Maternal immunostimulation of a teratocarcinoma-derived cell line, TerCs

Since murine teratocarcinomas and early embryos are known to share cell surface antigens, we investigated the possibility of maternal immune responses to normal pregnancy using teratocarcinoma-derived cell lines as targets. We found that an adherent cell population from both the spleen and peritoneum of syngeneically mated 129/SvSl pregnant females stimulated the uptake of [125I]iododeoxyuridine ( [125I]IUdR) by a teratocarcinoma-derived cell line, TerCs in vitro. Adherent cells from multiparous females did not stimulate the growth of other tumor cell lines. However, levels of natural anti-tumor activity detected in peritoneal cell populations of 129/SvSl virgin females were greatly reduced during pregnancy. Peritoneal cells from multiparous females with growth-stimulating activity were retained on nylon-wool columns and not eliminated by treatment with anti-theta antiserum and complement. Peritoneal cells from virgin females, treated with anti-theta antiserum and complement to eliminate cytotoxic lymphocytes, gained the ability to stimulate the uptake of [125I]IUdR by TerCs cells. [125I]IUdR uptake by cultured normal mouse blastocysts was significantly enhanced by peritoneal cells from multiparous females, while cells from age-matched virgin females had no effect. These results suggest that changes in immunocyte populations occur during pregnancy in the mouse; these changes could promote the growth of the embryo in utero.