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Acantholysis produced in vitro with pemphigus serum: hydrocortisone inhibits acantholysis, while dapsone and 6-mercaptopurine do not inhibit acantholysis.

Many studies have shown that human skin in organ cultures containing pemphigus antibody undergoes acantholysis, the histologic hallmark of pemphigus vulgaris. This in vitro organ culture system provides a good model to determine if drugs used to treat pemphigus inhibit the effect of pemphigus antibody after it is produced. In this study we determined if hydrocortisone, dapsone, and 6-mercaptopurine (6-MP) could inhibit acantholysis observed in human skin organ cultures containing high constant levels of pemphigus plasma. In six experiments we demonstrated that hydrocortisone (10(-3) and 5 X 10(-4) M) present at the start of organ culture inhibited acantholysis induced by pemphigus sera. Thus, this study raises the possibility that the large doses of steroids used to treat acute pemphigus could act directly on the skin, inhibiting acantholysis in the presence of high titers of pemphigus antibody. Other effective immunosuppressive drugs, such as dapsone and 6-MP, probably do not act directly on the skin.

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Proteinase inhibitors block formation of pemphigus acantholysis in experimental models of neonatal mice and skin explants: effects of synthetic and plasma proteinase inhibitors on pemphigus acantholysis.

In organ culture experiments, the induction of pemphigus acantholysis is known to be blocked by the addition of serine proteinase inhibitors. Recently, nontoxic synthesized low molecular weight proteinase inhibitors have been clinically available for the treatment of disseminated intravascular coagulation and pancreatitis. To determine if these drugs are useful aids to treat patients with pemphigus, we examined the effect of omega-guanidino ester analogues, i.e., 1) gabexate mesilate, 2) camostat mesilate, and 3) nafamostat mesilate, on experimental pemphigus acantholysis in both organ culture and neonatal BALB/c mice. Furthermore, the effect of plasma natural proteinase inhibitors (alpha-1-proteinase inhibitor) isolated from human plasma was similarly examined. Results revealed that synthesized low molecular weight inhibitors (drugs) were able to inhibit the induction of acantholysis in organ culture system, but had little or no effect on lesion formation in the neonatal mouse system. By contrast, alpha-1-proteinase inhibitor could completely inhibit acantholysis formation in mice. These findings implied a possible new therapeutic approach using proteinase inhibitors for patients with pemphigus.

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Cantharidin-induced acantholysis in Darier's disease: does acantholysis initiate dyskeratosis?

We have examined the action of cantharidin on the skin of patients with Darier's disease, and used immunohistological techniques to determine the distribution of desmosomal components, keratin intermediate filaments, and proteases in cantharidin-induced blisters. Cantharidin induced acantholysis, but the presence of acantholysis did not trigger the development of the characteristic warty, dyskeratotic papules in patients with Darier's disease. The distribution of desmosomal components, keratins and proteases within the acantholytic keratinocytes in the cantharidin-induced blisters was similar to that previously found in acantholytic cells within lesions of Darier's disease: peripheral staining for extracellular desmosomal components was reduced; some desmosomal components were detected diffusely in the acantholytic cells; basal cell keratin markers were expressed by some suprabasal acantholytic cells, and plasminogen was detected in association with acantholytic cells. Cleavage of desmosomes did not reveal the underlying abnormality in Darier's disease.

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Appearance of "pemphigus acantholysis factor" in human skin cultured with pemphigus antibody.

These studies deal with the mechanism of pemphigus IgG-induced epidermal acantholysis. When normal human skin was culted with defined medium containing IgG from pemphigus serum, extensive epidermal acantholysis developed and heat-labile proteolytic enzyme(s) were recovered in the culture medium. The enzyme(s) displayed maximal activity at pH 6.5 when a 3H-amino acid-labeled, insoluble epidermal cell material was used as substrate. The enzyme activity increased during the first 3 days of culture and the appearance of maximal activity coincided with the time of onset of acantholysis. Acantholysis did not occur in control cultures incubated with normal IgG and the enzyme did not appear in the medium or in aqueous extracts of cultured tissues. The enzyme(s) is probably not of lysosomal origin because low pH-active proteases characteristic of these organelles remained within the cells. The effects of puromycin on appearance of enzyme activity, acantholysis and cell viability was studied. At cytotoxic concentrations, the appearance of the enzyme(s) and acantholysis were prevented, whereas at less toxic concentrations enzyme activity and acantholysis were not prevented. Because inhibition of protein synthetic rates by puromycin could not be dissociated from the cytotoxic effects, it is uncertain whether enzyme appearance and acantholysis were dependent upon living tissue or on specific protein synthesis. After pemphigus IgG was removed from the conditioned medium by DEAE cellulose and affinity column chromatography, the remaining material contained enzyme activity and caused acantholysis in fresh skin explants. Similar activities were not present in normal IgG-containing conditioned medium or unfractionated epidermal extracts from normal skin. These data indicate that when the pemphigus IgG autoantibody interacts with epidermal cell surface antigens, the cell responds by synthesis or activation of a non-IgG "pemphigus acantholysis factor" (PAF) which may be a nonlysosomal proteolytic enzyme. It is suggested that PAF causes loss of adhesion between keratinocytes and ultimately produces the characteristic acantholytic cells of pemphigus.

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Methylprednisolone inhibits pemphigus acantholysis in skin cultures.

Glucocorticosteroids are used to treat patients with pemphigus, but the mechanism of action is unknown. We studied the effect of methylprednisolone on acantholysis induced in vitro by incubation of normal skin with plasma from a patient with pemphigus. Normal human breast skin was maintained in organ cultures for several days in Ham F-10 medium. Plasma from a patient with active pemphigus vulgaris caused suprabasilar epidermal acantholysis when added to this culture system. In control cultures (F-10 medium and fetal bovine serum), no acantholysis occurred. Acantholysis was prevented when breast skin was preincubated for 24 h in a 0.25 mM solution of methylprednisolone in F-10 medium and fetal bovine serum, suggesting that methylprednisolone directly inhibits acantholysis. No suppression of acantholysis occurred when the methylprednisolone was added to the culture system simultaneously with the pemphigus plasma, suggesting a time requirement for alteration of cellular events. The inhibition of acantholysis was not caused by cell death since methylprednisolone did not alter keratinocyte viability as determined by exclusion of trypan blue dye when keratinocytes were exposed to pemphigus plasma. Similarly, the inhibition of acantholysis was not due to dissolution, alteration, or coating of pemphigus antigen on epidermal cells, since the intercellular antibodies in the plasma bound as well to methylprednisolone-treated epidermis as to untreated epidermis.

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Cantharidin-induced acantholysis: adhesion molecules, proteases, and related proteins.

Acantholysis is a feature of disorders such as Hailey-Hailey disease and Darier's disease. Immunocytochemical studies have shown internalization of desmosomal components after acantholysis. Basal cytokeratins show suprabasal expression in lesional Darier's disease. The exact mechanisms of acantholysis are still unclear. Cantharidin induces blistering, with suprabasal keratinocyte acantholysis, possibly by protease activation. Plasmin has been implicated in the pathogenesis of acantholysis in Darier's disease and Hailey-Hailey disease. We examined the distribution of desmosomal components, proteases and cytokeratins in cantharidin blisters, to compare them with those previously found in Darier's disease and Hailey-Hailey disease. Two drops of cantharidin collodion were applied to the skin of five normal volunteers. A 4-mm punch biopsy of the blister was taken, and snap frozen. Sections were stained with antibodies to desmosomal proteins (dp) 1/2, dp 3, desmosomal glycoproteins (dg) 1, 2/3, extracellular carbohydrate residues, using the lectins peanut agglutinin (PNA) and soybean agglutinin (SBA), proteases and cytokeratins. Acantholytic cells were stained diffusely with dp1/2; there was markedly reduced or absent peripheral staining for dp3, dg1, dg2/3, PNA and SBA. There was no clumping of stain. Plasminogen, fibrinogen and urokinase were expressed in some acantholytic cells. Basal keratin markers were expressed suprabasally in acantholytic cells. These results are similar to those previously obtained in Darier's disease, but different from the staining obtained in Hailey-Hailey disease. Extracellular glycosylated portions of adhesion molecules may be lost after acantholysis, perhaps as a result of conformational changes, internalization of extracellular domains, or proteolysis. The changes in the expression of plasminogen, fibrinogen, urokinase and cytokeratins in acantholytic cells in cantharidin-induced blisters are, as in Darier's disease and Hailey-Hailey disease, probably secondary to acantholysis, and changes in the shape of cells. We conclude that cantharidin blisters may be a useful model for the study of acantholysis in Darier's disease.

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Pemphigus and dietary factors. In vitro acantholysis by allyl compounds of the genus Allium.

BACKGROUND: Today it is generally accepted that every drug that possesses an active thiol group in its molecule is capable of inducing pemphigus in vivo and provoking acantholysis in vitro. We therefore suggested that plants, in particular those belonging to the Allium group, that contain several active compounds with stable disulfide and thiol groups in their molecule may cause the same. OBJECTIVE: To verify this hypothesis by investigating the in vitro acantholytic effect of three compounds of garlic. METHODS: Skin samples from donors were cultured in the presence of three compounds of garlic (i.e. allylmercaptan, allylmethylsulfide and allylsulfide) for 3 days. The skin samples were then processed for microscopic control for acantholysis. RESULTS: Results indicate that, indeed, the three garlic compounds tested are capable of inducing acantholysis in vitro. Focal and diffuse acantholysis was observed in the specimens from 4 out of 7 donors cultured in the presence of 6 and 9 mM of each of the allyl compounds for 3 days. Interestingly, tissues from a DR4+ donor proved to be more acantholysis prone than others, showing large blistering due to diffuse acantholysis, thus indicating that individual susceptibility plays a crucial role also in vitro. CONCLUSION: Garlic compounds with stable disulfide and thiol groups in their molecule are capable of inducing acantholysis in vitro. These findings lend further support to the theory that 'harmless' nutritional factors are capable of inducing acantholysis in vitro and possibly also in vivo. In view of these findings, it is suggested that nutritional factors should be added to the ever-growing list of exogenous factors capable of inducing pemphigus.

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Induction of acantholysis in organ explant culture by penicillamine and captopril.

Pemphigus is an autoimmune disease proved to be mediated by IgG autoantibodies. Skin lesions clinically and histologically identical to pemphigus may occur in patients receiving penicillamine and captopril, but some of these patients lack circulating or tissue-bound autoantibodies. Therefore, we examined the ability of these drugs to produce acantholysis directly in organ explant culture. Human skin explants were prepared from split-thickness graft skin from adults and from neonatal foreskins. Explants were cultured in media containing 0.1 to 200 mmol/L of penicillamine or captopril; parallel drug-free control cultures were also prepared. Acantholysis occurred in all split-thickness graft skin cultures incubated for 72 hours with at least 20 mmol/L of penicillamine and at 24 to 48 hours in those incubated with at least 10 mmol/L of captopril. Acantholysis occurred less frequently in foreskin cultures, being present in 1 (8%) of 12 of those exposed to at least 20 mmol/L of penicillamine and 3 (12%) of 25 of those exposed to at least 10 mmol/L of captopril. None of the parallel drug-free control cultures developed acantholysis. Subcorneal acantholysis, resembling that seen in pemphigus foliaceus, and suprabasilar acantholysis, resembling that seen in pemphigus vulgaris, were induced in vitro. Our results indicate that both drugs can act as ligands and produce acantholysis in organ explant culture in the absence of autoantibody. This ligand-induced acantholysis may also be responsible for induction of the disease in vivo in those patients who lack demonstrable autoantibodies.

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Urokinase plasminogen activator mRNA is induced by IL-1alpha and TNF-alpha in in vitro acantholysis.

The role of urokinase type plasminogen activator (uPA) has been well documented in the pathogenesis of pemphigus vulgaris (PV). Activation of plasminogen into active serine protease plasmin initiates extracellular proteolysis leading to acantholysis but the mechanisms underlying this process are not clearly understood. We have previously shown that keratinocyte derived cytokines IL-1alpha and TNF-alpha are involved in PV-induced acantholysis. In the present study we sought to examine whether keratinocyte-derived IL-1alpha and TNF-alpha are correlated with uPA induction in keratinocytes during acantholysis. Normal human keratinocytes were incubated with diluted PV serum. mRNAs for IL-1alpha, TNF-alpha and uPA were examined with RT-PCR at various time points and acantholysis was measured. IL-1alpha, TNF-alpha and uPA mRNAs were all induced in keratinocytes following PV serum stimulation; IL-1alpha/TNF-alpha mRNAs' expression was earlier than the expression of uPA mRNA. To further examine the role of IL-1alpha, TNF-alpha and uPA in acantholysis, we performed antibody blocking studies. Anti-IL-1alpha, anti-TNF-alpha and anti-uPA antibodies suppressed acantholysis by 76%, 80% and 90%, respectively. In addition, anti-IL-1alpha and anti-TNF-alpha antibodies inhibited uPA mRNA induction, whereas anti-uPA antibodies did not alter IL-1alpha/TNF-alpha mRNAs' expression. Our results confirm the role of uPA in acantholysis and suggest an involvement of IL-1alpha/TNF-alpha in uPA induction.

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Involvement of urokinase-type plasminogen activator in acantholysis induced by pemphigus IgG.

Pemphigus IgG induces acantholysis in skin organ culture without the involvement of complement. Urokinase-type plasminogen activator, a proteolytic enzyme, has been implicated in the development of acantholysis. To test this hypothesis, we prepared a rabbit anti-urokinase antibody, which inhibited the plasminogen activator activity in normal human epidermis and in cultured keratinocytes. When added to skin organ cultures along with pemphigus IgG, anti-urokinase IgG completely prevented the development of acantholysis. Normal or preimmune rabbit IgG had no effect on pemphigus IgG-induced acantholysis. Plasminogen activator converts the zymogen plasminogen to its active form plasmin, a broad specificity serine proteinase. When high concentrations of plasminogen alone were added to skin organ culture, acantholysis of the pemphigus foliaceous type was induced. Anti-urokinase antibody also inhibited plasminogen-induced acantholysis. These results strongly support a pivotal role for plasminogen activator in the development of acantholysis.

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Plasmin induces acantholysis in skin organ cultures.

Addition of human plasminogen to three different pemphigus plasma samples showed a synergistic effect on acantholysis in the skin organ culture model. Human plasmin itself, without addition of pemphigus plasma, induced typical acantholytic changes in the skin explants, causing different types of acantholysis in a dose- and time-dependent manner: in the presence of 3 CU plasmin per ml culture medium, focal suprabasilar acantholysis of pemphigus vulgaris type could be detected after 72 h incubation, whereas 15 CU/ml caused extended acantholysis of pemphigus foliaceus type in the upper epidermal layers after 24 h, and extended acantholysis of benign chronic pemphigus (Hailey-Hailey disease) type comprising all layers of the epidermis after 48 h incubation. Plasminogen activator levels (Mr 55,000 urokinase type) in tissue extracts of skin explants and in culture media were reduced after 24 and 48 h incubation with pemphigus IgG as compared to control experiments with normal human IgG; this probably resulted from urokinase inactivation by reaction with inhibitors. These results lend support to the hypothesis proposed by Hashimoto et al. in 1983 that the plasminogen activator-plasmin system could play an essential role in the protease mechanisms of pemphigus acantholysis.

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Apoptotic mechanism in pemphigus autoimmunoglobulins-induced acantholysis--possible involvement of the EGF receptor.

Pemphigus is an autoimmune cutaneous disease characterized by circulating autoantibodies that cause blistering and erosions on skin and mucous membranes. Circulating autoantibodies bind to epidermal cell membrane and cause cell-cell detachment (acantholysis), leading to epidermal tissue damage and cell death. The principal target of pemphigus vulgaris autoantibodies (PV-IgG) is desmosomal cadherin desmoglein 3 (Dsg3), a constituent of desmosomes, mediating cell-cell adhesion. Several hypotheses for the mechanisms of acantholysis induction by PV-IgG exist, but the actual mechanism is not clear as yet. We have previously reported on apoptosis induction in PV-IgG-mediated epidermal tissue and cell damage as a possible mechanism of acantholysis and cell death (Wang et al. 2004, Apoptosis, 9:131-143). In this study we investigated the involvement of the EGFR and intracellular signal transduction pathways in the PV-IgG-induced apoptosis. We show here that PV-IgG induced activation/autophosphorylation of EGFR in cultured keratinocytes in vitro. The specific tyrosine kinase inhibitor AG1478 abrogated EGFR autophosphorylation, cell death, FasL appearance and acantholysis, all induced by PV-IgG, in parallel, confirming the involvement of EGFR in this Fas apoptotic cascade. Activation of EGFR was followed by phosphorylation of its downstream substrates, MAP kinase ERK and transcription factor c-Jun, and internalization of EGFR. Pharmacological inactivation of the EGFR and ERK kinase activities, by use of specific inhibitors AG1478 and PD98059 respectively, blocked PV-IgG-induced phosphorylation of EGFR, ERK and c-Jun and cellular apoptosis, measured by flow cytometry and caspase 3 activity. Prolonged activation of EGFR by PV-IgG led to dramatic internalization of this receptor, possibly reducing the ability of the cell to perform survival signals. This suggests that activation of EGFR, followed by its internalization, is pivotal for intracellular apoptotic signal transduction via ERK/c-Jun pathways, leading to acantholysis. Our experimental data indicate that the EGFR is instrumental in transducing apoptotic/acantholytic signals in keratinocytes cultures in response to PV-IgG treatment. The acantholytic effect caused by PV-IgG binding to cell surface receptors begins with and depends on cell surface receptor (EGFR) activation of intracellular signaling pathways (ERK pathway) and apoptosis induction (FasR pathway), which later lead to major cell-cell separation (acantholysis) and cell death.

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The pathogenic role of pemphigus antibodies and proteinase in epidermal acantholysis.

The pathogenic role of pemphigus autoantibodies and proteinases in epidermal acantholysis has been studied in organ cultures of normal human skin. Dose-dependent acantholysis occurred in skin explants cultured in medium containing 2-30 mg/ml of gamma-globulin from pemphigus serum. Acantholysis was not seen in explants cultured with 2 mg/ml pemphigus gamma-globulin although antibody binding to the epidermis was observed. Some degenerative changes in addition to acantholysis were present when 30 mg/ml pemphigus gamma-globulin was added to the medium. The addition of N,ethylmaleimide(NEM) and ethylene diamine tetraacetate(EDTA) prevented binding of pemphigus antibody to epidermis in culture. Soybean trypsin inhibitor and pepstatin had no effect on binding of pemphigus antibody to the epidermis but they did inhibit acantholysis in vitro. Our results suggest that pemphigus-induced acantholysis may be caused by at least 2 different types of enzyme.

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Production of epidermal acantholysis in normal human skin in vitro by the IgG fraction from pemphigus serum.

Normal human skin was maintained in organ cultures for several days in Ham's F-10 medium with good preservation of the epidermal cells. When the partially purified IgG fraction from the pooled sera of patients with pemphigus vulgaris or pemphigus foliaceous was added to this culture system, after 24 hr some evidence of epidermal acantholysis was seen. By 72 hr, extensive suprabasilar epidermal acantholysis had occurred in which the acantholytic cells were indistinguishable histologically from the acantholytic cells in biopsies from skin lesions of patients with pemphigus vulgaris. In the control cultures (i.e., F-10 medium or F-10 medium + normal human serum IgG), none of these changes was seen. Direct immunofluorescent staining of these explants using fluorescein-labeled goat antihuman IgG showed that by 6 hr binding of the pemphigus IgG had occurred in the intercellular cement substance of the epidermis. The staining intensity was maximal by 18 to 20 hr. When the pemphigus serum was fractionated by DEAE-cellulose column chromatography, three major IgG-containing peaks (presumably IgG) were eluted which bound to the epidermoid intercellular substance and caused acantholysis in culture. The complement system did not play a role in the antibody-induced acantholysis since complement was not included in this system and heating the reconstituted F-10 + pemphigus IgG for 1 hr at 58 degrees C did not destroy the acantholytic activity. Autoradiographic experiments showed that after about 2 days in culture the rates of incorporation of RNA and protein precursors in the suprabasilar cells in the presence of pemphigus IgG were reduced to less than 10% of the normal IgG controls, whereas these synthetic activities of the basal cells were only slightly affected. These observations lead to the proposal that it is the interaction of the pemphigus autoantibody(s) with the suprabasilar epidermal cell which initiates and possibly substains the process(es) of acantholysis.

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An organ culture model for the study of pemphigus acantholysis.

An in vitro model for the study of pemphigus acantholysis has been developed. The histological changes of pemphigus vulgaris were reproduced in vitro in organ culture by growing normal human skin in the presence of pemphigus vulgaris or pemphigus foliaceus sera. At 24 h a suprabasilar split was noted and at 72 h extensive suprabasilar acantholysis developed. Direct immunofluorescent tests demonstrated that pemphigus antibody became bound to the epidermal intercellular space antigen(s) during the first 6-12 h. As acantholysis increased the presence of tissue-fixed antibody decreased. The fixation of the pemphigus antibody to the skin prior to the development of acantholysis provides strong evidence for the pathogenetic role of this antibody in the production of acantholysis. The data suggest that complement is not required in this model for the production of the acantholytic changes of pemphigus since heating the serum for 30 min at 56 degrees C did not destroy the acantholytic activity and no complement (C3) could be detected by DIF of organ culture explants.

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Grover's disease (transient acantholytic dermatosis): relationship of acantholysis to acrosyringia.

Transient acantholytic dermatosis is often associated with excessive sweating, fever, and bed confinement. The pathogenesis of this disease has been postulated to be poral occlusion of damaged eccrine intraepidermal ducts. Histological and immunohistochemical and ultrastructural studies were performed on 10 biopsies from 10 patients with transient acantholytic dermatosis. Immunoreactions for carcinoembryonic antigen and cytokeratin-7 to identify eccrine duct epithelium were performed on all 11 biopsies. In addition, 5 of the biopsies were immunoreacted for cytokeratin 8. All immunoreactions were reviewed independently by two observers to determine extent of reactivity and whether it correlated with areas of epidermal acantholysis. Among the 11 biopsies, 8 showed acantholysis not associated with eccrine duct outflow tracts. In 2 biopsies the acantholysis was consistently associated with acrosyringea; in one case acantholysis was inconsistently associated with eccrine outflow tracts. Epidermal acantholysis in patients with Grover's disease is associated with the outflow tracts of eccrine ducts in a subgroup of patients. Although leakage of sweat from occluded sweat ducts in acrosyringia may be the mechanism operating in a subgroup of patients with Grover's disease, this does not appear to be the subgroup of patients in whom Grover's disease develops in the setting of being bedridden and/or sweating.

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Functional involvement of urokinase-type plasminogen activator receptor in pemphigus acantholysis.

Urokinase-type plasminogen activator (uPA) has been well documented in the development of pemphigus acantholysis. The function of its receptor (uPA-R) in pemphigus acantholysis has only recently attracted attention. Increased expression of uPA-R has been demonstrated in pemphigus vulgaris. In this study, we have further explored the functional involvement of uPA-R in pemphigus acantholysis. Our results show that uPA-R expression is significantly increased in acantholytic foci of pemphigus vulgaris and pemphigus foliaceus but not in bullous pemphigoid or normal skin specimens; the expression of uPA-R in cultured human keratinocytes is subjected to regulation by pemphigus vulgaris IgG but not by pemphigoid IgG or normal human IgG; furthermore, anti-uPA-R monoclonal antibody effectively inhibits pemphigus vulgaris IgG induced acantholysis in skin organ cultures. These data suggest that uPA-R may play an important role in the pathogenesis of pemphigus acantholysis.

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