胚胎自受精卵到囊胚均包绕着致密的透明带,只有一些小分子物质能够进出胚胎。因此,在囊胚或胚胎孵出之前胚胎与母体的免疫系统基本隔离,直到囊胚在子宫孵出,胚胎才与母体通过滋养细胞直接接触。发生在母胎界面的免疫反应使胚胎能够成功侵入子宫内膜并使子宫内膜的血管发生重铸, Embryos from the fertilized egg to the blastocysts are surrounded by a dense zona pellucida, only some small molecules can enter and exit the embryo. Therefore, the embryo and the mother’s immune system are substantially isolated prior to the blastocyst or embryo hatching until the blastocyst is hatched in the womb, and the embryo contacts the mother directly through the trophoblast. The immune response that occurs at the maternal-fetal interface allows the embryo to successfully invade the endometrium and recapitulate the endometrial vessels,