Antibodies to antigens on teratocarcinoma cells are associated with parity in mice

Previous studies have demonstrated that the maternal host responds immunologically to antigens of the fetus, including oncofetal antigens (OFA). However, until now, the OFA that have been studied are those associated with the postimplantation embryo. In this paper we provide evidence that the maternal host also responds immunologically to antigens associated with the mouse teratocarcinoma (TC) cell lines F9 and PYS-2, which have been established as models for the preimplantation embryo. In a solid-phase radioimmunoassay using cell membrane extracts as antigen and 125I-protein A to detect binding antibodies, sera from parous C57BL/6 mice had a significantly greater reactivity than sera from age-matched virgin animals to F9 but not PYS-2, splenocyte or fibroblast antigen extracts. This finding was confirmed by surface immunofluorescence (IF) with fluorescein-labeled anti-mouse IgG. IF also detected a small number of multiparous mice with antibodies to PSY-2. Positive serum reactivity did not correlate directly with the number of previous litters. These TC cell lines express at least 2 OFA, F9 and Endo, which are found on preimplantation embryos and sperm, and preimmunization of female mice with F9 cells has been shown to reduce fertility. The parity-induced antibodies detected in this study could react with embryos at early stages of development and contribute to the natural decrease in litter size which occurs in mice after the second litter.