Detection of antibodies after immune complex splitting in serum of patients with bullous pemphigoid and systemic lupus erythematosus.

No free anti-basement membrane antibodies were found in the sera of four patients with bullous pemphigoid, and no free anti-DNA antibodies in the sera of two patients with systemic lupus erythematosus. The sera treated with 3 mol/l urea and by gel chromatography to separate these antibodies from any circulating complexes, and antibodies to basement membrane were detected by immunofluorescence and to DNA by the Farr technique. The appropriate antibodies were found in all the sera, indicating that failure to detect antibodies by routine procedures may be due to binding of the antibodies to soluble antigens forming complexes in the sera.