Figure 1

Endometrial folding during pig conceptus attachment. Following rapid trophoblast elongation on Day 12 of pregnancy, conceptus attachment to the endometrial surface epithelium induces a localized increase in endometrial surface folding on Day 14 of pregnancy (A). Local conceptus release of IL1BE, IFN, estrogens or combination of the factors released by the conceptus to alter the uterine surface architecture (attachment and folding) to increase the surface area needed to support the epithiochorial type of placentation in the pig and alter immune cell trafficking to the uterine surface (B). (Tr = trophectoderm, LE = luminal epithelium, arrows = lymphocytes in the underlying stratum compactum).