HLA-DRB1 polymorphisms and autoimmune responses to desmogleins in Japanese patients with pemphigus

Sporadic pemphigus foliaceus and class II human leucocyte antigen allele associations in the white British and Indo-Asian populations in the UK

BACKGROUND

Pemphigus foliaceus (PF) has both genetic and environmental susceptibility factors. Current data on human leucocyte antigen (HLA) in patients with sporadic PF are limited.

AIM

To better define the distribution of HLA alleles in patients with PF in the UK.

METHODS

We recruited 36 patients [26 of white British (WB) descent, 10 of Indo-Asian (IA) descent] with PF who were living in the UK and 159 ethnically matched normal controls, and analysed their class II HLA DRB1 and DQB1 allele distribution.

RESULTS

There was an increased frequency of DRB1*1404 in association with DQB1*0503 in IA patients with PF. The DRB1*04 allele group as a whole had an increased frequency (P < 0.001) in the WB patient group compared with controls. The alleles contributing to this significance were DRB1*0401 (P = 0.03) and DRB1*0404 (P < 0.01).

CONCLUSION

This is the largest HLA association study in sporadic PF from the UK to date. There appears to be a difference in PF susceptibility alleles between WB and IA patients, highlighting the importance of racial variation in genetic susceptibility to disease development.

Investigation of the predisposing factor of pemphigus and its clinical subtype through a genome-wide association and next generation sequence analysis

BACKGROUND

Pemphigus is an autoimmune blistering disease with pemphigus vulgaris (PV) and foliaceus (PF) as the two major histological subtypes. Associations with HLA molecules have been suggested, but specific HLA risk variants as well as non-HLA risk variants remain to be discovered.

METHODS

We performed a two-stage genome-wide association study in the Chinese Han population through a genome-wide discovery analysis and follow-up validation analysis in a total number of 210 PV, 159 PF and 2493 healthy controls. HLA imputation as well as high coverage next generation sequencing based HLA genotyping was employed to investigate the association of classical HLA alleles and amino acid change.

RESULTS

We have discovered independent novel associations with PF at rs2178077 on 12q24.33, located next to RAN (P_PF = 1.57 × 10^-9 ) and rs3888722 within the MHC region (P = 6.73 × 10^-9 ). For the HLA variants, we confirmed independent genome-wide level risk associations in HLA-DQB1 and HLA-DRB1, with DQB1*05:03 to be the strongest association with PV (P = 8.59 × 10^-68 , OR = 31.16) and PF (P = 4.84 × 10^-17 , OR = 5.64). In addition, DRB1*14 was demonstrated to be a second independent variants (P = 4.2 × 10^-63 , OR = 35.47) for PV, while DRB1*04:06 was demonstrated to be the second independent signal (P = 7.44 × 10^-13 , OR = 5.58) for PF.

CONCLUSIONS

These findings advance our understanding of the genetic basis of pemphigus susceptibility and may offer opportunities for risk prediction and preventive treatment for pemphigus, in particular for PV.

The Genetics of Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease caused by auto-antibodies (auto-Abs) directed against epithelial desmosomal components and leading to disruption of cell-cell adhesion. The exact mechanisms underlying the disease pathogenesis remain unknown and treatment is still based on immunosuppressive drugs, such as corticosteroids, which are associated with potentially significant side effects. Ethnic susceptibility, familial occurrence, and autoimmune comorbidity, suggest a genetic component to the pathogenesis of the disease, which, if discovered, could advance our understanding of PV pathogenesis and thereby point to novel therapeutic targets for this life-threatening disorder. In this article, we review the evidence for a genetic basis of PV, summarize the different approaches used to investigate susceptibility traits for the disease and describe past and recent discoveries regarding genes associated with PV, most of which belong to the human leukocyte antigen (HLA) locus with limited data regarding association of non-HLA genes with the disease.

Association between HLA-DQB1 polymorphisms and pemphigus vulgaris: A meta-analysis

OBJECTIVE

This study was performed to systematically summarize the results on the association of HLA-DQB1 polymorphisms with pemphigus vulgaris (PV) and other related factors.

METHODS

A comprehensive literature search of PubMed, The Cochrane Library, Embase, and Google Scholar database was conducted to identify relevant articles in English, with the last report up to November 1, 2016. Heterogeneity test was performed, and publication bias was evaluated. Stata software 12.0 was used to perform the meta-analysis. Odds ratios (ORs) and 95% confidence intervals (CI) were used to describe the correlation by random-effects model.

RESULTS

18 studies were obtained after searching databases: 10 studies were about Caucasian, and 8 articles were about non-Caucasian. Meta-analysis revealed that the allele and phenotype frequencies of DQB1*05 were markedly higher in PV patients than in controls [P < 0.001, OR: 2.640, 95%CI: 1.570-4.441; P = 0.030, OR 3.688, 95%CI: 1.138-11.946]. In addition, DQB1*03 was significantly increased at the allele level [P < 0.001, OR: 2.080, 95%CI: 1.507-2.869], and DQB1*02 was significantly decreased in PV at the allele and phenotype levels [P = 0.002, OR: 0.450, 95%CI: 0.289-0.702; P = 0.001, OR: 0.293, 95%CI: 0.146-0.587]. When based on each subtype of HLA-DQB1, DQB1*05:03 and DQB1*03:02 may play susceptibility roles in PV, and DQB1*03:03, DQB1*05:01 and DQB1*06:01 are negatively associated with PV.

CONCLUSION

In summary, our study suggests that alleles from the groups DQB1*05 and DQB1*03, concretely DQB1*05:03 and DQB1*03:02, respectively, may be the susceptibility factors for PV at allele and phenotype levels, whereas DQB1*05:01, DQB1*02, DQB1*06:01, and DQB1*03:03 are negatively associated with PV.

Study of the association between human leukocyte antigens (HLA) and pemphigus vulgaris in Brazilian patients

BACKGROUND

Pemphigus vulgaris is a mucocutaneous blistering autoimmune disease that manifests as painful blisters or erosions on the skin and/or mucosal surfaces. IgG autoantibodies target desmoglein, playing a major role in disease pathogenesis. Genetic predisposal to pemphigus vulgaris, especially the HLA DR and DQ alleles, has been known since the 1980s. The unique constitution of the Brazilian population favors exploratory genetic studies.

METHODS

The study group included 51 patients with a confirmed diagnosis of pemphigus vulgaris from a tertiary hospital in Sao Paulo city, Sao Paulo, southeast Brazil. DNA was extracted from peripheral blood, and HLA A, B, C, DR, and DQ typing was performed. The control group was composed of a database of 297 deceased donors from the city of São Paulo typed with the same method. The statistical significance level was adjusted using the Bonferroni correction depending on the phenotypic frequencies evaluated for HLA A, HLA B, HLA C, HLA DRB1, DQA1, and HLA DQB1.

RESULTS

The alleles HLA-B*57, HLA-C*15, HLA-DRB1*04:02, HLA-DRB1*08:04, HLA-DRB1*14:01, DQA1*03:01, DQB1*03:02, and DQB1*05:03 were associated with susceptibility. Alleles HLA DRB1*04:02 and HLA-DRB1*14:01 and their respective haplotypes DRB1*04-DQA1*03:01-DQB1*03:02, and DRB1*14-DQA1*01:01-DQB1*05:03 conferred a risk of the disease.

CONCLUSIONS

The DRB1*04:02 and DQB1*05:03 alleles are associated with pemphigus vulgaris in our study as well as in various populations. The association with HLA-DRB1*08:04 in our study was confirmed to be specific to this allele and not to linkage disequilibrium to any adjacent gene. The association between HLA-B*57 and pemphigus vulgaris is reported for the first time in the present study.

HLA-DRB1 alleles are associated with the susceptibility to sporadic Parkinson's disease in Chinese Han population

Immune disorders may play an important role in the pathogenesis of Parkinson's disease (PD). Recently, polymorphisms in the HLA-DR region have been found to be associated with sporadic PD in European ancestry populations. However, polymorphisms in the HLA complex are highly variable with ethnic and geographic origin. To explore the relationships between polymorphisms of the HLA-DR region and sporadic PD in Chinese Han population, we genotyped 567 sporadic PD patients and 746 healthy controls in two independent series for the HLA-DRB1 locus with Polymerase chain reaction-sequence based typing(PCR-SBT). The χ(2) test was used to evaluate the distribution of allele frequencies between the patients and healthy controls. The impact of HLA-DRB1 alleles on PD risk was estimated by unconditional logistic regression. We found a significant higher frequency of HLA-DRB1*0301 in sporadic PD patients than in healthy controls and a positive association, which was independent of onset age, between HLA-DRB1*0301 and PD risk. Conversely, a lower frequency of HLA-DRB1*0406 was found in sporadic PD patients than in healthy controls, with a negative association between HLA-DRB1*0406 and PD risk. Furthermore, a meta-analysis involving 195205 individuals was conducted to summarize the frequencies of these two alleles in populations from various ethnic regions, we found a higher frequency of HLA-DRB1*0301, but a lower frequency of HLA-DRB1*0406 in European ancestry populations than that in Asians, this was consistent with the higher prevalence of sporadic PD in European ancestry populations. Based on these results, we speculate that HLA-DRB1 alleles are associated with the susceptibility to sporadic PD in Chinese Han population, among them HLA-DRB1*0301 is a risk allele while the effect of HLA-DRB1*0406 deserves debate.

Association between HLA-DRB1 polymorphisms and pemphigus vulgaris: a meta-analysis

Summary

Background Several studies have reported that HLA-DRB1 may be correlated with pemphigus vulgaris (PV), but most have been based on small samples and the results remain inconsistent and unclear.

Objectives To investigate the correlation between DRB1 and PV by a meta-analysis of case–control/nonfamily studies.

Methods PubMed, Wiley Online Library, ScienceDirect, Google Scholar, Cochrane Library, Chinese National Knowledge Infrastructure and Wanfang databases were searched for studies including: (i) ‘pemphigus’; and (ii) ‘human leukocyte antigen’, ‘HLA’, ‘major histocompatibility complex’, ‘MHC’ or ‘DRB1’. Eighteen selected studies were used in meta-analyses to evaluate DRB1 alleles and phenotypes by calculating the respective odds ratios (ORs) and 95% confidence intervals (CIs). Stratified meta-analyses and meta-regression analysis were also conducted.

Results The frequencies of three genotypes (allele and phenotype, respectively) were significantly increased in PV: DRB1*04 [P-value for comparability (Pc) < 0·00001, OR 3·61, 95% CI 2·28–5·71; Pc = 0·0002, OR 4·14, 95% CI 1·98–8·65], DRB1*08 (Pc = 0·03, OR 2·25, 95% CI 1·07–4·70; Pc = 0·0003, OR 2·46, 95% CI 1·51–4·01) and DRB1*14 (Pc < 0·00001, OR 6·47, 95% CI 4·52–9·26; Pc < 0·00001, OR 9·68, 95% CI 4·47–20·98). Three others (allele and phenotype, respectively) were significantly decreased in PV: DRB1*03 (Pc < 0·00001, OR 0·28, 95% CI 0·19–0·41; Pc = 0·0001, OR 0·25, 95% CI 0·12–0·51), DRB1*07 (Pc = 0·004, OR 0·45, 95% CI 0·26–0·78; Pc = 0·0002, OR 0·27, 95% CI 0·14–0·54) and DRB1*15 (Pc = 0·001, OR 0·35, 95% CI 0·18–0·66; Pc = 0·002, OR 0·32, 95% CI 0·16–0·65). Ethnicity partially explained the heterogeneity of DRB1*07, DRB1*08 and DRB1*14 phenotypes.

Conclusions Our findings suggest that DRB1*04, DRB1*08 and DRB1*14 are statistically significant susceptibility factors for PV. Conversely, DRB1*03, DRB1*07 and DRB1*15 may be negatively associated with PV. Specific HLA-DRB1 types may influence the susceptibility or resistance to PV, which needs further investigations.

Identification of quantitative trait loci in experimental epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a chronic mucocutaneous autoimmune skin blistering disease. Several lines of evidence underscore the contribution of autoantibodies against type VII collagen (COL7) to the pathogenesis of EBA. Furthermore, EBA susceptibility is associated with the MHC haplotype in patients (HLA-DR2) and in immunization-induced EBA in mice (H2s). The latter study indicated an additional contribution of non-MHC genes to disease susceptibility. To identify non-MHC genes controlling EBA susceptibility, we intercrossed EBA-susceptible MRL/MpJ with EBA-resistant NZM2410/J and BXD2/TyJ as well as Cast mice. Mice of the fourth generation of this four-way autoimmune-prone advanced intercross line were immunized with a fragment of murine COL7 to induce EBA. Anti-COL7 autoantibodies were detected in 84% of mice, whereas deposition of complement at the dermal-epidermal junction (DEJ) was observed in 50% of the animals; 33% of immunized mice presented with overt clinical EBA. Onset of clinical disease was associated with several quantitative trait loci (QTLs) located on chromosomes 9, 12, 14, and 19, whereas maximum disease severity was linked to QTLs on chromosomes 1, 15, and 19. This more detailed insight into the pathogenesis of EBA may eventually lead to new treatment strategies for EBA and other autoantibody-mediated diseases.

Pemphigus autoimmunity: hypotheses and realities

The goal of contemporary research in pemphigus vulgaris and pemphigus foliaceus is to achieve and maintain clinical remission without corticosteroids. Recent advances of knowledge on pemphigus autoimmunity scrutinize old dogmas, resolve controversies, and open novel perspectives for treatment. Elucidation of intimate mechanisms of keratinocyte detachment and death in pemphigus has challenged the monopathogenic explanation of disease immunopathology. Over 50 organ-specific and non-organ-specific antigens can be targeted by pemphigus autoimmunity, including desmosomal cadherins and other adhesion molecules, PERP cholinergic and other cell membrane (CM) receptors, and mitochondrial proteins. The initial insult is sustained by the autoantibodies to the cell membrane receptor antigens triggering the intracellular signaling by Src, epidermal growth factor receptor kinase, protein kinases A and C, phospholipase C, mTOR, p38 MAPK, JNK, other tyrosine kinases, and calmodulin that cause basal cell shrinkage and ripping desmosomes off the CM. Autoantibodies synergize with effectors of apoptotic and oncotic pathways, serine proteases, and inflammatory cytokines to overcome the natural resistance and activate the cell death program in keratinocytes. The process of keratinocyte shrinkage/detachment and death via apoptosis/oncosis has been termed apoptolysis to emphasize that it is triggered by the same signal effectors and mediated by the same cell death enzymes. The natural course of pemphigus has improved due to a substantial progress in developing of the steroid-sparing therapies combining the immunosuppressive and direct anti-acantholytic effects. Further elucidation of the molecular mechanisms mediating immune dysregulation and apoptolysis in pemphigus should improve our understanding of disease pathogenesis and facilitate development of steroid-free treatment of patients.

ICOS Gene Polymorphism May Be Associated with Pemphigus

Background:

Pemphigus is an autoimmune blistering disease mediated by circulating IgG autoantibodies directed against desmogleins 3 and/or 1. As pemphigus is a T cell–mediated disease, one may assume that genetically determined disregulation of costimulatory signal may be involved in its pathogenesis.

Objective:

The aim of the present study was to evaluate the relationship between polymorphisms in genes encoding costimulatory receptors, CTLA4 and ICOS, and pemphigus in the Polish population.

Methods:

The study included 54 patients with pemphigus: 40 with pemphigus vulgaris (PV) and 14 with pemphigus foliaceus (PF). Additionally, 176 healthy unrelated blood donors served as controls. +49A/G CTLA4 and IVS1+173 ICOS polymorphisms were identified using a modified polymerase chain reaction–restriction fragment-length polymorphism.

Results:

Analysis of the frequency of genotypes and alleles of +49A/G CTLA4 gene polymorphism showed no statistically significant differences between the PV and PF patients and the controls. The distribution of genotypes in IVS1+173 ICOS polymorphisms was significantly different in both PV ( p < .01) and PF ( p = .0004) patients when compared to controls. The carriers of the allele C were more frequent in PV or PF in comparison with the control group ( p < .001 for both groups).

Conclusions:

Our results suggest that genetically determined abnormal function of costimulatory receptors in T cells may be associated with the pathogenesis of pemphigus.

Relationship between target antigens and major histocompatibility complex (MHC) class II genes in producing two pathogenic antibodies simultaneously

In this report,we present 15 patients with histological and immunopathologically proven pemphigus vulgaris (PV). After a mean of 80 months since the onset of disease, when evaluated serologically, they had antibodies typical of PV and pemphigoid (Pg). Similarly, 18 patients with bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP) were diagnosed on the basis of histology and immunopathology.After a mean of 60 months since the onset of disease, when their sera were evaluated they were found to have Pg and PV autoantibodies. In both groups of patients the diseases were characterized by a chronic course, which included several relapses and recurrences and were non-responsive to conventional therapy. The major histocompatibility complex class II (MHC II) genes were studied in both groups of patients and phenotypes associated typically with them were observed. Hence, in 33 patients, two different pathogenic autoantibodies were detected simultaneously. The authors provide a computer model to show that each MHC II gene has relevant epitopes that recognize the antigens associated with both diseases. Using the databases in these computer models, the authors present the hypothesis that these two autoantibodies are produced simultaneously due to the phenomena of epitope spreading.

HLA class II (DRB, DQA1 and DQB1) allele and haplotype frequencies in the patients with pemphigus vulgaris

INTRODUCTION

Pemphigus vulgaris (PV), an autoimmune disease affecting the skin and mucous membranes, is associated with some human leukocyte antigen (HLA) class II alleles and haplotypes.

MATERIALS AND METHODS

In order to evaluate the association of HLA-DR and DQ alleles and haplotypes in Iranian non-Jewish patients with PV, 52 patients with PV and 180 normal subjects as control group were investigated in this study.

RESULTS AND DISCUSSION

HLA-DRB1*04, -DRB1*1401, -DRB4, -DQA1*0104, -DQA1*03011, -DQB1*0302, and -DQB1*0502 alleles have been significantly increased in our patients group. Moreover, the haplotypes HLA-DRB1*04/-DQA1*03011/-DQB1*0302 and HLA-DRB1*1401/-DQA1*0104/-DQB1*0502 increased significantly in our patients. In contrast, the following alleles decreased significantly in our patients: HLA-DRB1*15, -DRB1*0301, -DRB1*07, -DRB1*11, -DRB5, -DQA1*0101, -DQA1*0103, -DQA1*201, -DQA1*05, -DQB1*0201, -DQB1*0301, -DQB1*06011, and -DQB1*0602. In addition, HLA-DRB1*15/-DQA1*0103/-DQB1*06011, HLA-DRB1*0301/-DQA1*05011/-DQB1*0201, HLA-DRB1*07/-DQA1*0201/-DQB1*0201, and HLA-DRB1*11/-DQA1*05/-DQB1*03011 decreased significantly in our patients. Genetic factors are involved in the occurrence of PV; HLA-DRB1*04 and -DRB1*1401 alleles and the related haplotypes are suggestive to be two major PV susceptibility factors in our population study.

Epidemiology of pemphigus in Macedonia: A 15-year retrospective study (1990?2004)

BACKGROUND

Pemphigus is an autoimmune blistering skin disease mediated by auto-antibodies directed against desmoglein proteins. There are only a few epidemiological studies on pemphigus. Our objective was to determine the epidemiological features of pemphigus in Macedonia, and to compare the results with those reported elsewhere.

METHODS

Diagnosis in all cases was confirmed by histopathology and direct immunofluorescence. Binomial distribution testing and Fisher's exact-test at the 0.01 level of significance were used to determine if particular demographic groups were over-/ under-represented among the pemphigus patients.

RESULTS

One hundred and thirty-three new pemphigus cases were diagnosed in Macedonia from 1990-2004. The average annual incidence was 0.44/100,000 inhabitants (SD = 0.17). The incidence doubled to 0.89 in 2001 during the local armed unrest. The disease did not affect either gender to a greater extent. The average annual incidence was 0.51 for ethnic Macedonians. Roma (Gypsies) had a statistically significantly higher incidence of pemphigus at 2.4 cases/100,000 individuals. Ethnic Albanians had statistically significantly lower incidence of 0.1 cases/100,000 individuals. The most common variant was pemphigus vulgaris (77.4%).

CONCLUSIONS

The annual incidence for pemphigus in Macedonia is 0.44 cases/100,000 inhabitants. Most common form was pemphigus vulgaris. An epidemiological peak occurred in 2001 during the local armed conflict. Macedonian Roma had a sixfold higher incidence of pemphigus compared with the overall population; ethnic Albanians had a fourfold lower incidence.

Immunohistological analysis of immune cells in blistering skin lesions

BACKGROUND

Bullous skin lesions are characterised by the presence of intraepidermal or subepidermal bullae. Although inflammatory cell infiltrate is a constant feature in these lesions, their immunophenotypic characterisation is still incomplete.

AIM

To determine whether the development of bullous skin diseases is associated with changes in the inflammatory cell infiltrate.

MATERIALS AND METHODS

34 cases representing lesions with both intraepidermal and subepidermal bullae were examined using immunoperoxidase staining methods and antibodies targeting antigens for histiocytes (CD68), B cells (CD20+), T cells (CD3+), T cells with cytotoxic potential (T cell intracellular associated antigen, TIA1+) and activity (granzyme B, GRB+). The adjacent normal skin (lesions) and an additional five cases of normal skin were also examined (controls).

RESULTS

The transition from normal skin to lesional skin (lesions with intraepidermal and subepidermal bullae) was associated with a significant increase (p< or =0.05) in the density of total inflammatory cell infiltrate, CD68+ cells, CD3+ T lymphocytes, CD20+ B lymphocytes, TIA1+ -resting cytotoxic T cells and GRB+ T cells with cytotoxic activity.

CONCLUSIONS

The increase in inflammatory cell infiltrate during the transition from normal to lesional skin may reflect the presence of an increased antigenicity of the lesional cells or a response to some basement membrane components. CD68+ and CD3+ cells, especially the resting cytotoxic ones, achieved numerical dominance in these lesions. Cell-mediated immunity seems to have critical role in the development of these lesions.

A Truncated Alternative Spliced Isoform of Human Desmoglein 1 Contains a Specific T Cell Epitope Binding to the Pemphigus Foliaceus-Associated HLA Class II DRβ1*0102 Molecule

Desmogleins (Dsg) are transmembrane glycoproteins of the desmosome that allow a cell-cell adhesion between keratinocytes and comprise four different isoforms (Dsg1 to Dsg4). Two Dsg are targeted by pathogenic autoantibodies produced in the course of autoimmune bullous skin diseases, Dsg1 in pemphigus foliaceus (PF), and Dsg3 and Dsg1 in pemphigus vulgaris. The genetic susceptibility to PF is associated with certain HLA class II alleles, which are thought to participate in disease pathogenesis through their capacity to accommodate autoantigen-derived peptides and present them to autoreactive T cells. So far, a unique isoform of Dsg1 has been described in humans, which includes several immunodominant T cell epitopes. In this study, we describe an alternative transcript of DSG1, which contains a 101-bp insertion corresponding to the 3' end of DSG1-intron 6 and introducing a stop codon in the nucleotide sequence. This alternative transcript leads to the synthesis of a truncated isoform of Dsg1 expressed in normal human epidermis. This isoform bears a specific peptide sequence that binds to the PF-associated HLA class II DRbeta1*0102 molecule as shown in a HLA-DR peptide-binding assay, and induces PF T cell proliferation. These data provide an illustration of an autoantigen encoded by alternative spliced transcript that may participate in the pathogenesis of the disease by bearing PF-associated HLA class II restricted-epitope.

Disease relevant HLA class II alleles isolated by genotypic, haplotypic, and sequence analysis in North American Caucasians with pemphigus vulgaris

Early studies of genetic susceptibility to pemphigus vulgaris (PV) showed associations between human leukocyte antigen (HLA) DR4 and DR6 and disease. The emergence of DNA sequencing techniques has implicated numerous DRB1 and DQB1 loci in various populations, leading to confusion regarding which exact alleles confer susceptibility. The strong linkage disequilibrium among DR and DQ HLA alleles further complicates the investigation of the true susceptibility loci. In this study, we report genotyping data for the largest sampling of North American Caucasian non-Jewish and Ashkenazi Jewish PV patients studied to date and compare our data with other population studies. To pinpoint true susceptibility, alleles among overrepresented sequences, we applied a step-wise reductionist analysis through (1) determination of the degree of linkage disequilibrium (LD) between purportedly associated alleles, (2) haplotype frequencies comparisons, and (3) primary sequence comparisons of disease-associated versus non-disease-associated alleles to identify crucial differences in amino acid residues in putative peptide binding pockets. Collectively, our data provide extended support for the hypothesis that the HLA associations in Caucasian PV patients map to DRB1*0402 and DQB1*0503 alone. Further structure-function studies will be required to define the exact mechanisms of HLA-mediated control of susceptibility and resistance to disease.

Genetic factors in pemphigus

Epidemiological studies performed in different ethnic populations and family studies, notably based on a partial phenotype of the autoimmune process, indicate that genetic factors are involved in the occurrence of pemphigus. However, the precise heritability remains uncertain in the absence of twin concordance rate studies. Among the different strategies available to identify genetic factors participating in autoimmune disease susceptibility, only population studies based on case-control design have been performed in pemphigus. These studies consistently showed that MHC locus, in particular HLA class II alleles, are associated with pemphigus vulgaris and pemphigus foliaceus. Other genes of the MHC locus may also participate in disease susceptibility as shown by studies using microsatellite markers across different regions of the MHC. It is likely that other non-MHC genes are involved in the pathogenesis of pemphigus. In particular, involvement of a polymorphic variant of desmoglein 1 gene was shown to be associated with pemphigus foliaceus and to interact in an epistatic manner with MHC class II genes to contribute to the autoimmune process. Other candidate genes to which a role can be assigned in the disease pathogenesis should be considered to design case-control or family-based association studies. Genome scan studies which require a large number of multiplex families to reach statistical power, should also be considered in the endemic form of pemphigus foliaceus because of the high number of familial cases.

Tumour necrosis factor-alpha polymorphism as one of the complex inherited factors in pemphigus

The aim of our study was to analyse a significance of tumour necrosis factor (TNF)-alpha promoter gene polymorphisms in relation to the HLA-DR locus in genetic predisposition to pemphigus. TNF-alpha gene polymorphisms in position -238 and -308 were identified using a modified polymerase chain reaction-restriction fragment length polymorphism method in 53 patients with pemphigus (38 with pemphigus vulgaris, 15 with pemphigus foliaceus) and 87 healthy controls. The HLA-DRB1 locus was typed using the polymerase chain reaction SSO method in all the patients and 152 population controls. Carriers of the TNF-alpha polymorphic -308 A allele were found to be more frequent in the pemphigus foliaceus group in comparison with the control group (odds ratio (OR) = 8.12; p = 0.0005). A significant association between HLA-DRB1*04 (OR = 3.86; pcor = 0.0001) and DRB1*14 (OR = 8.4; pcor = 0.0001) and pemphigus vulgaris was found. In this group of patients a decreased frequency of HLA-DRB1*07 (OR = 0.08; pcor = 0.006) was also identified. We have shown for the first time a positive association of TNF-alpha polymorphism in position -308 with pemphigus foliaceus.

Dissecting the associations of endemic pemphigus foliaceus (Fogo Selvagem) with HLA-DRB1 alleles and genotypes

Endemic pemphigus foliaceus (EPF) is a blistering skin disease characterized by autoantibodies against the desmosomal protein desmoglein 1. Genetic and environmental factors influence its pathogenesis. A total of 128 patients and 402 controls from an ethnically admixed Brazilian population were analyzed for associations by allele and genotype with HLA-DRB1. The alleles DRB1(*)0101, (*)0102, (*)0103, (*)0404, (*)0406, (*)0410, (*)1406 and (*)1601 are significantly more frequent among patients, while DRB1(*)0301, (*)0701, (*)0801, (*)1101, (*)1104 and (*)1402 are negatively associated to EPF. Results of association analysis with protein motifs composed of polymorphic amino-acid residues do not add much to comprehension of the molecular basis of the HLA-DRB1/EPF associations. Interactions between susceptible (SU), protective (PR) and neutral (NE) alleles clearly deviate from the codominant model. Protection is dominant, since the PR/NE and PR/PR genotypes are both equally (P=0.95) and strongly protective (odds ratio OR=0.07 and 0.05, respectively; P<10(-6) for both). The SU/SU genotype confers a higher (P=0.012) risk than genotype SU/NE (OR=8.7 and 4.0; P<10(-6) for both), an evidence of a semi-dominant effect of SU alleles relative to NE alleles. The OR for the SU/PR genotype (statistically close to 1) is consistent with semi-dominance between PR and SU alleles. Knowledge of these allelic interactions is relevant for understanding the mechanisms underlying autoimmune disease pathogenesis.

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.

Clinical, autoimmune, and genetic characteristics of adult-onset diabetic patients with GAD autoantibodies in Japan (Ehime Study)

OBJECTIVE

To characterize the clinical, autoimmune, and genetic features in Japanese adult-onset diabetic patients with GAD autoantibodies.

RESEARCH DESIGN AND METHODS

GAD autoantibodies (GADab) were screened in 4,980 diabetic patients with age of onset >20 years in the hospital-based Ehime Study, and the GADab-positive (GADab(+)) patients were then divided into two groups according to their insulin secretion and compared with nondiabetic subjects. The insulin-deficient state was defined as <0.33 nmol/l serum C-peptide (CPR) at 2 h postprandial or 6 min after a 1-mg glucagon load.

RESULTS

GADab was detected in 188 (3.8%) of the 4,980 diabetic patients tested. Of these patients, 72 (38.3%) were classified as insulin deficient, 97 (51.6%) were classified as non-insulin deficient, and 19 (10.1%) were unclassified. The GADab(+) insulin-deficient patients were characterized by young age at onset of diabetes, low BMI, low maximum BMI, and high levels of HbA(1c). The prevalence of IA-2 autoantibodies and thyrogastric autoantibodies in the GADab(+) insulin-deficient patients were significantly higher than those in the GADab(+) non-insulin-deficient patients (P < 0.05). GADab(+) patients with insulin deficiency had increased frequencies of HLA DRB1*0405-DQB1*0401, *0802-*0302, and *0901-*0303 haplotypes, whereas the frequency of only HLA DRB1*0405-DQB1*0401 was increased in the case of GADab(+) non-insulin-deficient patients. Of note is the fact that the GADab(+) non-insulin-deficient group did not differ from healthy control subjects with respect to type 1 diabetes protective haplotype HLA DRB1*1502-DQB1*0601. A total of 13% of the GADab(+) patients with diabetes had genotypes comprising the DRB1*1501-DQB1*0602 or *1502-*0601 and were characterized by old age at onset of diabetes, high BMI, resistance to the insulin-deficient state, low titer of GADab, and low frequency of other organ-specific autoantibodies.

CONCLUSIONS

We conclude that GADab(+) non-insulin-deficient patients differ from GADab(+) patients with insulin deficiency with respect to clinical characteristics, humoral autoimmunity to other organ-specific autoantibodies, as well as HLA class II genes.

Genotyping for HLA-A, B and C alleles in Japanese patients with pemphigus: prevalence of Asian alleles of the HLA-B15 family

BACKGROUND

There have been only limited reports on major histocompatibility complex class I antigens in pemphigus.

OBJECTIVES

To characterize HLA-A, B and C class I alleles by genotyping in Japanese patients with pemphigus, and to analyse the possible association of class I alleles with disease susceptibility within a relatively homogeneous ethnic population.

METHODS

Alleles of HLA-A, B and C, and DRB1 and DQB1 loci were fully determined in 51 Japanese patients with pemphigus.

RESULTS

Asian alleles of the HLA-B15 family, including the allele B*1507, which was significantly increased in comparison with normal controls, were prevalent in patients with pemphigus vulgaris (PV). The prevalence of B*15 alleles in patients with PV was not due to linkage disequilibrium with HLA-DR4 or DR14 alleles, which have been shown to confer strong susceptibility to PV across racial barriers. In contrast to the unique distribution of the HLA-B alleles, HLA-A and C alleles were unremarkable in patients with PV when compared with normal control subjects.

CONCLUSIONS

These results suggest that there may be differences in the ethnic concentrations of different HLA-B alleles in patients with PV.

Antidesmoglein autoantibodies in silicosis patients with no bullous diseases

BACKGROUND

Pemphigus is an autoimmune bullous disease characterized by the presence of antidesmoglein autoantibodies. However, the mechanism of its autoantibody production remains unknown. In previous reports, we have described rare cases of pemphigus and pemphigoid associated with silicosis. It is well known that during long-term silicosis, some autoimmune diseases, such as systemic sclerosis, systemic lupus erythematosus or rheumatoid arthritis, can occur.

OBJECTIVE

The aim of this study was to explore the presence of pemphigus or pemphigoid autoantibodies in silicosis patients without clinical bullous diseases or collagen diseases.

METHOD

The presence of pemphigus antibodies was examined in 54 silicosis patients with no associated bullous diseases, using immunofluorescence, the enzyme-linked immunosorbent assay (ELISA) for desmoglein 1 and 3, and immunoblotting methods. In the antibody-positive cases, HLA genotyping of peripheral lymphocytes was performed with PCR-RFLP.

RESULTS

Seven out of the 54 patients were found to be positive for pemphigus antibodies and 1 for bullous pemphigoid by immunofluorescence. In addition, by ELISA, 6 patients were found to be positive against the desmoglein 1 antigen, 2 against the desmoglein 3 antigen and 2 against both desmoglein 1 and desmoglein 3.

CONCLUSION

The results of the present study strongly suggest the occurrence of pemphigus and pemphigoid autoantibodies in patients with silicosis. It remains unclear whether such patients will develop an autoimmune bullous disease in the future. Accordingly, long-term follow-up of antibody-positive patients is required.

Polymorphisms of HLA-DR and -DQ genes in Japanese patients with bullous pemphigoid

Bullous pemphigoid (BP), an autoimmune skin disease of the elderly, is mediated by autoantibodies that bind to hemidesmosomes of epidermal basal cells. This study investigated BP-associated HLA-DR and -DQ genes among Japanese patients. We analyzed HLA-DR and -DQ genes among 23 Japanese BP patients based on the polymerase chain reaction-restriction fragment length polymorphism. Eighteen of these 23 patients (78%) carried at least one allele of HLA-DRB1*04 or DRB1*1101, with significant increases in HLA-DRB1*04 (*0403, *0406)/DQA1*0301/DQB1*0302 and DRB1*1101/DQA1*0505/DQB1*0302 haplotypes as well as the individual alleles DRB1*1101 and DQB1*0302 (corrected p < 0.05 for each comparison), when compared to control subjects. These data differ from the accepted DQB1*0301 (DQ7) association with the same disease among Caucasians. These findings indicate that different HLA class II haplotypes genetically influence susceptibility to BP among different ethnic groups. Our findings, together with previous reports on Caucasian patients with the pemphigoid group of bullous diseases, suggest that HLA-DRB1 molecules might participate in the regulation of autoimmune responses to BP antigens.