The presence of anti-basement membrane zone antibodies in the sera of patients with non-bullous lupus erythematosus.

We performed indirect immunofluorescence (IF) studies using 1 mol/l sodium chloride split skin to determine whether or not a positive IF is specific to patients with bullous lupus erythematosus (LE). We examined the sera from 21 patients with systemic LE (SLE), three of which were obtained from two SLE patients and one subacute cutaneous LE (SCLE) patient with bullous eruptions. As a comparison, we also studied the sera from patients with discoid LE (DLE, n = 7), SCLE (n = 1), systemic sclerosis (SSc, n = 20), bullous pemphigoid (n = 2) and normal individuals (n = 10). Sera from 16 SLE, four DLE and two SSc revealed a linear deposition of IgG isotype antibody at the epidermal side and/or the dermal side on indirect IF of split skin. The sera from three patients with bullous eruption and from 12 patients of SLE, SCLE, DLE without bullous eruption or SSc were further analysed by immunoblotting using five defined antigens, i.e. dermal extract, epidermal extract, three fusion proteins of 230 kDa bullous pemphigoid antigen (BPAG). 180 kDa BPAG, and human epidermolysis bullosa acquisita (EBA) antigen. Two SLE sera as well as one of the SCLE and the DLE serum reacted with 230 kDa BPAG in epidermal extract, and one of the SCLE and the DLE serum also reacted with the fusion protein of 180 kDa BPAG. No serum reacted with the dermal extract or the fusion protein of 230 kDa BPAG or EBA antigen. There was no consistent correlation between split-skin IF results and immunoblotting results. These results may suggest that even non-bullous LE patients often have autoantibodies to the basement membrane zone antigens, most of which are less pathogenic. Although we rarely examine the sera from non-bullous LE patients, we should keep this phenomenon in mind to avoid overestimating the results of split-skin test and immunoblotting.