Studies in (a), (b), and (c) were conducted using human keratinocytes cultured in 0.5mm calcium for 18 hours before experimentation. (a) Representative immunofluorescence images show that PV IgG, but not normal (NL) IgG, recognizes a plasma membrane antigen with a localization pattern similar to that of DSG3. Scale bar = 10 μm. (b) Western blot analysis examining reactivity of human sera and antibodies against human keratinocyte protein lysates. PV and NL sera, purified PV and NL IgG fractions, and DSG3 antibodies were tested. (c) Immunoprecipitation–Western blot analysis of proteins immunoprecipitated by NL and PV IgG and probed for the desmosome components DSG3, PG, and DP. 10% of the input is shown. (d) Mechanical dissociation assay performed on monolayers of wild-type mouse keratinocytes treated with PV IgG or NL IgG for 24 hours. The numbers of fragments generated were counted in four 40 × fields in each of three experiments, and results represent the mean±SEM (n = 12). Statistical significance (*) was determined using the unpaired Student’s t-test (P<0.05).