Immunological relationships between murine surrogate mothers and transplanted embryos, as studied by local GVH reactivity

C57BL/Ks (H-2 d) female mice were transplanted with early (stage 2) embryos of the A/J (H-2 a) strain. Spleens from mice exhibiting successful pregnancies were tested at days 16 to 19 of gestation in a local graft versus host (LGVH) assay using (C57BL/Ks × A/J)F1 recipients and proved to be significantly more reactive than virgin controls or mice carrying transplanted syngeneic fetuses. This increased reactivity was specific for the transplanted embryo's strain. Other controls included donors with semi-allogeneic (F1) transplanted fetuses and females naturally pregnant by allogeneic males which did not give reactions significantly different from virgin control spleen cells. Para-aortic lymph node cells (PALN) obtained from the same A/J embryo-transplanted females showed a strong T suppressive activity both on their own spleen cell (SC) reaction as well as on the reaction obtained with virgin SC. This suppressive activity also appeared to be embryo-strain specific. Serological tests revealed the presence of mast cell-degranulating (anaphylactic) antibodies but not of hemagglutinating or complement-fixing cytotoxic activities. The A/J offspring obtained after embryo transfer to C57BL/Ks females presented at the age of two months significantly lower LGVH reactivity against the surrogate mother's strain. The differences in the responsiveness of the mice transplanted with allogeneic embryos compared with those with conventional pregnancies are discussed.