[Examination of the patient serum presenting a CEA false high value after cancer immuno-cell therapy]

False positive elevation of carcinoembryonic antigen (CEA) was observed in a 65-year-old woman who was treated with dendritic cell therapy (DCT) and activated lymphocyte therapy (ALT) for intrahepatic cholangiocarcinoma. Three months after the initiation of these therapies, her CEA value measured by AIA (TOSOH) began to increase without any evidence of worsening of cholangiocarcinoma. CEA was measured by several different methods, and only the result measured by AIA was high, indicating the presence of a false positive phenomenon. To clarify this phenomenon, we evaluated the patient's serum precisely. Gel filtration chromatography of her serum showed that CEA was detected in the elution fraction of IgG, which was different from the reference samples. Furthermore, this peak disappeared after incubation of patient's CEA and HBR-1. The immunoglobulin absorption test revealed that CEA value was decreased only after absorption of IgG and absorption tests using HBR-1 and MAK-absorbents showed a dramatic decrease in CEA value. These findings indicated the presence of IgG type human anti-mouse antibodies (HAMA), which interfered the measurement by AIA. Although we could not identify the reason why HAMA was produced in this patient, the facts that the false positive phenomenon was observed after the initiation of DCT and ALT, and that CEA value decreased after theses therapies were discontinued, indicated that immuno-modulaton by DCT and ALT may have a close relationship to HAMA production. It was probable that DCT and ALT activated preexisting heterophile-antibody-producing cells, which stimulated HAMA production. The incidence of such false positive reaction of CEA by HAMA in patients with DCT and ALT was low, but as the number of the patient with immuno-cell therapy increases, the incidence of such phenomenon surely increases. Because HAMA reacts to all types of immunoassay, careful attention should be paid to the evaluation of laboratory findings in patients undergoing with such immuno-cell therapies.