Isolation and preliminary characterization of circulating immune complexes from rabbits with experimental syphilis

Immune complexes isolated from sera of rabbits with experimental, disseminated syphilis were found to have sedimentation coefficients greater than 19s. By radioimmunoblot assays, materials precipitated with 2.5% polyethylene glycol or chromatographed on DEAE-Affi-Gel Blue were found to contain albumin, C3, immunoglobulin M (IgM), IgG, and treponemal antigen(s), whereas control materials contained only albumin and IgG. When polyethylene glycol precipitation of immune complexes from syphilitic rabbits was followed by immobilization on protein A and acid elution, radioimmunoblots detected only IgG and treponemal antigen(s).