CD4^(+)CD45RC^(low)Treg在大鼠肝移植免疫耐受中的调节作用研究

Study of the role of CD4^(+)CD45RC^(low) Treg in regulating immune tolerance of rats undergoing liver transplantation

目的探讨CD4^(+)CD45RC^(low)调节性T细胞(Treg)在肝移植免疫耐受诱导中的作用。方法建立急性排斥反应(AR)[Lewis→Brown Norway(BN),AR组]与自发耐受(BN→Lewis,耐受组)大鼠肝移植模型,每组6只。并设立假手术组(对照组),Lewis大鼠和BN大鼠各3只。对各组大鼠肝组织进行病理学检查;检测各组大鼠外周血、移植肝、脾脏T细胞亚群和浆细胞样树突状细胞(pDC)的表达情况,分析pDC与CD4^(+)CD45RC^(low)Treg的相关性;检测各组大鼠移植肝和脾脏CD4、CD45RC、CD103的表达情况。结果AR组大鼠病理学主要表现为移植肝炎症细胞浸润和组织结构紊乱。与AR组大鼠比较,耐受组大鼠外周血CD4^(+)CD25^(+)Treg、CD8^(+)Treg表达水平均升高(均为P<0.05)。外周血CD4^(+)CD25^(+)Treg与CD8^(+)Treg表达水平呈正相关(r=0.742,P=0.022)。AR组大鼠外周血CD4+CD45RChighT细胞水平高于耐受组和对照组大鼠(均为P<0.05)。与AR组大鼠比较,耐受组大鼠脾脏CD4+CD45RClowTreg表达水平升高,外周血、移植肝、脾脏CD8^(+)CD45RC^(low)Treg表达水平均升高(均为P<0.05)。与对照组和AR组大鼠比较,耐受组大鼠外周血CD8^(+)CD45RC^(low)Treg/CD8+T比值升高,外周血、移植肝、脾脏中pDC的表达水平均升高(均为P<0.05);且CD4^(+)CD45RC^(low)Treg与pDC表达水平的变化呈正相关(r=0.506,P=0.016)。耐受组大鼠移植肝和脾脏CD4、CD45RC、CD103的表达均增多;而AR组大鼠移植肝CD4、CD45RC的表达增多,CD103表达降低。结论CD4+CD45RClowTreg是具有负向免疫调控作用的细胞亚群,与CD8^(+)CD45RC^(low)Treg及pDC等构成免疫耐受诱导的调节性细胞网络。

Objective To investigate the role of CD4^(+)CD45RC^(low) regulatory T cell(Treg)in the immune tolerance induction of rats undergoing liver transplantation.Methods Liver transplantation rat models of acute rejection(AR)[Lewis→Brown Norway(BN),AR group]and spontaneous tolerance(BN→Lewis,tolerance group)were established,with 6 rats in each group.Moreover,3 Lewis rats and 3 BN rats were assigned into the sham operation group(control group).The liver tissues of rats in each group were subject to pathological staining.The expression of T cell subsets and plasmacytoid dendritic cells(pDC)in the peripheral blood,liver graft and spleen of rats was detected in each group.The correlation between pDC and CD4^(+)CD45RC^(low)Treg was analyzed.The expression levels of CD4,CD45RC and CD103 in the liver graft and spleen of rats were quantitatively measured in each group.Results In the AR group,pathological manifestations mainly consisted of inflammatory cell infiltration and structure disorders of transplant liver.Compared with the AR group,the expression levels of CD4^(+)CD25^(+)Treg and CD8+Treg in the peripheral blood were significantly upregulated in the tolerance group(all P<0.05).In the peripheral blood,the expression level of CD4^(+)CD25^(+)Treg was positively correlated with that of CD8+Treg(r=0.742,P=0.022).In the AR group,the expression level of CD4^(+)CD45RChighT cell in the peripheral blood was significantly higher than those in the tolerance and control groups(both P<0.05).Compared with the AR group,the expression level of CD4^(+)CD45RC^(low) Treg in the spleen,and the expression levels of CD8^(+)CD45RC^(low)Treg in the peripheral blood,transplant liver and spleen were significantly up-regulated in the tolerance group(all P<0.05).Compared with the control and AR groups,the ratio of CD8^(+)CD45RC^(low)Treg/CD8^(+)T in the peripheral blood and the expression levels of pDC in the peripheral blood,transplant liver and spleen were all significantly up-regulated in the tolerance group(all P<0.05).The expression level of CD4^(+)CD45RC^(low)Treg was positively correlated with the changes of pDC(r=0.506,P=0.016).The expression levels of CD4,CD45RC and CD103 in the transplant liver and spleen of rats were up-regulated in the tolerance group.In the AR group,the expression levels of CD4 and CD45RC were up-regulated,whereas that of CD103 was down-regulated.Conclusions CD4^(+)CD45RC^(low)Treg is a cell subgroup with negative immune regulation,which may construct a regulatory cell network of immune tolerance induction along with CD8+CD45RClowTreg and pDC.