Autoimmune and infectious skin diseases that target desmogleins

Exploring the depths of IgG4: insights into autoimmunity and novel treatments

IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.

Association of Human Endogenous Retrovirus-W (HERV-W) Copies with Pemphigus Vulgaris

BACKGROUND

Pemphigus is classified as a group of chronic, recurrent, and potentially fatal bullous autoimmune diseases that leads to blisters and skin lesions resulting from IgG antibodies and the loss of cellular connections in the epidermis. Human endogenous retrovirus (HERV) sequences and their products (RNA, cytosolic DNA, and proteins) can modulate the immune system and contribute to autoimmunity. The extent to which, HERV-W env copies may be involved in the pathogenesis of pemphigus remains to be elucidated.

AIM

This study aimed to comparatively evaluate the relative levels of HERV-W env DNA copy numbers in the peripheral blood mononuclear cells (PBMCs) of pemphigus vulgaris patients and healthy controls.

METHODS

Thirty-one pemphigus patients and the corresponding age- and sex-matched healthy controls were included in the study. The relative levels of HERV-W env DNA copy numbers were then evaluated by qPCR using specific primers, in the PBMCs of the patients and controls.

RESULTS

Our results indicated that relative levels of HERV-W env DNA copy numbers in the patients were significantly higher than that in the controls (1.67±0.86 vs. 1.17±0.75; p = 0.02). There was also a significant difference between the HERV-W env copies of male and female patients (p = 0.001). Furthermore, there was no relationship between the HERV-W env copy number and disease onset (p = 0.19) . According to the obtained data, we could not find any relationship between the HERV-W env copy number and serum Dsg1(p=0.86) and Dsg3 (p=0.76) levels.

CONCLUSION

Our results indicated a positive link between the HERV-W env copies and pathogenesis of pemphigus. The association between clinical severity score and HERVW env copies in the PBMCs as a biomarker for pemphigus needs further studies.

A Multispecialty Approach to the Identification and Diagnosis of Nonaccidental Trauma in Children

Child abuse is a preventable phenomenon of considerable concern resulting in significant child mortality and morbidity. We analyze various abuse lesions such as radiological (visceral and skeletal lesions and those associated with head trauma) and cutaneous (burns, bruises, bites, etc.) to enhance streamlined identification of injuries in cases of physical child abuse. For effective results, it is essential to remain mindful of all background factors, such as the caregiver setting and the prevalence of child maltreatment in the concerned community while acknowledging the possibility of natural causes (genetic diseases such as osteogenesis imperfecta and hemophilia, or acquired abnormalities) that can mimic NAT and cause confusion in diagnosis and treatment. The margin of error in cases of abuse is negligible, therefore, making its diagnosis a momentous as well as challenging clinical task. An ineffective diagnosis can have detrimental emotional consequences for the family and may even expose the child to future potentially fatal episodes of abuse. Hence, there is a need to direct special focus on the importance of accurate history taking and immediate, responsible reporting to authorities, as well as to child protective services. Therefore, considering the multifactorial approach this subject requires, this review aims to delve into prevalence statistics, various risk factors, and their effect on psychological health to offer a near-complete regulation to ensure an effective understanding of NAT on part of doctors, social workers, and other relevant authorities.

Inhibition of desmoglein-1 by aspirin leads to synthetic lethality of keratinocytes in Shuanghuanglian-induced cutaneous eruption response

Cutaneous eruptions caused by the combination of Chinese and Western medicine have attracted widespread attention; however, the underlying mechanism remains unclear. This study aimed to evaluate the potential mechanism of cutaneous eruptions in vivo and in vitro using the combination of Shuanghuanglian injection powder (SHL) and aspirin (ASA) as an example. ASA and SHL co-administration induced inflammatory responses in HaCat cells, as evidenced by marked increases in the expression of IL-4 and TNF-α, and the level of apoptosis. Additionally, histopathological investigation of mice skin tissues showed local inflammatory cell infiltration. Western boltting was used to detect the effects of ASA on desmoglein-1 (DSG1) expression; we found that DSG1 expression was down-regulated in vivo and in vitro. Finally, the key components of SHL were administered to HaCat cells with down-regulated DSG1; it was seen that neochlorogenic acid and rutin have a significant effect on HaCat cell apoptosis. These results demonstrate that DSG1 deficiency is a potential cause of cutaneous eruptions caused by the combination of SHL and ASA, and neochlorogenic acid and rutin are the main allergenic components. This study provides a new research strategy for the safety evaluation of integrated traditional Chinese and Western medicine.

Oral pemphigus vulgaris: dentists take-home message

Pemphigus is a life-threatening disease but timely recognition of oral lesions is critical to prevent serious cutaneous and fatal complications.

Oxidative Stress-Mediated YAP Dysregulation Contributes to the Pathogenesis of Pemphigus Vulgaris

Pemphigus Vulgaris (PV) is a life-threatening autoimmune disease manifested with blisters in the skin and mucosa and caused by autoantibodies against adhesion protein desmoglein-3 (Dsg3) expressed in epithelial membrane linings of these tissues. Despite many studies, the pathogenesis of PV remains incompletely understood. Recently we have shown Dsg3 plays a role in regulating the yes-associated protein (YAP), a co-transcription factor and mechanical sensor, and constraining reactive oxygen species (ROS). This study investigated the effect of PV sera as well as the anti-Dsg3 antibody AK23 on these molecules. We detected elevated YAP steady-state protein levels in PV cells surrounding blisters and perilesional regions and in keratinocytes treated with PV sera and AK23 with concomitant transient ROS overproduction. Cells treated with hydrogen peroxide also exhibited augmented nuclear YAP accompanied by reduction of Dsg3 and α-catenin, a negative regulator of YAP. As expected, transfection of α-catenin-GFP plasmid rendered YAP export from the nucleus evoked by hydrogen peroxide. In addition, suppression of total YAP was observed in hydrogen peroxide treated cells exposed to antioxidants with enhanced cell-cell adhesion being confirmed by decreased fragmentation in the dispase assay compared to hydrogen peroxide treatment alone. On the other hand, the expression of exogenous YAP disrupted intercellular junction assembly. In contrast, YAP depletion resulted in an inverse effect with augmented expression of junction assembly proteins, including Dsg3 and α-catenin capable of abolishing the effect of AK23 on Dsg3 expression. Finally, inhibition of other kinase pathways, including p38MAPK, also demonstrated suppression of YAP induced by hydrogen peroxide. Furthermore, antioxidant treatment of keratinocytes suppressed PV sera-induced total YAP accumulation. In conclusion, this study suggests that oxidative stress coupled with YAP dysregulation attributes to PV blistering, implying antioxidants may be beneficial in the treatment of PV.

The Role of Desmoglein 1 in Gap Junction Turnover Revealed through the Study of SAM Syndrome

An effective epidermal barrier requires structural and functional integration of adherens junctions, tight junctions, gap junctions (GJ), and desmosomes. Desmosomes govern epidermal integrity while GJs facilitate small molecule transfer across cell membranes. Some patients with severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome, caused by biallelic desmoglein 1 (DSG1) mutations, exhibit skin lesions reminiscent of erythrokeratodermia variabilis, caused by mutations in connexin (Cx) genes. We, therefore, examined whether SAM syndrome-causing DSG1 mutations interfere with Cx expression and GJ function. Lesional skin biopsies from SAM syndrome patients (n = 7) revealed decreased Dsg1 and Cx43 plasma membrane localization compared with control and nonlesional skin. Cultured keratinocytes and organotypic skin equivalents depleted of Dsg1 exhibited reduced Cx43 expression, rescued upon re-introduction of wild-type Dsg1, but not Dsg1 constructs modeling SAM syndrome-causing mutations. Ectopic Dsg1 expression increased cell-cell dye transfer, which Cx43 silencing inhibited, suggesting that Dsg1 promotes GJ function through Cx43. As GJA1 gene expression was not decreased upon Dsg1 loss, we hypothesized that Cx43 reduction was due to enhanced protein degradation. Supporting this, PKC-dependent Cx43 S368 phosphorylation, which signals Cx43 turnover, increased after Dsg1 depletion, while lysosomal inhibition restored Cx43 levels. These data reveal a role for Dsg1 in regulating epidermal Cx43 turnover.

Desmoglein1 Deficiency Is a Potential Cause of Cutaneous Eruptions Induced by Shuanghuanglian Injection

Cutaneous eruption is a common drug-adverse reaction, characterised by keratinocytes inflammation and apoptosis. Shuanghuanglian injeciton (SHLI) is a typical Chinese medicine injection, which is used to treat influenza. It has been reported that SHLI has the potential to induce cutaneous adverse eruptions. However, the mechanisms remain unclear. Since desmoglein 1 (DSG1) shows a crucial role in maintaining skin barrier function and cell susceptibility, we assume that DSG1 plays a critical role in the cutaneous eruptions induced by SHLI. In our study, retinoic acid (RA) was selected to downregulate the DSG1 expression, and lipopolysaccharide (LPS) was first used to identify the susceptibility of the DSG1-deficiency Hacat cells. Then, SHLI was administrated to normal or DSG1-deficient Hacat cells and mice. The inflammatory factors and apoptosis rate were evaluated by RT-PCR and flow cytometry. The skin pathological morphology was observed by hematoxylin and eosin (HE) staining. Our results show that treated only with SHLI could not cause IL-4 and TNF-α mRNA increases in normal Hacat cells. However, in the DSG1-deficient Hacat cells or mice, SHLI induced an extreme increase of IL-4 and TNF-α mRNA levels, as well as in the apoptosis rate. The skin tissue showed a local inflammatory cell infiltration when treated with SHIL in the DSG1-deficient mice. Thus, we concluded that DSG1 deficiency was a potential causation of SHLI induced eruptions. These results indicated that keratinocytes with DSG1 deficiency were likely to induce the cutaneous eruptions when stimulated with other medicines.

Streptococcal Cysteine Protease-Mediated Cleavage of Desmogleins Is Involved in the Pathogenesis of Cutaneous Infection

Streptococcus pyogenes is responsible for a wide variety of cutaneous infections ranging from superficial impetigo to fulminant invasive necrotizing fasciitis. Dysfunction of desmosomes is associated with the pathogenesis of cutaneous diseases. We identified streptococcal pyrogenic exotoxin B (SpeB) as a proteolytic factor that cleaves the extracellular domains of desmoglein 1 and 3. In an epicutaneous infection model, lesional skin infected with an speB deletion mutant were significantly smaller as compared to those caused by the wild-type strain. Furthermore, immunohistological analysis indicated cleavage of desmogleins that developed around the invasion site of the wild-type strain. In contrast, the speB mutant was preferentially found on the epidermis surface layer. Taken together, our findings provide evidence that SpeB-mediated degradation of desmosomes has a pathogenic role in development of S. pyogenes cutaneous infection.

Nasal, oral, and pharyngolaryngeal manifestations of pemphigus vulgaris: Endoscopic ororhinolaryngologic examination

Pemphigus vulgaris is an autoimmune blistering disorder that involves the skin and mucous membranes. Few reports have described nasal and oropharyngolaryngeal lesions in pemphigus vulgaris using an endoscopic ororhinolaryngologic examination. We retrospectively reviewed the clinical records of 11 patients with pemphigus vulgaris between 2001 and 2013 with respect to their symptoms, lesion sites, lesion features, and treatments received. All patients had undergone an endoscopic ororhinolaryngologic examination. Their mucosa-related symptoms were sore throat, oral pain, odynophagia, gingival bleeding, hoarseness, and epistaxis. The most frequent sites were the oral cavity (gingiva and buccal mucosa), larynx (epiglottis and vocal fold), oropharynx (soft palate), and nasal cavity (nasal septum). Lesions were typically characterized by erosion, erosion with a whitish exudate, and erythematous patches. Thus, our study findings reveal that pemphigus vulgaris involves both the nasal and oropharyngolaryngeal regions. Patients with pemphigus vulgaris should undergo an endoscopic ororhinolaryngologic examination to determine the range of their lesions.

Auxiliary activation of the complement system and its importance for the pathophysiology of clinical conditions

Activation and regulation of the cascade systems of the blood (the complement system, the coagulation/contact activation/kallikrein system, and the fibrinolytic system) occurs via activation of zymogen molecules to specific active proteolytic enzymes. Despite the fact that the generated proteases are all present together in the blood, under physiological conditions, the activity of the generated proteases is controlled by endogenous protease inhibitors. Consequently, there is remarkable little crosstalk between the different systems in the fluid phase. This concept review article aims at identifying and describing conditions where the strict system-related control is circumvented. These include clinical settings where massive amounts of proteolytic enzymes are released from tissues, e.g., during pancreatitis or post-traumatic tissue damage, resulting in consumption of the natural substrates of the specific proteases and the available protease inhibitor. Another example of cascade system dysregulation is disseminated intravascular coagulation, with canonical activation of all cascade systems of the blood, also leading to specific substrate and protease inhibitor elimination. The present review explains basic concepts in protease biochemistry of importance to understand clinical conditions with extensive protease activation.

Desmosomes and Intermediate Filaments: Their Consequences for Tissue Mechanics

Adherens junctions (AJs) and desmosomes connect the actin and keratin filament networks of adjacent cells into a mechanical unit. Whereas AJs function in mechanosensing and in transducing mechanical forces between the plasma membrane and the actomyosin cytoskeleton, desmosomes and intermediate filaments (IFs) provide mechanical stability required to maintain tissue architecture and integrity when the tissues are exposed to mechanical stress. Desmosomes are essential for stable intercellular cohesion, whereas keratins determine cell mechanics but are not involved in generating tension. Here, we summarize the current knowledge of the role of IFs and desmosomes in tissue mechanics and discuss whether the desmosome-keratin scaffold might be actively involved in mechanosensing and in the conversion of chemical signals into mechanical strength.

A reciprocal HLA-Disease Association in Rheumatoid Arthritis and Pemphigus Vulgaris

Human leukocyte antigens (HLA) have been extensively studied as being antigen presenting receptors, but many aspects of their function remain elusive, especially their association with various autoimmune diseases. Here we discuss an illustrative case of the reciprocal relationship between certain HLA-DRB1 alleles and two diseases, rheumatoid arthritis (RA) and pemphigus vulgaris (PV). RA is strongly associated with HLA-DRB1 alleles that encode a five amino acid sequence motif in the 70-74 region of the DR beta chain, called the shared epitope (SE), while PV is associated with the HLA-DRB1*04:02 allele that encodes a different sequence motif in the same region. Interestingly, while HLA-DRB1*04:02 confers susceptibility to PV, this and other alleles that encode the same sequence motif in the 70-74 region of the DR beta chain are protective against RA. Currently, no convincing explanation for this antagonistic effect is present. Here we briefly review the immunology and immunogenetics of both diseases, identify remaining gaps in our understanding of their association with HLA, and propose the possibility that the 70-74 DR beta epitope may contribute to disease risk by mechanisms other than antigen presentation.

Pathophysiology of the Desmo-Adhesome

Advances in our understanding of desmosomal diseases have provided a clear demonstration of the key role played by desmosomes in tissue and organ physiology, highlighting the importance of their dynamic and finely regulated structure. In this context, non-desmosomal regulatory molecules have acquired increasing relevance in the study of this organelle resulting in extending the desmosomal interactome, named the "desmo-adhesome." Spatiotemporal changes in the expression and regulation of the desmo-adhesome underlie a number of genetic, infectious, autoimmune, and malignant conditions. The aim of the present article was to examine the structural and functional relationship of the desmosome, by providing a comprehensive, yet focused overview of the constituents targeted in human disease. The inclusion of the novel regulatory network in the desmo-adhesome pathophysiology opens new avenues to a deeper understanding of desmosomal diseases, potentially unveiling pathogenic mechanisms waiting to be explored. J. Cell. Physiol. 232: 496-505, 2017. © 2016 Wiley Periodicals, Inc.

Desmosomes in disease: a guide for clinicians

The large number of diseases occurring when desmosome constituents are impaired provides striking evidence for the key role of desmosomes in maintaining tissue integrity. A detailed understanding of the molecular alterations causing desmosomal dysfunction has, in turn, underpinned the development of novel diagnostic tools. This has salient clinical implications for dentists and oral medicine practitioners because the majority of desmosomal diseases affect the oral cavity. In the present article, we review the autoimmune, infectious, genetic, and neoplastic diseases that target the desmosome, with particular emphasis on clinical manifestations, diagnostic pathways, and relevant laboratory investigations.

Super-Resolution Microscopy Reveals Altered Desmosomal Protein Organization in Tissue from Patients with Pemphigus Vulgaris

Pemphigus vulgaris (PV) is an autoimmune epidermal blistering disease in which autoantibodies (IgG) are directed against the desmosomal cadherin desmoglein 3 (Dsg3). In order to better understand how PV IgG alters desmosome morphology and function in vivo, PV patient biopsies were analyzed by structured illumination microscopy (SIM), a form of super-resolution fluorescence microscopy. In patient tissue, desmosomal proteins were aberrantly clustered and localized to PV IgG-containing endocytic linear arrays. Patient IgG also colocalized with markers for lipid rafts and endosomes. Additionally, steady-state levels of Dsg3 were decreased and desmosomes were reduced in size in patient tissue. Desmosomes at blister sites were occasionally split, with PV IgG decorating the extracellular faces of split desmosomes. Desmosome splitting was recapitulated in vitro by exposing cultured keratinocytes both to PV IgG and to mechanical stress, demonstrating that splitting at the blister interface in patient tissue is due to compromised desmosomal adhesive function. These findings indicate that Dsg3 clustering and endocytosis are associated with reduced desmosome size and adhesion defects in PV patient tissue. Further, this study reveals that super-resolution optical imaging is powerful approach for studying epidermal adhesion structures in normal and diseased skin.

Oral pemphigus vulgaris: A case report with direct immunofluorescence study

Pemphigus vulgaris (PV) is a chronic, autoimmune, intraepidermal blistering disease of the skin and mucous membranes. The initial clinical manifestation is frequently the development of intraoral lesions, and later, the lesions involve the other mucous membranes and skin. The etiology of this disease still remains obscure although the presence of autoantibodies is consistent with an autoimmune disease. These antibodies are targeted against the adhesion proteins of keratinocytes, leading to acantholysis (disruption of spinous layer, leading to intraepidermal clefting) and blister formation. Because only oral lesions are present initially, the chances of misdiagnosing the disease as another condition are increased, leading to inappropriate therapy. In this article, we report a case of PV with only oral manifestations in a 36-year-old male.

Desmosomes in acquired disease

Desmosomes are cell-cell junctions that mediate adhesion and couple the intermediate filament cytoskeleton to sites of cell-cell contact. This architectural arrangement integrates adhesion and cytoskeletal elements of adjacent cells. The importance of this robust adhesion system is evident in numerous human diseases, both inherited and acquired, which occur when desmosome function is compromised. This review focuses on autoimmune and infectious diseases that impair desmosome function. In addition, we discuss emerging evidence that desmosomal genes are often misregulated in cancer. The emphasis of our discussion is placed on the way in which human diseases can inform our understanding of basic desmosome biology and in turn, the means by which fundamental advances in the cell biology of desmosomes might lead to new treatments for acquired diseases of the desmosome.

Cell adhesion in epidermal development and barrier formation

Cell-cell adhesions are necessary for structural integrity and barrier formation of the epidermis. Here, we discuss insights from genetic and cell biological studies into the roles of individual cell-cell junctions and their composite proteins in regulating epidermal development and function. In addition to individual adhesive functions, we will discuss emerging ideas on mechanosensation/transduction of junctions in the epidermis, noncanonical roles for adhesion proteins, and crosstalk/interdependencies between the junctional systems. These studies have revealed that cell adhesion proteins are connected to many aspects of tissue physiology including growth control, differentiation, and inflammation.

Cell-cell adhesions and cell contractility are upregulated upon desmosome disruption

Desmosomes are perturbed in a number of disease states – including genetic disorders, autoimmune and bacterial diseases. Here, we report unexpected changes in other cell-cell adhesion structures upon loss of desmosome function. We found that perturbation of desmosomes by either loss of the core desmosomal protein desmoplakin or treatment with pathogenic anti-desmoglein 3 (Dsg3) antibodies resulted in changes in adherens junctions consistent with increased tension. The total amount of myosin IIA was increased in desmoplakin-null epidermis, and myosin IIA became highly localized to cell contacts in both desmoplakin-null and anti-Dsg3-treated mouse keratinocytes. Inhibition of myosin II activity reversed the changes to adherens junctions seen upon desmosome disruption. The increased cortical myosin IIA promoted epithelial sheet fragility, as myosin IIA-null cells were less susceptible to disruption by anti-Dsg3 antibodies. In addition to the changes in adherens junctions, we found a significant increase in the expression of a number of claudin genes, which encode for transmembrane components of the tight junction that provide barrier function. These data demonstrate that desmosome disruption results in extensive transcriptional and posttranslational changes that alter the activity of other cell adhesion structures.

Autoimmunity versus autoinflammation--friend or foe?

"Autoimmunity" is a designation dependent on the conventional immunological issue of self/non-self discrimination. Identification of novel target autoantigens is still an important issue ongoing in classical tissue-specific autoimmune bullous diseases and autoimmune connective tissue diseases. In contrast, synchronized with the paradigm shift of the fundamental aspect of immunity to danger sensing/signaling, distinct collagen-like diseases have been defined by the genetic mutations causing dysregulated innate immunity/inflammation and have been designated as “autoinflammatory”diseases. Due to the clinical and etiological similarities,the concept of autoinflammatory diseases has expanded to include non-hereditary collagen-like diseases, tissue-specific chronic idiopathic inflammatory diseases and metabolic diseases. On the other hand, various genetic causes of autoimmune diseases have been identified and the border of these two pathophysiologies is becoming obscure. Instead, a variable mixture of both autoimmunity and autoinflammation can cause each inflammatory phenotype with a variable level of antigen specificity

Desmosome assembly and disassembly are membrane raft-dependent

Strong intercellular adhesion is critical for tissues that experience mechanical stress, such as the skin and heart. Desmosomes provide adhesive strength to tissues by anchoring desmosomal cadherins of neighboring cells to the intermediate filament cytoskeleton. Alterations in assembly and disassembly compromise desmosome function and may contribute to human diseases, such as the autoimmune skin blistering disease pemphigus vulgaris (PV). We previously demonstrated that PV auto-antibodies directed against the desmosomal cadherin desmoglein 3 (Dsg3) cause loss of adhesion by triggering membrane raft-mediated Dsg3 endocytosis. We hypothesized that raft membrane microdomains play a broader role in desmosome homeostasis by regulating the dynamics of desmosome assembly and disassembly. In human keratinocytes, Dsg3 is raft associated as determined by biochemical and super resolution immunofluorescence microscopy methods. Cholesterol depletion, which disrupts rafts, prevented desmosome assembly and adhesion, thus functionally linking rafts to desmosome formation. Interestingly, Dsg3 did not associate with rafts in cells lacking desmosomal proteins. Additionally, PV IgG-induced desmosome disassembly occurred by redistribution of Dsg3 into raft-containing endocytic membrane domains, resulting in cholesterol-dependent loss of adhesion. These findings demonstrate that membrane rafts are required for desmosome assembly and disassembly dynamics, suggesting therapeutic potential for raft targeting agents in desmosomal diseases such as PV.

Clinical and immunologic characterization in 26 Indian pemphigus patients

BACKGROUND

Pemphigus shows geographically variable characteristics.

OBJECTIVE

To study the clinical and immunologic characteristics of Indian pemphigus patients before and after treatment.

METHODS

Twenty-six Indian pemphigus patients were analyzed with regard to age, gender, clinical features, treatments and response, the results of histopathology, direct and indirect immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), and immunoblot analyses.

RESULTS

There were 22 pemphigus vulgaris (PV) and 4 pemphigus foliaceus (PF) patients. Direct and indirect IF was positive in 95.8% and 56% of patients, respectively. Indices of ELISA were lower in our study. Immunoblot assays detected the 130 kDa desmoglein-3 in 10 PV patients and the 160 kDa desmoglein-1 in 1 PV patient; 190 kDa periplakin was unexpectedly detected in 8 patients.

CONCLUSION

Indian pemphigus patients showed several unique characteristics, including younger population, predominance of PV, low ELISA indices, lower sensitivity of indirect IF and immunoblotting, and the presence of the 190 kDa periplakin in nearly one-third of patients.

Evasion of mucosal defenses during Aeromonas hydrophila infection of channel catfish (Ictalurus punctatus) skin

The mucosal surfaces of fish serve as the first line of defense against the myriad of aquatic pathogens present in the aquatic environment. The immune repertoire functioning at these interfaces is still poorly understood. The skin, in particular, must process signals from several fronts, sensing and integrating environmental, nutritional, social, and health cues. Pathogen invasion can disrupt this delicate homeostasis with profound impacts on signaling throughout the organism. Here, we investigated the transcriptional effects of virulent Aeromonas hydrophila infection in channel catfish skin, Ictalurus punctatus. We utilized a new 8 × 60 K Agilent microarray for catfish to examine gene expression profiles at critical early timepoints following challenge--2 h, 8 h, and 12 h. Expression of a total of 2,168 unique genes was significantly perturbed during at least one timepoint. We observed dysregulation of genes involved in antioxidant, cytoskeletal, immune, junctional, and nervous system pathways. In particular, A. hydrophila infection rapidly altered a number of potentially critical lectins, chemokines, interleukins, and other mucosal factors in a manner predicted to enhance its ability to adhere to and invade the catfish host.

Signaling dependent and independent mechanisms in pemphigus vulgaris blister formation

Pemphigus vulgaris (PV) is an autoimmune epidermal blistering disease caused by autoantibodies directed against the desmosomal cadherin desmoglein-3 (Dsg3). Significant advances in our understanding of pemphigus pathomechanisms have been derived from the generation of pathogenic monoclonal Dsg3 antibodies. However, conflicting models for pemphigus pathogenicity have arisen from studies using either polyclonal PV patient IgG or monoclonal Dsg3 antibodies. In the present study, the pathogenic mechanisms of polyclonal PV IgG and monoclonal Dsg3 antibodies were directly compared. Polyclonal PV IgG cause extensive clustering and endocytosis of keratinocyte cell surface Dsg3, whereas pathogenic mouse monoclonal antibodies compromise cell-cell adhesion strength without causing these alterations in Dsg3 trafficking. Furthermore, tyrosine kinase or p38 MAPK inhibition prevents loss of keratinocyte adhesion in response to polyclonal PV IgG. In contrast, disruption of adhesion by pathogenic monoclonal antibodies is not prevented by these inhibitors either in vitro or in human skin explants. Our results reveal that the pathogenic activity of polyclonal PV IgG can be attributed to p38 MAPK-dependent clustering and endocytosis of Dsg3, whereas pathogenic monoclonal Dsg3 antibodies can function independently of this pathway. These findings have important implications for understanding pemphigus pathophysiology, and for the design of pemphigus model systems and therapeutic interventions.

Characterization of a variety of neutralizing anti-heparin-binding epidermal growth factor-like growth factor monoclonal antibodies by different immunization methods

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the epidermal growth factor family. The accumulated evidence on the tumor-progressing roles of HB-EGF has suggested that HB-EGF-targeted cancer therapy is expected to be promising. However, the generation of neutralizing anti-HB-EGF monoclonal antibodies (mAbs) has proved difficult. To overcome this difficulty, we performed a hybridoma approach using mice from different genetic backgrounds, as well as different types of HB-EGF immunogens. To increase the number of hybridoma clones to screen, we used an electrofusion system to generate hybridomas and a fluorometric microvolume assay technology to screen anti-HB-EGF mAbs. We succeeded in obtaining neutralizing anti-HB-EGF mAbs, primarily from BALB/c and CD1 mice, and these were classified into 7 epitope bins based on their competitive binding to the soluble form of HB-EGF (sHB-EGF). The mAbs showed several epitope bin-dependent characteristics, including neutralizing and binding activity to human sHB-EGF, cross-reactivity to mouse/rat sHB-EGF and binding activity to the precursor form of HB-EGF. The neutralizing activity was also validated in colony formation assays. Interestingly, we found that the populations of mAb bins and the production rates of the neutralizing mAbs were strikingly different by mouse strain and by immunogen type. We succeeded in generating a variety of neutralizing anti-HB-EGF mAbs, including potent sHB-EGF neutralizers that may have potential as therapeutic agents for treating HB-EGF-dependent cancers. Our results also suggest that immunization approaches using different mouse strains and immunogen types affect the biological activity of individual neutralizing antibodies.

Pemphigus vulgaris in a pregnant woman and her neonate

A 23-year-old pregnant woman in her second trimester of pregnancy presented with blisters on the face, abdomen and the leg. Based on the clinical presentation and skin biopsy (histopathology and direct immunofluorescence) the diagnosis of pemphigus vulgaris was established. The child born to this patient also had similar skin lesions. The lesions in the mother and the child improved after treatment. The authors report a rare case of pemphigus vulgaris in a pregnant lady and neonatal pemphigus in her child, both of whom were treated successfully.

Alopecia as a rare but distinct manifestation of pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) patients may develop scalp erosions, however, the development of alopecia has been reported to be extremely rare.

OBJECTIVE

To delineate the clinicopathological features of alopecia in PV and provide insight into the pathogenesis of this rarely observed manifestation.

METHODS

A retrospective case note review was performed on five PV patients presenting with progressive hair loss and alopecic patches. Data were collected on demographics and clinical findings. Results for hair pull tests, direct immunofluorescence study of plucked hairs, established laboratory tests to detect anti-desmoglein 1 and 3 autoantibodies and scalp swab culture were recorded. A combination of vertical and horizontal sectioning technique enabled detailed histopathological analysis of alopecic patches. Clinical course was monitored.

RESULTS

Anagen hair follicles with the outer root sheath structure were easily pulled from perilesional scalp, with intercellular IgG deposition on the outer root sheath keratinocytes. Acantholysis between outer root sheath keratinocytes extending from the infundibulum to suprabalbar level was evident in anagen hair follicles of affected lesions. Perifollicular cell infiltration was observed in the lesions where scalp swabs detected micro-organisms. The bulge stem cell area was mostly intact. Alopecia was non-scarring and following 4 weeks of therapy hair re-growth was seen in all patients.

CONCLUSION

In PV, the combination of anti-desmoglein autoantibody-mediated acantholysis in conjunction with secondary factors, such as inflammatory changes due to infection, may cause weakening of hair follicle anchorage resulting in hair loss and alopecic patches. This unusual clinical phenotype should alert physicians to PV as a potential diagnosis.

Modulation of connexin signaling by bacterial pathogens and their toxins

Inherent to their pivotal tasks in the maintenance of cellular homeostasis, gap junctions, connexin hemichannels, and pannexin hemichannels are frequently involved in the dysregulation of this critical balance. The present paper specifically focuses on their roles in bacterial infection and disease. In particular, the reported biological outcome of clinically important bacteria including Escherichia coli, Shigella flexneri, Yersinia enterocolitica, Helicobacter pylori, Bordetella pertussis, Aggregatibacter actinomycetemcomitans, Pseudomonas aeruginosa, Citrobacter rodentium, Clostridium species, Streptococcus pneumoniae, and Staphylococcus aureus and their toxic products on connexin- and pannexin-related signaling in host cells is reviewed. Particular attention is paid to the underlying molecular mechanisms of these effects as well as to the actual biological relevance of these findings.

Altered desmosomal proteins in granulomatous myocarditis and potential pathogenic links to arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Immunoreactive signal for the desmosomal protein plakoglobin (γ-catenin) is reduced at cardiac intercalated disks in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), a highly arrhythmogenic condition caused by mutations in genes encoding desmosomal proteins. Previously, we observed a false-positive case in which plakoglobin signal was reduced in a patient initially believed to have ARVC but who actually had cardiac sarcoidosis. Sarcoidosis can masquerade clinically as ARVC but has not been previously associated with altered desmosomal proteins.

METHODS AND RESULTS

We observed marked reduction in immunoreactive signal for plakoglobin at cardiac myocyte junctions in patients with sarcoidosis and giant cell myocarditis, both highly arrhythmogenic forms of myocarditis associated with granulomatous inflammation. In contrast, plakoglobin signal was not depressed in lymphocytic (nongranulomatous) myocarditis. To determine whether cytokines might promote dislocation of plakoglobin from desmosomes, we incubated cultures of neonatal rat ventricular myocytes with selected inflammatory mediators. Brief exposure to low concentrations of interleukin (IL)-17, tumor necrosis factor-α (TNF-α), and IL-6 (cytokines implicated in granulomatous myocarditis) caused translocation of plakoglobin from cell-cell junctions to intracellular sites, whereas other potent cytokines implicated in nongranulomatous myocarditis had no effect, even at much higher concentrations. We also observed myocardial expression of IL-17 and TNF-α and elevated levels of serum inflammatory mediators, including IL-6R, IL-8, monocyte chemoattractant protein 1, and macrophage inflammatory protein 1β, in patients with ARVC (all P<0.0001 compared with controls).

CONCLUSIONS

The results suggest novel disease mechanisms involving desmosomal proteins in granulomatous myocarditis and implicate cytokines, perhaps derived in part from the myocardium, in disruption of desmosomal proteins and arrhythmogenesis in ARVC.

Desmoglein 3-specific CD4+ T cells induce pemphigus vulgaris and interface dermatitis in mice

Pemphigus vulgaris (PV) is a severe autoimmune disease involving blistering of the skin and mucous membranes. It is caused by autoantibodies against desmoglein 3 (Dsg3), an adhesion molecule critical for maintaining epithelial integrity in the skin, oral mucosa, and esophagus. Knowing the antigen targeted by the autoantibodies renders PV a valuable model of autoimmunity. Recently, a role for Dsg3-specific CD4+ T helper cells in autoantibody production was demonstrated in a mouse model of PV, but whether these cells exert cytotoxicity in the tissues is unclear. Here, we analyzed 3 Dsg3-specific TCRs using transgenic mice and retrovirus induction. Dsg3-specific transgenic (Dsg3H1) T cells underwent deletion in the presence of Dsg3 in vivo. Dsg3H1 T cells that developed in the absence of Dsg3 elicited a severe pemphigus-like phenotype when cotransferred into immunodeficient mice with B cells from Dsg3-/- mice. Strikingly, in addition to humoral responses, T cell infiltration of Dsg3-expressing tissues led to interface dermatitis, a distinct form of T cell-mediated autoimmunity that causes keratinocyte apoptosis and is seen in various inflammatory/autoimmune skin diseases, including paraneoplastic pemphigus. The use of retrovirally generated Dsg3-specific T cells revealed that interface dermatitis occurred in an IFN-γ- and TCR avidity-dependent manner. This model of autoimmunity demonstrates that T cells specific for a physiological skin-associated autoantigen are capable of inducing interface dermatitis and should provide a valuable tool for further exploring the immunopathophysiology of T cell-mediated skin diseases.

Characterization of full-length and proteolytic cleavage fragments of desmoglein-2 in native human colon and colonic epithelial cell lines

The desmosomal cadherin desmoglein-2 (Dsg2) is a transmembrane cell adhesion protein that is widely expressed in epithelial and non-epithelial tissues, such as the intestine, epidermis, testis, and heart. Dsg2 has been shown to regulate numerous cellular processes, including proliferation and apoptosis, and we have previously reported that intracellular fragments of Dsg2 promote apoptosis in colonic epithelial cells. While several studies have shown that both the extracellular and intracellular domains of Dsg2 can be targeted by proteases, identification of these putative Dsg2 fragments in colonic epithelial cells has not been performed. Here, we report that the mouse monoclonal antibody (mAb) AH12.2 binds to the first extracellular domain of Dsg2. Using this antibody along with previously described mAb against the extracellular (6D8) and intracellular (DG3.10) domains of Dsg2, we characterize the expression and identify the cleavage fragments of Dsg2 in colonic epithelial cells. This study provides a detailed description of the extracellular and intracellular Dsg2 cleavage fragments that are generated in the simple epithelium of the colon and will guide future studies examining the relationship of these fragments to cellular fate and disease states.

From pemphix to desmogleins

In the not so distant past, the word pemphigus or pemphix was common for describing various diseases characterized by blistering as well as various disorders that do not originate from a blistering pathology. Patients with these conditions were grouped in "other" skin diseases. Step by step, during the past, we were introduced to these severe conditions. First, we learned from sporadic case reports, then new differentiations were reported according to histology, later immunopathology was developed, and now there are discoveries of new molecules. Immense progress with new approaches to therapy has been achieved, but much improvement is still needed. The modern definition of pemphigus undoubtedly represents a group of rare, intraepidermal autoimmune bullous diseases characterized by intraepidermal blisters and circulating autoantibodies desmogleins against the keratinocytes cell surface.

Desquamative gingivitis as a manifestation of chronic mucocutaneous disease

Desquamative gingivitis (DG) is a clinical descriptive term indicating "peeling gums". DG is usually the result of a disease process that causes separation of the epithelium from the underlying connective tissue in the oral masticatory mucosa. DG may be a manifestation of several mucocutaneous diseases, most commonly cicatricial pemphigoid, pemphigus vulgaris and lichen planus. Correct diagnosis of the underlying disease in DG patients requires careful clinical observation, detailed examination of medical history, biopsy and histopathological examination of the lesions as well as more specialized tests such as direct and indirect immunofluorescence. Treatment of DG consists of treating the underlying disease and often requires the use of immunosuppressive agents, such as corticosteroids. Elimination of local gingival irritants, such as dental plaque and calculus, can significantly improve the treatment outcome.