLE, although its distribution is limited to a few countries because of the risk of teratogenicity and polyneuropathy. However, medical treatment with local corticosteroids remains the mainstay of CLE treatment, especially for DLE. Patient education regarding the disease is also important in the management of CLE, because it helps relieve undue anxiety and to recruit the patient as an active participant in the treatment regimen.

Immunofluorescence in dermatology

The accurate diagnosis of bullous and other immune diseases of the skin requires evaluation of clinical, histologic, and immunofluorescence findings. Immunofluorescence testing is invaluable in confirming a diagnosis that is suspected by clinical or histologic examination. This is especially true in subepidermal bullous diseases that often have overlap in the clinical and histologic findings. Direct immunofluorescence is performed on perilesional skin for patients with bullous diseases and lesional skin for patients with connective tissue diseases and vasculitis.

The cutaneous pathology of lupus erythematosus: a review

The presentation of lupus erythematosus (LE) ranges from a skin rash unaccompanied by extracutaneous stigmata to a rapidly progressive lethal multiorgan disease. The diagnosis and subclassification is traditionally based on the correlation of serological and clinical findings. The latter include a photoinduced skin rash, arthralgia, arthritis, fever, Raynaud's phenomenon, anemia, leukopenia, serositis, nephritis and central nervous sysdtem disease. The conventional classification scheme includes systemic, subacute cutaneous and discoid LE. Recent advances in our understanding of the cutaneous histopathology which correlates with the traditional forms of LE, along with certain novel LE subtypes, are the focus of this review. In addition to the main subtypes of LE, we will discuss associated vasculopathic lesions and the contribution of immunofluorescence microscopy to the diagnosis of LE and related connective tissue disease syndromes. Consideration will be given to unusual variants of LE such as anti-Ro/SSA-positive systemic lupus erythematosus (SLE), bullous SLE, lymphomatoid LE, lupus erythematosus profundus, drug induced LE, linear cutaneous LE, chiblains LE and parvovirus B19-associated LE.

Autoantibodies to type VII collagen have heterogeneous subclass and light chain compositions and their complement-activating capacities do not correlate with the inflammatory clinical phenotype

Epidermolysis bullosa acquisita and bullous systemic lupus erythematosus are blistering skin diseases characterized by IgG autoantibodies that predominantly target the noncollagenous domain 1 of type VII collagen, a skin basement membrane component. The basic immunologic events leading to the blistering processes in these diseases remains unclear. We defined the subclass and light chain compositions of the IgG autoantibodies in 15 patients, in order to gain insight into the blistering mechanism. Immunofluorescence correlated the patients' in vivo-bound and circulating antibasement membrane autoantibodies. Four eukaryotic recombinant proteins, including one full-length and three truncated noncollagenous domain 1 proteins generated by sequential deletion of C-terminal amino acids, were used to perform enzyme-linked immunosorbent assay to detect the patients' anti-type VII collagen autoantibodies. The majority of patients' autoantibodies contained both complement-activating and non-complement-activating IgG subclasses. The presence or absence of complement-activating IgG autoantibody subclasses did not correlate with the inflammatory or noninflammatory clinical phenotype. The majority of tested sera contained both kappa and lambda light chain autoantibodies. All sera that reacted to the full-length noncollagenous domain 1 also reacted to the smallest truncated protein containing the cartilage matrix protein and the first three fibronectinlike repeats. The patients' anti-type VII collagen autoantibodies, likely to be polyclonal in nature, may contribute to the pathogenesis of the blistering process by both complement-dependent inflammatory injury and complement-independent mechanical disruption of the anchoring function of type VII collagen. The N-terminal region of the noncollagenous domain 1 may contain an important antigenic epitope targeted by the IgG autoantibodies.

Cicatricial pemphigoid

Cicatricial pemphigoid (CP) is a heterogeneous group of rare, chronic, subepithelial blistering disorders of the mucous membranes and, occasionally, the skin, which can have serious and rarely fatal consequences. The most common clinical features are desquamative gingivitis, oral erosions, and conjunctival fibrosis. Skin lesions occur less frequently and may present as widespread vesicles and bullae, as in bullous pemphigoid (BP). In some patients, the scarring can be a source of significant morbidity because it can result in odynophagia, strictures of the upper aerodigestive tract, or corneal opacities leading to eventual blindness. This article is a comprehensive review and discusses clinical, pathologic, and pathophysiologic aspects of this group of disorders collectively known as CP. (J Am Acad Dermatol 2000;43:571-91.)

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be familiar with the clinical spectrum of CP, the histopathologic and immunopathologic characteristics, the differential diagnosis, the treatment, and the natural history of the disease. Furthermore, this learning activity should facilitate early diagnosis of CP and should promote the idea that the involvement of other specialists, including ophthalmologists, otolaryngologists, gastroenterologists, and oral medicine specialists, as appropriate, will aid in providing these patients with the highest quality of care.

Autoimmune blistering skin diseases

Emergency physicians, at the front line of patient care, are often confronted with a wide variety of dermatologic conditions. Prompt recognition is essential, especially for the autoimmune blistering skin diseases, many of which have considerable morbidity and mortality. Therefore, an accurate diagnosis is imperative for appropriate referral and initiation of therapy. This review article provides a concise yet thorough discussion of the clinical presentation, incidence, differential diagnosis and management of the commonly encountered autoimmune blistering skin diseases, some of which include pemphigus, bullous pemphigoid, and epidermolysis bullosa acquisita.

Bullous systemic lupus erythematosus (type I) in a dog

In human patients with systemic lupus erythematosus, cutaneous subepidermal blistering can occur because of the production of antibodies specific for basement membrane antigens. This condition is referred to as bullous systemic lupus erythematosus (BSLE). A dog was diagnosed with BSLE because it fulfilled the following criteria: (i) a diagnosis of systemic lupus erythematosus by standard methods; (ii) an acquired, vesicular, erosive and ulcerative eruption; (iii) microscopical subepidermal vesicles with neutrophil-predominant inflammation at the dermo-epidermal junction; (iv) deposition of IgG at the epidermal basement membrane zone; and (v) circulating IgG autoantibodies against type VII collagen. Anti-collagen VII type I-BSLE therefore needs to be considered as a possible differential diagnosis for canine autoimmune subepidermal blistering diseases.

Acquired skin disease of hemidesmosomes

The hemidesmosome is a membrane-associated supramolecular dermal epidermal complex linking the cytoskeleton of the basal keratinocyte to structures within the papillary dermis. Different components of this complex have been identified as autoantigens in autoimmune bullous skin diseases. Some of the autoantigens have been characterized at the molecular level. Little is known, however, about the factors that initiate the production of autoantibodies. By histopathology, acquired skin diseases of hemidesmosomes show subepidermal blisters and by direct immunofluorescence, linear deposits of IgG, C3 or IgA at the dermal epidermal junction. Bullous pemphigoid (BP) is the most common acquired disease of hemidesmosomes. Two proteins, BP180 and BP230, have been identified as primary targets of autoantibodies in BP. In addition, pemphigoid/herpes gestationis, lichen planus pemphigoides, cicatricial pemphigoid and linear IgA disease are characterized by an immune response to BP180. Laminin 5 is another well-characterized anchoring filament-lamina densa component of hemidesmosomes. Patients with autoantibodies to laminin 5 show the clinical phenotype of cicatricial pemphigoid. Other acquired skin diseases of the hemidesmosomes reveal autoantibodies to a plectin-like protein, the beta4 subunit of alpha6beta4 integrin, uncein and a not yet characterized 168 kDa protein. Recently, diseases with autoantibodies to 105 and 200 kDa proteins of the lower lamina lucida have been reported. The association of these autoantigens with hemidesmosomes still needs to be demonstrated. Finally, anchoring fibrils associate with the dermal epidermal anchoring complex. The major structural component of anchoring fibrils is type VII collagen, the autoantigen of epidermolysis bullosa acquisita.

Bullous systemic lupus erythematosus: detection of antibodies against noncollagenous domain of type VII collagen

A 9-year-old girl with systemic lupus erythematosus developed bullous eruption. Histopathologic examination showed subepidermal blistering and immunoglobulins (IgG, IgM, IgA) and complement components (C1q, C3) deposited linearly at the basement membrane zone. IgG in this patient's serum bound to the dermal side of 1 mol/L sodium chloride-split normal human skin, and a 290 kd protein was identified in the dermal extract. The patient's serum recognized various epitopes on the noncollagenous domain as demonstrated by the use of fusion proteins of type VII collagen. Resolution of the bullous eruption occurred after treatment with dapsone.

Epitope spreading: lessons from autoimmune skin diseases

Autoimmune diseases are initiated when patients develop aberrant T and/or B cell responses against self proteins. These responses presumably are directed to single immunogenic epitopes on these proteins. Recent data in animal models of autoimmune diseases suggest that the targets of immune responses in autoimmunity do not remain fixed, but can be extended to include other epitopes on the same protein or other proteins in the same tissue, a phenomenon termed "epitope spreading." The "epitope spreading" phenomenon also applies to situations in which tissue damage from a primary inflammatory process causes the release and exposure of a previously "sequestered" antigen, leading to a secondary autoimmune response against the newly released antigen. In experimental autoimmune animal diseases, "epitope spreading" seems to have significant physiologic importance in determining the course and duration of disease. In this paper, we review the current concepts in animal models of autoimmune diseases in order to define the "epitope spreading" phenomenon, and we then propose how this phenomenon might play a significant role in the development and the course of autoimmune skin diseases. Hopefully, an understanding of "epitope spreading" will help the dermatology community to better understand the pathogenesis of autoimmune skin diseases and to rationally fashion disease-specific immune therapy in the future.

Mucocutaneous features of autoimmune blistering diseases

This review will describe adult onset mucocutaneous/autoimmune diseases that involve defects in cell-to-cell, cell-to-matrix, or cell-to-basement membrane adhesion. Included in this group are pemphigus, cicatricial pemphigoid, linear IgA bullous dermatosis, epidermolysis bullosa acquisita, and bullous systemic lupus erythematous. Detection and treatment of blistering disorders that manifest early in the oral cavity may prevent widespread involvement of skin. During the past few years, targets of autoantibodies have been clarified and new targets have been identified, allowing better understanding of the pathophysiology involved in these diseases. New information about more effective regimens with fewer side effects has also been obtained, presenting new treatment options. Clinical manifestations and management of these disorders will be described as well as histopathologic, ultrastructural, and immunopathologic studies that distinguish each disorder and facilitate diagnosis and treatment.

The dermal-epidermal junction

Recent insights into the structure and function of the dermal-epidermal junction have resulted from two converging lines of experimental evidence, namely, the study of inherited blistering disorders of the skin, in which mutations in genes encoding proteins of this region have been discovered, and the targeted ablation of the same genes in knockout mouse models. In addition to these studies, elegant analyses of the cell biology of the hemidesmosome/anchoring filament complex have revealed not only functionally important interactions between structural protein components, but also the role of certain of these proteins in mediating cell adhesion, migration, and signal transduction of messages from the extracellular matrix into the keratinocyte. Our current understanding of the dermal-epidermal junction forms a new model encapsulating the nature both of the hemidesmosomal attachment structures and of the interhemidesmosomal attachments that are mediated by differential cell type specific expression of proteins of the cutaneous adhesion zone.

An extract from cultured human keratinocytes that contains the major autoantigens related to autoimmune bullous skin diseases

Autoantibodies characteristic of autoimmune bullous skin diseases (AIBDs) can be detected by immunoblotting on epidermal, dermal, or bovine muzzle extracts. However, none of those substrates contain all the autoantigens involved in AIBDs, and the diagnosis requires the use of various substrates. Human keratinocytes were cultured under such conditions that they expressed the major autoantigens associated with AIBDs. Forty-two sera with antiepidermal antibodies were immunoblotted on the keratinocyte extract. Bands corresponding to desmoglein III, desmoglein I, BPAg2, BPAg1, and type VII collagen were found in 38 sera. Desmoplakins I and II were revealed by specific monoclonal antibodies. A review of the patients' charts showed a perfect correlation between the blots and the diagnoses of pemphigus vulgaris, pemphigus foliaceus, bullous pemphigoid, cicatricial pemphigoid, and epidermolysis bullosa acquisita. Four sera revealing no band typical of AIBD were from patients with no autoimmune skin disease. Therefore, a single extract of keratinocytes can be used for the differential diagnosis of AIBDs.

Development of an ELISA for rapid detection of anti-type VII collagen autoantibodies in epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is an acquired blistering skin disease characterized by the presence of IgG autoantibodies to type VII collagen. EBA autoantibodies recognize four major immunodominant epitopes localized within the amino-terminal, noncollagenous (NC1) domain. In this study, we developed a rapid, quantitative enzyme-linked immunosorbent assay (ELISA) to detect autoantibody activity against the complete NC1 domain of type VII collagen with the use of an eukaryotic-expressed, recombinant human NC1 antigen. With the ELISA, we tested serum from patients with EBA (n = 24), bullous systemic lupus erythematosus (BSLE) (n = 3), bullous pemphigoid (n = 16), pemphigus (n = 11), and normal controls (n = 12). All EBA and BSLE serum, including four sera that were negative by indirect immunofluorescence, demonstrated reactivity with immobilized NC1 in the ELISA. In contrast, none of the sera from healthy control subjects or patients with unrelated blistering skin diseases reacted with NC1. The EBA sera also reacted with recombinant NC1 by immunoblot analysis but with less sensitivity. Thus, the newly developed ELISA using recombinant NC1 is a sensitive, specific assay and a useful tool for rapidly screening EBA and BSLE serum.

Reactivity of autoantibodies from patients with defined subepidermal bullous diseases against 1 mol/L salt-split skin. Specificity, sensitivity, and practical considerations

BACKGROUND

Circulating IgG anti-basement membrane autoantibodies from patients with subepidermal bullous diseases can be categorized on the basis of their pattern of reactivity against 1 mol/L sodium chloride (NaCl)-split skin.

OBJECTIVE

The purpose of this study was to define by immunochemical techniques the specific antigen(s) targeted by IgG autoantibodies from a group of patients with subepidermal blistering diseases and then (1) prospectively determine which side(s) of 1 mol/L NaCl-split skin is (are) bound by these patients' autoantibodies, (2) compare the sensitivity of intact and 1 mol/L NaCl-split skin for the detection of these autoantibodies; and (3) devise a practical method to distinguish patients with antiepiligrin cicatricial pemphigoid from those with other subepidermal blistering diseases.

METHODS

Investigative techniques included direct and indirect immunofluorescence microscopy, immunoprecipitation studies, and immunoblotting.

RESULTS

These studies identified 14 patients whose sera immunoprecipitate bullous pemphigoid antigens 1, 2, or both. These patients' circulating IgG anti-basement membrane autoantibodies bind the epidermal (n = 11), epidermal and dermal (n = 2), or dermal (n = 1) sides of 1 mol/L NaCl-split skin by indirect immunofluorescence microscopy. In contrast, IgG from all patients with autoantibodies directed against type VII collagen (n = 5) or epiligrin (n = 6) bind only the dermal side of 1 mol/L NaCl-split skin. In all but one patient in this series, 1 mol/L NaCl-split skin proved to be a more sensitive test substrate than intact human skin for detection of circulating IgG anti-basement membrane autoantibodies. Patients with antiepiligrin cicatricial pemphigoid were distinguished from other patients in that their circulating autoantibodies bound epidermal basement membrane in the skin of primates but not small mammals.

CONCLUSION

NaCl-split skin (1 mol/L) of various species is a sensitive and practical indirect immunofluorescence microscopy test substrate for the evaluation of patients with IgG anti-basement membrane autoantibodies and evaluation of subepidermal bullous diseases.

Remission of severe epidermolysis bullosa acquisita induced by extracorporeal photochemotherapy

We report a patient with severe epidermolysis bullosa acquisita (EBA) whose disease was refractory to conventional treatments. New bullae continued to develop over greater than 50% of his body surface area despite therapy. His course was complicated by hyperglycaemia, sepsis, hypoxia caused by pulmonary Aspergillus infection and an idiopathic cardiomyopathy. His EBA resolved after treatment with extracorporeal photochemotherapy (ECP). Hence, ECP may be effective in the treatment of severe EBA which has failed to respond to standard treatment regimens.

Bullous systemic lupus erythematosus: revised criteria for diagnosis

Blistering in systemic lupus erythematosus has been divided into three groups. A specific subgroup of 'bullous systemic lupus erythematosus' has been defined by Gammon et al. on the basis of a number of criteria. From our experience of seven patients with bullous systemic lupus erythematosus, and after reviewing the literature, we suggest that the current classification is too narrow. Our patients displayed clinical and immunohistological (based on direct and indirect immunofluorescence and Western immunoblotting) heterogeneity. Sera from two patients bound to epidermal epitopes in sodium chloride-split skin, but immunoblotting was negative. In neither of these patients could the target antigen be type VII collagen, the only antigen identified as pathogenic in this disease. Patients with epidermal binding should not be excluded from a diagnosis of bullous systemic lupus erythematosus. SLE is a disease in which there is a genetic predisposition to form antibodies to type VII collagen, along with other autoantibodies, many of which may be implicated in blistering. We suggest that the criteria for the diagnosis of BSLE should be revised. We define this disease as an acquired subepidermal blistering disease in a patient with SLE, in which immune reactants are present at the basement membrane zone on either direct or indirect immunofluorescence.

Localized linear bullous eruption of systemic lupus erythematosus in a child

A 9-year-old girl newly diagnosed with systemic lupus erythematosus (SLE) developed a localized linear papulovesicular eruption over the right dorsal hand and ulnar forearm. The skin findings were clinically suggestive of herpes zoster, lichen striatus, or lichen planus-lupus erythematosus overlap. However, histologic, immunofluorescent, immunoelectron microscopic, and immunoblot studies revealed findings compatible with bullous SLE. Our patient is noteworthy because she is the first one reported with bullous SLE presenting in a localized linear pattern. She is also the second-youngest reported patient with bullous SLE.

Immunodominant autoepitopes of type VII collagen are short, paired peptide sequences within the fibronectin type III homology region of the noncollagenous (NC1) domain

Autoantibodies to type VII collagen are associated with the blistering diseases epidermolysis bullosa acquisita and bullous systemic lupus erythematosus. We showed previously that these autoantibodies recognize epitopes within the noncollagenous (NC1) region of type VII collagen. That region is composed of fibronectin type III homology units that may contribute to intermolecular cross-linking and basement membrane adhesion functions of type VII collagen. In this study, we defined the specific amino acid sequences recognized by these autoantibodies. By fusion protein analysis, sera from patients with epidermolysis bullosa acquisita and bullous lupus were found to react with two regions within the fourth (E-1) and eighth (E-2) fibronectin homology repeats, each consisting of approximately 100 amino acids. Affinity purification studies showed E-1 and E-2 to be independent and non-cross-reactive epitope regions. These regions were probed further by enzyme-linked immunosorbent assay analysis of overlapping octapeptide sets derived from the amino acid sequences of E-1 and E-2. The results showed two reactive, closely associated octapeptide sequences within each region, both lying in amphipathic portions of fibronectin type III homology repeats. These studies identify short peptide sequences within the NC1 domain of type VII collagen that are targeted independently by autoantibodies. These sequences may play a direct role in determining the properties of type VII collagen that influence adhesion between this molecule and other basement membrane proteins, and their alteration by antibody binding may be the immunopathogenic event underlying epidermolysis bullosa acquisita and bullous lupus.

Bullous systemic lupus erythematosus with cutaneous mucinosis and leukocytoclastic vasculitis

A 38-year-old man with systemic lupus erythematosus had nodular cutaneous mucinosis, leukocytoclastic vasculitis, and a vesiculobullous eruption. Immunopathologic study of a bullous lesion revealed granular deposits of IgA and IgG along the basement membrane zone. Localization of immune deposits to the lamina and sublamina densa was confirmed by immunoelectron microscopy.

A novel 105-kDa lamina lucida autoantigen: association with bullous pemphigoid

Several cases have been reported of patients with immunemediated subepidermal blistering disorders whose autoantibodies react to antigens present on both the dermal and epidermal side of 1 M NaCl-split skin. In this report, we identify, localize, and characterize the basement membrane zone antigen corresponding to the dermal staining in a patient whose serum stains both the dermal and epidermal side of 1 M NaCl-split skin. This patient's serum contains autoantibodies directed against a 105-kilodalton(kDa) dermal antigen and the 230-kDa epidermal (bullous pemphigoid) antigen. This novel 105-kDa protein was previously identified as the sole antigen in another patient with a unique bullous disease whose autoantibodies were directed against only the dermal side of 1 M NaCl-split skin. This 105-kDa antigen was identical by one- and two-dimensional immunoblot analysis in these two patients. By immunoblot analysis, autoantibodies from our patient labeled a 105-kDa protein within various extracts of human skin basement membrane. Immunoblot analyses using epitope-selected autoantibodies directed against the 105-kDa protein demonstrated that this antigen is independent and distinct from other known basement membrane antigens. The 105-kDa antigen is an extracellular matrix component of the basement membrane, which is synthesized and secreted by both keratinocytes and fibroblasts. Identical electrophoretic migration of cellular and secreted forms of the protein suggested there is no major post-translational modification of the protein. Immunomapping of normal human skin fractured through the dermal-epidermal junction by incubation in 1 M NaCl or by suction blistering demonstrated that the location of the 105-kDa antigen within the basement membrane zone is between the bullous pemphigoid antigens and two other lamina lucida components, laminin and nicein. These data demonstrate clearly that a subepidermal autoimmune bullous disease may have autoantibodies directed against two distinct components of the dermal-epidermal junction.