BULLOUS PEMPHIGOID AND LINEAR IGA DERMATOSIS SERA RECOGNIZE A SIMILAR120-KDA KERATINOCYTE COLLAGENOUS GLYCOPROTEIN WITH ANTIGENIC CROSS-REACTIVITY TO BP180

Circulating IgG from a large subset of bullous pein; phigoid (SP) pati ents reacted on immunoblot with a 120-kDa protein in conditioned kerat inocyte culture medium and in keratinocyte cell extracts, A protein wi th a similar molecular weight was recognized by circulating IgA from a subset of patients with linear IgA dermatosis (LAD). Both affinity-pu rified 120-kDa-specific BP IgG and 120-kDa-specific LAD IgA bound to t he roof of salt-split skin. Both proteins recognized are collagenous g lycoproteins. Deglycosylation with N-glycosidase F resulted in an iden tical reduction in molecular weight for both the BP-IgG-recognized pro tein and the LAD-IgA-recognized protein, Both proteins were equally su sceptible to digestion with type VII collagenase, Furthermore, both pr oteins were absent from conditioned culture medium of keratinocytes fr om patients with BP180-deficient general atrophic benign epidermolysis bullosa (GABEB). Immunodepletion studies showed that the 120-kDa LAD antigen could be removed from conditioned culture medium by anti-120-k Da BP IgG. Thus these results indicate that these proteins are either highly related or, most probably, identical, A strong antigenic relati onship between the 120-kDa protein and the 180-kDa bullous pemphigoid antigen (BP180) was detected by cross-reaction of affinity-purified an ti-120-kDa BP patient antibodies to BP180 and cross-reaction of monocl onal anti-180-kDa antibodies to the 120-kDa protein. Notwithstanding t his cross-reactivity, the 120-kDa protein also exhibits unique epitope s demonstrated by the nonreactivity of individual anti-120-kDa BP and LAD patient serum with the 180-kDa antigen.