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

Ultrastructural and immunohistochemical characterization of basal cells in three-dimensional culture models of the skin

Keratinocytes were cultured on fibroblast-free dermal substitutes made of type I collagen film (collagen dermal substitute) and an extracellular matrix gel film (matrix dermal substitute), each of which was laid on a lyophilized type I collagen sponge. The morphology of the basal keratinocytes in these three-dimensional culture models of the skin was studied ultrastructurally and immunohistochemically to assess their differentiation to basal cells. The basal keratinocytes in the artificial epidermis cultured on the collagen dermal substitute showed poorly organized tonofibril networks and desmosomes. Neither the tonofibril-hemidesmosome complex nor the lamina densa were detected along the interface, where many cytoplasmic projections of basal keratinocytes were noted. There were no detectable antigens of type IV or VII collagen, LDA-1, or laminin in the interface. Bullous pemphigoid (BP) and 1-2B7B antigens and integrins were expressed along the cytoplasmic membrane and the projections of the basal keratinocytes. A high molecular weight keratin (keratin 1, 68 kDa, 34 beta B4) was detected only in part of the uppermost layers of this artificial epidermis. In contrast, basal keratinocytes in the artificial epidermis on the matrix dermal substitute developed tonofibril networks radiating to desmosomes and hemidesmosomes, under which a primitive lamina densa was present. Basement membrane zone antigens, such as type IV and VII collagens, LDA-1 and laminin were noted along the interface as were 1-2B7B and BP antigens and integrins. Laminin and type VII collagen were also detected along or in the membrane of the endoplasmic reticulum of basal keratinocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel antigen of the dermal-epidermal junction defined by an anti-CD1b monoclonal antibody (NU-T2)

NU-T2 is a mouse monoclonal IgG1 antibody to the CD1b molecule, (cross-)reacting with an antigen of the dermal-epidermal junction (NU-T2 DEJ AG). Further immunohistochemical characterization of the NU-T2 DEJ AG showed it to display unique properties that differentiate it from other known antigens of the dermal-epidermal junction. Indeed, the NU-T2 DEJ AG is primate-specific and present only in epithelial basement membranes. In normal human skin it is expressed within the lowermost lamina lucida of the dermal-epidermal junction but not in the deep part of epidermal appendages nor in the deep part of epidermal appendages nor in the basement membrane of dermal vessels, smooth muscles or nerves. In diseases with intraepidermal or intradermal cleavage, NU-T2 reactivity was observed at the floor of the blister. In various skin specimens with a cleavage through the lamina lucida (NaCl--or dispase-split skin, bullous pemphigoid, junctional epidermolysis bullosa), NU-T2 immunoreactivity seemed reduced, being localized at the dermal side of the cleavage. These results suggest that the antigen recognized by NU-T2 is a novel component of the lamina lucida of the dermal-epidermal junction, that seems to be important for dermal-epidermal adhesion.

Epitopes for CD1a, CD1b, and CD1c antigens are differentially mapped on Langerhans cells, dermal dendritic cells, keratinocytes, and basement membrane zone in human skin

BACKGROUND

CD1 antigens are classified serologically into at least three groups, CD1a, CD1b, and CD1c, and many kinds of monoclonal antibodies are available for each subgroup of CD1 antigens. CD1a, CD1b, and CD1c antigens have been shown to be selectively and differentially expressed on epidermal Langerhans cells and dermal dendritic cells in normal human skin.

OBJECTIVE

The objective was to further delineate the localization of epitopes of CD1 antigens in human skin.

METHODS

We examined the immunoreactivity of 14 different CD1 antibodies (seven CD1a, five CD1b, and two CD1c antibodies) with the immunoperoxidase technique. We also studied the reactivity of NU-T2 (CD1b) antibody by immunogold electron microscopy.

RESULTS

The epitopes for CD1a, CD1b, and CD1c antigens were differentially mapped on epidermal Langerhans cells, dermal dendritic cells, keratinocytes, the luminal portion of eccrine gland ducts, and the basement membrane zone in human skin.

CONCLUSION

These CD1 antibodies may be useful to analyze the phenotypic alteration of immune and nonimmune cells in various skin diseases.

Lamina densa malformation involved in histogenesis of primary localized cutaneous amyloidosis

Skin lesions of lichenoid amyloidosis and macular amyloidosis were immunohistochemically investigated using five monoclonal antibodies against basement membrane zone (BMZ) components. A hemidesmosomal component did not contribute to amyloid deposits, but components of the lamina densa and anchoring fibrils were associated with amyloid deposits in the uppermost dermis. Immunoelectron microscopy revealed that these BMZ components were not only aggregated in the BMZ and dermis, but were also involved in the individual amyloid islets. The lamina densa was disrupted in the interface areas just above the amyloid deposits, where cytoplasm of the basal cells directly faced the aggregate of amyloid filaments. Aggregates of some BMZ components were continuous to the amyloid islets from the lamina densa area. These findings suggest that a lamina densa malformation is involved in amyloid production in the interface of the BMZ, and support the secretion theory rather than the fibrillar body theory of amyloidogenesis in these types of primary localized cutaneous amyloidosis.

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.

Human skin basement membrane-associated heparan sulphate proteoglycan: distinctive differences in ultrastructural localization as a function of developmental age

Recent studies have demonstrated that skin basement membrane components are expressed within the dermo-epidermal junction in an orderly sequence during human foetal development. We have investigated the ultrastructural localization of basement membrane-related antigens in human foetal skin at different developmental ages using two monoclonal antibodies to a well-characterized basement membrane-associated heparan sulphate proteoglycan. A series of foetal skin specimens (range, 54-142 gestational days) were examined using an immunoperoxidase immunoelectron microscopic technique. In specimens representing very early developmental ages, very diffuse immunoreaction products were detected. However, by approximately 76 gestational days, some accentuation of heparan sulphate proteoglycan was noted along the lamina densa, and by 142 gestational days, the distribution of heparan sulphate proteoglycan was identical to that observed in neonatal and adult human skin. These findings demonstrate that active remodelling of the dermo-epidermal junction occurs during at least the first two trimesters, and affects not only basement membrane-associated structures but also specific antigens.

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.

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.

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.

Ontogeny of structural components at the dermal-epidermal junction in human embryonic and fetal skin: the appearance of anchoring fibrils and type VII collagen

The ontogeny and composition of the dermal-epidermal junction (DEJ) in developing human embryonic and fetal skin was studied at progressive stages of gestation by immunofluorescence microscopy and immunocytochemistry using transmission electron microscopy (TEM). The DEJ of embryonic skin at 5 weeks estimated gestational age (EGA) was a simple basement membrane zone limited to the basal cell plasma membrane, lamina lucida, and lamina densa. A network of reticular collagen fibrils (reticular lamina) was deposited beneath the lamina densa by 6 weeks. Coincident with the onset of increased complexity in epidermal and dermal structure, at the time of the embryonic to fetal transition, the DEJ displayed additional components that were markers of maturation. At 7-8 weeks EGA, fine filamentous structures extended from the DEJ into the reticular lamina. By 9 weeks EGA hemidesmosomes and banded anchoring fibrils were recognizable, although distributed sparsely at the DEJ. With increasing gestational age, these structures displayed greater electron density and structural completeness. By the end of the first trimester, the DEJ appeared ultrastructurally similar to that of mature skin. Weak immunofluorescent labeling demonstrated the presence of type VII collagen at the DEJ by 8 weeks EGA. From 10-12 weeks EGA immunofluorescent labeling of the DEJ for type VII collagen was distinctly punctate, while immunoperoxidase labeling observed by TEM was linear, continuous, and sublamina densa in position. With ongoing gestation the immunofluorescent labeling became increasingly stronger at the DEJ. Thus, type VII collagen was present at the DEJ in the zone immediately beneath the lamina densa, before the appearance of mature anchoring fibrils but coordinate with the appearance of fine filamentous, unbanded structures, and appeared to increase with the development and accumulation of anchoring fibrils.

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.

Monoclonal antibody GB3, a new probe for the study of human basement membranes and hemidesmosomes

A monoclonal antibody, GB3, has been raised against human amnion. Not only does GB3 bind to amniotic basement membrane, but it also recognizes an antigenic structure expressed by epidermal as well as by some other human basement membranes. This antigen is synthesized (and excreted) by cultured normal human epidermal keratinocytes. It is expressed to a lesser extent by the A431 epidermoid carcinoma cell line, but is not expressed by the SV40 virus-transformed SVK14 keratinocyte cell line. In ultrastructural studies, this antigen was located in the epidermal basement membrane, both in the lamina densa and in the lamina lucida, associated with hemidesmosomes. It was identified as a protein by in vitro proteolytic cleavage studies. The radio-immunoprecipitates from cultured human keratinocytes, analysed by SDS-PAGE, showed that GB3 recognized five polypeptides of 93.5, 125, 130, 146 and 150 kD under reducing conditions. They were probably linked by disulfide bonds. The tissue distribution of the antigen and the molecular weights (MWs) of its constitutive polypeptides suggest that it is different from other known components of basement membranes. It may provide a biochemical marker for hemidesmosomes. Furthermore, GB3 represents an interesting and original clinical probe, since the antigenic structure recognized by GB3 is lacking in Junctional Epidermolysis Bullosa, a lethal genodermatosis in which a dermo-epidermal splitting occurs at the level of lamina lucida.