The anti-desmoglein 1 autoantibodies in pemphigus vulgaris sera are pathogenic

Pemphigus vulgaris and pemphigus foliaceus are two closely related, but clinically and histologically distinct, autoimmune skin diseases. The autoantigens for pemphigus vulgaris and pemphigus foliaceus are desmoglein 3 and desmoglein 1, respectively. The anti-desmoglein 1 antibodies in pemphigus foliaceus and anti-desmoglein 3 antibodies in pemphigus vulgaris are pathogenic as determined by immunoglobulin G passive transfer animal models. More than 50% of pemphigus vulgaris sera also contain anti-desmoglein 1 autoantibodies; however, the pathogenicity of the anti-desmoglein 1 autoantibodies in pemphigus vulgaris remains unknown. In this study, we used soluble recombinant extracellular domains of desmoglein 1 and desmoglein 3 to obtain affinity-purified anti-desmoglein 1 and anti-desmoglein 3 autoantibodies from pemphigus vulgaris sera and examined the pathogenicity of each fraction separately using the passive transfer mouse model. By immunoprecipitation, the purified anti-desmoglein 1 and anti-desmoglein 3 showed no cross-reactivity. The anti-desmoglein 1 autoantibodies in pemphigus vulgaris induced typical pemphigus foliaceus lesions in neonatal mice, whereas the anti-desmoglein 3 fraction induced pemphigus vulgaris-like lesions. In addition, the pathogenic anti-desmoglein 1 and anti-desmoglein 3 autoantibodies in pemphigus vulgaris had predominant IgG4 subclass specificity. These findings suggest that the anti-desmoglein 1 antibodies in pemphigus vulgaris are pathogenic.     

Immunologic and histopathologic characterization of an active disease mouse model for pemphigus vulgaris

Pemphigus vulgaris is an autoimmune blistering disease of the skin and mucous membranes that is caused by anti-desmoglein 3 IgG autoantibodies. Recently, we generated an active disease mouse model for pemphigus vulgaris by adoptive transfer of splenocytes from immunized desmoglein 3-/- mice to Rag2-/- mice. In this study, we performed immunologic and histopathologic studies using this pemphigus vulgaris model in mice and compared the gross and microscopic phenotypes of pemphigus vulgaris model mice and desmoglein 3-/- mice. Pemphigus vulgaris model mice showed strong in vivo IgG, and weak IgA deposition on keratinocyte cell surfaces in stratified squamous epithelia, and produced circulating anti-desmoglein 3 IgG antibodies without apparent cross-reactivity to desmoglein 1, in enzyme-linked immunosorbent assays. The predominant IgG subclass was IgG1. Pemphigus vulgaris model mice and desmoglein 3-/- mice were almost indistinguishable in terms of both gross and microscopic findings. Both types of mice showed suprabasilar acantholysis in the stratified squamous epithelia, including the oral mucous membranes and traumatized skin around the snout or paws; however, some pemphigus vulgaris model mice demonstrated a more severe phenotype than desmoglein 3-/- mice. The esophagus and forestomach were affected in some pemphigus vulgaris model mice, but not in desmoglein 3-/- mice. Furthermore, eosinophilic spongiosis, which is found in early pemphigus vulgaris lesions in patients, was observed in pemphigus vulgaris model mice but not in desmoglein 3-/- mice. Pemphigus vulgaris model mice reflect several of the histopathologic and immunologic features seen in pemphigus vulgaris patients, and provide a valuable tool to investigate the pathophysiologic mechanisms of pemphigus vulgaris.     

Pemphigus,a pathomechanism of acantholysis

Autoantibodies to the desmosomal proteins desmoglein 1 and 3 cause pemphigus foliaceus and pemphigus vulgaris, which are characterised by keratinocyte dissociation (acantholysis) and intraepidermal blister formation. The passive transfer of pathogenic anti‐desmoglein antibodies induces blisters in mice in vivo and the loss of keratinocyte adhesion in vitro. The pathogenetic mechanisms of acantholysis due to anti‐desmoglein autoantibodies are not fully understood. However, recent studies have revealed that signalling‐dependent and signalling‐independent pathways are operative in the loss of cell adhesion. In this review, we focus on the pathomechanism of acantholysis due to autoantibodies to desmogleins and recent therapeutic approaches.     

Cutaneous type pemphigus vulgaris: a rare clinical phenotype of pemphigus

Pemphigus is an autoimmune blistering disease of the skin, mucous membranes, or both. There are two main categories of pemphigus: pemphigus foliaceus (PF) and pemphigus vulgaris (PV). PV is further subdivided into mucosal dominant and mucocutaneous types, according to the extent of cutaneous lesions. These classes of pemphigus have distinct histopathologic and serologic findings, with most cases falling into these subtypes. We report 4 cases that clinically showed blisters and erosions in the skin only, without mucosal involvement. Histologic examination of cutaneous lesions demonstrated suprabasilar acantholysis, a typical finding for PV. These patients had predominant anti-desmoglein 1 (Dsg1) IgG autoantibodies as well as anti-Dsg3 IgG autoantibodies, as determined by enzyme-linked immunosorbent assay. The desmoglein compensation theory posits that this rare phenotype can be produced by pathogenically weak anti-Dsg3 IgG in the presence of potent anti-Dsg1 IgG autoantibodies. Thus, cutaneous type PV without apparent mucosal involvement is observed as a rare clinical and histologic expression of pemphigus. This expression can be a transient phenotype that may develop from, or evolve into, other subtypes of pemphigus.     

Pemphiguserkrankungen bei Kindern und Jugendlichen

The pemphigus diseases, which include some of the most severe bullous autoimmune skin reactions, are seen predominantly in middle-aged and elderly individuals. Only endemic pemphigus foliaceus in South America most frequently affects juveniles and children. All non-endemic pemphigus diseases, including paraneoplastic pemphigus, have been reported to occur in adolescents and even very rarely in children younger than 10 years. Pemphigus vulgaris in pregnancy represents a frequently overseen medical problem and may result in fetal growth retardation, intrauterine death, premature delivery and – in about 30% – in neonatal pemphigus vulgaris of the newborn. Contrary to pemphigus vulgaris, the transplacental crossing of autoantibodies against desmoglein1 in pregnant women with pemphigus foliaceus hardly ever leads to neonatal skin lesions in the offspring. This phenomenon can be explained by differences in the distribution and cross-compensation of the pemphigus antigens desmoglein3 and 1 in neonatal and adult skin or mucosa, respectively.     

Oxidative stress in patients with endemic pemphigus foliaceus and healthy subjects with anti-desmoglein 1 antibodies

Background:Previous studies have shown oxidative stress in pemphigus vulgaris and pemphigus foliaceus, nevertheless, it remains unknown whether a similar response is characteristic of endemic pemphigus foliaceus in Peru.Objectives:To determine the oxidative stress response in endemic pemphigus foliaceus patients and subjects with positive for anti-desmoglein1 antibodies (anti-dsg1) from endemic areas of Peru.Subjects and methods:This is a cross-sectional study. The study population included 21 patients with Endemic Pemphigus foliaceus and 12 healthy subjects with anti-dsg1 antibodies from the Peruvian Amazon (Ucayali), as well as 30 healthy control subjects. Malondialdehyde, an indicator of lipid peroxidation by free radicals, was measured in serum.Results:We collected 21 cases of endemic pemphigus foliaceus, 15 of them with active chronic disease and 6 in clinical remission. Serum malondialdehyde values in patients with chronic active evolution and healthy subjects with anti-dsg1 antibodies were statistically higher than those of healthy controls (p<0.001). There was no significant difference between serum values of localized and generalized clinical forms.Study limitations:The main limitation of this present study is the small number of patients with endemic pemphigus and healthy subjects positive for desmoglein 1 antibodies.Conclusions:The increased serum levels of malondialdehyde in patients with chronic active endemic pemphigus foliaceus and healthy subjects from endemic areas with anti-dsg1 antibodies may suggest a contribution of systemic lipid peroxidation in the pathogenesis of endemic pemphigus foliaceus.     

Spectrum of autoantibodies other than anti‐desmoglein in pemphigus patients

Background Pemphigus is a life‐threatening autoimmune blistering disease mediated by autoantibodies against adhesion molecule of the skin. Its concurrence with systemic and organ‐specific autoimmune disease was described in case reports. Objectives To evaluate the presence of a broad spectrum of organ‐specific and non‐organ‐specific autoantibodies other than anti‐desmoglein antibodies in pemphigus patients. Patients and methods Serum samples were obtained from 105 pemphigus foliaceus (PF) patients, 51 pemphigus vulgaris (PV) patients and 50 controls. Both indirect immunofluorescence assay and ELISA were used to assess the presence of autoantibodies related to connective tissue diseases, autoimmune hepatitis, vasculitis, rheumatoid arthritis, coeliac disease, diabetes and thyroiditis. Results Significant difference was observed between the three groups for anti‐thyroglobulin antibodies in the pemphigus foliaceus group (18% vs. 4%, P = 0.03). A significantly higher occurrence of IgM anti‐cardiolipin (P = 0.03), IgG anti‐reticulin (P = 0.01) and IgG anti‐gliadin antibodies (P = 0.008) were observed in the PV group. Cases with more than four autoantibodies were frequently positives for both anti‐desmoglein 1 and anti‐desmoglein 3. Conclusion Autoantibodies other than anti‐desmoglein antibodies are not rare in pemphigus patients. Clinical and serological follow‐up of pemphigus patients with positive autoantibodies are needed to clarify their impact in disease evolution.     

Anti-desmoglein 1 antibodies in healthy related and unrelated subjects and patients with pemphigus foliaceus in endemic and non-endemic areas from Tunisia

Background  Pemphigus foliaceus is an autoimmune blistering skin disease characterized by the production of pathogenic IgG autoantibodies directed against desmoglein 1.
Aim  To determine the prevalence of anti-desmoglein 1 antibodies in healthy subjects and their distribution in the different regions of Tunisia and to better identify endemic areas of pemphigus foliaceus.
Methods  We tested, by enzyme-linked immunoserbent assay, sera of 270 normal subjects recruited from different Tunisian areas and 203 related healthy relatives to 90 Tunisian pemphigus foliaceus patients.
Results  Seventy-six patients (84.4%), 20 healthy controls (7.4%), and 32 relatives (15.76%) had anti-desmoglein 1 antibodies. In southern regions where pemphigus foliaceus is associated with a significant sex ratio imbalance (9 female : 1 male in the south vs. 2.3 : 1 in the north) and a lower mean age of disease onset (33.5 in the south vs. 45 years in the north), a higher prevalence of anti-desmoglein 1 antibodies in healthy controls was observed (9.23% vs. 5.71% in the north). Interestingly, the highest prevalence of anti-desmoglein 1 antibodies in healthy relatives (up to 22%) was observed in the most rural southern localities. More than half anti-desmoglein 1–positive healthy controls were living in rural conditions with farming as occupation, which suggests that this activity may expose the subjects to particular environmental conditions.
Conclusion  These results show that the endemic features of Tunisian pemphigus foliaceus are focused in these southern areas more than in other areas and that both environmental and genetic factors contribute to the disease.

Conflicts of interest

None declared.     

Pemphigus

Pemphigus diseases comprise a group of autoimmune disorders which are characterized by intraepidermal blisters and autoantibodies to components of desmosomes. Desmosomes mediate adhesion between neighbouring keratinocytes. A common feature of pemphigus diseases are intercellular deposits of IgG or, less frequently, of IgA within the epidermis. The group of pemphigus diseases includes pemphigus vulgaris, pemphigus foliaceus, pemphigus vegetans, pemphigus herpetiformis, pemphigus erythematosus, paraneoplastic pemphigus, drug-induced pemphigus, and IgA pemphigus. Using molecular tools, some of the autoantigens in these diseases have been characterized. In pemphigus vulgaris, autoantibodies are directed to desmoglein 3 and in pemphigus foliaceus to desmoglein 1. Target antigens in IgA pemphigus are desmocollin 1 and desmoglein 3. In paraneoplastic pemphigus, autoantibodies react with a complex of various proteins, including desmoplakin 1 and 2, BP230, envoplakin, periplakin, plectin, desmoglein 3, and a yet uncharacterized 170 kD protein. This review summarizes new insights into the immunopathogenesis and diagnosis of pemphigus diseases.     

Pemphigus foliaceus developing after metastasis of cutaneous squamous cell carcinoma to regional lymph nodes

We describe a patient in whom pemphigus foliaceus developed after cutaneous squamous cell carcinoma (SCC) metastasized to regional lymph nodes. Immunologic analysis revealed that production of anti-desmoglein 1 autoantibodies started when SCC metastasized, and the SCC expressed desmoglein 1, suggesting a pathogenic role of metastasized SCC in developing pemphigus foliaceus.     

Five Japanese cases of antidesmoglein 1 antibody-positive and antidesmoglein 3 antibody-negative pemphigus with oral lesions

Background Oral mucosal lesions develop in pemphigus vulgaris, but not in pemphigus foliaceus. This clinical phenomenon is explained by the ‘desmoglein (Dsg) compensation theory’. Dsg3 and Dsg1 are major autoantigens for pemphigus vulgaris and pemphigus foliaceus, respectively. Dsg3 is overexpressed and Dsg1 is weakly expressed on the oral mucosa. Thus, on the oral mucosa, suppression of Dsg3 function by anti‐Dsg3 autoantibodies is not compensated by weakly expressed Dsg1 in pemphigus vulgaris, while suppression of Dsg1 function by anti‐Dsg1 autoantibodies is perfectly compensated by richly expressed Dsg3 in pemphigus foliaceus. Objectives We present five Japanese patients with pemphigus who deviate from this theory, i.e. all patients showed oral lesions (three also had cutaneous lesions) and reacted only with Dsg1, but not with Dsg3, by enzyme‐linked immunosorbent assay. Methods To confirm whether the unique clinical phenotypes in our patients were due to a different immunological profile from that in classical pemphigus, we examined the reactivity of the patient sera by immunoprecipitation‐immunoblotting analysis using five Dsg1/Dsg2 domain‐swapped molecules. Results The sera of two patients who had only oral lesions tended to react with the extracellular (EC) 5 domain of Dsg1, the domain that is considered nonpathogenic in classical pemphigus foliaceus. Sera of three patients with mucocutaneous lesions reacted with EC1 domain or with both EC1 and EC2 domains of Dsg1, like classical pemphigus foliaceus. Conclusions These results indicate that antigenic diversity of anti‐Dsg1 antibodies in these patients may cause the unique oral mucosal and cutaneous lesions, although further studies are required to elucidate the pathomechanisms.     

Non-pathogenic anti-desmoglein 3 IgG autoantibodies in Fogo Selvagem

The endemic form of pemphigus foliaceus, fogo selvagem, is caused by IgG autoantibodies directed against desmoglein 1 (Dsg1). Hilario-Vargas and his colleagues describe a high prevalence of IgG autoantibodies against Dsg3, the target antigen of pemphigus vulgaris, in a Brazilian population where fogo selvagem is endemic, although those patients do not develop any apparent clinical phenotype of pemphigus vulgaris.     

Detection of antigen-specific B cells in patients with pemphigus vulgaris by enzyme-linked immunospot assay: requirement of T cell collaboration for autoantibody production

Patients with pemphigus vulgaris have circulating IgG autoantibodies against desmoglein 3, which inhibit cell-cell adhesion of keratinocytes and cause blister formation in the skin and mucous membrane. To examine cellular mechanisms underlying the autoantibody production in pemphigus vulgaris patients, we have successfully developed an enzyme-linked immunospot assay which was able to detect desmoglein 3-specific autoimmune B cells quantitatively. Circulating B cells producing anti-desmoglein 3 antibodies were detected exclusively in three patients with severe disease (1.3-2.3/105 peripheral blood mononuclear cells), but not in 10 patients with mild disease or in remission or in seven healthy individuals. When this enzyme-linked immunospot assay was combined with in vitro stimulation of peripheral blood mononuclear cells with pokeweed mitogen and recombinant-desmoglein 3, we could detect circulating desmoglein 3-specific memory B cells in nine of 14 patients (6.3-84. 0/105 peripheral blood mononuclear cells), but in none of 10 healthy individuals. We further analyzed the role of CD4 + T cells in promoting anti-desmoglein 3 antibody production. The in vitro anti-desmoglein 3 antibody production was abolished when CD4 + cells were depleted or when anti-HLA-DR or anti-HLA-DQ monoclonal antibody was added to the cultures. Our results demonstrated the quantitative detection of circulating "activated" and "memory" desmoglein 3-specific B cells and suggested the important part of HLA class II-restricted CD4 + T cells in the autoantibody production in pemphigus vulgaris. In addition, the enzyme-linked immunospot assay in combination with in vitro stimulation of B cells could be broadly applied to study mechanisms for autoantibody production in various autoimmune diseases.     

Curvicircular intracytoplasmic membranous structures in keratinocytes of pemphigus foliaceus

We noticed intracytoplasmic membranous, annular, or circular structures in the lesion of pemphigus foliaceus and studied these by regular transmission electron microscopy and immuno-electron microscopy. These curvicircular bodies were observed in the preacantholytic keratinocytes of the blister wall as well as in acantholytic cells in 6 out of 6 patients with pemphigus foliaceus. They were absent in samples from 3 patients with pemphigus vulgaris. These structures were about 60–70 nm wide and consisted of 4 electron-dense layers. They were continuous with intact desmosomal structures and gap junctions in the periphery of the keratinocytes. These curvicircular membranous bodies were well labeled with immunogold particles for desmoglein, plakoglobin, connexin 43, and IgG. In contrast to pemphigus vulgaris, splitting of desmosomes through dissolution of intercellular desmoglea was seldom observed in all 6 specimens of pemphigus foliaceus. These findings suggest that in pemphigus foliaceus 1) curvicircular bodies are derived from internalized desmosomes and gap junctions, and 2) cell-to-cell adhesions are weakened by this internalization and acantholysis is initiated, while in pemphigus vulgaris the dissolution of clesmoglea is the initial event. It is suggested that in pemphigus foliaceus the binding of autoantibody induces internalization of many intact desmosomes and gap junctions rather than splitting them.     

Upregulation of P-cadherin expression in the lesional skin of pemphigus, Hailey-Hailey disease and Darier's disease

BACKGROUND: Autoimmune blistering diseases, pemphigus vulgaris (PV) and pemphigus foliaceus (PF), are known to be caused by binding of autoantibodies to the desmosomal cadherins, desmoglein 3 and desmoglein 1, respectively. Recently, mutations in the genes coding Ca2+ pumps leads to inherited blistering diseases, Hailey-Hailey disease (HHD) and Darier's disease (DD). Cadherins are a family of Ca2+-dependent cell adhesion molecules and P-cadherin is one of the major cadherins expressed in the epidermis. Although detailed mechanisms of acantholysis of these blistering diseases have not been fully clarified, abnormal expression of cadherins caused by altered Ca2+ concentration due to the binding of autoantibodies to cell surface or by mutations in Ca2+ pumps is suggested to be involved in mechanisms of acantholysis of these autoimmune and inherited blistering diseases. The purpose of the present study was to determine whether altered P-cadherin expression is present in these diseases. METHOD: Distribution patterns of P-cadherin in skin specimens from patients with PV (n=2), PF (n=2), HHD (n=4) and DD (n=3), were examined with confocal laser scanning microscopy using two anti-P-cadherin antibodies, 6A9 and NCC-CAD-299. RESULTS: In normal control skin, P-cadherin expression was restricted to the basal layer. In contrast, positive immunostaining of P-cadherin was observed not only in the basal cells, but also in the suprabasal cells in lesional skin of all the acantholytic diseases. CONCLUSIONS: The present results clearly demonstrated that upregulation of P-cadherin expression occurs in the acantholysis in all the four blistering diseases PV, PF, HHD and DD. Upregulation of P-cadherin may be involved in the pathomechanism of both the autoimmune blistering diseases and the inherited blistering diseases.     

Signalling pathways in pemphigus vulgaris

Acantholysis in pemphigus vulgaris is induced by binding of autoantibodies to desmoglein 3 (Dsg3). The roles of signalling pathways on development of acantholysis have recently been extensively studied. In the study by Sayar et al., recently published in Exp Dermatol, epidermal growth factor receptor (EGFR) signalling was activated in both in vivo and in vitro pemphigus vulgaris experimental models. However, while EGFR inhibitors suppressed activity of p38 mitogen‐activated protein kinase (p38MAPK) linearly, they suppressed activity of c‐Myc and acantholysis in a non‐linear, V‐shaped relationship. These findings indicated complicated interactions among EGFR, p38MAPK and c‐Myc in pemphigus vulgaris pathology.     

Internalization of constitutive desmogleins with the subsequent induction of desmoglein 2 in pemphigus lesions

Acantholytic blisters in pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are caused by a dissociation of desmosomes mediated by autoantibodies against desmoglein (Dsg) 3 and Dsg 1, respectively. The blistering occurs at the suprabasilar level in PV and at the subcorneal level in PF, which corresponds to the distribution of target antigens in the epidermis: there is a more prominent expression of Dsg 1 in the upper layer, whereas Dsg 3 is more prominent in the lower layer. To elucidate the histogenesis of acantholysis, we studied the alterations of the desmosomal components and the expression pattern of Dsg isoforms in the lesional and perilesional epidermis of pemphigus patients. The results demonstrated an internalization of the desmosomes in the lower epidermis of PV, PF and pemphigus vegetans. A similar phenomenon was induced in monolayers of keratinocytes cultured with PV sera. However, little change was observed in E-cadherin expression until acantholysis became manifest. This internalization occurred prior to overt acantholysis, and was frequently associated with the induction of Dsg 2 expression in the basilar or lower layers of the epidermis. These findings indicate an alteration of Dsg isoform expression in subclinical pemphigus lesions, which might be related to the characteristic acantholytic patterns: the suprabasilar layer in PV and the upper epidermis in PF.     

Transplacental passage of maternal pemphigus foliaceus autoantibodies induces neonatal pemphigus

The association of maternal pemphigus foliaceus (PF) with neonatal PF is rare and may be secondary to transplacental passage of PF autoantibodies. We describe a 25-year-old patient with PF who was delivered of two consecutive babies, one with classic skin lesions of PF and another that was normal. The neonate with PF was born when the mother had widespread skin disease; the normal newborn was born when the mother was in partial remission. The titers of PF autoantibodies were higher in the mother's serum and the cord serum of the baby with PF than in the mother during partial remission and the unaffected baby. The mother and affected baby had autoantibodies to desmoglein 1. Furthermore, cord blood from the baby with PF induced skin disease when injected into mice. In this case, maternal PF was associated with neonatal PF when the titers of maternal anti-desmoglein 1 autoantibodies were elevated. The cutaneous disease in neonatal PF is due to anti-desmoglein 1 autoantibodies.     

天疱疮发病机制的研究进展

天疱疮是自身免疫引起表皮棘层细胞松解导致的慢性复发性表皮内大疱性皮肤病,典型表现为红斑基础上的疱壁松弛性水疱、糜烂、尼氏征阳性.依据天疱疮的临床表现,分为寻常型、增殖型、落叶型和红斑型天疱疮.天疱疮主要的发病机制是患者存在针对角质形成细胞桥粒芯(糖)蛋白的自身抗体,但棘层松解的详细机制尚不清.近年来,随着对蛋白组学、免疫学和分子生物学技术的发展以及天疱疮发病机制研究的不断深入,发现天疱疮的发病机制中除传统的桥粒芯(糖)蛋白自身抗体外,非桥粒芯(糖)蛋白抗体因素也参与了棘层松解的形成,为天疱疮提供了新的潜在治疗靶位.