Expression pattern of the bullous pemphigoid-180 antigen in normal and neoplastic epithelia

BP180 is a 180kDa hemidesmosomal protein recognized by bullous pemphigoid (BP) and pemphigoid gestationis (PG) autoantibodies. Recent cloning and sequence analysis performed by our laboratory have revealed that BP180 is a transmembrane protein with a long extracellular collagen-like region. A rabbit polyclonal antibody has been generated against a recombinant protein, designated GST-N delta 1, containing a segment of the BP180 ectodomain. The resulting antiserum, RN delta 1A, was shown to specifically react with BP180 on immunoblot, and labelled the extracellular region of the epidermal hemidesmosome on immunoelectron microscopy. A panel of normal and neoplastic human tissues were analysed by indirect immunofluorescence (IF) and RN delta 1A, to determine the distribution of BP180. A total of nine basal cell carcinomas (BCCs) and four squamous cell carcinomas (SCCs) of the skin were also studied. Intense IF staining was seen along the basement membrane zone (BMZ) of the epidermis, hair follicles, and the periphery of sebaceous gland lobules. The sebaceous lobules showed more intense staining in areas close to the duct. The epithelial BMZ of the following tissues also reacted with RN delta 1A: cornea, ocular conjunctiva, buccal mucosa, upper oesophagus, placenta (amnion placentum), umbilical cord and transitional epithelium of the bladder. The epithelium of the jejunum and ovary failed to react with RN delta 1A. Staining of the BCCs and SCCs was variable. Five of six nodular BCCs showed some anti-BP180 staining at the tumour-stromal interface, although the level of staining was less intense than that observed in the overlying normal epidermis. All three morphoeic BCCs analysed in this investigation did not show any staining with RN delta 1A. Three of four SCCs showed weak staining at the tumour-stromal interface. Thus, the tissue distribution of BP180 paralleled that of hemidesmosomes, and expression of this protein was found to be decreased or absent in cutaneous neoplasms.