Further analysis of pemphigus autoantibodies and their use in studies on the heterogeneity, structure, and function of desmosomes

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 suggest 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 cultures 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 comprise 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. Klaus-Kovtun, and J.R. Stanley, 1984, J. Exp. Med., 160:1509-1518). 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.