In this review, we discuss the often overlooked tissue-resident fetal macrophages, Hofbauer cells, which are found within the chorionic villi of the human placenta. Hofbauer cells have been shown to have a phenotype associated with regulatory and anti-inflammatory functions. They are thought to play a crucial role in the regulation of pregnancy and in the maintenance of a homeostatic environment that is crucial for fetal development. Even though the numbers of these macrophages are some of the most abundant immune cells in the human placenta, which are sustained throughout pregnancy, there are very few studies that have identified their origin, their phenotype, and functions and why they are maintained throughout gestation. It is not yet understood how Hofbauer cells may change in function throughout normal pregnancy, and especially in those complicated by maternal gestational diabetes, preeclampsia, and viral infections, such as Zika, cytomegalovirus, and human immunodeficiency virus. We review what is known about the origin of these macrophages and explore how common complications of pregnancy dysregulate these cells leading to adverse birth outcomes in humans. Our synthesis sheds light on areas for human studies that can further define these innate regulatory cells.

中文翻译：

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胎盘巨噬细胞的难以捉摸的作用：霍夫鲍尔细胞。

在这篇综述中，我们讨论了经常被忽略的驻留在组织中的胎儿巨噬细胞霍夫鲍尔细胞，其在人类胎盘的绒毛膜绒毛中发现。已经显示霍夫鲍尔细胞具有与调节和抗炎功能相关的表型。人们认为它们在调节怀孕和维持对胎儿发育至关重要的体内环境中起着至关重要的作用。尽管这些巨噬细胞的数量是人类胎盘中最丰富的免疫细胞，在整个妊娠过程中都会持续存在，但很少有研究能够确定它们的来源，表型和功能以及为什么在整个妊娠过程中都能保持这种状态。目前尚不清楚霍夫鲍尔细胞在正常怀孕期间如何改变功能，尤其是在那些合并有孕妇妊娠糖尿病，先兆子痫和病毒感染（例如寨卡病毒，巨细胞病毒和人类免疫缺陷病毒）的患者中。我们回顾了有关这些巨噬细胞起源的已知信息，并探讨了妊娠的常见并发症如何使这些细胞异常调节，从而导致人类不良的出生结局。我们的合成为可以进一步定义这些先天调节细胞的人类研究领域提供了启示。