Serum levels of autoantibodies to BP180 correlate with disease activity in patients with bullous pemphigoid

Background The 180‐kDa transmembrane hemidesmosomal protein (BPAG2) has been identified as an important autoantigen in bullous pemphigoid (BP). Using the NC16A domain as the antigenic target, a highly sensitive and specific enzyme‐linked immunosorbent assay (ELISA) for the detection of autoantibodies to BP180 was developed. Aim To investigate the correlation of clinical severity and ELISA indices in BP. Methods Antibody titers in the sera from 20 patients were measured using BP180NC16a‐ELISA, and an analysis of the correlation of ELISA indices with disease activity was performed. Serum was obtained from each patient with BP at least three times: before the initiation of treatment, during complete disease control just before the decrease in corticosteroid, and when the dosage of corticosteroid was successfully decreased to half the initial dose. Of the 20 patients, three showed recurrence at a later stage, caused by their decision to stop treatment; serum was obtained at the early stage of recurrence. Results ELISA indices were significantly decreased after successful therapy, although indirect immunofluorescence titers did not always show apparent correlations. Indices measured using BP180NC16a‐ELISA were well correlated with disease activity. Three patients decided to stop taking their medication; subsequently (within 1–2 weeks), blisters recurred, and the levels of antibodies to BP180 increased to close to those before the initiation of treatment. Conclusion BP180 antibody titers showed a closer correlation than indirect immunofluorescence titers to disease activity. The titer of BP180 antibody may be a useful tool for the evaluation of disease activity and for the assessment of the effectiveness of treatments in BP.