• Oncofetal antigen;
  • tumor immunity;
  • suppressor cell

ABSTRACT: Previous studies employing ultraviolet light-induced (UV-induced) and methylcholanthrene-induced (MCA-induced) tumors have elucidated the presence of three functionally denned groups of tumor antigens. One is the tumor-specific transplantation antigens (TSTA), which represent the most potent tumor-rejection antigens. The second is the tumor-associated transplantation antigens (TATA), which appears to be etiology-dependent (ultraviolet light-UV-or methylcholanthrene-MCA) and is capable of acting as a rejection antigen following hyperimmunization. The third is the tumor-associated antigens (TAA) which, to date, has only been defined by in vitro assays. The TAA appear to be present on all murine tumors tested. We feel that the TAA are functionally related to fetal antigens. In these experiments, cytotoxic T lymphocytes (CTL) generated from the popliteal lymph nodes of C3H mice immunized with a C3H, UV-induced tumor (RD-1024) were capable of causing specific lysis of not only the immunizing tumor but also of fetal fibroblasts (FFB) and placental cells (PC) obtained from syngeneic C3H × C3H matings. In cold-cell inhibition experiments, unlabeled placental cells could abolish specific lysis of labeled placental cell targets, fetal fibroblast targets, and secondary tumor targets (LR80, a MCA-induced tumor) while not inhibiting lysis of the immunizing tumor. Placental cells and fetal fibroblasts from 12-day to 14-day syngeneic C3H pregnancies were capable of eliciting a CTL response by footpad immunization of virgin C3H female mice. Anti-FFB or anti-PC CTL were capable of killing all tumors tested (UV-induced or MCA-induced) and were without H-2 restriction as demonstrated by specific lysis of a BALB/c tumor. These results indicate that antigenic determinants present on 12-day to 14-day fetal and placental cells satisfy the functional definition of the TAA.