骨髓间充质干细胞对T细胞亚群的影响

本研究探讨人骨髓间充质干细胞对植物血凝素（phytohemagglutinin，PHA）刺激引起的T细胞增殖的影响和可能机制。应用CD3^＋磁珠分选T淋巴细胞，从骨髓分离出的间充质干细胞经照射后与T细胞共培养过夜，经PHA（5μg/ml）作用72小时后，应用BrdU检测T细胞的增殖情况，应用流式细胞术检测T细胞的Annexinv／PI的水平。对未经照射的骨髓间充质干细胞处理的T细胞，用PHA处理72小时后收集T细胞，应用流式细胞术检测CD4，CD8以及CD4和CD25的表达，同时设立未经PHA处理的T细胞与照射的骨髓间充质干细胞共培养组，及未经骨髓间充质干细胞处理的T细胞组。结果表明：骨髓间充质干细胞抑制PHA引起的T细胞的增殖，但不诱导T细胞凋亡。与未处理组相比，骨髓间充质干细胞处理组中T细胞的CD4^＋CD8^＋细胞比例无显著变化；但在PHA作用下，骨髓间充质干细胞处理组中T细胞的CD4^＋亚群显著增加，且呈剂量依赖性，但CD4^＋CD25^＋细胞亚群显著减少。结论：骨髓间充质干细胞抑制PHA刺激所引起的T细胞增殖，对CD8^＋T细胞的抑制作用更强．推测其可能的机制与CD4^＋调节性T细胞的参与有关．但与CD25^＋T调节细胞无明显关系。

Effect of Bone Marrow Mesenchymal Stem Cells on T-Cell Subgroups

The aim of this study was to invesigate the effect of human bone marrow mesenchymal stem cells on human T-cell proliferation resulted from stimulation with PHA and possible immunomodulating mechanism. T cells were positively selected by CD3(+) magnetic beads, and were then co-cultured with irradiated MSCs overnight before the addition of PHA. T-cell proliferation was measured by BrdU assay and the degree of apoptosis was assessed by flow cytometry with Annexin V/PI. T cells co-cultured with or without MSCs were treated with PHA for 72 hours, then harvested. They were labeled with anti-CD4, anti-CD8, anti-CD25 antibodies and analyzed by flow cytometry. The results showed that MSCs inhibited T-cell proliferation, but did not induce T cell apoptosis. There were no significant changes in the ratio of CD4(+) and CD8(+) T cells of MSC-treated group, as compared with the control group. After stimulation with PHA, there was an increase in CD4(+) T cells and decrease of CD4(+)CD25(+) cells in MSC co-cultured group. It is concluded that the MSCs inhibit T-cell proliferation after stimulation with PHA, and show more inhibitive effects on CD8(+) and CD4(+) T cells, but CD25(+) regulatory T cells may not be involved in this process.