Unraveling the significance of IgE autoantibodies in organ-specific autoimmunity: lessons learned from bullous pemphigoid

Bullous pemphigoid (BP), a cutaneous autoimmune blistering disease, has provided a useful model to elucidate a role for IgE in autoimmunity. IgE antibodies specific for the BP180 autoantigen are detected in sera and biopsy samples from the majority of BP patients. In BP biopsies, both IgE and BP180 antigen localize to the surface of mast cells, and incubation of circulating basophils from these patients with BP180 protein triggered degranulation. The in vivo pathogenicity of BP180-specific IgE was confirmed in mouse models, where injection of purified BP IgE into human skin grafted onto nu/nu mice replicated the early phase of lesion development, including mast cell degranulation, eosinophil infiltration and development of urticarial plaques. In addition, IgE antibodies from patient sera bind to BP180 on basal keratinocytes, resulting in internalization of BP180, production of inflammatory cytokines, IL-6 and IL-8, and a decrease in the number of hemidesmosomes at the basement membrane zone. These findings have led to therapeutic trials of the anti-IgE monoclonal antibody omalizumab in BP, resulting in substantial improvement in the patients' disease. Overall, the work in BP provides the first evidence for a pathogenic role for IgE in autoimmunity.

Role of IgE in bullous pemphigoid: a review and rationale for IgE directed therapies

Bullous pemphigoid (BP) is an autoimmune blistering disorder that is characterized by elevated total serum IgE and both IgG and IgE class autoantibodies directed against the hemidesmosomal proteins BP180 and BP230. In BP, IgE is found at the basement membrane zone and coating mast cells in lesional skin. IgE binding to immune cells is mediated through its high affinity receptor, FcεRI on the surface of mast cells, basophils and eosinophils. In BP lesions, IgE binding is thought to be a critical step in the activation of these cells. Models of the disease have demonstrated that BP IgE can replicate the early stages of BP lesion formation. These findings suggest that IgE inhibition may be a therapeutic approach for BP. Omalizumab is a humanized monoclonal antibody that inhibits IgE binding to FcεRI and is currently FDA-approved for the treatment of severe allergic asthma. To date, two case reports have each described the efficacy of omalizumab in a patient with severe recalcitrant BP. These studies are the first to provide clear evidence of the contribution of IgE autoantibodies in the pathogenesis of human BP and suggest that omalizumab may provide an additional therapeutic tool for treatment.

New and innovative interventions in the management of pemphigus

Pemphigus is a rare autoimmune blistering disease usually treated with systemic glucocorticoids with adjuvant immunosuppressants or anti-inflammatories. However significant morbidity and mortality is associated with these treatments. This review discusses conventional therapeutic options, as well as new and emerging therapies that may be safer alternatives to broad-based immunosuppression.

Autoimmunity in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease primarily of the elderly, characterized by the development of urticarial plaques surmounted by subepidermal blisters and the deposition of immunoglobulins and complement at the basement membrane zone (BMZ). Immunologically, it is characterized by the development of autoantibodies targeting two structural proteins of the hemidesmosomes, BP180 (collagen XVII) and BP230. BP230 is intracellular protein of the hemidesmosomal plaque, while BP180 is a transmembrane protein with a collagenous extracellular domain. The weight of experimental evidence indicates that BP180 is the primary target of the pathogenic autoantibodies. Autoantibodies are of both the IgG or IgE class, and their binding in the skin triggers complement activation, mast cell degranulation and the accumulation of inflammatory cells, including eosinophils, mast cells, and neutrophils. Release of proteases from these inflammatory cells results in cleavage of the BMZ and blister formation. While the initial triggers of autoantibody production remain obscure, a better understanding of the pathomechanisms of blister formation will lead to the development of new therapeutic strategies.

Human cytomegalovirus infection inhibits epidermal growth factor (EGF) signalling by targeting EGF receptors

Infection with human cytomegalovirus (HCMV) is known to involve complex interactions between viral and cellular factors resulting in perturbation of a number of cellular functions. Specifically, HCMV infection targets control of the cell cycle, cellular transcription and immunoregulation, presumably to optimize the cellular environment for virus persistence and productive infection. Here, we show that HCMV infection also prevents external signalling to the cell by disrupting the function of epidermal growth factor receptor (EGFR). Infection with HCMV resulted in a decrease in cell-surface expression of EGFR. This decrease was correlated with a concomitant decrease in steady-state levels of EGFR protein. Consistent with this, HCMV inhibited EGF-mediated receptor autophosphorylation. Infection with a mutant HCMV deleted of all viral gene products known to be involved in down-regulation of MHC Class I receptors still resulted in this down-regulation, implying that EGFR down-regulation by HCMV is mediated by a novel virus function. We suggest that a primary goal of HCMV is to 'isolate' the infected cell from host-mediated signals so that the cell responds solely to an array of virus-specific signals which optimize the cell for virus production.

Activator-mediated disruption of sequence-specific DNA contacts by the general transcription factor TFIIB

The transcription factor TFIIB plays a central role in preinitiation complex assembly, providing a bridge between promoter-bound TFIID and RNA Polymerase II. TFIIB possesses sequence-specific DNA-binding ability and interacts with the TFIIB-recognition element (BRE), present in many promoters. Here we show that the BRE suppresses the basal level of transcription elicited by a core promoter, which increases the amplitude of transcriptional stimulation in the presence of an activator protein. Further, we find that an activator can disrupt the TFIIB-BRE interaction within a promoter-bound complex. Our results reveal a novel function for activators in the modulation of core promoter recognition by TFIIB.

A critical role for neutrophil elastase in experimental bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune skin disease characterized by subepidermal blisters and autoantibodies against 2 hemidesmosome-associated proteins, BP180 and BP230. The immunopathologic features of BP can be reproduced in mice by passive transfer of anti-BP180 antibodies. Lesion formation in this animal model depends upon complement activation and neutrophil recruitment. In the present study, we investigated the role of neutrophil elastase (NE) in antibody-induced blister formation in experimental BP. Abnormally high levels of caseinolytic activity, consistent with NE, were detected in extracts of lesional skin and blister fluid of mice injected with anti-BP180 IgG. The pathogenic anti-BP180 IgG failed to induce subepidermal blistering in NE-null (NE(-/-)) mutant mice. NE(-/-) mice reconstituted with neutrophils from wild-type mice became susceptible to experimental BP. Wild-type mice given NE inhibitors (alpha1-proteinase inhibitor and Me-O-Suc-Ala-Ala-Pro-Val-CH(2)Cl), but not mice given cathepsin G/chymase inhibitors (alpha1-antichymotrypsin or Z-Gly-Leu-Phe-CH(2)Cl), were resistant to the pathogenic activity of anti-BP180 antibodies. Incubation of murine skin with NE induced BP-like epidermal-dermal detachment. Finally, NE cleaved BP180 in vitro and in vivo. These results implicate NE directly in the dermal-epidermal cleavage induced by anti-BP180 antibodies in the experimental BP model.

The anti-desmoglein 1 autoantibodies in pemphigus vulgaris sera are pathogenic

Pemphigus vulgaris and pemphigus foliaceus are two closely related, but clinically and histologically distinct, autoimmune skin diseases. The autoantigens for pemphigus vulgaris and pemphigus foliaceus are desmoglein 3 and desmoglein 1, respectively. The anti-desmoglein 1 antibodies in pemphigus foliaceus and anti-desmoglein 3 antibodies in pemphigus vulgaris are pathogenic as determined by immunoglobulin G passive transfer animal models. More than 50% of pemphigus vulgaris sera also contain anti-desmoglein 1 autoantibodies; however, the pathogenicity of the anti-desmoglein 1 autoantibodies in pemphigus vulgaris remains unknown. In this study, we used soluble recombinant extracellular domains of desmoglein 1 and desmoglein 3 to obtain affinity-purified anti-desmoglein 1 and anti-desmoglein 3 autoantibodies from pemphigus vulgaris sera and examined the pathogenicity of each fraction separately using the passive transfer mouse model. By immunoprecipitation, the purified anti-desmoglein 1 and anti-desmoglein 3 showed no cross-reactivity. The anti-desmoglein 1 autoantibodies in pemphigus vulgaris induced typical pemphigus foliaceus lesions in neonatal mice, whereas the anti-desmoglein 3 fraction induced pemphigus vulgaris-like lesions. In addition, the pathogenic anti-desmoglein 1 and anti-desmoglein 3 autoantibodies in pemphigus vulgaris had predominant IgG4 subclass specificity. These findings suggest that the anti-desmoglein 1 antibodies in pemphigus vulgaris are pathogenic.

Hedgehog hives

BACKGROUND

Hedgehogs are increasingly popular pets in the United States and Europe. A number of infections may be acquired from these animals, and hedgehogs are possible hosts of parasites. However, to our knowledge there arc no previous reports of urticarial reactions to hedgehogs.

OBSERVATIONS

We describe 3 patients who developed an acute, transient, urticarial reaction after contact with the extended spines of pet hedgehogs. One patient also developed a more prolonged reaction at the site of contact. Interestingly, all 3 patients had documented allergies to cats and/or dogs. The results of prick testing in 1 patient to an extract of hedgehog dander produced an immediate wheal-and-flare reaction.

CONCLUSIONS

A variety of dermatologic disorders may be seen in handlers of hedgehogs. Due to the increasing popularity of these animals as pets, it is likely that these reactions will be noted more frequently by dermatologists. The presence of allergies to other pets may be predictive of hedgehog hives and further investigation of the cross reaction of various animal antigens may clarify this relationship.

A bullous pemphigoid-like skin eruption after a chemical burn

Bullous pemphigoid is a blistering disorder characterized by antibody deposition in the lamina lucida of the basement membrane zone. In addition to the idiopathic form, there are many agents that have been implicated in inducing bullous pemphigoid or bullous pemphigoid-like lesions. We describe a patient who developed a bullous pemphigoid-like eruption after a chemical burn.

The systematic evaluation of the skin in children

A large proportion of children seen by primary care pediatricians involve problems related to the skin. In this chapter, the importance of history and, particularly, physical examination in the diagnosis of various skin disorders is discussed. The ability to describe a rash using proper terminology will help narrow the differential and enable one to communicate what is seen to other physicians. The various primary and secondary lesions that may be present will be described along with various dermatoses as examples. Four common skin disorders that often fool the primary care physician are also discussed.

Epitope spreading: lessons from autoimmune skin diseases

Autoimmune diseases are initiated when patients develop aberrant T and/or B cell responses against self proteins. These responses presumably are directed to single immunogenic epitopes on these proteins. Recent data in animal models of autoimmune diseases suggest that the targets of immune responses in autoimmunity do not remain fixed, but can be extended to include other epitopes on the same protein or other proteins in the same tissue, a phenomenon termed "epitope spreading." The "epitope spreading" phenomenon also applies to situations in which tissue damage from a primary inflammatory process causes the release and exposure of a previously "sequestered" antigen, leading to a secondary autoimmune response against the newly released antigen. In experimental autoimmune animal diseases, "epitope spreading" seems to have significant physiologic importance in determining the course and duration of disease. In this paper, we review the current concepts in animal models of autoimmune diseases in order to define the "epitope spreading" phenomenon, and we then propose how this phenomenon might play a significant role in the development and the course of autoimmune skin diseases. Hopefully, an understanding of "epitope spreading" will help the dermatology community to better understand the pathogenesis of autoimmune skin diseases and to rationally fashion disease-specific immune therapy in the future.

T lymphocytes from a subset of patients with pemphigus vulgaris respond to both desmoglein-3 and desmoglein-1

Pemphigus vulgaris and pemphigus foliaceus are cutaneous autoimmune diseases characterized by intraepithelial blisters and autoantibodies to desmosomal glycoproteins. The antigens recognized by pemphigus vulgaris and pemphigus foliaceus autoantibodies are desmoglein-3 (Dsg3) and desmoglein-1 (Dsg1), respectively. Dsg3 and Dsg1 are members of the desmoglein subfamily of the cadherin supergene family of cell adhesion molecules. It has been well documented that a subset of pemphigus vulgaris sera have IgG reactivity to both Dsg1 and Dsg3, suggesting that Dsg1 may also participate in the autoimmune response of these patients. The cellular mechanisms of T cell autoimmunity in these patients, however, are completely unknown. In this study, we tested the proliferative responses of T lymphocytes from eight pemphigus vulgaris patients after incubation with Dsg3 and Dsg1 fusion proteins. The sera of four of these PV patients showed reactivity with both Dsg1 and Dsg3, whereas the remaining four reacted only with Dsg3. We found that T cells obtained from those patients that exhibited the combined Dsg1/Dsg3 autoantibody reactivity showed a proliferative response after exposure to either Dsg1 or Dsg3 fusion proteins. The cellular responses to both of these recombinant proteins were highly specific and restricted to the CD4-positive T cell population. T cells from pemphigus vulgaris patients with no anti-Dsg1 serum reactivity showed a proliferative response to Dsg3, but not to Dsg1. The Dsg1 fusion protein used in this study has minimal sequence homology with Dsg3. Thus, this study provides the first evidence that T cells from a subset of pemphigus vulgaris patients respond to both Dsg1 and Dsg3.

Mechanisms of acantholysis in pemphigus vulgaris: role of IgG valence

Pemphigus vulgaris (PV) is a dermatosis mediated by autoantibodies against desmoglein 3 (Dsg3). It was known that intraperitoneal (i.p.) injections of PV IgG and PV F(ab')2, but not of PV Fab, into neonatal mice reproduced the key features of the disease in these animals. It was proposed that crosslinking of antigen by bivalent PV autoantibodies may trigger acantholysis in PV. In the present study, we have used subcutaneous (s.c.) injections of PV IgG and its proteolytic fragments into neonatal mice to test equimolar amounts of these autoantibody fractions. Mice developed clinical and histological features of PV in a dose-dependent manner following a similar time course. PV IgG and Fab fractions induced acantholysis as early as 2 hr after the injection. It was also demonstrated that sc injections of PV Fab were more effective in inducing disease than ip injections. PV autoantibodies may bind an "adhesive site" of Dsg3 and impair its function, thus triggering acantholysis.

Mechanisms of acantholysis in pemphigus foliaceus

Pemphigus foliaceus (PF) is a dermatosis characterized by subcorneal vesicles and pathogenic IgG autoantibodies against desmoglein 1. PF IgG passively transferred into neonatal mice induces a blistering disease that duplicates the key findings of PF. In this study we have used this animal model to investigate the role of complement and IgG valence in triggering blister formation. In the passive transfer experiments, we found that PF IgG, as well as the F(ab')2 and Fab fragments, was capable of inducing the typical subcorneal blistering disease in both complement-deficient and complement-sufficient mice. Moreover, the disease activity in these mice correlated well with the dose of IgG or its proteolytic fragments injected in the animals. We conclude that neither complement activation nor IgG-mediated cell surface antigen crosslinking is required for the induction of acantholysis in the experimental PF model.

Mucosal and mucocutaneous (generalized) pemphigus vulgaris show distinct autoantibody profiles

Pemphigus vulgaris is an autoimmune bullous disorder characterized by autoantibodies directed against desmoglein 3. A group of 19 pemphigus vulgaris sera were characterized by immunoblotting, immunofluorescence, immunoprecipitation, and the passive transfer mouse model. The aim of these studies was to determine the specificity of the autoantibody response in these patients. All patients had clinical and histologic evidence of pemphigus vulgaris. Fogo selvagem sera (n = 8), bullous pemphigoid sera (n = 8), antinuclear antibodies positive sera from patients with lupus erythematosus (n = 2), and normal human sera (n = 8) were used as controls. All pemphigus vulgaris patients showed titers of IgG autoantibodies by indirect immunofluorescence > or = 1:60, predominantly of the IgG4 subclass and immunoprecipitated recombinant desmoglein 3 expressed in the baculovirus system. Patients with disease localized to the mucous membranes showed no reactivity with desmoglein 1 and only one had weak reactivity with mouse skin by indirect immunofluorescence (titer = 1:20). Sera of four of these mucosal patients were tested in the mouse model and three of four did not elicit skin or mucosal disease in the animals. In contrast, sera from all seven patients with disease involving the skin and mucous membranes (generalized disease) produced disease in neonatal mice. In one patient the disease evolved from pure mucosal involvement associated with anti-desmoglein 3 antibodies to a disorder involving mucosas and skin. This transition was associated with the appearance of anti-desmoglein 1 antibodies in the patient's serum. These studies indicate that the autoantibody response in pemphigus vulgaris is heterogeneous. Epitopes recognized by some pemphigus vulgaris sera are species specific and others may be mucosal specific.

A major role for neutrophils in experimental bullous pemphigoid

Bullous pemphigoid (BP) is an inflammatory subepidermal blistering disease associated with an IgG autoimmune response to the hemidesmosomal protein, BP180. Using a passive transfer mouse model, our group has shown previously that antibodies to the murine BP180 (mBP180) ectodomain are capable of triggering a blistering skin disease that closely mimics human BP. In this study, we investigated the role of neutrophils in the immunopathogenesis of this disease model. BALB/c mice depleted of circulating neutrophils by treatment with neutrophil-specific antibodies were no longer susceptible to the pathogenic effects of anti-mBP180 IgG. IgG and complement were deposited at the dermal-epidermal junction of these animals, but there was no evidence of inflammatory infiltration or blistering. C5-deficient mice, which are resistant to the pathogenic activity of anti-mBP180 IgG, could be made susceptible to this IgG-mediated blistering disease by intradermal administration of a neutrophil chemoattractant, IL-8 or C5a. Intraperitoneal injection of IL-8, which sequesters neutrophils in the peritoneal cavity, interferes with anti-mBP180-induced neutrophilic infiltration of the skin and prevented the development of BP disease in BALB/c mice. These findings provide the first direct evidence that neutrophils recruited to the skin via a C5-dependent pathway play an essential role in subepidermal blister formation in experimental BP, and suggest new directions for disease intervention.

Nonsecretory IgA1 autoantibodies targeting desmosomal component desmoglein 3 in intraepidermal neutrophilic IgA dermatosis

Intraepidermal neutrophilic IgA dermatosis, a rare skin disease entity manifested with blisters and pustules clinically and lower epidermal blister, acantholysis, and neutrophilic infiltration pathologically, was first reported in 1985. Although the disease is characterized by IgA autoantibodies targeting the epithelial cell surface component, the target antigen has not been determined. We investigated a patient with this disease by histopathology, direct and indirect immunofluorescence, immunoblotting, and immunoadsorption studies. The pustular lesion was characterized by blister at the lower epidermis, acantholysis, and neutrophilic infiltration. Nonsecretory IgA1 subclass autoantibodies targeting the lower epithelial cell surfaces were detected in the patient's skin and serum. The patient's IgA autoantibodies labeled a recombinant desmosomal protein desmoglein 3 on immunoblotting and the immunolabeling of epithelial cell surfaces was eliminated by preadsorption with desmoglein 3. Thus, desmoglein 3 is identified as a target antigen in intraepidermal neutrophilic IgA dermatosis. The ability of IgA1 autoantibodies to bind neutrophils may be responsible for the prominent neutrophilic infiltration observed histopathologically and for the pustular lesions observed clinically.

Vulvar basal cell carcinoma

BACKGROUND

Vulvar basal cell carcinoma is a rare neoplasm that often displays aggressive biologic behavior. Recurrence after simple excision is common, and metastases have been reported. Early diagnosis is essential and rests upon histopathologic examination of biopsy specimens, since the clinical appearance of these neoplasms may be deceptively innocent.

CASE

A 65-year-old woman was seen with a nonhealing skin lesion on the right vulva. Physical examination revealed a 0.3 X 0.3 cm crusted papule on the right labium majus. A saucerization biopsy was performed. Histopathologic examination of the biopsy specimen revealed basal cell carcinoma. The patient underwent Mohs micrographic excision of the tumor, the total extent of which measured 0.9 X 1.8 cm.

CONCLUSION

Vulvar basal cell carcinoma is a rare but important consideration in the differential diagnosis of cutaneous vulvar lesions. Accurate diagnosis depends upon a high index of suspicion, biopsy, and histopathologic examination. Mohs micrographic excision is the treatment of choice.

Development and characterization of desmoglein-3 specific T cells from patients with pemphigus vulgaris

Pemphigus vulgaris (PV) is a cutaneous autoimmune disease characterized by blister formation in the suprabasilar layers of skin and mucosae and anti-desmoglein-3 (Dsg3) autoantibodies bound to the surface of lesional keratinocytes and circulating in the serum of patients. This disease can be reproduced in neonatal mice by passive transfer of patients' IgG, indicating that humoral immunity plays an important role in the pathogenesis of PV. Currently, the role of T lymphocytes in the development of PV is not clear. Here, we report that three immunoreactive segments of the ectodomain of Dsg3 specifically induced proliferation of T cells from PV patients. We found that T lymphocytes from 13 out of 14 patients responded to at least one of three Dsg3 peptides. T cells from controls and other patient groups did not respond to these Dsg3 peptides. The major T cell population stimulated by these Dsg3 peptides was CD4 positive. Dsg3-specific T cell lines and clones were developed and were shown to express a CD4 positive memory T cell phenotype. Upon stimulation, these cell lines and clones secreted a Th2-like cytokine profile. The Dsg3 responses of these T cells were restricted to HLA-DR, and not -DQ and -DP, of the major histocompatibility complex. This information will help to elucidate the cellular immune abnormalities leading to production of pathogenic IgG autoantibodies in patients with PV.

An active focus of high prevalence of fogo selvagem on an Amerindian reservation in Brazil. Cooperative Group on Fogo Selvagem Research

Fogo Selvagem (FS) is an autoimmune disease characterized by subcorneal vesicles and antidesmoglein-1 autoantibodies. Previous epidemiologic data have linked the onset of FS to exposure to an environmental antigen(s). This investigation describes a unique human settlement with an extraordinarily high prevalence of FS. This community is made up of Amerindians belonging to the Terena tribe, which has settled on the Limao Verde reservation in the state of Mato Grosso do Sul in Brazil. Twenty-six well-characterized FS cases have been identified within a total population of 998, yielding a prevalence of 2.6%. Seventeen of the patients (65 %) were males, and over 50% were older than 30 y of age. The incidence of the disease shows temporal periodicity, i.e., years with several cases of FS alternating with years with no cases. Over one-half of the cases occurred in genetically related family members. Another Terena reservation, the Ipegue/Taunay, located 90 km west of the Limao Verde reservation, was also evaluated as a control group. This reservation, with a population of 2203, had no recorded cases of FS. Thus, the Limao Verde reservation represents a new focus of FS in which the disease exhibits temporal, geographic, and familial clustering. These results suggest that the environmental antigen or antigens precipitating FS are endemic to the Limao Verde reservation. This reservation appears to be an ideal population for carrying out sero-epidemiologic, genetic, and environmental studies aimed at disclosing the etiology of FS.

Progressive osseous heteroplasia

BACKGROUND

Primary heterotopic ossification beginning in childhood is quite rare but occurs in several well-described conditions, such as Albright hereditary osteodystrophy, fibrodysplasia ossificans progressiva, and platelike osteoma cutis. Recently, a new disorder called progressive osseous heteroplasia (POH) has been described in the orthopedic literature. Primary cutaneous calcification and ossification beginning in infancy are presenting signs of this progressive and potentially debilitating disorder.

OBSERVATIONS

We describe 2 children with POH who were recently seen at Children's Hospital of Wisconsin. Both children were female and developed cutaneous calcification and ossification within the first 6 months of life. Both girls had progression of the lesions to involve ossification of the deeper tissues. No abnormalities in calcium, phosphorus, vitamin D, or parathyroid hormone levels were identified in these patients. No associated anomalies were detected. Biopsy results from the lesions showed calcinosis cutis superficially, with both endochondral and intramembranous bone formation in the deeper tissues.

CONCLUSIONS

Progressive osseous heteroplasia must now be included in the differential diagnosis of primary cutaneous ossification beginning in childhood. Because the first clinical manifestations of POH appear in the skin. It is important for dermatologists to be aware of this newly described condition.

Molecular mapping of a pathogenically relevant BP180 epitope associated with experimentally induced murine bullous pemphigoid

Bullous pemphigoid (BP) and herpes gestationis (HG) are subepidermal blistering diseases associated with an autoimmune response directed against BP180, an epidermal hemidesmosomal glycoprotein. The pathogenic relevance of this Ag/Ab system was established by the recent demonstration that IgG Abs reactive with the murine form of BP180 (mBP180) are capable of triggering a subepidermal blistering disease after passive transfer into neonatal BALB/c mice. The aim of the present study was to determine the fine specificity of the pathogenically relevant Abs in this experimental model of BP. Four high titer rabbit-anti-mBP180 antisera were included in this analysis--only two of which exhibited pathogenic activity in the passive transfer model. Immunoblot analysis using a panel of mBP180 deletion mutants revealed that each of the four rabbit sera reacted with at least three distinct sites on the mBP180 ectodomain; however, this technique failed to distinguish between the reactivity patterns of the pathogenic and nonpathogenic sera. An alternative technique, liquid phase immunoadsorption analysis, was used to identify one mBP180 antigenic site, comprising 9 to 12 amino acids and designated mBP1, that was specifically recognized by the two pathogenic sera. Pre-adsorption of pathogenically active IgG preparations with fusion proteins containing the mBP1 antigenic site resulted in complete blocking of immunofluorescence reactivity with the murine basement membrane zone (BMZ) and in complete neutralization of pathogenic activity. Anti-BMZ reactivity displayed by nonpathogenic Abs was not altered or diminished by pre-adsorption with this same mBP180 recombinant protein. These findings should help to elucidate the immunopathologic mechanisms responsible for human BP and HG and may have significant implications in the diagnosis and treatment of these autoimmune diseases.

Molecular mapping of a pathogenically relevant BP180 epitope associated with experimentally induced murine bullous pemphigoid

Bullous pemphigoid (BP) and herpes gestationis (HG) are subepidermal blistering diseases associated with an autoimmune response directed against BP180, an epidermal hemidesmosomal glycoprotein. The pathogenic relevance of this Ag/Ab system was established by the recent demonstration that IgG Abs reactive with the murine form of BP180 (mBP180) are capable of triggering a subepidermal blistering disease after passive transfer into neonatal BALB/c mice. The aim of the present study was to determine the fine specificity of the pathogenically relevant Abs in this experimental model of BP. Four high titer rabbit-anti-mBP180 antisera were included in this analysis--only two of which exhibited pathogenic activity in the passive transfer model. Immunoblot analysis using a panel of mBP180 deletion mutants revealed that each of the four rabbit sera reacted with at least three distinct sites on the mBP180 ectodomain; however, this technique failed to distinguish between the reactivity patterns of the pathogenic and nonpathogenic sera. An alternative technique, liquid phase immunoadsorption analysis, was used to identify one mBP180 antigenic site, comprising 9 to 12 amino acids and designated mBP1, that was specifically recognized by the two pathogenic sera. Pre-adsorption of pathogenically active IgG preparations with fusion proteins containing the mBP1 antigenic site resulted in complete blocking of immunofluorescence reactivity with the murine basement membrane zone (BMZ) and in complete neutralization of pathogenic activity. Anti-BMZ reactivity displayed by nonpathogenic Abs was not altered or diminished by pre-adsorption with this same mBP180 recombinant protein. These findings should help to elucidate the immunopathologic mechanisms responsible for human BP and HG and may have significant implications in the diagnosis and treatment of these autoimmune diseases.

Calcifying disorders of the skin

Calcium is vital to many biologic processes. In skin, it has a profound effect on keratinocyte proliferation, differentiation, and cell-cell adhesion. Serum calcium is tightly regulated by parathyroid hormone and 1,25(OH)2D3. Despite this careful regulation, calcification and ossification of cutaneous and subcutaneous tissues may occur. Cutaneous calcification may be divided into four major categories: dystrophic, metastatic, idiopathic, and iatrogenic. Dystrophic calcification occurs as a result of local tissue injury or abnormalities. Metastatic calcification results from abnormal calcium and/or phosphate metabolism. Virtually any process that calcifies may secondarily ossify. Primary ossification may rarely occur.

Expression pattern of the bullous pemphigoid-180 antigen in normal and neoplastic epithelia

BP180 is a 180kDa hemidesmosomal protein recognized by bullous pemphigoid (BP) and pemphigoid gestationis (PG) autoantibodies. Recent cloning and sequence analysis performed by our laboratory have revealed that BP180 is a transmembrane protein with a long extracellular collagen-like region. A rabbit polyclonal antibody has been generated against a recombinant protein, designated GST-N delta 1, containing a segment of the BP180 ectodomain. The resulting antiserum, RN delta 1A, was shown to specifically react with BP180 on immunoblot, and labelled the extracellular region of the epidermal hemidesmosome on immunoelectron microscopy. A panel of normal and neoplastic human tissues were analysed by indirect immunofluorescence (IF) and RN delta 1A, to determine the distribution of BP180. A total of nine basal cell carcinomas (BCCs) and four squamous cell carcinomas (SCCs) of the skin were also studied. Intense IF staining was seen along the basement membrane zone (BMZ) of the epidermis, hair follicles, and the periphery of sebaceous gland lobules. The sebaceous lobules showed more intense staining in areas close to the duct. The epithelial BMZ of the following tissues also reacted with RN delta 1A: cornea, ocular conjunctiva, buccal mucosa, upper oesophagus, placenta (amnion placentum), umbilical cord and transitional epithelium of the bladder. The epithelium of the jejunum and ovary failed to react with RN delta 1A. Staining of the BCCs and SCCs was variable. Five of six nodular BCCs showed some anti-BP180 staining at the tumour-stromal interface, although the level of staining was less intense than that observed in the overlying normal epidermis. All three morphoeic BCCs analysed in this investigation did not show any staining with RN delta 1A. Three of four SCCs showed weak staining at the tumour-stromal interface. Thus, the tissue distribution of BP180 paralleled that of hemidesmosomes, and expression of this protein was found to be decreased or absent in cutaneous neoplasms.

The role of complement in experimental bullous pemphigoid

Bullous pemphigoid (BP) is a blistering skin disease associated with an IgG autoimmune response directed against the ectodomain of the hemidesmosomal protein, BP180. An animal model of BP has recently been developed by our laboratory based on the passive transfer of rabbit antimurine BP180 antibodies into neonatal BALB/c mice. The experimental animals develop a blistering disease that reproduces all of the key immunopathological features of BP. In the present study we have investigated the role of complement in the pathogenesis of subepidermal blistering in the mouse model of BP. We demonstrate the following. (a) Rabbit anti-murine-BP180 IgG was effective in inducing cutaneous blisters in a C5-sufficient mouse strain, but failed to induce disease in the syngeneic C5-deficient strain; (b) neonatal BALB/c mice, pretreated with cobra venom factor to deplete complement, became resistant to the pathogenic effects of the anti-BP180 IgG; (c) F(ab')2 fragments generated from the anti-BP180 IgG exhibited no pathogenic activity in the mouse model; and (d) histologic evaluation of the skin of mice described in points b and c above showed minimal or no neutrophilic cell infiltration in the upper dermis. Thus, anti-BP180 antibodies trigger subepidermal blistering in this BP model via complement activation. This experimental model of BP should greatly facilitate future studies on the pathophysiology of autoantibody-mediated diseases of the dermal-epidermal junction.

Pemphigus foliaceus and pemphigus vulgaris autoantibodies react with the extracellular domain of desmoglein-1

Pemphigus foliaceus is associated with an autoimmune response against desmoglein-1; however, the fine specificity of these autoantibodies and the role that they play in pathogenesis have not yet been elucidated. In an attempt to develop a system to facilitate the detection and characterization of this antigen/antibody system, recombinant human desmoglein-1 was expressed in COS-1 cells, a mammalian epithelial cell line. The desmoglein-1 transgene product was shown to be expressed on the surface of the COS-1 cells in the appropriate transmembrane orientation. All pemphigus foliaceus sera (endemic form, n = 24; nonendemic form, n = 7) reacted strongly with nonpermeabilized desmoglein-1-transfected cells, exhibiting a punctate cell-surface staining pattern. This reactivity against the desmoglein-1 ectodomain was predominantly an IgG4-restricted response and was calcium dependent. Ten of 18 pemphigus vulgaris sera also reacted with the extra-cellular domain of recombinant desmoglein-1. Use of this eukaryotic expression system should greatly facilitate further characterization of the anti-desmoglein-1 autoimmune response associated with pemphigus foliaceus and pemphigus vulgaris and may aid in determining its pathogenic relevance.

Management errors leading to unnecessary hospitalization for kerion

OBJECTIVE

Tinea capitis is a common problem in the inner city, outpatient population. It is known that some children were being admitted for treatment of the kerion type of tinea capitis. The purpose of this study was to determine why these children were being admitted and whether hospitalization was justified.

DESIGN

A retrospective study of all children hospitalized at Children's Hospital of Wisconsin between January 1990 and December 1992 with the diagnosis of tinea capitis was performed.

RESULTS

Twenty-nine children who were hospitalized with tinea capitis were identified. In 10 cases, tinea capitis was the primary reason for admission, in 19 patients it was a secondary diagnosis. All of the patients with a primary diagnosis of tinea capitis were presumed to have a secondary bacterial infection of the kerion; however, this was not verified by the workup of any patient. Numerous deviations from optimal treatment were noted in both groups of patients. Although tinea capitis had been correctly diagnosed before admission in seven primary tinea capitis patients, only two of these patients received oral griseofulvin. The patients in whom tinea capitis was a secondary diagnosis also had a number of therapeutic deficiencies including failure to prescribe griseofulvin (16%), failure to administer griseofulvin with a fatty food or meal (58%), and failure to prescribe a sporicidal shampoo (63%).

CONCLUSIONS

Although all patients were assumed to have a secondary bacterial infection, this could not be documented. With the possible exception of one patient all the symptoms described by the patients could be explained by the highly inflammatory nature of a kerion. A better understanding of the degree of inflammation that may accompany a kerion, as well as its proper treatment, may prevent unnecessary hospitalization of children.

Development of an ELISA to detect anti-BP180 autoantibodies in bullous pemphigoid and herpes gestationis

Autoantibodies associated with the subepidermal blistering disorders bullous pemphigoid and herpes gestationis react with a 180-kD transmembrane hemidesmosomal protein, designated BP180. The BP180 ectodomain is composed of a series of interrupted collagen triple helical domains. Located on one of the noncollagenous extracellular segments of this protein is an immunodominant epitope, designated MCW-1, recognized by patient autoantibodies. In this investigation we have developed an enzyme-linked immunosorbent assay system to detect antibody reactivity against the MCW-1 epitope with the use of a bacterial fusion protein containing the BP180 autoantibody-reactive site. The following sera were assayed for reactivity with this recombinant protein: bullous pemphigoid (n = 62), herpes gestationis (n = 28), endemic pemphigus foliaceus (n = 17), lupus erythematosus (n = 15), and normal human sera (n = 22). This enzyme-linked immunosorbent assay-based protocol was shown to be highly specific (98.3%) in detecting autoantibody activity in bullous pemphigoid and herpes gestationis patients. Fifty-three percent of bullous pemphigoid sera and 71% of herpes gestations sera, but none of the control sera, yielded positive results in this assay. Of the patient sera that were known to react with full-length BP180, almost all showed reactivity with the MCW-1 antigenic site of this protein. Autoantibodies detected in this assay were predominantly of the immunoglobulin G class. The results presented here lend support to the hypothesis that this well-defined antigen/antibody system may be relevant in pathogenesis.

A passive transfer model of the organ-specific autoimmune disease, bullous pemphigoid, using antibodies generated against the hemidesmosomal antigen, BP180

Subepidermal blistering associated with the human skin diseases bullous pemphigoid and herpes gestationis has been thought to be an IgG autoantibody-mediated process; however, previous attempts to demonstrate the pathogenicity of patient autoantibodies have been unsuccessful. An immunodominant and potentially pathogenic epitope associated with these blistering diseases has recently been mapped to the extracellular domain of a human epidermal antigen, BP180. Patient autoantibodies that react with this well-defined antigenic site failed to crossreact with the murine form of this autoantigen and thus could not be assayed for pathogenicity in a conventional passive transfer mouse model. As an alternative, rabbit polyclonal antibodies were generated against a segment of the murine BP180 protein homologous with the human BP180 autoantibody-reactive site and were passively transferred into neonatal BALB/c mice. The injected animals developed a subepidermal blistering disease that closely mimicked bullous pemphigoid and herpes gestationis at the clinical, histological, and immunological levels. Autoantibodies that recognize the human BP180 ectodomain are therefore likely to play an initiatory role in the pathogenesis of bullous pemphigoid and herpes gestationis.

Calcium metabolism and the pathogenesis of dermatologic disease

Calcium has a major role in regulating epidermal functions, including cell proliferation, terminal differentiation, and cell-to-cell adhesion. Aberrations in calcium regulation have been noted in psoriasis when levels of the calcium binding protein calmodulin are elevated, and the normal calcium gradient within the epidermis is altered. Calcium may also be important in neoplasia because similar elevations in calmodulin have been noted in transformed cells. The function of calcium in mediating cell-cell adhesion may be important in understanding the acantholysis observed in pemphigus. The pemphigus foliaceus antigen appears to contain a calcium-sensitive epitope, and in pemphigus vulgaris, alteration in the function of calcium-sensitive cadherins may play a role in the production of acantholysis. Further understanding of the function of calcium in these processes may, in the future, allow us to alter calcium metabolism as a therapeutic intervention.

Characterization of keratocalmin, a calmodulin-binding protein from human epidermis

Using affinity-purified calmodulin-binding proteins from human epidermis we have developed a monoclonal IgM antibody, ROC 129.1, to a human desmosomal calcmodulin-binding protein. This antibody reacts with a submembranous 250-kD protein from human keratinocytes and stains human epidermis in a "cell-surface pattern". Permeability studies indicated that the epitope with which this monoclonal reacts is on the inner surface of the cell membrane. Immunoelectronmicroscopy localized the antigen to the desmosome. The epitope is restricted to stratified squamous epithelia and arises between 8-12 wk of fetal development. This desmosomal calmodulin-binding protein, which we have termed keratocalmin, may be involved in the calcium-regulated assembly of desmosomes.

Intracellular targets of cyclosporine

Since cyclosporine was first reported to improve psoriasis, investigators have been trying to determine its mechanism of action. In addition to the well-documented effects on cytokine production by T lymphocytes, a direct effect on keratinocytes has been proposed. Cyclophilin and calmodulin, two proteins that are present in both lymphocytes and keratinocytes, have been considered as possible intracellular targets for cyclosporine. Cyclophilin binds cyclosporine with high affinity and the ability to bind cyclophilin correlates with the immunosuppressive effects of cyclosporine analogs. Cyclophilin is identical to peptidyl-prolyl cis-trans isomerase, an enzyme that catalyzes refolding of proteins. The process of protein folding may be important in DNA-protein and protein-protein interactions. Calmodulin is an intracellular calcium-binding protein that is important in the regulation of cell proliferation. Cyclosporine binds to calmodulin with low affinity, and such binding of cyclosporine isomers does not reflect their immunosuppressive activity. The physiologic importance of calmodulin-to-cyclosporine binding is controversial.

Effect of ciclosporin A on epidermal keratinocytes in vitro: lack of a direct effect on calmodulin

Calmodulin, a major calcium-binding protein, is important in the regulation of cell proliferation. In human keratinocytes we found that culture confluence was accompanied by a decrease in calmodulin content. Ciclosporin A, 1-10 micrograms/ml, was found to inhibit the proliferation of the cells but did not affect their calmodulin content as measured by bioassay or radioimmunoassay.

Monoclonal antibody to a 35 kD epidermal protein induces cell detachment

A murine monoclonal antibody (ECS-1) was prepared from BALB/c mice immunized with trypsinized cultured human foreskin keratinocytes. The antibody showed a pattern suggestive of intercellular staining on the nucleated layers of normal human epidermis, adult palm, mouse lip epidermis, and cultured human keratinocytes. ECS-1 stained human fetal skin by 9 weeks estimated gestational age. ECS-1 reacted with a 35 kD protein extracted from neonatal foreskin epidermis and cultured human keratinocytes. The protein required Nonidet P-40 or sodium dodecyl sulfate and mercaptoethanol for solubilization. ECS-1 induced epidermal cell detachment which was enhanced by complement. ECS-1 shares characteristics with human pemphigus antibodies.

Increased prostaglandin synthesis by low calcium-regulated keratinocytes

The effect of calcium concentration on the in vitro prostaglandin production by murine keratinocytes was studied using radioimmunoassay. Keratinocytes grown in low-calcium medium (0.02 mM) maintained intracellular calcium levels adequate for arachidonic acid metabolism and actually showed increased prostaglandin production. Baseline, unstimulated PGE2 production was 4.5 times higher in cells growing in low- compared to normal-calcium (1.2 mM) medium (p = 0.001). PGF2 alpha production was increased 2.5 times in the low-calcium cells (p = 0.002). The calcium ionophore A23187 and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) exhibited differing calcium requirements for activation of the arachidonic acid pathway. A23187 ionophore stimulated prostaglandin synthesis only in cells growing in normal-calcium medium while TPA stimulated prostaglandin production by both low- and normal-calcium cells. Paradoxically, short-term exposure of low calcium-grown cells to normal-calcium medium abolished the TPA effect. These results suggested that calcium can control arachidonic acid metabolism at a number of regulatory points.