A carcinofetal antigen located on the membrane of cells from rat intestinal carcinoma in culture.

Heteroantisera were produced in rabbits by immunization with cultivated cells from rat intestinal carcinomas. The sera were made specific by in vivo absorption in syngeneic rats. On immunofluorescence, these sera recognized a membrane-associated antigen common to five different intestinal carcinomas and to fetal intestine. The antigen was not detected in noncancerous adult intestine, nonintestinal fetal tissues, or three nonintestinal tumor cell lines.