Trophoblast MHC-I: Trigger for Immune-Mediated Rejection of Cloned Bovine Fetuses

描述（由申请人提供）：免疫介导流产是妇女妊娠失败的一个重要原因，尽管人们对其了解甚少，而且常常未被认识到。自然流产和与胎盘异常相关的先兆子痫，在通过体外受精（IVF）等辅助生殖技术建立的人类和牛妊娠中发生的频率增加。我们的长期目标是了解免疫介导流产和胎盘功能不全的免疫学基础，并制定和测试策略来下调对该概念的免疫反应。基于牛体细胞核移植（SCNT）妊娠中胎盘发育不足和胎儿丢失的常规发生，将使用一种独特的牛免疫介导的流产和胎盘功能不全模型。几个观察结果支持该模型的有效性：(1)与对照组胎儿相比，SCNT胎儿的胎盘滋养细胞在妊娠早期表达经典的主要组织相容性复合体I类（MHC-I）抗原，(2)T淋巴细胞在SCNT受体子宫间质中积累，(3)MHC纯合子SCNT胎儿比MHC杂合子胎儿表现更好。这些发现表明，SCNT妊娠的大部分胎儿丢失是由于免疫介导的流产。该项目基于妊娠早期滋养细胞MHC-I表达不当会导致免疫介导的流产或胎盘功能不全的一般假设。MHC-I蛋白的不适当表达可能包括经典MHC-I蛋白表达增加，非经典MHC-I蛋白表达减少或两者兼而有之。该提案的具体目标是：(1)在妊娠第32 - 34天制备8-10个MHC-I相容的SCNT， 8-10个MHC-I不相容的SCNT和8-10个对照妊娠用于子宫和胎盘组织收集，并比较三种妊娠类型中滋养细胞MHC-I表达、子宫白细胞群和子宫和胎盘基因表达；(2)比较SCNT胚胎移植到MHC-I兼容和不兼容的受体奶牛的胚胎死亡率，以确定是否可以通过消除抗原MHC-I触发来避免免疫介导的流产。本项目将阐明正常妊娠和异常妊娠中胎盘与子宫免疫系统相互作用的功能基因组学。功能基因组学和形态学数据将被整合，以创建一个完整的图像细胞和分子事件涉及一个重要的临床问题：免疫介导流产。该项目还将直接测试怀孕早期异常MHC-I表达引发免疫介导流产的假设，这是一个长期存在的假设，但由于缺乏合适的动物模型，从未得到充分的测试。公共卫生相关性：哺乳动物的胎儿必须说服其母亲的免疫系统接受它。当胎儿不能诱导母体耐受时，结果要么是免疫介导的流产，要么是胎盘异常的发展，这可能导致妊娠后期的问题。随着体外受精等辅助生殖技术的使用，人类和牛中免疫介导的流产和胎盘功能不全的发生率大大增加。在本研究中，牛体细胞核移植妊娠通常具有较高的妊娠早期自然流产率，将用于研究胚胎在体外操作时母体和母体免疫系统之间的通信如何中断。

DESCRIPTION (provided by applicant): Immune-mediated abortion is an important, although poorly understood and often unrecognized, cause of pregnancy failure in women. Both spontaneous abortion and preeclampsia, which is associated with abnormal placentation, occur at increased frequency in human and bovine pregnancies established by assisted reproductive technologies such as in vitro fertilization (IVF). Our long-term goals are to understand the immunological basis of immune-mediated abortion and placental insufficiency, and to develop and test strategies to down-regulate the immune response to the conceptus. A unique bovine model of immune- mediated abortion and placental insufficiency based on the routine occurrence of inadequate placental development and fetal loss in bovine somatic cell nuclear transfer (SCNT) pregnancies will be used. Several observations support the validity of this model: (1) placental trophoblast cells of SCNT fetuses, in contrast to control fetuses, express classical major histocompatibility complex class I (MHC-I) antigens early in pregnancy, (2) T lymphocytes accumulate in the uterine stroma of SCNT recipients, and (3) MHC homozygous SCNT fetuses fare better than MHC heterozygous fetuses. These findings suggest that much of the fetal loss in SCNT pregnancies is due to immune-mediated abortion. This project is based on the general hypothesis that inappropriate trophoblast MHC-I expression early in pregnancy will induce immune-mediated abortion or placental insufficiency. Inappropriate expression of MHC-I proteins may consist of increased expression of classical MHC-I proteins, decreased expression of non-classical MHC-I proteins or a combination of the two. The proposal's specific aims are: (1) produce 8-10 MHC-I compatible SCNT, 8-10 MHC-I incompatible SCNT and 8-10 control pregnancies for collection of uterine and placental tissues on days 32 to 34 of pregnancy, and compare trophoblast MHC-I expression, uterine leukocyte populations and uterine and placental gene expression in the three types of pregnancies; and (2) compare embryonic mortality rates of SCNT embryos transferred into MHC-I compatible and incompatible recipient cows to determine if immune-mediated abortion can be avoided by eliminating the antigenic, MHC-I trigger. This project will elucidate the functional genomics of the cross-talk between the placenta and uterine immune system in normal and abnormal pregnancies. Functional genomics and morphological data will be integrated to create a complete picture of the cellular and molecular events involved in an important clinical problem: immune-mediated abortion. The project will also directly test the hypothesis that abnormal MHC-I expression early in pregnancy triggers immune-mediated abortion, a long-standing hypothesis that has never been adequately tested because of lack of a suitable animal model. PUBLIC HEALTH RELEVANCE: A mammalian conceptus must convince its mother's immune system to accept it. When the fetus fails to induce maternal tolerance, the outcome is either immune-mediated abortion or the development of abnormal placentation that can result in problems later in pregnancy. The incidence of immune-mediated abortion and placental insufficiency in both humans and cattle are greatly increased with the use of assisted reproductive technologies such as in vitro fertilization. In this study bovine somatic cell nuclear transfer pregnancies, which normally have a high rate of first trimester spontaneous abortions, will be used to study how communications between the conceptus and maternal immune system break down when embryos are manipulated in vitro.