• Oncofetal antigens;
  • antitumor immunity;
  • T cell-mediated immune response

ABSTRACT: The presence of fetal antigens on a wide variety of tumors has been well-documented it has been attributed, for the most part, to de-repression of genes normally operative in the early stages of embryonic development. Controversy still exists, however, about the role of fetal antigens in antitumor immunity. It is not clear whether the tumor inhibition shown in some systems is due to an immune response. In the present study, conducted in a weakly immunogenic Lewis T241 fibrosarcoma, syngeneic for C57B1/ 6J mice, immunization of normal mice with syneneic fetal cells resulted in striking inhibition of growth and metastases of tumors. On the other hand, immunization with syngeneic normal, adult spleen cells or with allogeneic A/J fetal cells did not inhibit tumor growth or metastases. Mice that had gone through single pregnancy also showed inhibition in tumor growth and metastases. Immunization of female mice with syngeneic tumor cells or fetal cells, prior to pregnancy, resulted in a high incidence of fetal death in these mice. Further studies showed that tumor inhibitory response evoked by fetal cell immunization was due to fetal antigens the male-specific HY antigen was not responsible for antitumor response. When tumor cells were mixed with spleen cells from fetal antigen-immunized mice and then injected into normal mice (Winn neutralization assay), significant inhibition of tumor growth and metastases was observed. In this assay, mixing tumor cells with syngeneic fetal cells, normal adult spleen cells, or spleen cells from C57 mice immunized with allogeneic fetal cells did not inhibit the tumor growth or metastases. These results show that inhibition in tumor growth and metastases, following fetal cell immunization, was due to a specific immune response to the oncofetal antigens involved. Analysis of effector cells showed them to be T cells of Lyt-1+ and Lyt-2 phenotype.