The immune response against murine IgG2a immunoglobulin was studied in 42 gastrointestinal cancer patients treated with mouse monoclonal antibodies. IgM, IgA, and all 4 IgG subclasses directed against mouse immunoglobulin were studied. Thirty of 42 patients developed an anti-mouse response of IgG isotype, often associated with IgM and IgA specific for mouse monoclonal antibodies circulating in serum. Patients first developed an IgM response, followed by IgA and IgG. IgG1 was found to be the most frequently expressed isotype, followed by IgG2 and IgG3. IgG4 was detected in only 6 patients.
Presented at the “Second Conference on Radioimmunodetection and Radioimmunotherapy of Cancer,” September 8–10, 1988, Princeton, NJ. This work was supported by a fellowship from the Minister of Foreign Affairs, France, and NIH Grants CA 10815, CA 2587, and CA21124.