Direct characterization of human T cells in pemphigus vulgaris reveals elevated autoantigen-specific Th2 activity in association with active disease

Pemphigus vulgaris (PV) is a blistering skin disorder mediated by autoantibodies targeting the epidermal adhesion molecule desmoglein 3 (Dsg3). As Th2-associated cytokines are necessary for directing antibody production, it is hypothesized that Dsg3-specific Th2 activity is associated with active disease. We used cell-surface-matrix technology in combination with flow cytometry to characterize the Dsg3-reactive T-cell population using peripheral blood mononucleocytes sampled from PV patients stratified by active (n = 9) or remittent disease (n = 6), and healthy human leucocyte antigen-matched controls (n = 5). We evaluated interferon-gamma-producing CD4+ cells (Th1) and interleukin (IL)-10- or IL-4-producing CD4+ cells (Th2). The mean frequency of Th2 CD4+ T cells was significantly elevated for five of nine PV patients with active disease. No significant Th2 responses were detected for patients with remittent disease or controls. There was a significant association of Th2 activity with active disease compared with remittent and control groups (P = 0.026 and P =0.012, respectively), and Th2 activity was significantly correlated with anti-Dsg3 IgG titre (P = 0.044). One patient with remittent disease converted from a Th2-negative to a Th2-positive response with the initiation of disease activity. An antigen-specific CD4- lymphocyte response was detected in five PV patients (36%), and was shown to correlate closely with the CD8+ population. These results are consistent with the hypothesis that Th2 response directs autoantibody production and is therefore associated with disease activity in PV.     

Autoantibodies against desmocollins in European patients with pemphigus

Background. Autoimmune bullous disorders of the pemphigus group are characterized by autoantibodies targeting desmoglein (Dsg)1, Dsg3 and Dsg4 and occasionally, desmocollin (Dsc)1, Dsc2 and Dsc3. Both Dsg and Dsc are components of desmosomal adhesion complexes. Aim. To investigate the presence of IgG and IgA autoantibodies against Dsc1, Dsc2 and Dsc3 in a cohort of patients with bullous disorders. Methods. IgG and IgA autoantibodies against Dsc1, Dsc2 and Dsc3 were investigated by ELISA and immunoblotting analysis in a cohort of European patients with pemphigus vulgaris (PV; n = 74), IgA pemphigus (n = 3), paraneoplastic pemphigus (PNP; n = 3) and two cases of atypical pemphigus (n = 2). Results. Of the two cases with atypical pemphigus, one showed IgA reactivity against Dsc1 and Dsc3 and weak reactivity against Dsc2, and the other showed both IgG and IgA reactivity against Dsc1. One patient with IgA pemphigus had IgA autoantibodies against Dsc1, Dsc2 and Dsg1, and one patient with PNP had IgG reactivity against with Dsc3. In contrast, all the PV sera showed IgG reactivity against Dsg3 but not against Dsc1–3. Thus, IgG and IgA reactivity against Dsc was restricted to cases of PNP, IgA pemphigus and atypical pemphigus. Conclusions. These findings support the concept that desmocollins are not important autoantigens in PV.     

IgG reactivity against non-conformational NH-terminal epitopes of the desmoglein 3 ectodomain relates to clinical activity and phenotype of pemphigus vulgaris

Pemphigus vulgaris (PV) is an autoimmune disease caused by immunoglobulin G (IgG) autoantibodies against the desmosomal adhesion molecules, desmoglein (Dsg)3 and Dsg1. The aim of the study was to relate IgG reactivity of 123 PV sera and 40 control sera against NH(2)-terminal non-conformational epitopes of Dsg3 and Dsg1 with disease activity and clinical phenotype by enzyme-linked immunosorbent assay. The results show that (i) the overall reactivity and the titres of IgG reactive with the Dsg3 ectodomain, Dsg3(1-566), significantly correlated with the disease activity of the PV patients; (ii) IgG reactivity against the NH(2)-terminus of Dsg3, Dsg3(1-161), was associated with active PV while there was no direct correlation between the IgG titres and the disease activity; (iii) IgG reactivity against the NH(2)-terminus of Dsg3, Dsg3(1-161), was associated with mucosal and mucocutaneous PV; (iv) IgG titres against a small stretch of the NH(2)-terminus of Dsg3, Dsg3(25-88), were associated with active PV; and (v) IgG in the PV sera detected non-conformational epitopes in addition to the previously identified conformation-dependent epitopes of the Dsg3 and Dsg1 ectodomains.     

Predominant IgG4 subclass in autoantibodies of pemphigus vulgaris and foliaceus

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are autoimmune skin diseases caused by autoantibodies against desmoglein (Dsg) 3 and Dsg1. We have previously developed ELISAs using recombinant Dsg3 and Dsg1 expressed by baculovirus as a diagnostic tool for pemphigus. In this study, we determined the frequency of coexistence of IgA class as well as distribution of IgG subclass. Two out of 49 PV and PF sera tested had anti-Dsg1 IgA in addition to anti-Dsg1 IgG. Interestingly, one of them showed prominent pustular formation. Among IgG subclass, IgG4 was predominant and found in all of the 30 PV and 19 PF sera tested, followed by IgG1, detected in 25 out of 30 PV and 12 out of 19 PF sera. Even though IgG2 and IgG3 were detected in 13 and one PV and 6 and 4 PF sera, respectively, the ELISA titers had barely exceeded the cutoff value in most of the cases. There was no IgG subclass shift during the course of the disease in seven cases examined. These findings indicate that IgG4 subclass is the predominant autoantibodies in both PV and PF, while IgG1 is also frequently found.     

Coexistence of IgA antibodies to desmogleins 1 and 3 in pemphigus vulgaris, pemphigus foliaceus and paraneoplastic pemphigus

BACKGROUND: Pemphigus is a bullous mucocutaneous autoimmune disease characterized by IgG autoantibodies to desmoglein (Dsg) 1 and/or Dsg3. Occasionally direct immunofluorescence of pemphigus skin reveals IgA depositions with an intraepidermal intercellular pattern in addition to the IgG deposition. OBJECTIVES: To investigate if pemphigus patients, in addition to having IgG autoantibodies, also generate IgA antibodies to Dsg1 and/or Dsg3. PATIENTS/METHODS: Sera of 100 pemphigus patients and 36 bullous pemphigoid controls were tested by IgA enzyme-linked immunosorbent assay (ELISA) to the recombinant extracellular domains of Dsg1 and Dsg3. The patients were selected on clinical grounds and positive IgG ELISA index values for Dsg1 and/or Dsg3. They were divided into four groups: patients having IgG to only Dsg1 (n=34), patients having IgG to both Dsg1 and Dsg3 (n=31), patients having IgG to only Dsg3 (n=27) and patients who had paraneoplastic pemphigus (PNP) (n=8). RESULTS: IgA antibodies to Dsg1 were found in 13 (38%) of the patients with IgG to Dsg1, in five (16%) of the patients with IgG to both Dsg1 and Dsg3, in four (15%) of the patients with IgG to Dsg3 and in none of the PNP patients. IgA antibodies to Dsg3 were found in one (3%) of the patients with IgG to Dsg1, in 18 (58%) of the patients with IgG to both Dsg1 and 3, in 18 (67%) of the patients with IgG to Dsg3, and in four (50%) of the PNP patients. Immunofluorescence analysis demonstrated intraepidermal intercellular staining IgA antibodies in serum and intercellular IgA deposits in skin of IgA ELISA-positive patients, although to a lesser extent than by ELISA. CONCLUSIONS: This study shows that in a considerable number of supposedly IgG-mediated pemphigus patients IgA to Dsg1 and Dsg3 is also present. In most cases the antigen specificity of the IgA follows the antigen specificity of the IgG, although in a small number of cases IgA is present against the Dsg not recognized by IgG.     

E-cadherin is an additional immunological target for pemphigus autoantibodies

Pemphigus foliaceus (PF) and pemphigus vulgaris (PV) are autoimmune blistering diseases characterized by autoantibodies against desmoglein (Dsg)1 and Dsg3, respectively. The role of classical cadherins as immunological targets of pemphigus autoantibodies is unknown. In this study, we tested the reactivity of sera from patients with PF, Fogo Selvagem (FS), and PV by immunoprecipitation coupled with immunoblotting (IP-IB) and ELISA techniques using a baculovirus-expressed ectodomain of E-cadherin. By IP-IB, anti-E-cadherin reactivity was detected in all tested sera of PF (n=13) and FS (n=15) patients, and in 79% of mucocutaneous-type PV patients (n=33), but in none of the mucosal-type PV patients (n=7). By ELISA, anti-E-cadherin IgG was detected in most pemphigus sera that produced strong E-cadherin bands by IP-IB. The immunoreactivity of PF/FS sera with E-cadherin was also demonstrated by IP-IB using human epidermal extracts. However, immunofluorescence staining of A431DE cells (E-cadherin positive, Dsg1 negative) with pemphigus sera showed negative results. Immunoadsorption and competitive ELISA analysis suggest that most of the anti-E-cadherin antibodies cross-react with Dsg1, whereas others may represent independent antibodies that do not cross-react with Dsg1. The functional relevance of these anti-E-cadherin IgG autoantibodies detected in these pemphigus sera remains to be defined.     

IgG against extracellular subdomains of desmoglein 3 relates to clinical phenotype of pemphigus vulgaris

Abstract:  Pemphigus vulgaris (PV) is associated with autoantibodies against desmoglein (Dsg) 3 inducing epidermal loss of adhesion. The major pathogenic epitopes of Dsg3 are presumably dependent of their conformation. The aim of this study was to characterize the IgG reactivity of sera from a cohort of clinically well-characterized PV patients against presumably non-conformational subdomains of the Dsg3 ectodomain including recently described NH₂-terminal immunodominant epitopes. By ELISA, IgG reactivity against distinct subdomains of Dsg3 was related to disease activity and the clinical phenotype of PV patients. Our findings suggest that (i) autoantibody from PV sera react with non-conformational epitopes of Dsg3; (ii) IgG reactivity against the NH₂-terminus and the extracellular domains (EC) 2-4 of Dsg3 was associated with active PV, while IgG titres were not strictly correlated with disease activity and (iii) IgG reactivity against the EC1-4 was associated with mucosal dominant PV and was decreased in cutaneous dominant PV. The findings may help to define more refined serological disease markers of PV.     

Anti-desmoglein IgG autoantibodies in patients with pemphigus in remission

Background   Desmoglein (Dsg) enzyme-linked immunosorbent assay (ELISA) is a highly sensitive and specific method to detect anti-Dsg3 and anti-Dsg1 IgG autoantibodies in pemphigus vulgaris (PV) and pemphigus foliaceus (PF), respectively. Whereas ELISA index values fluctuate in parallel with disease activity, ELISA positivity during clinical remission has been observed.
Objective   To determine the prevalence of positive Dsg ELISA index values during clinical remission. To ascertain how positive Dsg ELISA scores during remission compare with those during active disease.
Methods   Dsg ELISA was performed on serum samples of PV and PF patients taken during remission (lesion-free ≥ 3 months on ≤ 15 mg or ≤ 5 mg/day prednisolone) and active disease. We used a modified ELISA protocol with optimal serum dilutions in sera with very high initial index values, as we previously described.
Results   When remission was defined as no eruption ≥ 3 months with ≤ 15 mg/day prednisolone, 20 of 43 PV patients (46.5%) and 4 of 12 PF patients (33.3%) showed Dsg3 and Dsg1 ELISA positivity, respectively. With ≤ 5 mg/day, 6 of 17 PV (35.3%) and 1 of 6 PF patients (16.7%) showed Dsg3 and Dsg1 ELISA positivity, respectively. The index value of each ELISA-positive remission serum was consistently lower than that of its corresponding active disease serum. We observed consistent correlation between ELISA index values and indirect immunofluorescence titres.
Conclusions   Circulating anti-Dsg IgG autoantibodies are found in a considerable percentage of pemphigus patients in remission, who have high levels of antibody production during active stages.     

In vitro keratinocyte dissociation assay for evaluation of the pathogenicity of anti-desmoglein 3 IgG autoantibodies in pemphigus vulgaris

Patients with pemphigus vulgaris (PV) have circulating anti-desmoglein (Dsg) 3 immunoglobulin G (IgG) autoantibodies that induce blister formation. We developed an in vitro quantitative assay to evaluate the pathogenic strength of anti-Dsg3 IgG autoantibodies in blister formation. To obtain intercellular adhesion mediated dominantly by Dsg3, we used primary cultured normal human keratinocytes expressing low level of Dsg2 in the presence of exfoliative toxin A that specifically digests Dsg1. After incubation with various antibodies, monolayers released by dispase were subjected to mechanical stress by pipetting, and the number of cell fragments were counted. When anti-Dsg3 monoclonal antibodies (mAb) obtained from pemphigus model mice were tested, pathogenic AK23 mAb yielded significantly higher number of cell fragments than AK7 or AK20 non-pathogenic mAb. Dissociation scores, defined with AK23 mAb as the positive control, were significantly higher with active stage PV sera (n=10, 77.4+/-21.4) than controls (n=11, 16.0+/-9.6; p=0.003). When pair sera obtained from 6 PV patients in active stage and in remission were compared, the dissociation scores reflected well the disease activity as those in active stage were four to 17 times higher than those in remission. When sera from different patients showing similar ELISA scores but different clinical severity were tested (n=6), the dissociation scores with sera from severe disease activity were significantly higher than those with sera in remission. These findings indicate that this dissociation assay will provide a simple and objective biological method to measure the pathogenic strength of pemphigus autoantibodies.     

Analysis of the T cells that are potentially involved in autoantibody production in pemphigus vulgaris

Pemphigus vulgaris (PV) is a classical example of an antibody-mediated autoimmune disease of the skin. Direct evidence exists that autoantibodies against the desmosomal adhesion molecule, desmoglein 3 (Dsg3), are critical in the pathogenesis of this disease. The transfer of serum IgG antibodies reactive with Dsg3 into newborn mice induces a bullous skin disease resembling PV. Autoreactive T cell responses to Dsg3 may be critical in the pathogenesis of PV because 1) antibody production generally requires T cell help, 2) the involvement of CD4+ T lymphocytes in PV has been suggested by the strong association with distinct HLA class II alleles, and 3) T cell recognition of epitopes of Dsg3 may be crucial for the initiation and perpetuation of the production of Dsg3-specific autoantibodies by B cells. We and others have identified autoreactive T cells recognizing distinct epitopes of the extracellular portion of Dsg3 in PV patients. These autoreactive CD4+ T cells preferentially produced TH2 cytokines such as IL-4, and IL-10. Autoantibodies of the TH2-dependent IgG4 subtype are preferentially seen in active stages of PV disease, while autoantibodies of the TH1-dependent IgG1 subclass are predominant upon remission of PV. Healthy individuals who carried HLA class II alleles similar or identical to those found to be highly prevalent in PV also developed autoreactive T cell responses to Dsg3. Autoreactive T cells from PV patients produced both TH1 and TH2 cytokines; autoreactive T cells from normals produced TH0 cytokines. These observations suggest that Dsg3-specific T cells may provide targets to eventually modulate the T cell-dependent production of pathogenic autoantibodies in PV.     

Circulating IgA and IgE autoantibodies in antilaminin‐332 mucous membrane pemphigoid

Background Antilaminin‐332 mucous membrane pemphigoid (MMP) is a chronic autoimmune bullous disease that is often associated with internal malignancy. IgG autoantibodies against laminin‐332 in patients with MMP are well documented; however, IgA and IgE autoantibodies against laminin‐332 have not yet been described. Objectives To characterize IgA and IgE autoantibodies binding to laminin‐332 in sera from patients with antilaminin‐332 MMP. Methods Sera and skin samples from four patients who met the following criteria were used: (i) subepidermal blistering lesions present on the mucous membranes; (ii) in vivo deposition of IgG along the epidermal basement membrane zone of sampled skin; (iii) circulating IgG antibasement membrane zone antibodies that react with the dermal side of salt‐split normal human skin; and (iv) circulating IgG autoantibodies that do not show positivity against type VII collagen or 200‐kDa protein (p200 antigen) in immunoblot analysis using dermal extracts. Circulating IgG/IgA/IgE class autoantibodies against laminin‐332 were determined by immunoblotting. Results Circulating IgG autoantibodies against the γ2, α3/γ2, α3 and α3/β3/γ2 subunits of laminin‐332 were demonstrated in sera from four patients, respectively. Serum from one of the four patients showed IgA reactivity with the α3/β3/γ2 subunits of laminin‐332. Serum from one of the four patients showed IgE reactivity with the γ2 subunit of laminin‐332. The control sera failed to display IgG/IgA/IgE reactivity to laminin‐332. Conclusions In addition to IgG autoantibodies, circulating IgA and IgE autoantibodies against laminin‐332 are detectable in a subset of patients with antilaminin‐332 MMP.     

Diagnosis of pemphigus by ELISA: a critical evaluation of two ELISAs for the detection of antibodies to the major pemphigus antigens, desmoglein 1 and 3

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are characterized by autoantibodies to the desmosomal glycoproteins desmoglein 3 (Dsg 3) and Dsg 1 (Dsg 1), respectively. In this study, two enzyme-linked immunosorbent assays (ELISA) which detect IgG autoantibodies to Dsg 1 and Dsg 3 have been evaluated. A total of 317 normal and disease controls, 82 patients with PV and 25 with PF were studied. The Dsg 3 ELISA was positive in all 34 patients with untreated PV and the Dsg 1 ELISA was positive in all 10 with untreated PF. When patients undergoing treatment were included, the sensitivities fell to 95% and 92%, respectively, but still compared favourably to the sensitivity of indirect immunofluorescence which was 79% in PV and 84% in PF. All PF sera were negative in the Dsg 3 ELISA and the specificity of both assays was 98% or greater. Large numbers of samples could be analysed simultaneously over a relatively short time period. The Dsg 1 and Dsg 3 ELISAs also provided objective, quantitative, reproducible data which allowed differentiation of PV from PF and in view of these advantages, they are likely to become a routine technique in diagnostic laboratories.     

Novel ELISA systems for antibodies to desmoglein 1 and 3: correlation of disease activity with serum autoantibody levels in individual pemphigus patients

Please cite this paper as: Novel ELISA systems for antibodies to desmoglein 1 and 3: correlation of disease activity with serum autoantibody levels in individual pemphigus patients. Experimental Dermatology 2010; 19: 458–463. Abstract: Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are intraepidermal blistering skin diseases. PV is characterised by autoantibodies directed against desmoglein (Dsg) 3 and in patients with the mucocutaneous variant also against Dsg 1, whereas in PF, only Dsg 1 is targeted. Here, ectodomains of Dsg 3 and Dsg 1 were recombinantly expressed in a human cell line (HEK293) and applied as authentic solid phases in ELISA test systems. Autoantibodies against Dsg 3 and/or Dsg 1 could be detected in 71 (100%) of 71 PV sera and against Dsg 1 in 48 (96%) of 50 PF sera. Control sera showed reactivity with Dsg 3 and Dsg 1 in 0.2% and 0.7%, respectively, of 401 healthy blood donors and in 2.1% of 48 randomly selected patients with bullous pemphigoid. No reactivity with Dsg 1 and 3 was detected in 21 patients with linear IgA disease. For both pemphigus variants, a statistically significant correlation between clinical severity and autoantibody levels was observed as demonstrated for 10 PV and 5 PF patients. In conclusion, the use of the ectodomains of Dsg 3 and 1 as target antigens expressed in a human cell line resulted in sensitive and specific ELISA systems for both diagnosis and monitoring of PV and PF.     

Conformational epitope mapping and IgG subclass distribution of desmoglein 3 in paraneoplastic pemphigus

BACKGROUND: Pemphigus vulgaris (PV) shows autoimmune reaction against desmoglein 3 (Dsg3), whereas paraneoplastic pemphigus (PNP) shows autoimmune reaction against Dsg3 as well as numerous members of the plakin family. It has been demonstrated that in PV, dominant epitopes reside in N-terminal adhesive regions of Dsg3 and that the dominant IgG subclass against Dsg3 is IgG4. OBJECTIVE: We attempted to map conformational epitopes and analyze IgG subclass distribution against Dsg3 in PNP. METHOD: Epitopes on Dsg3 for circulating IgG autoantibodies from PNP (n = 22) were studied with competition enzyme-linked immunosorbent assay (ELISA) using domain-swapped molecules between Dsg3 and Dsg1 and were compared with those for IgG autoantibodies from PV (n = 22). IgG subclass distribution was analyzed with PNP serum by Dsg3 ELISA (n = 17). RESULTS: Epitopes on Dsg3 in PNP were distributed more broadly through the extracellular domain of Dsg3 than were those in PV, although the N-terminal extracellular domains of Dsg3 were more frequently recognized than the C-terminal extracellular domains. IgG subclass in PNP was IgG1 and IgG2 dominant. CONCLUSION: Autoimmune response against Dsg3 in PNP is more diversified than that in PV, a finding that suggests PNP and PV have different pathophysiologic mechanisms for triggering production of anti-Dsg3 IgG.     

Two cases of erosive oral lichen planus with autoantibodies to desmoglein 3

Oral lichen planus (OLP) is a chronic inflammatory disorder of the oral mucosa of unknown etiology. Clinically, the erosive type of OLP (erosive OLP) can show features similar to those of pemphigus vulgaris (PV), an autoimmune blistering disorder in which desmoglein (Dsg)3 is targeted. In addition to clinical and histopathological findings, immunological studies, including direct immunofluorescence (IF), indirect IF and enzyme‐linked immunosorbent assay (ELISA) that detect autoantibodies to Dsg3, are helpful in differentiating erosive OLP from PV. Here, we show two cases of erosive OLP with autoantibodies to Dsg3. Patient 1 was a 68‐year‐old woman with chronic erosions of the oral mucosa, in which elevated levels of immunoglobulin (Ig)G autoantibodies to Dsg1 and Dsg3 were detected by ELISA. Patient 2 was an 85‐year‐old woman with white striae with erosions on the lateral sides of the buccal mucosa with elevated levels of IgG autoantibodies to Dsg3 detected by ELISA. Histopathological findings from both cases showed lichenoid dermatitis, and both direct and indirect IF showed no tissue‐bound IgG autoantibodies. From these findings, the diagnosis of erosive OLP was made. Immunological assays revealed both cases to have IgG‐directing calcium‐independent linear epitopes on Dsg3, which are suggestive of non‐pathogenic autoantibodies. In addition, autoantibodies to Dsg3 in patient 2 reacted with a prosequence‐possessing precursor form of Dsg3 but not with the mature form of the molecule. The present study suggests that erosive OLP may develop anti‐Dsg3 autoantibodies, which should be carefully assessed.     

Usefulness of enzyme-linked immunosorbent assay using recombinant desmogleins 1 and 3 for serodiagnosis of pemphigus

Pemphigus is an autoimmune blistering disease with two major subtypes, pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Patients with pemphigus have circulating antidesmoglein (Dsg)1 and/or anti-Dsg3 IgG autoantibodies. We have previously developed enzyme-linked immunosorbent assays (ELISAs) using recombinant Dsg1 and Dsg3 expressed by baculovirus as a diagnostic tool for pemphigus. The purpose of this study was to evaluate the practical application of these ELISAs for clinical use with a large number of serum samples. We used 81 PV sera, 48 PF sera, 114 bullous pemphigoid (BP) sera, 124 collagen disease sera, nine sera of other non-pemphigus bullous diseases and 179 normal control sera. A cut-off value was determined by receiver-operating-characteristic plots. Forty-seven of 48 PF sera (97.9%) were positive in the Dsg1 ELISA and 79 of 81 PV sera (97.5%) were positive in the Dsg3 ELISA, while only two (1. 1%) and four (2.2%) of 179 normal sera were positive in Dsg1 and Dsg3 ELISAs, respectively. However, some disease control sera of BP and collagen diseases exceeded the cut-off value. Introduction of a grey zone helped to decrease the number of these false-positive sera. Furthermore, in three patients studied, the respective Dsg1 and Dsg3 ELISA scores showed parallel fluctuation with the disease activity along the time course. We conclude that Dsg1 and Dsg3 ELISAs provide a simple, sensitive and highly specific assay for the diagnosis of patients with PV and PF and that these ELISAs may be a valuable tool to monitor the disease activity. We also propose diagnostic criteria for pemphigus based on ELISA reactivity: if a serum is positive against Dsg3 it indicates a diagnosis of PV, regardless of reactivity against Dsg1; if a serum is negative for Dsg3 and positive for Dsg1, it indicates a diagnosis of PF.     

A novel lateral flow immunoassay for the rapid detection of anti‐Dsg3 IgG serum autoantibodies in pemphigus vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease of the skin and mucous membranes. As autoantibodies play an essential role in the disease pathogenesis, the serological detection of anti‐desmoglein 3 IgG represents a central tool in the diagnosis of the disease. In this study, we show the validation of a novel lateral flow immunoassay (LFIA) which rapidly detects anti‐desmoglein 3 (Dsg3) IgG in human serum. In contrast to other diagnostic procedures, the assay is compact and simple to perform and delivers a fast ”yes” or “no” answer within 10 minutes without additional hardware requirements for test evaluation. For validation, a blinded collection of 200 sera including 100 sera from 14 PV patients, 75 sera from 24 bullous pemphigoid patients and 25 sera from 6 patients with pemphigus foliaceus collected at different time points during disease was used. Presence or non‐presence of anti‐Dsg3 IgG within sera was confirmed using a commercially available Dsg3‐ELISA. For qualitative evaluation, Dsg3‐LFIA test results were assessed by two independent groups of human observers. Furthermore, quantitative evaluation using POCScan reader was applied. The Dsg3‐LFIA demonstrated reliable test results with a sensitivity and specificity of 78.1% and 97.1%, respectively. Test results from POCScan and human observers showed a substantial agreement. The Dsg3‐LFIA represents a new diagnostic tool for the immediate and reliable detection of anti‐desmoglein 3 serum IgG autoantibodies that does not require additional hardware. Further prospective trials are warranted to validate the Dsg3 LFIA in pemphigus.     

Immunoreactivity against intracellular domains of desmogleins in pemphigus

In pemphigus vulgaris (PV) and pemphigus foliaceus (PF), most of the autoantibodies are directed against the extracellular domains of desmoglein 1 (Dsg1) or Dsg3, and those antibodies are proved to play a pathogenic role in blister formation in the skin and mucous membranes. However, some pemphigus sera have been reported to react with the intracellular domains of these antigens. In the present study, we examined the reactivity of the sera from various types of pemphigus with recombinant proteins of extracellular and intracellular domains of human Dsg1 and Dsg3 by immunoblot analysis. We produced the entire extracellular domain of Dsg1 or Dsg3 fused with mouse IgG2a by baculovirus expression. We prepared the intracellular domain of Dsg1 or Dsg3 fused with glutathione-S-transferase by bacterial expression. All of the 31 PV sera reacted with the extracellular domain of Dsg3 and four reacted with the intracellular domain. Six out of 19 PF sera reacted with the extracellular domain of Dsg1 and five reacted with the intracellular domain. In addition, some sera of Brazilian PF patients or cases with mixed features of PV and PF also reacted with the intracellular domains of Dsg1 or Dsg3. Although the frequency was low, some sera did react with the intracellular domain of Dsgs.     

Genetic characterization of human Dsg3-specific B cells isolated by flow cytometry from the peripheral blood of patients with pemphigus vulgaris

BACKGROUND: Pemphigus vulgaris (PV) is an autoimmune bullous disease caused by anti-desmoglein 3 (Dsg3) IgG autoantibodies; however, the Dsg3-specific B cells that produce anti-Dsg3 IgG are not well characterized. OBJECTIVES: Our aims were to develop a flow cytometric method for the isolation of Dsg3-specific B cells from the peripheral blood of patients with active PV and to identify the variable regions within their heavy- and light-chain immunoglobulin genes. METHODS: Dsg3-specific B cells were isolated as CD3(-)IgD(-)PI(-)Dsg3E-tag(+) cells using recombinant human Dsg3 with an E-tag (rDsg3-E-His) as a probe. Heavy- and light-chain cDNA was produced by PCR from single B cells; these were used to characterize the usage and CDR3 sequence in the variable region of each gene. RESULTS: Staining conditions were optimized using mouse hybridoma cells against human Dsg3 and peripheral blood mononuclear cells (PBMCs) from a PV patient. Individual Dsg3-specific B cells were isolated by FACS from four PV patients at a frequency of 1-18 per 10(5) PBMCs. CDR3 sequences and identical gene usage in the variable region were identified in several B cells from the same PV patients. Common gene usage was also found among several PV patients. CONCLUSIONS: These results suggested clonal expansion of autoreactive B cells and restricted gene usage for autoreactive B cells against Dsg3. Our method for the isolation of Dsg3-specific B cells will allow the systematic analysis of immunoglobulin gene usage in PV patients, which may elucidate the mechanism of immunopathogenesis.     

A mouse model of pemphigus vulgaris by adoptive transfer of naive splenocytes from desmoglein 3 knockout mice

BACKGROUND: Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by antidesmoglein3 (anti-Dsg3) IgG autoantibodies. Recently, we developed a PV mouse model by adoptive transfer of splenocytes from recombinant Dsg3-immunized Dsg3(-/-) mice to Rag2(-/-) immunodeficient mice that expressed Dsg3. OBJECTIVES: We determined whether the adoptive transfer of naive splenocytes from nonimmunized Dsg3(-/-) mice induces the anti-Dsg3 IgG production and the PV phenoytpe in recipient mice. METHODS: We adoptively transferred naive Dsg3(-/-) splenocytes into Rag2(-/-) mice and compared their PV phenoytpe with those mice receiving immunized Dsg3(-/-) splenocytes. The numbers of splenocytes and their subpopulations required for anti-Dsg3 IgG production were examined. RESULTS: Mice that received naive Dsg3(-/-) splenocytes produced anti-Dsg3 IgG, which bound to keratinocyte cell surfaces in vivo, and developed the PV phenotype, including oral erosions with suprabasilar acantholysis. Antibody production and the appearance of the PV phenotype were delayed by approximately 2 weeks in mice that received naive splenocytes compared with mice that received immunized splenocytes. However, once the PV phenotypes developed, there were no apparent differences in disease severity between the two models. Interestingly, the anti-Dsg3 IgG titres were significantly lower in mice that received naive splenocytes than in mice that received immunized splenocytes, suggesting that the former antibodies were more potent than the latter. The frequency of anti-Dsg3 IgG production depended on the number of transferred naive splenocytes. Both CD4+ T cells and B220+ B cells from naive Dsg3(-/-) mice were essential for the production of anti-Dsg3 IgG antibodies. CONCLUSIONS: Dsg3-specific naive lymphocytes in Dsg3(-/-) mice can be primed and activated by the endogenous Dsg3 in recipient mice to produce pathogenic anti-Dsg3 IgG without active immunization. This approach using naive lymphocytes provides a unique model to dissect immunological mechanisms of tolerance against peripheral autoimmune targets.