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Objective To investigate the effects of blockade of OX40/OX40L costimulation pathway on mice islet allograft tolerance in CD40/CD154 costimulation pathway blockade mice.Methods C57BL/6 mice were induced into diabetes mellitus as recipients,and were transplanted with DBA/2 mice islets.The recipients were divided into four groups,(1) treated with IgG as controls,(2) anti-OX40L mAb,(3) anti-CD154,(4) combined treatment of anti-OX40L mAb and anti CD154mAb.The mean survival time (MST) of islet allograft was observed.The expression of OX40 in activated T cells of CD154 deficient mice was detected.Effector T cells were obtained from the spleen of CD154 deficient mice cultured with or without anti-OX40L mAb for 3 days.The proliferation of T cells was assayed.Results The MST in the control group,anti-OX40L mAb group,anti-CD154 mAb group and anti OX40L mAb + anti-CD154 mAb group was 19,22,48,and ＞150 days respectively (P ＜0.05).The OX40 expression was readily induced in the 66％ activated T effector cells.CD154 deficient T effector cells proliferation was inhibited by the addition of anti-OX40L mAb in the culture in a dose-dependent fashion.Conclusion The blockade of OX40/OX40L costimulation pathway can promote islet allograft tolerance in CD40/CD154 costimulation pathway blockade mice by inhibiting the proliferation of T cells.
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Objective To investigate the role of OX40 in the mechanisms of memory T cells in islet transplant tolerance.Methods The expression of OX40 on native, like memory and memory CD8+T cells was detected by RT-PCR. Splenic T cells from B6 mice were injected into Rag-/- mice via the tail vein, and the Rag-/- mice were divided into three groups (n=8 each): control group, given IgG; treatment group, given anti-OX40L; and OX40 knock-out group, given T cells from OX40 knock-out B6 mice spleen. All recipients were induced into diabetes mellitus model after adoptive transfer. Islet transplantation was performed on all Rag-/- mice as recipients. The mean survival time of islet was observed.Results The expression of OX40 in native T cells, like memory T cells and memory T cells was 2.87, 111.24 and 146.15 respectively. The expression of OX40 in like memory and memory T cells was higher than in native T cells (P<0.05). Comparison with control group , The mean survival time of the DBA/2 islet allografts in treatment group (130 days) and OX40 knock-out group (125 days) was significantly longer than in control group (21 days, P<0.05).Conclusion The OX40 expression is high in memory T cells. The mean survival time of the islet allografts can be prolonged by blocking OX40/OX40L pathway. OX40/OX40L pathway may be the key point of transplant tolerance.
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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.