目的 探索刚地弓形虫感染对早孕期母胎界面蜕膜免疫细胞内吲哚胺2,3-双加氧酶（IDO）表达水平的影响，并分析其与不良妊娠结局的关系。方法 40只C57BL/6野生型孕鼠分为野生型对照组（20只）和感染组（20只），IDO基因敲除（IDO^-/-）孕鼠（20只）为IDO^-/-感染组。孕8 d时，2个感染组小鼠分别腹腔注射250个弓形虫RH速殖子（悬于250 µl PBS），野生型对照组小鼠腹腔注射等量PBS。孕14 d时，观察各组孕鼠的精神状态，取孕鼠胎盘、胎鼠并称重，计算异常胎鼠率。取自愿终止妊娠的健康人早孕期蜕膜组织，采用人淋巴细胞分离液制备人蜕膜单个核细胞悬液。取细胞悬液，分为对照组和弓形虫感染组（每组1.5 × 10⁷个细胞），对照组不处理，感染组按弓形虫速殖子与细胞1:3的比例感染，培养20 h后收集两组细胞。采用流式细胞术检测蜕膜自然杀伤（dNK）细胞、蜕膜巨噬细胞（dMϕ）、蜕膜树突状细胞（dDC）和蜕膜髓源性抑制细胞（dMDSC）内IDO的表达水平。利用CD3^-CD56⁺、CD14、DC、CD33磁珠分选试剂盒分别分离纯化dNK细胞、dMϕ、dDC和dMDSC，各类细胞均设对照组和弓形虫感染组（每组1 × 10⁷个细胞），对照组不处理，感染组按弓形虫速殖子与细胞1:3的比例感染，培养20 h后收集两组细胞并提取蛋白。采用蛋白质免疫印迹（Western blotting）检测各类蜕膜免疫细胞内IDO的表达水平。采用GraphPad Prism 10.1.2软件进行统计学分析，组间数据分析采用独立样本Student’s t检验。结果 IDO^-/-感染组孕鼠较野生型感染组孕鼠不良妊娠结局明显加重，精神更萎靡，行动更迟缓，胎盘淤血更严重、干瘪塌陷无弹性，且胎鼠发育不良，伴有吸收胎出现。野生型感染组孕鼠的胎盘、胎鼠质量分别为（55.73 ± 5.52）、（106.88 ± 37.33）mg，均低于野生对照组的（81.73 ± 9.35）、（198.66 ± 26.58）mg（t = 6.329、5.299，均P < 0.01）；IDO^-/-感染组孕鼠的胎盘胎鼠质量分别为（39.87 ± 4.24）、（51.67 ± 19.75）mg，均较野生型感染组孕鼠减轻（t = 5.726、3.241，P < 0.01）。野生型对照组未出现异常胎鼠；野生型感染组异常胎鼠率为（40.60 ± 20.69）%，高于野生型对照组（t = 5.193，P < 0.01）；IDO^-/-感染组异常胎鼠率为（93.33 ± 10.80）%，高于野生型感染组（t = 5.600，P < 0.01）。流式细胞术检测人蜕膜单个核细胞结果显示，感染组dNK细胞内IDO的阳性细胞率为（8.02 ± 3.20）%，与对照组的（9.65 ± 2.62）%差异无统计学意义（t = 2.025，P > 0.05）；感染组dMϕ、dDC、dMDSC内IDO的阳性细胞率分别为（27.50 ± 6.24）%、（20.23 ± 3.20）%、（3.14 ± 0.57）%，均低于对应细胞对照组的（35.07 ± 8.11）%、（24.80 ± 4.13）%、（6.81 ± 0.88）%（t = 5.830、5.533、5.644，均P < 0.05）。感染后，IDO的阳性细胞率在dMDSC内下降幅度最大，下降了（53.20 ± 11.56）%；在dMϕ内次之，下降了（21.45 ± 3.65）%；在dDC和dNK细胞内分别下降了（18.22 ± 4.17）%、（17.84 ± 15.54）%。Western blotting结果显示，感染组dNK细胞、dMϕ、dDC、dMDSC中IDO的相对表达水平分别为0.91 ± 0.10、0.62 ± 0.12、0.75 ± 0.11、0.47 ± 0.06，均低于对应细胞对照组的1.04 ± 0.11、1.14 ± 0.09、1.11 ± 0.06、1.05 ± 0.03（t = 13.360、12.930、7.482、13.960，P < 0.05或 < 0.01）。感染后，IDO的相对表达水平在dMDSC内下降幅度最大，下降了（55.22 ± 16.12）%；在dMϕ内次之，下降了（46.30 ± 6.98）%；在dDC和dNK细胞内分别下降了（33.53 ± 7.78）%、（12.74 ± 0.67）%。结论 早孕期弓形虫感染可下调母胎界面中dNK细胞、dMϕ、dDC和dMDSC内IDO的表达水平，进而加重不良妊娠结局的发生，提示IDO表达下调与不良妊娠结局的发生密切相关。

Objective To investigate the effect of Toxoplasma gondii infection on indoleamine 2,3-dioxygenase (IDO) expression in decidual immune cells at the maternal-fetal interface during pregnancy, and to examine its association with adverse pregnancy outcomes. Methods A total of 40 wild-type pregnant mice of the C57BL/6 strain were divided into the wild-type control group and the infection group, of 20 animals in each group, while 20 pregnant IDO gene-knockout mice were assigned as the IDO^-/- infection group. Mice in two infection groups were intraperitoneally injected with 250 T. gondii RH tachyzoites in 250 µl PBS on day 8 of gestation, and animals in the wild-type control group were intraperitoneally injected with an equal volume of PBS. The mental state of the pregnant mice was observed on day 14 of gestation, and placental weight of pregnant mice and fetal weight were recorded and the incidence of abnormal fetal mice was calculated. Clinical decidual tissues were obtained from healthy pregnant women who voluntarily chose to terminate their pregnancies during the first trimester, and mononuclear cell suspensions of human decidual tissues were prepared using the human lymphocyte separation solution. Cell suspensions were divided into the control group and T. gondii infection group, with 1.5 × 10⁷ cells in each group. No treatment was given in the control group, and cells in the T. gondii infection group were infected with T. gondii RH strain tachyzoites at a tachyzoite-to-cell ratio of 1 : 3. Cells were harvested in both groups 30 hours following incubation. The IDO expression was detected in decidual natural killer (dNK) cells, decidual macrophages (dMϕ), decidual dendritic cells (dDC), and decidual myeloid-derived suppressor cells (dMDSC) using flow cytometry. dNK cells, dMϕ, dDC, and dMDSC were separated and purified from human decidual mononuclear cells with CD3^-CD56⁺, CD14, DC, and CD33 magnetic microbeads separation kits, respectively. These types of cells were all divided into the control group and the T. gondii infection group, with 1 × 10⁷ cells in each group. Cells in the control group were given no treatment, while cells in the infection group were infected with T. gondii RH strain tachyzoites at a tachyzoite-to-cell ratio of 1 : 3. Cells in both groups were harvested 20 hours following culture. Total proteins were extracted from cells, and the IDO expression was determined in various types of decidual immune cells using Western blotting. All statistical analyses were performed using the software GraphPad Prism 10.1.2, and comparisons of means between groups were conducted with independent sample Student’s t-test. Results The pregnant mice exhibited poorer pregnancy outcomes, more listlessness, slower movements, more severe placental congestion, and placental dryness, collapse, and elasticity loss in the IIDO^-/- infection group relative to in the wild-type control group, and the pregnant mice in the IDO^-/- infection group had poorly developed fetuses and absorbed fetuses. The pregnant mice had lower placental [(55.73 ± 5.52) mg vs. (81.73 ± 9.35) mg; t = 6.329, P < 0.01] and fetal weights [(106.88 ± 37.33) mg vs. (198.66 ± 26.58) mg; t = 5.299, P < 0.01) in the wild-type infection group than in the wild-type control group, and the pregnant mice had lower placental [(39.87 ± 4.24) mg] and fetal weights [(51.67 ± 19.75) mg] in the IDO^-/- infection group than in the wild-type infection group (t = 5.726 and 3.241, both P values < 0.01). No abnormal fetal mice were seen in the wild-type infection group, while a higher incidence rate of abnormal fetuses was found in the wild-type infection group [(40.6 ± 20.69)%] than in the wild-type control group (t = 5.193, P < 0.01) and higher in the IDO^-/- infection group [(93.33 ± 10.80)%] than in the wild-type infection group (t = 5.600, P < 0.01). Flow cytometry detected no significant difference in the proportion of positive IDO expression in dNK cells between the infection and control groups [(8.02 ± 3.20)% vs. (9.65 ± 2.62)%; t = 2.025, P > 0.05], and higher proportions of positive IDO expression in dMϕ [(27.50 ± 6.24)% vs. (35.07 ± 8.11)%; t = 5.830, P < 0.05], dDC [(20.23 ± 3.20)% vs. (24.80 ± 4.13)%; t = 5.533, P < 0.05] and dMDSC [(3.14 ± 0.57)% vs. (6.81 ± 0.88)%; t = 5.644, P < 0.05] in the infection group than in the control group. The largest reduction in the proportion of positive IDO expression [(53.20 ± 11.56)%] was seen in dMDSC following T. gondii infection, followed by in dMϕ [(21.45 ± 3.65)%], dDC [(18.22 ± 4.17)%] and dNK cells [(17.84 ± 15.54)%]. Western blotting determined relatively lower IDO expression in dNK cells [(0.91 ± 0.10) vs. (1.04 ± 0.11); t = 13.360, P < 0.01], dMϕ [(0.62 ± 0.12) vs. (1.14 ± 0.09); t = 12.930, P < 0.01)], dDC [(0.75 ± 0.11) vs. (1.11 ± 0.06); t = 7.482, P < 0.05] and dMDSC [(0.47 ± 0.06) vs. (1.05 ± 0.03); t = 13.960, P < 0.01] in the infection group than in the control group. The largest reduction in the relative IDO expression [(55.22 ± 16.12)%] was seen in dMDSC following T. gondii infection, followed by in dMϕ [(46.30 ± 6.98)%], dDC [(33.53 ± 7.78)%] and dNK cells [(12.74 ± 0.67)%]. Conclusion T. gondii infection may downregulate the IDO expression in dNK cells, dMϕ, dDC and dMDSC at the maternal-fetal interface during the first trimester of pregnancy, thereby increasing the incidence of adverse pregnancy outcomes. These findings suggest that downregulation of IDO expression is closely associated with the occurrence of adverse pregnancy outcomes.