Bullous pemphigoid: serum antibody titre and antigen specificity.

2 antigens have been identified as possible targets for autoantibody depositions in bullous pemphigoid: a 230-kD protein (BP230) and a 180-kD protein (BP180). We studied the relationship of these 2 antigens with the immunofluorescence determined serum antibody titre: 2 groups of bullous pemphigoid patients were selected on the basis of immunoblot-determined antibody specificity. One group (13 patients) had antibody specificity for BP230 and not for BP180, while the other group (9 patients) had antibody specificity for BP180 and not for BP230. The immunofluorescence titres of the circulating antibodies determined on monkey oesophagus substrate displayed, for the BP230-specific group, a mean of 1:1102. The maximal observed titre was 1:5120. The mean titre in the BP180-specific group was only 1:29, with a highest titre of only 1:160. This result suggests that in routine indirect immunofluorescence of bullous pemphigoid sera, the contribution of the BP180-specific antibodies to the total anti-epidermal basement membrane zone antibody titre is relatively much lower than that of the BP230-specific antibodies. Thus, at high dilutions, only the BP230-specific antibodies contribute to the overall indirect immunfluorescence titre.