Anti-laminin gamma-1 pemphigoid

Anti-p200 pemphigoid has been characterized by autoantibodies to an unidentified 200-kDa protein (p200) of the dermal-epidermal junction. The objective of this study was to identify p200. We performed 2D gel electrophoresis of dermal extracts and immunoblotting with patients' sera, followed by MS analysis of a unique protein band. The protein band corresponded to laminin gamma 1. Anti-laminin gamma 1 mAb reacted with the anti-p200 immunoprecipitates by immunoblotting. Sera from 32 patients with anti-p200 pemphigoid showed 90% reactivity to the recombinant products of laminin gamma 1. None of the healthy control sera reacted with laminin gamma 1. By immunoblotting, reactivity of a patient's serum with p200 was competitively inhibited by adding anti-laminin gamma 1 C-terminus mAb. Purified anti-p200 IgG also inhibited the reactivity of this mAb to dermal laminin gamma 1. Most laminin gamma 1-positive sera showed reactivity with recombinant laminin gamma 1 C-terminal E8 fragment. Reactivity of patients' sera and purified IgG to dermal laminin gamma 1 was higher than reactivity to blood vessel laminin gamma 1 under reducing conditions. These results suggest that laminin gamma 1 is the autoantigen for patients with anti-p200 pemphigoid. The autoantibodies may specifically recognize dermal laminin gamma 1 with unique posttranslational modifications. The epitope is localized to the 246 C-terminal amino acids within the coiled-coil domain. The 9 C-terminal residues are known to be critically involved in laminin recognition by integrins.