PD-1/PD-L1及相关炎症因子在细粒棘球蚴感染致肝损伤中的免疫调节作用北大核心CSCD

目的探讨程序性死亡受体-1(programmed cell death receptor 1,PD-1)、程序性死亡受体配体1(programmed cell death-Ligand-1,PD-L1)及相关炎症因子在棘球蚴感染免疫损伤中的免疫调控机制。方法将BALB/c小鼠分为2个组:对照组(40只)、模型组(40只)。采用原头蚴腹腔注射制备细粒棘球蚴感染模型,腹腔接种后2 d、8 d、1个月、3个月、6个月时每组取8只小鼠行内眦静脉取血,采用流式细胞术微球阵列法试剂盒(Cytometric Bead Array,CBA)检测小鼠外周血中白细胞介素6(interleukin-6,IL-6)、白细胞介素17A(interleukin-17A,IL-17A)和肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)的含量。取肝脏进行苏木精-伊红(hematoxylin-eosin staining,HE)染色,采用免疫组织化学染色法检测小鼠肝组织中PD-1、PD-L1的表达。结果对照组腹部未见异常。模型组小鼠腹部出现明显膨隆,腹腔中有包囊。对照组小鼠肝组织结构正常,模型组小鼠6个月时肝脏有大片肝细胞坏死变性,可见大量炎性细胞浸润。对照组小鼠肝组织PD-1、PD-L1表达均呈阴性,模型组小鼠3个月时肝脏开始出现明显PD-1表达的阳性细胞,主要位于肝损伤区域,6个月时小鼠PD-1的表达主要集中于肝坏死区域周围,可见明显增多的阳性细胞存在。模型组2 d和8 d时均可见PD-L1表达的大量阳性细胞,1个月肝脏PD-L1呈低表达,3个月开始表达又升高。模型组小鼠TNF-α在感染2 d时高于对照组(t=15.587,P<0.05),后开始下降,从3个月开始时TNF-α升高,至6个月时达高峰,模型组小鼠血清中IL-17A在感染8 d时高于对照组(t=0.067,P<0.05),后一直呈上升趋势,至6个月时达高峰,IL-6在感染2 d开始即高于对照组,6个月时达高峰。结论IL-6、TNF-α、IL-17A参与了细粒棘球蚴感染导致的炎症反应。细粒棘球感染模型小鼠肝脏出现高表达的PD-1/PD-L1,随着时间延长,PD-1表达逐渐增强,尤其是细粒棘球蚴感染早期,PD-L1高表达,PD-1、PD-L1在感染前期、中期就开始发挥负调节作用,可进一步促进棘球蚴组织在体内迅速生长,参与肝脏的损伤作用。在细粒棘球蚴感染早、中期,阻断PD-1/PD-L1信号通路,将有助于抗棘球蚴感染。

Roles of PD-1/PD-L1 and related inflammatory factors in liver injury caused by Echinococcus granulosus infection

This study explored the immune regulation mechanism of programmed cell death receptor-1 (PD-1) and its ligand (PD-L1) with related inflammatory factors in hydatid infection. BALB/c mice were divided into a control group (n=40) and model group (n=40). Intraperitoneal injection of protocephalic larvae was used to prepare a model of Echinococcus granulosus infection. At 2 d, 8 d, 1 month, 3 months and 6 months after injection, eight mice from each group were used to detect the levels of peripheral interleukin 6 (IL-6), interleukin 17A (IL-17A) and tumor necrosis factor-α (TNF-α). The livers were collected for HE staining, and the expression of PD-1 and PD-L1 in the liver tissues of the mice was detected by immunohistochemical staining. In the control group, no abnormalities were observed. Mice in the model group had obvious swelling in the abdomen, with cysts in the abdominal cavity. The liver tissue structure of the mice in the control group was normal, whereas that of mice in the model group mice showed large areas of hepatocyte necrosis and degeneration, with large numbers of inflammatory cells. The expression of PD-1 and PD-L1 in the liver tissues inn the control group was negative. A large number of positive cells expressing PD-L1 were seen in the model group on days 2 and 8. PD-L1 expression in the liver was low at 1 month and began to increase at 3 months. TNF-α in the model group increased at 3 months, reaching a peak at 6 months. The IL-17A in the serum of mice in the model group was higher than that in the control group at 8 days after infection (t=0.067,P<0.05), then subsequently increased, peaking at 6 months. IL-6 in the serum of mice in the model group was higher than that in the control group at 2 days after infection and reached a peak at 6 months. IL-6, TNF-α and IL-17A are involved in the inflammatory response to cystic hydatid infection. The expression of PD-1 gradually increased, especially in early stages of Echinococcus granulosus infection. PD-L1 was highly expressed, and PD-1 and PD-L1 began to play a negative regulatory role in the early and middle stages of infection, thus further promoting the rapid growth of hydatid tissue in the body and participating in liver damage. Blocking the PD-1/PD-L1 signaling pathway in the early and mid-stages of infection may help combat hydatid infection.