移植抗原特异性转基因CD8+T细胞对白细胞介素2的依赖性

目的研究白细胞介素2（IL-2）在调节移植抗原特异性转基因CD8^＋T细胞介导的免疫排斥反应中的作用。方法将经荧光染科CFSE标记后的C57BL／6小鼠和2CTg小鼠（CD4敲除鼠）淋巴细胞分别植入经致死剂量γ射线照射过的两组DBA／2J小鼠体内，检测CD4^＋与CD8^＋T细胞在体内分裂增殖的时相，并用胞浆内IL-2标志染色方法测定活化后T细胞表达IL-2的能力。以Balb／c小鼠为供者，糖尿病2CTg小鼠和2C Tg-IL-2KO小鼠（IL-2敲除鼠）为受者，进行胰岛细胞移植。观察CD8^＋ T细胞在介导移植排斥中的作用。结果DBA／2J小鼠输注了C57BL／6小鼠的淋巴细胞后，CD4^＋与CD8^＋T细胞分裂增殖均非常明显，前者表达大量IL-2，后者则不表达。DBA／2J小鼠输注了2CTg小鼠的淋巴细胞后。在完全没有CD4^＋T细胞存在的情况下，CD8^＋T细胞仍明显分裂增殖并大量表达IL-2。2CTg和2CTg—IL-2KO小鼠移植胰岛细胞后，前者迅速发生排斥反应，胰岛移植物的平均存活时间仅为8d，而后者胰岛移植物的平均存活时间〉50d。结论CD8^＋T细胞在产生和利用IL-2时有很大的可塑性。CD4^＋T细胞存在时，CD8^＋T细胞能有效利用CD4^＋T细来源的IL-2进行分裂增殖，在缺乏CD4^＋T细胞时，则利用自身来源的IL-2进行分裂增殖；移植抗原特异性CD8^＋T细胞的效应功能完全依赖于IL-2，排斥反应由CD8^＋T细胞介导时，阻断IL-2／IL-2受体通路可诱导移植物长期存活。

Alloantigen specific TCR transgenic CD8 + T cells require IL-2 to mediate allograft rejection

Objective To study the role of IL-2 in regulating allograft rejection mediated by alloantigen-specific CD8~+ T cell.Methods T cell proliferation in vivo at a single cell level was examined using the CFSE dilution assay. IL-2 expression by activated CD4~+ versus CD8~+ T cells was determined by intracellular cytokine staining. The ability of alloantigen-specific CD8~+T cells in mediating allograft rejection was studied using the islet transplantation model.Results CD8~+ T cells divided vigorously in vivo in the allogeneic hosts regardless the presence or absence of CD4~+ T cells. CD4~+ T cells, but not CD8~+ T cells, were the primary source of IL-2 when both subsets were present. However, CD8~+ T cells could express high levels of IL-2 in the complete absence of CD4~+ T cells. In 2C TCR transgenic (Tg) mice in which the 2C TCR transgene was selectively expressed on the CD8~+ T cells that specifically recognized alloantigen (Ld) of Balb/c origin, islet allografts from Balb/c mice was promptly rejected by the 2CTg recipients with mean survival time of only 8 days. In contrast, in 2CTg mice with a genetic deletion of the IL-2 gene (2CTg-IL-2KO mice), the alloantigen specific CD8~+ T cells failed to mediate the islet allograft rejection and all the Balb/c islets survived for more than 50 days.Conclusions CD8~+ T cells appear to be very plastic in producing and utilizing IL-2. In the presence or absence of CD4~+ T cells, CD8~+ T cells can use CD4~+ derived or self derived IL-2 for proliferation and effector function respectively. In an alloantigen specific TCR transgenic model, the effector function of CD8~+ T cells is strictly IL-2 dependent. Thus, in situations where graft rejection is mediated solely by the CD8~+T cells, blocking IL-2/IL-2R pathway may be critically important in preventing transplant rejection.