Specificity and inhibition of the epidermal cell detachment induced by pemphigus IgG in vitro

The human skin organ culture model as an optimal complementary tool for murine pemphigus models

Pemphigus is a severe autoimmune bullous disease of the skin and/or mucous membranes caused by autoantibodies that mainly target the adhesion proteins desmoglein (Dsg) 3 and/or Dsg1. Clinically, pemphigus is characterized by flaccid blistering, leading to severe water and electrolyte loss. Before the introduction of corticosteroid treatment, the disease turned out to be fatal in many cases. Despite recent therapeutic improvements, treatment of pemphigus patients is centred on prolonged systemic immunosuppression and remains challenging. Current drug development for pemphigus has a strong focus on disease-causing B cells and autoantibodies and, more recently, also on modulating autoantibody-induced tissue pathology and keratinocyte signalling. This drug development requires reliable pre-clinical model systems replicating the pathogenesis of the human disease. Among those are neonatal and adult mouse models based on the transfer of Dsg3, Dsg1/3 or Dsg1-specific autoantibodies. To reduce the number of animal experiments, we recently established a standardized human skin organ culture (HSOC) model for pemphigus. This model reproduces the clinical phenotype of autoantibody-induced tissue pathology in pemphigus vulgaris. For induction of blistering, a recombinant single-chain variable fragment (scFv) targeting both Dsg1 and 3 is injected into pieces of human skin (obtained from plastic surgeries). Further characterization of the HSOC model demonstrated that key morphologic, molecular and immunologic features of pemphigus are being replicated. Thus, the pemphigus HSOC model is an excellent alternative to pemphigus animal model systems that are based on the transfer of (auto)antibodies.

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.

Pemphigus in the XXI Century: New life to an old story

In this new century of pemphigus research, the search for novel treatments is switching from a monospecific approach, focused on immunosuppression, to a polyspecific approach that includes drugs acting on novel pathophysiologic pathways. Current research argues that acantholysis in pemphigus occurs as an active process resulting from intracellular signaling triggered as a result of IgG binding to the keratinocyte membrane antigens in a receptor-ligand fashion. Recent progress regarding the pathophysiology of pemphigus acantholysis led to, or was accompanied by, breakthrough discoveries of safer treatments. Both the identification of cell-surface receptors to acetylcholine among the nondesmoglein (Dsg) targets for pemphigus antibodies, and the elucidation of the cholinergic control of keratinocyte cell adhesion provide an explanation for the therapeutic efficacy of cholinomimetics in patients with pemphigus. In patients' skin, Fas-L, TNFalpha, and, probably, IL-1alpha act as autocrine/paracrine co-factors for anti-keratinocyte IgG. Thus, it appears that an array of interconnected signaling cascades is responsible for acantholysis and cell death in pemphigus. Future studies should define the signaling pathways mediating acantholysis that occur in individual pemphigus patients and identify the membrane proteins (receptors) triggering signaling along a specific pathway upon their ligation by autoantibodies. It will be important to determine which pathway 1) leads directly to a loss of cell-cell adhesion (primary pathway), 2) which is being activated due to cell shrinkage/detachment (secondary pathway), 3) which contributes to utilization of altered proteins and organelles (scavenging pathway), and 4) which represents the cell defense (protective pathway). To dissect out the signaling pathways originating from binding of pemphigus IgG to non-Dsg targets on the keratinocyte plasma membrane experiments should be performed in cultures of murine keratinocytes grown from the Dsg3-/- mice or human keratinocytes with the knocked-down expression of the Dsg1 and/or Dsg3 gene by the RNA interference.

Pemphigus antibody induced phosphorylation of keratinocyte proteins

The pemphigus family of autoimmune blistering diseases is characterized by an autoantibody response to desmosomal cadherins in epithelia. Autoantibodies against desmogleins, desmosome cell adhesion molecules, induce loss of cell-cell adhesion that is characterized clinically by blister formation. The mechanism by which these autoantibodies induce loss of cell-cell adhesion is under active investigation, but appears to involve a coordinated intracellular response including activation of intracellular signaling and phosphorylation of a number of proteins in the target keratinocyte. Activation of p38 mitogen activated protein kinase may have a critical role in the acantholytic mechanism as inhibitors of p38MAPK block the ability of pemphigus IgG to induce blistering in pemphigus animal models.

In vitro and in vivo expression of interleukin-1alpha and tumor necrosis factor-alpha mRNA in pemphigus vulgaris: interleukin-1alpha and tumor necrosis factor-alpha are involved in acantholysis

Keratinocyte-derived cytokines have been implicated in the pathogenesis of a number of skin diseases. In this study we examined the possible role of keratinocyte-derived cytokines in the development of acantholysis in pemphigus vulgaris. Nineteen patients with pemphigus vulgaris, demonstrating the characteristic clinical, pathologic, and immunopathologic findings were studied. In situ immunolabeling demonstrated the presence of two cytokines interleukin-1alpha and tumor necrosis factor-alpha, in lesional and perilesional areas. Results were confirmed by reverse transcriptase-polymerase chain reaction, demonstrating overexpression of both cytokines in vivo. To study the role of these cytokines in the pathogenesis of pemphigus vulgaris both in vitro and in vivo studies were performed. The results of the in vitro study demonstrated that pemphigus vulgaris IgG induced interleukin-1alpha and tumor necrosis factor-alpha mRNA in the skin. The potential pathogenic role of these mediators was demonstrated by a blocking study using antibodies against human interleukin-1alpha and tumor necrosis factor-alpha in keratinocytes cultures. A combination of anti-interleukin-1alpha and anti-tumor necrosis factor-alpha antibodies inhibited in vitro pemphigus vulgaris IgG induced acantholysis. To confirm the role of interleukin-1 and tumor necrosis factor-alpha in pemphigus, we utilized passive transfer studies using interleukin-1 deficient mice (ICE-/-, interleukin-1beta-/-) and tumor necrosis factor-alpha receptor deficient mice (TNFR1R2-/-). Both groups demonstrated a decreased susceptibility to the passive transfer of pemphigus. Our data support the role of cytokines interleukin-1 and tumor necrosis factor-alpha in the pathogenesis of pemphigus vulgaris.

Proteinase inhibitors and pemphigus vulgaris. An in vitro and in vivo study

The aim of this study was to determine the inhibitory effect of clinically usable proteinase inhibitors p-aminomethylbenzoic acid (PAMBA), and aprotinin on acantholysis in skin organ culture and in clinical trials with pemphigus patients. PAMBA added to the culture medium at a concentration of 1 mg/ml fully prevented the acantholysis, while Contrykal at 10 ATrE/ml reduced acantholysis. Subsequently, we treated 12 patients (groups 1) with PAMBA 100-200 mg daily for 7 to 26 days in combination with a moderate dose of corticosteroid (mean dose 36.1 mg prednisolone equivalent) or immunosuppressive drugs. A second group of 12 patients (group 2) were treated with a high dose of corticosteroid (mean 94.2 mg prednisolone equivalent) and immunosuppressive drugs. Evaluation was performed before treatment, after 3 weeks and on discharge using a clinical scoring system. The inclusion of PAMBA in the treatment protocol of group 1 resulted in active disease being brought under control with lower corticosteroid doses. As a result, fewer side effects were observed in group 1 than in group 2. In our opinion, protease inhibitors may be useful as adjuvant drugs in the combination therapy of pemphigus.

IgG subclasses in pemphigus in Indian and UK populations

The autoimmune blistering disease pemphigus is more common in the Indian subcontinent than in the UK. This study of 19 patients from Oxford, UK and 39 patients from New Delhi, India demonstrates that the incidence of the disease subtypes is different in the two countries. In the UK the commonest subtypes are pemphigus vulgaris and foliaceus with equal prevalence (both eight of 19), but in India pemphigus vulgaris is the most frequent (31 of 39), while pemphigus foliaceus is uncommon (three of 39) and with equal prevalence to the other subtypes. These populations also differ with a younger age at onset in the Indian patients (36.9 India; 52.7 UK) though the sex distribution is the same. Study of the immunopathology shows that the antibodies produced by patients in the two countries do not differ significantly, and are predominantly of the IgG4 subclass. The antibody produced does not vary with the subtype of pemphigus or the age or sex of the patient. Although there are considerable differences between the two groups of patients this difference is not reflected by the subclass of auto-antibody response.

Ultrastructural study of clinically uninvolved skin of patients with pemphigus vulgaris

We investigated skin biopsies from pemphigus vulgaris (PV) patients by light, fluorescent and electron microscopy in order to study the ultrastructural appearances of epidermis at the pre-acantholytic stage. The biopsies were obtained from uninvolved forearm skin in 10 patients with PV in the acute stage of the disease, from perilesional skin of the same patients as well as from the forearm skin of 10 healthy subjects. Light microscopy showed no pathological changes in clinically uninvolved skin of pemphigus patients. Direct immunofluorescence confirmed the presence of IgG auto-antibodies fixed in intercellular space of the spinous-cell layer of uninvolved skin. Electron microscopy of the uninvolved skin biopsies revealed the following changes: disintegration of desmosomes of spinous cells with their replacement by finger-shaped protrusions of cytoplasm; clarification of the nuclear matrix; widening of the perinuclear slit; an increased number of secondary lysosomes in cells; oedema and swelling of mitochondria with destruction of their cristae. The cells retained their polygonal shape and the intercellular distance did not increase. We conclude that at the pre-acantholytic stage the breakage and dissolution of desmosomes precedes the increase in the intercellular space.

Deposition of the membrane attack complex of complement in pemphigus vulgaris and pemphigus foliaceus skin

The present study was performed to determine whether complement activation in pemphigus vulgaris (PV) and pemphigus foliaceus (PF) results in the assembly of the terminal complement sequence or membrane attack complex (MAC) in skin lesions. Biopsy specimens of skin lesions from five patients with PV and three patients with PF contained C5, C7, C9, and the MAC related neoantigen (C5b-9 neoantigen) in intercellular substance areas (ICS), as well as IgG and the early complement components Clq, C4, and C3. The presence of these late complement components and the C5b-9 neoantigens in ICS sites of the skin lesions is indicative of complement activation by the pemphigus antibody, with subsequent assembly of the MAC. The binding of IgG and early complement components to ICS was observed in both non-lesional (normal appearing) skin and in skin lesions. However, no MAC could be detected in the normal appearing skin of our pemphigus patients. It was also noted that the MAC could be generated in vitro on cryostat sectioned normal human skin by pemphigus antibody in the presence of complement. Results of these studies suggest that complement activation may be related to membrane damage of epidermal cells in both PV and PF.

The usefulness of immunofluorescent tests in pemphigus patients in clinical remission

Direct and indirect immunofluorescent studies (DIF, IIF) were performed on 24 pemphigus vulgaris patients who were in a state of clinical remission. The tests were repeated after an interval of 6 months. All the patients were on maintenance therapy with oral prednisone. The DIF in eight patients showed negative results among whom seven remained negative. Six patients out of 24 showed weakly positive fluorescence and ten patients showed strong positive fluorescence. The IIF was negative in 17 patients and positive in seven patients who also showed positive DIF. During a follow-up period of 20 months, one of eight patients with negative DIF relapsed compared with two of six patients with weak positive DIF and five of 10 patients with strong DIF. Five patients with strong DIF for IgG also had C3, of whom three relapsed, compared with five of 19 patients who were negative for C3. Four of seven patients with positive IIF relapsed compared with four of 17 with negative IIF. It is suggested that repeated DIF tests in pemphigus patients, who are in clinical remission, may serve as an indicator for the immunological activity and be of help in the management of these cases.

Pemphigus

The term pemphigus refers to a group of autoimmune intraepidermal blistering diseases of the skin and mucous membranes. Several clinical variants of pemphigus are recognized. The major histologic feature of all variants is acantholysis, the disruption of normal cell-to-cell adhesion, which leads to intraepidermal blister formation. Most patients with pemphigus demonstrate IgG autoantibodies directed against an antigen located on the surface of keratinocytes. Although the stimulus for autoantibody production is unknown, several mechanisms have been proposed to explain the pathogenesis of acantholysis. One popular model proposes that pemphigus antibodies induce acantholysis through local stimulation of the plasminogen-plasmin system. Another model proposes that pemphigus antibodies fix complement and thereby alter cell membrane integrity to produce acantholysis. Prior to the availability of corticosteroids, pemphigus vulgaris was commonly fatal. Treatment with glucocorticosteroids has drastically improved the prognosis. Immunosuppressive agents and plasmapheresis have been used successfully in some patients with severe disease.

Cantharide acantholysis: endogenous protease activation leading to desmosomal plaque dissolution

Using a method which allowed us to study the morphological consequences of the expression and the inhibition of proteases in living tissues, we demonstrated that the primary detectable cellular event in cantharide acantholysis is the dissolution of the dense plaque, leading to the detachment of tonofilaments from desmosomes. This process is inhibited by neutral serine protease inhibitors. This suggests that the desmosome-tonofilament complex, more precisely the desmosomal dense plaque, is the primary target of activated proteases during cantharide acantholysis, and can be disrupted by a specific epidermal protease-anti protease system. Cantharide acantholysis may be useful model for studying desmosomal turnover.

Effects of pemphigus antibody on the regeneration of cell-cell contact in keratinocyte cultures grown in low to normal Ca++ concentration

Pemphigus is an autoimmune blistering disease of epidermal cells in which autoantibodies to the surface develop. The present study was performed to determine whether the binding of pemphigus antibodies to the surface of keratinocytes can inhibit the regeneration of cell-cell contact induced by altering from low to normal Ca++ concentration medium. Human keratinocytes (a cell line of squamous cell carcinoma, DJM-1 cell) were grown in low Ca++ medium for 4 days, then the cells were incubated in normal Ca++ medium containing 10% pemphigus (4 patients with pemphigus vulgaris and 4 patients with pemphigus foliaceus) or normal serum (treated at 56 degrees C, for 30 min) for various incubation periods (2, 6, 12, 24 h). The cells were fixed and stained with antikeratin antibody by the indirect immunofluorescence method so that the detachment of cell-cell contact was able to be clearly visualized by observing the cytoskeletal arrays of keratin filaments. The cells grown in normal Ca++ medium showed detachments of cell-cell contact 24-36 h after addition of any one of the pemphigus sera used in this study. The cells grown in low Ca++ medium formed no cell-cell contacts and expressed no pemphigus antigens. However, re-formation of cell-cell contacts and reexpression of the antigens were confirmed by immunofluorescence microscopy 30 min after the addition of Ca++ to the medium. The addition of any pemphigus vulgaris and foliaceus sera with Ca++ did not inhibit the regeneration of cell-cell contact and exerted no effects on the contact during the subsequent 12 h. However, after 24 h, these cells again lost the contact. These results indicate that pemphigus antibody and antigen reaction on the cell surface did not directly inhibit the Ca++-induced re-formation of cell-cell contact.

Human pemphigus autoantibodies are pathogenic to squamous epithelium

In 1957, Witbesky et al. put forward several criteria that ideally should be fulfilled in order to prove the pathogenic role of an autoantibody in a putative autoimmune disease. There can now be very little doubt of the autoimmune nature of this disease and of the primary role of autoantibodies in its pathogenesis. The evidence that supports the concept that pemphigus autoantibodies are of primary pathogenic importance in the disease is as follows: IgG class autoantibodies can be found both circulating in the serum and bound to the epithelial cell surfaces in and around lesions in patients with pemphigus. These autoantibodies, purified from the serum of pemphigus patients, can induce acantholytic lesions typical of pemphigus both in experimental animals (neonatal mice) and in human and murine epidermal cell cultures. These autoantibodies react with a specific antigen of the epidermal cell. This purified antigen has been used to immunize rabbits and the resulting antibodies are capable of inducing pemphigus-like lesions in neonatal mice.

Immunopathologic mechanisms in pemphigus and bullous pemphigoid

Pemphigus and bullous pemphigoid are autoimmune bullous diseases of the skin. Pemphigus, an intraepidermal blistering disease, is characterized by autoantibodies reactive with antigens located in the intercellular spaces or on the surfaces of epidermal cells. These antibodies, which have recently been shown to activate complement, appear to be the cause of the basic pathologic process of pemphigus, acantholysis. The complement system and the plasminogen-plasmin system may be important mediators in the detachment of epidermal cells. Bullous pemphigoid, a subepidermal blistering disease, is characterized by autoantibodies reactive with an antigen located in the lamina lucida region of the basement membrane zone. These autoantibodies, which will avidly fix complement, appear to mediate subepidermal separation by attraction of a variety of inflammatory cells. Anaphylatoxins, released by activation of C4 and C3, or specific IgE antibodies, may activate mast cells with release of ECF-A attracting eosinophils. With activation of C5, C5a is released which could attract polymorphonuclear leukocytes. Antigen-specific lymphocytes, which can also contribute histamine releasing substances, may also be involved. The exact mechanism by which the epidermis separates from the dermis in bullous pemphigoid, however, remains unresolved.

Model for detection of membrane-associated antigens on epithelial cells (HLA-A, -B, -C alloantigens and pemphigus antigens)

Incubation of skin explant culture with HLA-A, -B and -C alloantibodies results in detachment of cells at the periphery of the outgrowth. This detachment can be observed within 1 1/2 h, using the reflection contrast microscope. During the detachment of the epithelial cell, characteristic changes occur, such as disorganization of the filopodia and lifting up of the cell borders from the surface of the Petri dish. The same changes were seen using antibodies against pemphigus antigens.

High doses of antigen-nonspecific IgG do not inhibit pemphigus acantholysis in skin organ cultures

A patient suffering from severe pemphigus vulgaris was treated using large-volume plasma exchange in combination with an immunosuppressive regimen. As some recent reports have shown evidence that polyclonal, polyspecific human IgG in high doses through the i.v. route (IGIV) protect target platelets in idiopathic thrombocytopenic purpura from attack by antiplatelet autoantibodies and/or immune complexes, we also administered IGIV to this pemphigus-vulgaris patient. In order to test the hypothesis that IGIV might protect in vitro-cultured human skin from acantholysis induced by pemphigus antibodies, studies with skin organ cultures were carried out using plasma from another pemphigus-vulgaris patient who had undergone plasma exchange. The preincubation of either the skin explants or the pemphigus plasma with various concentrations of IGIV (ranging from 0.15 to 15 mg/ml in the culture medium) did not prevent acantholysis induced by the pemphigus plasma nor did it inhibit the binding of the specific antibodies visualized by direct immunofluorescence. Thus, the assumption that IGIV may coat the pemphigus antigens on epidermal cells making them inaccessible to pathogenic autoantibodies was not substantiated by our tests in vitro; likewise, the hypothesis of functionally blocking autoantibody activity by means of anti-idiotype effects of IGIV cannot be supported.

Experimentally induced pemphigus vulgaris in neonatal BALB/c mice: a time-course study of clinical, immunologic, ultrastructural, and cytochemical changes

Pemphigus vulgaris autoantibodies (PV IgG) promote cell detachment in epidermal cell cultures and acantholysis in the epidermis of neonatal BALB/c mice in vivo. We have studied the evolution of the immunologic and ultrastructural changes in the epidermis of BALB/c mice that receive parenteral injections of PV IgG. Neonatal BALB/c mice received a single i.p. injection of PV IgG (10 mg/g body weight) or control IgG from normal humans. The skin and serum of these animals was obtained at 0, 1, 3, 6, 12, 18, and 24 h post injection, and examined by immunofluorescence (IF), electron microscopy (EM), and immunoelectron microscopy (IEM). PV IgG was detected in the mouse serum and bound to the epidermal cells as soon as 1 h after injection by IF and IEM. The intensity of the binding in the skin (by IF) increased sharply between 3 and 6 h, and remained positive at 24 h. Early epidermal cell detachment was demonstrable by EM at 1 h as widening of the epidermal intercellular spaces (ICS), and by 6 h the ICS between desmosomes had detached completely. Desmosomal junctions are the last to separate, occurring at 12-18 h. At this point, complete cell detachment occurred in the suprabasilar layers of the epidermis. Basal cells remain attached to the underlying dermis (tombstone row). Coincident with cell detachment, intracellular tonofilaments retracted from the cell periphery and clustered in a perinuclear position. IEM confirmed the binding of PV antibodies to the surface of epidermal cells in early and established lesions. This study demonstrates that the early immunologic and ultrastructural changes that occur in human pemphigus vulgaris are reproduced in this mouse model of the disease.

Demonstration of pemphigus antibodies on the cell surface of murine epidermal cell monolayers and their internalization

The pathogenic effects of pemphigus vulgaris (PV) antibodies on epidermal cells can be demonstrated both in vitro using skin organ culture or primary epidermal cell cultures (PECC) and in vivo by passive transfer of PV antibodies into neonatal BALB/c mice. Although PV antibodies have been localized on the epidermal cell surface by several techniques, little is known about the fate of these autoantibodies subsequent to their surface binding. We have examined this, using murine PECC which express pemphigus antigen on their surface, and followed the fate of the bound antibody molecules. Forty-eight-hour PECC were incubated at 37 degrees C with PV antibodies for 20 min and then with horseradish peroxidase-labelled antihuman IgG. This was considered time 0. The monolayers were fixed with glutaraldehyde after 0, 0.5, 1, 3, 6, 18, and 24 h incubation at 37 degrees C and then processed for electron microscopy. At time 0 hour, PV antibodies is detected bound evenly along the surface of keratinocytes. Within 30 min, the bound PV antibodies becomes clustered, internalized into submembranous vesicles via surface pits, and eventually fused with lysosomes. Widening of the intercellular spaces was also seen in PECC treated with PV antibodies within the first 24 h. PECC treated with normal human IgG in parallel cultures showed no such surface binding, internalization, or cell-cell detachment. Treatment with cytochalasin-D and/or colchicine did not affect the internalization of the PV antibodies, but fusion with lysosomes was not seen in treated cultures. These findings suggest that PV antibodies binds a surface antigen and the complex is internalized and fused with lysosomes in a process that may have pathophysiologic relevance.

Human autoantibodies against a desmosomal core protein in pemphigus foliaceus

Pemphigus foliaceus (PF) is a human autoimmune disease in which antibodies are directed against the cell surface of epidermal cells with resultant blister formation. The histopathology of these blisters indicates that cells have detached from each other, and electron microscopy of early blisters shows diminished numbers, to complete loss, of desmosomes as well as abnormalities of the tonofilament-desmosome complex. In this study we demonstrate that autoantibodies from certain PF patients bind to a desmosomal core glycoprotein called desmoglein (DG) I. Proteins in extracts of normal human epidermis were separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE), then transferred to nitrocellulose or 2-aminophenylthioether paper for immunoperoxidase staining. Results of these immunoblots indicated that sera from 6 of 13 PF patients specifically and intensely stained an approximately 160,000 mol wt polypeptide, "PF antigen". Such staining was not seen with normal human sera or sera from patients with pemphigus vulgaris or bullous pemphigoid, two autoimmune blistering skin diseases that are clinically, histologically, and immunochemically distinct from PF. However, rabbit antiserum directed against DGI, that was isolated from bovine muzzle desmosomes, stained a polypeptide band which co-migrated with PF antigen. Furthermore, when proteins from extracts of normal human epidermis were electrophoresed in two dimensions (isoelectric focusing, then SDS-PAGE) before transfer to nitrocellulose for immunoperoxidase staining, PF antibodies and antibodies to DGI stained identical spots. Finally, PF sera as well as PF IgG that was affinity purified with PF antigen from normal human epidermis, both selectively bound to DGI extracted from bovine muzzle desmosomes. These studies demonstrate that the human autoantibodies from certain patients with PF, a disease of epidermal cell adhesion, are directed against a desmosomal core protein.

Distinction between epidermal antigens binding pemphigus vulgaris and pemphigus foliaceus autoantibodies

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are autoimmune blistering diseases in which antibodies develop to the cell surface of epidermal cells. In this study we sought to determine the antigenic specificity of antibodies in the sera of patients with PV and PF. Sera from 12 patients with PV were used to immunoprecipitate extracts of cultured human epidermal cells that were radiolabeled with 14C-amino acids. Immunoprecipitates were identified by SDS polyacrylamide gel electrophoresis (PAGE) and fluorography. All 12 PV sera precipitated a protein which, when reduced, displayed chains of 130,000 and 80,000 mol wt on SDS-PAGE. Electrophoresis under nonreducing conditions identified a 210,000-mol wt molecule, which was presumably formed by disulfide crosslinking of the 130,000 and 80,000-mol wt chains. Immunoprecipitates of epidermal cell extracts that were labeled with 14C-glucosamine indicated that the 130,000-mol wt chain. Seven of eight PF sera, which were run concurrently with the PV sera in this immunoprecipitation assay, did not precipitate this glycoprotein, nor did they specifically precipitate any protein. To determine if a specific molecule which reacted with antibodies in PF sera could be identified, we used immunoblot analysis of extracts of normal human epidermis. The proteins in these extracts were reduced, separated by SDS-PAGE, and electrophoretically transferred to nitrocellulose sheets or to 2-aminophenylthioether paper. Immunoperoxidase staining of the transferred proteins with PF sera indicated that four of eight PF sera contained antibodies that stained a protein band of 160,000 mol wt. Indirect immunofluorescence, using normal human skin as the substrate, indicated that IgG that was eluted from this protein band stained the epidermis in a cell surface pattern. PV sera did not specifically recognize any bands by immunoblot analysis. Immunoblots performed with PV antigen that was immunoprecipitated from cell culture extracts suggested that, once denatured for SDS-PAGE, PV antigen is no longer immunoreactive. Taken together, these data indicate that: autoantibodies contained in PV sera from various patients have a unique molecular specificity; autoantibodies from most PF sera have a specificity different from that of PV autoantibodies; and autoantibodies from various PF patients may not have identical antigenic specificities. These differences in antigenic specificity between PV and PF sera may account for the clinical and histologic differences between these diseases.