Bullous pemphigoid and cicatricial pemphigoid: immunoblotting detection of involved autoantigens

Humoral Epitope Spreading in Autoimmune Bullous Diseases

Autoimmune blistering diseases are characterized by autoantibodies against structural adhesion proteins of the skin and mucous membranes. Extensive characterization of their autoantibody targets has improved understanding of pathogenesis and laid the basis for the study of antigens/epitopes diversification, a process termed epitope spreading (ES). In this review, we have reported and discussed ES phenomena in autoimmune bullous diseases and underlined their functional role in disease pathogenesis. A functional ES has been proposed: (1) in bullous pemphigoid patients and correlates with the initial phase of the disease, (2) in pemphigus vulgaris patients with mucosal involvement during the clinical transition to a mucocutaneous form, (3) in endemic pemphigus foliaceus, underlining its role in disease pathogenesis, and (4) in numerous cases of disease transition associated with an intermolecular diversification of immune response. All these findings could give useful information to better understand autoimmune disease pathogenesis and to design antigen/epitope specific therapeutic approaches.

Anti-BP180-type mucous membrane pemphigoid immunoglobulin G shows heterogeneity of internalization of BP180/collagen XVII into keratinocyte cytoplasm

Anti-BP180-type mucous membrane pemphigoid (BP180-MMP) is a rare autoimmune subepidermal blistering disease that targets the C terminus of BP180/collagen XVII. Currently, the pathomechanism of BP180-MMP is not well understood. We reported previously that immunoglobulin G (IgG) from patients with bullous pemphigoid (BP) can induce internalization of BP180 via a macropinocytic pathway, which depletes BP180 and weakens epidermal cell-matrix integrity. The purpose of the present study was to elucidate the pathomechanism of BP180-MMP. Immunohistochemistry of biopsy specimens from two patients with BP180-MMP revealed that one patient had BP180 internalization, but the other did not. In live-cell imaging using IgG from patients with BP180-MMP on several keratinocyte cell lines, IgG from only three out of the seven patients was associated with BP180 internalization into the cytoplasm. Our results suggest that IgG from patients with BP180-MMP shows heterogeneity of internalization of BP180. This variability in BP180 internalization in patients with BP or BP180-MMP may lead to differences in clinical presentation.

Treatment strategies in mucous membrane pemphigoid

Mucous membrane pemphigoid (MMP) is an autoimmune blistering disorder that is characterized by subepithelial bullae. Various basement membrane zone components have been identified as targets of autoantibodies in MMP. Considerable variability exists in the clinical presentation of MMP. Mucous membranes that may be involved include the oral cavity, conjunctiva, nasopharynx, larynx, esophagus, genitourinary tract, and anus. A multidisciplinary approach is essential in the management of MMP. Early recognition of this disorder and treatment may decrease disease-related complications. The choice of agents for treatment of MMP is based upon the sites of involvement, clinical severity, and disease progression. For more severe disease, or with rapid progression, systemic corticosteroids are the agents of choice for initial treatment, combined with steroid-sparing agents for long-term maintenance. Due to the rarity of this disease, large controlled studies comparing the efficacy of various agents are lacking.

Bullous diseases in the elderly

The elderly are prone to several autoimmune bullous diseases that have significant morbidity, and an accurate diagnosis is essential for proper management. It is important to be aware of the potential adverse effects of the various systemic agents that can be used.

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.

Contemporary issues in the diagnosis of oral pemphigoid: a selective review of the literature

Pemphigoid is a group of bullous diseases that have a diversified morphologic presentation and affect the skin, oral mucosa, and other mucosal membranes, alone or in combination. In the literature, the condition has been subclassified into bullous pemphigoid and cicatricial pemphigoid (mucous membrane pemphigoid) on the basis of the primary organ of involvement. In addition to the clinical presentation and a subepithelial vesicle or bullae on routine histologic analysis, the diagnosis is based on direct and indirect immunofluorescence studies. Recent investigations indicate that different clinical groups of patients with pemphigoid produce autoantibodies to different molecules within the basement membrane zone. Based on these recent observations and a review of the literature, a viewpoint is presented that not all patients with cicatricial pemphigoid should be grouped together. Rather, they should be classified into subgroups-ocular, oral, etc-on the basis of the clinical phenotype and long-term follow-up. Such a division will facilitate the provision of appropriate and relevant treatment plans; if the clinical course changes, the diagnosis can be adjusted. This strategy will prevent patients with disease limited to the oral cavity from receiving systemic drugs or agents that may be more harmful than beneficial.

Characterization of the antibody response in oesophageal cicatricial pemphigoid

Cicatricial pemphigoid (CP) is a subepidermal, autoimmune bullous dermatosis. It is classified as a clinical subset of bullous pemphigoid (BP). However, it differs from BP in some significant ways: (i) in CP mucosal involvement with clinical scarring is prominent; (ii) there is a prominent IgA class antibody response alone or in addition to the IgG class antibody response; and (iii) there is a heterogeneous antibody response in CP, whereas in BP the majority of the antibodies are directed against a 180-kDa hemidesmosomal protein, bullous pemphigoid antigen 2 (BPAg2). Oesophageal involvement in CP is a rare, but often devastating manifestation. In this study we examined the humoral autoimmune response in oesophageal CP, in an attempt to characterize the autoantibody reactivity profile. We used direct and indirect immunofluorescence and Western immunoblotting using normal human skin and oesophagus substrates. We studied patient sera over time in order to search for evidence of epitope spreading in these patients. All patients had positive direct immunofluorescence of perilesional oesophageal epithelium. All patients had positive circulating antibasement membrane zone autoantibody titres. There was a significant IgA class in addition to an IgG class autoantibody response. IgA and IgG antibodies demonstrated significant reactivity with BPAg2 and the 97 kDa linear IgA disease antigen on Western immunoblot suggesting intraprotein epitope spreading. There was no evidence of interprotein epitope spreading over time. Our findings suggest that there is a heterogeneous antibody response in oesophageal CP with the predominant antigen being BPAg2.

Cicatricial pemphigoid: serial titres of circulating IgG and IgA antibasement membrane antibodies correlate with disease activity

We have recently shown in a cohort of patients (n = 67) with mucous membrane pemphigoid, 63 of whom had cicatricial pemphigoid (CP), that the presence of both IgG and IgA circulating antibasement membrane zone antibodies was associated with a more severe and persistent disease. In this study we sought to ascertain whether in CP, serial titres of IgG and IgA might provide a reliable marker of disease activity. Serum titres for IgG and IgA antibodies were assayed at 6- to 12-monthly intervals in 56 patients over 32.2 +/- 20.3 (mean +/- SD) months. Antibody titres were correlated with the clinical score recorded at each follow-up visit. Sequential titres for both IgG (P < 0.001) and IgA (P = 0.015) were significantly associated with variations in disease activity. Greatest improvement was seen in patients with the greatest change in either IgG or IgA antibody titre. We suggest that serial antibody titres may therefore be useful in the assessment and management of CP.

Significantly increased occurrence of HLA-DQB1*0301 allele in patients with ocular cicatricial pemphigoid

To determine the immunogenetic characteristics of patients with immune-mediated subepithelial blistering diseases of mucous membranes, we performed HLA-typing for the class II MHC gene DQB1*0301 allele using a direct method. Genomic DNA extracted from Caucasian patients was amplified by polymerase chain reaction using primer pairs specific for the DQB loci followed by Southern blotting with a peroxidase-conjugated sequence-specific oligonucleotide probe. Seventy-six percent (16/21) of patients with ocular mucosal disease (with or without oral mucosal and skin diseases) carried the DQB1*0301 allele; by contrast, only 33% (14/42) of race-, age-, and geography-matched normal individuals carried the DQB1*0301 allele (p < 0.005). The relative risk for ocular disease if DQB1*0301 allele is present is 6.4, similar to the relative risk of 8 for patients with ocular but no oral disease (pure ocular cicatricial pemphigoid, p < 0.025). In patients with oral mucosal disease (with or without ocular mucosal and skin diseases), 68% (15/22) carried the DQB1*0301 allele (p < 0.025). When patients with ocular disease were excluded, however, the increased occurrence of the DQB1*0301 allele in patients with oral disease was not statistically significant (64%, 7/11, p < 0.25). In patients with subepidermal blistering skin disease but no oral or ocular disease, there was no increase in the occurrence of the DQB1*0301 allele (38%, 5/13, p > 0.5). The significantly increased occurrence of the DQB1*0301 allele in patients with ocular mucosal disease may point to a distinct immunogenetic factor that predisposes patients to develop an ocular scarring process.

Identification of a 168-kDa mucosal antigen in a subset of patients with cicatricial pemphigoid

This study describes the presence of antibodies in sera from patients with cicatricial pemphigoid specific for a 168-kDa antigen expressed by buccal mucosa. Six cicatricial pemphigoid sera unreactive, with epidermal or dermal proteins in immunoblot assay were tested on mucosal protein extracts. Four of these sera labeled a mucosal 168-kDa antigen (M168) under reducing conditions. An additional cicatricial pemphigoid serum with circulating antibodies to 180-kDa bullous pemphigoid antigen (BPAg2) also labeled M168. None of these cicatricial pemphigoid sera reacted with the alpha, beta, or gamma subunits of laminin-5. Nitrocellulose elution studies showed that the M168 antigen is a basement membrane antigen and labeled the epidermal side of salt-split skin. Immunoaffinity-purified anti-M168 antibodies did not bind to the 230-kDa bullous pemphigoid antigen (BPAg1) or to the 180-kDa BPAg2. None of the control sera from healthy individuals or from bullous pemphigoid, pemphigus vulgaris, or pemphigus foliaceus patients reacted with Ml68. This study demonstrates the specificity of some cicatricial pemphigoid sera against a 168-kDa antigen that is different from the laminin-5 subunits and shares no epitopes with the antigens of bullous pemphigoid (BPAg1, BPAg2) or the epidermolysis bullosa acquisita.

Cicatricial pemphigoid autoantibodies react with multiple sites on the BP180 extracellular domain

Cicatricial pemphigoid (CP) is an autoimmune blistering disease that primarily affects mucosal tissues. Autoantibodies to laminin-5 have previously been detected in certain patients with a CP-like disease; however, individuals that exhibit this reactivity profile apparently represent a small subset of CP patients. In the present investigation, 0 of 18 CP sera showed reactivity with laminin-5 by immunoblotting. In contrast, 18 of 23 CP sera (78%) recognized a 180-kDa epidermal antigen that, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, co-migrated with BP180, a hemidesmosomal glycoprotein associated with two other autoimmune blistering diseases, bullous pemphigoid and herpes gestationis. To investigate further the CP autoimmune response, various segments of human BP180 were expressed as bacterial fusion proteins and assayed by immunoblotting for reactivity with CP patients' sera. The results of this investigation demonstrated that the BP180 autoantigen is indeed a major target of CP autoantibodies. Further, two distinct CP-reactive sites were identified on the extracellular domain of the BP180 protein, one located in the non-collagenous (NC) 16A domain (at or near the previously defined autoantibody-reactive site recognized by bullous pemphigoid and herpes gestationis sera) and the other in the carboxy-terminal region of this protein. Sixteen of 23 CP sera (70%) reacted with one or both of these antigenic sites of BP180. Other immunologic data suggested that BP180 may harbor additional CP-reactive sites. In conclusion, there are now three bullous diseases, bullous pemphigoid, herpes gestationis, and cicatricial pemphigoid, that are known to be associated with an autoimmune response against the extracellular domain of the BP180 antigen.

Major antigenic epitopes of bullous pemphigoid 230 kDa antigen map within the C-terminal end of the protein. Evidence using a 55 kDa recombinant protein

In order to obtain greater insight into the nature of B-cell epitopes in bullous pemphigoid (BP), we generated a BP recombinant protein of 55 kDa M(r) (rBP 55) from a cDNA sequence encoding for the carboxyterminal region of the 230 kDa BP antigen. Serum IgG from guinea-pigs immunized with rBP 55 stained the basement membrane zone of normal human skin and immunoprecipitated the rBP 55 protein, and also the 230 kDa BP antigen recovered from extracts of cultured keratinocytes, thus confirming that the rBP 55 amino acid sequence is present in native BP antigen. The reactivity of sera from 60 patients with BP was analysed using an immunoblot assay on epidermal protein extracts and on the rBP 55 protein. Forty of the 60 BP sera (66%) contained autoantibodies to the 230 kDa polypeptide in an epidermal extract, and 37 of these 40 sera (92%) recognized the rBP 55 protein. In contrast, no reactivity against rBP 55 was detected with 20 BP sera devoid of autoantibodies against the 230 kDa antigen. Likewise, sera from patients with autoimmune blistering skin disorders other than BP (epidermolysis bullosa acquisita or pemphigus vulgaris), and control sera, were unreactive to rBP 55. These results clearly demonstrate the immunogenicity and antigenicity of the C-terminal end of the 230 kDa BP antigen. They confirm that this 555 amino acid segment, corresponding to rBP 55, contains major epitopes which can bind BP patients' autoantibodies, and suggest that the rBP 55 protein could be useful for further characterization of these B-cell epitopes.

Identification and partial characterization of a novel 105-kDalton lower lamina lucida autoantigen associated with a novel immune-mediated subepidermal blistering disease

Certain skin basement membrane components, such as bullous pemphigoid antigens and epidermolysis bullosa acquisita antigen, were discovered as a result of an autoimmune reaction. In this report, we describe a unique lamina lucida determinant associated with a novel immune-mediated subepidermal bullous dermatosis. This unique bullous dermatosis resembled severe toxic epidermal necrolysis clinically. The histologic findings resemble dermatitis herpetiformis. Direct immunofluorescence microscopy detected linear immunoglobulin G (IgG) and C3 deposition at the cutaneous basement membrane zone of lesional and perilesional skin. Direct and indirect immunoelectron microscopy localized the IgG deposits to the lowest portion of the lamina lucida. The patient's autoantibodies, belonging to the IgG1 subclass, labeled basement membrane zone of normal intact human skin, oral mucosa, and conjunctiva, and localized to the dermal side of salt-split normal adult and neonatal human skin, but failed to react with human fetal skin up to 142 gestational days. The patient's autoantibodies failed to react with bullous pemphigoid antigens or epidermolysis bullosa acquisita antigen (type VII collagen) by immunoblotting. Instead, the patient's autoantibodies unequivocally labeled a 105-kilodalton (kD) protein in cellular extracts and conditioned media of human cultured keratinocytes and dermal fibroblasts. The titer of the patient's antibody against the cutaneous basement membrane zone and the intensity of the antibody reactivity against the 105-kD protein paralleled the patient's disease activity. Thus, this 105-kD lower lamina lucida protein represents a novel autoantigen and this patient's disease represents a novel autoantigen and this patient's disease represents a deep lamina lucida pemphigoid, distinguishable from all other known autoimmune bullous dermatoses.

Epidermolysis bullosa acquisita in a 3 1/2-year-old girl

A 3 1/2-year-old girl had a subepidermal bullous eruption with immunopathologic features that were consistent with epidermolysis bullosa acquisita or bullous systemic lupus erythematosus. This report highlights the difficulty encountered in distinguishing between epidermolysis bullosa acquisita and other bullous disorders that involve the dermoepidermal junction and the need for modern immunologic investigations in the diagnosis of bullous diseases in children.

The distribution of alpha 6 beta 4 integrins in lesional and non-lesional skin in bullous pemphigoid

The alpha 6 beta 4 integrin is associated ultrastructurally with the hemidesmosomes of the basal keratinocytes and with the bullous pemphigoid antigen (BPA), suggesting an important role in adhesion of epidermal cells to the basement membrane. Using an immunofluorescence technique with chain-specific monoclonal antibodies to the alpha and beta subunits we have investigated the distribution of the alpha 6 beta 4 integrin in normal skin (n = 3) and in BP skin (uninvolved, perilesional and lesional) [n = 11]). The findings have been compared with other types of subepidermal blisters and with normal skin split by chemical means (n = 2) and by suction (n = 2). The distribution of alpha 6 beta 4 integrin was compared with that of bullous pemphigoid antigen (BPA) and with other basement membrane zone (BMZ) macromolecules, laminin, collagen type IV, collagen type VII and the BM600 antigen. In uninvolved, perilesional and early pre-blistered lesional BP skin the distribution of both the alpha 6 and beta 4 integrin subunits, BPA laminin, collagen types IV and VII and the BM600 antigen was identical to normal skin, i.e. a linear band in the BMZ. Within BP blisters, both alpha 6 and beta 4 integrin subunits and BPA were absent, except in two blisters in which the integrin expression was retained in the blister roof, despite loss of BPA. The other BMZ components were expressed on the blister floor.(ABSTRACT TRUNCATED AT 250 WORDS)

The major cicatricial pemphigoid antigen is a 180-kD protein that shows immunologic cross-reactivities with the bullous pemphigoid antigen

Recent studies have shown that sera from patients with cicatricial pemphigoid (CP) contained autoantibodies against epidermal antigens of molecular weight 230 kD and/or 180 kD by immunoblotting, similar to those recognized by bullous pemphigoid (BP) sera. Previous immunoprecipitation studies have shown that BP sera only precipitated the 230-kD antigen. To characterize the CP antigen(s) we tested 10 CP sera, 10 BP sera, and four controls by both immunoprecipitation of radiolabeled cells and immunoblotting of epidermal extracts. For immunoprecipitation, we used 0.5% NP-40 extracts of both normal human keratinocytes and Pam cells. All CP sera precipitated a 180-kD protein that co-migrated with the BP180 antigen precipitated by some individual BP sera. Two of these CP sera also faintly bound a 230-kD protein of similar molecular weight as the major BP230 antigen. CP and BP sera with an immunoblotting pattern of 180 kD immunoprecipitated a co-migrating 180-kD protein. CP sera reacting by immunoblotting with the 230-kD antigen precipitated the 180-kD and/or the 230-kD antigen. In contrast, BP sera reacting with the 230-kD antigen only precipitated this antigen. In further experiments, labeled 0.5% NP-40 extracts from Pam cells were first preabsorbed with a reference BP serum and then immunoprecipitated with CP sera. Under these conditions, CP sera that immunoprecipitated both 180-kD and 230-kD proteins with the standard procedure no longer precipitated these proteins. Our results suggest that a 180-kD protein is the major CP target-antigen that demonstrated immunologic cross-reactivities with the BP180 and the BP230 antigens.

Serological diagnosis of bullous pemphigoid (BP): comparison of the sensitivity of indirect immunofluorescence on salt-split skin to immunoblotting

Specialized immunological assays are required for the accurate diagnosis of bullous dermatoses such as bullous pemphigoid (BP), epidermolysis bullosa acquisita and bullous lupus erythematosus. The aim of this study was to analyse and compare the sensitivity of indirect immunofluorescence (IF) on salt-split skin and immunoblotting for the detection of circulating autoantibodies in BP. Of the BP patients selected for the study, 74/79 (94%) had circulating autoantibodies detected by at least one of the two methods. Both methods had comparable sensitivity and detected BP-specific autoantibodies in 82-85% of the patients. Because 20% of the patients were found to be positive by only one of the methods, both methods should be used in the diagnosis of BP. Indirect IF on salt-split skin is easier to perform and is preferable in routine analysis, but Western blotting may be used as a complementary assay with sera showing no reactivity on salt-split skin.

Structure and antigenicity of the skin basement membrane zone

The skin basement membrane zone is comprised of two major ultrastructural regions, four associated structures, and at least 17 different antigens. In this brief review, the ultrastructure, antigenicity, and ontogeny of normal human skin will be discussed in detail, as will alterations in expression or immune response to selected basement membrane components in specific mechanobullous and autoimmune diseases.

The clinical expression of bullous pemphigoid is not determined by the specificity of the target antigen

The major bullous pemphigoid (BP) antigen is a 220-240-kDa polypeptide, although some BP sera recognize bands of 180-200 kDa or lower molecular weight. We have investigated to what extent this heterogeneity of the target antigen accounts for the clinical diversity of BP. Immunoblotting studies against extracts of salt-separated epidermis were performed on sera from 39 patients with BP. The blotting patters obtained were correlated with the clinical findings, with particular reference to prodromal itching, lesion morphology and severity, mucosal involvement, presence of milia, dapsone responsiveness and disease duration. The results confirm that the major BP antigen is a 220-kDa polypeptide, and that the 180-kDa polypeptide is a second and sometimes the sole BP antigen identified in immunoblots. Rarely, multiple bands of lower molecular weight were found. There was no correlation between the pattern of BP antigens detected in immunoblots and the clinical presentation and course of BP. There was considerable clinical diversity even among the nine patients showing specificity for a single 220-kDa target antigen. Although two patients with a single 180-kDa antigen specificity had a disease of unusually long duration, factors other than antigen specificity must determine the clinical expression of BP.

Cicatricial pemphigoid antigen differs from bullous pemphigoid antigen by its exclusive extracellular localization: a study by indirect immunoelectronmicroscopy

Several components of the dermal-epidermal junction (DEJ) bear the name of the autoimmune bullous disease in which they are involved. The epidermolysis bullosa acquisita (EBA) antigen, a component of anchoring fibrils, and the bullous pemphigoid (BP) antigen, a component of hemidesmosomes (HD) with a molecular weight of 220-240 kD, have been well characterized. In contrast, there is little data known about the cicatricial pemphigoid (CP) antigen. No differences between CP and BP have been reported when sera of patients were studied by Western immunoblotting. Findings of a study of sera from 8 patients with CP by indirect immunoelectron microscopy (IEM) on normal human skin are reported. Saponin (0.1% 10 mn) was used as a permeabilizing agent of cytomembranes and saponin-treated skin samples were compared to saponin-untreated skin samples. Four sera from patients with BP, one from a patient with EBA, and three from healthy donors served as controls. The CP sera produced a similar staining of DEJ on both saponin-treated and saponin-untreated skin samples: immune deposits were localized over the lamina densa and the lower part of the lamina lucida clearly separated from the cytoplasmic membrane of keratinocytes, in regularly spaced clumps. The BP sera produced an intense staining of DEJ only on saponin-treated skin samples: immune deposits were observed on the cytoplasmic attachment plaque of the HD; on saponin-untreated skin samples, BP sera produced only a faint staining of the extracellular part of HD. Finally, as expected the EBA serum appeared on the lower part of the lamina densa and anchoring fibrils, and no DAB deposits were observed with the serum of healthy donors. This data indicated that CP antigen is different than BP antigen by its exclusive extracellular localization. It may be a component of anchoring filaments.

Salt-split human skin substrate for the immunofluorescent screening of serum from patients with cicatricial pemphigoid and a new method of immunoprecipitation with IgA antibodies

In patients with cicatricial pemphigoid, immunoglobulins (usually IgG) and complement are deposited within the dermoepidermal junction and are detected by direct immunofluorescent staining of perilesional mucous membrane and/or skin with fluorescein-labeled antibodies to human immunoglobulins. Although rare, some patients also have circulating low-titer, anti-basement membrane zone autoantibodies. In this study, we report 11 patients with the clinical, histologic, and immunologic criteria for cicatricial pemphigoid who had circulating anti-BMZ autoantibodies as demonstrated by positive indirect staining of a normal human skin that had been fractured through the dermoepidermal junction by prolonged incubation in a cold, 1 mol/L sodium chloride solution. On this salt-split human skin substrate, 9 of the 11 patients (82%) had autoantibodies that bound to the epidermal roof, one serum stained only the dermal floor, and one serum stained both sides of the separation. The predominant class of immunoglobulin in the patients' sera that bound to the substrate was IgA; IgA was the single immunoglobulin in 55% and was associated with IgG in 18%. IgG was the only immunoglobulin detected in 27% of the cases. No specific protein was detected by either Western immunoblot or a new IgA immunoprecipitation procedure.

Immunodermatology update: the immunologically mediated vesiculobullous diseases

Before a specific diagnosis of an immunologically mediated blistering disease can be made, the clinical and histologic features and the results of direct and indirect immunofluorescence studies (with use of multiple substrates in some cases) must be assessed. For both subepidermal and intraepidermal groups of blistering diseases, direct immunofluorescence testing of perilesional tissue is critical for diagnosis. For these conditions, indirect immunofluorescence testing of serum is important for diagnosis and has a role in management of selected diseases. In dermatitis herpetiformis, indirect testing of serum for IgA antiendomysial antibodies is useful for both diagnosis and management. Indirect testing of serum for IgG antibodies to intercellular substance is important for diagnosis and, in conjunction with the clinical findings, can be used as a guide for monitoring disease activity in patients with pemphigus. Immunoelectron microscopy, immunoprecipitation, and immunoblotting studies have identified the sites of immune deposits and the specific antigens in most of the immunologically mediated bullous diseases. From a practical standpoint, however, direct and indirect immunofluorescence testing, in conjunction with clinical and histologic evaluations, is a simple, rapid, and relatively inexpensive tool for diagnosis and management.

The hemidesmosomal plaque. I. Characterization of a major constituent protein as a differentiation marker for certain forms of epithelia

To examine whether constituent proteins of hemidesmosomal structures can be used as markers for certain pathways of epithelial differentiation we have examined the occurrence of the major M- approximately 230,000 plaque protein, the "bullous pemphigoid" (BP) antigen. Several bovine, rat and human tissues and bovine cell culture lines were examined, using different human autoantibody preparations in immunocytochemistry and immunoblotting. We report that this protein, also unequivocally identified by cDNA cloning from expression libraries and DNA sequencing, occurs not only in different stratified epithelia but also, apparently always in hemidesmosomal structures, in urothelium of bladder and the complex epithelia of trachea, bronchus and several glands, notably myoepithelium-containing skin glands, the mammary gland and salivary glands. The protein is absent, however, in all single-layered epithelia and in several tissues reported to have subplasmalemmal densities structurally similar to hemidesmosomes, such as Purkinje fibers of heart, meninges and perineuria. A mammary-gland-derived epithelial cell line (BMGE + H) is particularly rich in hemidesmosomes. This has been used to study the endocytotic uptake of hemidesmosome-containing plasma membrane domains into cytoplasmic vesicles upon detachment of cell sheets during treatment with dispase, a proteolytic enzyme. We propose to use the Mr- approximately 230,000 plaque protein as a marker selective for certain subsets of epithelial cell types and epithelium-derived tumors in studies of fetal and tumor development, including differentiation diagnosis of carcinomas.

Studies of cicatricial pemphigoid autoantibodies using direct immunoelectron microscopy and immunoblot analysis

We studied 11 consecutive patients with classical cicatricial pemphigoid (CP) using direct immunoelectron microscopy (IEM) and Western immunoblotting analysis. Direct IEM performed in the skin or gingival mucosa revealed in all 11 CP patients that immunoglobulins and complement deposits were usually thick and discontinuous along the dermoepidermal junction, mostly localized on the lamina densa and occasionally in the lamina lucida. By direct IEM, the ultrastructural aspect in CP differs from the pattern observed in bullous pemphigoid (BP) and from that of chronic epidermolysis bullosa acquisita (EBA). Nine CP patients were studied by Western immunoblotting and, of these nine, only two had detectable anti-basement membrane zone (BMZ) antibodies by indirect immunofluorescence on salt-split skin. By immunoblotting performed on protein extracts of heat-separated epidermis, eight out of the nine CP sera specifically reacted with two protein bands of approximately 230-240 kD and 180 kD, similar to those recognized by BP sera in co-migration experiments. By immunoblotting on skin BMZ extracts, none of these nine CP sera recognized the 290-kD major polypeptide of EBA antigen. Taken together, these results suggest that, in CP, the target-antigen, as identified on immunoblots, is similar to BP antigen, but with an abnormal expression within the dermoepidermal junction of patients, which may in part explain the scarring course of the disease.

The localization of the bullous pemphigoid and cicatricial pemphigoid antigens: direct and indirect immunofluorescence of suction blisters

The location of in vivo bound immunoreactants was studied in 37 patients with subepidermal blistering diseases by direct immunofluorescence (IMF) on suction blisters taken from uninvolved forearm skin. The patients studied included 18 with bullous pemphigoid (BP), nine with cicatricial pemphigoid (CP), three with acquired epidermolysis bullosa (EBA) and 7 hybrid cases. The patterns of IMF in the suction blisters were: BP, epidermal 1, dermal 1, combined 4, negative 12; CP, epidermal 1, dermal 2, negative 6; EBA, dermal 2, negative 1; and 'hybrid' patients, epidermal 3, negative 4. The different patterns of suction blister staining could not be correlated with the clinical features of the patients in respect of mucous membrane involvement, scars or milia or a history of skin fragility. Both BP and CP are probably heterogeneous in respect of their antigen specificity, and the two diseases cannot reliably be distinguished by the patterns of direct IMF on suction blisters. In addition, some individual patients with BP have more than one target antigen as indicated by a combined pattern of suction blister fluorescence. The lack of correlation between the pattern of suction blister fluorescence and the clinical features suggests that factors other than antigen specificity determine the clinical expression of subepidermal blistering diseases.

Comparative expression of bullous pemphigoid antigens in normal human epidermis and cultured keratinocytes

A heterogeneity of the bullous pemphigoid (BP) antigen initially described as a 220- to 240-kDa polypeptide doublet expressed in normal human skin was recently demonstrated. The aim of our study was to compare the heterogeneity of BP antigen by the immunoblotting technique in extracts of both human epidermis and keratinocyte cultures. Extracts of epidermal tissues obtained from plastic surgery skin samples and secondary keratinocyte cultures were analyzed for their immunologic content defined by 30 BP sera. Twenty-six out of 30 tested sera showed similar binding reactivities with one or several polypeptide bands in both extracts. These sera defined seven antigens of molecular weights ranging from 240 to 97 kDa. Three groups of sera reacting with three, two, or only one antigen could be distinguished in which 180, 200, and 220 kDa polypeptides represented the major BP antigens both in vivo and in vitro. The binding reactivity of most immunofluorescent negative sera demonstrated the sensitivity of the immunoblotting technique to evidence the heterogeneity of BP antigens and antibodies. Keratinocyte cultures represent a reproducible substrate for such analysis and offer a standardization attempt in comparative investigations in BP.