Major H-2 and non-H-2 differences between parental strains prevent occurrence of fetectomy-induced yolk sac teratomas

We performed fetectomies, according to the technique of Sobis and Vandeputte for the surgical induction of teratomas, in female mice mated with syngeneic, congeneic, or allogeneic males. Benign teratomas including multiple tissue formations derived from the three germinal layers were observed only in syngeneic pregnancies. In addition, the frequency of induced teratomas was lower in some strains (A/Sn, A . By, and A . SW) than in others (A . CA, B10 . A, C57BL/6, and C3H/He). This variable frequency may be explained by postulating the existence of fetal, strain-specific antigens. In hybrid pregnancies we observed no complete teratomas, but only cartilaginous formations considered as vestiges of early teratoma differentiation. The maternal immune reaction against either major (H-2) or minor (non-H-2) paternal histocompatibility antigens was sufficient to suppress the development of teratomas from visceral yolk sac of hybrid fetuses. This reaction, including both a serological and a cell-mediated activity, was measured in vitro. These results suggest that a maternal immune reaction is not efficiently altered by the normal first half of pregnancy and that differentiated teratoma tissues express the paternal antigens sufficiently to induce their immune rejection.