Specific detection of anti-idiotypic immune responses in cancer patients treated with murine monoclonal antibody.

Procedures are described for the specific detection in cancer patients' sera of human antibodies raised during the course of monoclonal antibody (MAb) immunotherapy against common and idiotypic determinants of monoclonal anti-colon carcinoma antibody 17-1A. The possible interference of serum factors in these assays other than human anti-murine immunoglobulin antibodies has been virtually excluded. Minimal detectable concentrations of antibody in the various assays ranged between 0.1 and 2.8 micrograms antibody per ml serum. Thirty-five of 41 patients who raised an immune response against the administered MAb produced anti-idiotypic antibodies in concentrations of up to 42 micrograms per ml serum. Anti-idiotypic antibodies persisted in the blood for up to 475 days following the administration of a single dose of MAb. A significant proportion of the anti-idiotypic antibodies were directed against the antigen-combining site of the MAb. The importance of these results in light of possible immunoregulatory functions of the anti-idiotypic antibodies is discussed.