Expression of cross-reactive idiotypes at the basement membrane zone in patients with bullous pemphigoid

The purpose of the present study was to determine whether tissue-bound anti-basement membrane zone (BMZ) autoantibodies in patients with bullous pemphigoid (BP) express a cross-reactive idiotype. We assayed 34 skin biopsies from 26 patients with BP and nine biopsies from control subjects, including normal subjects and patients with epidermolysis bullosa acquisita for the presence of a cross-reactive idiotype at the BMZ. Perilesional split-skin biopsies were assayed for the presence of immunoreactants, immunoglobulin G, and complement and for reactivity with a monoclonal anti-idiotypic antibody specific for a circulating anti-BMZ antibody, anti-Id 3-17. Anti-Id 3-17 bound in a linear band to the BMZ in 12 of 26 patients with BP (46%) and in 0 of 9 control subjects. In serial biopsy specimens, the presence or absence of cross-reactive idiotype at the BMZ in six patients was stable during the disease course. This cross-reactive idiotype has been previously identified in the serum of 36% of patients with BP; however, in this study, no correlation was noted between the presence of the cross-reactive idiotype in skin and serum of individual patients. Because cross-reactive idiotypes occur as a consequence of restricted variable-region gene utilization, the demonstration of a cross-reactive idiotype at the BMZ previously identified in the serum of patients with BP supports the hypothesis that circulating and tissue-bound autoantibodies in this disease arise from a common genetic origin.