Identification of pemphigus-like antigens expressed by SCaBER cells

Indirect immunofluorescence revealed the presence of pemphigus-like antigenic activity on SCaBER cell monolayers after incubation with sera from patients with pemphigus vulgaris. In contrast, no fluorescence was observed after incubation of the cells with sera from patients with bullous pemphigoid, systemic lupus erythematosus or healthy individuals. In order to identify this pemphigus-like antigen, the SCaBER cell membrane proteins were solubilized in non-ionic detergent, separated according to their molecular weight by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and electrophoretically transferred to nitrocellulose sheets. After incubation with pemphigus serum followed by 125I-radiolabelled goat anti-human IgG, autoradiography revealed pemphigus antibody binding activity in the 105 Kd region in electrophoretograms of the unreduced SCaBER cell membrane extracts. This pemphigus-like antigen was isolated by affinity chromatography on the Sepharose-linked IgG fraction of sera from patients with pemphigus vulgaris.