Abstract
Samples of malignant ascitic fluid from 30 patients with advanced ovarian carcinoma were examined for the presence of IgM antibodies to CEA and PEG‐precipitable proteins binding to ^125^I‐CEA. The IgM antibodies to CEA were measured by a solid‐phase radioimmunoassay using ovarian CEA. There was no correlation between the level of IgM antibodies to CEA and that of total IgM in the fluid. In 11 of 30 (37%) samples tested, significant amounts of IgM antibodies to CEA were found. The CEA‐binding proteins were measured by the ability of ascitic fluid to incorporate ^125^I‐colonic‐CEA into PEG‐precipitable complexes. In 9 of 39 (30%) samples, the precipitation was significant. There was no association between antibodies to the ABO and Lewis blood group factors and these antibodies to CEA. An inverse relationship was observed between the level of CEA and that of CEA‐binding proteins shown by the two assays. When ^125^I‐CEA was incubated with these “positive” samples, a high molecular weight fraction was demonstrated by chromatography. By contrast, in the “negative” samples, there was no incorporation of ^125^I‐CEA. These findings would indicate the presence of CEA‐reactive proteins possibly existing as immune‐complex‐like material in ascitic fluid of some patients.