Identification of a 160-kD molecule as a component of the basement membrane zone and as a minor bullous pemphigoid antigen.

The antigens in normal human skin defined by antibodies in patients with bullous pemphigoid (BP) were studied by Western immunoblots. Eighteen (90%) of 20 BP sera reacted to a 230-kD antigen. Seven (35%) of the sera reacted to a 160-kD antigen. Two of these reacted only to the 160-kD antigen and five also reacted to the 230-kD antigen. Antibodies to the 160-kD antigen were not present in 25 control sera obtained from normal individuals or patients with other bullous diseases. The 160-kD antigen was present in epidermal extracts of four different specimens of normal human skin but not in dermal extracts or extracts of control cells including melanoma, fibroblasts, lung carcinoma, and colon carcinoma. Monospecific sera with antibodies to either the 230-kD or to the 160-kD antigen reacted solely to their respective target antigens, but not to both, in extracts of epidermis that contained both antigens. The 160-kD antigen broke down to a 140-kD fragment, while the 230-kD antigen was unchanged in the absence of protease inhibitors. Western blot affinity purified antibody to the 160-kD antigen bound only to the basement membrane zone on the epidermal side of 1M NaCl split skin. These results indicate that a 160-kD antigen is a normal component of the basement membrane zone of human skin. The antigen is located on the epidermal side of skin split with 1M NaCl. It is a minor BP antigen, antibodies to which are present in some patients with BP.