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

Ultrastructural skin alterations of healthy subjects with anti-desmoglein 1 antibodies in endemic areas to pemphigus foliaceus: A case series

Background

Endemic pemphigus foliaceus and endemic pemphigus vulgaris are autoimmune dermatologic disorders endemic to the Peruvian Amazon.

Objective

To determine the ultrastructural skin alterations of three healthy subjects with anti DSG-1 antibodies in areas endemic to pemphigus foliaceus and pemphigus vulgaris in the Peruvian Amazon.

Patients and methods

Case series carried out from data of three clinically healthy subjects positive to anti DSG-1 antibodies, from Peru. This study consists of a sub-analysis of data gathered in a previous study.

Results

Ultrastructural results are presented from the skin biopsies of three clinically healthy patients positive to anti-desmoglein 1 (DSG-1) antibodies. High Resolution Optical Microscopy (HROM) showed the absence of acantholysis. Transmission Electron Microscopy (TEM) showed the widening of intercellular space between keratinocytes, the presence of vacuoles in intercellular space with granular material and cytoplasmic vacuolization, loss of desmosome structure, loss of normal distribution among tonofilaments and lateral separation among cells in the stratum basale.

Conclusion

According to our results, healthy subjects that present anti-desmoglein 1 antibodies can develop ultrastructural alterations that are visible through transmission electron microscopy but not through conventional optical microscopy.

Role of Human Leukocyte Antigen Class II in Antibody-Mediated Skin Disorders

HLA class II molecules are key factors determining susceptibility to autoimmune disorders, and their role in immune-mediated skin conditions such as psoriasis has been extensively investigated. However, there is currently little understanding of their role in antibody-mediated skin diseases such as autoimmune blistering disorders. We researched the available literature using PubMed to narratively review the current knowledge on HLA associations in antibody-mediated blistering skin pathologies. Our results summarized the risk alleles that are identified in the literature, together with certain known protective alleles: in the pemphigus group, alleles HLA-DQB1*0503 and HLA-DRB1*0402 are most commonly associated with disease; in the pemphigoid group, the most studied allele is HLA-DQB1*0301; in epidermolysis bullosa acquisita, few genetic studies are available; in dermatitis herpetiformis, the association with haplotypes HLA-DQ2 and HLA-DQ8 is strongly established; finally, in linear IgA bullous disease, specific HLA alleles may be responsible for pediatric presentations. Our current pathogenic understanding of this group of disorders assigns a key role to predisposing HLA class II alleles that are able to bind disease autoantigens and therefore stimulate antigen-specific autoreactive T cells. The latter engage B lymphocytes that will produce pathogenic autoantibodies. The distribution of HLA alleles and their disease associations are variable across demographics, and an in-depth pathogenetic understanding is needed to support associations between HLA alleles and disease phenotypes. Additionally, in a personalized medicine approach, the identification of HLA alleles associated with the risk of disease may become clinically relevant in identifying susceptible subjects that should avoid exposure to known triggers, such as medication, when possible.

The landscape of the immunoglobulin repertoire in endemic pemphigus foliaceus

Introduction

Primarily driven by autoreactive B cells, pemphigus foliaceus (PF) is an uncommon autoimmune blistering skin disease of sporadic occurrence worldwide. However, PF reaches a prevalence of 3% in the endemic areas of Brazil, the highest ever registered for any autoimmune disease, which indicates environmental factors influencing the immune response in susceptible individuals. We aimed to provide insights into the immune repertoire of patients with PF living in the endemic region of the disease, compared to healthy individuals from the endemic region and a non-endemic area.

Methods

We characterized the B-cell repertoire in i) nontreated patients (n=5); ii) patients under immunosuppressive treatment (n=5); iii) patients in remission without treatment (n=6); and two control groups iv) from the endemic (n=6) and v) non-endemic areas in Brazil (n=4). We used total RNA extracted from peripheral blood mononuclear cells and performed a comprehensive characterization of the variable region of immunoglobulin heavy chain (IGH) in IgG and IgM using next-generation sequencing.

Results

Compared to individuals from a different area, we observed remarkably lower clonotype diversity in the B-cell immune repertoire of patients and controls from the endemic area (p < 0.02), suggesting that the immune repertoire in the endemic area is under geographically specific and intense environmental pressure. Moreover, we observed longer CDR3 sequences in patients, and we identified differential disease-specific usage of IGHV segments, including increased IGHV3-30 and decreased IGHV3-23 in patients with active disease (p < 0.04). Finally, our robust network analysis discovered clusters of CDR3 sequences uniquely observed in patients with PF.

Discussion

Our results indicate that environmental factors, in addition to disease state, impact the characteristics of the repertoire. Our findings can be applied to further investigation of the environmental factors that trigger pemphigus and expand the knowledge for identifying new targeted and more effective therapies.

Understanding CD4+ T cells in autoimmune bullous diseases

Autoimmune bullous diseases (AIBDs) are a group of life-threatening blistering diseases caused by autoantibodies that target proteins in the skin and mucosa. Autoantibodies are the most important mediator in the pathogenesis of AIBDs, and various immune mechanisms contribute to the production of these pathogenic autoantibodies. Recently, significant progress has been made in understanding how CD4⁺ T cells drive autoantibody production in these diseases. Here, we review the critical role of CD4⁺ T cells in the production of pathogenic autoantibodies for the initiation and perpetuation of humoral response in AIBDs. To gain an in-depth understanding of CD4⁺ T-cell pathogenicity, antigen specificity, and mechanisms of immune tolerance, this review covers comprehensive mouse and human studies of pemphigus and bullous pemphigoid. Further exploration of pathogenic CD4⁺ T cells will potentially provide immune targets for improved treatment of AIBDs.

A systematic review and meta-analysis of HLA class II associations in patients with IgG4 autoimmunity

Autoimmune diseases caused by pathogenic IgG4 subclass autoantibodies (IgG4-AID) include diseases like MuSK myasthenia gravis, pemphigus vulgaris or thrombotic thrombocytopenic purpura. Their etiology is still unknown. Polymorphisms in the human leukocyte antigen (HLA) gene locus, particularly in HLA-DRB1, are known genetic susceptibility factors for autoimmune diseases. We hypothesized a similar role for HLA polymorphisms in IgG4-AID and conducted a systematic review and meta-analysis with case-control studies on IgG4-AID based on MOOSE/ HuGENet guidelines. Genotype (G) and allele (A) frequencies of HLA-DQB1*05 (G: OR 3.8; 95% CI 2.44-5.9; p < 0.00001; A: OR 2.54; 95% CI 1.82-3.55; p < 0.00001) and HLA-DRB1*14 (G: OR 4.31; 95% CI 2.82-6.59; p < 0.00001; A: OR 4.78; 95% CI 3.52-6.49; p < 0.00001) and the HLA-DRB1*14-DQB1*05 haplotype (OR 6.3; 95% CI 3.28-12.09; p < 0.00001/OR 4.98; 95% CI 3.8-6.53; p < 0.00001) were increased while HLA-DRB1*13 (G: OR 0.48; 95% CI 0.34-0.68; p < 0.0001; A: OR 0.46; 95% CI 0.34-0.62; p < 0.00001) was decreased in IgG4-AID patients. In conclusion, the HLA-DQB1*05, HLA-DRB1*14 alleles and the HLA-DQB1*05-DRB1*14 haplotype could be genetic risk factors that predispose for the production of pathogenic IgG4 autoantibodies and the HLA-DRB1*13 allele may protect from IgG4 autoimmunity.

Variation in genes implicated in B-cell development and antibody production affects susceptibility to pemphigus

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease characterized by the presence of pathogenic autoantibodies against desmoglein 1, a component of intercellular desmosome junctions. PF occurs sporadically across the globe and is endemic in some Brazilian regions. Because PF is a B-cell-mediated disease, we aimed to study the impact of variants within genes encoding molecules involved in the different steps of B-cell development and antibody production on the susceptibility of endemic PF. We analysed 3,336 single nucleotide polymorphisms (SNPs) from 167 candidate genes genotyped with Illumina microarray in a cohort of 227 PF patients and 193 controls. After quality control and exclusion of non-informative and redundant SNPs, 607 variants in 149 genes remained in the logistic regression analysis, in which sex and ancestry were included as covariates. Our results revealed 10 SNPs within or nearby 11 genes that were associated with susceptibility to endemic PF (OR >1.56; p < 0.005): rs6657275*G (TGFB2); rs1818545*A (RAG1/RAG2/IFTAP);rs10781530*A (PAXX), rs10870140*G and rs10781522*A (TRAF2); rs535068*A (TNFRSF1B); rs324011*A (STAT6);rs6432018*C (YWHAQ); rs17149161*C (YWHAG); and rs2070729*C (IRF1). Interestingly, these SNPs have been previously associated with differential gene expression, mostly in peripheral blood, in publicly available databases. For the first time, we show that polymorphisms in genes involved in B-cell development and antibody production confer differential susceptibility to endemic PF, and therefore are candidates for possible functional studies to understand immunoglobulin gene rearrangement and its impact on diseases.

Beyond the HLA polymorphism: A complex pattern of genetic susceptibility to pemphigus

Pemphigus is a group of autoimmune bullous skin diseases that result in significant morbidity. As for other multifactorial autoimmune disorders, environmental factors may trigger the disease in genetically susceptible individuals. The goals of this review are to summarize the state of knowledge about the genetic variation that may affect the susceptibility and pathogenesis of pemphigus vulgaris and pemphigus foliaceus – both the endemic and the sporadic forms –, to compare and discuss the possible meaning of the associations reported, and to propose recommendations for new research initiatives. Understanding how genetic variants translate into pathogenic mechanisms and phenotypes remains a mystery for most of the polymorphisms that contribute to disease susceptibility. However, genetic studies provide a strong foundation for further developments in this field by generating testable hypotheses. Currently, results still have limited influence on disease prevention and prognosis, drug development, and clinical practice, although the perspectives for future applications for the benefit of patients are encouraging. Recommendations for the continued advancement of our understanding as to the impact of genetic variation on pemphigus include these partially overlapping goals: (1) Querying the functional effect of genetic variants on the regulation of gene expression through their impact on the nucleotide sequence of cis regulatory DNA elements such as promoters and enhancers, the splicing of RNA, the structure of regulatory RNAs and proteins, binding of these regulatory molecules to regulatory DNA elements, and alteration of epigenetic marks; (2) identifying key cell types and cell states that are implicated in pemphigus pathogenesis and explore their functional genomes; (3) integrating structural and functional genomics data; (4) performing disease-progression longitudinal studies to disclose the causal relationships between genetic and epigenetic variation and intermediate disease phenotypes; (5) understanding the influence of genetic and epigenetic variation in the response to treatment and the severity of the disease; (6) exploring gene-gene and genotype-environment interactions; (7) developing improved pemphigus-prone and non-prone animal models that are appropriate for research about the mechanisms that link genotypes to pemphigus. Achieving these goals will demand larger samples of patients and controls and multisite collaborations.

Human leukocyte antigen (HLA)-DRB1 allele polymorphisms and systemic sclerosis

Objectives: Human leukocyteantigen (HLA) is the most important gene for immune system regulation. Although studies have evaluated the association between HLA-DRB1 allele polymorphisms and systemic sclerosis (SSc), their results are still controversial. We performed a meta-analysis to assess the association of HLA-DRB1 alleles with risk of SSc.Methods: Electronic database were systematically searched for articles, a total of 11 case-control studies including 3268 cases and 5548 controls were analyzed. Odds ratio (ORs) and 95% confidence intervals were used to assess the association of HLA-DRB1 alleles with SSc. The relationship between SSc-related autoantibodies and DRB1 alleles was also analyzed.Results: In the overall analysis, four alleles (DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04) increased the risk of SSc; however, five alleles (DRB1*07, DRB1*11:01, DRB1*13, DRB1*13:01, and DRB1*14) had the opposite effect. Analysis of subgroups by ethnicity indicate that DRB1*11:01 and DRB1*13:01 confer a protective effect in Caucasians, while DRB1*11:04 was associated with a higher risk of SSc. For Asian, DRB1*13:02 was found to be a protective factor. In addition, the frequency of DRB1*11:04 alleles was significantly increased in ATA⁺ SSc patients compared with ATA^- SSc patients.Conclusion: DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04 were associated with the risk of SSc. Additionally, DRB1*11 and DRB1*11:04 were association with ATAs.

Region 1p13.2 including the RSBN1, PTPN22, AP4B1 and long non-coding RNA genes does not bear risk factors for endemic pemphigus foliaceus (fogo selvagem)

Pemphigus foliaceus (PF) is an autoimmune skin disease characterized by autoantibodies directed mainly against desmoglein-1. The purpose of this study was to determine whether differential susceptibility to endemic PF in Brazil (fogo selvagem) is associated with polymorphisms at the cytogenetic location 1p13.2. Four single nucleotide polymorphisms that together tag 28 SNPs on a segment of approximately 312,000 bp encompassing the protein-coding genes MAGI3, PHTF1, RSBN1, PTPN22, BCL2L15, AP4B1, DCLRE1B, the pseudogenes MTND5P20, RPS2P14 (AL133517.1) and the long non-coding RNA genes AL137856.1, and AP4B1-AS1 were used as markers for association analysis in a case-control study. Allele, genotype and haplotype frequencies of rs33996649, rs2476601, rs3789604 and rs3195954 were compared between patient and control samples. No significant association was found. Lack of association with rs2476601 of the PTPN22 gene agrees with previous results for pemphigus vulgaris and the Tunisian form of endemic pemphigus foliaceus. The other three SNPs had never been analysed before in any form of pemphigus. We conclude that variants in structural and regulatory sites of region 1p13.2 are not susceptibility factors for fogo selvagem. We suggest careful investigation of this genomic region in diseases that had been previously associated with PTPN22, since there are several other genes relevant for immune-mediated diseases located in 1p13.2.

Screening the full leucocyte receptor complex genomic region revealed associations with pemphigus that might be explained by gene regulation

Pemphigus foliaceus (PF) is a blistering autoimmune skin disease rare in most of the world but endemic in certain regions of Brazil. PF is characterized by the detachment of epidermal cells and the presence of autoantibodies against desmoglein 1. In previous studies, we have shown that genetic polymorphisms and variable expression levels of certain leucocyte receptor complex (LRC) genes were associated with PF. However, the role of the LRC on PF susceptibility remained to be investigated. Here, we analysed 527 tag single nucleotide polymorphisms (SNPs) distributed within the 1·5 Mb LRC. After quality control, a total of 176 SNPs were analysed in 229 patients with PF and 194 controls. Three SNPs were associated with differential susceptibility to PF. The intergenic variant rs465169 [odds ratio (OR) = 1·50; P = 0·004] is located in a region that might regulate several immune-related genes, including VSTM1, LILRB1/2, LAIR1/2, LILRA3/4 and LENG8. The rs35336528 (OR = 3·44; P = 0·009) and rs1865097 (OR = 0·57; P = 0·005) SNPs in LENG8 and FCAR genes, respectively, were also associated with PF. Moreover, we found four haplotypes with SNPs within the KIR3DL2/3, LAIR2 and LILRB1 genes associated with PF (P < 0·05), which corroborate previously reported associations. Thus, our results confirm the importance of the LRC for differential susceptibility to PF and reveal new markers that might influence expression levels of several LRC genes, as well as candidates for further functional studies.

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.

Sparking Fire Under the Skin? Answers From the Association of Complement Genes With Pemphigus Foliaceus

Skin blisters of pemphigus foliaceus (PF) present concomitant deposition of autoantibodies and components of the complement system (CS), whose gene polymorphisms are associated with susceptibility to different autoimmune diseases. To investigate these in PF, we evaluated 992 single-nucleotide polymorphisms (SNPs) of 44 CS genes, genotyped through microarray hybridization in 229 PF patients and 194 controls. After excluding SNPs with minor allele frequency <1%, out of Hardy-Weinberg equilibrium in controls or in strong linkage disequilibrium (r2 ≥ 0.8), 201 SNPs remained for logistic regression. Polymorphisms of 11 genes were associated with PF. MASP1 encodes a crucial serine protease of the lectin pathway (rs13094773: OR = 0.5, p = 0.0316; rs850309: OR = 0.23, p = 0.03; rs3864098: OR = 1.53, p = 0.0383; rs698104: OR = 1.52, p = 0.0424; rs72549154: OR = 0.55, p = 0.0453). C9 (rs187875: OR = 1.46, p = 0.0189; rs700218: OR = 0.12, p = 0.0471) and C8A (rs11206934: OR = 4.02, p = 0.0323) encode proteins of the membrane attack complex (MAC) and C5AR1 (rs10404456: OR = 1.43, p = 0.0155), a potent anaphylatoxin-receptor. Two encode complement regulators: MAC-blocking CD59 (rs1047581: OR = 0.62, p = 0.0152) and alternative pathway-blocking CFH (rs34388368: OR = 2.57, p = 0.0195). One encodes opsonin: C3 (rs4807895: OR = 2.52, p = 0.0239), whereas four encode receptors for C3 fragments: CR1 (haplotype with rs6656401: OR = 1.37, p = 0.0382), CR2 (rs2182911: OR = 0.23, p = 0.0263), ITGAM (CR3, rs12928810: OR = 0.66, p = 0.0435), and ITGAX (CR4, rs11574637: OR = 0.63, p = 0.0056). Associations reinforced former findings, regarding differential gene expression, serum levels, C3, and MAC deposition on lesions. Deregulation of previously barely noticed processes, e.g., the lectin and alternative pathways and opsonization-mediated phagocytosis, also modulate PF susceptibility. The results open new crucial avenues for understanding disease etiology and may improve PF treatment through additional therapeutic targets.

Spatial Distribution of Pemphigus Occurrence over Five Decades in Southeastern Brazil

Well-defined locations of pemphigus cases support the hypothesis of environmental factors' involvement in its etiopathogenesis; however, these foci have never been described using specialized geographical tools. This is the first report to geo-reference pemphigus cases in a high-prevalence Brazilian region using geographic information systems. We aimed to report the spatio-temporal behavior of pemphigus foliaceus (PF) and vulgaris (PV) in southeastern Brazil, over the last five decades to describe geographical clusters, as well as to characterize the land use in the city with the highest number of cases. Patients were identified from 1965 to 2014. Maps were developed using ArcGIS software and organized into decades from 1965 to 2014. Ribeirão Preto was identified as the city with the greatest number of cases. Land use was analyzed within a 2 km-buffer surrounding the residence of each patient. A total of 426 cases of pemphigus were identified. PF was the predominant form (285 cases); notwithstanding, the number of new cases of PV rose, overtaking the number of new cases of PF in the last decade studied. Agricultural area (42%) and exposed soil (33.2%) are the most predominant land uses in Ribeirão Preto surrounding patients' residences. This study shows high-confidence geographical foci of PF and PV, as well as provides evidence of an increase of both clinical forms over the last five decades. All cases of PV and PF are in proximity to rivers and agricultural areas which reinforce the hypothesis that environmental factors play a role in pemphigus etiopathogenesis.

Cytokine and Chemokines Alterations in the Endemic Form of Pemphigus Foliaceus (Fogo Selvagem)

INTRODUCTION

The endemic form (fogo selvagem-FS) of pemphigus foliaceus is an autoimmune disease characterized by the presence of IgG autoantibodies against desmoglein-1. Despite the array of findings, the role of chemokines and cytokines that dictate the immune response and disease outcome is still poorly investigated.

MATERIALS AND METHODS

Serum from 64 patients diagnosed with FS was used to draw and establish the levels of these molecules on this disease and establish the levels of these molecules with the severity of FS, and influence of treatment.

RESULTS

In comparison to healthy subjects, FS patients, newly diagnosed and still without therapeutic intervention, had higher levels of IL-22 and CXCL-8, and reduced levels of IFN-γ, IL-2, IL-15, and CCL-11. Furthermore, treatment using immunosuppressant drugs augmented the production of IFN-γ, IL-2, CCL-5, and CCL-11 besides reducing the levels of IL-22 and CXCL-10. Immunosuppressive therapy seemed to have long-lasting effects on the production of higher amounts of IFN-γ, IL-2, and CCL-5, besides keeping lowered the levels of IL-22 in remission FS patients.

CONCLUSION

Taken together, our findings suggest a putative role of IL-22 in the pathogenesis of FS. Finally, data presented here may contribute for better understanding the immune aspects that control disease outcome.

Data on HLA class I/II profile in Brazilian pemphigus patients

Pemphigus are blistering autoimmune diseases related with genetic and environmental factors. Here we describe HLA genotyping in pemphigus patients. First, we review the HLA class I/II data on pemphigus reported in Brazilian samples and then present the HLA class I (-A, -B, -C) and class II (-DRB1, -DQA1, -DQB1) alleles related to susceptibility/resistance to pemphigus by comparing 86 patients with pemphigus foliaceus, 83 patients with pemphigus vulgaris, and 1592 controls from the northeastern region of the state of São Paulo, Southeastern Brazil. The data presented here are related to the manuscript “Differential HLA class I and class II associations in Pemphigus Foliaceus and Pemphigus Vulgaris patients from a prevalent Southeastern Brazilian region” Brochado et al. (2016) [1].

Differential HLA class I and class II associations in pemphigus foliaceus and pemphigus vulgaris patients from a prevalent Southeastern Brazilian region

Genetic factors, particularly those concerning HLA class II, have been associated with the pathogenesis of pemphigus. Taking advantage of an area where pemphigus foliaceus (PF) and pemphigus vulgaris (PV) are prevalent in the northeastern region of the state of São Paulo, Southeastern Brazil, we have studied the HLA class I (A, B and C) and class II (DRB1 and DQA1/DQB1) profiles in 86 and 83 patients with PF and PV, respectively, as compared with 1592 controls from the same region. Among all the HLA alleles described herein, the more prevalent susceptibility alleles for PF were HLA-A*11, 33, -B*14; -DRB1*01:01, *01:02; -DQA1*01:02; and -DQB1*05:01. In PV patients, the HLA-B*38; -C*12; -DRB1*04:02, *08:04, *14:01, *14:04; -DQA1*03:01; and -DQB1*03:02 and *05:03 alleles were associated with susceptibility. The HLA-DRB1*01:02 allele and the HLA-DRB1*01-DQA1*01-DQB1*05 haplotype in PF patients and the HLA-DRB1*04:02 and *14:01 alleles and the HLA-DRB1*14-DQA1*01-DQB1*05 haplotype in PV patients were related with the highest etiologic fraction values. Distinct genetic patterns and not yet described HLA susceptibility/protection alleles/haplotypes profiles have been observed in this series. Our findings corroborate the differential genetic markers in PF and PV in an area where pemphigus is prevalent but not yet reported.

Family study of monozygotic twins affected by pemphigus vulgaris

Rare are the family studies that include siblings affected by pemphigus vulgaris (PV) and in whom HLA class II alleles are related. HLA-DR and -DQ genotyping and profiling of antibodies against desmogleins (Dsg) 1 and Dsg3 were performed in ten members of a family including monozygotic twins affected by PV. The twin sisters were heterozygotes; they presented the haplotypes most commonly associated with increased susceptibility to PV (DRB1∗04:02-DQA1∗03:01-DQB1∗03:02 and DRB1∗14:04-DQA1∗01:01-DQB1∗05:03). Their parents and five siblings had only one or none of these two haplotypes in combination with the alleles or haplotypes associated with resistance to PV (DRB1∗07:01-DQA1∗02:01-DQB1∗02:02 and DRB1∗13:01-DQA1∗01:03-DQB1∗06:03). Only the monozygotic twins presented IgG antibodies against both Dsg1 and Dsg3. According to our knowledge based on a review of published literature on the topic, this is the first report of PV affecting monozygotic twins.

Differential gene expression levels might explain association of LAIR2 polymorphisms with pemphigus

The leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1) is a collagen-binding inhibitory receptor important for the regulation of immune responses, expressed on the majority of peripheral blood mononuclear cells (PBMC). LAIR-2 is a soluble homolog that antagonizes LAIR-1 inhibitory function by binding the same ligands. We sought to investigate whether LAIR1 and LAIR2 single nucleotide polymorphisms (SNP) are associated with differential mRNA expression levels. We analyzed 14 SNPs of LAIR1 (6) and LAIR2 (8) by mass spectrometry-based genotyping and extracted mRNA from PBMC of 177 healthy subjects, followed by quantitative assays. Four SNPs of LAIR1 and two SNPs of LAIR2 mark differential mRNA levels in healthy individuals. To verify the biological relevance of these findings, we analyzed additional 515 individuals (282 patients and 233 controls) to check if LAIR1 and LAIR2 differential mRNA expression could be related to susceptibility to pemphigus foliaceus (PF), an autoimmune blistering skin disease endemic in Brazil. Two LAIR1 variants (rs56802430 G, OR = 1.52, p = 0.0329; rs11084332 C, OR = 0.57, p = 0.0022) and one LAIR2 (rs2287828 T+, OR = 1.9, p = 0.0097) contribute to differential susceptibility to PF. Furthermore, we demonstrate interactions among four LAIR2 SNPs (rs2042287, rs2287828, rs2277974 and rs114834145). A haplotype harboring these SNPs is strongly associated with higher LAIR2 mRNA levels (4.5-fold, p = 0.0069) and with higher susceptibility to PF (OR = 4.02, p = 0.0008). We suggest that LAIR1 and LAIR2 genetic variants are associated with regulation of gene expression and variable PF susceptibility, and show indirect association of LAIR2 differential mRNA expression with PF pathogenesis. Our data demonstrate how this relatively unknown disease can add invaluable knowledge regarding the role of LAIR1 and LAIR2 in immune responses.

Pemphigus is associated with KIR3DL2 expression levels and provides evidence that KIR3DL2 may bind HLA-A3 and A11 in vivo

Although HLA-A3 and A11 have been reported to be ligands for KIR3DL2, evidence for any in vivo relevance of this interaction is still missing. To explore the functional importance of KIR3DL2 allelic variation, we analyzed the autoimmune disease pemphigus foliaceus, previously associated (lower risk) with activating KIR genes. KIR3DL2*001 was increased in patients (odds ratio (OR) = 2.04; p = 0.007). The risk was higher for the presence of both KIR3DL2*001 and HLA-A3 or A11 (OR = 3.76, p = 0.013), providing the first evidence that HLA-A3 and A11 may interact with KIR3DL2 in vivo. The nonsynonymous single nucleotide polymorphism 1190T (rs3745902) was associated with protection (OR = 0.52, p = 0.018). This SNP results in a threonine-to-methionine substitution. Individuals who have methionine in this position exhibit a lower percentage of KIR3DL2-positive natural killer (NK) cells and also lower intensity of KIR3DL2 on expressing natural killer cells; additionally, we show that the expression of KIR3DL2 is independent of other killer cell immunoglobulin-like receptors. Pemphigus foliaceus is a very unique complex disease strongly associated with immune-related genes. It is the only autoimmune disease known to be endemic, showing a strong correlation with environmental factors. Our data demonstrate that this relatively unknown autoimmune disease may facilitate understanding of the molecular mechanisms of KIR3DL2 ligand recognition.

Genome-wide gene expression profiling reveals unsuspected molecular alterations in pemphigus foliaceus

Pemphigus foliaceus (PF) is a complex autoimmune disease characterized by bullous skin lesions and the presence of antibodies against desmoglein 1. In this study we sought to contribute to a better understanding of the molecular processes in endemic PF, as the identification of factors that participate in the pathogenesis is a prerequisite for understanding its biological basis and may lead to novel therapeutic interventions. CD4+ T lymphocytes are central to the development of the disease. Therefore, we compared genome-wide gene expression profiles of peripheral CD4+ T cells of various PF patient subgroups with each other and with that of healthy individuals. The patient sample was subdivided into three groups: untreated patients with the generalized form of the disease, patients submitted to immunosuppressive treatment, and patients with the localized form of the disease. Comparisons between different subgroups resulted in 135, 54 and 64 genes differentially expressed. These genes are mainly related to lymphocyte adhesion and migration, apoptosis, cellular proliferation, cytotoxicity and antigen presentation. Several of these genes were differentially expressed when comparing lesional and uninvolved skin from the same patient. The chromosomal regions 19q13 and 12p13 concentrate differentially expressed genes and are candidate regions for PF susceptibility genes and disease markers. Our results reveal genes involved in disease severity, potential therapeutic targets and previously unsuspected processes involved in the pathogenesis. Besides, this study adds original information that will contribute to the understanding of PF's pathogenesis and of the still poorly defined in vivo functions of most of these genes.

Cytokine gene polymorphisms in Tunisian endemic pemphigus foliaceus: a possible role of il-4 variants

Polymorphism in the genes of TH2 cytokines and/or theirs receptors can influence serum cytokine levels in and the switch to the pathologic IgG4 auto-antibodies. In order to underline the role of these genes in the aethiopathogenesis of Pemphigus Foliaceus, we conduct a familial and a case control studies including 80 Tunisian patients, 147 related subjects and 160 matched healthy controls. We investigated, by PCR-RFLP technique, seven nucleotide polymorphisms: rs2243250 in promoter region of IL4 gene, rs47877948, rs3024530 and rs30246223 in the IL4R gene, rs1881457and rs205412 SNPs in IL13 gene and rs535036 in IL13RA2 gene. After Bonferroni adjustment, T allele and the TT genotype of IL4-590 were significantly increased in the PF patients group compared to healthy controls. This association was confirmed by the family study. Interestingly, the serum IL-4 levels were significantly increased in patients with the TT genotype compared to CT or CC genotypes. Interestingly, the IL4/IL13:T-A-C haplotype exhibited a significant effect on PF susceptibility. In addition, a significant gene-gene interaction between the IL4/IL4R (TACA) significantly increases in PF patients as compared to controls. These findings assess the role of the IL4/IL4R axis in the aethiopathogenesis of Tunisian endemic PF by the induction of a high transcriptional activity which could enhance the T-cell balance and inducing immunoglobulin isotype switching.

Activating KIR and HLA Bw4 ligands are associated to decreased susceptibility to pemphigus foliaceus, an autoimmune blistering skin disease

The KIR genes and their HLA class I ligands have thus far not been investigated in pemphigus foliaceus (PF) and related autoimmune diseases, such as pemphigus vulgaris. We genotyped 233 patients and 204 controls for KIR by PCR-SSP. HLA typing was performed by LABType SSO reagent kits. We estimated the odds ratio, 95% confidence interval and performed logistic regression analyses to test the hypothesis that KIR genes and their known ligands influence susceptibility to PF. We found significant negative association between activating genes and PF. The activating KIR genes may have an overlapping effect in the PF susceptibility and the presence of more than three activating genes was protective (OR = 0.49, p = 0.003). A strong protective association was found for higher ratios activating/inhibitory KIR (OR = 0.44, p = 0.001). KIR3DS1 and HLA-Bw4 were negatively associated to PF either isolated or combined, but higher significance was found for the presence of both together (OR = 0.34, p<10⁻³) suggesting that the activating function is the major factor to interfere in the PF pathogenesis. HLA-Bw4 (80I and 80T) was decreased in patients. There is evidence that HLA-Bw4(80T) may also be important as KIR3DS1 ligand, being the association of this pair (OR = 0.07, p = 0.001) stronger than KIR3DS1-Bw4(80I) (OR = 0.31, p = 0.002). Higher levels of activating KIR signals appeared protective to PF. The activating KIR genes have been commonly reported to increase the risk for autoimmunity, but particularities of endemic PF, like the well documented influence the environmental exposure in the pathogenesis of this disease, may be the reason why activated NK cells probably protect against pemphigus foliaceus.

Pemphigus Foliaceus Associated with Psoriasis during the Course of Narrow-Band UVB Therapy: A Simple Coincidence?

Although psoriasis and bullous diseases are considered to be completely different disease entities, the literature has reported a few cases of psoriasis associated with bullous diseases, most of which are bullous pemphigoid. In limited cases, pemphigus foliaceus has also been reported in association with psoriasis. In most of them, pemphigus lesions usually developed on an untreated patient with a chronic history of psoriasis. Herein, we report a case of 53-year-old male with a chronic history of psoriasis who first developed generalized erosive lesions after 26 cycles of narrow-band ultraviolet B (NBUVB) therapy. A diagnosis of pemphigus foliaceus was made based on skin biopsy and direct immunofluorescence assay. Pemphigus lesions were well controlled with combination therapy of oral steroid and azathioprine. This is the first case where pemphigus foliaceus co-occurred with psoriasis during NBUVB therapy.

Peanut-allergic subjects and their peanut-tolerant siblings have large differences in peanut-specific IgG that are independent of HLA class II

We enrolled 53 peanut-allergic subjects and 64 peanut-tolerant full siblings, measured peanut-specific IgG and IgE, determined HLA class II at high resolution, and analyzed DRB1 alleles by supertypes. Peanut-specific IgG and IgE were elevated in the peanut-allergic subjects (p<0.0001) but did not stratify with HLA alleles, haplotypes, or supertypes. There were no significant differences in HLA class II between the peanut-allergic and peanut-tolerant siblings but there was an increased frequency of DRB1*0803 in both sets of siblings compared to unrelated controls (p(c)=4.5×10⁻⁹). Furthermore, we identified 14 sibling pairs in which the peanut-allergic and the peanut-tolerant siblings have identical HLA class II and again found an elevation of anti-peanut IgG in the peanut-allergic subjects (p<0.0001). In conclusion, although DRB1*0803 may identify a subset of families with increased risk of peanut allergy, differences in peanut-specific immunoglobulin production between peanut-allergic subjects and their peanut-tolerant siblings are independent of HLA class II.

CTLA4CT60 gene polymorphism is not associated with differential susceptibility to pemphigus foliaceus

Pemphigus foliaceus is an organ-specific autoimmune disease characterized by autoantibodies against the extracellular region of desmoglein 1, a protein that mediates intercellular adhesion in desmosomes. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a key negative regulator of the T cell immune response, playing an important role in T cell homeostasis and maintenance of peripheral tolerance. Polymorphisms in the CTLA4 gene have been associated with autoimmune diseases and the functional CT60 single nucleotide polymorphism (rs3087243, also named 6230G > A) has been proposed to be a casual variant in several of these diseases. The aim of this study was to ascertain whether this polymorphism is associated with inter-individual variation in susceptibility to pemphigus foliaceus. The population sample in this case-control association study comprised 248 patient and 367 controls. We did not found a significant association of pemphigus foliaceus with the CT60 variants. We conclude that the CTLA4CT60 polymorphism is not an important factor for pemphigus foliaceus pathogenesis in the population analyzed.

A new variant of endemic pemphigus foliaceus in El-Bagre, Colombia: the Hardy-Weinberg-Castle law and linked short tandem repeats

Background:

We reported a new variant of endemic pemphigus foliaceus in El Bagre, Colombia.

Aims:

Our study performed Complex Segregation Analysis (CSA) and short tandem repeats to discriminate between environmental and/or genetic factors in this disorder.

Materials and Methods:

The CSA analysis was carried out according to the unified model, implemented using the transmission probabilities implemented in the computer program POINTER, and evaluated by using a software package for population genetic data analysis (GDA), Arlequin. We performed pedigree analyses by using Cyrillic 2.1 software, with a total of 30 families with 50 probands (47 males and 3 females) tested. In parallel to the CSA, we tested for the presence of short tandem repeats from HLA class II, DQ alpha 1, involving the gene locus D6S291 by using the Hardy-Weinberg- Castle law.

Results

Our results indicate that the best model of inheritance in this disease is a mixed model, with multifactorial effects within a recessive genotype. Two types of possible segregation patterns were found; one with strong recessive penetrance in families whose phenotype is more Amerindian-like, and another of possible somatic mutations.

Conclusion:

The penetrance of 10% or less in female patients 60 years of age or older indicates that hormones could protect younger females. The greatest risk factor for men being affected by the disorder was the NN genotype. These findings are only possible due to somatic mutations, and/or strong environmental effects. We also found a protective role for two genetic loci (D6S1019 AND D6S439) in the control group.

Immunogenetics of pemphigus: An update

Pemphigus are rare but informative models of organ-specific autoimmune diseases, resulting from the interplay of environmental, genetic and stochastic factors. There are many arguments to consider that pemphigus have a genetic basis involving, as many other autoimmune diseases, several different genes with additive or synergistic effects. So far, the unique strategy used to identify the contributive loci has been direct analysis of candidate genes through conventional case-control association studies. The major histocompatibility complex in particular the class II locus was demonstrated to be associated with pemphigus with a high rate of replicability. The progresses in the understanding of pemphigus physiopathology and the development of new molecular tools offer new perspectives to unveiled the genetic basis of this group of autoimmune blistering diseases, as shown by recent studies of candidate genes expressed at different levels of the autoimmune process.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

Prédisposition aux infections des malades ayant un pemphigus

INTRODUCTION

The relation between pemphigus and infection is complex. The aim of this work was to determine the frequency and impact of infection as well as the factors associated with it among our patients with pemphigus.

METHODS

This retrospective case series examined records of patients with pemphigus admitted to the dermatology unit of Ibn Sina University Hospital of Rabat between 1989 and 2004. We compared the patients with and without infections as well as the patients with and without severe bacterial infections according to patient profile and outcome. The principal outcome measure was death and the secondary measure, duration of hospitalization.

RESULTS

Of the 141 patients with pemphigus included in our study, 68% developed an infection. Infections were bacterial in 52% of cases, fungal in 50%, herpetic in 19% and parasitic in 1.5%. They were associated with diabetes mellitus and immunosuppressive drugs. Severe bacterial infection was frequent in patients with diabetes and rare in those treated with corticosteroids or with pemphigus foliaceous. Death occurred significantly more often among infected subjects (p=0.01), especially those with severe bacterial infections (p<0.001). Hospitalization was slightly longer among patients with infections (p=0.01) but shorter in cases of severe bacterial infections (p=0.004).

DISCUSSION

Our study confirms the predisposition to all types of infection among patients with pemphigus, as well as the undeniable role its treatment plays in promoting infection. Severe bacterial infections were most often contracted before hospitalization. The literature reports a wide variety of infections, with pemphigus-herpes documented most often. Prevention and management require hygienic measures as well as early diagnosis and treatment of pemphigus and infections. Preventive treatment may be considered, but studies are needed to define the patients who might benefit from it.

HLA-DRB1*0402 haplotypes without DQB1*0302 in Venezuelan patients with pemphigus vulgaris

The two basic forms of autoimmune intraepidermal blistering diseases, pemphigus vulgaris (PV) and pemphigus foliaceus (PF), affect different layers of the skin, have different symptoms and target different antigens. We have defined human leukocyte antigen (HLA)-DRB1-DQB1 alleles and haplotypes in a case-control study of 66 non-Jewish patients attending a public reference Hospital over the past 10 years. The control group consisted of 101 matched individuals tested also by medium to high-resolution polymerase chain reaction-sequence-specific oligonucleotide with primers and probes from the 12th and 13th International Histocompatibility Workshop. Patients and controls were descendants of three-generation individuals born in the country. Among the patients, 49 had PV, 50% showed predominantly mucosal involvement, 50% showed predominantly the cutaneous clinical phenotype and 17 had PF. Statistically significant HLA-DR frequency differences between patients with PV and controls were found only for DRB1*0402 and DRB1*1401 [odds ratio (OR) = 27.22, confidence interval (CI) 94.7-7.82, P= 1.1 x 10(-14) and OR = 46.56, CI 801.4-2.70 P= 7.5 x 10(-6), respectively]. Both alleles were also increased in the patients with PF compared with the controls (OR = 7.0, P= 0.038 and OR = 21.64, P= 0.009, respectively), but the significance of the difference did not resist Bonferroni correction. Haplotype analysis showed that DRB1*0402 was always present with DQB1*0302 and DRB1*1401 with DQB1*0503, but no independent effect of the DQB1*0302 in the former haplotype was evident. Our results support the hypothesis that the DRB1*0402 without DQB1*0302 is the most relevant HLA-DRB1 allele responsible for the pathogenesis of pemphigus in Venezuelan patients with PV and discard the DQB1*0302 influence observed in other populations.

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.

Polymorphism of the promoter region and exon 1 of the CTLA4 gene in endemic pemphigus foliaceus (fogo selvagem)

Endemic pemphigus foliaceus (EPF) is an autoimmune bullous skin disease characterized by acantholysis and antibodies against a desmosomal protein, desmoglein 1. Genetic and environmental factors contribute to development of this multifactorial disease. HLA class II and some cytokine gene polymorphisms are the only genetic markers thus far known to be associated with susceptibility to or protection from EPF. The cytotoxic T-lymphocyte antigen-4 gene (CTLA4) encodes a key immunoreceptor molecule that regulates and inhibits T-cell proliferation. It participates in the regulatory process controlling autoreactivity and therefore has been considered a strong candidate gene in autoimmune diseases. In the search for genes that might influence EPF pathogenesis, we analyzed variants of the CTLA4 gene in a sample of 118 patients and 291 controls from a Brazilian population. This is the first study investigating the possible role of polymorphisms of the 2q33 chromosomal region in differential susceptibility to pemphigus foliaceus. Promoter region and exon 1 single nucleotide polymorphisms -318 (C,T) and 49 (A,G) were genotyped using sequence-specific oligonucleotide probes after amplification by the polymerase chain reaction. The allelic and genotypic frequencies did not differ significantly between the patient and the control groups (-318T: 9.8 and 10.9%, 49G: 33.0 and 35.2% were the allelic frequencies in patients and controls, respectively). In addition, no significant difference was found when the patient and control population samples were stratified by the presence of HLA-DRB1 alleles. We conclude that the CTLA4 -318 (C,T) and 49 (A,G) polymorphisms do not play a major role in EPF development.

No evidence for association of the TP53 12139 and the BAX-248 polymorphisms with endemic pemphigus foliaceus (fogo selvagem)

Pemphigus foliaceus (PF) is an autoimmune bullous epidermal disease, characterized by autoantibodies specific to the desmosomal protein desmoglein 1 (dsg1) and by acantholysis, the rupture of the cellular junctions among keratinocytes. Known also as fogo selvagem (wild fire) in Brazil, the disease has distinct epidemiological characteristics, being endemic in certain regions of South America. It is a multifactorial (complex) disease, with oligo- or polygenic disease susceptibility. In view of the previously reported evidences of a role for apoptosis dysregulation in pemphigus pathogenesis, we hypothesized that genetic variants of molecules participating in apoptosis may contribute to interindividual variation of susceptibility to PF. The TP53 12139(G,C) and the BAX-248(G,A) single nucleotide polymorphisms (SNP) were analysed in a genetic association study. The allelic, genotypic and allele carrier frequencies for these SNPs did not differ statistically between the patient and the control groups, for both the Euro- and the Afro-Brazilian population strata. The results of this study lead us to conclude that, although the TP53 and BAX alleles analysed differ functionally, this variation does not alter the functionality of the molecules in a way that would interfere with the development of the disease.

Antígenos de histocompatibilidade humanos e dermatologia: da pesquisa para a prática clínica

A participação do sistema de histocompatibilidade humano (HLA: human leukocyte antigens) na patogênese das doenças auto-imunes é bem conhecida. Situado no braço curto do cromossomo 6, o sistema HLA se destaca por seu polimorfismo e por sua capacidade de conferir susceptibilidade ou proteção a diferentes enfermidades. Em Dermatologia, esse sistema desempenha papel importante na patogenia e história natural de várias doenças. A força e o tipo de associação variam com a dermatose e, algumas vezes, com o grupo étnico-racial estudado. O surgimento de métodos moleculares para tipificação dos alelos HLA e as recentes atualizações de sua nomenclatura têm contribuído para o melhor entendimento desse sistema. Infelizmente, essas informações não têm sido veiculadas de maneira adequada na literatura clínica, o que dificulta o entendimento da associação do HLA com as doenças cutâneas. Nesta revisão, são discutidos alguns aspectos do sistema HLA, métodos de detecção, nomenclatura e sua associação com vitiligo, pênfigo, psoríase, lúpus eritematoso, escabiose, leishmaniose cutânea, hanseníase, paracoccidioidomicose e dermatite atópica.

Pemphigus foliaceus and desmoglein 1 gene polymorphism: is there any relationship?

Transmembrane proteins of the cadherin superfamily, the desmogleins and desmocollins, mediate intercellular adhesion in desmosomes. Autoantibodies to desmoglein 1 (dsg1) are a hallmark of pemphigus foliaceus (PF), a disease characterized by skin blistering resulting from keratinocyte cell detachment. The etiology and pathogenesis of this disease remain poorly understood; however, genetic susceptibility is clearly involved. The aim of this study was to verify if genetic variants of dsg1 influence susceptibility/resistance to endemic PF (fogo selvagem). Two single nucleotide polymorphisms (SNPs) were analyzed: 809 (C,T), a synonymous variation, and 1660 (A,C), a tyrosine<-->serine variation in the fifth extracellular domain. Allelic, haplotypic and genotypic frequencies did not differ significantly between the patient (n=134) and the control (n=227) population samples. Moreover, there is no evidence of interaction between the DSG1 and the HLA-DRB1 and IL6 genes, whose alleles had been found associated with differential susceptibility to PF. The results of this study agree with the described and predicted B- and T-cell epitopes of the dsg1 molecule, which seemingly are not affected by the allelic variation. We conclude that genetic diversity of the autoantigen dsg1 is not a major factor for PF pathogenesis in the Brazilian population.

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.

Cytokine gene polymorphisms in endemic pemphigus foliaceus: a possible role for IL6 variants

Endemic pemphigus foliaceus (EPF) is a complex autoimmune disease characterized by the presence of antibodies against desmoglein 1, which lead to the loss of adhesion among keratinocytes (acantholysis). Variants of HLA class II genes have been the only genetic factors found to modulate susceptibility to EPF. This study aims at investigating the influence of cytokine genetic variants in the pathogenesis of EPF, since they may affect the expression levels of these immunomodulatory molecules. The sample included 168 patients and 189 controls and was comprised of mostly Caucasoids and Mulattos. The approach consisted of a case-control association study and the alleles were identified by mismatched PCR-RFLP. No associations were found with variants of IL1A, IL1B, IL1RN, IL4R and IL10. There was a weak negative association with the haplotype -1082G -592C (OR=0.49) of the IL10 gene in Mulattos. In regard to polymorphism -590 of the IL4 gene, a positive association with the T/T genotype (OR=2.71) and a negative association with the C variant (OR=0.37) were found. Associations with IL6 -174 variants suggest that the C/C genotype has a protective effect (OR=0.13) while carriers of the G allele are more susceptible (OR=7.66) to EPF.

Polymorphisms within the tumor necrosis factor and lymphotoxin-alpha genes and endemic pemphigus foliaceus--are there any associations?

The purpose of this study was to analyze the possible influence of the TNF and LTA loci polymorphisms on the susceptibility/resistance to endemic pemphigus foliaceus, also named fogo selvagem (FS), an autoimmune disease characterized by blisters due to acantholysis of the superficial-most epidermal cells. Autoantibodies, mainly of the IgG4 subclass, are directed against a desmosomal glycoprotein known as desmoglein 1. FS shares clinical, histological and immunological features with nonendemic pemphigus foliaceus. Most residents of the endemic regions do not develop the disease, and familial clustering has been documented, suggesting that host factors play a role in susceptibility. In fact, strong positive and negative associations with HLA class II genes have been reported. The TNF and LTA genes are located in the class III region of the Human Major Histocompatibility Complex. Their location, the function of their products, which are cytokines and pluripotent immunomodulators, as well as their genetic variability make them candidate genes for complex diseases with an altered immune response. A total of 162 patients and 191 controls were enrolled in this study. No significant associations were found with any one of the three LTA single nucleotide polymorphisms (SNP) analyzed (at nucleotides 249, 365, 720), nor with the TNF SNP located at positions -863 and -308. The frequency of allele TNF*238A was slightly decreased in patients (OR = 0.45). In conclusion, the results of this study indicate that genetic variability of the TNF and LTA genes does not play a major role in susceptibility/resistance to pemphigus foliaceus.