胎儿携带二分之一父方基因和二分之一母方基因在母体宫内,可视为移入母体内的半异体移植物,但成功妊娠的胎儿却不被母体排斥,这是由于妊娠期的母体存在免疫耐受。其中胎盘的滋养层和底蜕膜上有许多免疫因子可使胎儿得以逃避母体的免疫攻击:胎盘自身的机械性屏障作用也起重要作用;HLA-G,E可抑制妊娠时T细胞及NK细胞的表达;补体调节蛋白可通过干扰膜攻击复合物的形成而利于母胎免疫;母体Treg细胞在正常妊娠时的表达量高于非妊娠时的表达量,也参与了母胎免疫耐受。 One half of the fetus carrying the parent gene and one half of the mother gene in the mother’s uterus can be considered as a transplanted hemi-allograft within the mother, but a successful fetus is not rejected by the mother because the mother during pregnancy There is immune tolerance. Placenta trophoblast and decidua on the bottom of many immune factors can make the fetus to escape the mother’s immune attack: the placenta itself also plays an important role in the mechanical barrier; HLA-G, E can inhibit pregnancy T cells and NK cells ; Complement regulatory protein can interfere with the formation of membrane attack complex to facilitate maternal immunization; maternal Treg cells in normal pregnancy expression is higher than non-pregnancy expression, also involved in the immune tolerance of the mother.