Pemphigus Foliaceus Patients Research Articles

Treatment of Refractory Pemphigus with the Anti-CD20 Monoclonal Antibody (Rituximab)

Background: Pemphigus is a severe blistering disorder caused by autoantibodies to desmogleins 1 and 3. Because some patients with pemphigus never enter into remission, new immunosuppressants are warranted. Rituximab is a chimeric monoclonal antibody binding to the CD20 antigen on B cells, which proved to be effective in recalcitrant pemphigus. Objectives: To evaluate the efficacy and safety of rituximab in refractory pemphigus and to investigate its effects on the autoantibody profile. Patients and Methods: Six patients with recalcitrant pemphigus were treated. Rituximab was administered intravenously at a dosage of 375 mg/m² body surface once weekly for 4 weeks. Results: Three pemphigus foliaceus patients and 1 with mucocutaneous pemphigus vulgaris (PV) showed complete response over a follow-up period of up to 18 months. In one oral PV, control of the disease was achieved using pulse therapy with cyclophosphamide following rituximab withdrawal. In one PV with vegetating features, good improvement was obtained after 6 rituximab infusions. All patients tolerated the treatment well. Anti-desmoglein autoantibodies significantly decreased only in pemphigus foliaceus. Conclusions: This study highlights that rituximab is a valuable drug for refractory pemphigus, although the response of mucous membranes and cutaneous folds may be delayed.

Using Desmoglein 1 and 3 Enzyme-linked Immunosorbent Assay as an Adjunct Diagnostic Tool for Pemphigus

Pemphigus is an acquired autoimmune intraepidermal blistering disease that is divided into 2 major subtypes: pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Patients with pemphigus have circulating anti-desmoglein (Dsg)1 and/or anti-Dsg3 IgG autoantibodies. Recently, a novel commercial enzyme-linked immunosorbent assay (ELISA) against Dsg1 and Dsg3 has been established and found to be extremely sensitive and specific. To date, the usefulness of Dsg1 and Dsg3 ELISA in the diagnosis of pemphigus in the Taiwanese population has never been reported. Serum samples were obtained from 143 patients, including 20 patients with PV, 9 patients with PF, 72 patients with bullous pemphigoid, 1 patient with dermatitis herpetiformis and 41 patients with non-autoimmune blistering diseases. They were tested for anti-Dsg1 and anti-Dsg3 reactivity by ELISA. Seventeen of 20 PV sera (85%) exceeded the cut-off value of Dsg3 ELISA, and 9 of 9 PF sera (100%) exceeded the cut-off value of Dsg1 ELISA, while only 1 (0.88%) and 3 (2.6%) of 114 non-pemphigus sera exceeded the cut-off values of Dsg3 and Dsg1 ELISAs, respectively. Thus, the sensitivity and specificity of Dsg3 ELISA were 85% and 99.1%, while the sensitivity and specificity of Dsg1 ELISA were 100% and 97.4%, respectively. The correlation between ELISA scores and disease activity along the time course was examined in 6 PV patients and 1 PF patient, and the result was equivocal. Dsg1 and Dsg3 ELISAs provide a simple, highly sensitive and specific method that can serve as a useful adjunct tool for the initial diagnosis of pemphigus.

Synergistic Pathogenic Effects of Combined Mouse Monoclonal Anti-Desmoglein 3 IgG Antibodies on Pemphigus Vulgaris Blister Formation

Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by anti-desmoglein 3 (Dsg3) IgG antibodies. Previously, we generated an active mouse model for PV by adoptive transfer of splenocytes from immunized or naive Dsg3(-/-) mice. In this study, we isolated 10 anti-Dsg3 IgG mAbs (NAK-series) from PV model mice generated by transfer of naive Dsg3(-/-) splenocytes. We characterized their epitopes using domain-swapped and point-mutated Dsg1/Dsg3 molecules and examined their pathogenic activities in blister formation in three different assays. In a passive transfer model using neonatal mice, eight of 10 NAK mAbs showed pathogenic activity when injected together with half the minimum pathogenic dose of anti-Dsg1 IgG autoantibodies from pemphigus foliaceus (PF) patients. None of the mAbs could induce the PV phenotype when individual hybridoma clones were inoculated by peritoneal injection into adult Rag2(-/-) mice. NAK mAbs displayed a range of potency in an in vitro dissociation assay using primary cultured mouse keratinocytes. Interestingly, when multiple hybridoma clones recognizing different epitopes were inoculated in combination, recipient mice developed the PV phenotype. In vitro dissociation assays confirmed that combined NAK mAbs had synergistic pathogenic effects. These findings indicate that although an individual anti-Dsg3 IgG is not sufficient to cause blistering in adult mice, several together can induce the PV phenotype. These mAbs will provide a valuable tool to investigate the molecular mechanisms of blister formation, mimicking the effects of the polyclonal IgG antibodies found in patients.

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Viewpoint 6

Prolonged Clinical Remission of Patients with Severe Pemphigus upon Rapid Removal of Desmoglein-Reactive Autoantibodies by Immunoadsorption

Background: In pemphigus, loss of epidermal adhesion is induced by binding of circulating autoantibodies to the desmosomal cadherins desmoglein 3 (Dsg3) in pemphigus vulgaris (PV) and desmoglein 1 (Dsg1) in pemphigus foliaceus (PF), respectively. Therapeutic removal of Dsg-reactive autoantibodies by immunoadsorption (IA) has been demonstrated to exert clinical remission of the disease. Objectives: The aim of this intervention study was to evaluate the efficacy and safety of the peptide-based Globaffin^® adsorber system in the treatment of severe pemphigus cases. Patients and Methods: We applied IA in 4 PV and 2 PF patients with severe chronic disease resistant to conventional immunosuppressive therapy. IA was performed on 4 consecutive days, representing 1 treatment cycle, followed by a 4-week treatment-free interval. Serum samples for determining serum IgG and anti-Dsg1/Dsg3 IgG autoantibodies were drawn daily before and after IA, respectively. During follow-up, patients were examined carefully, and laboratory parameters were controlled monthly for up to 1 year. Results: IA led to excellent clinical responses. Skin and mucosal lesions cleared almost completely within weeks. One IA cycle reduced anti-Dsg1 and anti-Dsg3 autoantibodies by an average of 50–70% as determined by ELISA. Conclusions: Using the Globaffin adsorber system, IA represents an effective and safe treatment opportunity in severe and therapy-resistant pemphigus.

Study of desmoglein 1 and 3 antibody levels in relation to disease severity in Indian patients with pemphigus

To conduct a cross-sectional study to compare Dsg1 and Dsg3 antibody levels independently with severity of disease activity in pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Blood samples from 44 patients with pemphigus (PV-38, PF-6) were analyzed using ELISA. The severity of skin and mucosal disease was graded using a score from 0 to 3. A statistically significant correlation between increase in Dsg 3 antibody titres with severity of oral involvement and Dsg 1 titres with severity of skin involvement was found in both PV and PF patients (p < 0.01). However, we were unable to demonstrate a relationship between increased titres of Dsg1 and Dsg 3 antibodies with oral and skin involvement respectively. This study suggests that the severity of skin and oral disease in pemphigus is determined by the quantities of Dsg1 and Dsg3 antibodies respectively.

Enzyme-linked immunosorbent assay using bacterial recombinant proteins of human BP230 as a diagnostic tool for bullous pemphigoid

By immunoblot analyses of normal human epidermal extracts, the 230kDa bullous pemphigoid antigen (BP230) is recognized by most bullous pemphigoid (BP) sera. We produced different recombinant glutathione-S-transferase-fusion proteins, which roughly presented N-terminal domain, central rod domain and C-terminal domain of human BP230. In the present study, we developed an enzyme-linked immunosorbent assay (ELISA) using the recombinant proteins for detection of anti-BP230 IgG antibodies and assessed the usefulness of this assay in conjunction with an anti-BP180 ELISA to establish the diagnosis of BP. Using the bacterial recombinant proteins of N-terminal and C-terminal domains, we developed an ELISA. A receiver-operating-characteristic (ROC) analysis was performed to determine a cut-off value for the BP230 ELISA. By this BP230 ELISA, 173 (72.4%) of 239 BP sera were positive, while only one (1.1%) of 94 sera from pemphigus vulgaris and pemphigus foliaceus patients was positive and all the 109 normal control sera were negative. Thus, the sensitivity and specificity of the BP230 ELISA were 72.4 and 99.5%, respectively. Interestingly, while 54 (84.4%) of 64 BP sera in active stage and 113 (64.6%) of 175 BP sera in remission were positive in BP180 ELISA, 37 (57.8%) of 64 BP sera in active stage and 136 (77.7%) of 175 BP sera in remission were positive in BP230 ELISA. These results indicate that the titer of anti-BP230 antibodies is not related with disease activity in some BP cases. Most significantly, by combining the results of BP230 ELISA and BP180 ELISA, 232 (97.1%) of 239 BP sera were positive. The combination of BP230 ELISA and BP180 ELISA is the highly sensitive method for the diagnosis of BP.

Pemphigus foliaceus IgG causes dissociation of desmoglein 1–containing junctions without blocking desmoglein 1 transinteraction

Autoantibodies against the epidermal desmosomal cadherins desmoglein 1 (Dsg1) and Dsg3 have been shown to cause severe to lethal skin blistering clinically defined as pemphigus foliaceus (PF) and pemphigus vulgaris (PV). It is unknown whether antibody-induced dissociation of keratinocytes is caused by direct inhibition of Dsg1 transinteraction or by secondary cellular responses. Here we show in an in vitro system that IgGs purified from PF patient sera caused cellular dissociation of cultured human keratinocytes as well as significant release of Dsg1-coated microbeads attached to Dsg-containing sites on the keratinocyte cellular surface. However, cell dissociation and bead release induced by PF-IgGs was not caused by direct steric hindrance of Dsg1 transinteraction, as demonstrated by single molecule atomic force measurements and by laser trapping of surface-bound Dsg1-coated microbeads. Rather, our experiments strongly indicate that PF-IgG-mediated dissociation events must involve autoantibody-triggered cellular signaling pathways, resulting in destabilization of Dsg1-based adhesive sites and desmosomes.

Ex vivo analysis of desmoglein 1‐responsive T‐helper (Th) 1 and Th2 cells in patients with pemphigus foliaceus and healthy individuals

Pemphigus foliaceus (PF) is a severe autoimmune bullous disorder, characterized by autoantibodies (autoAb) against desmoglein 1 (Dsg1). As T cells may be critical in the pathology of PF, the aim of the present study was to identify and characterize autoaggressive T-helper cells reactive to Dsg1 in PF patients and healthy individuals. Eight patients with the clinical diagnosis of PF and six HLA class II-matched healthy individuals were examined. By magnetic cell-sorting (MACS) cytokine-secretion assay, Dsg1-responsive T-helper (Th) 1 and Th2 cells were isolated and cloned by limiting dilution. The generated T-cell clones (TCC) were characterized regarding proliferative response, TCR Vbeta-chain usage, and cytokine profile upon in vitro stimulation with Dsg1. Both Dsg1-reactive Th1 and Th2 cells were detected in PF patients and controls at similar frequencies. A total of 15 Th1 and Th2 clones were isolated from patients and 27 TCC from healthy controls. Analysis of TCR Vbeta-chain usage of autoreactive T cells from both groups revealed no predominance of a specific Vbeta chain. Noteworthy, the isolated TCC showed a polarized Th1- or Th2-like phenotype upon in vitro culture and stable expression of Th1 or Th2 cytokines during long-term in vitro culture. In summary, our data demonstrate that T-cell autoreactivity against Dsg1 is not restricted to patients with PF. Moreover, both Th1 and Th2 cells were present in patients and healthy donors, suggesting that the loss of B-cell tolerance against Dsg1 in PF is not exclusively determined by the presence of autoaggressive T cells.

Mechanisms of Blister Formation by Staphylococcal Toxins

Many children suffer from the bacterial skin diseases bullous impetigo and staphylococcal scalded skin syndrome (SSSS). Staphylococcus aureus, which produces exfoliative toxins (ETs), causes these diseases. Recently, it was proven that ETs cleave the cell adhesion molecule desmoglein (Dsg) 1, which plays an important role in maintaining the proper structure and barrier function of the epidermis. Surprisingly, Dsg1 is also the antibody target in the autoimmune disease pemphigus foliaceus. Skin biopsies from pemphigus foliaceus patients show the same pathology as those from bullous impetigo and SSSS patients. The crystal structure of ET suggests that it is a serine protease with an inactive catalytic site, which may become activated when ET binds a specific receptor. This receptor binding is thought to cause a change in conformation that exposes the catalytic site. It has recently been shown that Dsg1 specifically binds and activates ET, which in turn cleaves the bound Dsg1 at only one peptide bond. This process is absolutely dependent on the calcium-dependent conformation of Dsg1. These data suggest that ETs have a very high specificity for human Dsg1, and that S. aureus uses ETs to disrupt the barrier of the human epidermis in order to survive and proliferate on the human body.

Anti-desmoglein 1 antibodies in Tunisian healthy subjects: arguments for the role of environmental factors in the occurrence of Tunisian pemphigus foliaceus.

Pemphigus foliaceus is an autoimmune blistering skin disease mediated by autoantibodies directed against desmoglein 1 and occurs as a sporadic form throughout the world, or as an endemic form called fogo selvagem in Brazil. Healthy subjects living in Brazilian endemic areas produce antidesmoglein 1 antibodies, suggesting the role of environmental factors in the initiation of the autoimmune response. Tunisia was described recently as an endemic area where the disease is characterized by its high rate among young people, especially women. An enzyme-linked immunosorbent assay using recombinant desmoglein 1 as antigen was used to detect antibodies against desmoglein 1 and calibrated with sera from 67 French healthy blood donors, 20 French pemphigus foliaceus patients and patients with other bullous skin diseases. When sera from 179 healthy Tunisian blood donors were tested, 31 (17%) were found positive. The desmoglein 1 binding activity of these 31 sera was confirmed in 10 cases by indirect immunofluorescence analysis and/or immunoblotting using human epidermal extract. Subclass analysis of antidesmoglein 1 antibodies showed that they were almost exclusively of the IgG2 subclass in positive normal sera and of IgG4 subclass in patients with PF. Thus, antibodies against desmoglein 1 are prevalent in normal subjects living in Tunisia which, along with their IgG2 isotype, suggests the role of the environment in the pathogenesis of this endemic type of pemphigus foliaceus and the need for additional factors to switch from a subclinical to a clinical form of the disease.

Dermal dendritic cell number correlates with serum autoantibody titers in Brazilian pemphigus foliaceus patients

Pemphigus foliaceus (PF) is an autoimmune bullous disease endemic in Brazil. Since serum IL-12 is increased in patients with PF and Langerhans cells (LC) produce IL-12, we titrated serum autoantibodies by indirect immunofluorescence, and quantified epidermal dendritic cells, known as LC, and dermal dendritic cells (DC). Biopsies of blistering lesions were obtained from 22 patients, 13 of whom were submitted to biopsy of both injured and of apparently healthy skin. The control groups consisted of skin from 8 cadavers and from 12 women submitted to breast plastic surgery. LC and DC were identified with anti-CD1a antibody and quantified by morphometric analysis. LC number in the lesion and in apparently healthy skin from PF patients was similar to that of both control groups. DC number in the injured skin (median=0.94 DC/mm basement membrane) was higher than that of the cadaver group (median=0.13 DC/mm basement membrane). In the 13 patients with biopsies of both injured and apparently healthy skin, LC and DC were present in larger numbers in the lesion. There was a direct correlation between DC number in the lesion of the PF group and serum autoantibody titers. This correlation was not observed for LC number. The increased number of DC in the lesion, as well as its direct correlation with serum autoantibody titers suggest the participation of DC in the pathogenesis of PF. The relationship between increased DC number and IL-12 in PF needs to be clarified.

Pathogenicity and Epitope Characteristics of Anti-Desmoglein-1 from Pemphigus Foliaceus Patients Expressing Only IgG1 Autoantibodies

Pemphigus foliaceus (PF) is an antibody-mediated autoimmune disorder with IgG1 and IgG4 as the predominant subclasses of autoantibodies against a desmosomal glycoprotein, desmoglein-1 (Dsg1). Previously, we found that the IgG4 anti-Dsg1 autoantibodies only recognize a conformational epitope(s), whereas the IgG1 autoantibodies recognize both conformational and linear epitopes but do not display pathogenicity in the passive transfer animal model. The purpose of this study was to analyze the epitopes recognized by autoanti-bodies from a subset of PF patients who only express anti-Dsg1 of the IgG1 isotype throughout the course of their diseases and to further characterize the pathogenicity of their IgG1 anti-Dsg1. We found that IgG1 auto-antibodies in this subset of PF patients, similar to IgG4 autoantibodies from other PF patients, are able to bind both human and mouse skin and induce the experimental PF in mice. Moreover, a detailed epitope mapping reveals that the conformational epitopes recognized by IgG1 autoantibodies from these PF patients are restricted to the first 161 amino acids of Dsg1, whereas the linear epitopes are spread throughout the entire ectodomain. In conclusion, our study reveals that the isotype of IgG does not necessarily determine the epitopes and pathogenicity of pemphigus autoantibodies.

Apoptosis and p63 expression in the pathogenesis of bullous lesions of endemic pemphigus foliaceus

The physiopathological mechanism involved in the formation of the intraepithelial bullae in pemphigus foliaceus (PF), which is endemic in Brazil, has not been elucidated [1, 2]. Apoptosis has been reported to occur in some dermatoses that may present a positive Nikolsky sign such as PF and graft-versus-host disease (GVHD) [3, 4, 5]. In the first disease, apoptotic keratinocytes are present in the acantholytic region and close to the bullae, but little is known about their role in this dermatosis. Recently, the p53 homologues, p63 and p73, which probably originate from a common ancestor gene, have been described [6]. The p63 gene is located in the 3q27-28 locus and is selectively expressed in the basement membrane of various epithelia, being considered as a stem cell marker for these tissues [7]. However, nothing is known about the role of p63 in bullous dermatoses. The aim of the present study was to determine apoptosis and p63 expression in skin samples from patients with PF. After approval by the Research Ethics Committee of the University Hospital, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, and after obtaining informed consent from each patient, skin biopsies were taken from ten patients with a diagnosis of PF. Clinical criteria were established and active lesions were confirmed by a positive Nikolsky sign and histology. For PF patients, biopsies of injured skin and of apparently healthy skin located at least 3 cm from the active lesion were obtained. The control group (n=5) consisted of skin samples from patients undergoing abdominal plastic surgery. A positive control group for apoptosis (n=5) was included using skin samples from GVHD patients [4]. The biopsies were fixed in formalin, embedded in paraffin and sectioned. For the apoptosis study, the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) technique was performed using an Apoptag kit (Intergen Company, Oxford, UK), developed with 3,3′diaminobenzidine (DAB) (Sigma, St. Louis, Mo.). For p63 expression, immunohistochemistry was performed with a p63 antibody (Santa Cruz Biotechnology, clone 4A4; Santa Cruz, Calif.) at 1:100 dilution, and p63 was identified using the streptavidin-biotin-peroxidase method (Novostain Universal kit, Novocastra, Newcastle upon Tyne, UK), developed with 3-amino-9-ethyl-carbazole (AEC) (Vector Laboratories, Burlingame, Calif.). In the control group, p63 expression was limited to the basal layer of the epidermis (Fig. 1b). Indeed, p63 is essential for the maintenance of a precursor population (stem cells) in various epithelial tissues and may be considered a marker of cell undifferentiation [6, 7]. In these samples, apoptotic keratinocytes were identified in some cells close to the horny layer (Fig. 1a). Apoptotic keratinocytes in Isabela Zuccolotto · Ana Maria Roselino · Leandra Naira Zambelli Ramalho · Sergio Zucoloto

Pemphigus in Korea: clinical manifestations and treatment protocol.

Pemphigus, a rare, chronic blistering disease of the skin and mucous membranes with severe morbidity and occasional mortality, is the most common autoimmune bullous disease in Korea. The purpose of this study was to evaluate the clinical features and propose a treatment strategy for patients with pemphigus. A retrospective analysis was conducted of 51 pemphigus patients seen between 1993 and 2001. Pemphigus vulgaris (PV) was the most common type with 32 cases, followed by 19 cases of pemphigus foliaceus (PF). The male to female ratio was 1:1.3, with females predominating, particularly among PV patients (PV, 1:1.5; PF, 1:1.1). The average ages at onset of PV and PF were 44.3 and 51.0 years old, respectively. Mucosal involvement was noted in 27 cases (84.4%) of PV but in only 3 cases (15.8%) of PF. Most patients initially received relatively low to intermediate doses (0.3-1.0 mg/kg/day) of prednisolone, and 23 (71.9%) PV patients and 10 (52.6%) PF patients also received immunosuppressive agents. Oral prednisolone and azathioprine (100 mg/day) formed the mainstay of treatment for our patients (47.1%). At the time of writing, 25.5% (13/51) of patients are in complete remission, and 72.5% (37/51) are undergoing maintenance therapy. One patient died due to sepsis during the treatment. For the treatment of pemphigus, a course of the lowest possible corticosteroid dosage in combination with immunosuppressive agents appears to be effective and less toxic than a high corticosteroid dosage.

Paraneoplastic pemphigus is associated with the DRB1∗03 allele

Pemphigus is a group of autoimmune blistering diseases caused by autoantibodies directed against keratinocyte adhesion molecules. Pemphigus vulgaris (PV) and pemphigus foliaceus (PF), in which autoantibodies bind, respectively, to desmoglein 3 and desmoglein 1, are strongly associated with HLA-class II DR4 and DR14 alleles. In paraneoplastic pemphigus (PNP), a rare variant associated with neoplasia, autoantibodies target proteins of the plakin family in addition to desmogleins 1 and 3. The presence of anti-desmoglein antibodies in all types of pemphigus raises the question of common molecular mechanisms of susceptibility, particularly similar MHC-class II allele associations, in the different forms of the disease. HLA-DRB1 typing was performed in 13 PNP patients and results were compared to those obtained from 84 healthy controls, 37 PV and 31 PF patients. Our data demonstrate a significant association of PNP with HLA-DRB1∗03 allele which was found in 61.5% of the patients, whereas DRB1∗04 and DRB1∗14 appear not to be involved in PNP susceptibility. Therefore, the HLA-genetic background of PNP differs from that of other types of pemphigus, which suggests that distinct mechanism(s) initiate(s) the immunological response in this form of pemphigus.

Serum lipids of pemphigus foliaceus patients on long-term glucocorticoid therapy.

Endemic pemphigus foliaceus, and long-term corticotherapy may affect serum lipid levels. The aim of this study was to compare serum lipids of pemphigus foliaceus patients on glucocorticoid therapy to a healthy control group. Fifteen patients receiving prednisone (0.33 +/- 0.22 mg/kg) for at least 12 months and 15 controls were submitted to 48-h food intake records, anthropometry, and biochemical measurements. Data were compared by chi2, Mann-Whitney and Student "t" tests. The groups were matched for gender, age, weight, body mass index, arm circumference and triceps skin fold. No differences were observed in relation to energy, fat, protein and carbohydrate daily intakes, total cholesterol, HDL, LDL, uric acid, and serum creatinine levels. Pemphigus foliaceus patients had higher triglyceride [159 (64-371) vs. 100 (45-133) mg/dl], VLDL [32 (13-74) vs. 20 (9-114) mg/dl] and ESR [44 (9-87) vs. 7 (1-30) mm/h] levels than controls, probably due to metabolic effects of inflammatory disease and corticotherapy.

T Cell Receptor β Chain Gene Usage in Endemic Pemphigus Foliaceus (Fogo Selvagem)

The trimolecular complex comprised of the major histocompatibility complex, peptide antigen, and the T cell receptor is a requisite for T cell activation in normal and autoimmune responses. T cell receptor analysis is critical to further our understanding regarding mechanisms of T cell epitope selection and autoimmune initiation and progression and may help to identify targets for immunotherapy. Pemphigus foliaceus is an autoimmune blistering skin disease characterized by intraepidermal blisters and circulating autoantibodies directed against desmoglein 1, a 160 kDa transmembrane desmosomal molecule expressed in keratinocytes. As tissue damage is mediated by anti-desmoglein 1 antibodies, an initial T cell response is a likely requirement for autoantibody generation in this disease. To elucidate the role of pathogenic T cells in autoimmunity further, we have directly characterized the T cell receptor of T cells derived from pemphigus foliaceus patients. Complementary DNA was isolated from 17 desmoglein 1 specific T cell clones generated from pemphigus foliaceus patients by clonal expansion in vitro. To analyze the T cell repertoire, a panel of primers, collectively specific for the known human T cell receptor beta variable region (TCRBV) families were paired with a constant region primer to polymerase chain reaction to amplify one distinct T cell receptor beta variable region allele for each T cell clone studied. Polymerase chain reaction products were sequenced to determine exact beta chain gene usage. In the 17 clones tested, 10 distinct T cell receptor beta variable region usages and nine T cell receptor beta joining gene segment usages were identified. Furthermore, T cell receptor beta variable region and beta joining usage did not appear to be random, but oligoclonal in nature, with some preference shown for T cell receptor beta variable region 5S1 and T cell receptor BJ2S5.

Epistasis between DSG1 and HLA class II genes in pemphigus foliaceus.

Pemphigus foliaceus (PF) is a rare and severe cutaneous autoimmune disease caused by autoantibodies directed against desmoglein 1 (DSG1), a desmosomal adhesion glycoprotein. We previously showed that the DSG1 gene is polymorphic and that a coding synonymous T/C single nucleotide polymorphism at position 809 is associated with PF. To determine whether the disease occurred as a consequence of complex genetic interactions, we simultaneously examined the contribution of major histocompatibility complex (MHC) class II and DSG1 polymorphisms to PF susceptibility. Our analysis performed in 31 PF patients and 84 healthy controls first confirmed the previously reported common DRB1*04 and DRB1*14 genetic background in PF and individualized DRB1*0102, DRB1*0402 and DRB1*0406, and DRB1*1404 as susceptibility MHC class II alleles in French Caucasian PF patients. It also showed that the C/C(809) genotype was associated with PF. Combined analysis of HLA class II and DSG1 polymorphisms with several distinct statistical methods including logistic regression, showed that the DRB1*04 allele and the C/C(809) genotype interact to confer a higher susceptibility to PF. These data demonstrate the role of epistasis between individual genes in PF susceptibility and illustrate the genetic complexity of organ-specific autoimmune diseases.

A polymorphic variant of the gene coding desmoglein 1, the target autoantigen of pemphigus foliaceus, is associated with the disease.

Two polymorphic markers were identified on the desmoglein 1 gene which encodes the autoantigen targeted by pathogenic antibodies in pemphigus foliaceus (PF), a cutaneous autoimmune blistering disease. The first marker, made of a variant haplotype of five mis-sense mutations located on the part of the gene encoding the fourth and fifth extracellular domains of the protein, is not associated with the disease. The second marker consists of a single silent T to C transition at position 809 and was found to be significantly more frequent (P = 0.015) in Caucasian PF patients (n = 36) than in controls (n = 98). Thus, pemphigus foliaceus constitutes another example of autoimmune disease in which the autoantigen polymorphism contributes to disease susceptibility.