Immunofluorescent localization of type IV collagen and laminin in human skin and its application in junctional zone pathology

Skin calcium-binding protein immunoreactivity in basal cell carcinoma

Skin calcium-binding protein (SCaBP) is a low molecular weight protein of unknown function which is localized in the cytoplasm of epidermal basal cells. We have examined SCaBP immunoreactivity in basal cell carcinoma (BCC) since BCC cells retain some of the characteristics of basal cells, including the capacity for proliferation and migration from the dermo-epidermal junction. We also examined immunoreactivity to basement membrane zone (BMZ) antigens (type IV collagen, laminin and bullous pemphigoid antigen) in BCC. We found that all BCC cells showed SCaBP immunoreactivity regardless of the histological type or position of the cells. BMZ antigens were expressed around tumourous buds, although bullous pemphigoid antigen may also present a cytoplasmic immunoreactivity. Our results suggest that SCaBP immunoreactivity is independent of the basal position of the cell, but may be related to the proliferative capacity and the undifferentiated state of the cell.

Distribution of fibronectin and laminin in basal cell epitheliomas

The distribution of fibronectin (FN) and laminin (LM) in basal cell epithelioma was evaluated by indirect immunofluorescence. FN is a glycoprotein which promotes interaction between cells and the extracellular matrix, and is present at the dermal-epidermal junction (DEJ) and throughout the dermis, but absent in the normal epidermis. LM, a noncollagenous basement membrane protein, plays a role in epithelial adhesion to type IV collagen, and is normally present in the DEJ, but absent in the epidermis. The role of FN and LM in epithelial differentiation has not been established. Therefore, the distribution of FN and LM in a tumor of epithelial origin was studied by indirect immunofluorescence. Using affinity-purified antibodies to FN and LM, and the appropriate fluorescein-conjugated second antibodies, normal skin and 7 basal cell tumors were examined. By immunofluorescence, nests of malignant basal cells were surrounded by linear LM staining. FN immunofluorescence was intense throughout the connective tissue stroma of all tumors. Five tumors also showed FN staining within the nests of neoplastic cells, and 4 of these were also LM-positive in the tumor bulk. These immunofluorescent findings suggest that epidermal neoplasia can be associated with alterations in the distribution of FN and LM.

Immunohistochemical localization of laminin, type IV and type V collagen in basal cell carcinoma

Laminin, type IV and type V collagen were localized in twenty-five basal cell carcinomas (BCCs) by immunofluorescence. All basal cell carcinomas were separated from the connective tissue by a continuous basement membrane (BM) which always contained the three antigenic determinants. Nodular and cystic BCCs, but not pagetoid BCCs, contain linear and globular deposits of these BM components. The linear deposits probably represent BM debris that remains undigested and the globular deposits correspond to residual cytoplasmic fragments occurring during apoptosis. These results suggest that BM components are synthesized by epithelial cells and are secreted to polymerize at the dermo-epidermal junction.

Procollagen localisation in normal, premalignant and malignant lesions of the epidermis

The distribution of procollagen in normal hyperplastic, preneoplastic or neoplastic human epidermal lesions has been analysed in indirect immunofluorescence tests with the antibodies to procollagen raised in sheep to extracted procollagen, synthesised by newborn rat skin explants in culture. These antiprocollagen antibodies produced indirect immunofluorescence staining only of the papillary dermis of human skin. We reacted serial dilutions of the antibody with each skin lesion and recorded the maximum dilution at which a positive reaction was observed. All lesions examined displayed essentially the same procollagen immunofluorescence pattern. The fluorescence was localised as a fibrillar/diffuse area just under the epidermis. In conditions in which the epidermis is highly convoluted, the fluorescent band was found to follow the pattern of the epidermis and to surround epidermal 'islands' in the deeper dermis. Our observations suggest that in the neoplastic lesions a new dermal topography, resembling the stratum papillare of normal human skin, is found in the deeper dermis surrounding the epidermal islands produced as the epidermal mass increases and invaginates further into the stroma. Malignant epidermal lesions were found to show a positive procollagen immunofluorescent staining at tenfold lower concentrations of the antibody than normal human skin in subepidermal regions.