DNA-dependent protein kinase is one of a subset of autoantigens specifically cleaved early during apoptosis.

Proteolytic cleavage of key substrates appears to be an important biochemical mechanism underlying the apoptotic process, and the centrality of interleukin 1 beta-converting enzyme (ICE)-like proteases as mediators of apoptosis has been suggested. The identification of the relevant substrates of the ICE protease family during apoptosis therefore constitutes a major challenge. Using human autoantibodies, we demonstrate here that a subset of autoantigens is specifically cleaved early during apoptosis. One of these cleaved molecules is identified as the catalytic subunit of the DNA-dependent protein kinase. The time courses of all proteolytic cleavages are identical and coincide with the onset of morphologic apoptosis. Furthermore, all cleavages share the same inhibition characteristics, which implicate an ICE-like activity(ies). We propose that cleavage of these autoantigens targets these molecules for an autoimmune response by revealing immunocryptic fragments in a proimmune apoptotic setting. Study of the immunogenicity of these fragments may yield insights into the autoimmune targeting of molecules. Moreover, the autoantibodies described will be valuable tools for the elucidation of mechanistically important proteolytic steps along the apoptotic pathway.

Autoantibodies to desmoplakin I and II in patients with erythema multiforme.

Erythema multiforme (EM) represents a syndrome of chronic recurrent inflammatory skin disease. Depending on the severity and extent of skin and mucosal involvement, it is defined either as EM minor or EM major. In this study we demonstrate the presence of autoantibodies (aAbs) against desmoplakin I and II, two major proteins of the desmosomal plaque, in six of six patients with the severe variant of EM, EM major. Light microscopic studies of lesional skin and mucous membranes localized in vivo bound immunoglobulin G (IgG) in a dotted desmosomal pattern along the cytoplasmic membranes of keratinocytes. By immunoelectronmicroscopy, in vivo bound IgG was confined to the desmosomal plaques. These findings were confirmed by indirect immunolocalization studies that demonstrated the presence of IgG aAbs in the serum of patients during active disease. These aAbs did not only bind to desmosomal plaques of epithelial cells where they colocalized with defined murine monoclonal antibodies directed against desmoplakin I and II, but also labeled the intercalated discs of myocardial cells. Biochemical characterization of circulating IgG aAbs revealed desmoplakin I and II as actual target autoantigens. By passive transfer of serum into newborn mice, in vivo binding of serum aAbs to keratinocytes was shown. The findings presented in this study imply a humoral immune response in certain patients with EM major and indicate a potential pathogenetic role of aAbs against desmoplakin I and II in this disease.

Efficacy of intravenous immunoglobulin (IVIG) affinity-purified anti-desmoglein anti-idiotypic antibodies in the treatment of an experimental model of pemphigus vulgaris.

Pemphigus vulgaris is a rare life-threatening autoimmune bullous disease caused by immunoglobulin G (IgG) autoantibodies directed against desmogleins 1 and 3. Previously, we showed that intravenous immunoglobulin (IVIG) ameliorates anti-desmoglein-induced experimental pemphigus vulgaris in newborn naive mice. The aim of this study was to examine the efficacy of anti-anti-desmoglein-specific IVIG in a similar model. Pemphigus-vulgaris-specific IVIG (PV-sIVIG) was affinity-purified from IVIG on a column of single-chain variable fragment (scFv) anti-desmogleins 1 and 3. The anti-idiotypic activity of PV-sIVIG was confirmed by enzyme-linked immunosorbent assay, inhibition assay. After induction of pemphigus by injection of anti-desmogleins 1 and 3 scFv to newborn mice, the animals were treated with PV-sIVIG, IVIG (low or high dose) or IgG from a healthy donor (n = 10 each). The skin was examined 24-48 h later, and samples of affected areas were analysed by histology and immunofluorescence. In vitro study showed that PV-sIVIG significantly inhibited anti-desmogleins 1 and 3 scFv binding to recombinant desmoglein-3 in a dose-dependent manner. Specificity was confirmed by inhibition assay. In vivo analysis revealed cutaneous lesions of pemphigus vulgaris in mice injected with normal IgG (nine of 10 mice) or low-dose IVIG (nine of 10 mice), but not in mice treated with PV-sIVIG (none of 10) or high-dose IVIG (none of 10). On immunopathological study, PV-sIVIG and regular IVIG prevented the formation of acantholysis and deposition of IgG in intercellular spaces. In conclusion, the PV-sIVIG preparation is more effective than native IVIG in inhibiting anti-desmoglein-induced pemphigus vulgaris in mice and might serve as a future therapy in patients with the clinical disease.

Antibodies against desmoglein 3 (pemphigus vulgaris antigen) are present in sera from patients with paraneoplastic pemphigus and cause acantholysis in vivo in neonatal mice.

Paraneoplastic pemphigus (PNP) is an autoimmune blistering disease that occurs in association with underlying neoplasms. Patients with PNP develop characteristic IgG autoantibodies directed against multiple antigens, most of which have been identified as cytoplasmic proteins of the plakin family (desmoplakin I, II, BPAG1, envoplakin, and periplakin). This study identified cell surface target antigens of PNP. We focused on desmoglein (Dsg) 3 and Dsg1, the autoantigens of pemphigus vulgaris and pemphigus foliaceus. ELISA using baculovirus-expressed recombinant Dsgs (rDsg3, rDsg1) has revealed that 25 out of 25 PNP sera tested were positive against Dsg3 and 16 of 25 were positive against Dsg1. All of 12 PNP sera tested immunoprecipitated Dsg3. Removal of anti-Dsg3 autoantibodies by immunoadsorption was sufficient to eliminate the ability of PNP sera to induce cutaneous blisters in neonatal mice in vivo. Furthermore, anti-Dsg3-specific antibodies that were affinity purified from PNP sera were proven to be pathogenic and caused blisters in neonatal mice. These findings indicate that Dsg3 and Dsg1 are the cell surface target antigens in PNP and that IgG autoantibodies against Dsg3 in PNP sera play a pathogenic role in inducing loss of cell adhesion of keratinocytes and causing blister formation.

Herpes gestationis autoantibodies recognize a 180-kD human epidermal antigen.

Herpes gestationis (HG) is a putative autoimmune bullous dermatosis of pregnancy which shares many findings with bullous pemphigoid (BP), a disease of the elderly. This study identifies for the first time the antigen detected by HG autoantibodies and compares it with that recognized by BP autoantibodies. Sera from 16 HG and 17 BP patients, and from normal pregnant women were evaluated by immunofluorescent (IF) studies and immunoblotted against human epidermal extracts. 89% of HG sera with circulating antibodies by IF recognized a 180-kD protein by immunoblotting. 71% of BP sera recognized a 240-kD band, but 47% detected a 180-kD protein that comigrated with the antigen detected by HG sera. None of the control sera recognized any specific bands. These findings suggest that the 180-kD epidermal protein may be the antigen detected by the HG factor and they also define immunologic similarities between HG and BP.

Pathogenic effects of bullous pemphigoid autoantibodies on rabbit corneal epithelium.

Bullous pemphigoid (BP) is associated with circulating autoantibodies reactive with an antigen(s) of the basement membrane zone (BMZ) of skin and mucosae. The pathogenicity of these autoantibodies, although suspected, is unconfirmed. We have investigated the effects of BP autoantibodies on a closely related tissue, the corneal epithelium of the rabbit. IgG fractions from the sera of seven patients with BP were purified by (a) ammonium sulfate precipitation, (b) ion exchange chromatography, or (c) gel filtration. Control IgG was prepared by ion exchange chromatography of pooled normal human gamma globulins. 32 rabbits received corneal intrastromal injections of BP IgG fractions (50 microliter, 0.95-2.05 mg total dose) in one eye, and control IgG (50 microliter, 1.8 mg) in the contralateral cornea. 28 of 32 BP IgG injections produced corneal inflammatory lesions, 10 of which developed visible blisters. Histologically, lesions showed polymorphonuclear cells clustering along the BMZ, and subepithelial blister formation. Immunofluorescence showed in vivo bound IgG and C3 at the BMZ. The intensity of inflammation was dose dependent and correlated often with in vitro complement fixation titers of the fractions. None of 32 corneas injected with control IgG became inflamed. BP IgG fractions injected intradermally into the ear skin of rabbits failed to produce inflammation. This may be due to slow clearance of IgG in the cornea, and optimal binding by the corneal epithelium. The intracorneal injections of BP IgG reproduce the clinical, histological, and immunological features of BP. This study provides evidence that BP autoantibodies are pathogenic.

Isolation of a human epidermal cDNA corresponding to the 180-kD autoantigen recognized by bullous pemphigoid and herpes gestationis sera. Immunolocalization of this protein to the hemidesmosome.

Autoantibodies present in the sera of patients with bullous pemphigoid (BP) bind to the basement membrane zone of normal human skin and commonly recognize two epidermal proteins, the BP240 and BP180 antigens. Two BP antigen cDNA clones from a lambda gt11 human keratinocyte library have been identified on the basis of reactivity with a BP serum. The fusion protein (FP) produced by one clone immunoadsorbed autoantibodies, which specifically recognized the BP180 by antigen, showing no cross-reactivity with BP240 by immunoblot analysis. The FP produced by the second clone immunoadsorbed autoantibodies which specifically reacted with the BP240 epidermal antigen. Northern blot analysis demonstrated that the BP180 and BP240 antigens are encoded by distinct RNA transcripts with lengths of 6.0 and 8.5 kb, respectively. Immunoblot analysis of the BP180 lysogen extract identified a 135-kD FP which was recognized by 7 of 16 BP sera and 7 of 8 herpes gestationis sera. A rabbit antiserum prepared against the lysogenic BP180 FP specifically recognized the BP180 antigen from human epidermal extracts by immunoblotting, labeled the BMZ by indirect immunofluorescence, and bound to human epidermal hemidesmosomes by immuno-electron microscopy. These results indicate that the BP180 antigen recognized by BP and herpes gestationis autoantibodies is a unique hemidesmosomal polypeptide, distinguishable from the BP240 antigen.

Human autoantibodies against desmoplakins in paraneoplastic pemphigus.

Recently, a previously unrecognized autoantibody mediated blistering disease, paraneoplastic pemphigus has been described. Paraneoplastic pemphigus is associated with lymphoid malignancies, thymomas, and poorly differentiated sarcomas. Serum of affected patients contain pathogenic autoantibodies that immunoprecipitate from normal keratinocytes a characteristic complex of four polypeptides with M(r) of 250, 230, 210, and 190 kD. As our preliminary studies indicated that the 250-kD and the 210-kD antigens comigrated with desmoplakins I and II, we investigated the possibility that autoantibodies against the desmoplakins were a component of this autoimmune syndrome. 11 sera from affected patients were tested by indirect immunofluorescence against desmosome containing tissues, immunoprecipitation of metabolically labeled keratinocytes, and Western immunoblotting of desmoplakins I and II that had been purified to homogeneity from pig tongue epithelium. By indirect immunofluorescence, 9 of 11 sera showed strong binding to epithelial and nonepithelial desmosomes, and 2 were weakly reactive. All 11 immunoprecipitated 250- and 210-kD bands of variable intensity that comigrated with bands identified by a murine monoclonal antidesmoplakin antibody, and immunoblotting confirmed binding of the serum autoantibodies to purified desmoplakins. This demonstrates that paraneoplastic pemphigus is the first human autoimmune syndrome in which autoantibodies against the desmoplakins are a prominent component of the humoral autoimmune response.

Bullous skin diseases.

Fundamental advances in the fields of molecular biology and immunology have facilitated investigation of the autoimmune blistering disorders. Recently, the use of human autoantibodies has helped to identify biologically important adhesion molecules of the skin, and the pathogenic mechanisms involved in bullous skin diseases are now being precisely defined.

Pernicious anemia and widespread absence of gastrointestinal endocrine cells in a patient with autoimmune polyglandular syndrome type I and malabsorption.

CONTEXT: Autoimmune polyglandular syndrome type I (APS I) is characterized by multiple endocrine gland failures, with other manifestations such as gastrointestinal (GI) symptoms. OBJECTIVE: The objective of the study was to study the histopathological and immunological findings in the GI mucosa of a patient with typical features of APS I, malabsorption, and pernicious anemia. DESIGN AND PATIENT: Biopsies from the GI tract of a patient with APS I were immunostained with chromogranin for GI endocrine cells (GIECs). Blinded slides were graded for numbers of endocrine cells. Normal gastric mucosa was exposed to the patient's serum to test for circulating anti-GIEC and antiparietal cell antibodies using indirect immunofluorescence. SETTING: The study was conducted at the Departments of Pediatrics and Medical Gastroenterology in an academic medical center. RESULTS: The patient's GI mucosa demonstrated absence of GIECs throughout, including gastric gastrin-secreting cells, and her laboratory tests for serum gastrin levels were low normal. Both GIECs and parietal cells were absent in her gastric corpus. The patient's serum contained anti-GIEC antibody but no antiparietal cell antibody. CONCLUSIONS: These observations suggest that GIECs in APS I are subject to an autoimmune destruction that can cause widespread GIEC loss. This could explain the GI dysfunctions that are often noted in the syndrome including malabsorption and atrophic gastric changes with pernicious anemia. We also hypothesize that absence of gastric parietal cells may result mainly from hypogastrinemia that is mainly the loss of gastrin-secreting cells rather than from immune-mediated destruction of parietal cells like that seen in the atrophic gastritis associated with adult-onset pernicious anemia.

Dry eye and dry mouth in the elderly: a population-based assessment.

BACKGROUND: Symptoms of dry eye and dry mouth are common in the elderly and are often debilitating. Previous research on small populations has been inconsistent regarding the contribution to sicca symptoms of autoimmune markers, medication use, and other factors. The objective of this study was to determine the population prevalence of symptoms of dry eye and dry mouth and to evaluate possible risk factors. METHODS: This is a population-based study of 2481 individuals, aged 65 to 84 years, residing in Salisbury, Md, and identified by the Health Care Financing Medicare database. The main outcome measures included information on sicca symptoms, medical history, medication use, and joint examination results collected in a standardized manner. Autoimmune status was assessed in 1200 individuals by measuring antinuclear antibody, rheumatoid factor, and autoantibodies to the soluble nuclear antigens Ro/SS-A and La/SS-B by double immunodiffusion. RESULTS: Approximately 27% of the population reported dry eye or dry mouth symptoms to be present often or all the time and 4.4% reported both. The prevalence of dry mouth (but not dry eye) symptoms increased with age, female sex, and white race. No association of sicca symptoms was found with rheumatoid arthritis, smoking, alcohol consumption, reproductive hormonal status, or the presence of autoantibodies. A strong, dose-response relationship was observed between sicca symptoms and the use of certain medication classes. The proportion of the population prevalence of sicca symptoms attributable to the use of drying medications was estimated at 62% for dry eye and dry mouth and 38% for dry eye or dry mouth symptoms. CONCLUSIONS: Sicca symptoms are common in the elderly, and medication side effects appear to be a major underlying factor. Our results do not indicate an association between autoimmune status and sicca symptoms and do not support immunologic testing in persons with sicca symptoms in the absence of other important systemic features.

Inhibition of cutaneous contact hypersensitivity by calcium transport inhibitors lanthanum and diltiazem.

Epidermal Langerhans cells (ELC) are bone marrow-derived immune cells that are important in allergic contact dermatitis. We examined the influence of calcium transport inhibitors, lanthanum and diltiazem hydrochloride, on allergic contact dermatitis induced by 1-chloro-2,4-dinitrobenzene (DNCB) in BALB/c mice. Systemic lanthanum at a dose of 0.08 mg/kg and topical lanthanum (50 microliters of 10% solution) were given 5 d before DNCB sensitization. Systemic diltiazem (30 mg/kg per dy) was given for 3 d during sensitization with DNCB. In all animals, challenge with topical DNCB to the ear skin was performed 5 d after sensitization and ear swelling was measured. Twenty four hours post-DNCB challenge, animals receiving systemic lanthanum demonstrated a 56% decrease in contact hypersensitivity (ear swelling) compared with non-lanthanum-treated animals (0.08 +/- 0.03 mm vs 0.18 mm +/- 0.02 mm, p less than 0.01). Topical lanthanum produced a 58% decrease in contact hypersensitivity (0.20 +/- 0.02 mm vs 0.41 +/- 0.03 mm, p less than 0.01). The DNCB-induced ear swelling also resolved more quickly in animals treated with lanthanum. Systemic diltiazem produced a 67% decrease in ear swelling (0.05 +/- 0.01 mm vs 0.15 +/- 0.02 mm, p less than 0.001). A decrease in epidermal Langerhans cell density of 13 to 14% was produced by systemic lanthanum, detected by both ATPase staining and Ia staining, respectively (p less than 0.05). Approximately 20% of the Langerhans cells were morphologically abnormal, having become "rounded," and lacking normal dendritic processes. From these results, we infer that calcium transport across the cell membrane of ELC may be important in the regulation of their function. Lanthanides and other calcium-channel blockers may be useful pharmacologic agents to probe these phenomena.

The calcium-sensitive epitope of pemphigus foliaceus antigen is present on a murine tryptic fragment and constitutes a major antigenic region for human autoantibodies.

Recent findings indicate that the pemphigus foliaceus (PF) antigen is involved in epidermal cell adhesion and that characteristic PF lesions result from loss of this function as a consequence of autoantibody binding. In the present communication we present data on the epitopes involved in the human autoantibody binding to an immunologically reactive murine tryptic fragment of the PF antigen (tf-PF). Immunoprecipitation experiments showed that 39 PF sera, obtained from North American, Colombian, and Brazilian patients recognized only calcium-sensitive epitope(s) on the tf-PF. Immunofluorescence blocking experiments showed that preincubation with tf-PF completely blocked the immunofluorescence of 80% of the sera when tested on human skin substrate, and 86% of the sera when tested on murine skin substrate. These results show that the calcium-sensitive epitope(s) originally recognized on human PF complex, is (are) present on the murine tf-PF and constitute(s) a major antigenic region for the human PF autoantibodies. They also implicate this region of the PF antigen in the pathogenesis of PF as well as in epidermal cell adhesion.

Ultrastructural studies of acantholysis induced in vivo by passive transfer of IgG from endemic pemphigus foliaceus (Fogo Selvagem).

Intraperitoneal (IP) injections of IgG from patients with Endemic Pemphigus Foliaceus [Fogo Selvagem (FS)] cause acantholysis in BALB/c mice (JID. 85:538, 1985). The dynamic ultrastructural changes of FS IgG-induced acantholysis in mice are the subject of this study. FS IgG was injected IP into neonatal BALB/c mice. Skin and serum was studied at 0, 1, 3, 6, 12, 18, and 24 h post injection by immunofluorescence (IF), electron microscopy (EM), and immuno-EM. Binding of FS IgG in the intercellular spaces (ICS) of the basal cell layer was seen by IF within 1 h and was strongest at 12 h. IgG binding affected the spinous and granular cell layer by 12 h, then faded and remain localized only in the basal cell layer at 24 h. By immuno-EM, IgG binding was diffuse along the keratinocyte surface. Edema of the ICS in the basal cell layer was present at 1 h by EM. At 12 h, there was microvillous formation with intact desmosomes at the tip of the projections. Splitting of desmosomes (forming half desmosomes) and acantholysis primarily affecting the granular cell layer were most prominent between 12 and 24 h. The plaques of the half desmosomes gradually disappeared and tonofilaments retracted into the cytoplasm. Detaching keratinocytes showed vacuolization, swollen mitochondria, and internalization of intact desmosomes and half desmosomes (remnants of split desmosomes). This investigation shows that the ultrastructural changes observed in the epidermis of patients with FS can be duplicated in experimental animals by IP injection of FS IgG. Further, FS IgG may have direct effects on the assembly/disassembly of desmosomes.

Purification of immunoprecipitated pemphigus foliaceus antigen fragment and its use in radioimmunoassay.

A major difficulty in biochemical studies of the pemphigus foliaceus (PF) antigen is the lack of a method for its quantitative determination. Immunofluorescence blocking and immunoprecipitation methods are semiquantitative and time consuming. Radioimmunoassay (RIA) methods are quantitative but they require pure and stable antigen preparations that have not been available for PF. The present investigation shows the further purification of a previously described preparation of PF antigen fragment obtained from trypsinization media of mouse skin (Con A Frn) and demonstrates its usefulness in a RIA method for quantitation of the antigen. The major contaminants of the 45-kD tryptic fragment of the PF antigen (tf-PF) in immunoprecipitates of the Con A Frn with PF sera were identified as H and L chains of murine IgG and mannose-binding lectins. The IgG contaminants could be removed by avoidance of blood contamination during preparation of the Con A Frn and/or pre-absorption of the Con A Frn with protein A Sepharose. The lectins could be removed by affinity chromatography of the Con A Frn on asialofetuin column and washing the immunoprecipitates with 0.2 M alpha-methyl-mannoside. Using the purified, labeled Con A Frn in RIA, we showed that standard curves could be established and the amounts of PF antigen could be determined in different extracts without the need for electrophoresis, autoradiography, or scanning. This RIA method is rapid and can be easily used to analyze many samples, e.g., chromatographic fractions and extracts made from different tissues.

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.

Inhibition of Langerhans cell ATPase and contact sensitization by lanthanides--role of T-suppressor cells.

Lanthanides are rare earths, elements 55-71 in the periodic table, that are of interest in biologic systems as isomorphic competitors for calcium binding sites. Lanthanides were tested for their inhibitory influence on the Ca++/Mg(++)-dependent ATPase of epidermal langerhans cells in vitro, and on the immunologic function of Langerhans cells in vivo. The trivalent ions of lanthanides, lanthanum, and cerium completely inhibited the ATPase staining of Langerhans cells in vitro. When mice were sensitized with dinitrofluorobenzene on skin sites pretreated with topical lanthanum chloride, and challenged on untreated ear skin, a markedly reduced contact hypersensitivity response was observed. This hyporesponsiveness was found to be antigen specific, and could be passively transferred to naive syngeneic animals recipients by CD4-CD8+ spleen cells. These results suggest that inhibition of the epidermal Langerhans cell surface ATPase by application of topical lanthanum and the induction of antigen-specific immunologic tolerance may be related events.

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.

No evidence of human herpesvirus 8 infection in patients with paraneoplastic pemphigus, pemphigus vulgaris, or pemphigus foliaceus.

Paraneoplastic pemphigus has been associated with both malignancies and multicentric Castleman's disease; the latter is a rare angiolymphoproliferative disorder that has also been linked with human herpesvirus 8 (HHV8) infection. Other diseases definitively associated with HHV8 include Kaposi's sarcoma and primary effusion lymphoma. In a search for additional HHV8-associated diseases, patients with paraneoplastic pemphigus, as well as patients with pemphigus vulgaris and pemphigus foliaceus, were studied. Using an immunofluorescence assay able to specifically detect antibodies directed against lytically induced HHV8 antigens, HHV8 antibodies were not detected in sera from 24 patients with paraneoplastic pemphigus (including 10 with concomitant Castleman's disease) nor from 19 patients with pemphigus vulgaris. Sera from patients with Kaposi's sarcoma and from healthy U.S. blood donors were positive (25 of 26) and negative (none of 20), respectively. In addition, HHV8 DNA was not found in frozen lesional skin of five patients with pemphigus vulgaris and five patients with pemphigus foliaceus by nested polymerase chain reaction (lower limit of detection = 10 copies viral DNA per microg total cellular DNA). Finally, tissue sections of lesional skin from 10 patients with pemphigus vulgaris were negative for HHV8 by in situ hybridization, using probes able to detect both latently and lytically expressed HHV8 genes in Kaposi's sarcoma tissue. In summary, no evidence of HHV8 infection was found in all types of pemphigus using a variety of methods. These findings do not support a general role for HHV8 in skin diseases associated with immunosuppression.