Intra-epidermal retention of type VII collagen in a patient with recessive dystrophic epidermolysis bullosa

An infant born with severe blisters on the limbs, face, trunk, and oral mucosa was diagnosed by light and electron microscopy to have recessive dystrophic epidermolysis bullosa. Transmission electron microscopy showed that the basal lamina remained with the epidermis and that the floor of the blister was exposed collagen of the papillary dermis. No banded anchoring fibrils were observed along either the roof or the floor of the blister; however, small filamentous structures, possibly immature anchoring fibrils, extended down from the lamina densa along the blister roof. Some basal and suprabasal keratinocytes contained large vesicles filled with filamentous matrix of variable electron density. Immunofluorescent staining of skin for type VII collagen showed sparse and irregular staining of type VII collagen along the blister roof, and intense intracellular labeling for type VII collagen in clusters of epidermal cells in basal and suprabasal layers. Type VII collagen appeared to be synthesized by keratinocytes but not secreted.     

Ontogenesis of the basement membrane zone after grafting cultured human epithelium: a morphologic and immunoelectron microscopic study.

Sheets of cultured epithelial cells have been successfully used as autografts for the permanent coverage of patients with full-thickness burns and as allografts to stimulate the healing of chronic skin ulcers. The basement membrane zone (BMZ), composed of lamina lucida, lamina densa, and anchoring fibrils, plays a pivotal role in the firm adherence of the epidermis to the dermis. The present study describes the ultrastructural development during various stages of wound healing after resurfacing different wound areas by cultured epithelial grafts. For this purpose, biopsies were obtained from five patients 5 d to 4.5 years after resurfacing full-thickness burns with cultured autografts, and from five patients at various stages after treatment of excised tattoos and chronic skin ulcers with cultured allografts. One biopsy was taken from a spontaneously healed burn wound 30 years post-injury. Ultrathin sections were prepared for transmission and immunoelectron microscopy, using monoclonal antibodies against type IV and VII collagen. Findings were compared to controls of age- and site-matched normal skin. Eleven days after grafting, the first BMZ features had regenerated, including lamina lucida, a discontinuous lamina densa, hemidesmosomes, and sparse anchoring fibrils. The process of de novo synthesis of BMZ components had begun, and within 4 to 5 weeks complete reformation of BMZ was observed, including normal distribution of anchoring fibrils. Immunolabeling of type VII collagen was first observed upon the lower part of lamina densa at day 11 and steadily increased, reaching normal values 5 weeks after grafting. In contrast, gold deposition of type IV collagen upon lamina densa was strongly increased at day 19 compared to normal. This high expression reduced a little at 5 weeks, but remained high up to 30 years after injury. Long-term burn scars exhibited pseudopodia-like extensions of all basal cells, abundant anchoring fibrils, and an increased amount of arching anchoring fibrils. These features might compensate for the lack of proper rete ridges.     

Immunomapping of EBA sera to multiple epitopes on collagen VII: further evidence that anchoring fibrils originate and terminate in the lamina densa

Epidermolysis bullosa acquisita (EBA) is an autoimmune blistering disease with circulating antibodies to type VII collagen, a major component of anchoring fibrils located at the dermal-epidermal junction. The purpose of this study was to further confirm the ultrastructural organisation of anchoring fibrils and to assess the relationship between the clinical phenotype of EBA and target site of their autoantibodies on anchoring fibrils. We studied the ultrastructural binding site of circulating autoantibodies from two patients with atypical clinical features who predominantly presented with oral lesions, and compared this with two patients with clinically typical forms of EBA. Immunoblotting of whole dermal extracts showed labelling of 290-kDa bands consistent with that of type VII collagen as well as the non-collagenous (NC-1) domain fusion protein in three out of four patients' sera. Postembedding immunoelectron microscopy (IEM) using Lowicryl K11M embedded normal human skin and patients' sera demonstrated the majority of labelling within the lamina densa, not below the lamina densa. We conclude that EBA autoantibodies in these patient's sera bind to the NC-1 domain of collagen VII situated in the lamina densa of the epidermal basement membrane, regardless of the EBA clinical phenotype. This confirms the previous notion that anchoring fibrils originate and terminate in the lamina densa.     

The carboxyl-terminal domain of type VII collagen is present at the basement membrane in recessive dystrophic epidermolysis bullosa

Recent studies showing that type VII collagen is a component of anchoring fibrils suggests that the absence of anchoring fibrils in recessive dystrophic epidermolysis bullosa may be due to a defect in the synthesis, secretion, and deposition of type VII collagen. That hypothesis is further supported by recent studies suggesting that monoclonal antibodies to type VII collagen do not react with the basement membrane in most patients. To investigate further, we examined skin from 12 patients by electron microscopy and by immunohistology and immunoelectron microscopy using a concentrated and purified monoclonal antibody to the carboxy-terminal domain of Type VII collagen. Although anchoring fibrils were not detected by electron microscopy, the results of immunohistology showed definite, but reduced, binding of the monoclonal antibody to type VII collagen at the basement membrane in a linear pattern in 11 of 12 patients. By immunoelectron microscopy, reduced deposition of anti-type VII collagen antibody was detected beneath the lamina densa. The results of this study show that the carboxyl-terminal domain of type VII collagen is synthesized, secreted, and deposited at the basement membrane zone in 11 of 12 patients with recessive dystrophic epidermolysis bullosa and suggest that the absence of anchoring fibrils may be due either to deposition of abnormal type VII collagen, reduced levels of normal type VII collagen, defective assembly of type VII collagen into anchoring fibrils, or destruction of the collagenous domain of type VII collagen.     

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

Summary 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.     

Key role of heparan sulfate chains in assembly of anchoring complex at the dermal-epidermal junction

Epidermal basement membrane forms anchoring complex composed of hemidesmosomes, anchoring filaments, lamina densa and anchoring fibrils to link epidermis to dermis. However, the anchoring complex is rarely formed in skin equivalent models, probably because of degradation of extracellular matrix (ECM) proteins and heparan sulfate chains by matrix metalloproteinases (MMPs) and heparanase, respectively. To explore the roles of ECM proteins and heparan sulfate in anchoring complex assembly, we used specific inhibitors of MMPs and heparanase, and the formation of anchoring complex was analysed in terms of polarized deposition of collagen VII, BP180 and β4 integrin at the dermal-epidermal junction (DEJ) by means of immunohistochemistry and transmission electron microscopy (TEM). The deposition of collagen VII was polarized to the basal side by the addition of MMP inhibitor, and the staining intensity was increased by combined treatment with MMP inhibitor and heparanase inhibitor, which enhanced anchoring fibril formation as observed by TEM. BP180 was polarized to the basal side by heparanase inhibitor, which protects HS chains, but not by MMP inhibitor. MMP inhibitor improved the polarization of β4 integrin. Hemidesmosomes were formed in the presence of each inhibitor, as observed by TEM, and formation was greatly enhanced by the combined treatment. These findings suggest that heparan sulfate chains, in addition to ECM proteins at the DEJ, play an important role in the assembly of anchoring complex, especially hemidesmosomes and anchoring fibrils.     

Epidermolysis bullosa acquisita antigen and the carboxy terminus of type VII collagen have a common immunolocalization to anchoring fibrils and lamina densa of basement membrane

In this study a variety of immunoelectron microscopic methods were used to define the precise ultrastructural binding site of epidermolysis bullosa acquisita antibodies (EBA-Ab). We used two EBA sera which immunoblotted with the same skin-extracted protein as that labelled by a monoclonal antibody (LH7.2) which is known to react with the carboxy terminus of type VII collagen. Gold-conjugated antibodies were used in two different immunoelectron microscopic procedures to compare the labelling characteristics of EBA-Ab and LH7.2 in normal human skin. Antibody incubations were performed using ultra-thin cryosections of unfixed skin and thin slices of fresh skin (en bloc technique) before conventional fixation and embedding in Epon. Both methods showed similar labelling features for both EBA-Ab and LH7.2. With ultra-thin cryosections there was labelling of the lamina densa and an undefined component of the sublamina densa region. With the en bloc technique, labelling of dermal ends of anchoring fibrils and of amorphous material recently defined as 'anchoring plaques' was evident. There was no labelling of the central banded portions of anchoring fibrils. We conclude that EBA-Ag is localized to the dermal ends of anchoring fibrils in addition to the lamina densa and possibly anchoring plaques, and thus has the same distribution as the carboxy terminus of type VII collagen.     

Alterations of basement membrane zone in bullous and non-bullous variants of extragenital lichen sclerosus

The aim of the study was to compare alterations of various regions of the basement membrane zone (BMZ) in lichen sclerosus (LS) using laser scanning confocal microscopy. The study included three cases of bullous LS, one case of bullous LS that developed in the course of graft-versus-host disease (GVHD), and six cases of non-bullous LS. Three cases of morphea served as a control. Biopsies from patients' skin and control biopsies from normal human skin were cut into 30-microm thick slides and labeled with antibodies against beta4-intergin (lamina lucida marker), collagen IV, and the N-terminal end of collagen VII (lamina densa markers) and the C-terminal end of collagen VII (sublamina densa marker) using routine immunofluorescence (IF). Three-dimensional (3D) reconstruction of various regions of the BMZ showed a decrease in the number and size of the dermal papillae in LS and morphea as compared with normal skin. In LS numerous invaginations and holes were present in the BMZ at the level of the lamina lucida and lamina densa. Computer animation of 3D projections revealed that the thickness of the lamina densa observed under the light microscopy is an optical artifact dependent on periodical tortion of the lamina densa along its axis. Torsions and invaginations of the BMZ are equally responsible for the phenomenon of artificial reduplication of the lamina densa observed at the ultrastructural level. IF labeling with antibody against the N-terminal end of collagen VII disclosed the presence of a large hole (up to 25 microm) in the lamina densa and the presence of granular material in deep dermis suggestive of partial degradation of lamina densa at the level of anchoring fibers. An IF mapping study showed blister formation below the lamina densa in three patients with bullous LS, whereas in a case of LS associated with GVHD, a blister formed through the basal layer of the epidermis. In morphea, there was flattening of BMZ at the level of lamina lucida, lamina densa, and sublamina densa but the continuity of BMZ was preserved. Three-dimensional reconstruction of dermal-epidermal junction in LS revealed alterations of the BMZ, most pronounced at the level of the lamina densa and sublamina densa.     

Transient bullous dermolysis of the newborn

In a freshly induced blister from transient bullous dermolysis of the newborn, we found in epidermal basal cells structures similar to anchoring fibrils and lamina densa, often in combination. In the upper dermis, collagenolysis and phagocytosis of degenerated collagen fragments were observed. It is concluded that the stellate inclusions previously reported in this disease are prematurely assembled anchoring fibrils and lamina densa. A disturbance of delivery mechanism of precursor materials for anchoring fibrils and lamina densa may cause the deficiency of these structures which are essential for the integrity of dermo-epidermal adhesion. The presence of many normal anchoring fibrils and lamina densa in perilesional skin and their prompt degeneration after rupture of the inclusions previously led us to conclude that lytic enzymes are involved in the formation of blisters in this disease. The new finding of collagen phagocytosis in the lesional dermis seemed to support this contention.     

Scanning electron microscopy of the epidermal lamina densa in normal human skin.

The lamina densa of normal human epidermis was exposed by treatment with 1 M sodium chloride and was examined by high-power scanning electron microscopy before and after trypsinization. Localization of type IV collagen in the lamina densa was also studied by transmission and scanning immunoelectron microscopy. Before trypsinization, the surface of the lamina densa consisted of microridges and microvalleys. The microridges varied in height and were connected with each other. They were arranged in a concentric fashion around the tips of the dermal microprojections. At a higher magnification, the surface of the lamina densa was composed of densely packed cobblestone-like structures approximately 7-15 nm in size, between which were interspaces 4-11 nm wide. These structures expressed type IV collagen. After trypsinization, the lamina densa was found to be composed of microfilaments approximately 10 nm thick showing beaded appearances. These microfilaments exhibited the same cobblestone-like structures as the lamina densa surface. Observation of the torn lamina densa demonstrated anchoring fibrils and oxytalan fibers that were attached to the lamina densa itself. Another kind of filament about 7 nm thick linked the anchoring fibrils and the oxytalan fibers. Beneath the lamina densa was a network of fibers about 40-50 nm thick, which was composed of collagen fibers and possibly also elaunin fibers. In conclusion, this study revealed the detailed surface ultrastructure of the epidermal lamina densa and its underlying filamentous elements.     

Type VII collagen is expressed but anchoring fibrils are defective in dystrophic epidermolysis bullosa inversa

A patient with dystrophic epidermolysis bullosa inversa was studied using electron microscopy and indirect immunofluorescence using antibodies to matrix macromolecules of the dermoepidermal junction zone. There was splitting below the lamina densa with an apparently normal basement membrane, but a lack of intact anchoring fibrils and with a disarranged papillary connective tissue. Indirect immunofluorescence examination with antibodies to type VII collagen, the major structural protein of anchoring fibrils, showed a normal linear staining pattern. Synthesis of type VII collagen which is unable to form stable, resistant anchoring fibrils may be a distinct feature of this subtype of recessive dystrophic epidermolysis bullosa.     

Application and limitations of three-dimensional reconstruction of the epidermal-dermal junction using electron microscopy

BACKGROUND: Anchoring fibrils were initially described as the arch-like structures that extend from the lamina densa to the sub-lamina densa. Keene et al. proposed a model in which the anchoring fibrils bridge structures called "anchoring plaques", and thus the three-dimensional (3D) structure of the anchoring fibrils remains somewhat controversial. OBJECTIVE: The aim of this study is to elucidate the 3D structure of anchoring fibrils in the skin. METHODS: In the present study, we performed electron microscopic 3D reconstruction of the epidermal-dermal junction, including the anchoring fibrils and hemidesmosomes using a personal computer and NIH-image software. RESULTS: We obtained images showing that anchoring fibrils had both ends inserted into the lamina densa and that interstitial dermal collagen fibers passed through the loops of the anchoring fibrils. "Anchoring plaques" were not observed. Clear images of hemidesmosomal distribution were not obtained due to technical limitations. CONCLUSION: These results suggest that the loops of the anchoring fibrils are the most important primary structures that hold the dermal interstitial collagen fibers and bind the basement membrane to the dermis.     

The localization of target antigens and autoantibodies in linear IgA disease is variable: correlation of immunogold electron microscopy and immunoblotting

Linear IgA disease (LAD) of adults and children is a dapsone-responsive, autoimmune subepidermal blistering disease characterized by linear IgA deposits at the basement membrane zone (BMZ) of the skin and mucosa. Circulating IgA antibodies to BMZ components are often present. In this study we investigated the ultrastructural localization of the antigens and autoantibodies in six patients with LAD (five adults and one child). Using a direct postembedding immunogold electron microscopy (EM) technique, three different patterns of IgA antibody deposition were seen in the skin of four patients with LAD. The IgA deposits localized within the uppermost part of the lamina lucida and to the basal surface of the hemidesmosome in two patients, to the lamina lucida in one, and to the lamina densa in the fourth patient. Using an indirect immunogold EM technique and serum or purified blister fluid from two additional LAD patients, we showed that the serum autoantibodies of one patient bound to the hemidesmosome of the BMZ, while the autoantibodies in the blister fluid of the other patient bound to the lamina densa and sublamina densa including the anchoring fibrils in a labelling pattern similar to that of the monoclonal antibody (LH7.2) to collagen VII. All the autoantibodies binding to the hemidesmosome or lamina lucida recognized a protein in epidermal extracts of molecular weight 180 kDa or its breakdown product of 97 kDa, 200 kDa or 230 kDa. The antibodies binding to the lamina densa recognized proteins of 180 and 285 kDa. The antibodies that bound to the lamina densa and anchoring fibrils recognized collagen VII. In this immunogold EM study we have shown four patterns of IgA labelling in six patients with LAD, associated with five different antigens as recognized by immunoblotting. These results, together with our previous immunofluorescence and immunoblotting findings add support to the contention that LAD is a heterogeneous disease as regards both the target antigens and epitopes.     

Two cases of recessive dystrophic epidermolysis bullosa diagnosed as severe generalized

Recessive dystrophic epidermolysis bullosa (RDEB) is a congenital bullous disease resulting from defective anchoring fibrils at the dermal-epidermal junction and mutations in the type VII collagen gene. In this report, we describe two patients with severe generalized RDEB. Patient 1 was a 24-day-old male infant, and patient 2 was a 1-day-old female infant. Immunofluorescence microscopy demonstrated absence of type VII collagen labeling in a skin sample of patient 1, and reduced staining in patient 2. Electron microscopy revealed absence of anchoring fibrils below the lamina densa in patient 1, and reduced or rudimentary anchoring fibrils in patient 2. Mutation analyses of COL7A1 in these patients revealed heteroallelic recessive mutations which resulted in premature termination codons (PTC): 6573+1G>C in intron81 and 886del6ins14 in exon 7 in patient 1, and 6573+1G>C in intron81 and 4535insC in exon 44 in patient 2. Heteroallelic combinations of PTC mutation generally result in the severe generalized type. Patient 2 has developed a digital fusion at age 2, which is a typical manifestation of severe generalized RDEB. The RDEB subtype is considered to be determined based on comprehensive information, including analysis of alleles, protein expression, ultrastructure and clinical symptoms after growth. However, mutation analyses of COL7A1 can provide valuable information estimating a diagnosis in early infancy.     

Evidence for a structural abnormality of collagen VII in a patient with dystrophic epidermolysis bullosa inversa.

Recent studies indicate that in skin of patients with dystrophic epidermolysis bullosa (EB) inversa, anchoring fibrils have an abnormal ultrastructure, but the major protein of these fibrils, collagen VII, is expressed and detectable with antibodies at the dermo-epidermal junction. For molecular characterization of this rare EB phenotype, skin biopsies from a patient with dystrophic EB inversa were investigated with indirect immunofluorescence, immunoelectron microscopy, and immunoblotting. Ultrastructural analysis of clinically uninvolved skin showed sublamina densa splitting. In unblistered areas, focal groups of anchoring fibrils that appeared loosely polymerized and without a distinct crossbanding pattern were observed. Indirect immunofluorescence staining with antibodies to collagen VII exhibited a linear fluorescence at the dermo-epidermal junction and at the roof of a spontaneous blister. Immunoelectron microscopy demonstrated staining of the poorly assembled anchoring fibrils, but no significant reaction in areas where no fibrillar structures could be discerned. In contrast to normal control skin, immunoblotting showed immunoreactive collagen VII in both epidermal and dermal extracts. Moreover, the dermis-associated collagen VII appeared as a distinct doubleband that contained the tissue form of collagen VII (250-300 kD) and an additional band with a slightly smaller molecular weight. In epidermal extracts one band, of the size of the tissue form, was detected. The studies on the present patient suggest that a structural abnormality of collagen VII that prevents its aggregation to stable dimers or polymerization to distinct anchoring fibrils may contribute to the etiopathogenesis of dystrophic EB inversa.     

Structure of basement membranes in malignant melanoma and nevocytic nevi

Basement membranes found around tumor cells in nevocytic nevi, Spitz's nevi, and malignant melanomas were analyzed by electron microscopy and antibody staining for several basement membrane proteins. Nevocytic nevi and Spitz's nevi showed a distinct, occasionally discontinuous lamina densa regardless of whether they were located in junctional zones of the epidermis or within the dermis. All basement membranes around nests of aggregated nevus cells, however, lacked anchoring fibrils. This correlated with the absence of type VII collagen. In contrast, type IV collagen, laminin, and nidogen were present at the periphery of the nevus cell clusters in agreement with the presence of an intact lamina densa. Aggregated tumor cells in malignant melanomas were bordered by a lamina densa when located in a junctional position and lacked this structure when they had migrated into the dermis. This process was accompanied by a drastically reduced staining for collagen type IV and nidogen, whereas laminin was still detectable. Anchoring fibrils and their molecular correlate, type VII collagen, were consistently absent. These observations demonstrate major alterations in the composition of basement membranes around malignant melanomas, which can be an important factor for the invasive growth and formation of metastases of these tumors.     

Type VII collagen is a component of cylindroma basement membrane zone

Cylindroma basement membranes (BMs) were studied by electron microscopy and immunofluorescence with antibodies to Types IV and VII collagen in order to correlate the ultrastructure with the biochemical characteristics. Type IV collagen served as a marker for lamina densa structures and Type VII collagen for the anchoring fibrils. Ultrastructurally, the cylindroma BMs were composed of a wide band of BM-like material in which numerous anchoring fibrils were embedded. The BMs surrounding the tumor cell clusters and nodules of BM-like material entrapped within the tumor cell islands stained positively for both Types IV and VII collagen. We conclude, that anchoring fibrils are a major component of cylindroma BM zone. A trichoepithelioma investigated as control showed a BM similar to the one found at the dermoepidermal junction, i.e. a BM distinctly different from the one of cylindroma. The trichoepithelioma BMs and nodules of BM-like material included within the tumor also stained positively for both Type IV and VII collagen.     

Immunofluorescent analysis of the basement membrane zone in lichen planus suggests destruction of the lamina lucida in bullous lesions

Lichen planus is an inflammatory dermatosis which is characterized histologically by an intense lymphocytic infiltrate at the dermal epidermal junction. This frequently results in disruption of the basement membrane zone, occasionally causing clinical blisters. In order to better understand the specific portion of the basement membrane zone which is disrupted by the lymphocytic infiltrate, we examined 7 cases of lichen planus with antibodies directed against anchoring filaments (GB3), the bullous pemphigoid antigen, anchoring fibrils (type VII collagen) and type IV collagen. In lesions without separation at the BMZ, all antibodies were strongly expressed, as in normal skin. In lesions with early separation, there was a focal decrease in GB3 staining, but types VII and IV collagen labelled normally. In lesions resulting in blisters, GB3 staining was essentially absent, and anti-types IV and VII collagen remained, but stained in a disrupted, less discrete pattern. The bullous pemphigoid antigen showed only slight deviation from the normal staining pattern. These findings suggest that the basement membrane zone in lichen planus is disrupted in the lamina lucida region. The lamina densa and sub-lamina clensa zones remain intact even in bullous lesions of lichen planus.     

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.     

Expression of the α1–α6 collagen IV chains in the dermoepidermal junction during human foetal skin development: temporal and spatial expression of the α4 collagen IV chain in an early stage of development

To study the expression of the α1–α6 chains of type IV collagen in the dermoepidermal junction (DEJ) during human foetal skin development, human foetal (10 and 20 weeks of gestation) and adult skin was immunostained with specific monoclonal antibodies to the α1–α6 chains of type IV collagen. Intense expression of the α4 chain and weak expression of the α2 and α6 chains were observed in the DEJ of 10 weeks gestational skin. In contrast, the α1, α2, α5 and α6 chains were detected in the DEJ of 20 weeks gestational and adult skin. Preferential expression of α4 during the early phase of development (10 weeks of gestation) may suggest a chain-specific regulatory mechanism for type IV collagen expression and its potential role in DEJ formation during development.