Detection in colorectal carcinoma patients of antibody cytotoxic to established cell strains derived from carcinoma of the human colon and rectum

Sera from eight of 15 patients with colonic carcinoma exhibited demonstrable cytotoxicity against an established cell strain derived from adenocarcinoma of the ileocecum, HCT‐8. Sera from 12 of 16 patients with rectal carcinoma were cytotoxic for an established cell strain derived from an adenocarcinoma of the rectum, HRT‐18. Patients with colonic carcinoma exhibited serum cytotoxicity against only the colonic target cells, whereas patients with rectal carcinoma gave significant cytotoxicity against both cell strains. This cytotoxicity was shown to be complement‐dependent and appeared to be specific for colonic and/or rectal carcinoma cells. Although the cells produced carcinoembryonic antigen (CEA) in vitro, the cytotoxic antibody response in these patients did not appear to be directed against CEA. Serum cytotoxicity was not demonstrated against two other cell strains, HCT‐48 and HT‐29, derived from adenocarcinomas of the human colon, except for a reaction against a blood‐group‐related antigen. These cell strains had comparable levels of cell‐associated CEA. The routine titration of cytotoxic antibody against these established cell cultures may provide meaningful information on the host's immune response to colorectal neoplasms.