Table_14_ERAP, KIR, and HLA-C Profile in Recurrent Implantation Failure.docx

The mother’s uterine immune system is dominated by uterine natural killer (NK) cells during the first trimester of pregnancy. These cells express killer cell immunoglobulin-like receptors (KIRs) of inhibitory or activating function. Invading extravillous trophoblast cells express HLA-C molecules, and both maternal and paternal HLA-C allotypes are presented to KIRs. Endoplasmic reticulum aminopeptidase 1 (ERAP1) and 2 (ERAP2) shape the HLA class I immunopeptidome. The ERAPs remove N-terminal residues from antigenic precursor peptides and generate optimal-length peptides to fit into the HLA class I groove. The inability to form the correct HLA class I complexes with the appropriate peptides may result in a lack of immune response by NK cells. The aim of this study was to investigate the role of ERAP1 and ERAP2 polymorphisms in the context of KIR and HLA-C genes in recurrent implantation failure (RIF). In addition, for the first time, we showed the results of ERAP1 and ERAP2 secretion into the peripheral blood of patients and fertile women. We tested a total of 881 women. Four hundred ninety-six females were patients who, together with their partners, participated in in vitro fertilization (IVF). A group of 385 fertile women constituted the control group. Women positive for KIR genes in the Tel AA region and HLA-C2C2 were more prevalent in the RIF group than in fertile women (p/pcorr. = 0.004/0.012, OR = 2.321). Of the ERAP polymorphisms studied, two of them (rs26653 and rs26618) appear to affect RIF susceptibility in HLA-C2-positive patients. Moreover, fertile women who gave birth in the past secreted significantly more ERAP1 than IVF women and control pregnant women (p < 0.0001 and p = 0.0005, respectively). In the case of ERAP2, the opposite result was observed; i.e., fertile women secreted far less ERAP2 than IVF patients (p = 0.0098). Patients who became pregnant after in vitro fertilization embryo transfer (IVF-ET) released far less ERAP2 than patients who miscarried (p = 0.0032). Receiver operating characteristic (ROC) analyses indicate a value of about 2.9 ng/ml of ERAP2 as a point of differentiation between patients who miscarried and those who gave birth to a healthy child. Our study indicates that both ERAP1 and ERAP2 may be involved in processes related to reproduction.

妊娠早期阶段，母体子宫免疫系统以子宫自然杀伤细胞（uterine natural killer, NK）为主导。这类细胞表达兼具抑制与激活功能的杀伤细胞免疫球蛋白样受体（killer cell immunoglobulin-like receptors, KIRs）。侵袭性绒毛外滋养层细胞可表达HLA-C分子，父母双方的HLA-C同种异型均可被呈递给KIRs。内质网氨肽酶1（endoplasmic reticulum aminopeptidase 1, ERAP1）与内质网氨肽酶2（ERAP2）可塑造HLA I类免疫肽组：二者可对抗原前体肽的N端残基进行酶切，生成长度适配HLA I类分子沟槽的最优肽段。若无法与特异性肽段形成正常的HLA I类复合物，则可能导致NK细胞无法触发有效免疫应答。本研究旨在探讨ERAP1与ERAP2基因多态性在KIR及HLA-C基因背景下对反复植入失败（recurrent implantation failure, RIF）的作用。此外，本研究首次报道了ERAP1与ERAP2在RIF患者及已生育女性外周血中的分泌水平。本研究共纳入881名女性受试者：其中496名为伴配偶参与体外受精（in vitro fertilization, IVF）的RIF患者，剩余385名已生育女性作为对照组。数据分析显示，与已生育女性相比，RIF组中携带KIR基因Tel AA区域及HLA-C2C2基因型的女性占比更高（p/pcorr. = 0.004/0.012，比值比OR=2.321）。在本次研究的ERAP基因多态性位点中，rs26653与rs26618这两个位点似乎会在HLA-C2阳性患者中影响RIF的易感性。进一步分析显示，既往已生育的女性其外周血ERAP1分泌水平显著高于IVF患者及妊娠对照组女性（分别对应p<0.0001与p=0.0005）。而ERAP2的分泌结果则恰好相反：已生育女性的外周血ERAP2分泌水平远低于IVF患者（p=0.0098）。体外受精胚胎移植（in vitro fertilization embryo transfer, IVF-ET）后成功妊娠的患者，其外周血ERAP2分泌水平显著低于流产患者（p=0.0032）。受试者工作特征（Receiver operating characteristic, ROC）分析表明，ERAP2浓度约2.9ng/ml可作为区分流产患者与健康分娩产妇的临界阈值。本研究证实，ERAP1与ERAP2均可能参与生殖相关的生理病理过程。