Colorectal carcinoma. Evidence for circulating CEA-anti-CEA complexes.

Significant increments in measurable plasma CEA were effected by 2.5 M MgCl2 elution from putative circulating CEA-anti-CEA complexes in 11 of 15 patients with disseminated colorectal cancer and in five of ten patients with a high probability of having subclinical disease (Dukes'C category). Following 2.5 M MgCl2 elution, IgG from a patient with a high CEA increment effected a higher specific binding to 125I-CEA than a similar IgG eluate from a patient with a negligible increment in measurable CEA. These data suggest that CEA is autoimmunogenic and may result in circulating CEA-anti-CEA complex formation. The clinical implications of such complexes in the diagnosis and monitoring of patients with colorectal cancer remain to be determined.