Characterization of 230-kD bullous pemphigoid antigen associated with the detergent-insoluble fraction of cultured keratinocytes.

The 230-kD protein identified by antibodies from patients with bullous pemphigoid (BP) has a dual location in cultured normal human epidermal keratinocytes: part in a high-speed supernatant of homogenized cells and part in a particulate fraction, where it is resistant to extraction by non-ionic detergent or mild base. Antibodies were affinity purified from the particulate 230-kD BP antigen, which can be extracted in the presence of urea. The affinity-purified antibodies bind not only the cytosolic 230-kD protein, showing that it is related, if not identical, to the particulate form, but also produce a discontinuous granular pattern by indirect immunofluorescence in the basement membrane zone of rabbit esophagus. In stratifying epidermal cultures, expression of the 230-kD BP antigen is limited to basal cells. These data are consistent with 230-kD BP antigen involvement in keratinocyte basal cell interaction with extracellular matrix and indicate that the cultured cell may provide a useful model for analysis of 230-kD BP antigen function.