STUDY QUESTION Is the innate immunity system active in early human embryo development? SUMMARY ANSWER The pattern recognition receptors and innate immunity Toll-like receptor (TLR) genes are widely expressed in preimplantation human embryos and the pathway appears to be active in response to TLR ligands. WHAT IS KNOWN ALREADY Early human embryos are highly sensitive to their local environment, however relatively little is known about how embryos detect and respond to specific environmental cues. While the maternal immune response is known to be key to the establishment of pregnancy at implantation, the ability of human embryos to detect and signal the presence of pathogens is unknown. STUDY DESIGN, SIZE, DURATION Expression of TLR family and related genes in human embryos was assessed by analysis of published transcriptome data (n = 40). Day 5 (D-5) human embryos (n = 25) were cultured in the presence of known TLR ligands and gene expression and cytokine production measured compared to controls. PARTICIPANTS/MATERIALS, SETTING, METHODS Human embryos surplus to treatment requirements were donated with informed consent from several ART centres. Embryos were cultured to Day 6 (D-6) in the presence of the TLR3 and TLR5 ligands Poly (I: C) and flagellin, with gene expression measured by quantitative PCR and cytokine release into medium measured using cytometric bead arrays. MAIN RESULTS AND THE ROLE OF CHANCE TLR and related genes, including downstream signalling molecules, were expressed variably at all human embryo developmental stages. Results showed the strongest expression in the blastocyst for TLRs 9 and 5, and throughout development for TLRs 9, 5, 2, 6 and 7. Stimulation of Day 5 blastocysts with TLR3 and TLR5 ligands Poly (I: C) and flagellin produced changes in mRNA expression levels of TLR genes, including the hyaluronan-mediated motility receptor (HMMR), TLR5, TLR7, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and monocyte chemoattractant Protein-1 (MCP-1) (P < 0.05, P < 0.001 compared to unstimulated controls), and release into culture medium of cytokines and chemokines, notably IL8 (P = 0.00005 and 0.01277 for flagellin and Poly (I: C), respectively). LIMITATIONS, REASONS FOR CAUTION This was a descriptive and experimental study which suggests that the TLR system is active in human embryos and capable of function, but does not confirm any particular role. Although we identified embryonic transcripts for a range of TLR genes, the expression patterns were not always consistent across published studies and expression levels of some genes were low, leaving open the possibility that these were expressed from the maternal rather than embryonic genome. WIDER IMPLICATIONS OF THE FINDINGS This is the first report of the expression and activity of a number of components of the innate immunity TLR system in human embryos. Understanding the role of TLRs during preimplantation human development may be important to reveal immunological mechanisms and potential clinical markers of embryo quality and pregnancy initiation during natural conception and in ART. STUDY FUNDING/COMPETING INTEREST(S) This work was funded by the Ministry of Higher Education, The State of Libya, the UK Medical Research Council, and the NIHR Local Comprehensive Research Network and NIHR Manchester Clinical Research Facility and the European Union’s Horizon 2020 Research and Innovation Programmes under the Marie Skłodowska-Curie Grant Agreement No. 812660 (DohART-NET). In accordance with H2020 rules, no new human embryos were sacrificed for research activities performed from the EU funding, which concerned only in silico analyses of recorded time-lapse and transcriptomics datasets. None of the authors has any conflict of interest to declare. TRIAL REGISTRATION NUMBER n/a.

中文翻译：

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Toll 样受体在植入前人类胚胎中的表达和活性表明了先天免疫的新作用

研究问题 先天免疫系统在人类胚胎早期发育中是否活跃？总结答案 模式识别受体和先天免疫 Toll 样受体 (TLR) 基因在人类胚胎着床前广泛表达，并且该途径似乎对 TLR 配体有反应。已知情况 早期人类胚胎对其当地环境高度敏感，但对于胚胎如何检测和响应特定环境线索知之甚少。虽然已知母体免疫反应是在植入时建立妊娠的关键，但人类胚胎检测和发出病原体存在信号的能力尚不清楚。研究设计、大小、持续时间 TLR 家族和相关基因在人类胚胎中的表达通过分析已发表的转录组数据（n = 40）进行评估。第 5 天 (D-5) 人类胚胎 (n = 25) 在存在已知 TLR 配体的情况下进行培养，并与对照相比测量基因表达和细胞因子产生。参与者/材料、环境、方法 超出治疗要求的人类胚胎是在几个 ART 中心的知情同意下捐赠的。在存在 TLR3 和 TLR5 配体 Poly (I: C) 和鞭毛蛋白的情况下，将胚胎培养至第 6 天 (D-6)，通过定量 PCR 测量基因表达，并使用细胞计数珠阵列测量细胞因子释放到培养基中。主要结果和机会 TLR 和相关基因（包括下游信号分子）的作用在所有人类胚胎发育阶段都有不同的表达。结果显示，TLR 9 和 5 在胚泡中表达最强，TLR 9、5、2、6 和 7 在整个发育过程中表达最强。用 TLR3 和 TLR5 配体 Poly (I: C) 和鞭毛蛋白刺激第 5 天的囊胚导致 TLR 基因的 mRNA 表达水平发生变化，包括透明质酸介导的运动受体 (HMMR)、TLR5、TLR7、核因子 kappa-轻链-活化 B 细胞 (NF-κB) 和单核细胞趋化蛋白 1 (MCP-1) 的增强剂（与未受刺激的对照相比，P < 0.05，P < 0.001），并释放到培养基中的细胞因子和趋化因子，特别是 IL8 （鞭毛蛋白和聚（I：C）分别为 P = 0.00005 和 0.01277）。限制，谨慎的原因 这是一项描述性和实验性研究，表明 TLR 系统在人类胚胎中是活跃的并且能够发挥作用，但没有证实任何特定的作用。虽然我们鉴定了一系列 TLR 基因的胚胎转录本，在已发表的研究中，表达模式并不总是一致的，并且一些基因的表达水平很低，这使得这些基因表达来自母体而不是胚胎基因组的可能性仍然存在。研究结果的更广泛意义 这是关于人类胚胎中先天免疫 TLR 系统的许多成分的表达和活性的第一份报告。了解 TLR 在胚胎植入前人类发育过程中的作用对于揭示自然受孕和 ART 期间胚胎质量和妊娠开始的免疫机制和潜在临床标志物可能很重要。研究资助/竞争兴趣 这项工作由利比亚高等教育部、英国医学研究委员会、以及 NIHR 地方综合研究网络和 NIHR 曼彻斯特临床研究机构以及欧盟根据 Marie Skłodowska-Curie 资助协议第 812660 号 (DohART-NET) 开展的 Horizo​​n 2020 研究和创新计划。根据 H2020 规则，欧盟资助的研究活动不会牺牲任何新的人类胚胎，这仅涉及对记录的延时和转录组数据集的计算机分析。没有一个作者有任何利益冲突要声明。试用注册号 不适用。这仅涉及记录的延时和转录组数据集的计算机分析。没有一个作者有任何利益冲突要声明。试用注册号 不适用。这仅涉及记录的延时和转录组数据集的计算机分析。没有一个作者有任何利益冲突要声明。试用注册号 不适用。