Cicatricial pemphigoid, bullous pemphigoid, and epidermolysis bullosa acquisita antigens: differences in organ and species specificities and localization in chemically-separated human skin of three basement membrane antigens

Remission of antiepiligrin (laminin-5) cicatricial pemphigoid after excision of gastric carcinoma

PURPOSE

To describe a case of antiepiligrin cicatricial pemphigoid with unusual ocular manifestations and its remission after surgical removal of gastric carcinoma.

METHODS

We describe a 61-year-old Japanese man with antiepiligrin cicatricial pemphigoid.

RESULTS

He presented with conjunctival injection and discharge preceded by a 6-month period of erosive lesions in the oral mucosa and the truncal skin. An advanced gastric carcinoma was found and his serum immunoprecipitated laminin-5. Despite topical treatment with betamethasone, ofloxacin, and artificial tear solutions, serious symblepharon along the Meibomian line developed with little shortening of the inferior conjunctival sac. Following radical gastrectomy, the ocular and cutaneous lesions turned completely quiet.

CONCLUSION

The present case differed from past cases by lacking inferior conjunctival sac shortening and by showing erosive lesions solely at the mucocutaneous junctions. The ocular involvement in this case correlated very well with the severity of gastric carcinoma.

Contemporary issues in the diagnosis of oral pemphigoid: a selective review of the literature

Pemphigoid is a group of bullous diseases that have a diversified morphologic presentation and affect the skin, oral mucosa, and other mucosal membranes, alone or in combination. In the literature, the condition has been subclassified into bullous pemphigoid and cicatricial pemphigoid (mucous membrane pemphigoid) on the basis of the primary organ of involvement. In addition to the clinical presentation and a subepithelial vesicle or bullae on routine histologic analysis, the diagnosis is based on direct and indirect immunofluorescence studies. Recent investigations indicate that different clinical groups of patients with pemphigoid produce autoantibodies to different molecules within the basement membrane zone. Based on these recent observations and a review of the literature, a viewpoint is presented that not all patients with cicatricial pemphigoid should be grouped together. Rather, they should be classified into subgroups-ocular, oral, etc-on the basis of the clinical phenotype and long-term follow-up. Such a division will facilitate the provision of appropriate and relevant treatment plans; if the clinical course changes, the diagnosis can be adjusted. This strategy will prevent patients with disease limited to the oral cavity from receiving systemic drugs or agents that may be more harmful than beneficial.

Characterization of the antibody response in oesophageal cicatricial pemphigoid

Cicatricial pemphigoid (CP) is a subepidermal, autoimmune bullous dermatosis. It is classified as a clinical subset of bullous pemphigoid (BP). However, it differs from BP in some significant ways: (i) in CP mucosal involvement with clinical scarring is prominent; (ii) there is a prominent IgA class antibody response alone or in addition to the IgG class antibody response; and (iii) there is a heterogeneous antibody response in CP, whereas in BP the majority of the antibodies are directed against a 180-kDa hemidesmosomal protein, bullous pemphigoid antigen 2 (BPAg2). Oesophageal involvement in CP is a rare, but often devastating manifestation. In this study we examined the humoral autoimmune response in oesophageal CP, in an attempt to characterize the autoantibody reactivity profile. We used direct and indirect immunofluorescence and Western immunoblotting using normal human skin and oesophagus substrates. We studied patient sera over time in order to search for evidence of epitope spreading in these patients. All patients had positive direct immunofluorescence of perilesional oesophageal epithelium. All patients had positive circulating antibasement membrane zone autoantibody titres. There was a significant IgA class in addition to an IgG class autoantibody response. IgA and IgG antibodies demonstrated significant reactivity with BPAg2 and the 97 kDa linear IgA disease antigen on Western immunoblot suggesting intraprotein epitope spreading. There was no evidence of interprotein epitope spreading over time. Our findings suggest that there is a heterogeneous antibody response in oesophageal CP with the predominant antigen being BPAg2.

Identification of a 168-kDa mucosal antigen in a subset of patients with cicatricial pemphigoid

This study describes the presence of antibodies in sera from patients with cicatricial pemphigoid specific for a 168-kDa antigen expressed by buccal mucosa. Six cicatricial pemphigoid sera unreactive, with epidermal or dermal proteins in immunoblot assay were tested on mucosal protein extracts. Four of these sera labeled a mucosal 168-kDa antigen (M168) under reducing conditions. An additional cicatricial pemphigoid serum with circulating antibodies to 180-kDa bullous pemphigoid antigen (BPAg2) also labeled M168. None of these cicatricial pemphigoid sera reacted with the alpha, beta, or gamma subunits of laminin-5. Nitrocellulose elution studies showed that the M168 antigen is a basement membrane antigen and labeled the epidermal side of salt-split skin. Immunoaffinity-purified anti-M168 antibodies did not bind to the 230-kDa bullous pemphigoid antigen (BPAg1) or to the 180-kDa BPAg2. None of the control sera from healthy individuals or from bullous pemphigoid, pemphigus vulgaris, or pemphigus foliaceus patients reacted with Ml68. This study demonstrates the specificity of some cicatricial pemphigoid sera against a 168-kDa antigen that is different from the laminin-5 subunits and shares no epitopes with the antigens of bullous pemphigoid (BPAg1, BPAg2) or the epidermolysis bullosa acquisita.

Acquired bullous diseases of childhood: re-evaluation of diagnosis by indirect immunofluorescence examination on 1 M NaCl split skin and immunoblotting

Acquired autoimmune bullous diseases of childhood are rare, and can be difficult to distinguish clinically. We have studied 12 children, with an initial diagnosis of bullous pemphigoid (BP) in eight patients, cicatricial pemphigoid (CP) in one, chronic bullous disease of childhood (CBDC) in one, and epidermolysis bullosa acquisita (EBA) in two. All patients had positive indirect immunofluorescence (IIF) of the BMZ with IgG. Using 1 M NaCl split skin, six patients showed epidermal binding of IgG, with additional IgA in three cases, and in five patients IgG antibodies bound a dermal protein. Immunoblotting studies revealed an antibody to type VII collagen (EBA antigen) in three patients who had a dermal pattern on IIF. Six sera reacted with an epidermal protein of 180 and/or 220 kDa, characteristic of BP and CP. One of the three IgA-positive sera detected 220- and 180-kDa epidermal proteins using anti-IgA antibody. Following these studies the diagnosis was changed in three of the children. The diagnosis of CBDC was changed to either BP or EBA because of the presence of circulating IgG autoantibodies. In two children with an initial diagnosis of BP the diagnosis was changed to EBA. We conclude that the clinical picture in bullous disorders of childhood shows considerable overlap, and is often misleading. Additional circulating IgA autoantibodies seem to be more common in BP than has been recognized previously. Indirect immunofluorescence investigation on 1 M NaCl split skin may be helpful in differentiating between BP and EBA, but does not replace immunoblotting studies. EBA is apparently more common in children than in adults. No difference was found between the children with BP and EBA with regard to the duration of disease. The long-term outlook is good, although the course may be protracted.

Immunofluorescence on split skin for the detection and differentiation of basement membrane zone autoantibodies

The autoimmune subepidermal bullous diseases are characterized by autoantibodies to the basement membrane zone of stratified squamous epithelium. Recent studies have shown that the antibodies have characteristic ultrastructural and antigenic binding properties and that differentiating between those properties can be useful in distinguishing one disease from another. Immunofluorescence microscopy is widely used to detect basement membrane zone autoantibodies. The test has traditionally used tissue substrates with an intact basement membrane zone. Those substrates are limited because autoantibody binding cannot always be detected and because autoantibodies with different ultrastructural and antigenic binding properties cannot be distinguished from each other. Normal human skin that has been separated through the basement membrane zone (i.e., split skin) has recently been used as a substrate for detecting and characterizing basement membrane zone autoantibodies by immunofluorescence. Studies indicate that split skin is a more sensitive substrate than intact skin for detecting the antibodies and that antibodies with different ultrastructural binding sites can often be differentiated from one another on split skin. Those studies suggest split skin is the substrate of choice for the routine immunofluorescence evaluation of autoimmune subepidermal bullous diseases.

A novel lamina lucida component of epithelial and endothelial basement membranes detected by LH39 monoclonal antibody

The murine monoclonal antibody, LH39 was characterized in this study and appeared to bind to a novel basement membrane epitope. This antigen was expressed in the epithelial basement membrane of human tissue derived from all three germ cell layers and in basement membranes surrounding small blood vessels within the stroma of all organs examined. LH39 antigen could be first detected in fetal skin at the dermo-epidermal junction at 7 weeks estimated gestational age but was not present in the dermal vasculature until 16 weeks. When tested against tissue from a range of lower mammalian species, LH39 antigen appeared to be primate-specific. The epithelial basement membrane zone in organotypical cultures, where there is de novo synthesis of basement membrane components, contained abundant LH39 antigen in contrast to other basement membrane components, type IV collagen, laminin, and type VII collagen. Ultrastructural localization of LH39 epitope, using immunogold electron microscopy on unfixed freshly frozen tissue, was to the lamina lucida. No cross-reactivity could be detected between LH39 and laminin, fibronectin, and collagens I, III, IV, and V using the ELISA assay. In vitro studies with a range of proteolytic enzymes suggested that the antigen was non-collagenous in nature. LH39 precipitated a polypeptide with a molecular weight of 185 kD from extracts of metabolically labelled cultured keratinocytes, and polypeptides of 185 and 200 kD from the culture medium. The tissue distribution of LH39 antigen suggested that it may be an epitope within anchoring filaments. Potential applications of this antibody include the study of benign and malignant human vascular disorders, diseases and tumours associated with angiogenesis, epithelial neoplasms, and conditions of tissue regeneration and repair, such as wound healing.

Structure and antigenicity of the skin basement membrane zone

The skin basement membrane zone is comprised of two major ultrastructural regions, four associated structures, and at least 17 different antigens. In this brief review, the ultrastructure, antigenicity, and ontogeny of normal human skin will be discussed in detail, as will alterations in expression or immune response to selected basement membrane components in specific mechanobullous and autoimmune diseases.

Cicatricial pemphigoid antigen differs from bullous pemphigoid antigen by its exclusive extracellular localization: a study by indirect immunoelectronmicroscopy

Several components of the dermal-epidermal junction (DEJ) bear the name of the autoimmune bullous disease in which they are involved. The epidermolysis bullosa acquisita (EBA) antigen, a component of anchoring fibrils, and the bullous pemphigoid (BP) antigen, a component of hemidesmosomes (HD) with a molecular weight of 220-240 kD, have been well characterized. In contrast, there is little data known about the cicatricial pemphigoid (CP) antigen. No differences between CP and BP have been reported when sera of patients were studied by Western immunoblotting. Findings of a study of sera from 8 patients with CP by indirect immunoelectron microscopy (IEM) on normal human skin are reported. Saponin (0.1% 10 mn) was used as a permeabilizing agent of cytomembranes and saponin-treated skin samples were compared to saponin-untreated skin samples. Four sera from patients with BP, one from a patient with EBA, and three from healthy donors served as controls. The CP sera produced a similar staining of DEJ on both saponin-treated and saponin-untreated skin samples: immune deposits were localized over the lamina densa and the lower part of the lamina lucida clearly separated from the cytoplasmic membrane of keratinocytes, in regularly spaced clumps. The BP sera produced an intense staining of DEJ only on saponin-treated skin samples: immune deposits were observed on the cytoplasmic attachment plaque of the HD; on saponin-untreated skin samples, BP sera produced only a faint staining of the extracellular part of HD. Finally, as expected the EBA serum appeared on the lower part of the lamina densa and anchoring fibrils, and no DAB deposits were observed with the serum of healthy donors. This data indicated that CP antigen is different than BP antigen by its exclusive extracellular localization. It may be a component of anchoring filaments.

Salt-split human skin substrate for the immunofluorescent screening of serum from patients with cicatricial pemphigoid and a new method of immunoprecipitation with IgA antibodies

In patients with cicatricial pemphigoid, immunoglobulins (usually IgG) and complement are deposited within the dermoepidermal junction and are detected by direct immunofluorescent staining of perilesional mucous membrane and/or skin with fluorescein-labeled antibodies to human immunoglobulins. Although rare, some patients also have circulating low-titer, anti-basement membrane zone autoantibodies. In this study, we report 11 patients with the clinical, histologic, and immunologic criteria for cicatricial pemphigoid who had circulating anti-BMZ autoantibodies as demonstrated by positive indirect staining of a normal human skin that had been fractured through the dermoepidermal junction by prolonged incubation in a cold, 1 mol/L sodium chloride solution. On this salt-split human skin substrate, 9 of the 11 patients (82%) had autoantibodies that bound to the epidermal roof, one serum stained only the dermal floor, and one serum stained both sides of the separation. The predominant class of immunoglobulin in the patients' sera that bound to the substrate was IgA; IgA was the single immunoglobulin in 55% and was associated with IgG in 18%. IgG was the only immunoglobulin detected in 27% of the cases. No specific protein was detected by either Western immunoblot or a new IgA immunoprecipitation procedure.

Immunoelectron microscopy and immunofluorescence antigenic mapping: diagnostic applications

In selected situations, direct and indirect IEM may provide important diagnostic information for the clinician, as pertains to the diagnosis and therefore prognosis in a given patient. As discussed, however, all of the more conventional approaches should be pursued before consideration is given to the performance of IEM, knowing its relative cost and technical difficulty. In contrast, we consider immunofluorescence antigenic mapping to be the diagnostic method of choice for the determination of the type of inherited EB present in affected individuals. When additional ultrastructural or morphometric data is required, then TEM can be performed as an adjunct study once it is determined by mapping technique that additional useful information may be derived.

Absence of type IV collagen in the centre of the corneal epithelial basement membrane

Type IV collagen is the basic structural component of all basement membranes (BM), and forms the backbone to which other BM components attach. We have found that in the centre of the adult human cornea the epithelium does not display a type IV collagen immunoreactive BM. In fetal corneas (14 and 22 weeks of gestation), however, the epithelial BM shows uninterrupted type IV collagen immunoreactivity. In similar experiments laminin immunoreactivity was observed in the entire corneal epithelial BM, in fetal as well as adult corneas. Ultrastructurally, a normal BM with a lamina lucida and a lamina densa can be observed in the conjunctiva. The adult corneal centre, however, shows epithelium without a lamina densa. Focal deposits of electron-dense material are observed in conjunction with hemidesmosomes and anchoring fibres. These observations indicate that in the development of the eye, the cornea is initially covered with an epithelium which attaches to a normal BM. Later on, however, the BM type IV collagen disappears from the corneal centre. Assuming that highly differentiated epithelium cannot produce a BM, this could be due to the high level of differentiation of central corneal epithelium, which is generated in the limbal proliferation zone. Alternatively, the acellular Bowman's layer might lack triggers to induce type IV collagen production by the epithelial cells.

Ultrastructural localization of the core protein of a basement membrane-specific chondroitin sulfate proteoglycan in adult rat skin

Basement membranes are complex extracellular matrices present at epithelial/mesenchymal interfaces of tissues. The dermal-epidermal junction has been shown to contain numerous components, some of the most well known being laminin, types IV and VII collagens, heparan sulfate proteoglycan, fibronectin, and entactin/nidogen. IN this paper we show, using core protein-specific antibodies, the presence of a newly described basement membrane-specific chondroitin sulfate proteoglycan at the epithelial/mesenchymal interface of adult rat skin. Ultrastructurally, this antigen was proven to reside primarily within the basal lamina, apparently concentrated in the lamina densa. In addition, some of the proteoglycan was also present beneath the lamina densa, associated with the reticular lamina collagen fibrils.

Tissue-specific distribution of a novel component of epithelial basement membranes

Monoclonal antibodies against basement membrane (BM) were generated using the matrix deposited by cultured rabbit corneal epithelial cells as immunogen. BM antibodies were identified by immunofluorescent staining of frozen tissue sections and of extracellular matrix of living cultured cells. BM localization was confirmed by immunoelectron microscopy. Antibody AE26 immunoprecipitates a 140,000 Mr component from radiolabeled corneal epithelial cells and recognizes this component plus a 95,000 Mr band on Western blots. The antigen resists extraction by high and low salt and by nonionic detergents, but is solubilized in 4 M urea/1% mercaptoethanol. On isoelectric focusing and nonequilibrium pH gradient gels, AE26 antigen migrates to the acidic region (pI less than 3). The molecule is destroyed by trypsin, but is insensitive to bacterial collagenase. In frozen tissue sections, AE26 stains only BM of stratified epithelia plus trachea, ureter, lung, and intestine, but no other epithelial or nonepithelial BM. AE26 antigen is detected on Western blots of cornea, skin, and lung extracts, but not liver, kidney, or muscle, indicating that this is not due to masking of the epitope. This tissue distribution is different from any previously described BM molecule. Although we have not ruled out the possibility that AE26 recognizes a modification or fragment of a known BM component (particularly entactin), the acidic pI, collagenase resistance, and unusual tissue specificity suggest that AE26 recognizes a new BM protein. The BM heterogeneity demonstrated by AE26 may play a structural role or provide positional signals to the overlying epithelium.

Studies of cicatricial pemphigoid autoantibodies using direct immunoelectron microscopy and immunoblot analysis

We studied 11 consecutive patients with classical cicatricial pemphigoid (CP) using direct immunoelectron microscopy (IEM) and Western immunoblotting analysis. Direct IEM performed in the skin or gingival mucosa revealed in all 11 CP patients that immunoglobulins and complement deposits were usually thick and discontinuous along the dermoepidermal junction, mostly localized on the lamina densa and occasionally in the lamina lucida. By direct IEM, the ultrastructural aspect in CP differs from the pattern observed in bullous pemphigoid (BP) and from that of chronic epidermolysis bullosa acquisita (EBA). Nine CP patients were studied by Western immunoblotting and, of these nine, only two had detectable anti-basement membrane zone (BMZ) antibodies by indirect immunofluorescence on salt-split skin. By immunoblotting performed on protein extracts of heat-separated epidermis, eight out of the nine CP sera specifically reacted with two protein bands of approximately 230-240 kD and 180 kD, similar to those recognized by BP sera in co-migration experiments. By immunoblotting on skin BMZ extracts, none of these nine CP sera recognized the 290-kD major polypeptide of EBA antigen. Taken together, these results suggest that, in CP, the target-antigen, as identified on immunoblots, is similar to BP antigen, but with an abnormal expression within the dermoepidermal junction of patients, which may in part explain the scarring course of the disease.

Entactin: ultrastructural localization of an ubiquitous basement membrane glycoprotein in mouse skin

Entactin is a recently described sulfated glycoprotein component of mouse endodermal cell-derived extracellular matrix and is present in a number of basement membranes. It has been ultrastructurally localized to both lamina densa and adjacent epithelial cell membranes in rodent kidney. In the present study, we have sought to determine the localization of entactin in mouse skin. Indirect immunofluorescence and immunoelectron microscopy (the latter via immunoperoxidase technique) were performed on both intact and NaCl-separated mouse skin, using a well-characterized IgG class entactin-specific rat x mouse monoclonal antibody. At the light microscopic level, entactin was present in all skin basement membranes. On NaCl-split skin, staining was noted solely on the dermal portion. At the electron microscopic level, in intact skin, entactin was primarily localized to the lamina densa and adjacent upper papillary dermis. However, smaller amounts of immunoreaction products were also detectable within the lamina lucida and in close apposition to overlying hemidesmosomes. In partially separated skin, immunoreactants were similarly noted above the level of the lamina densa. However, in completely separated areas, hemidesmosomal or cell membrane staining was no longer visible. We conclude that entactin is an ubiquitous component of mouse skin basement membranes. Similar to previous findings in rodent kidney, entactin is present in multiple regions of skin basement membrane, although its primary localization remains within and directly beneath the lamina densa.

The localization of the bullous pemphigoid and cicatricial pemphigoid antigens: direct and indirect immunofluorescence of suction blisters

The location of in vivo bound immunoreactants was studied in 37 patients with subepidermal blistering diseases by direct immunofluorescence (IMF) on suction blisters taken from uninvolved forearm skin. The patients studied included 18 with bullous pemphigoid (BP), nine with cicatricial pemphigoid (CP), three with acquired epidermolysis bullosa (EBA) and 7 hybrid cases. The patterns of IMF in the suction blisters were: BP, epidermal 1, dermal 1, combined 4, negative 12; CP, epidermal 1, dermal 2, negative 6; EBA, dermal 2, negative 1; and 'hybrid' patients, epidermal 3, negative 4. The different patterns of suction blister staining could not be correlated with the clinical features of the patients in respect of mucous membrane involvement, scars or milia or a history of skin fragility. Both BP and CP are probably heterogeneous in respect of their antigen specificity, and the two diseases cannot reliably be distinguished by the patterns of direct IMF on suction blisters. In addition, some individual patients with BP have more than one target antigen as indicated by a combined pattern of suction blister fluorescence. The lack of correlation between the pattern of suction blister fluorescence and the clinical features suggests that factors other than antigen specificity determine the clinical expression of subepidermal blistering diseases.

Detection and partial characterization of a midlamina lucida-hemidesmosome-associated antigen (19-DEJ-1) present within human skin

A murine anti-human monoclonal antibody (19-DEJ-1) has been produced that binds to basement membranes (BMs) of the dermoepidermal junction and arrector pili muscles but not to either dermal glandular or vascular BMs. 19-DEJ-1 also recognizes BMs underneath epithelia of buccal mucosa, tongue, esophagus, cervix, and cornea, and BMs surrounding smooth muscle in medium-sized vessels, placenta, uterus, and esophagus. When 16 human fetal skins (aged 54-142 gestational days) were examined, the antigen was first detected at 81 days. Using immunoperoxidase and immunogold staining techniques, indirect immunoelectron microscopy demonstrated localization of 19-DEJ-1 to the level of the midlamina lucida, directly underneath hemidesmosomes; absent staining was noted beneath melanocytes. 19-DEJ-1 antigen was detectable in unfixed A431 cells grown on coverslips. After radioincorporation of 35S-methionine into A431 cells, 19-DEJ-1 monoclonal antibody specifically precipitated 2.75% of the total radiolabeled proteoglycans produced in culture supernatant and isolated by anion exchange chromatography. On the basis of our present findings, we conclude that 19-DEJ-1 monoclonal antibody defines a unique primate-specific proteoglycan that is present within BMs along the epithelial-connective tissue interface and around smooth muscle in skin and other selected organs. Its unique ultrastructural localization suggests the possibility that 19-DEJ-1 may recognize an antigenic epitope of either anchoring filaments or alternatively, the subbasal dense plate.

Bullous pemphigoid and cicatricial pemphigoid: immunoblotting detection of involved autoantigens

Bullous pemphigoid (BP) and cicatricial pemphigoid (CP) are subepidermal bullous autoimmune diseases which have distinct clinical features but identical immunological status. In order to determine whether these diseases could be dissociated on the basis of qualitative differences in serum antibodies to basement membrane zone (BMZ) antigens, the reactivity of sera from 7 CP and 29 BP patients with proteins extracted from normal human epidermal sheets (containing most of the lamina lucida components) was analysed using immunoblotting and compared to that of 10 normal sera. 20 out of the 29 BP sera contained antibodies recognizing one or several protein(s) of 240, 200, 180 and 165 kD molecular weight (MW). Antibodies in 4 out 7 CP sera specifically reacted with one or two polypeptides of 240 and 120 kD MW. These data confirm the heterogeneity of BP antigens and show the presence in CP of a novel 120 kD MW polypeptide which is found only in CP but not in BP. Taken together these findings demonstrate that in BP and CP, autoantibodies are directed to both common and specific BMZ antigens, their physiopathological significance need to be understood.

Monoclonal antibodies to native basement membranes reveal heterogeneous immunoreactivity patterns

In this paper we describe the development of basement membrane (BM) reactive monoclonal antibodies (MA), by immunization of mice with intact denuded BM. The MA raised against denuded amniotic BM (clones 1052, 1053 and 1065) showed heterogeneous staining patterns. MA 1052 and 1053 reacted with epithelial BM of the epidermis and epidermal adnexa and furthermore with the epithelial alveolar BM in the lung and the superficial part of the epithelial BM in the gastrointestinal tract. MA 1065 showed immunoreactivity with the epithelial BM of epidermis and epidermal adnexa and the epithelial BM of trachea and oesophagus, and furthermore pericellular staining of the basal keratinocytes and basal corneal epithelial cells. MA 1087, raised against human glomerular BM, showed immunoreactivity with all BM, except the central epithelial BM in the cornea. The precise localization of the target epitopes in the BM was investigated on chemically cleaved human skin. Reactivity for the MA occurred predominantly in the BM lamina adherent to the dermis, suggesting that the target epitopes reside in the lamina densa and/or lamina fibroreticularis. We furthermore examined the nature of the epitopes by preincubation of tissue sections with various enzymes prior to immunohistochemistry. The reactivity of the target epitopes was not affected by bacterial collagenase, but after various protease treatments the reactivity disappeared, suggesting that the epitopes are not localized on the triple helical part of collagenous proteins.

Chondroitin-6-sulfate-containing proteoglycan: a new component of human skin dermoepidermal junction

A murine monoclonal antibody (3B3) has been produced with specificity for chondroitin-6-sulfate (C-6-S) and proven binding to rodent basement membranes, presumably detecting a population of C-6-S-containing proteoglycans. Utilizing this antibody, we sought to determine whether a basement membrane chondroitin sulfate proteoglycan is present in adult, neonatal, and/or fetal skin, and if present, its ultrastructural localization. Indirect immunofluorescence was performed on human adult, neonatal, and fetal skin. To detect the antigen, specimens were pretreated with chondroitinase ABC; absence of enzyme treatment served as negative control. Chondroitin sulfate proteoglycan was detectable in linear homogeneous array along the dermoepidermal junction and within vascular (and when present, adnexal) basement membranes in both adult and neonatal skin. In fetal skin, basement membrane staining was noted as early as 54 gestational days. Indirect immunoelectron microscopy and NaCl-split skin studies were performed to ultrastructurally localize the antigen; immune deposits were detectable within the lamina densa in chondroitinase-treated skin. These findings demonstrate that chondroitin sulfate proteoglycan is present within all skin basement membranes; that it is present in the region of the lamina densa; and that similar to some other ubiquitous basement membrane antigens, it is present early in the developing fetus.

LDA-1: a ubiquitous noncollagenous lamina densa component of basement membrane detected by monoclonal antibody technique

Using monoclonal antibody technology, a new basement membrane antigen, designated as LDA-1, has been identified. This antigen is expressed in all human tissues thus far examined; within skin it is detectable not only within the dermal-epidermal junction but also within dermal vascular and appendageal basement membranes. In addition to human skin, LDA-1 is also detectable within rabbit but not monkey, rat, mouse, guinea pig, or cow skin. This antigen has been ultrastructurally localized to the lamina densa and to a much lesser extent, the adjacent sublamina densa region. ELISA (enzyme-linked immunosorbent assay) revealed no cross-reactivity between LDA-1 and type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan. In vitro enzymatic studies suggest that LDA-1 is noncollagenous in nature.