Analysis of antigens targeted by circulating IgG and IgA autoantibodies in 50 patients with cicatricial pemphigoid

Scarring autoimmune bullous disease in a Ugandan patient with autoantibodies to BP180, BP230, and laminin 5

We report on a 24-year-old, male Ugandan patient with a 2-week history of itchy papules, vesicles, erosions, and crusts distributed on the entire body, accompanied by minor erosions on the palate, tongue, and lower lip. Conjunctivae and genital mucosa were not involved. Circulating IgG and IgA autoantibodies were found against recombinant full-length BP180, BP180 4575, and the C-terminus of BP230. In addition, IgG reactivity was observed against the 16th noncollagenous region of the BP180 ectodomain, the cell-derived soluble ectodomain of BP180 (linear IgA disease antigen 1), and the alpha3 and gamma2 chains of laminin 5. No reactivity was detected with type VII collagen, alpha6beta4 integrin, and the p200 protein. Oral prednisolone and dapsone led to clearance of lesions that mostly healed with scarring and milia formation. Here, we describe a scarring mucocutaneous variant of an autoimmune blistering skin disorder that extends the current clinical and immunopathologic spectrum of this group of diseases.

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.

Collagen XVII/BP180: a collagenous transmembrane protein and component of the dermoepidermal anchoring complex

Collagen XVII, or BP180, is a collagenous transmembrane protein and a structural component of the dermoepidermal anchoring complex. Molecular studies reveal that it has a globular cytosolic amino-terminal domain and flexible-rod extracellular carboxyterminal domain. The extracellular portion of collagen XVII is constitutively shed from the cell surface by ADAMs (proteinases that contain adhesive and metalloprotease domains). Cell biological analyses suggest that collagen XVII functions as a cell-matrix adhesion molecule through stabilization of the hemidesmosome complex. This concept is supported by investigations into human diseases of the dermoepidermal junction, in which collagen XVII is either genetically defective or absent (as in some forms of nonlethal junctional epidermolysis bullosa). Autoantibodies against collagen XVII (BP180) are seen in bullous pemphigoid, pemphigoid gestationis, mucous membrane pemphigoid, linear IgA disease, lichen planus pemphigoides and pemphigoid nodularis. In vivo and in vitro studies provide evidence for a pathogenic role of these autoantibodies, and suggest that the serum level and epitope specificity of these antibodies influences disease severity and phenotype. This review summarizes the structural and biological features of collagen XVII and its role in diseases of the basement membrane zone.

[Mucous membrane pemphigoid: IgG and IgA antibodies against the BP180 antigen]

INTRODUCTION

Mucous membrane pemphigoid is a group of autoimmune bullous diseases, mediated by autoantibodies directed against different proteins in the dermoepidermal junction, including the BP180 antigen.

PATIENTS, MATERIAL AND METHODS

We included five patients with MMP in this study. We studied the presence of circulating autoantibodies against the BP180 antigen and against recombinant extracellular fragments of this protein.

RESULTS

We detected the presence of circulating antibodies against BP180 in all of the patients. Indirect immunofluorescence (IIF) studies were positive in 2 patients (20 %), as well as in 2 patients via salt-split studies. We found reactivity to the extracellular fragment of BP180 (LAD-1) in 3 patients, 2 of them via IgA and 1 with IgG. The serum of only 2 patients recognized the NC16A fragment, and 4 of the 5 patients had antibodies against the carboxy-terminal domain BP180 4575.

CONCLUSIONS

Molecular biology techniques are very important to complement the diagnosis of MMP, especially when the results of hematoxylin-eosin or IF studies are not satisfactory for a diagnosis of MMP.

Detection of laminin 5-specific auto-antibodies in mucous membrane and bullous pemphigoid sera by ELISA

Mucous membrane pemphigoid (MMP) is an autoimmune bullous disease that primarily affects mucous membranes leading to a scarring phenotype. MMP patients produce auto-antibodies (auto-ab) that preferentially recognize two components of the dermoepidermal basement membrane zone (BMZ): bullous pemphigoid (BP)180 and laminin 5 (LN5). Since detection of disease-specific auto-ab may be critical for diagnosis of MMP, we developed an ELISA with affinity-purified native human LN5. A total of 24 MMP, 72 BP, and 51 control sera were analyzed for LN5-specific auto-ab: 18/24 (75.0%) MMP and 29/72 (40.3%) BP sera were LN5 reactive. Sensitivity and specificity of the LN5 ELISA for MMP were 75% and 84.3%, respectively, and 40.3% and 88.2% for BP, respectively. The LN5 ELISA was more sensitive than a dot blot assay with native LN5, which detected LN5-reactive IgG in 14/24 (58.3%) MMP and 16/72 (22.2%) BP sera. In MMP, but not BP, levels of LN5-reactive IgG correlated with disease severity. Furthermore, IgG reactivity to LN5 of the MMP and BP sera was not significantly associated with IgG reactivity against other autoantigens of the BMZ, such as BP180 or BP230. Thus, the established LN5 ELISA holds great promise as a novel diagnostic and prognostic parameter for MMP.

Development of a novel ELISA system for detection of anti-BP180 IgG and characterization of autoantibody profile in bullous pemphigoid patients

BACKGROUND

The NC16A immunodominant region of the bullous pemphigoid (BP) antigen BP180 has been used to develop several enzyme-linked immunosorbent assays (ELISAs) as diagnostic tools for BP autoantibody detection.

OBJECTIVES

Because BP180 autoantibody reactivity is not restricted to NC16A, we have investigated the possibility of developing an ELISA based on selected epitopes additional to this immunodominant region.

METHODS

Initially 78 BP sera were tested using an NC16A ELISA and IgG reactivity was detected in 64 BP sera (82%). The 14 NC16A-negative BP sera were then analysed by immunological screening against seven BP180-specific epitopes. Recombinant phages displaying BP180 epitopes were grown as plaques, blotted onto a nitrocellulose filter and incubated with BP sera.

RESULTS

Three and five NC16A-negative BP sera reacted with epitopes AA 1080-1107 and AA 1331-1404 of the BP180 ectodomain, respectively. Thus, a novel ELISA with GST-1080 and GST-1331 (GST-1080/1331) was developed: 32 of 78 BP sera (41%) proved positive by this assay. The combined use of ELISAs with GST-NC16A and GST-1080/1331 detected IgG reactivity in 72 of 78 BP sera, increasing the sensitivity from 82% to 92%. In addition, autoreactivity against the three extracellular epitopes appeared to be related to the presence of both skin and mucosal involvement as assessed by Fisher's exact probability test.

CONCLUSIONS

Our findings further characterize the autoimmune response in BP by identifying a subgroup of NC16A-negative patients who react with different BP180 extracellular epitopes. The developed ELISA system appears more sensitive than the ELISA based on NC16A alone and also informative about the epitope profile of BP patients.

Analysis of antigens targeted by circulating IgG and IgA antibodies in patients with mucous membrane pemphigoid predominantly affecting the oral cavity

BACKGROUND

Mucous membrane pemphigoid (MMP) includes a range of variants frequently having oral, particularly gingival, lesions. It has been suggested that MMP exclusively involving the oral cavity could be a distinct subset, but the immunological status of patients with predominantly oral lesions has received little attention.

METHODS

Indirect immunofluorescence (IIF) on normal human skin and normal human salt-split skin (SSS) as a substrate and immunoblotting on extracts of human keratinocyte cultures and normal human skin were carried out in 28 consecutive patients with MMP predominantly affecting the gingiva.

RESULTS

There was no significant difference between frequency of positive SSS-IIF among patients with exclusive oral lesions (42%) and with MMP not restricted to the oral cavity (78%) (P = 0.114). By immunoblotting, IgG of 13 sera (46%) reacted with the 180 kD bullous pemphigoid antigen (BPAg2), six (21%) reacted with the 230 kD bullous pemphigoid antigen (BPAg1), and two (7%) reacted with an antigen of 200 kD. IgA of three sera (11%) reacted with BPAg2 and three (11%) reacted with BPAg1. There was no significant difference between frequency of positive immunoblotting among patients with exclusive oral lesions (68%) and with MMP not restricted to the oral cavity (67%) (P = 1.00).

CONCLUSIONS

Most of the MMP sera contain IgG and IgA antibodies to the two major bullous pemphigoid antigens, independent of clinical presentation. Thus, in the majority of cases, patients with exclusively gingival pemphigoid lesions do not appear to have a distinct variety of mucous membrane pemphigoid.

BP230- and BP180-specific auto-antibodies in bullous pemphigoid

Bullous pemphigoid is a subepidermal blistering disease associated with auto-antibodies (auto-ab) to BP180 and BP230. We developed ELISAs utilizing baculovirus-encoded recombinant proteins of BP230 and BP180 and studied their diagnostic and prognostic values by assessing the profile of the auto-ab response in 127 patients with BP. 39 patients had focal involvement, whereas 88 had generalized disease; 51 individuals served as controls. The results indicate: (1) BP180 IgG reactivity was associated with an overall sensitivity of 0.953 and specificity of 0.940; (2) 105 of 127 BP patients also displayed BP230 auto-reactivity, the global diagnostic performance of which, however, was moderate compared to BP180-auto-reactivity (sensitivity 0.815 vs 0.953, specificity 0.648 vs 0.940); (3) 101 patients (79.5%) had concordant BP180 and BP230 reactivity; (4) the association between the presence of BP230 auto-reactivity and focal involvement was stronger than in generalized disease (odds ratio (OR) 17.7 vs 10.2), independently from BP180 auto-ab profile; (5) correlation of total IgG with IgG1 and IgG4 was variable for both BP180 and BP230. Collectively, the global diagnostic properties of the BP180-ELISA outperform those of the BP230-ELISA. Presence of BP230 auto-reactivity, however, supports the diagnosis of BP and might be indicative for the extent of the disease.

Development of an ELISA for the detection of autoantibodies to BP230

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease associated with autoantibodies against the transmembrane hemidesmosomal protein BP180/collagen type XVII and the intracellular plaque protein BP230. The aim of the present study was to develop an ELISA system for the detection of circulating autoantibodies to BP230. We generated five overlapping cDNA constructs covering the entire length of BP230 and expressed them in baculovirus-infected Sf21 insect cells. ELISA reactivity against BP230 was found in 63% of 56 BP patients' sera; the specificity of the ELISA was 93%. Epitope mapping studies showed that the fragment representing the C-terminal portion of BP230 was by far the most frequent target within the molecule. This ELISA provides a useful tool for the detection of autoantibodies to BP230 in BP and other diseases associated with an autoimmune response to this protein.

Characterization of the anti-BP180 autoantibody reactivity profile and epitope mapping in bullous pemphigoid patients

Bullous pemphigoid is a subepidermal bullous disease of skin and mucosae associated with autoantibodies to BP180. To characterize the humoral response to BP180, we generated a random BP180 epitope library displayed on lambda bacteriophage. After validation of the library by epitope mapping of three BP180-specific monoclonal antibodies, 15 novel or known BP180 epitopes were identified using 10 bullous pemphigoid serum samples. Fifty-seven bullous pemphigoid and 81 control sera were then assayed against the selected epitopes. Thirty-one out of 57 (54%) bullous pemphigoid sera reacted with at least an additional antigenic site other than the NC16A, within the extracellular (37%) and intracellular (28%) domains of BP180. In addition, the reactivity with extracellular epitopes of BP180 contained within the residue stretches 508-541 and 1331-1404 appeared to be related to the presence of both skin and mucosal involvement. Finally, a preliminary analysis of the epitope pattern in the disease course indicated that bullous pemphigoid patients exhibit a specific reactivity pattern, and that binding to intracellular epitopes of BP180, in addition to NC16A, may be detectable at an early clinical stage. Our findings provide novel insights into the pathophysiology of bullous pemphigoid and show the potential of the utilized approach as a tool for a rapid diagnosis of bullous pemphigoid patients and their management.

Pemphigoid gestationis with predominant involvement of oral mucous membranes and IgA autoantibodies targeting the C-terminus of BP180

Pemphigoid gestationis (PG) is an autoimmune pregnancy-associated subepidermal blistering disease. It usually affects skin and, rarely, mucous membranes. In the vast majority of patients with PG, the autoimmune response is directed to the membrane-proximal NC16A domain of the 180-kd bullous pemphigoid (BP) antigen (BP180) and is mediated by IgG1 and IgG3 autoantibodies. We report the case of a patient with PG associated with extensive lesions on oral mucous membranes. Immunoblotting studies demonstrated the presence of circulating IgA autoantibodies in the patient's serum that were exclusively directed to a 49 amino acid stretch on the C-terminal portion of the BP180 ectodomain located 800 amino acids downstream from NC16A. This C-terminal stretch of BP180 has previously been demonstrated to localize to the lamina lucida/lamina densa interface and to be recognized by IgG and IgA antibodies in a subgroup of patients with cicatricial pemphigoid as well as by IgG autoantibodies in some BP sera. Our patient's lesions healed without scarring within 6 weeks after delivery of a healthy child. The findings in this patient extend the clinical and immunopathologic spectrum of PG.

Severity and phenotype of bullous pemphigoid relate to autoantibody profile against the NH2- and COOH-terminal regions of the BP180 ectodomain

Bullous pemphigoid, the most common autoimmune subepidermal bullous disorder, is associated with autoantibodies targeting antigenic sites clustered within the extracellular domain of BP180. To investigate epitope and subclass specificity of autoantibodies in bullous pemphigoid, we developed an enzyme-linked immunosorbent assay utilizing baculovirus-expressed recombinant forms of the NH2- and COOH-terminal regions of the extracellular domain of BP180 and examined sera obtained from patients with active bullous pemphigoid (n=116) and controls (n=100). Ninety-three (80%) and 54 (47%) of the 116 bullous pemphigoid sera recognized the NH2- and COOH-terminal regions, respectively, of the extracellular domain of BP180. Detailed analysis demonstrates that (i) this novel enzyme-linked immunosorbent assay is highly specific (98%) and sensitive (93%) as 108 of 116 bullous pemphigoid sera reacted with at least one of the baculovirus-derived recombinants, (ii) in active bullous pemphigoid, autoantibodies against the NH2-terminus of the extracellular domain of BP180 were predominantly of the IgG1 class, whereas a dual IgG1 and IgG4 response to this region was related to a more severe skin involvement, (iii) autoreactivity against both the NH2- and COOH-terminal regions was more frequently detected in patients with mucosal lesions, and (iv) levels of IgG (and IgG1) against the NH2-terminal, but not against the COOH-terminal portion of the extracellular domain of BP180, reflected disease severity indicating that autoantibodies against the NH2-terminus are critical in the pathogenesis of bullous pemphigoid. In conclusion, this novel enzyme-linked immunosorbent assay represents a highly sensitive and specific assay for rapid diagnosis of bullous pemphigoid and related disorders and may provide predictive parameters for the management of bullous pemphigoid patients.

Laminin-5 is targeted by autoantibodies in feline mucous membrane (cicatricial) pemphigoid

In human and canine patients with mucous membrane (cicatricial) pemphigoid (MMP), circulating autoantibodies have been shown to target multiple epidermal basement membrane antigenic epitopes. These autoantigens include collagen XVII in humans and dogs, as well as laminin-5, laminin-6 or integrin alpha-6/beta-4 in human beings. The purpose of this study was to determine if autoantibodies targeted laminin-5 in a cat exhibiting clinical and microscopic lesions resembling those of MMP in humans. In this patient, an indirect immunofluorescence (IF) assay revealed circulating IgG and IgA autoantibodies that bound to the basement membrane zone on the dermal side of salt-split gingiva (titer 1:1000 for IgG and 1:50 for IgA). Immunoblotting, performed with affinity-purified human laminin-5, demonstrated that the autoantibodies bound the alpha-3 chain of this heterotrimer. These observations identify laminin-5 as one of the antigens recognized by circulating autoantibodies in this feline homologue of MMP in humans and dogs.

Cicatricial pemphigoid-induced phimosis

Cicatricial pemphigoid is an autoimmune bullous disease that has a predilection for mucous membranes and often results in scarring. We describe a case of cicatricial pemphigoid with severe involvement of the glans penis, which, despite systemic therapy, led to phimosis.

Cicatricial pemphigoid with circulating IgA and IgG autoantibodies to the central portion of the BP180 ectodomain: beneficial effect of adjuvant therapy with high-dose intravenous immunoglobulin

Cicatricial pemphigoid (CP) is an autoimmune subepidermal blistering disease characterized by deposits of IgG, IgA, or C3 at the cutaneous basement membrane zone. CP may present with considerable variation regarding age, morphology of lesions, and mucosal involvement, which may heal with or without scarring. We describe a patient with CP who presented with circulating IgA and IgG autoantibodies to the epidermal side of salt-split human skin. By immunoblot analysis, the patient's IgA reacted with the soluble ectodomain of BP180 (LAD-1). This reactivity was mainly directed to the central portion of the BP180 ectodomain, a site that, to date, has not been described as the target of IgA autoantibodies. Different immunosuppressive treatment regimens including steroids and mycophenolate mofetil did not control this patient's disease, and severe scarring of the conjunctivae occurred with impairment of vision. Addition of adjuvant intravenous immunoglobulin (1 g/kg body weight on 2 consecutive days) every 4 weeks led to a dramatic improvement of conjunctivitis and gingivitis. Clinical improvement correlated with the serum's IgA immunoblot reactivity against LAD-1. Further studies on a larger number of patients with CP should try to correlate the specificity of autoantibodies in CP with the response to certain therapeutic regimens.

Cicatricial pemphigoid differs from bullous pemphigoid and pemphigoid gestationis regarding the fine specificity of autoantibodies to the BP180 NC16A domain

Bullous pemphigoid (BP), pemphigoid (herpes) gestationis (PG), cicatricial pemphigoid (CP), and lichen planus pemphigoides (LPP) are autoimmune subepidermal bullous diseases that are characterized by circulating autoantibodies to the transmembrane hemidesmosomal protein BP180/type XVII collagen. Previous studies demonstrated that the majority of patients with BP, PG, and LPP show antibodies to an immunodominant, membrane-proximal non-collagenous domain (NC16A) on the extracellular portion of BP180. By the use of non-overlapping peptides of the NC16A domain, we previously demonstrated that autoantibodies from BP and PG patients mainly react with epitopes clustered within the N-terminus of this immunodominant site of BP180; antibodies from patients with LPP also recognized the C-terminal portion of NC16A. However, some of these results had been obtained indirectly by preadsorption studies. The aim of the present study was to analyze the fine specificity of IgG autoantibodies to NC16A in sera from patients with CP and to compare their reactivity with antibodies from BP, PG, and LPP patients using a series of new overlapping fragments covering the entire NC16A domain. We confirm that BP and PG sera mainly react with N-terminal epitopes of NC16A, whereas sera from patients with LPP also bind to C-terminal portions, of this domain. Interestingly, out of ten patients with CP, the sera of seven reacted with NC16A; within NC16A, these sera bound to both C-terminal fragments and an N-terminal epitope right next to the cell membrane. Our data demonstrate a heterogeneous binding pattern of autoantibodies to BP180 NC16A in patients with CP.

False-negative results in immunoblot assay of serum IgA antibodies reactive with the 180-kDa bullous pemphigoid antigen: the importance of primary incubation temperature

BACKGROUND

Different subepidermal autoimmune blistering skin disorders are characterized by linear deposition of IgA, sometimes accompanied by linear IgG, along the epidermal basement membrane zone. Identification of the targeted autoantigen is usually attempted by immunoblotting. Although immunoblotting works well for human IgG, the method is less successful for IgA and often no or only faint signals are obtained.

OBJECTIVES

To improve the method of immunoblotting for diagnosis of IgA-mediated bullous dermatoses.

METHODS

Eleven sera, selected from patients with linear deposition of IgA along the epidermal basement membrane zone in vivo, were tested by immunoblotting for antigen specificity using different primary incubation temperatures.

RESULTS

No reliable information regarding IgA antigen specificity was obtained when the primary incubation was undertaken at room temperature. In 10 of 11 sera, IgA bound to the 180-kDa bullous pemphigoid antigen (BP180) when the primary incubation temperature was increased to 37 degrees C.

CONCLUSIONS

Primary incubation at room temperature may result in false-negative results in the IgA-BP180 immunoblot assay.

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.

Cicatricial pemphigoid: IgA and IgG autoantibodies target epitopes on both intra- and extracellular domains of bullous pemphigoid antigen 180

BACKGROUND

Cicatricial pemphigoid (CP) is an autoimmune subepidermal blistering disease where autoantibodies target various components of the dermal-epidermal junction, including the bullous pemphigoid antigen 180 (BP180).

OBJECTIVE

We determined the exact specificity of circulating IgG and IgA autoantibodies to BP180 in a large number of CP patients.

METHODS

Twenty-six consecutive CP sera were analysed by Western blotting using a panel of cell-derived and recombinant proteins covering the entire BP180 molecule.

RESULTS

Circulating autoantibodies were detected in all CP sera. Seven sera reacting with laminin-5 were excluded from further analyses; the remaining 19 sera recognized BP180, including six sera (32%) that showed only IgA reactivity to this protein. With the combined use of the soluble BP180 ectodomain (LAD-1) and recombinant BP180 NC16A, 16 of these 19 CP sera (84%) targeted BP180. IgG reactivity was preferentially found against NC16A, whereas IgA antibodies predominantly recognized LAD-1. Thirty-two per cent of the BP180-reative sera revealed reactivity with the intracellular domain of this protein.

CONCLUSIONS

Our findings demonstrate that autoantibodies in CP target epitopes on both extra- and intracellular domains of BP180 and highlight the importance of testing for both IgG and IgA reactivity in these patients' sera.

Mucous membrane pemphigoid: HLA-DQB1*0301 is associated with all clinical sites of involvement and may be linked to antibasement membrane IgG production

BACKGROUND

Class I human leucocyte antigens (HLA) -A, -B, -Cw and class II HLA-DRB1, -DQB1 alleles were determined in 131 British Caucasian patients with mucous membrane pemphigoid (MMP) using serological and DNA-based methods.

OBJECTIVES

To analyse the class I and II alleles expressed in well-defined clinical and immunopathological subgroups of MMP, in order to establish whether specific alleles or haplotypes might in part explain disease susceptibility, clinical sites of involvement or disease severity.

METHODS

Subgroups of patients were analysed according to the following clinical criteria: age of onset, sex, sites of clinical involvement (oral, ocular, skin, nasal, genital, pharyngeal, oesophageal, laryngeal, perianal), disease severity and history of autoimmune disease. Subgroups were also analysed according to the following immunopathological criteria: autoantibody profile, the presence of circulating antibasement membrane IgG or IgA antibodies and the detection of target basement membrane zone (BMZ) antigens (BP230 and BP180) by IgG autoantibodies.

RESULTS

Class I HLA typing showed no significant disease or subgroup associations. Class II DRB1 typing showed a significantly increased allelic frequency in MMP vs. controls for DRB1*11 (RR = 2.08, Pc < 0.0000056). For DQB1, MMP vs. controls, there was a significantly increased allelic frequency for DQB1*0301 (Pc < 0.00000028) in both males and females; all clinical sites of involvement, with the exception of laryngeal, oesophageal and perianal sites and in patients with detectable circulating anti-BMZ IgG compared with those negative for IgG (P < 0.0096, Pc < 0.019). A positive trend was noted in patients with ocular involvement compared with no ocular involvement and in patients with a clinical score > or = 10 compared with < 10. We found no difference in DQB1*0301 allele frequency between subgroups with or without BP180 or BP230 target antigens. Haplotype frequencies showed an increase in DRB1*04, DQB1*0301 (Pc < 0.000066) and DRB1*11, DQB1*0301 (Pc < 0.000002) among patients compared with controls.

CONCLUSIONS

The DQB1*0301 allele confers a predisposition to all subgroups of MMP and may have a role in T-cell recognition of basement membrane antigens, resulting in the production of anti-BMZ IgG autoantibodies. The positive trend between increased allelic expression of DQB1*0301 in patients with ocular disease and in those with a higher clinical score, further suggests a role for this allele in disease severity.

Immunodiagnosis of pemphigus and mucous membrane pemphigoid

Pemphigus and pemphigoid are two of a group of bullous diseases affecting oral mucosa and skin. Mucous membrane pemphigoid (MMP) comprises a heterogeneous group of disorders characterized by subepithelial separation and the deposition of immunoglobulins and complement along the basement membrane zone (BMZ). The target antigens in the epithelium and BMZ determine the nature of the condition, and recently there have been considerable improvements in our understanding of the BMZ antigenic composition. Pemphigus vulgaris (PV) is characterized by autoantibodies of the IgG isotype to the desmosomal glycoprotein desmoglein (Dsg) 3, whereas pemphigus foliaccus targets Dsg1, although at least 50% of PV patients have additional autoantibodies to Dsg1. The clinical phenotype appears to be determined by the relative amounts of Dsg1 and Dsg3. Patients with oral or mucosal PV have predominantly Dsg3 autoantibodies. The most frequently targeted antigen in MMP is bullous pemphigoid antigen 180 (BP180), although bullous pemphigoid antigen 230 (BP230), laminin 5, and beta 4 integrin are also involved. Circulating IgG and IgA antibodies may bind to different epitopes of BP180 namely the NC 16A domain or COOH -terminal domain. Pure ocular disease has been associated with IgA antibodies to a 45-kDa antigen and IgG antibodies to the 205-kDa antigen b4 integrin. The use of salt-split skin substrate enables differentiation between epidermal and dermal 'binders'. Since both the specificity and the antibody titer appear to have direct relationships with the disease severity, and a combination of clinical score and antibody titer provides valuable prognostic data, these investigations should be carried out on a more routine basis.

Bullous pemphigoid induced by cephalexin

Two young men developed severe bullous eruptions with a distinctive clinical picture of severe flexural involvement and extensive mucosal ulceration. Biopsies showed subepidermal bullae and associated inflammation consisted of predominantly neutrophils. Both had IgG and C3 staining of the dermal-epidermal junction on direct immunofluorescence. Bullous pemphigoid was diagnosed on the basis of clinical, histopathological and immunofluorescence findings. Both cases occurred after recent ingestion of cephalexin. We believe they represent the first reported cases of bullous pemphigoid induced by cephalexin.

Immunopathological diagnosis of cicatricial pemphigoid with desquamative gingivitis. A case report

Cicatricial pemphigoid (CP) is a chronic subepidermal bullous dermatosis which primarily involves the mucous membranes. The oral cavity and the eye are most frequently involved. Since extension of the lesion into the pharynx and esophagus causes sore throat and dysphagia and progressive ocular lesions may cause blindness, early and valid diagnosis is very important. Here we present a case of cicatricial pemphigoid with onset at age 45 in a patient who manifested severe periodontal disease and showed the lesion on the mucous membranes of the mouth (desquamative gingivitis), skin, and eyes. Since definite diagnosis is very important, we describe how we made a differential diagnosis from other diseases which also accompany desquamative gingivitis. We examined the clinical manifestations, blood test results, HLA-genotype, histopathologic findings of the affected tissue, and immunological findings in relation to autoimmunity. Since many of the CP cases are first referred to periodontists or dentists, we believe that the diagnostic strategy described in the present study will be quite informative for making rapid and definite diagnoses of similar cases.

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.

Autoantibodies in a subgroup of patients with linear IgA disease react with the NC16A domain of BP1801

Linear IgA disease is an autoimmune subepidermal blistering disease characterized by IgA deposits at the cutaneous basement membrane zone. IgA antibodies from linear IgA disease sera react with antigens of 97 kDa (LABD97) and 120 kDa (LAD-1), both of which appear to be fragments of the extracellular domain of bullous pemphigoid 180 (type XVII collagen). The aim of this study was to determine whether linear IgA disease sera react with the immunodominant region of BP180 (NC16A domain), which is a major target of IgG autoantibodies produced by patients with bullous pemphigoid. Indeed, 11 of 50 linear IgA disease sera were found to contain IgA autoantibodies that recognized a recombinant form of NC16A by immunoblotting. The same sera also reacted with NC16A by enzyme-linked immunosorbent assay. An epitope mapping analysis uncovered four linear IgA disease-associated epitopes located within the 45 amino acid N-terminal stretch of NC16A, all of which were previously identified as antigenic sites targeted by bullous pemphigoid autoantibodies. Eight of the linear IgA disease sera that were reactive with NC16A also recognized LAD-1 secreted by the SCC-25 cell line, and five sera recognized BP180 extracted from keratinocytes. Linear IgA disease sera depleted of reactivity to NC16A by immunoadsorption continued to react with both the LAD-1 antigen and BP180 by immunoblotting and with the basement membrane zone by indirect immunofluorescence microscopy. Our results demonstrate that IgA autoantibodies from a subset of linear IgA disease patients react with the same sites on BP180 that are targeted by IgG autoantibodies in bullous pemphigoid.

Successful treatment of recalcitrant cicatricial pemphigoid with a combination of plasma exchange and cyclophosphamide

We describe two patients with severe oral cicatricial pemphigoid, one of whom also had severe pharyngeal involvement. Both patients were resistant to treatment with corticosteroids and other standard immunosuppressive therapies. Plasma exchange alone proved to be only temporarily effective, but the combination of plasma exchange with subsequent cyclophosphamide resulted in a remission in both patients. Both patients experienced mild side-effects during the plasma exchange treatment (urticaria and mild hypotension). At present, at follow-up of 6 and 9 years, respectively, the patients have no symptoms of active disease and have not required any further immunosuppressive treatment.

Autoantibodies in lichen planus pemphigoides react with a novel epitope within the C-terminal NC16A domain of BP180

Lichen planus pemphigoides is an autoimmune subepidermal blistering disease. The finding of immunoglobulin G antibodies directed against the basement membrane zone differentiates it from bullous lichen planus. The aim of this study was to identify the target antigen of lichen planus pemphigoides autoantibodies. Sera from lichen planus pemphigoides patients (n = 4) stained the epidermal side of NaCl-split human skin in a pattern indistinguishable from that produced by bullous pemphigoid sera. In bullous pemphigoid, the autoimmune response is directed against BP180, a hemidesmosomal transmembrane collagenous glycoprotein. We previously demonstrated that bullous pemphigoid sera predominantly react with a set of four epitopes (MCW-0 through MCW-3) clustered within a 45 amino acid stretch of the major noncollagenous extracellular domain (NC16A) of BP180. By immunoblotting and enzyme-linked immunosorbent assay, lichen planus pemphigoides sera were also strongly reactive with recombinant bullous pemphigoid 180 NC16A. The lichen planus pemphigoides epitopes were further mapped using a series of overlapping recombinant segments of the NC16A domain. All lichen planus pemphigoides sera reacted with amino acids 46-59 of domain NC16A, a protein segment that was previously shown to be unreactive with bullous pemphigoid sera. Two lichen planus pemphigoides sera, in addition, reacted with the immunodominant antigenic region associated with bullous pemphigoid. In conclusion, there are now five bullous diseases that are associated with an autoimmune response to BP180: bullous pemphigoid; pemphigoid/herpes gestationis; cicatricial pemphigoid; linear immunoglobulin A disease; and lichen planus pemphigoides. In addition, we have identified a novel epitope within the BP180 NC16A domain, designated MCW-4, that appears to be uniquely recognized by sera from patients with lichen planus pemphigoides.

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.

The immunoglobulin A antibody response in clinical subsets of mucous membrane pemphigoid

BACKGROUND

Mucous membrane pemphigoid (MMP) is an immunobullous disease. In MMP there is frequently a mixed antibody response with the presence of IgA and/or IgG antibodies directed toward basement membrane zone antigens. The IgG antibody response in MMP has been studied, but the antigens to which the IgA antibodies react have not been studied.

OBJECTIVE

To determine the IgA autoantibody reactivity profiles in patients with MMP.

METHODS

Patients who had both ocular and oral MMP were compared with patients who had ocular or oral MMP and with patients who had cutaneous linear IgA disease (LABD) by Western immunoblot studies.

RESULTS

Five of 15 MMP patients and 1 of 5 LABD patients had IgA antibodies reactive with the 180-kD bullous pemphigoid antigen. Seven of 15 MMP patients had IgA antibodies reactive with the 97-kD LABD antigen.

CONCLUSION

Major antigens in IgA MMP are the 180-kD bullous pemphigoid antigen and the 97-kD LABD antigen.

Antiepiligrin cicatricial pemphigoid represents an autoimmune response to subunits present in laminin 5 (alpha3beta3gamma2)

Sera from 20 patients with antiepiligrin cicatricial pemphigoid were studied to define the specific reactivity of their IgG autoantibodies. IgG from all patients bound exclusively to the dermal side of 1 mol/L NaCl split skin and immunoprecipitated laminin 5 (alpha3beta3gamma2) from extracts of human keratinocytes (HKs). Immunoblot studies on purified laminin 5 subunits demonstrated that patient IgG bound alpha3 alone in 16 patients. In two patients, IgG autoantibodies were directed predominantly to the gamma2 subunit, yet showed trace reactivity to alpha3 as well. Sera from two patients did not immunoblot any laminin 5 subunits, their IgG presumably immunoprecipitating laminin 5 via a conformational epitope. Sera from patients with alpha3 subunit-specific IgG immunoprecipitated all subunits of laminin 5 as well as polypeptides of 190 and 200 kDa from the conditioned media of HKs. Preclearance studies and experiments utilizing affinity-purified patient IgG demonstrated that the latter signified laminin 6 (alpha3beta1gamma1) that was bound by cross-reactive alpha3 subunit-specific patient IgG. Sera from patients with gamma2 subunit-specific IgG showed no reactivity to laminin 6, except for faint reactivity provided by low levels of their alpha3 subunit-specific IgG. Taken together, these findings indicate that antiepiligrin cicatricial pemphigoid signifies an autoimmune response to subunits present in laminin 5.