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

描述（由申请人提供）：免疫介导的流产是一个重要的，虽然了解甚少，往往不承认，在妇女妊娠失败的原因。与异常胎盘形成相关的自然流产和先兆子痫在通过辅助生殖技术（如体外受精（IVF））建立的人类和牛妊娠中发生频率增加。我们的长期目标是了解免疫介导的流产和胎盘功能不全的免疫学基础，并开发和测试策略，下调对孕体的免疫反应。将使用一种独特的免疫介导的流产和胎盘功能不全的牛模型，该模型基于牛体细胞核移植（SCNT）妊娠中胎盘发育不足和胎仔丢失的常规发生。几个观察结果支持该模型的有效性：（1）与对照胎儿相比，SCNT胎儿的胎盘滋养层细胞在妊娠早期表达经典的主要组织相容性复合物I类（MHC-I）抗原，（2）T淋巴细胞在SCNT受体的子宫基质中积累，（3）MHC纯合的SCNT胎儿比MHC杂合的胎儿更好。这些研究结果表明，SCNT妊娠中的大部分胎儿丢失是由于免疫介导的流产造成的。该项目基于妊娠早期滋养层MHC-I表达不当将诱导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由经典MHC-I蛋白的表达增加、非经典MHC-I蛋白的表达减少或两者的组合组成。（1）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，用于收集妊娠32 - 34天的子宫和胎盘组织，并比较三种妊娠类型的滋养层MHC-I表达、子宫白细胞群以及子宫和胎盘基因表达;和（2）比较移植到MHC-I相容和不相容受体母牛中的SCNT胚胎的胚胎死亡率，以确定是否可以通过消除抗原性MHC-I触发物来避免免疫介导的流产。本计画将阐明正常与异常妊娠中胎盘与子宫免疫系统间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，以创建一个重要的临床问题：免疫介导的流产所涉及的细胞和分子事件的全貌。该项目还将直接测试怀孕早期异常MHC-I表达引发免疫介导的流产的假设，这是一个长期存在的假设，由于缺乏合适的动物模型而从未得到充分的测试。公共卫生相关性：哺乳动物的胚胎必须说服母亲的免疫系统接受它，当胎儿不能诱导母亲的耐受性时，结果要么是免疫介导的流产，要么是胎盘形成异常，这可能导致怀孕后期的问题。人类和牛免疫介导的流产和胎盘功能不全的发生率随着体外受精等辅助生殖技术的使用而大大增加。在这项研究中，牛体细胞核移植妊娠，通常有一个高利率的第一个三个月自然流产，将被用来研究如何之间的通信概念和母体免疫系统打破胚胎在体外操作时。

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.