Low pathogenicity of anti‐desmoglein 3 immunoglobulin G autoantibodies contributes to the atypical clinical phenotypes in pemphigus

The clinical phenotypes of pemphigus can be explained by the desmoglein (Dsg) compensation theory. However, some atypical cases such as cutaneous pemphigus vulgaris (cPV), in which patients have anti‐Dsg3 antibodies without oral erosions, do not conform to this theory. To explain the discrepancy between clinical phenotypes and anti‐Dsg antibody profiles, the pathogenic strength of immunoglobulin (Ig)G autoantibodies against Dsg3 must be taken into consideration. We analyzed the epitopes and blister‐inducing pathogenic strength of the sera from three patients having IgG against Dsg3 without oral erosions with domain‐swapped recombinant proteins and dissociation assay using cultured normal human epidermal keratinocytes. The results showed that all sera contained IgG directed against the amino terminal EC1 domain of Dsg3, as is found in most PV sera. However, dissociation assays revealed that the pathogenic strength of the anti‐Dsg3 antibodies in all three cases was extremely lower than that of typical PV cases with mucosal involvement. In conclusion, when anti‐Dsg3 IgG antibodies are not sufficient to inhibit the expression of Dsg3 in the oral mucosa, but can inhibit the expression in the skin, skin blisters can result. Therefore, the pathogenicity of anti‐Dsg3 antibodies should be regarded as a key factor contributing to the clinical phenotype in pemphigus patients with conflicting antibody profiles.     

Atypical pemphigus with immunoglobulin G autoantibodies against desmoglein 3 and desmocollin 3

In patients with pemphigus vulgaris (PV), pathogenic immunoglobulin (Ig)G antibodies are most commonly directed against desmoglein 3 (Dsg3). It has recently been reported, however, that IgG anti‐desmocollin 3 (Dsc3) antibodies are detected in some cases of pemphigus with or without IgG anti‐Dsg3 antibodies. We present a case of pemphigus with IgG antibodies against Dsg3 and Dsc3. Subsequent studies showed that the cell surface distribution pattern of Dsc3 but not Dsg3 was altered, suggesting that suprabasal acantholytic blisters were induced by IgG anti‐Dsc3 antibodies rather than IgG anti‐Dsg3 antibodies. Our case suggests that anti‐Dsc3 antibodies may be pathogenic in cases positive for the dual cadherin autoantibodies.     

Evidence of an association between desmoglein 3 haplotypes and pemphigus vulgaris

BACKGROUND: Pemphigus vulgaris (PV, OMIM 169610) is a severe blistering disorder of the skin and mucous membranes, caused by the production of autoantibodies directed against the epithelial adhesive protein desmoglein 3. Although an association between PV and HLA class II alleles has been established, the genetic factors predisposing to the disease remain poorly understood, the rarity of PV hampering the recruitment of substantial patient cohorts. OBJECTIVES: To investigate DSG3 as a candidate PV susceptibility gene. METHODS: We examined five DSG3 single nucleotide polymorphisms (rs8085532, rs3911655, rs3848485, rs3794925 and rs1466379) in two case-control datasets respectively originating from the U.K. (62 PV patients, 154 controls) and northern India (28 patients, 98 controls). RESULTS: In the U.K. sample, we observed a significant association between PV and the DSG3*TCCTC haplotype (Fisher's exact test P = 0.002). A related haplotype (DSG3*TCCCC) was associated with PV in the Indian dataset (P = 0.002). We also found that all British and Indian patients bearing DSG3 risk haplotypes carried at least one copy of a PV-associated HLA allele. CONCLUSIONS: These results suggest that genetic variation of DSG3 may be an additive risk factor predisposing to PV and warrant further investigations of this gene.     

Case of bullous pemphigoid coexisting with anti‐desmoglein autoantibodies

A 79‐year‐old Japanese woman had clinical and histopathological features of bullous pemphigoid, while direct immunofluorescence test revealed C3 and immunoglobulin G depositions in the lower cell surfaces of the epidermis in addition to those in the dermoepidermal junction. Chemiluminescent enzyme immunoassays were positive for desmoglein‐1 and ‐3 antibodies in addition to anti‐BP180 antibodies. In an immunoblotting study, antibodies against both 180‐kDa bullous pemphigoid antigen and 130‐kDa pemphigus vulgaris antigen were detected. Based on these results, bullous pemphigoid coexisting with anti‐desmoglein autoantibodies was diagnosed in this case.     

Cutaneous pemphigus vulgaris with absence of desmoglein 1 autoantibodies. An example of the extended desmoglein compensation theory

A 79 year‐old male patient presented clinically as a typical case of pemphigus foliaceus. He displayed a seborrhoeic pattern of crusting and erosions with an absence of oral involvement. Surprisingly, a biopsy showed suprabasilar acantholysis and direct immunofluorescence consistent with pemphigus vulgaris. Indirect pemphigus antibodies were positive for desmoglein 3 (DSG‐3) but negative for DSG‐1 antibodies. Most cases of cutaneous pemphigus are reported to have both DSG‐1 and DSG‐3 antibodies. A rare cutaneous subtype of pemphigus vulgaris is reported in the literature that may present clinically as seen in our patient. Our patient is clinically similar to these previous reported cases but with a negative DSG‐1 antibody titre. The extended DSG compensation theory explains the differences of clinical expression in pemphigus based on the variable pathogenicity of DSG antibodies as well as the distribution of DSG‐1 and DSG‐3. We discuss this case, highlighting the theories of the pathogenesis of pemphigus and, in particular, the cutaneous pemphigus subtype.     

Clues to diagnosis for unusual mucosal pemphigus demonstrating undetectable anti‐desmoglein 3 serum antibodies by routine tests

Pemphigus is an autoimmune blistering disease caused by immunoglobulin (Ig)G autoantibodies against desmogleins (Dsg). In mucosal‐dominant pemphigus vulgaris (PV), anti‐Dsg3 antibodies play a critical role in acantholysis. We followed two mucosal‐dominant PV cases who suffered from refractory oral mucosal erosions. In these cases, anti‐Dsg3 serum antibodies were not detected by indirect immunofluorescence and enzyme‐linked immunosorbent assay (ELISA). However, direct immunofluorescence showed the intercellular IgG deposition in the epidermis and histopathological findings revealed suprabasal acantholysis. In order to analyze the pathomechanisms in these cases, we first examined the Dsg3 expression patterns in lesional sites and compared them with those of typical mucosal‐dominant PV cases. In typical PV cases, the alteration of Dsg3 distribution was observed in lesional sites by immunostaining. The aggregation of Dsg3, which is the characteristic change in PV mucosal lesions, was observed as the initial change prior to acantholysis. In our cases, a clustering of Dsg3 was observed at mucosal lesions, and the expression levels of Dsg3 in acantholytic lesions were decreased, as observed in typical mucosal‐dominant PV cases. Although anti‐Dsg3 serum antibodies could not be detected by routine tests, anti‐Dsg3 serum antibodies were detected by Dsg3 ELISA using 10‐times more concentrated sera (highly sensitive ELISA). Moreover, purified and concentrated PV IgG showed high pathogenicity when examined by dissociation assay. In conclusion, the detection of morphological changes in Dsg3 distribution and highly sensitive ELISA method could be useful for the early diagnosis of PV recurrence.     

Co‐occurrence of autoantibodies in healthy blood donors

Autoimmune diseases are rare, but their incidence has increased over the past decades. Interestingly, the co‐occurrence of autoimmune diseases is well documented; however, data on the presence of more than one specific autoantibody in healthy individuals are not available. Here, we investigated the prevalence of several autoantibodies in a cohort of over 6000 healthy persons. While individual autoantibodies were rarely detected (i.e. ranging from 0.3% for ANCA to 4.6% for anti‐TPO), the cumulative prevalence of the tested autoantibodies was as high as 10%. Furthermore, our results demonstrate co‐occurrence of ANA with specific autoantibodies that target TPO, CCP and Dsg1/3, while ANCA and autoantibodies to PCA and BP180/BP230 were not more frequent in ANA‐positive compared to ANA‐negative samples. This indicates that shared and independent mechanisms influence loss of tolerance to distinct sets of self‐antigens.     

Immune response towards the amino‐terminus of desmoglein 1 prevails across different activity stages in nonendemic pemphigus foliaceus

Background Pemphigus foliaceus (PF) is a blistering skin disease mediated by antibodies to desmoglein (Dsg) 1. The two major subtypes are nonendemic and endemic PF. A previous study in endemic PF demonstrated that changes in antibody epitope could modulate disease relapse and remission. Objectives To characterize the frequency of immunoreactivity to various Dsg1 extracellular (EC) domains in nonendemic PF and to study if there is any change in epitope profile across various activity stages. Methods Sera from 34 patients with nonendemic PF were selected. To map the conformational epitopes by immunoprecipitation‐immunoblotting, we constructed five Dsg1/Dsg2 domain‐swapped molecules, with each molecule representing one EC domain of Dsg1 on a backbone of Dsg2. Results Dsg1 EC1, EC2, EC3, EC4 and EC5 domains were recognized by 88%, 50%, 13%, 22% and 0% of active PF sera, respectively. Immunoreactivity to EC3 or EC4 often cosegregated with that to either EC1 or EC2. Longitudinal follow‐up of 21 patients with PF for a median of 16 months revealed that, in most cases, immunoreactivity to the amino‐terminus of Dsg1 persisted across various activity stages; only two patients lost their EC1 reactivity upon remission and changed their major epitope(s) to EC2 ± EC3. Conclusions Most of the anti‐Dsg1 antibodies in nonendemic PF bind to the amino‐terminus of Dsg1, a region critical for intercellular adhesion of cadherins, and this skewed amino‐terminal immunoreactivity prevails across various activity stages in most patients, even upon remission. These findings are valuable for understanding the biology of Dsg‐mediated cellular adhesion as well as for the development of epitope‐based monitoring and therapeutic strategies.     

Cleavage of desmoglein 3 can explain its depletion from keratinocytes in pemphigus vulgaris

We have previously demonstrated that serum of patients with pemphigus vulgaris induces reduction of desmoglein 3 (Dsg3) half-life in keratinocytes (FEBS Lett 2006: 580: 3276). This phenomenon seems to occur as a consequence of the progressive depletion of Dsg3 from desmosomes. Here we reported that reduction of full-length Dsg3 may be due to its progressive cleavage, leading to the formation of two fragmentation products with apparent molecular masses of about 60 kDa (fragment 1) and 70 kDa (fragment 2), as revealed by Western blotting. Unexpectedly, analysis of fragmentation pattern suggested cleavage to occur intracellularly. Consistently, fragment 1 was shed and localized within the cytosol, as shown by living cell immunofluorescence microscopy. Total amounts of full-length plakoglobin and Dsg1 were apparently unchanged. Taken together, our findings provide evidence that proteolytic processing of Dsg3 can lead to depletion of Dsg3 from the cell.     

Paraneoplastic pemphigus without antidesmoglein 3 or antidesmoglein 1 autoantibodies

Paraneoplastic pemphigus (PNP) is an autoimmune mucocutaneous blistering disease characterized by IgG autoantibodies that bind to various epithelia and immunoprecipitate a complex of 250, 230, 210, 190 and 170 kDa proteins. A recent study has suggested that PNP patients have antidesmoglein (Dsg) 3 autoantibody and that the antibody plays a pathogenic role in PNP. We report a 72-year-old woman with PNP associated with thymoma and adenocarcinoma of the lung. Diagnosis of PNP was made by the characteristic clinical, histological and immunopathological findings, as well as immunoprecipitation of characteristic 230, 210 and 190 kDa proteins. Using enzyme-linked immunosorbent assay with baculovirus-expressed recombinant proteins, the patient's serum was negative against both Dsg 3 and Dsg 1. This finding is unusual, and it suggests that the target antigen, which is involved in acantholysis, may be other than Dsg 3 in this case.     

Neonatal pemphigus vulgaris

A male newborn with skin erosions was born to a 32-year-old woman who was under treatment for pemphigus vulgaris that had been diagnosed 16 months earlier. Antibodies to desmoglein (Dsg)1 and Dsg3 were analyzed by enzyme-linked immunosorbent assay. Index values of antibodies to Dsg1 and Dsg3 were 49 (normal index values, <14) and 121 (normal index values, <7), respectively. Those findings concluded a diagnosis of neonatal pemphigus vulgaris. No new vesicles or bullae appeared in the newborn after the birth. Non-corticosteroid ointments produced prompt epithelialization on the erosive lesions. All the eruptions disappeared in 3 weeks. The level of serum anti-Dsg3 autoantibodies when measured at the 76th day was negative (<5).     

Pemphigus vegetans – immunopathological findings in a rare variant of pemphigus vulgaris

A patient with painful erosions of the oral cavity and the labia minora developed multifocal blisters in inter‐triginous areas. These blisters eroded and evolved into papillomatous erosive vegetations. Histopathology and immunopathological investigations confirmed the diagnosis of pemphigus vegetans, mediated by IgG autoantibodies. The circulating IgG1 and IgG4 autoantibodies were exclusively directed against desmoglein 3, as shown by ELISA and indirect immunofluorescence studies. These IgG1 and IgG4 isotypes were also in vivo bound, as demonstrated with immunoperoxidase staining of perilesional skin. Our clinical, biochemical and immunopathological observations confirm the hypothesis that pemphigus vegetans is a variant of pemphigus vulgaris.     

Evaluating efficacy of plasmapheresis for patients with pemphigus using desmoglein enzyme-linked immunosorbent assay

BACKGROUND: Pemphigus is an autoimmune bullous disease caused by circulating IgG autoantibodies against cell-cell adhesion molecules between keratinocytes: desmoglein (Dsg) 3 and Dsg1. Plasmapheresis is often used to treat severe cases of pemphigus. Enzyme-linked immunosorbent assays (ELISAs) against recombinant Dsg3 and Dsg1 have recently become available, allowing us to quantify IgG autoantibodies against Dsg3 and Dsg1. OBJECTIVES: Using ELISA against recombinant Dsg3 and Dsg1, to evaluate the efficacy of plasmapheresis in pemphigus. METHODS: Sera obtained from 10 patients with pemphigus vulgaris and one with pemphigus foliaceus following a total of 16 cycles of centrifugal plasmapheresis and 12 effluents from the plasmapheresis were subjected to ELISA against Dsgs. The percentage of IgG autoantibodies removed was calculated using two different formulae: one used serum titres before and immediately after plasmapheresis and the other used the absolute amounts of IgG autoantibodies in the effluents. The percentage fall of anti-Dsg antibody level was also calculated using the serum titres 1 day after plasmapheresis. RESULTS: Using serum titres immediately after plasmapheresis, there was a mean fall per treatment in anti-Dsg 3 antibody level of 43.0% (n = 12) and in anti-Dsg1 antibody level of 48.4% (n = 7). By contrast, calculated from the effluents, on average one treatment removed only 14.6% of anti-Dsg3 antibodies (n = 12) and 16.4% of anti-Dsg1 antibodies (n = 7). This should reflect the correct percentage as it is based on the absolute amounts of IgG autoantibodies removed. Using serum titres 1 day after plasmapheresis, there was a mean fall per treatment in anti-Dsg 3 antibody level of 12.9% (n = 2) and in anti-Dsg1 antibody level of 8.4% (n = 4). The percentage of IgG autoantibodies removed 1 day after plasmapheresis was lower than that found to be removed immediately after plasmapheresis (n = 6). CONCLUSIONS: One centrifugal plasmapheresis procedure eliminates about 15% of the IgG autoantibodies from the whole body. The percentage fall of anti-Dsg IgG antibody level differed depending on when the serum samples were obtained after plasmapheresis. The change in the percentage fall of anti-Dsg antibody level within 1 day after plasmapheresis is thought to be attributable to the passive diffusion of the IgG autoantibodies from the extravascular space to the intravascular space. Therefore, removal of IgG autoantibodies calculated using serum titres only should be evaluated carefully considering the equilibration of the IgG autoantibodies between the different body spaces.     

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.     

A study of desmoglein 1 autoantibodies in pemphigus vulgaris: racial differences in frequency and the association with a more severe phenotype

BACKGROUND: Pemphigus vulgaris (PV) is characterized by pathogenic autoantibodies to desmoglein (Dsg) 3, but additional antibodies to Dsg1, the pemphigus foliaceus antigen, are detectable in some cases. OBJECTIVES: To investigate the clinical significance of the presence of both Dsg 1 and 3 antibodies. METHODS: In 79 subjects with PV, enzyme-linked immunosorbent assays were used to detect IgG autoantibodies reactive with the ectodomain of Dsg1 and Dsg3. RESULTS: There was a clear association between the clinical phenotype and the Dsg antibody profile. All subjects had Dsg3 autoantibodies and 61% had coexisting Dsg1 antibodies (Dsg3+/Dsg1+). PV limited entirely to the mucosal surfaces was seen only in Dsg3+/Dsg1- patients, while additional Dsg1 antibodies (Dsg3+/Dsg1+) predicted cutaneous in addition to mucosal involvement. Although minor cutaneous involvement was observed in most Dsg3+/Dsg1- patients, severe cutaneous involvement was seen only in Dsg3+/Dsg1+ patients. Dsg1 antibodies were detectable early in the course of disease and their appearance did not relate to the use of systemic therapy. The proportion of Dsg1+ patients was higher in those of Indian origin compared with white northern Europeans (P < 0.05). CONCLUSIONS: These data suggest that the presence of Dsg1 antibodies is predictive of a potentially more severe disease and that genetic factors may determine the Dsg antibody profile.     

The severity of cutaneous and oral pemphigus is related to desmoglein 1 and 3 antibody levels

BACKGROUND: Pemphigus vulgaris (PV) and foliaceus (PF) are characterized by antibodies to the desmosomal proteins desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1), respectively. Past studies using indirect immunofluorescence (IIF) as a measure of pemphigus antibody levels have failed to demonstrate consistently a relationship between disease severity and IIF titres. However, IIF is not able to measure separately Dsg1 and 3 antibodies, unlike enzyme-linked immunosorbent assays (ELISA), which utilize recombinant proteins. OBJECTIVES: To compare independently Dsg1 and 3 antibody levels with the severity of both cutaneous and oral involvement in PV and PF. Patients and methods Four hundred and twenty-four serum samples were analysed from 80 subjects with PV and 24 with PF. IgG antibodies to Dsg1 and 3 were measured by ELISA. For every sample analysed, the associated severity of skin and oral disease were graded from 0 to 3; quiescent, mild, moderate and severe. RESULTS: A relationship between Dsg1 antibodies and skin severity was demonstrated such that a 10-unit increase in Dsg1 ELISA value was associated with a 34% chance of having a higher severity score [95% confidence interval (CI), 25-45%, P < 0.0005]. This was observed in both PV and PF. Oral severity was associated with Dsg3 antibody levels and a 10-unit increase in the Dsg3 ELISA value was associated with a 25% chance of a higher oral severity score (CI 17-33%, P < 0.0005). We were unable to demonstrate a relationship between Dsg1 antibodies and oral severity, even after adjusting for the effect of Dsg3 antibodies. Similarly, there was no relationship between Dsg3 antibodies and skin severity. CONCLUSIONS: This study suggests that the clinical phenotype of pemphigus, in particular the balance of skin and oral disease, is determined principally by the quantities of Dsg1 and 3 autoantibodies, respectively.     

IgG, IgA and IgE autoantibodies against the ectodomain of desmoglein 3 in active pemphigus vulgaris

BACKGROUND: IgG autoantibodies against desmoglein (Dsg) 3 play a key part in the pathogenesis of pemphigus vulgaris (PV), the most severe autoimmune bullous disorder. OBJECTIVES: To determine whether immunoglobulin isotypes other than IgG are detectable in the sera of patients with PV and whether a particular immunoglobulin subtype is associated with a distinct clinical phenotype of PV. METHODS: Sera from 41 patients with acute-onset, chronic active, and remittent PV disease with mucosal and cutaneous lesions were assayed against a baculovirus-expressed Dsg3 protein by immunoblot analysis. RESULTS: In acute-onset PV, Dsg3-reactive IgG1 was detected in nine of 15 (60%), IgG4 in 14 of 15 (93%), IgA in nine of 15 (60%) and IgE in two of 15 (13%) sera. In chronic active PV, Dsg3-reactive IgG1 was detected in 11 of 18 (61%), IgG4 in 16 of 18 (89%), IgA in 13 of 18 (72%) and IgE in two of 18 (11%) sera. In contrast, sera from patients with remittent PV disease contained only Dsg3-reactive IgG1 in six of eight (75%) and IgG4 in four of eight (50%) cases, but not Dsg3-reactive IgA or IgE. CONCLUSIONS: In extension of previous findings, our study demonstrates that, in addition to IgG autoantibodies, IgA and occasionally IgE autoantibodies reactive with Dsg3 are present in acute and chronic active PV. The detection of Dsg3-reactive autoantibodies of the IgG4, IgA and IgE subclasses in active PV provides additional evidence that PV is a T-helper 2-regulated autoimmune disorder.