Characterization of bullous pemphigoid antigen synthesized by cultured human squamous cell carcinoma cells

This report concerns the characterization of bullous pemphigoid antigen (BPA) in cultured cells derived from a human squamous cell carcinoma (SCC cells) as identified by sera of 9 patients with bullous pemphigoid (BP). Immunoglobulin G from 5 of 9 BP sera bound the cell surfaces of SCC cells with a punctate staining pattern by immunofluorescence. The other four BP sera and all 12 controls sera showed no specific staining. To characterize the antigen for pemphigoid antibody, we immunoprecipitated NP-40 extracts of cells labeled with [14C] amino acids using nine BP sera and 12 controls sera. These immunoprecipitates were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by fluorography. The five BP sera that gave positive immunofluorescence results also precipitated a protein with molecular weight (mol wt) of 110 kD, whereas the other four BP sera negative by immunofluorescence and all 12 controls sera did not precipitate this protein. These results indicate that the sera of patients with BP contain antibodies against the protein with mol wt 110 kD in the SCC cells used in this study. With use of four BP sera, two of which were positive to this mol wt 110 kD BPA and two of which were negative, immunoprecipitation was carried out in Pam cells. One 110 kD-positive serum and two 110 kD-negative sera, precipitated a BPA of mol wt 220 kD from Pam cells labeled with [35S] methionine. These results suggest that BP sera may recognize more than one antigen, in addition to possible BPA heterogeneity in different individuals.