Chronic exposure to the anti-M3 muscarinic acetylcholine receptor autoantibody in pemphigus vulgaris contributes to disease pathophysiology.

Pemphigus vulgaris (PV) is a potentially lethal autoimmune mucocutaneous blistering disease characterized by binding of IgG autoantibodies (AuAbs) to keratinocytes (KCs). In addition to AuAbs against adhesion molecules desmogleins 1 and 3, PV patients also produce an AuAb against the M3 muscarinic acetylcholine (ACh) receptor (M3AR) that plays an important role in regulation of vital functions of KCs upon binding endogenous ACh. This anti-M3AR AuAb is pathogenic because its adsorption eliminates the acantholytic activity of PV IgG; however, the molecular mechanism of its action is unclear. In the present study, we sought to elucidate the mode of immunopharmacologic action of the anti-M3AR AuAb in PV. Short-term exposures of cultured KCs to PV IgG or the muscarinic agonist muscarine both induced changes in the expression of keratins 5 and 10, consistent with the inhibition of proliferation and upregulated differentiation and in keeping with the biological function of M3AR. In contrast, long-term incubations induced a keratin expression pattern consistent with upregulated proliferation and decreased differentiation, in keeping with the hyperproliferative state of KCs in PV. This change could result from desensitization of the M3AR, representing the net antagonist-like effect of the AuAb. Therefore, chronic exposure of KCs to the anti-M3AR AuAb interrupts the physiological regulation of KCs by endogenous ACh, contributing to the onset of acantholysis. Since cholinergic agents have already demonstrated antiacantholytic activity in a mouse model of PV and in PV patients, our results have translational significance and can guide future development of therapies for PV patients employing cholinergic drugs.

What protein kinases are crucial for acantholysis and blister formation in pemphigus vulgaris? A systematic review.

Pemphigus vulgaris (PV) is a potentially fatal autoimmune blistering disease characterized by cell-cell detachment (or acantholysis) and blister formation. While the signaling mechanisms that associate with skin/mucosal blistering are being elucidated, specific treatment strategies targeting PV-specific pathomechanisms, particularly kinase signaling, have yet to be established. Hence, the aim of this review was to systematically evaluate molecules in the class of kinases that are essential for acantholysis and blister formation and are therefore candidates for targeted therapy. English articles from PubMed and Scopus databases were searched, and included in vitro, in vivo, and human studies that investigated the role of kinases in PV. We selected studies, extracted data and assessed risk of bias in duplicates and the results were reported according to the methodology outlined by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). The risk of bias assessment was performed on in vivo studies utilizing SYRCLE's risk of bias tool. Thirty-five studies were included that satisfied the pathogenicity criterion of kinases in PV, the vast majority being experimental models that used PV sera (n = 13) and PV-IgG (n = 22). Inhibition of kinase activity (p38MAPK, PKC, TK, c-Src, EGFR, ERK, mTOR, BTK, and CDK2) was achieved mostly by pharmacological means. Overall, we found substantial evidence that kinase inhibition reduced PV-associated phosphorylation events and keratinocyte disassociation, prevented acantholysis, and blocked blister formation. However, the scarce adherence to standardized reporting systems and the experimental protocols/models used did limit the internal and external validity of these studies. In summary, this systematic review highlighted the pathogenic intracellular events mediated by kinases in PV acantholysis and presented kinase signaling as a promising avenue for translational research. In particular, the molecules identified and discussed in this study represent potential candidates for the development of mechanism-based interventions in PV.

Mechanism-based therapeutic targets of pemphigus vulgaris: A scoping review of pathogenic molecular pathways.

Pemphigus vulgaris (PV) is a potentially fatal autoimmune blistering disease characterised by cell-cell detachment or acantholysis. The mechanisms which follow antibody (Ab) binding and culminate in acantholytic changes and skin/mucosal blistering have not been fully clarified. Current treatment strategies are not specific to PV pathophysiology and although life-saving, harbour considerable side effects. We aimed to systematically assess the molecules amenable to targeted treatments that follow Ab binding and are associated with PV acantholysis. The resulting scoping review was conducted under PRISMA-ScR guidelines with clear inclusion and exclusion criteria and focused specifically on kinases, caspases, proteases, hydrolytic enzymes and other molecules of interest postulated to take part in the pathophysiology of PV. The review process resulted in the identification of 882 articles, of which 56 were eligible for qualitative synthesis. From the included articles, the majority (n = 42) used PV-IgG as the pathogenic agent, mainly via in vitro (n = 16) and in vivo (n = 10) models. Twenty-five molecules were found to play a pathogenic role in PV, including uPA, ADAM10, EGFR, Src, PKC, cdk2, ERK, PLC, calmodulin, NOS, p38MAPK and caspase-3. Selective inhibition of these molecules resulted in varying degrees of reduction in acantholysis and blistering. The pathogenic molecules identified in this review represent potential candidates for clinical translation.

Regional Differences in the Permeability Barrier of the Skin-Implications in Acantholytic Skin Diseases.

The chemical milieu, microbiota composition, and immune activity show prominent differences in distinct healthy skin areas. The objective of the current study was to compare the major permeability barrier components (stratum corneum and tight junction (TJ)), investigate the distribution of (corneo)desmosomes and TJs, and measure barrier function in healthy sebaceous gland-rich (SGR), apocrine gland-rich (AGR), and gland-poor (GP) skin regions. Molecules involved in cornified envelope (CE) formation, desquamation, and (corneo)desmosome and TJ organization were investigated at the mRNA and protein levels using qRT-PCR and immunohistochemistry. The distribution of junction structures was visualized using confocal microscopy. Transepidermal water loss (TEWL) functional measurements were also performed. CE intracellular structural components were similarly expressed in gland-rich (SGR and AGR) and GP areas. In contrast, significantly lower extracellular protein levels of (corneo)desmosomes (DSG1 and CDSN) and TJs (OCLN and CLDN1) were detected in SGR/AGR areas compared to GP areas. In parallel, kallikrein proteases were significantly higher in gland-rich regions. Moreover, gland-rich areas were characterized by prominently disorganized junction structures ((corneo)desmosomes and TJs) and significantly higher TEWL levels compared to GP skin, which exhibited a regular distribution of junction structures. According to our findings, the permeability barrier of our skin is not uniform. Gland-rich areas are characterized by weaker permeability barrier features compared with GP regions. These findings have important clinical relevance and may explain the preferred localization of acantholytic skin diseases on gland-rich skin regions (e.g., Pemphigus foliaceus, Darier's disease, and Hailey-Hailey disease).

Acantholytic dyskeratosis of the vulva presenting with clinical features of vulval lichen sclerosus-A possible rare collision entity.

We present a challenging case of chronic, erosive, scarring dermatosis of the vulva with clinical features of long standing lichen sclerosus (LS), namely pallor and loss of vulval architecture, but with histopathology consistently showing features of an acantholytic process. The history and clinical features of this case do not resemble other acantholytic conditions such as pemphigus vulgaris, Hailey-Hailey disease, Darier disease, or the entities described as acantholytic dermatoses affecting the vulva. As far as we are aware, the combination of the clinical features and histopathologic findings in our case do not fit with any previously described condition and we propose that this is a rare entity of a collision of LS and an erosive acantholytic process occurring together.

Distinguishing histopathologic features of acantholytic dermatoses and the pattern of acantholytic hypergranulosis.

BACKGROUND: Acantholysis can be seen in multiple skin diseases. Adnexal acantholysis has been regarded as a feature distinguishing pemphigus vulgaris (PV) from acantholytic conditions. METHODS: A retrospective review of the histopathologic features of diseases with acantholysis including PV, pemphigus foliaceus (PF), Hailey-Hailey disease (HHD), Darier disease (DD), Grover disease, and pityriasis rubra pilaris (PRP) was performed. RESULTS: Biopsies of PV (n = 49), HHD (n = 27), DD (n = 25), Grover disease (n = 65), and PRP (n = 33) showed suprabasilar acantholysis. Acantholysis was limited to the lower epidermis in PV and PRP, and involved all epidermal layers in HHD, DD, and Grover disease. Acantholysis in PF (n = 38) mainly involved the upper epidermis. Follicular acantholysis occurred more frequently in PV and PF (P < 0.0001). Eccrine acantholysis was found in PV (42%), HHD (18%), PF (13%), and DD (4%). Grover disease, DD, and HHD had greater dyskeratosis (P < 0.0001). Neutrophils were more common in PV, PF, and HHD, while eosinophils were more common in Grover disease and DD. A pattern termed acantholytic hypergranulosis occurred predominantly in PF. CONCLUSION: Adnexal acantholysis does not reliably distinguish PV from PF. The level of acantholysis, degree of dyskeratosis, and acantholytic hypergranulosis are distinguishing features between the two types of pemphigus and other acantholytic disorders.

Pseudoherpetic transient acantholytic dermatosis (Grover disease): case series and review of the literature.

A total of 3 cases of pseudoherpetic transient acantholytic dermatosis (Grover disease) are presented, followed by a brief review of prior reports. All 3 patients were above the age of 60 and presented with a pruritic eruption composed of papules with or without vesicles distributed on the trunk. For all 3 patients, the clinical differential diagnosis included drug eruption but did not include Grover disease; in 1 patient, the clinical impression included herpesvirus infection. Similar histologic and immunohistochemical findings were demonstrated in all 3 cases. Intraepidermal vesicles with acantholysis, multinucleation and hypereosinophilic keratinocytes mimicking necrosis raised the possibility of herpesvirus infection. However, the focality of the process at scanning magnification, absence of true cytopathic effect despite multinucleation, and identification of dyskeratosis rather than true necrosis all permitted for morphologic distinction as pseudoherpetic change. Immunohistochemistry, negative for herpes simplex virus and varicella zoster virus antigens, also distinguished pseudoherpetic change in these patients from a true herpesvirus infection. This series highlights an uncommon histologic variant of a common disorder and describes morphologic and immunohistochemical findings to facilitate its distinction from true herpesvirus infection.

PD-1 inhibitor-associated lichenoid inflammation with incidental suprabasilar acantholysis or vesiculation-Report of 4 cases.

BACKGROUND: Immune checkpoint agents targeting programmed cell death-1 protein (PD1) or cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) receptors are increasingly utilized in treatment of advanced malignancies. However, these immunotherapies are commonly associated with idiosyncratic cutaneous adverse reactions. Thus, recognition and awareness of these reactions are necessary. METHODS: We reviewed the skin biopsies of all patients on anti-PD1 therapy with or without ipilimumab who developed lichenoid inflammation and included those with microscopic suprabasal or intraepidermal clefts. RESULTS: Four patients presented with interface dermatitis with microscopic intraepidermal clefts. In 2 patients, the clefts were well developed and had some acantholytic cells while the other 2 appeared to be spongiosis or inflammation related. Immunofluorescence was negative in 1 patient. None of them had clinical findings in keeping with paraneoplastic pemphigus (PP) and the symptoms improved with either topical corticosteroid or withdrawal of immunotherapy. CONCLUSIONS: Lichenoid drug reaction occurring in patients receiving anti-PD1 therapy may be associated with microscopic suprabasal or intraepidermal clefting. The clinical course was similar to lichenoid drug reactions without clefting even though some lesions may resemble PP microscopically.

A pathophysiologic role for epidermal growth factor receptor in pemphigus acantholysis.

The pemphigus family of autoimmune bullous disorders is characterized by autoantibody binding to desmoglein 1 and/or 3 (dsg1/dsg3). In this study we show that EGF receptor (EGFR) is activated following pemphigus vulgaris (PV) IgG treatment of primary human keratinocytes and that EGFR activation is downstream of p38 mitogen-activated protein kinase (p38). Inhibition of EGFR blocked PV IgG-triggered dsg3 endocytosis, keratin intermediate filament retraction, and loss of cell-cell adhesion in vitro. Significantly, inhibiting EGFR prevented PV IgG-induced blister formation in the passive transfer mouse model of pemphigus. These data demonstrate cross-talk between dsg3 and EGFR, that this cross-talk is regulated by p38, and that EGFR is a potential therapeutic target for pemphigus. Small-molecule inhibitors and monoclonal antibodies directed against EGFR are currently used to treat several types of solid tumors. This study provides the experimental rationale for investigating the use of EGFR inhibitors in pemphigus.

Transcriptional profiling of rare acantholytic disorders suggests common mechanisms of pathogenesis.

Darier, Hailey-Hailey, and Grover diseases are rare acantholytic skin diseases. While these diseases have different underlying causes, they share defects in cell-cell adhesion in the epidermis and desmosome organization. To better understand the underlying mechanisms leading to disease in these conditions, we performed RNA-seq on lesional skin samples from patients. The transcriptomic profiles of Darier, Hailey-Hailey, and Grover diseases were found to share a remarkable overlap, which did not extend to other common inflammatory skin diseases. Analysis of enriched pathways showed a shared increase in keratinocyte differentiation, and a decrease in cell adhesion and actin organization pathways in Darier, Hailey-Hailey, and Grover diseases. Direct comparison to atopic dermatitis and psoriasis showed that the downregulation in actin organization pathways was a unique feature in the acantholytic skin diseases. Furthermore, upstream regulator analysis suggested that a decrease in SRF/MRTF activity was responsible for the downregulation of actin organization pathways. Staining for MRTFA in lesional skin samples showed a decrease in nuclear MRTFA in patient skin compared with normal skin. These findings highlight the significant level of similarity in the transcriptome of Darier, Hailey-Hailey, and Grover diseases, and identify decreases in actin organization pathways as a unique signature present in these conditions.

Innate immune activation as cofactor in pemphigus disease manifestation.

Molecular mechanisms underlying auto-antibody-induced acantholysis in pemphigus vulgaris are subject of current research to date. To decipher the discrepancy between ubiquitous antibody binding to the epidermal desmosomes, but discontinuous disease manifestation, we were able to identify Ultraviolet A (UVA) as a cofactor for acantholysis. UVA induces interleukin (IL)-1 secretion in keratinocytes, mirroring innate immune system activation. In an in vitro keratinocyte dissociation assay increased fragmentation was observed when UVA was added to anti-Desmoglein 3 Immunoglobulins (anti-Dsg3 IgG). These results were confirmed in skin explants where UVA enhanced anti-Dsg3-mediated loss of epidermal adhesion. The UVA-mediated effect was blocked in vitro by the pan-caspase-inhibitor zVAD-fmk. Thus, we introduce UVA as a caspase-dependent exogenous cofactor for acantholysis which suggests that local innate immune responses largely contribute to overt clinical blister formation upon autoantibody binding to epidermal cells in pemphigus vulgaris.

Low SOCS3 expression in CD4+ T cells from pemphigus vulgaris patients enhanced Th1- and Th17-cell differentiation and exacerbated acantholysis via STAT activation.

OBJECTIVE: Pemphigus vulgaris (PV) is a chronic inflammatory autoimmune blistering disease. Aberrant SOCS3/STAT pathway activation is associated with many autoimmune diseases. This study explored the relationship between activation of the SOCS3/STAT pathway and abnormally increased proportions of Th1 and Th17 cells in the peripheral blood of PV patients as well as the effect of CD4+ T cells with abnormal SOCS3/STAT pathway activation on acantholysis. METHODS: In PV patients, the proportions of Th1 and Th17 cells in peripheral blood, the levels of IFN-γ and IL-17 in serum and the mRNA levels of SOCS3 and STAT1/3 in CD4+ T cells were detected. Then, SOCS3-knockdown primary CD4+ T cells were prepared, and cocultured with HaCaT cells. Finally, after SOCS3 knockdown and coculture, CD4+ T cells were collected, and the proportions of Th1 and Th17 cells, the protein levels of STAT1/3 and p-STAT1/3, and the levels of IFN-γ and IL-17 were measured. After 2 days of coculture, HaCaT cells were collected, inflammatory factors mRNA expression and acantholysis were assessed. RESULTS: In PV patients, the proportions of Th1 (P = 0.016) and Th17 (P = 0.045) cells and the levels of IFN-γ (P = 0.010) were significantly increased. SOCS3 mRNA in CD4+ T cells was significantly decreased (P = 0.008), whereas STAT1 (P = 0.043) and STAT3 (P = 0.004) mRNA were significantly increased. After SOCS3 knockdown, the proportions of Th1 (P < 0.001) and Th17 (P = 0.006) cells, the levels of IFN-γ (P < 0.001) and IL-17 (P = 0.001), and the protein levels of p-STAT1 (P = 0.001) and p-STAT3 (P = 0.003) were significantly increased in the CD4+ T-shSOCS3-1 group. In the coculture system, the proportions of Th1 (P < 0.001) and Th17 (P < 0.001) cells, the levels of IFN-γ (P < 0.001) and IL-17 (P < 0.001), and the number of cell fragments (P < 0.001) were significantly increased in the CD4+ T-shSOCS3-1+HaCaT-PV-IgG group, whereas the protein level of desmoglein3 (Dsg3) was significantly decreased. In addition, PV-IgG significantly increased IFN-γ and IL-6 mRNA in HaCaT cells. CONCLUSION: Low SOCS3 expression in CD4+ T cells from PV patients leads to overactivation of STAT, which causes CD4+ T cells to overdifferentiate into Th1 and Th17 cells. Additionally, PV-IgG-induced local inflammation in skin lesions, which is mediated by IFN-γ and IL-6, can aggravate this phenomenon. Furthermore, low SOCS3 expression in CD4+ T cells further exacerbates PV-IgG-induced acantholysis. Therefore, upregulating the expression of SOCS3 in CD4+ T cells of PV patients and maintaining the balance of the IFN-γ/STAT1/SOCS3 and IL-6/STAT3/SOCS3 pathways can alleviate acantholysis in patients with PV.

Mechanisms Causing Acantholysis in Pemphigus-Lessons from Human Skin.

Pemphigus vulgaris (PV) is an autoimmune bullous skin disease caused primarily by autoantibodies (PV-IgG) against the desmosomal adhesion proteins desmoglein (Dsg)1 and Dsg3. PV patient lesions are characterized by flaccid blisters and ultrastructurally by defined hallmarks including a reduction in desmosome number and size, formation of split desmosomes, as well as uncoupling of keratin filaments from desmosomes. The pathophysiology underlying the disease is known to involve several intracellular signaling pathways downstream of PV-IgG binding. Here, we summarize our studies in which we used transmission electron microscopy to characterize the roles of signaling pathways in the pathogenic effects of PV-IgG on desmosome ultrastructure in a human ex vivo skin model. Blister scores revealed inhibition of p38MAPK, ERK and PLC/Ca2+ to be protective in human epidermis. In contrast, inhibition of Src and PKC, which were shown to be protective in cell cultures and murine models, was not effective for human skin explants. The ultrastructural analysis revealed that for preventing skin blistering at least desmosome number (as modulated by ERK) or keratin filament insertion (as modulated by PLC/Ca2+) need to be ameliorated. Other pathways such as p38MAPK regulate desmosome number, size, and keratin insertion indicating that they control desmosome assembly and disassembly on different levels. Taken together, studies in human skin delineate target mechanisms for the treatment of pemphigus patients. In addition, ultrastructural analysis supports defining the specific role of a given signaling molecule in desmosome turnover at ultrastructural level.

Desmosomes and disease: pemphigus and bullous impetigo.

Desmosomal cadherins are the pathophysiologic targets of autoimmune or toxin-mediated disruption in the human diseases pemphigus and bullous impetigo (including its generalized form, called staphylococcal scalded skin syndrome). Experiments exploiting the production of both pathogenic and nonpathogenic antidesmoglein antibodies in pemphigus patients' sera have afforded data that make an invaluable contribution towards identifying the functional domains of the desmogleins involved in intercellular adhesion. Conformational epitopes of antidesmoglein autoantibodies in pemphigus patients' sera and the specific cleavage site of desmoglein 1 by exfoliative toxin have been identified, implicating the N-terminal extracellular domains of the desmogleins as critical regions for controlling intercellular adhesion. Furthermore, the development of active autoimmune mouse models for pemphigus allows in vivo characterization of the disease and its pathogenesis. These studies offer new insight into the potential mechanisms of acantholysis in pemphigus and staphylococcal-associated blistering disease, with implications for the role of desmogleins in desmosomal structure and function.

IgG-induced clustering of desmogleins 1 and 3 in skin of patients with pemphigus fits with the desmoglein nonassembly depletion hypothesis.

BACKGROUND: In pemphigus circulating IgG is present with the desmosomal cadherins desmoglein (Dsg) 1 and 3. In the epidermis of patients, this IgG deposits in a pattern that is often partly granular and does not reflect the normal Dsg distribution. OBJECTIVE: To understand why the IgG deposits in a granular pattern in the skin of patients with pemphigus. PATIENTS/METHODS: We analysed the distribution of IgG and desmosomal adhesion molecules in skin biopsies of 18 patients with pemphigus vulgaris (PV) and 10 with pemphigus foliaceus (PF) by double staining immunofluorescence. The effect of IgG on desmosomal proteins was studied in an in vitro skin model. RESULTS: In PF skin Dsg1, but not Dsg3, was aberrantly distributed in the same partly granular pattern as the IgG. Vice versa, in skin of PV patients with anti-Dsg3 antibodies, Dsg3, but not Dsg1, colocalized with the granular IgG. Plakoglobin also coclustered with IgG and Dsg, but this was far more prominent with Dsg1 than with Dsg3. In areas of heavy Dsg1 clustering, but not in areas of heavy Dsg3 clustering, intercellular widening between keratinocytes was present. Patient IgG, but not Fab fragments, induced the same Dsg clustering in vitro. CONCLUSIONS: The IgG-induced clustering of the Dsg autoantigens underlies the granular IgG deposition in patient skin. In PF and in mucocutaneous PV, Dsg1 clustering, but not Dsg3 clustering, correlates with nonacantholytic intercellular widening between desmosomes. In the patient the Dsg becomes sequestered from desmosomal components which fits in with the desmoglein nonassembly depletion hypothesis, indicating that targeted nonjunctional Dsg is no longer available to be incorporated into desmosomes and this leads to disturbed assembly, and Dsg-depleted desmosomes.

Acantholytic anaplastic Paget's disease.

Classic Paget's disease (PD) can be diagnosed relatively easily by histopathologic examination. 'Anaplastic' variant of this disease is a less-recognized subset that may pose as a diagnostic challenge and pitfall. We describe two cases who presented with scaly erythematous plaques on their nipple/areola. In the first patient, there was no palpable mass and imaging studies were negative. The second case presented with a lesion 5 years after a lumpectomy. Initial shave biopsies revealed histopathologic changes indistinguishable from Bowen's disease with no readily identifiable classic Paget's cells, associated with prominent superficial acantholysis. The neoplastic cells were negative for mucin, GCDFP-15, negative/minimally positive for CEA and strongly positive for CK7 markers. A high-grade ductal carcinoma in situ in the underlying breast was ultimately found in both cases. Anaplastic PD is a rare variant of this disease that histologically mimics Bowen's disease with an associated prominent superficial acantholysis. There is mucin, CEA and GCDFP-15 negativity with positive CK7 reaction. A high index of suspicion along with a complete immunohistochemical panel should be considered in evaluating any Bowenoid neoplasm of the breast skin, particularly in superficial skin shave biopsies along with negative imaging studies and no palpable mass clinically.

Oral variant of acantholytic squamous cell carcinoma-Histochemical and immunohistochemical features.

Acantholytic squamous cell carcinoma (ASCC) is an uncommon variant of squamous cell carcinoma (SCC). It is characterized by a combination of typical SCC and pseudoglandular structures, dyskeratotic cells and prominent acantholysis. The purpose of this study was to analyze the histochemical and immunohistochemical characteristics of the intraoral variant of ASCC. Cases of intraoral ASCC were retrieved from the English language literature. Four new cases from our files were added. In total, 35 cases were included and analyzed in this study. The mean age of the patients was 61.5 + 13 years (age range 38-92 years), with a male-to-female ratio of 1.7:1. According to the available data, histochemical and immunohistochemical stains for mucins were found to be consistently negative. E- cadherin, a marker of adherens junctions, was usually reported to be expressed in areas of "typical" (non acantholytic) SCC, but reduced in the acantholytic areas. We examined for the first time the expression of claudin 1, a marker of tight junctions, and found it to be reduced in the acantholytic areas, similar to E-cadherin. Several cases of oral ASCC also expressed vimentin and cytokeratin (CK) 19, markers associated with epithelial-mesenchymal transition. A wide range of non-epithelial markers yielded negative immunoreactions. In conclusion, ASCC is an uncommon variant of squamous cell carcinoma. The acantholytic process appears to involve reduced expression of molecular components of both adherens junctions and tight junctions. These findings could suggest a relation to the epithelial mesenchymal transition process and therefore further studies are needed in order to establish such a link and the subsequent possible impact on the clinical outcome of the patients.

Pemphigus: a complex T cell-dependent autoimmune disorder leading to acantholysis.

Pemphigus is a relatively rare autoimmune bullous disorder involving the skin and mucous epithelia. Clinically characterized by blisters and erosions, its histological hallmark is acantholysis induced by IgG antibodies (ab) against desmoglein 3 and/or desmoglein 1. The role of ab alone in inducing acantholysis is still a matter of debate as several mechanisms could be involved. Another intriguing area of research is the trigger factor inducing autoimmunity in pemphigus patients and the role of T and B cells in this process. This paper will review the data related to the mechanisms of acantholysis between keratinocytes and the role of T cell in this phenomenon.

Immunohistological study of involucrin expression in Darier's disease skin.

BACKGROUND: Darier's disease (DD) is an autosomal dominant skin disorder characterized by acantholysis and abnormal keratinization. The gene responsible for DD, ATP2A2 encodes for the sarco/endoplasmic reticulum (ER) Ca2+-ATPase isoform 2 protein. Involucrin, considered as a marker of terminal epidermal differentiation, could be altered in some keratinization disorders including DD. PATIENTS AND METHODS: An immunohistochemical staining using anti-involucrin antibody was carried out on 16 DD patients epidermis. Involucrin staining was compared with biopsies from cutaneous lesions of three healthy individuals and of patients with Hailey-Hailey disease (five cases) and Mal de Meleda (four cases). A semi-quantitative analysis was performed in order to evaluate involucrin immunostaining on the basis of intensity, extension and epidermal distribution. The involucrin expression was examined afterward with confocal laser scanning microscopy. RESULTS: In contrast to normal skin, all DD cases showed premature expression of involucrin in the lower epidermal layers in four cases with a strong labeling in both keratinocytes cell membrane and cytoplasm. Other keratinization disorders share premature expression of involucrin but displayed differences in cytoplasm/cell membrane labeling. CONCLUSIONS: DD skin displayed a constant immunohistochemical involucrin pattern characterized by both premature expression and a particular cytoplasmic/cell membrane localization distribution.