目的 在小鼠血吸虫病肝纤维化模型中，探究自然杀伤（NK）细胞条件性敲除抑制性受体T细胞免疫球蛋白和免疫受体酪氨酸抑制性基序结构域（tigit）对疾病进程的影响及其潜在作用机制。方法 取4只NK细胞条件性敲除tigit小鼠作为实验组，4只同窝野生型小鼠作为对照组，小鼠经皮肤感染日本血吸虫尾蚴[（20 ± 2）条/只]，感染后第6周收集小鼠肝组织，苏木精-伊红（HE）和马松（Masson）染色观察虫卵肉芽肿形态结构、炎细胞浸润程度和胶原纤维沉积情况，兔抗鼠α-平滑肌肌动蛋白（α-SMA）免疫组化染色观察肝组织纤维化程度，采用ImageJ软件计算阳性染色面积百分比；逆转录实时荧光定量PCR（RT-qPCR）检测α平滑肌肌动蛋白（acta2）、Ⅰ型胶原蛋白（I-c）及tigit的mRNA相对转录水平。对两组小鼠肝组织RNA进行转录组测序，筛选差异表达基因，并进行基因本体（GO）功能富集分类。采用GraphPad Prism 9软件进行统计学分析，数据采用独立样本t检验。结果 HE染色显示，相较于对照组，实验组小鼠虫卵肉芽肿面积较小，炎症细胞浸润程度较轻。Masson染色显示，实验组小鼠肝组织胶原沉积减少，沉积范围局限，多呈纤细的纤维条索状，对照组小鼠肝组织内可见大量蓝色胶原纤维沉积，并且在虫卵肉芽肿周围形成明显的纤维包裹。实验组胶原沉积评分（8.07 ± 0.52）较对照组（26.07 ± 1.54）降低（t = 19.22, P < 0.01）。α-SMA免疫组化染色显示，实验组小鼠肝组织内α-SMA阳性表达明显减少，染色强度减弱，对照组α-SMA阳性表达广泛，主要见于肉芽肿周围活化的肝星状细胞及窦周隙。半定量分析证实，实验组α-SMA阳性面积百分比（3.39 ± 1.25）较对照组（8.60 ± 2.47）下降（t = 5.92, P < 0.01）。RT-qPCR结果显示，实验组小鼠肝组织纤维化指标acta2、I-c、tigit基因mRNA相对转录水平分别为0.87 ± 0.06、0.88 ± 0.03、1.03 ± 0.11，低于对照组的1.40 ± 0.03、1.2 ± 0.02、1.67 ± 0.15（t = 14.93、14.99、6.216，均P < 0.01）。转录组测序共鉴定出431个差异表达基因（上调基因365个，下调基因66个）。GO富集分析显示，上调基因显著富集于免疫应答相关通路，涵盖NK细胞脱颗粒、肝星状细胞激活负向调控、中性粒细胞趋化与迁移等通路。结论 NK细胞条件性敲除tigit可能通过恢复NK细胞功能及抑制肝星状细胞活化减轻小鼠血吸虫病肝纤维化，并影响中性粒细胞通路，提示其在肝脏免疫微环境中具有复杂调控作用。

Objective To investigate the effect of conditional knockout of inhibitory receptor T-cell immunoreceptor immunoglobulin and tyrosine-based inhibitory motif domain (tigit) in natural killer (NK) cells on disease progression in a model of schistosomiasis liver fibrosis and unravel the underlying mechanisms. Methods Four mice with tigit conditional knockout NK cells were used as the experimental group, and four wild-type mice in the same litter served as controls. All mice were percutaneously infected with Schistosoma japonicum cercariae (20 ± 2 per mouse), and mouse liver tissues were sampled 6 weeks post infection. The morphological structure of egg granulomas, degree of inflammatory cell infiltration, and collagen fiber deposition were observed using hematoxylin and eosin (HE) staining and Masson’s trichrome staining, and the degree of liver fibrosis was assessed using immunohistochemical staining of α smooth muscle actin (α-SMA). The percentage of positively stained area was calculated using the software ImageJ. The relative mRNA expression of alpha smooth actin (acta2), Ⅰ-collagen (I-c) and tigit was quantified with a reverse transcription quantitative Real-time PCR (RT-qPCR) assay. Total RNA extracted from mouse liver tissues was subjected to transcriptome sequencing to identify differentially expressed genes, followed by Gene Ontology (GO) functional enrichment analysis. All statistical analyses were performed using the software GraphPad Prism 9, and differences of means were tested for statistical significance with independent samples t test. Results HE staining revealed smaller areas of egg granulomas and milder inflammatory cell infiltration in the experimental group relative to the control group. Masson’s trichrome staining showed reduced collagen deposition that was confined to localized areas and presented as slender fibrous strands in mouse liver tissues in the experimental group, and deposition of extensive blue collagen fibers in mouse liver tissues in the control group, producing obvious fibrous encapsulation around egg granulomas. The score for collagen deposition was significantly lower in the experimental group (8.07 ± 0.52 points) than in the control group (26.07 ± 1.54 points) (t = 19.22, P < 0.01). Immunohistochemical staining for α-SMA revealed a marked decrease in positive α-SMA expression and staining intensity in mouse liver tissues in the experimental group, whereas widespread positive α-SMA expression was detected in mouse liver tissues in the control group, which was mainly found around activated hepatic stellate cells around granulomas and in the perisinusoidal spaces. Semi-quantitative analysis revealed a lower percentage of α-SMA positive areas in the experimental group (3.39 ± 1.25) than in the control group (8.60 ± 2.47) (t = 5.92, P < 0.01). RT-qPCR assay quantified lower relative mRNA expression of the fibrosis-related genes acta2 [(0.87 ± 0.06) vs. (1.40 ± 0.03); t = 14.93, P < 0.01], I-c [(0.88 ± 0.03) vs. (1.2 ± 0.02); t = 14.99, P < 0.01], and tigit [(1.67 ± 0.15) vs. (1.03 ± 0.11); t = 6.216, P < 0.01] in the experimental group than in the control group. Transcriptome sequencing identified 431 differentially expressed genes (365 up-regulated and 66 down-regulated genes), and GO enrichment analysis indicated that the up-regulated genes were significantly enriched in immune response-related pathways, including pathways of NK cell degranulation, negative regulation of hepatic stellate cell activation, and neutrophil chemotaxis and migration. Conclusion Conditional knockout of tigit in NK cells may alleviate schistosomiasis liver fibrosis in mice by restoring NK cell functions and inhibiting hepatic stellate cell activation, and affect the neutrophil pathway, suggesting that TIGIT has a complex regulatory role in the liver immune microenvironment.