Evidence against the presence of circulating immune complexes in chronic inflammatory bowel disease.

Several investigators have reported the presence of circulating immune complexes in serum from patients with Crohn's disease and chronic ulcerative colitis. Because previous assays employed conditions which might have caused immunoglobulin aggregates to form in vitro, thus falsely suggesting the presence of immune complexes in vivo, we tested inflammatory bowel disease sera for immune complexes using four assays designed to minimize in vitro immunoglobulin aggregation. In three assays immune complexes were not detectable, while in a fourth, the Clq precipitin test, positive reactions occurred. These precipitin reactions did not have characteristics of immune complexes. Our data suggest that circulating immune complexes are either not present in patients with inflammatory bowel disease or that they occur infrequently or in low concentration.