CD4＋T细胞抗体标记超顺磁性氧化铁MR成像诊断异种胰岛移植免疫排斥反应的实验研究

Detection of the immunologic rejection after xeno-islet transplantation： a study by MR imaging enhanced with superparamagnetic iron oxide marking CD4＋ T cell antibody

目的探讨利用抗人分化抗原簇（CD）4＋T细胞抗体标记的纳米免疫超顺磁性氧化铁（SPIO）作为MRI生物探针，诊断胰岛细胞移植后免疫排斥反应的可行性。方法27只BALB／C裸鼠，每只左肾被膜下移植分离纯化后的猪胰岛细胞2000个，3周后MRI可观察到肾包膜下移植物大小，然后采用数字表法随机将实验动物分为实验组（21只）和对照组（6只）。将人T淋巴细胞注入实验组鼠腹腔内重建人的T淋巴细胞免疫系统，其中20只重建成功。实验组动物免疫系统重建前及重建后3、7和14d，经尾静脉注射纳米免疫SPIO，30min后行MRI T2WI，观察移植物的MRI信号改变。MRI结束后立即安乐死方法牺牲动物，取下左肾行移植物病理组织检查；对照组动物胰岛细胞移植后，不进行免疫处理，与实验组动物相同时间点给予相同检查。并以病理检查为金标准，用临床诊断一致性检验计算MRI对异种胰岛细胞移植后免疫排斥反应诊断的灵敏度、特异性、Youden指数和符合率。结果2组动物在移植胰岛细胞3周后MRI可显示移植物。实验组BALB／C裸鼠，重建免疫系统前及重建成功后3d注入纳米免疫SPIO，MRI移植物局部未见异常信号；免疫系统重建成功后7d，MRI显示移植物对应区域信号减低，苏木精-伊红及CD4＋T免疫组织化学染色显示移植物局部大量淋巴细胞浸润，提示免疫排斥反应发生。对照组动物移植物所有MRI均未见异常；病理组织学检查移植物局部未见炎性细胞浸润。MRI对免疫反应检测的灵敏度、特异度、Youden指数和符合率分别为：（72．96±0.24）％、100％、0．73±0．24、（88．46±0．13）％（Kappa值为0．76）。结论通过抗人CD4＋T细胞抗体标记的纳米免疫SPIO生物探针MRI，可以检查异种胰岛细胞移植后免疫排斥反应，并能早期、实时、无创性的对移植受体免疫排斥反应进行诊断。

Objective To evaluate the feasibility of the diagnosis of the early immunologic rejection after xeno-islet transplantation by MR imaging enhanced with superparamagnetic iron oxide （SPIO） marking CD4＋T cell antibody. Methods Two thousand neonatal porcine islets （NPI）were transplanted under the left renal capsule of BALB/C nude mice. When the grafts could be observed by MRI, 107 human PBMC was intraperitoneal injected to nude mouse models to reconstitute the human immunologic system,20 mice were reconstituted. Before and 3,7, ld days after reconstitution of human immunologic system on BALB/C nude mice, MRI imaging was performed half an hour after intravenous injection of nano-immunomagnetic beads via vena caudalis to observe the grafts＇ MRI signal. BALB/C nude mice were sacrificed after MRI scanning immediately, the histopathologic examination was assessed on grafts, the results were compared with MRI results. And calculate the sensitivity, specificity, Youden index number and coincidence of the MRI for immunologic rejection. Results Grafts can be observed by MRI 3 weeks after islet cell transplantation （before immunologic rejection modeling）, there is no abnormal MRI signal detected in nude mice＇ graft region after microbeads injected. Seven days after building of immunologic rejection model, MRI hypo-signal in graft site is shown in the T2WI sequence after nano-bioprober injected. Histopathologic assessments were employed on grafts in nude mice immediately （ HE and immunohistochemistry staining）, the results shown that there are a lot of T lymphocyts infiltrated in graft region, implying the occurrence of immunologic rejection. And the sensitivity, specificity, Youden index number and coincidence is ： （72.96± 0. 24） %, 100%, 0.73±0.24, （ 88.46 ± 0. 13 ） % respectively. The correct Kappa between the MRI and the imunohistochemistry staining was 0. 76. Conclusion The cellular immunological rejection to xeno-islet grarts can be assessed with nano-bioprobe with anti-CD4＋ antibody MR imaging, real time, and noninvasively.