IDENTIFICATION OF A 168-KDA MUCOSAL ANTIGEN IN A SUBSET OF PATIENTS WITH CICATRICIAL PEMPHIGOID

This study describes the presence of antibodies in sera from patients with cicatricial pemphigoid specific for a 168-kDa antigen expressed b y buccal mucosa. Six cicatricial pemphigoid sera unreactive with epide rmal or dermal proteins in immunoblot assay were tested on mucosal pro tein extracts. Four of these sera labeled a mucosal 168-kDa antigen (M 168) under reducing conditions. An additional cicatricial pemphigoid s erum with circulating antibodies to 180-kDa bullous pemphigoid antigen (BPAg2) also labeled M168. None of these cicatricial pemphigoid sera reacted with the alpha, beta, or gamma subunits of laminin-5. Nitrocel lulose elution studies showed that the M168 antigen is a basement memb rane antigen and labeled the epidermal side of salt-split skin, Immuno affinity-purified anti-M168 antibodies did not bind to the 230-kDa bul lous pemphigoid antigen (BPAg1) or to the 180-kDa BPAg2. None of the c ontrol sera from healthy individuals or from bullous pemphigoid, pemph igus vulgaris, or pemphigus foliaceus patients reacted with M168. This study demonstrates the specificity of some cicatricial pemphigoid ser a against a 168-kDa antigen that is different from the laminin-5 subun its and shares no epitopes with the antigens of bullous pemphigoid (BP Ag1, BPAg2) or the epidermolysis bullosa acquisita.