Binding of murine immunoglobulin to human tissues after immunotherapy with anticolorectal carcinoma monoclonal antibody.

An anticolorectal carcinoma antibody, 17-IA, that is of gamma 2a isotype and has been used in previous immunotherapy trials, binds to an antigen on most human colon tumors. This antigen is destroyed by the fixative and embedding procedures employed for routine histologic evaluation of tissues. It can be demonstrated by the avidin/biotin-labelled peroxidase complex (ABC) immunoperoxidase technique on briefly fixed, frozen sections of fresh human tissues. With this assay technique, the antibody is found to bind in vitro to both human colonic carcinoma and normal gastrointestinal epithelia. Tissues removed from patients having received the 17-IA antibody intravenously in an immunotherapy trial show bound antibody 1-2 after administration. This is no longer evident 3 weeks later though the antigen is present on the cell surface and is still capable of binding antibody in vitro.