Immune Gene Regulation in Human Trophoblast Cells

描述（由申请人提供）：成功的妊娠要求抗原性不同的胎儿避免受到母亲免疫系统的攻击。胎盘滋养层细胞（TBCs）是唯一与母体血液直接接触的囊胚源性细胞，它们在调节母体对孕体的免疫反应中起重要作用。干扰素-3（IFN-3）是一种促炎细胞因子，在多种细胞过程中发挥关键作用，包括诱导细胞凋亡、抑制细胞增殖和启动适应性免疫反应。重要的是，IFN-3在正常妊娠期间存在于子宫中。来自所有孕龄的人TBCs对IFN-3介导的细胞凋亡和多态性MHC抗原表达的激活都有抗性。这表明人类TBCs已经进化出逃避IFN-3有害作用的机制。对IFN-3的应答是通过JAK-STAT-1途径激活转录介导的。重要的是，多种病原体通过破坏响应于IFN-3的JAK-STAT途径来逃避宿主免疫应答。对IFN-3的细胞应答的幅度和持续时间由正作用JAK和STAT与负作用蛋白酪氨酸磷酸酶（PTP）和细胞因子信号传导抑制剂（SOCS）的活性之间的平衡决定。调节IFN-3信号传导的PTP是组成型活性的，但在细胞暴露于IFN-3后瞬时失活。PTP的失活导致JAK的最大活化和细胞因子信号的传播。我们以前证明，IFN-3的反应被抑制在人类原发性长期TBC和TBC衍生的绒毛膜癌（CC）细胞的PTP介导的抑制JAK。我们的动力学研究表明，即使在IFN-3治疗的早期时间点，TBC中的JAK也被抑制。这些结果表明，PTP在暴露于IFN-3的TBC中未失活。我们最近还证明了SOCS-1和SOCS-3在TBCs中组成型表达。因此，在特定目的I中，我们将研究1）PTP在IFN-3处理的TBC中与其他细胞类型相比是否受到差异调节，以及2）SOCS-1和SOCS-3在调节TBC中IFN-3应答中的作用。我们的集体研究表明，JAK的抑制是TBC抑制IFN-3应答的主要机制，但它们没有解决异常JAK或STAT-1激活对滋养层细胞对IFN-3应答的影响。最近的研究确定了原因不明的妊娠丢失与JAK-2的组成性活性（CA）突变体之间的关联。此外，STAT-1在肿瘤的免疫监视中起重要作用。因此，在特异性目的II中，我们将研究JAK和STAT-1的CA突变体对TBC IFN-3应答的影响。目前尚不清楚TBCs中IFN-3信号的抑制是否发生在整个妊娠期，或仅限于特定的妊娠期。因此，在特定目标III中，我们将检查第一，第二和第三孕期TBCs中的IFN-3应答。我们的研究将为了解孕体如何逃避对IFN-3的有害反应，以及TBCs中异常的IFN-3信号传导如何导致妊娠并发症提供见解。公共卫生相关性：最近的研究表明，妊娠是一种受控炎症状态，胎盘IFN-3水平的改变在胎盘病理学与生殖成功中起着关键作用。我们提出的研究将阐明TBCs如何补偿在正常妊娠期间和感染后子宫中促炎性IFN-3的存在，通过全面分析TBCs调节对IFN-3反应的分子机制。因此，我们的研究将提供有关孕体如何逃避对IFN-3的潜在有害反应，以及TBCs中异常细胞因子信号传导如何导致妊娠并发症的见解。这项工作对肿瘤免疫也有重要意义，因为肿瘤细胞对IFN-3的反应性丧失在肿瘤免疫逃避中起着至关重要的作用。

DESCRIPTION (provided by applicant): Successful pregnancy requires that the antigenically disparate fetus avoid attack by the mother's immune system. Placental trophoblast cells (TBCs) are the only blastocyst-derived cells in direct contact with maternal blood, and they play essential roles in modulating maternal immune responses to the conceptus. Interferon-3 (IFN-3) is a pro-inflammatory cytokine that plays critical roles in diverse cellular processes, including induction of apoptosis, inhibition of cell proliferation and initiation of adaptive immune responses. Importantly, IFN-3 is present in the uterus during normal pregnancy. Human TBCs from all gestational ages examined are resistant to both IFN-3-mediated apoptosis, and activation of polymorphic MHC antigen expression. This suggests that human TBCs have evolved mechanisms to evade the harmful effects of IFN-3. Responses to IFN-3 are mediated by activation of transcription through the JAK-STAT-1 pathway. Importantly, multiple pathogens evade host immune responses by disrupting the JAK-STAT pathway in response to IFN-3. The magnitude and duration of cellular responses to IFN-3 are dictated by the equilibrium between the activities of the positively acting JAKs and STATs, versus negatively acting protein tyrosine phosphatases (PTPs) and suppressors of cytokine signaling (SOCS). The PTPs that regulate IFN-3 signaling are constitutively active, but are transiently inactivated following exposure of cells to IFN-3. Inactivation of the PTPs results in maximal activation of the JAKs and propagation of the cytokine signal. We previously demonstrated that IFN-3 responses are inhibited in human primary term TBCs and TBC-derived choriocarcinoma (CC) cells by PTP-mediated repression of the JAKs. Our kinetic studies demonstrate that JAKs are inhibited in TBCs even at early time points of IFN-3 treatment. These results suggest that the PTPs are not inactivated in TBCs exposed to IFN-3. We also recently demonstrated that SOCS-1 and SOCS-3 are constitutively expressed in TBCs. Thus, in Specific Aim I, we will investigate 1) whether PTPs are differentially regulated in IFN-3-treated TBCs versus other cell types, and 2) the roles of SOCS-1 and SOCS-3 in regulating IFN-3 responses in TBCs. Our collective studies suggest that inhibition of the JAKs is the primary mechanism by which TBCs suppress IFN-3 responses, but they do not address the consequences of aberrant JAK or STAT-1 activation on trophoblastic responses to IFN-3. Recent studies identified an association between unexplained pregnancy loss and a constitutively active (CA) mutant of JAK-2. Moreover, STAT-1 plays an essential role in immunosurveillance of tumors. Thus, in Specific Aim II, we will investigate the effects of CA mutants of the JAKs and STAT-1 on TBC IFN-3 responses. It is currently unclear whether inhibition of IFN-3 signaling in TBCs occurs throughout gestation, or is restricted to specific trimesters of pregnancy. Thus, in Specific Aim III we will examine IFN-3 responses in 1st, 2nd and 3rd trimester TBCs. Our studies will provide insights into how the conceptus evades deleterious responses to IFN-3, and how aberrant IFN-3 signaling in TBCs may lead to complications of pregnancy. PUBLIC HEALTH RELEVANCE: Recent studies suggest that pregnancy is a state of controlled inflammation, and that alterations in placental levels of IFN-3 play a critical role in placental pathology versus reproductive success. Our proposed studies will shed light on how TBCs compensate for the presence of pro-inflammatory IFN-3 in the uterus during normal pregnancy and following infection by providing a comprehensive analysis of the molecular mechanism(s) by which TBCs regulate responses to IFN-3. Thus, our studies will provide insights into how the conceptus evades potentially deleterious responses to IFN-3, and how aberrant cytokine signaling in TBCs may lead to pregnancy complications. This work also has important implications for tumor immunity, for loss of responsiveness to IFN-3 by tumor cells plays an essential role in tumor immunoevasion.