Anti-laminin gamma-1 pemphigoid

Abstract

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 γ1. Anti-laminin γ1 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 γ1. None of the healthy control sera reacted with laminin γ1. By immunoblotting, reactivity of a patient's serum with p200 was competitively inhibited by adding anti-laminin γ1 C -terminus mAb. Purified anti-p200 IgG also inhibited the reactivity of this mAb to dermal laminin γ1. Most laminin γ1-positive sera showed reactivity with recombinant laminin γ1 C -terminal E8 fragment. Reactivity of patients' sera and purified IgG to dermal laminin γ1 was higher than reactivity to blood vessel laminin γ1 under reducing conditions. These results suggest that laminin γ1 is the autoantigen for patients with anti-p200 pemphigoid. The autoantibodies may specifically recognize dermal laminin γ1 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.