CD4^+ CD25^+调节性T细胞对致敏小鼠异基因造血干细胞移植影响

Effects of CD4^+ CD25^+ Regulatory T Cells on Allogeneic Hematopoietic Stem Cell Transplantation in Sensitized Mice

本研究旨在探讨CD4+CD25+调节性T细胞(Treg)对异基因造血干细胞(HSC)在致敏小鼠植入的影响,为临床应用异基因造血干细胞移植(HSCT)治疗致敏受者免疫排斥提供实验依据。BALB/c小鼠分为5组:致敏组、致敏及移植前7 d应用5×105Treg组、致敏及移植前13及7 d应用5×105Treg组、未致敏小鼠移植组(给予等体积的PBS对照)和正常小鼠空白对照组。每组动物15只。移植当天给予致死量8 Gy照射,然后将荧光标记的C57BL/6小鼠骨髓干细胞(BMSC)经尾静脉注入BALB/6小鼠内。在不同时间点取血或器官组织用流式细胞仪检测荧光细胞归巢情况,同时记录生存状况,监测造血重建水平。结果表明,移植后12及24 h,应用Treg组与致敏组相比,不同组织中荧光细胞归巢数量明显增多(P<0.05);致敏组和空白对照组小鼠均于照射后6-13 d死亡,而分别应用5×105Treg 1次及2次组小鼠中位生存期分别为15和16 d,与致敏组相比,差异均具有统计学意义(P<0.001);两Treg细胞组之间相比较差异无统计学意义(P>0.05)。结论:应用Treg能诱导致敏受鼠对异基因HSC一定程度的免疫耐受,抑制免疫杀伤,延长其生存期,但未能完全诱导免疫耐受,最后致敏小鼠仍因HSC排斥而死亡。

The aim of this study was to investigate the effects of CD4 ＋ CD25＋ regulatory T cells （Treg） on allogeneic hematopoietic stem cell transplantation （HSCT） in sensitized mice so as to provide experimental evidence for clinical treatment of allogeneic HSCT rejection in sensitized recipients. The BALB/c mice were divided into 5 groups ： group A -- mice were sensitized with injection of splenocytes; group B -- mice were sensitized with splenocytes and treated with 〉 5 ×10^5 Treg on day 7 before transplantation; group C -- mice were sensitized with splenocytes and treated with 5 × 10^5 Treg on day 13 and 7 before transplantation; group D -- mice were not sensitized, but treated with equal volume of PBS as control; group E -- blank control. Each group had 15 mice. On day 0 of transplantation, mice in each group were irradiated lethally with 8 Gy by linear accelerator, and the bone marrow cells of C57BL/6 labeled by fluorescence staining were intravenously injected via the tail vein. The fluorescent cells in peripheral blood and organ tissue were detected by flow cytometry on different time points for homing assessment. Survival rates and hematopoietic reconstitution were also recorded and monitored. The results showed that on 12 and 24 hours after transplantation, as compared with the sensitized group, the number of fluorescence homing cells in different tissue of the applied Treg groups increased significantly and the differences were statistically significant （ P 〈 0. 05 ）. The mice in sensitized group and blank control group all died on the 6 - 13 day, whereas the median survival time of mice in applied Treg once and twice were 15 days and 16 days respectively. Comparing with sensitized group, the difference was statistically significant （ P 〈 0. 001 ）, but there was no significant difference between these two groups applied regulatory T cell （ P 〉 0. 05 ）. It is concluded that applying Treg can induce immune tolerance of sensitized recipient to allogeneic HSCT and inhibit immune destruction and prolong the survival time, but can not induce full immune tolerance and at last sensitized mice died of rejection of hematopoietic stem cells.