Demonstration of two disease specific antigens in circulating immune complexes.

A method is described to assess antigenic cross-reactivity between soluble immune complexes precipitated from sera with polyethylene glycol. The precipitated complex from one serum was dissociated in acid and used to coat a plastic cup. Radioiodinated complexes from another serum were dissociated in the cup, neutralized and allowed to reassociate overnight. The binding of the labelled complex was used to measure the cross-reactivity between the complexes. Using this technique, complexes from a group of patients with haematuria and hypertension have been found to share an antigen, and a different antigen was found in patients with bullous pemphigoid. The participation of rheumatoid factors in the cross-reactions is unlikely, and no cross-reactivity of either group was found with sera from patients with rheumatoid arthritis.