Autoimmune Blistering Skin Disease Research Articles

Immunoadsorber for specific apheresis of autoantibodies in the treatment of bullous pemphigoid.

Bullous pemphigoid (BP) is an autoimmune blistering skin disease associated with autoantibodies against two hemidesmosomal proteins, BP180 (type XVII collagen) and BP230. As the pathogenic relevance of antibodies against the immunodominant NC16A domain of BP180 has been clearly demonstrated, specific removal of these antibodies should be a rational therapeutic approach. Here, we evaluated three recombinant forms of bacterially produced BP180 NC16A, a monomer, trimer, and tetramer, together with different matrices for their efficacy to specifically adsorb autoantibodies from BP plasma samples. An adsorber consisting of NC16A-trimer coupled to NHS-activated Sepharose 4 Fast Flow revealed satisfying adsorption rates and a high specificity. The NC16A-trimer adsorber was regenerable and autoclavable. It has the potential to be used for specific immunoadsorption to treat severe and refractory BP and other pemphigoid diseases associated with BP180 NC16A reactivity.

Paraneoplastic Pemphigus: Autoimmune-Cancer Nexus in the Skin.

Paraneoplastic pemphigus (PNP) is a debilitating and lethal adult and pediatric autoimmune blistering skin disease that occurs in the setting of a known or occult neoplasm. It is characterized by painful mucosal erosions that are often resistant to therapy. These clinical characteristics, in addition to positive immunohistochemistry findings make the diagnosis of PNP. The ability to recognize and diagnose PNP has dramatically improved in the last two and half decades. However, the mortality remains 75-90% with a mean survival of less than 1 year. The disease typically progresses from localized skin manifestations to multiple organ failure despite treatment with high dose corticosteroids and immunosuppressives. Because PNP has a low incidence and prevalence, information on treatment and management strategies has depended on a limited number of case reports and case series. The rarity of the disease hampers the ability to conduct large-scale clinical trials as well as investigations into the pathophysiology of PNP. In this article, we review clinical presentation, diagnosis, management, treatment, and pathophysiology of PNP.

Skin microbiota-associated inflammation precedes autoantibody induced tissue damage in experimental epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a chronic autoimmune blistering skin disease characterized by autoantibodies against type VII collagen (COL7). Immunization of SJL/J mice with recombinant murine COL7 results in break of tolerance and skin blisters. Strikingly, despite circulating autoantibodies, the same genetic background and identical environmental conditions, 20% of mice remain healthy. To elucidate the regulation of the transition from the presence of autoantibodies to overt autoimmune disease, we characterized the innate and adaptive immune response of mice that remain healthy after immunization and compared it to mice that developed skin disease.Both clinically healthy and diseased SJL/J mice showed circulating autoantibodies and deposition of complement-fixing IgG2c autoantibodies and C3 at the dermal–epidermal junction. However, only in diseased animals significant neutrophil infiltration and increase in FcgRIV expression were observed in the skin. In contrast, the expression of T cell signature cytokines in the T cell zone of the draining lymph node was comparable between clinically healthy and diseased animals after immunization. Surprisingly, health was associated with a decreased expression of CD11c, TNFA and KC (CXCL1) in the skin prior to immunization and could be predicted with a negative predictive value of >80%. Furthermore, mice that did not develop clinical disease showed a significantly higher richness and distinctly clustered diversity of their skin microbiota before immunization.Our data indicate that the decision whether blisters develop in the presence of autoantibodies is governed in the skin rather than in the lymph node, and that a greater richness of cutaneous bacterial species appears to be protective.

Deletion of the Major Bullous Pemphigoid Epitope Region of Collagen XVII Induces Blistering, Autoimmunization, and Itching in Mice

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering skin disease with a characteristic of pruritus and blistering. BP patients carry inflammation-triggering autoantibodies against the collagen XVII (ColXVII, also known as BP180) juxtamembraneous extracellular noncollagenous 16A (NC16A) domain involved in ectodomain shedding. Deletion of the corresponding NC14A region in a genetically modified mouse model (ΔNC14A) decreased the amount of ColXVII in skin, but it did not prevent ectodomain shedding. Newborn ΔNC14A mice had no macroscopic phenotypic changes. However, subepidermal microblisters, rudimentary hemidesmosomes, and loose basement membrane zone were observed by microscopy. ΔNC14A mice grow normally, but at around 3 months of age they start to scratch themselves and develop crusted erosions. Furthermore, perilesional eosinophilic infiltrations in the skin, eosinophilia, and elevated serum IgE levels are detected. Despite the removal of the major BP epitope region, ΔNC14A mice developed IgG and IgA autoantibodies with subepidermal reactivity, indicating autoimmunization against a dermo-epidermal junction component. Moreover, IgG autoantibodies recognized a 180-kDa keratinocyte protein, which was sensitive to collagenase digestion. We show here that ΔNC14A mice provide a highly reproducible BP-related mouse model with spontaneous breakage of self-tolerance and development of autoantibodies.

Eosinophilic Skin Diseases: A Comprehensive Review.

Eosinophilic skin diseases, commonly termed as eosinophilic dermatoses, refer to a broad spectrum of skin diseases characterized by eosinophil infiltration and/or degranulation in skin lesions, with or without blood eosinophilia. The majority of eosinophilic dermatoses lie in the allergy-related group, including allergic drug eruption, urticaria, allergic contact dermatitis, atopic dermatitis, and eczema. Parasitic infestations, arthropod bites, and autoimmune blistering skin diseases such as bullous pemphigoid, are also common. Besides these, there are several rare types of eosinophilic dermatoses with unknown origin, in which eosinophil infiltration is a central component and affects specific tissue layers or adnexal structures of the skin, such as the dermis, subcutaneous fat, fascia, follicles, and cutaneous vessels. Some typical examples are eosinophilic cellulitis, granuloma faciale, eosinophilic pustular folliculitis, recurrent cutaneous eosinophilic vasculitis, and eosinophilic fasciitis. Although tissue eosinophilia is a common feature shared by these disorders, their clinical and pathological properties differ dramatically. Among these rare entities, eosinophilic pustular folliculitis may be associated with human immunodeficiency virus (HIV) infection or malignancies, and some other diseases, like eosinophilic fasciitis and eosinophilic cellulitis, may be associated with an underlying hematological disorder, while others are considered idiopathic. However, for most of these rare eosinophilic dermatoses, the causes and the pathogenic mechanisms remain largely unknown, and systemic, high-quality clinical investigations are needed for advances in better strategies for clinical diagnosis and treatment. Here, we present a comprehensive review on the etiology, pathogenesis, clinical features, and management of these rare entities, with an emphasis on recent advances and current consensus.

Survey of bullous pemphigoid disease in northern Iran.

Bullous pemphigoid is an autoimmune subepidermal blistering skin and mucous membrane disease that usually occurs in elderly people. This study was done to determine clinical features, paraclinical findings, incidence of mucosal lesions, prognosis, course of the disease, and mortality rate of patients with bullous pemphigoid. Retrospective descriptive study that reviews the existing files of 122 patients with bullous pemphigoid referred to dermatology clinics of Ghaem and Imam Reza hospitals in Mashhad, Iran, from 1995 to 2010. The majority of patients were aged between 60 and 79 years, and 53% of them were women. The major prodromal lesions were erythematous and urticarial (36.8%) and eczematous lesions (32.7%); 84.3% of patients complained of pruritus, and mucosal lesions were observed in 31.1% of patients (all in the oral mucosa). The most frequent concurrent diseases with pemphigoid were hypertension and diabetes mellitus. Clinical features, paraclinical findings, incidence of mucosal lesions, prognosis, course of the disease, and mortality rate of bullous pemphigoid in the Khorasan region were approximately similar to results from other regions.

Conditional depletion of mast cells has no impact on the severity of experimental epidermolysis bullosa acquisita.

The role of mast cells (MCs) in autoimmunity is the matter of an intensive scientific debate. Based on observations in different MC-deficient mouse strains, MCs are considered as fundamental players in autoimmune diseases. However, most recent data suggest that the outcome of such diseases is strongly affected by the individual mouse strain used. By the use of two c-Kit mutant MC-deficient mouse strains and one c-Kit-independent strain, we here investigated the role of MCs in a systemic Ab transfer model of epidermolysis bullosa acquisita, a subepidermal autoimmune blistering skin disease characterized by autoantibodies against type VII collagen. While C57BL/6J-Kit(W-sh/W-sh) mice developed an unexpected increased blistering phenotype, no significant differences to WT controls were seen in WBB6F1 -Kit(W/W-v) or the novel Mcpt5-Cre iDTR animals. Interestingly, in a local Ab transfer model, which induces a localized disease, we showed that application of high concentrations of anti-COL7 (where COL7 is type VII collagen) Abs induced MC activation and MC-dependent edema formation that did, however, not contribute to blister induction. Our results indicate that in the autoimmune disorder epidermolysis bullosa acquisita MCs do not contribute to the immune-mediated tissue injury. Modern c-Kit mutant-independent MC-deficient mouse strains will help to further redefine the role of MCs in autoimmunity.

Identification of a new disease cluster of pemphigus vulgaris with autoimmune thyroid disease, rheumatoid arthritis and type I diabetes.

Pemphigus vulgaris (PV) is a potentially fatal autoimmune blistering skin disease. It is known that individuals with autoimmune diseases such as PV, as well as their family members, are at increased risk of developing other autoimmune diseases. However, it is unknown whether there are specific autoimmune diseases that cluster with PV. To investigate the frequency of coexisting autoimmune diseases in patients with PV and their relatives, to determine the prevalence of specific autoimmune diseases in patients with PV vs. the general population and to identify statistically significant clinical clusters linking PV with other autoimmune disorders. We performed a cross-sectional study and meta-analysis of patient data from our own patient database (n = 230), an anonymous online survey conducted by our laboratory (n = 171) and the International Pemphigus & Pemphigoid Foundation registry (n = 393). We found that the prevalences of autoimmune thyroid disease (AITD), rheumatoid arthritis and type 1 diabetes were significantly increased in patients with PV compared with the general population. These diseases were also among the most frequent in family members of patients with PV, in addition to systemic lupus erythematosus (SLE). Descriptive cluster analysis using basic principle components methods revealed that PV forms a distinct cluster with AITD, rheumatoid arthritis and type 1 diabetes, and another cluster with SLE, AITD and rheumatoid arthritis. PV belongs to an established autoimmune disease cluster that includes AITD, rheumatoid arthritis and type 1 diabetes. Our data suggest the possibility of common genetic elements across clinically distinct diseases that might underlie autoimmune susceptibility.

Development of a Disease Registry for Autoimmune Bullous Diseases: Initial Analysis of the Pemphigus Vulgaris Subset

Pemphigus vulgaris (PV) is a rare, potentially life threatening, autoimmune blistering skin disease. The International Pemphigus and Pemphigoid Foundation (IPPF) has recently developed a disease registry with the aim to enhance our understanding of autoimmune bullous diseases with the long-term goal of acquiring information to improve patient care. Patients were recruited to the IPPF disease registry through direct mail, e-mail, advertisements, and articles in the IPPF-quarterly, -website, -Facebook webpage, and IPPF Peer Health Coaches to complete a 38-question survey. We present here the initial analysis of detailed clinical information collected on 393 PV patients. We report previously unrecognized gender differences in terms of lesion location, autoimmune comorbidity, and delay in diagnosis. The IPPF disease registry serves as a useful resource and guide for future clinical investigation.

Autoantibodies Against Multiple Epitopes in Bp180 and Laminin Gamma-1 in Subepidermal Blistering Skin Disease Associated with Psoriatic Erythroderma.

We report a 79-year-old Japanese man who developed subepidermal blistering skin disease after an 8-year history of psoriasis. Histology of a bullous lesion revealed a subepidermal blister with a mixed inflammatory cell infiltrate and fibrin nets. Indirect immunofluorescence using normal human skin sections revealed IgG and IgA autoantibodies in the patient serum, which bound to the epidermal side of 1M NaCl-split skin sections. Immunoblot analysis revealed that both IgA and IgG antibodies reacted with the BP180 NC16a domain and the 120-kDa LAD-1 and that IgG antibodies also reacted with the BP180 C-terminal domain and laminin gamma-1. These findings indicated that autoantibodies to laminin gamma-1 and multiple epitopes in BP180 ectodomain played a role in the pathogenesis of this unique autoimmune subepidermal blistering skin disease associated with psoriasis.

Immunofluorescence testing in the diagnosis of autoimmune blistering diseases: overview of 10-year experience.

BACKGROUNDImmunofluorescence testing is an important tool for diagnosing blistering diseases.OBJECTIVETo characterize the immunofluorescence findings in patients diagnosed with autoimmune blistering skin diseases.METHODSWe retrospectively analyzed immunofluorescence results encompassing a 10-year period.RESULTS421 patients were included and divided into 2 groups: group 1- intraepidermal blistering diseases (n=277) and 2- subepidermal blistering diseases (n=144). For group 1, positive DIF findings demonstrated: predominance of IgG intercellular staining (ICS) and C3 for pemphigus foliaceus-PF (94% and 73% respectively), pemphigus vulgaris-PV (91.5%-79.5%) and paraneoplastic pemphigus-PNP (66%-33%); ICS IgA in 100% of IgA pemphigus cases, and IgG deposits in the basement membrane zone (BMZ) along with ICS in one Hailey-Hailey patient. The IIF findings revealed mean titers of 1:2.560 for PV and 1:1.280 for PF. For paraneoplastic pemphigus, IIF was positive in 2 out of 3 cases with rat bladder substrate. In group 2, positive DIF findings included multiple deposits at basement membrane zone for epidermolysis bullosa acquisita-EBA (C3-89%,IgG-79%,IgA-47%,IgM-21%) mucous membrane pemphigoid-MMP (C3,IgG,IgA,IgM-80%) and bullous pemphigoid-BP (C3-91%,IgG-39%,IgA-11%,IgM-6%), and IgA at basement membrane zone for IgA linear disease (99%) and dermatitis herpetiformis-DH (dermal papillae in 84.6%). For lichen planus pemphigoides, there was C3 (100%) and IgG (50%) deposition at basement membrane zone. indirect immunofluorescence positive findings revealed basement membrane zone IgG deposits in 46% of BP patients, 50% for EBA, 15% for IgA linear dermatosis and 50% for LPP. Indirect immunofluorescence positive results were higher for BP and EBA with Salt-Split skin substrate.CONCLUSIONOur results confirmed the importance of immunofluorescence assays in diagnosing autoimmune blistering diseases, and higher sensitivity for indirect immunofluorescence when Salt-split skin technique is performed.

Bullous pemphigoid in infants: characteristics, diagnosis and treatment.

BackgroundBullous pemphigoid (BP) in infants is a rare but increasingly reported autoimmune blistering skin disease. Autoantibody reactivity is usually poorly characterized. Current guidelines do not address specific aspects of the infantile form of BP. The objectives of this study are to define clinical and diagnostic characteristics of infantile BP and develop a treatment algorithm.MethodsDetailed characterization of a current case series of five infants with BP from our departments. Comprehensive analysis of all reported cases (1–12 months) with respect to clinical and laboratory characteristics, treatment and outcome.ResultsIn total 81 cases were identified (including our own). The mean age was 4.5 months. Moderately severe and severe disease was seen in 84% of cases. Involvement of hands and feet was present in all cases. Immunofluorescence microscopy was comparable with BP in adults. Where analyzed, the NC16A domain of bullous pemphigoid 180 kDa antigen/collagen XVII (BP180) was identified as the major target antigen. BP180 NC16A ELISA values in our cohort were significantly higher than in a control cohort of 28 newly diagnosed adult patients.50% of patients were treated with systemic corticosteroids, 20% with a combination of systemic corticosteroids and dapsone or sulfapyridine and 10% with topical corticosteroids alone. 14% of patients needed a combination of multiple immunosuppressants. All but one patient reached remission. Relapses were rare.ConclusionsPresentation of infantile BP is often severe with blistering of hands and feet present in all cases. Pathogenesis and diagnostic criteria are comparable to adult BP, yet BP180 NC16A ELISA levels seem to be significantly higher in infants. The overall disease outcome is favorable. Based on the results of this study we propose a treatment algorithm for infantile BP.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-014-0185-6) contains supplementary material, which is available to authorized users.

Increasing incidence of bullous pemphigoid in Northern Finland: a retrospective database study in Oulu University Hospital.

Bullous pemphigoid (BP) is an autoimmune blistering skin disease of elderly people. Some studies have suggested that the incidence of BP has increased, but the diagnostic accuracy and methodology of studies have varied considerably. To examine the incidence of BP in Northern Finland, and whether the incidence has changed over time. This was a retrospective database study of all BP cases diagnosed in the Oulu University Hospital, Finland between 1985 and 2009. The diagnostic criteria were clinical features characteristic of BP (all patients) and positive direct or indirect immunofluorescence in the skin biopsy. The age-standardized incidences were calculated by the direct standardization method. Incidence rate ratios (IRR) were estimated by the Poisson regression model. To derive adjusted IRRs, age and sex were used as potential confounding factors. The crude incidence of BP was 17 per 1 million person-years [95% confidence interval (CI) 15-20] between 1985 and 2009. Using the general European population as a reference, the age-standardized incidence was 14 per 1 million person-years (95% CI 12-17). The incidence of BP increased 1·8-fold (IRR 1·8, 95% CI 1·3-2·6; P<0·001) in 2005-09 compared with the mean incidence of BP between 1985 and 2004, but after the adjustment for age and sex the increase was 1·4-fold (IRR 1·4, 95% CI 1·0-2·0; P=0·043). This is the first study with immunohistologically verified BP diagnoses that reports the increase in the incidence of BP in age- and sex-adjusted populations.

Autoimmune blistering skin diseases: diagnostic and therapeutic approach

Autoimmune blistering skin diseases: diagnostic and therapeutic approach

Hsp90 blockade modulates bullous pemphigoid IgG-induced IL-8 production by keratinocytes.

Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering skin disease characterized by autoantibodies against the hemidesmosomal proteins BP180 and BP230. The cell stress chaperone heat shock protein 90 (Hsp90) has been implicated in inflammatory responses, and recent evidence suggests that it represents a novel treatment target in autoimmune bullous diseases. The aim of the study was to investigate the contribution of Hsp90 to the proinflammatory cytokine production in keratinocytes induced by autoantibodies to BP180 from BP patient serum. HaCaT cells were treated with purified human BP or normal IgG in the absence or presence of the Hsp90 blocker 17-DMAG and effects on viability, interleukin 6 (IL-6) and IL-8 (cytokines critical for BP pathology), NFκB (their major transcription factor), and Hsp70 (marker of effective Hsp90 inhibition and potent negative regulator of inflammatory responses) were investigated. We found that BP IgG stimulated IL-6 and IL-8 release from HaCaT cells and that non-toxic doses of 17-DMAG inhibited this IL-8, but not IL-6 secretion in a dose- and time-dependent fashion. Inhibition of this IL-8 production was also observed at the transcriptional level. In addition, 17-DMAG treatment blunted BP IgG-mediated upregulation of NFκB activity and was associated with Hsp70 induction. This study provides important insights that Hsp90 is involved as crucial regulator in anti-BP180 IgG-induced production of keratinocyte-derived IL-8. By adding to the knowledge of the multimodal anti-inflammatory effects of Hsp90 blockade, our data further support the introduction of Hsp90 inhibitors into the clinical setting for treatment of autoimmune diseases, especially for BP.

CD1a, HAM56, CD68 and S-100 are present in lesional skin biopsies from patients affected by autoimmune blistering diseases

Introduction: Previous research on autoimmune skin blistering diseases (ABD) has primarily focused on the humoral immune response; moreover, little attention has been given to the potential role of the antigen presenting cells (APCs) in lesional skin. Aim: The purpose of our study was to immunophenotype selected APC in the lesional skin of ABDs, utilizing immunohistochemistry (IHC) stains. Materials and Methods: We utilized IHC to stain for dendritic cells (DC), staining with CD1a, CD68, HAM56, and S-100 in lesional skin from 30 patients with endemic pemphigus foliaceus (EPF), 15 controls from the EPF endemic area, and 15 healthy controls from the USA. We also tested archival biopsies from patients with selected ABD, including 30 patients with bullous pemphigoid (BP), 20 with pemphigus vulgaris (PV), 8 with pemphigus foliaceus (PF) and 14 with dermatitis herpetiformis (DH) and 2 with epidermolysis bullosa acquisita (EBA). Results: Cells stained by CD68, HAM56 and S-100 were present in the majority of the ABD skin biopsies; these cells were located primarily in perivascular infiltrates surrounding dermal vessels subjacent to the blisters. However, these cells were also noted within the blisters, in vessels supplying dermal eccrine glands and ducts, and in areas of dermal endothelial-mesenchymal cell junction-like structures, especially in BP cases. In our CD1a staining, the number and location of positive staining cells varied with each disease, being abundant in most ABD in the epidermis suprajacent to the blisters, or in the epidermis surrounding the blister site if the blister site epidermis was missing. In the control biopsies, most did not display positive IHC staining, with the exception of a few CD1a positive cells in the epidermis Conclusion: Our findings confirm positive IHC staining for APCs in areas of the skin besides the disease blisters. Our findings suggest that the antigen presentation in ABD proceeds in areas distant from the blister site. Further studies are needed to confirm our findings, and to explore their full significance.

HLA-DPDQDR is expressed in all lesional skin from patients with autoimmune skin diseases

Introduction: Human genes responsible for human antigen presentation and transplant rejection functions are located on the short arm of Chromosome 6, and are called the Major Histocompatibility Complex (MHC). Moreover, the primary physiologic function of MHC molecules is to present peptides to T lymphocytes. MHC molecules are integral components of the ligands that most T cells recognize, since the T cell receptor (TCR) has specificity for complexes of foreign antigenic peptides, as well as self-MHC molecules. Aim: Our investigation attempts to investigate the presence of HLA-DPDQDR within lesional skin biopsies from patients affected by autoimmune skin blistering diseases (ABDs). Materials and Methods: We utilized immunohistochemistry (IHC) to evaluate the presence of HLA-DPDQDR in lesional skin biopsies of patients affected by ABDs. We tested 30 patients with endemic pemphigus foliaceus (EPF), 15 controls from the EPF endemic area, and 15 biopsies from healthy controls from the USA. We also tested archival biopsies from patients with selected ABDs, including 30 patients with bullous pemphigoid (BP), 20 with pemphigus vulgaris (PV), 8 with pemphigus foliaceus (PF), 14 with dermatitis herpetiformis (DH) and 2 with epidermolysis bullosa acquisita (EBA). Results: Most ABD biopsies stained positive for HLA-DPDQDR in the lesional blisters and/or inflamed neurovascular neuroplexus areas in the superficial dermis, and also at mesenchymal-endothelial like-cell junctions in the dermis. In BP, EBA and EPF, the HLA-DPDQDR staining was also seen in dermal eccrine sweat gland coils and ducts. Conclusion: We document that HLA-DPDQDR is expressed in several anatomic areas of lesional skin in patients with ABDs. Notably, HLADPDQDR positivity was also consistently present in areas of the classic immune response, including epidermal intercellular junctions in pemphigus, and at basement membrane sites in bullous pemphigoid and other subepidermal blistering diseases.

Plakophilin-1 Protects Keratinocytes from Pemphigus Vulgaris IgG by Forming Calcium-Independent Desmosomes

Plakophilin-1 (PKP-1) is an armadillo family protein critical for desmosomal adhesion and epidermal integrity. In the autoimmune skin blistering disease pemphigus vulgaris (PV), autoantibodies (IgG) target the desmosomal cadherin desmoglein 3 (Dsg3) and compromise keratinocyte cell-cell adhesion. Here, we report that enhanced expression of PKP-1 protects keratinocytes from PV IgG-induced loss of cell-cell adhesion. PKP-1 prevents loss of Dsg3 and other desmosomal proteins from cell-cell borders and prevents alterations in desmosome ultrastructure in keratinocytes treated with PV IgG. Using a series of Dsg3 chimeras and deletion constructs, we find that PKP-1 clusters Dsg3 with the desmosomal plaque protein desmoplakin in a manner dependent upon the plakoglobin binding domain of the Dsg3 tail. Furthermore, PKP-1 expression transforms desmosome adhesion from a calcium-dependent to a calcium-independent and hyper-adhesive state. These results demonstrate that manipulating the expression of a single desmosomal plaque protein can block the pathogenic effects of PV IgG on keratinocyte adhesion.

Specific immunoadsorption of pathogenic autoantibodies in pemphigus requires the entire ectodomains of desmogleins

Pemphigus foliaceus (PF) and pemphigus vulgaris (PV) are life-threatening autoimmune blistering skin diseases. They are characterized by circulating autoantibodies which bind to the ectodomains of desmoglein (Dsg) 1 and Dsg3. These antibodies induce acantholysis in skin and mucous membranes. In severe cases of pemphigus, immunoadsorption is applied to remove total IgG from patient plasma using protein A or other ligands. To develop a specific adsorber for anti-Dsg antibodies, epitope mapping studies of Dsg1 and Dsg3 ectodomains were conducted. Dsg variants were expressed on the surface of HEK-293 cells and analysed for reactivity with pemphigus and control sera by indirect immunofluorescence technique. For Dsg1, a construct consisting of domain 1 directly fused to domain 5, seemed to be suitable for specific immunoadsorption of anti-Dsg1 antibodies. The recognized epitopes were mainly conformation-dependent. However, adsorption of pemphigus foliaceus IgG using this protein coupled to a Sepharose matrix did not completely remove pathogenicity from the sera, as proven by a keratinocyte dissociation assay. In contrast, full-length Dsg1 and Dsg3 ectodomains were able to specifically adsorb anti-Dsg antibodies and to efficiently eliminate pathogenicity. Therefore, the complete and correctly folded ectodomains of both desmogleins are required for therapeutic immunoadsorption.

Broad requirement for terminal sialic acid residues and FcγRIIB for the preventive and therapeutic activity of intravenous immunoglobulins in vivo

Intravenous immunoglobulin (IVIg) therapy is widely used to treat a variety of autoimmune diseases including immunothrombocytopenia, chronic inflammatory demyelinating polyneuropathy, and more recently autoimmune skin blistering diseases. Despite this well-documented clinical success, the precise molecular and cellular mechanisms underlying this immunomodulatory activity are discussed controversially. In particular, the clinically relevant therapeutic pathway of IVIg-mediated immune modulation has not been studied in detail. In the present study, we use four independent in vivo model systems of auto-Ab-mediated autoimmune disease to identify a common pathway explaining IVIg activity under therapeutic conditions in vivo. We show that irrespective of the in vivo model system, IVIg activity is strictly dependent on the presence of terminal sialic acid residues and the inhibitory FcγRIIB under preventive as well as therapeutic treatment conditions. In contrast, specific ICAM3 grabbing nonintegrin related 1, previously demonstrated to be essential under preventative treatment conditions, showed a disease-specific impact on IVIg-mediated resolution of established autoimmune disease.