Abstract. Pemphigus is an autoimmune disease that causes blistering of human epidermis. We have recently shown that autoantibodies in the serum of three pemphigus patients bind to desmosomes (Jones, J. C. R., J. Arnn, L. A. Staehelin, and R. D. Goldman, 1984, Proc. Natl. Acad. Sci. USA., 81:2781-2785, and we suggested that pemphigus blisters form, at least in part, from a specific antibody-induced disruption of desmosomes in the epidermis. In this paper, experiments are described that extend our initial observations. 13 pemphigus serum samples, which include four known pemphigus vulgaris (Pv) and four known pemphigus foliaceus (Pf) serum samples, have been analyzed by both immunofluorescence and by immunoblotting using cell-free desmosome preparations. Tissue sections of mouse skin processed for double indirect immunofluorescence using each of the pemphigus serum samples and a rabbit antiserum directed against a component of the desmosomal plaque (desmoplakin) show similar punctate cell surface staining patterns. This suggests that all 13 pemphigus serum samples contain autoantibodies that recognize desmosomes. These autoantibodies appear specific for stratified squamous epithelial cell desmosomes and do not recognize desmosomes of other tissues (e.g., mouse heart and mouse intestine). Cultured mouse keratinocytes, which possess well-defined desmosomes, were processed for indirect immunofluorescence using the pemphigus serum samples. Eight of the 13 sera (including the four known Pv samples but not the known Pf sera) stain desmosomes in these preparations. By double indirect immunofluorescence the desmoplakin antiserum stains a double fluorescent line along the contacting edges of cultured keratinocytes, whereas the positive pemphigus serum samples stain a single fluorescent line along this same border. We believe that these pemphigus autoantibodies recognize extracellular antigens located somewhere within the region between the two apposing membranes that ~omprise the desmosome. The pemphigus sera exhibit positive immunoblotting reactions with desmosome-enriched fractions obtained from bovine tongue epithelium. Three serum samples (including two of the four known Pf serum samples) react with 160-and 165-kD desmosome-associated polypeptides (Koulu, L., A. Kusimi, M. S. Steinberg, V. KlausKovtun, and J. R. Stanley, 1984, J. Exp. Med., 160: I509-1518. Another eight serum samples (including the four known Pv sera) recognize a 140-kD desmosome-associated polypeptide. We propose that the antigens recognized by these human autoantibodies may play important roles in the adhesion of cells within the epidermis. Furthermore we discuss the heterogeneity of desmosome structure in light of our immunofluorescence and immunoblotting results.

Although the mammalian epidermal basal cell hemidesmosome bears some superficial resemblance to one half of a desmosome at the ultrastructural level, examination of the structure of the electron-dense submembranous plaques of the hemidesmosome and desmosome reveals that they differ with respect to their overall morphology and dimensions. Based on these findings, we wondered whether components of the desmosome are present in the hemidesmosome. In order to determine this we prepared a number of stratified squamous epithelial tissues for indirect immunofluorescence using antibody preparations directed against known desmosome components including desmoplakin and certain glycoproteins. These antibody preparations do not show reaction with hemidesmosomes by indirect immunofluorescence criteria. We have also utilized bullous pemphigoid (BP) autoantibodies that have been shown to recognize hemidesmosomes in mammalian skin cells [Mutasim et al., J. Invest. Derm., 84:47-53, 1985]. Double label indirect immunofluorescence observations of neonatal mouse skin prepared using desmoplakin antibodies and BP autoantibodies reveal that hemidesmosomes that are stained by the BP autoantibodies are not recognized by the desmoplakin antibodies. We confirmed these findings at the ultrastructural level by indirect immunogold localization of desmoplakin antibodies and BP autoantibodies. Therefore, the hemidesmosome does not appear to be one half of a desmosome and may possess a very different molecular organization relative to the desmosome. We raise the possibility that the variability between the hemidesmosome and desmosome that we detect at the morphological and immunological level may reflect the functional differences of these two types of junctions.

Autoantibodies in the serum of patients suffering the blistering skin disease pemphigus vulgaris recognize a 140-kDa glycoprotein (GP) present in enriched fractions of bovine tongue epidermal desmosomes. Immunofluorescence observations of cryostat sections of bovine tongue epidermis reveal that afflinity-purified rabbit antibodies to the 140-kDa GP generate a punctate intercellular stain that is similar to that generated by antibodies directed against a desmosome plaque component (desmoplakin). In cultured mouse keratinocytes, the antibodies against 140-kDa GP recognize desmosomes along areas of cell-cell contact. Double immunofluorescence of cultured keratinocytes with these antibodies and a desmoplakin antiserum reveals that the antibodies against the 140-kDa GP stain a single fluorescent line along areas of cell-cell contact. This single fluorescent line lies between double fluorescent lines generated by the desmoplakin antiserum. Immunogold ultrastructural localization reveals that the 140-kDa antigen is localized not only along the intercellular area of the desmosome but also is found along the whole epidermal cell surface. The antiiodies to the 140-kDa GP are able to induce a disruption of cell-cell contact in cultured keratinocytes that possess desmosomes. We propose that the 140-kDa GP is a cell adhesion molecule (CAM). Furthermore we discuss the heterogeneity of desmosomes in the light of our findings that antibodies against the 140-kDa GP recognize specific stratified squamous epithelial tissues.