Role of MHC Class II genes in the pathogenesis of pemphigoid

HLA-Cw6 Polymorphism in Autoimmune Blistering Diseases

Autoimmune blistering diseases of the pemphigus and pemphigoid groups are immune-mediated disorders due to circulating pathogenetic autoantibodies. Multiple human leukocyte antigen (HLA) genes have been associated with predisposition to these disorders. HLA-Cw6 is involved in antigen presentation processes and has been linked to psoriasis. The aim of our study was to investigate the association between the presence of the HLA-Cw6 allele and susceptibility to pemphigus vulgaris and bullous pemphigoid. A genetic study in vitro with a cross-sectional design was performed enrolling forty patients with pemphigus vulgaris and forty patients with bullous pemphigoid. The detection of HLA-Cw6 was performed through the EUROArray test on DNA obtained from whole blood samples. The polymorphism was detected in 3/40 genotypes in the pemphigus vulgaris group and in 4/40 genotypes of patients with bullous pemphigoid, unveiling a non-statistically significant different frequency in pemphigus (p = 0.6368) and in pemphigoid (p = 0.62) compared to the reference frequency from the literature of 0.086. Further research is needed to better investigate the role of HLA-Cw6 in immune-mediated diseases and to identify novel genetic markers associated with susceptibility to autoimmune blistering diseases and with disease severity and response to immunosuppressive therapies.

Ocular Mucous Membrane Pemphigoid: The Effect of Risk Factors at Presentation on Treatment Outcomes

PURPOSE

Analyze the influence of risk factors at presentation in the long-term immunosuppressive therapy (IMT) outcomes of ocular mucous membrane pemphigoid (OMMP).

DESIGN

Retrospective multicenter study.

PARTICIPANTS

Patients with OMMP seen at the Duke Eye Center, Tecnologico de Monterrey, and Hospital Clinic of Barcelona from 1990 to 2022.

METHODS

Data at presentation on demographics, direct immunofluorescence, ocular findings, sites of extraocular manifestations (EOMs), and previous treatments in patients with a clinical or laboratory diagnosis of OMMP, were analyzed with multivariable analysis and Kaplan-Meier plots to identify factors associated with adverse outcomes.

MAIN OUTCOME MEASURES

(1) Inflammatory control (no conjunctival inflammation in both eyes at 3 months on IMT); (2) relapse (new-onset inflammation after absolute control in either eye); (3) progression (≥ 1 cicatrizing stage progression in either eye); and (4) vision loss (≥ 2 Snellen lines).

RESULTS

A total of 117 patients (234 eyes), 61% (71/117) of whom were women, with a mean age of 66.6 (SD: 12.4) years (range: 37-97 years) and median follow-up of 34 months (interquartile range: 16-66 months; range: 3-265 months), were enrolled. Inflammatory control was achieved in 57% of patients (67/117), with high-risk EOM (HR-EOM), including esophageal, nasopharyngeal, and/or genital involvement (adjusted odds ratio [aOR]: 12.51; 95% confidence interval [CI]: 2.61-59.99; P = 0.002) and corneal scarring (aOR: 3.06; 95% CI, 1.15-8.14; P = 0.025), as significant risk factors for persistent inflammation. Disease relapse, progression, and vision loss occurred in 20% of patients (23/117), 12% of patients (14/117), and 27% of patients (32/117), respectively. Baseline corneal scarring was a risk factor for relapse (adjusted hazard ratio: 4.14; 95% CI: 1.61-10.62; P = 0.003), progression (aOR: 11.46; 95% CI: 1.78-73.75; P = 0.010), and vision loss (aOR: 3.51; 95% CI: 1.35-9.10; P = 0.010). HR-EOM was associated with stage progression (aOR, 34.57; 95% CI, 6.57-181.89; P<0.001) and vision loss (aOR, 8.42; 95% CI, 2.50-28.42; P = 0.001). No significant differences were found between IMT regimes and relapse (P = 0.169).

CONCLUSIONS

Ocular mucous membrane pemphigoid presenting with HR-EOMs and corneal scarring has an increased risk of stage progression and vision loss. Corneal scarring and severe inflammation at baseline were associated with an increased risk of relapse. A disease progression staging system incorporating both the HR-EOMs and corneal involvement is required to predict the visual outcome of OMMP better.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

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.

Genetic predisposition to ocular surface disorders and opportunities for gene-based therapies

The ocular surface, comprised of the corneal and conjunctival epithelium, innervation system, immune components, and tear-film apparatus, plays a key role in ocular integrity as well as comfort and vision. Gene defects may result in congenital ocular or systemic disorders with prominent ocular surface involvement. Examples include epithelial corneal dystrophies, aniridia, ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, xeroderma pigmentosum (XP), and hereditary sensory and autonomic neuropathy. In addition, genetic factors may interact with environmental risk factors in the development of several multifactorial ocular surface disorders (OSDs) such as autoimmune disorders, allergies, neoplasms, and dry eye disease. Advanced gene-based technologies have already been introduced in disease modelling and proof-of-concept gene therapies for monogenic OSDs. For instance, patient-derived induced pluripotent stem cells have been used for modelling aniridia-associated keratopathy (AAK), XP, and EEC syndrome. Moreover, CRISPR/Cas9 genome editing has been used for disease modelling and/or gene therapy for AAK and Meesmann's epithelial corneal dystrophy. A better understanding of the role of genetic factors in OSDs may be helpful in designing personalized disease models and treatment approaches. Gene-based approaches in monogenic OSDs and genetic predisposition to multifactorial OSDs such as immune-mediated disorders and neoplasms with known or possible genetic risk factors has been seldom reviewed. In this narrative review, we discuss the role of genetic factors in monogenic and multifactorial OSDs and potential opportunities for gene therapy.

[Immunopathogenesis of mucous membrane pemphigoid]

A detailed understanding of the immunopathogenesis of mucous membrane pemphigoid (MMP) is of particular importance in view of the mostly difficult diagnostics and treatment of this blistering autoimmune dermatosis. A still unknown disturbance of the body's own immune tolerance leads to the formation of autoreactive cells. As the disease progresses these produce autoantibodies which are directed against structural proteins in the basement membrane zone (BMZ). After they bind to the target antigen, complement factors are deposited along the BMZ and inflammatory cells invade the underlying tissue and produce the characteristic subepithelial blistering. This inflammatory response is associated with fibrosis and scarring in many affected tissues. Most phases of MMP pathogenesis are poorly understood; however, the last few years have shed more light on this processes. These advances are mostly the result of animal and cell culture models. Typical clinical and immunopathological characteristics of MMP, such as oral, conjunctival and skin lesions, are reflected, for example, in an antibody transfer-induced mouse model for anti-laminin 332 MMP in adult mice. Dapsone, as first-line treatment for MMP patients, significantly reduced the severity of these symptoms, and fibrosis in the skin and mucous membranes was also found histologically, which makes the model well-suited for testing new therapeutic approaches for MMP patients and might be of help for further elucidation of the immunopathogenesis of MMP.

Cutaneous metastases at the sites of pembrolizumab-induced bullous pemphigoid lesions in a patient with melanoma

The authors report a case of bullous pemphigoid (BP) that occurred during pembrolizumab therapy in a 67-year-old male patient with advanced melanoma. Following regression of BP blisters, they reintroduced anti-PD-1 treatment. Due to the flare-up of BP, immunotherapy was discontinued again and corticosteroid was restarted. As the BP lesions regressed, interestingly, new skin metastases developed, exactly where the blisters were. One year after discontinuation of anti-PD-1 treatment, considering the significant tumor progression, pembrolizumab was restarted. This induced tumor remission, while the added low-dose corticosteroid was able to prevent the recurrence of BP. The patient carries the BP-predisposing HLA-DQB1*03:01 allele. In conclusion, anti-PD-1 rechallenge may be considered in metastatic melanoma, even if restarting anti-PD-1 has previously caused the flare-up of BP symptoms.

Imputation of the major histocompatibility complex region identifies major independent variants associated with bullous pemphigoid and dermatomyositis in Han Chinese

As autoimmune skin diseases, both bullous pemphigoid (BP) and dermatomyositis (DM) show significant associations with the major histocompatibility complex (MHC) region. In fact, the coexistence of BP and DM has been previously reported. Therefore, we hypothesized that there may be a potential genetic correlation between BP and DM. Based on data for 312 BP patients, 128 DM patients, and 6793 healthy control subjects, in the MHC region, we imputed single-nucleotide polymorphisms (SNP), insertions and deletions (INDEL), and copy number variations (CNV) using the 1KGP phase 3 dataset and amino acids (AA) and SNP using a Han-MHC reference database. An association study revealed the most significant SNP associated with BP, namely, rs580921 (p = 1.06E-08, odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.37-1.90), which is located in the C6orf10 gene, and the most significant classic human leukocyte antigen (HLA) allele associated with DM, namely, HLA-DPB1*1701 (p = 6.56E-10, OR = 3.61, 95% CI = 2.40-5.42). Further stepwise regression analyses with rs580921 identified a threonine at position 163 of the HLA-B gene as a new independent disease-associated AA, and HLA-DPB1*1701 indicated that no loci were significant. Three-dimensional ribbon models revealed that the HLA-B AA position 163 (p = 3.93E-07, OR = 1.64, 95% CI = 1.35-1.98) located in the α2 domain of the HLA-B molecule was involved in the process of specific antigen presentation. The calculations showed that there was no significant genetic correlation between BP and DM. Our study identified three significant loci in the MHC region, proving that the HLA region was significantly correlated with BP and DM separately. Our research highlights the key role of the MHC region in disease susceptibility.

Case Report: Bullous Pemphigoid Associated With Morphea and Lichen Sclerosus: Coincidental Diseases or Pathogenetic Association?

Bullous pemphigoid (BP) represents the most common autoimmune bullous disease and is characterized by IgG autoantibodies targeting collagen XVII (BP180). BP has reportedly been occurred in association with other inflammatory skin diseases. Here, we describe the unusual occurrence of BP in a female patient with a concomitant history of generalized morphea (localized scleroderma, LoS) and cutaneous and genital lichen sclerosus (LiS). The occurrence of BP was associated with elevated serum levels of anti-BP180 IgG autoantibodies, which decreased upon clinical remission. Autoimmune bullous diseases and sclerosing dermatitis are immunologically distinct entities, whose association has been rarely described. In this study, we provide a literature review on cases of BP developed in patients with either LoS or LiS. Further, we discussed immunological mechanisms which may have favored the emergence of BP in our patient.

Genetic polymorphism of glutathione S-transferases (GSTM1, GSTT1, and GSTP1) in patients with bullous pemphigoid in a Polish population

Introduction. Bullous pemphigoid (BP) is one of the most common bullous diseases with an autoimmune background. The etiology and pathogenesis of BP are believed to be influenced not only by environmental, genetic, and immunological factors as well as by oxidative stress. BP is observed more frequently in elderly patients. Additionally, more potent oxidative stress is observed just in old age. Glutathione S-transferases (GSTs) play key roles in the detoxification of xenobiotics, metabolism of endogenous substrates, and the defense against oxidative stress. The present study examines whether polymorphism of genes encoding three selected GSTs (GSTM1, GSTT1, and GSTP1) might be associated with a higher risk for BP.

Materials and methods. The study involved 71 patients with BP and 100 healthy volunteers from a Polish population. The presence of the deletion type polymorphism for GSTM1 and GSTT1 was confirmed by multiplex PCR. The Ile105Val GSTP1 polymorphism was analyzed by PCR-RFLP.

Results. It was observed that the combination of GSTM1 null/GSTT1 null/GSTP1 Ile/Val, Val/Val genotypes occurred more frequently in patients with BP (8.5%) than in controls (4.0%). The odds ratio for carriers of GSTM1 null/GSTT1 null/ GSTP1 Ile/Val, Val/Val genotypes was 2.22 (95% CI 0.60–8.16; p = 0.3727), but was not statistically significant.

Conclusions. The combination of GSTM1 null, GSTT1 null, GSTP1 Ile/Val, Val/Val genotypes might be related to a greater risk of BP in a Polish population. However, future studies including more individuals are required to confirm this.

Incidence, prevalence, and demographic characteristics of ocular cicatricial pemphigoid in Colombia: data from the National Health Registry 2009-2019

AIM

To provide an epidemiological characterization of ocular cicatricial pemphigoid (OCP) in Colombia.

METHODS

We conducted a cross-sectional study using SISPRO. We applied the specific code of the International Classification of Diseases for Ocular Pemphigoid, from 2009-2019 to estimate prevalence, incidence, and the demographic status of the disease in Colombia.

RESULTS

The estimated average prevalence was 0.22 per 1 000 000 inhabitants, and the estimated average incidence was 0.24 per 1 000 000 inhabitants. With a female predominance of 62.5%, and a male/female ratio of 1:1.6. The group of patients diagnosed with the disease after the age of 80 presented the highest prevalence. The departments with the highest prevalence were Antioquia, Bogotá, and Santander.

CONCLUSION

There are important differences between worldwide and Colombian prevalence and incidence data, which may be related to genetic and epigenetic factors, and the possible underdiagnosis of the disease. According to the results, OCP is an extremely rare disease in Colombia. Nevertheless, it is important to encourage awareness of the disease due to its devastating consequences.

Common Denominators in the Immunobiology of IgG4 Autoimmune Diseases: What Do Glomerulonephritis, Pemphigus Vulgaris, Myasthenia Gravis, Thrombotic Thrombocytopenic Purpura and Autoimmune Encephalitis Have in Common?

IgG4 autoimmune diseases (IgG4-AID) are an emerging group of autoimmune diseases that are caused by pathogenic autoantibodies of the IgG4 subclass. It has only recently been appreciated, that members of this group share relevant immunobiological and therapeutic aspects even though different antigens, tissues and organs are affected: glomerulonephritis (kidney), pemphigus vulgaris (skin), thrombotic thrombocytopenic purpura (hematologic system) muscle-specific kinase (MuSK) in myasthenia gravis (peripheral nervous system) and autoimmune encephalitis (central nervous system) to give some examples. In all these diseases, patients’ IgG4 subclass autoantibodies block protein-protein interactions instead of causing complement mediated tissue injury, patients respond favorably to rituximab and share a genetic predisposition: at least five HLA class II genes have been reported in individual studies to be associated with several different IgG4-AID. This suggests a role for the HLA class II region and specifically the DRβ1 chain for aberrant priming of autoreactive T-cells toward a chronic immune response skewed toward the production of IgG4 subclass autoantibodies. The aim of this review is to provide an update on findings arguing for a common pathogenic mechanism in IgG4-AID in general and to provide hypotheses about the role of distinct HLA haplotypes, T-cells and cytokines in IgG4-AID.

Genetic predisposition to bullous pemphigoid

Bullous pemphigoid (BP) is a common autoimmune blistering skin disease that mainly affects elderly patients. Although BP risk is strongly influenced by age, genetic factors are also important determinants of this disease. Many genomic regions, especially in the HLA-II region, have been found to influence BP susceptibility through targeted sequencing studies. However, the relationship between non-HLA regions and BP susceptibility remains poorly understood and the identification of functional variants and key genes within these association regions remains a major challenge. In this review, we summarize the genetic predisposition to BP through an overview of the research history in this field.

Polymorphisms in the Mitochondrial Genome Are Associated With Bullous Pemphigoid in Germans

Bullous pemphigoid (BP) is the most prevalent autoimmune skin blistering disease and is characterized by the generation of autoantibodies against the hemidesmosomal proteins BP180 (type XVII collagen) and BP230. Most intriguingly, BP is distinct from other autoimmune diseases because it predominantly affects elderly individuals above the age of 75 years, raising the question why autoantibodies and the clinical lesions of BP emerges mostly in this later stage of life, even in individuals harboring known putative BP-associated germline gene variants. The mitochondrial genome (mtDNA) is a potential candidate to provide additional insights into the BP etiology; however, the mtDNA has not been extensively explored to date. Therefore, we sequenced the whole mtDNA of German BP patients (n = 180) and age- and sex-matched healthy controls (n = 188) using next generation sequencing (NGS) technology, followed by the replication study using Sanger sequencing of an additional independent BP (n = 89) and control cohort (n = 104). While the BP and control groups showed comparable mitochondrial haplogroup distributions, the haplogroup T exhibited a tendency of higher frequency in BP patients suffering from neurodegenerative diseases (ND) compared to BP patients without ND (50%; 3 in 6 BP with haplogroup T). A total of four single nucleotide polymorphisms (SNPs) in the mtDNA, namely, m.16263T>C, m.16051A>G, and m.16162A>G in the D-loop region of the mtDNA, and m.11914G>A in the mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 4 gene (MT-ND4), were found to be significantly associated with BP based on the meta-analysis of our NGS data and the Sanger sequencing data (p = 0.0017, p = 0.0129, p = 0.0076, and p = 0.0132, respectively, Peto's test). More specifically, the three SNPs in the D-loop region were negatively, and the SNP in the MT-ND4 gene was positively associated with BP. Our study is the first to interrogate the whole mtDNA in BP patients and controls and to implicate multiple novel mtDNA variants in disease susceptibility. Studies using larger cohorts and more diverse populations are warranted to explore the functional consequences of the mtDNA variants identified in this study on immune and skin cells to understand their contributions to BP pathology.

Genetics and Omics Analysis of Autoimmune Skin Blistering Diseases

Autoimmune blistering diseases (AIBDs) of the skin are characterized by autoantibodies against different intra-/extracellular structures within the epidermis and at the basement membrane zone (BMZ). Binding of the antibodies to their target antigen leads to inflammation at the respective binding site and degradation of these structures, resulting in the separation of the affected skin layers. Clinically, blistering, erythema and lesions of the skin and/or mucous membranes can be observed. Based on the localization of the autoantigen, AIBDs can be divided into pemphigus (intra-epidermal blistering diseases) and pemphigoid diseases (sub-epidermal blistering diseases), respectively. Although autoantigens have been extensively characterized, the underlying causes that trigger the diseases are still poorly understood. Besides the environment, genetic factors seem to play an important role in a predisposition to AIBDs. Here, we review currently known genetic and immunological mechanisms that contribute to the pathogenesis of AIBDs. Among the most commonly encountered genetic predispositions for AIBDs are the HLA gene region, and deleterious mutations of key genes for the immune system. Particularly, HLA class II genes such as the HLA-DR and HLA-DQ alleles have been shown to be prevalent in patients. This has prompted further epidemiological studies as well as unbiased Omics approaches on the transcriptome, microbiome, and proteome level to elucidate common and individual genetic risk factors as well as the molecular pathways that lead to the pathogenesis of AIBDs.

Role of immune cells in the ocular manifestations of pemphigoid diseases

Pemphigoid disease is classified according to the phenotypical location of the disease and the presence of different types of antibodies. The ocular distribution of pemphigoid mainly occurs in patients with bullous pemphigoid and mucous membrane pemphigoid. Several immune cells, including the cells of the innate immune system (neutrophils and γδ T cells) and the adaptive immune system (T and B cells), are involved in pemphigoid disease. The treatment of pemphigoid is still wide-ranging, and the most utilized treatment is the use of immunosuppressants and corticosteroids. In this scenario, it is absolutely important to screen the immune cells that are involved in this group of diseases and to determine if a targeted treatment approach is plausible. In conclusion, this review will identify some newer treatment possibilities for the whole spectrum of pemphigoid diseases.

Proteases in Pemphigoid Diseases

Pemphigoid diseases are a subgroup of autoimmune skin diseases characterized by widespread tense blisters. Standard of care typically involves immunosuppressive treatments, which may be insufficient and are often associated with significant adverse events. As such, a deeper understanding of the pathomechanism(s) of pemphigoid diseases is necessary in order to identify improved therapeutic approaches. A major initiator of pemphigoid diseases is the accumulation of autoantibodies against proteins at the dermal-epidermal junction (DEJ), followed by protease activation at the lesion. The contribution of proteases to pemphigoid disease pathogenesis has been investigated using a combination of in vitro and in vivo models. These studies suggest proteolytic degradation of anchoring proteins proximal to the DEJ is crucial for dermal-epidermal separation and blister formation. In addition, proteases can also augment inflammation, expose autoantigenic cryptic epitopes, and/or provoke autoantigen spreading, which are all important in pemphigoid disease pathology. The present review summarizes and critically evaluates the current understanding with respect to the role of proteases in pemphigoid diseases.

Ocular Mucous Membrane Pemphigoid: Current State of Pathophysiology, Diagnostics and Treatment

Mucous membrane pemphigoid (MMP) is a systemic cicatrizing autoimmune disease that primarily affects orificial mucous membranes, such as the conjunctiva, the nasal cavity, the oropharynx, and the genitalia. Ocular involvement occurs in about 70% of all MMP cases. Ocular MMP (OcMMP) also encompasses the conditions linear immunoglobulin A disease, mucosal dominated epidermolysis bullosa acquisita, and anti-laminin 332/anti-epiligrin/anti-laminin 5 pemphigoid. It is a complex clinical entity that may lead to ocular surface failure and result in inflammatory and infectious complications, as well as potentially devastating visual loss. Early diagnosis and appropriate treatment are of paramount importance and require a high level of expertise as this condition can be extremely challenging to diagnose and treat even for experienced clinicians. In this review we provide an up-to-date insight on the pathophysiology of OcMMP, with an emphasis on the current state of its diagnostics and therapeutics. Our the aim is to increase our understanding of OcMMP and highlight modern diagnostic and therapeutic options.

Subepidermal autoimmune bullous diseases: overview, epidemiology, and associations

Subepidermal autoimmune bullous diseases of the skin and mucosae comprise a large group of chronic diseases, including bullous pemphigoid, pemphigoid gestationis, mucous membrane pemphigoid, linear IgA bullous dermatosis, epidermolysis bullosa acquisita, and anti-p200 pemphigoid. These diseases are characterized by an antibody response toward structural components of the basement membrane zone, resulting in subepidermal blistering. The epidemiological features of these diseases vary substantially in different regions of the world. Observational studies investigating comorbidities and associations among patients with these diseases are inconsistent and sometimes inconclusive. This review provides a brief overview regarding each one of the subepidermal autoimmune bullous diseases. In addition, it summarizes the most recent understanding of the epidemiological features and associations of this group of organ-specific autoimmune diseases.

Autoimmune Subepidermal Bullous Diseases of the Skin and Mucosae: Clinical Features, Diagnosis, and Management

Autoimmune subepidermal blistering diseases of the skin and mucosae constitute a large group of sometimes devastating diseases, encompassing bullous pemphigoid, gestational pemphigoid, mucous membrane pemphigoid, epidermolysis bullosa acquisita, and anti-p200 pemphigoid. Their clinical presentation is polymorphic. These autoimmune blistering diseases are associated with autoantibodies that target distinct components of the basement membrane zone of stratified epithelia. These autoantigens represent structural proteins important for maintenance of dermo-epidermal integrity. Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering disease of the skin and mucosae. Although the disease typically presents with a generalized blistering eruption associated with itch, atypical variants with either localized bullous lesions or "non-bullous" presentations are observed in approximately 20% of patients. A peculiar form of BP typically associated with pregnancy is pemphigoid gestationis. In anti-p200 pemphigoid, patients present with tense blisters on erythematosus or normal skin resembling BP, with a predilection for acral surfaces. These patients have antibodies targeting the 200-kDa basement membrane protein. Epidermolysis bullosa is a rare autoimmune blistering disease associated with autoantibodies against type VII collagen that can have several phenotypes including a classical form mimicking dystrophic epidermolysis bullosa, an inflammatory presentation mimicking BP, or mucous membrane pemphigoid-like lesions. Mucous membrane pemphigoid (MMP) is the term agreed upon by international consensus for an autoimmune blistering disorder, which affects one or more mucous membrane and may involve the skin. The condition involves a number of different autoantigens in the basement membrane zone. It may result in severe complications from scarring, such as blindness and strictures. Diagnosis of these diseases relies on direct immunofluorescence microscopy studies and immunoserological assays. Management of affected patients is often challenging. We will here review the clinical and immunopathological features as well as the pathophysiology of this group of organ-specific autoimmune diseases. Finally, we will discuss the diagnostic approach and the principles of management in clinical practice.

Haplotypes of ABCB1 1236C >T (rs1128503), 2677G >T/A (rs2032582), and 3435C >T (rs1045642) in patients with bullous pemphigoid

Bullous pemphigoid (BP) constitutes the most prevalent disease in the group of bullous dermatoses with the autoimmune background. Some authors suggest that certain cytokines (IL-2, IFN-γ) may be transported by P-glycoprotein (P-gp), the product of the ABCB1 gene. ABCB1 polymorphism might affect not only the effectiveness of treatment with drugs that are P-gp substrates but also contribute to the development of diseases, including BP. In the present work, we resolved to conduct a haplotype analysis of ABCB1 in patients with BP and to answer the question of whether any of the haplotypes are able to affect the incidence of this entity. The study involved 71 patients with BP and 100 healthy volunteers. Determination of polymorphisms 1236C > T and 3435C > T in ABCB1 was carried out with the PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) method. The 2677G > T/A ABCB1 polymorphism was analyzed with the allele-specific PCR method. It was observed that the 1236T-2677G-3435T haplotype occurred with a statistically significantly lower frequency in patients with BP than in controls (1.4 vs. 10.0%). Carriers of this haplotype were also shown to have had a low relative risk for BP (OR = 0.13, p = 0.003). Haplotype analysis of ABCB1 conducted in patients with BP demonstrated that the 1236T-2677G-3435T haplotype may protect against development of this entity.

Identification of Immunodominant Th2-Cell Epitopes in Chinese Patients with Bullous Pemphigoid

Bullous pemphigoid (BP) is a subepidermal autoimmune blistering disease caused by autoantibodies targeting the juxtamembranous extracellular noncollagenous 16A (NC16A) domain of human collagen XVII (also known as BP180). Because T-helper (Th) cells are essential for antibody responses to antigens, we adopted an assay to map the immunodominant Th2-cell epitopes in NC16A. We synthesized 22 overlapping peptides spanning the entire sequence of BP180-NC16A and investigated the reactivity of Th2 cells from patients with BP to these peptides using the Enzyme-Linked ImmunoSpot (ELISPOT) assay. We screened two epitope peptides, P2 (492-506 aa: VRKLKARVDELERIR) and P5 (501-515 aa: ELERIRRSILPYGDS), and confirmed that these epitopes play a dominant role in stimulating CD4⁺ T-cell proliferation and Th2 IL-4 cytokine production, and activating B cells to secrete autoantibodies. These immunodominant epitopes are HLA-DR-restricted and were observed in subjects with different HLA alleles. This work contributes to elucidation of the epitope-mediated immunologic pathogenesis of BP, and the identified Th2-cell epitopes are candidates for epitope-specific therapeutic strategy.

Diagnostic value of autoantibody titres in patients with bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune blistering disease of the skin requiring skin and serum tests for a precise diagnosis.

OBJECTIVES

We analysed the sensitivity and specificity of BP-relevant parameters and the value of autoantibody titres during follow-up of BP patients.

MATERIALS & METHODS

In a retrospective single-centre study, we included 200 consecutive patients with BP and 400 non-BP patients, and evaluated the test results of patients' serum and skin. In addition, we followed patients' autoantibody titres and clinical characteristics.

RESULTS

BP180-ELISA revealed the highest sensitivity (85.0%; specificity: 93.9%), while BP230-ELISA demonstrated the lowest sensitivity (55.5%; specificity: 92.9%). Direct and indirect immunofluorescence showed comparable results for sensitivity (77.2%/72.7%) and specificity (94.9%/93.7%). The sensitivity for skin histology was 76.3% (specificity: 81.3%). Longitudinal analysis showed significant changes in autoantibody titres.

CONCLUSIONS

BP diagnostics should include serum tests for BP autoantibodies and skin immunofluorescence. Skin histology is supportive for diagnosis. Autoantibody titres are markers for disease activity.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.

Association of HLA class I and class II alleles with bullous pemphigoid in Chinese Hans

BACKGROUND

Bullous pemphigoid (BP) is one of the most common autoimmune skin diseases. Associations of genes, especially human leukocyte antigen (HLA)-DQ alleles, with BP indicate that genetic predisposition contributes to the disease.

OBJECTIVES

To evaluate the association of HLA class I and HLA class II alleles with susceptibility to BP in the northern Chinese Han population.

METHODS

We performed genotype for HLA-A, -B, -C, -G, -DPA1, -DPB1, -DQA1, -DQB1 and -DRB1 loci in 105 patients with BP by Sanger sequence-based typing (SBT) method. These data were compared with a local control cohort of 420 age- and sex-matched cases.

RESULTS

Among the HLA alleles described herein, the susceptibility alleles associated with a high prevalence of BP were A*11:01 (OR = 1.9 Pc = 0.017); B*37:01 (OR = 8, Pc = 1.811 × 10^-6); G*01:01 (OR = 3.61, Pc = 2.839 × 10^-15) and G*01:06 (OR = 2.22, Pc = 0.025); DQA1*01:05 (OR = 4.87, Pc = 5.822 × 10^-5), DQA1*05:05 (OR = 2.64, Pc = 9.114 × 10^-4), and DQA1*05:08 (OR = 10.2, Pc = 0.016); DQB1*03:01 (OR = 1.69, Pc = 0.048) and DQB1*05:01 (OR = 3.42, Pc = 7.28 × 10^-6); and DRB1*10:01 (OR = 6.85, Pc = 2.63 × 10^-6). To the contrary, HLA-DQA1*01:02 (OR = 0.46, Pc = 8.603 × 10^-4) and DQA1*01:03 (OR = 0.38, Pc = 0.048); DQB1*02:02 (OR = 0.28, Pc = 0.016); and DRB1*07:01 (OR = 0.26, Pc = 0.004) had significant associations with protection against BP. In addition, the frequency of haplotype HLA-DRB1*13-DQA1*05-DQB1*03 (OR = 12.32, Pc = 0.026) in BP patients was significantly higher than those in controls.

CONCLUSION

Our data demonstrated that the alleles and haplotypes found in this study may be important differential genetic markers for susceptibility to or protection against BP in individuals of northern Chinese Han population.

Ethnic variations in the epidemiology of bullous pemphigoid in Israel

BACKGROUND

No ethnic or geographic predisposition to bullous pemphigoid (BP) was reported so far.

OBJECTIVE

To evaluate trends in the incidence of BP in northern Israel, shedding light on differences between two distinct ethnic populations who inhabit the same region, namely Jews and Arabs.

METHODS

Bullous pemphigoid incidence was retrospectively estimated from January 2000-December 2015 in two Israeli regions with a total population of 1.56 million inhabitants.

RESULTS

A total of 287 new-onset BP patients (mean age: 77.6 ± 12.1) were identified. The incidence rate was 11.4 per million inhabitants per year (95% CI, 10.2-12.9). The crude incidence rate in Jews was 4.8-fold higher than that in Arabs (16.4 vs. 3.4 cases per million per year, respectively [P < 0.0001]). After adjusting for age, the discrepancy between the two populations diminished (11.7 vs. 8.9 cases per million per year, respectively) but remained statistically significant (P = 0.032). The incidence increased consistently from 7.6 cases per million per year in the calendar period 2000-2005 to 12.6 and 14.3 cases in 2006-2010 and 2011-2015, respectively (P < 0.0001). Bullous pemphigoid patients of Arab ancestry presented with the disease significantly earlier than Jews (69.5 ± 15.3 vs. 78.7 ± 11.1 years, respectively, P = 0.002).

CONCLUSIONS

The incidence of BP in northern Israel has increased in the last 16 years and is significantly higher among Jews compared to Arabs. The age of presentation is remarkably different between patients belonging to the two populations.

A multi-hit hypothesis of bullous pemphigoid and associated neurological disease: Is HLA-DQB1*03:01, a potential link between immune privileged antigen exposure and epitope spreading?

Bullous pemphigoid (BP) is the most common autoimmune blistering disease and is linked to IgG recognition of 2 hemidesmosomal antigens, that is, BP230 (BP antigen 1) and BP180 (BP antigen 2, collagen XVII). The association of BP with other systemic diseases, particularly neurocognitive diseases, provides a potential clue in the underlying pathogenesis of BP. The role of HLA-DQB1*03:01 binding to the immunogenic portion of BP180 provides a potential mechanism by which exposure to neuronal collagen BP180 may lead to cutaneous disease. In our proposed multi-hit hypothesis, patients with underlying neuronal disease are exposed to previously sequestered self-antigen, most importantly BP180. Patients with the HLA-DQB1*03:01 allele show an increased T-cell avidity to several epitopes of BP180, particularly the BP180-NC16a domain. Thus, they have a genetic susceptibility to developing BP upon exposure to the target antigen. In a patient with dysregulation of Th1/Th2 balance, anergy is lost and T-cells are subsequently primed resulting in the development of functional autoimmunity against the BP180-NC16a domain leading to clinically overt disease.

ABCB1 gene is associated with the risk of bullous pemphigoid in a polish population

BACKGROUND AND OBJECTIVES

Polymorphisms in the P-glycoprotein-encoding ABCB1 gene may affect the intracellular concentration of xenobiotics, and thus contribute to the development of autoimmune diseases, including bullous pemphigoid (BP). The objective of the present study was to investigate whether there is an association between the C3435T and G2677T/A polymorphisms in the ABCB1 gene and the risk of BP in a Polish population.

PATIENTS AND METHODS

The study included 71 patients with BP and 156 healthy volunteers. Determination of the C3435T polymorphism was carried out using PCR-RFLP; the G2677T/A polymorphism, using allele-specific PCR.

RESULTS

While there was no correlation between the C3435T polymorphism and the risk of BP, we did find such an association with respect to the G2677T/A polymorphism. The relative risk of BP was more than five times greater in individuals with the 2677TA genotype (OR = 5.52, p = 0.0063), and more than twice as high in carriers of the 2677TT genotype (OR = 2.40, p = 0.0076). At 2.40 (0.000018), the OR in carriers of the 2677T allele was also increased. The greater prevalence of the 2677GG genotype and the 2677G allele in the control group, as well as the OR < 1.0 (0.22 and 0.33, respectively), suggest a protective role of the 2677G allele with respect to the development of BP.

CONCLUSIONS

The results of the present study indicate that the G2677T/A polymorphism in the ABCB1 gene may affect the risk of developing BP.

Geographic variations in epidemiology of two autoimmune bullous diseases: pemphigus and bullous pemphigoid

Autoimmune bullous diseases are rare, organ-specific, a group of blistering disease of skin and mucous membranes. Recent studies suggest that the frequency of the autoimmune bullous diseases has been increasing. Pemphigus vulgaris and bullous pemphigoid are the most frequently reported autoimmune bullous diseases. High incidence of autoimmune bullous diseases in some ethnic groups such as pemphigus in Ashkenazi Jewish, or in some regions such as pemphigus foliaceus in Brazil has been shown to be related to genetic and environmental factors, respectively. Pemphigus has been reported more frequently in the female gender. Although it is most frequently diagnosed between the ages 50 and 60 in European countries, in the remaining countries in the world, it is seen between the ages of 30 and 50. Bullous pemphigoid is generally seen above 70 years of age. Although overall incidence is slightly higher in females, after the age of 80 years it is more frequent in males. Both pemphigus vulgaris and bullous pemphigoid has a chronic course with recurrences. Mortality risk of the patients with bullous pemphigoid was found at least 2 times higher and the mortality risk of the patients with pemphigus was found approximately 3 times higher than that of the general population. In this review, the results obtained from the epidemiological studies were analyzed according to geographic regions, and especially epidemiologic features of two prevalent autoimmune bullous diseases, pemphigus and bullous pemphigoid have been discussed.

Update on the pathogenesis of bullous pemphigoid: an autoantibody-mediated blistering disease targeting collagen XVII

Bullous pemphigoid (BP) is a common autoimmune blistering skin disorder that tends to affect the elderly. Autoantibodies (autoAbs) from BP patients react with two hemidesmosomal components: transmembrane collagen XVII (BP180 or BPAG2) and plakin family protein BP230 (BPAG1). Of these, collagen XVII (COL17) is thought to be a major autoantigen. The binding of autoAbs to COL17 following the activation of complements and inflammatory pathways eventually leads to the degradation of COL17, and this has been regarded as the main pathogenesis of BP. However, recent investigations have suggested other pathways, including a complement-independent pathway and a pathway involving IgE-autoAbs. BP-autoAbs can directly deplete COL17, leading to fragility of the dermal-epidermal junction. In addition, IgE-autoAbs to COL17 may be involved in the formation of itchy urticarial erythema associated with eosinophilic infiltration. This article summarizes the update on pathogenesis of BP, with a special focus on blister formation by autoAbs to COL17.

[Human leukocyte antigen (HLA) system in ophthalmology]

Various inflammatory and non-inflammatory eye diseases are associated with specific HLA isotypes. Therefore, HLA isotyping can be a useful diagnostic tool for these diseases and has already been shown to reduce the rejection rate of corneal allografts. Unfortunately, the volume of published data and the varying quality of these publications complicate obtaining good overview in this field. This review briefly summarizes the genetic structure of the HLA system and elucidates differences between HLA classes I and II in the context of antigen presentation. Possible mechanisms of HLA associations in the field of ophthalmology are discussed, and finally different tools (e.g. genome wide association studies) for assessing associations of HLA isotypes with different ocular diseases are examined.

The putative role of the C1858T polymorphism of protein tyrosine phosphatase PTPN22 gene in autoimmunity

Autoimmune diseases represent a heterogeneous group of conditions whose incidence is increasing worldwide. This has stimulated studies on their etiopathogenesis, derived from a complex interaction between genetic and environmental factors, in order to improve prevention and treatment of these diseases. An increasing amount of epidemiologic investigations has associated the presence of the C1858T polymorphism in the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene to the onset of several autoimmune diseases including insulin-dependent diabetes mellitus (Type 1 diabetes). PTPN22 encodes for the lymphoid tyrosine phosphatase Lyp. This belongs to non-receptor-type protein tyrosine phosphatases involved in lymphocyte activation and differentiation. In humans, Lyp may have a role in the negative regulation of T cell receptor signaling. The single nucleotide polymorphism C1858T encodes for a more active phosphatase Lyp R620W. This has the ability to induce a higher negative regulation of T cell receptor signaling. Thus, C1858T could play an important role at the level of thymocyte polarization and escape of autoreactive T lymphocytes, through the positive selection of otherwise negatively selected autoimmune T cells. In this review we discuss the physiological role exerted by the PTPN22 gene and its encoded Lyp product in lymphocyte processes. We highlight the pathogenic significance of the C1858T PTPN22 polymorphism in human autoimmunity with special reference to Type 1 diabetes. Recently the genetic variation in PTPN22 was shown to induce altered function of T and B-lymphocytes. In particular BCR signaling defects and alterations in the B cell compartment were reported in T1D patients. We finally speculate on the possible development of novel therapeutic treatments in human autoimmunity aiming to selectively target the variant Lyp protein in autoreactive T and B lymphocytes.

Gene network analysis of small molecules with autoimmune disease associated genes predicts a novel strategy for drug efficacy

Numerous genes/SNPs in autoimmune diseases (ADs) are identified through genome-wide association studies (GWAS) and likely to contribute in developing autoimmune phenotypes. Constructions of biologically meaningful pathways are necessary to determine how these genes interact with each other and with other small molecules to develop various complex AD phenotypes prior to beginning time-consuming rigorous experimentation. We have constructed biological pathways with genetically identified genes leading to shared AD phenotypes. Various environmental and endogenous factors interact with these AD associated genes suggesting their critical role in developing diseases and further association studies could be designed for assessing the role of these factors with risk allele in a specific gene. Additionally, existing drugs that have been used long before the identification of these genetically associated genes also interact with these newly associated genes. Thus advanced therapeutic strategies could be designed by grouping patients with risk allele(s) in particular genes that directly or closely interact with the specified drugs. This drug-susceptible gene network will not only increase our understanding about the additional molecular basis for effectiveness against these diseases but also indicate which drug could be more effective for those patients carrying risk allele(s) in that gene. Additionally, we have also identified several interlinking genes in the pathways that could be used for designing future association studies.

Diagnostic accuracy of enzyme-linked immunosorbent assays (ELISA) to detect anti-skin autoantibodies in autoimmune blistering skin diseases: a systematic review and meta-analysis

BACKGROUND

Systematic reviews and meta-analysis are essential tools to accurately and reliably summarize evidence, and can be used as a starting point for developing practice guidelines for the diagnosis and treatment of patients.

AIM

To estimate the diagnostic accuracy of enzyme-linked immunosorbent assays (ELISA) to detect anti-BP180 and anti-desmoglein 3 (Dsg3) autoantibodies in the diagnosis of autoimmune blistering skin diseases.

METHODS

A Medline search of English written articles, published between 1994 and 2011, reporting data on the sensitivity and specificity of diagnostic tests was conducted using the following search terms: "BP180 autoantibodies", "Dsg3 autoantibodies", and "enzyme linked immunosorbent assay". The selected articles have been evaluated according to the quality of the statistical methods used to calculate diagnostic accuracy (definition of cutoff value, use of ROC curves, and selection of control cases). The meta-analysis was performed using a summary ROC (SROC) curve and a random-effect model to independently combine sensitivity and specificity across studies.

RESULTS

The search yielded 69 publications on BP180 autoantibodies and 178 on Dsg3 autoantibodies. A total of 30 studies met the inclusion criteria: 17 provided data on the assays to detect autoantibodies to BP180 in a sample of 583 patients with bullous pemphigoid (BP), while 13 studies provided data on the assays to search for anti-Dsg3 autoantibodies in a sample of 1058 patients with pemphigus vulgaris (PV). The 17 studies on BP180 autoantibodies yielded a pooled sensitivity of 0.87 (95% confidence interval (CI) 0.85 to 0.89) and a pooled specificity of 0.98 (CI, 0.98 to 0.99). The area under the curve (AUC) for the SROC curve was 0.988, and the summary diagnostic odds ratio was 374.91 (CI, 249.97 to 562.30). The 13 studies on Dsg3 autoantibodies which met the inclusion criteria, yielded a pooled sensitivity of 0.97 (CI, 0.95 to 0.98), and a pooled specificity of 0.98 (CI, 0.98 to 0.99). The AUC for the SROC curve was 0.995 and the summary diagnostic odds ratio was 1466.11 (95% CI, 750.36 to 2864.61).

CONCLUSIONS

Results of the meta-analysis demonstrated that ELISA tests for anti-BP180 and anti-Dsg3 autoantibodies have high sensitivity and specificity for BP and PV, respectively, and can be used in daily laboratory practice for the initial diagnosis of autoimmune blistering skin diseases.

Origin and plasticity of MHC I-associated self peptides

Endogenous peptides presented by MHC I molecules represent the essence of self for CD8 T lymphocytes. These MHC I peptides (MIPs) regulate all key events that occur during the lifetime of CD8 T cells. CD8 T cells are selected on self-MIPs, sustained by self-MIPs, and activated in the presence of self-MIPs. Recently, large-scale mass spectrometry studies have revealed that the self-MIP repertoire is more complex and plastic than previously anticipated. The composition of the self-MIP repertoire varies from one cell type to another and can be perturbed by cell-intrinsic and -extrinsic factors including dysregulation of cellular metabolism and infection. The complexity and plasticity of the self-MIP repertoire represent a major challenge for the maintenance of self tolerance and can have pervasive effects on the global functioning of the immune system.