Studies of patients with anti-epiligrin cicatricial pemphigoid.
We have recently identified patients with a form of cicatricial pemphigoid who have IgG anti-basement membrane autoantibodies directed against epiligrin, a laminin isoform closely related if not identical to laminin 5. These patients' autoantibodies bind the lower lamina lucida of human epidermal basement membrane and immunoprecipitate this laminin isoform from extracts and media of biosynthetically radiolabeled human keratinocytes. Immunoblot studies show that these patients' autoantibodies specifically bind the alpha subunit of this laminin (i.e., laminin subunit alpha 3). We have found no evidence of these autoantibodies in normal volunteers or patients with other bullous skin diseases (including those with other forms of CP). These studies have identified a group of patients with an acquired, autoimmune, subepidermal bullous disorder who have disease-specific autoantibodies directed against the alpha subunit of epiligrin/laminin 5. These findings correlate with prior reports showing that a monoclonal antibody directed against this laminin subunit induces detachment of keratinocytes from extracellular matrix in vitro as well as epidermis from human skin in situ. Together, these findings suggest that this laminin mediates attachment of basal keratinocytes to epidermal basement membrane and that autoantibodies directed against it may be pathogenic. Moreover, recent studies showing that subunits of this laminin isoform are mutated in some patients with Herlitz's junctional epidermolysis bullosa indicate that acquired or inherited abnormalities in this adhesion ligand are associated with skin diseases characterized by separation of epidermis from epidermal BM.