Demonstration of antibodies in patients' sera, directed against nonspecific cross-reacting antigen.

Nonspecific cross-reacting antigen (NCA), which strongly cross-reacts with carcinoembryonic antigen, was demonstrated to be an autoantigen. Antibodies directed against NCA were shown in different groups of patients, but high titers (greater than 1/64) were found only in cancer patients. A correlation between tumor mass, antigen load, and antibody titer apparently existed. Sera obtained from patients preoperatively and postoperatively differed significantly (P greater than 0.01) in the sense that titers were high only in sera sampled after the patients were treated. Nevertheless, the formation of these antibodies cannot be considered a cancer-specific phenomenon because of their existence also in patients with nonmalignant diseases.