Circulating immune complexes in Behçet's syndrome: purification, characterization and cross-reactivity studies.

The C1q-binding assay was performed on 30 sera from patients with Behçet's syndrome and circulating immune complexes were found in 46%. Circulating immune complexes were isolated and purified from the sera of two patients by immunoadsorption on a column of polymethylmetacrylate beads coated with C1q and then labelled with 125I. In double immunodiffusion these purified immune complexes were found to contain IgG, C1q, C1s and C3. Anti-IgG activity was not detectable in the purified immune complexes while specific cross-reactivity was found in a solid-phase radioimmunoassay with the majority of the sera of behçet's syndrome.