Human autoantibodies against a desmosomal protein complex with a calcium-sensitive epitope are characteristic of pemphigus foliaceus patients

Pemphigus foliaceus (PF) patients have antibodies against a tightly, but noncovalently bound complex of polypeptides, which consists of desmoglein I (DGI) and other, possibly desmosomal, proteins. Most PF antibodies bind a calcium-sensitive epitope on this complex and chelation of calcium destroys the reactivity of these sera with the complex, but not the complex itself. The PF sera that do bind the desmosomal complex in the absence of calcium are those sera capable of binding denatured DGI on immunoblotting, and these same sera also immunoprecipitate only DGI when the desmosomal complex is dissociated with SDS. These findings demonstrate that autoantibodies against a complex of desmosome-associated proteins are characteristic of PF and define a calcium-sensitive conformational epitope on this complex.