Expression of pemphigoid antigen by SV40-transformed human keratinocytes

The expression and properties of pemphigoid antigen of SV40-transformed human keratinocytes were studied. By indirect immunofluorescence, SV40-transformed keratinocytes in passage 80-85 expressed the pemphigoid antigen as coarsely granular perinuclear fluorescence. To characterize this antigen, NP40 extracts of cells labeled with [14C]amino acids were immunoprecipitated using sera of 8 patients: bullous pemphigoid (6 patients), chronic localized pemphigoid (1 patient), and drug-induced lichen planus pemphigoides (1 patient). These immunoprecipitates were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and then fluorographed. All 8 sera precipitated a protein of Mr 240K, while normal human sera did not precipitate this protein. These results indicate that SV40-transformed human keratinocytes synthesize pemphigoid antigen, and that autoantibodies in the sera of pemphigoid patients with different clinical features identify the same antigen of Mr 240K in these cells.