内源性树突状细胞介导免疫抑制性外源性树突状细胞在心脏移植免疫调节中的作用

发布时间：2018-03-26 15:24

本文选题：心脏移植　切入点：排斥反应　出处：《哈尔滨医科大学》2011年博士论文

【摘要】：心脏移植是治疗终末期心脏病的有效手段。近年来，，尽管移植术后的近期生存率得到了显著的提高，但是受者远期生存情况并未得到有效改善。目前，由于免疫抑制药物的明显缺陷，心脏移植后受者的主要病死原因均与免疫抑制过度（感染，恶性肿瘤）或不足（排斥，心脏移植物血管病，晚期移植物衰竭）相关。因此，免疫排斥是影响移植远期效果的最主要障碍,是心脏移植领域当前的核心问题。移植免疫领域研究更多的集中在供者特异性免疫调节方面，如树突状细胞（dendritic cell，DC）治疗。近年来，大量的研究揭示了DC诱导和维持自我耐受的机制，并在体外培养耐受诱导DC，用于供者特异性免疫耐受的诱导。耐受诱导或免疫抑制性DC为未成熟、成熟抵抗或者通过其他方式激活的DC。这些DC表达MHC分子，低水平表达共刺激分子，甚至传递抑制信号，不能正常合成促进Th1细胞反应的细胞因子。目前的观点普遍认为，治疗性免疫抑制性DC在控制移植排斥反应中的作用机制主要在于其与供者反应性T细胞的直接作用，从而诱导T细胞的失能、清除或者调节T细胞的产生。然而，这种观点尚未在体内实验中的到证实。我们使用典型的体外经VitaminD3培养的成熟抵抗（maturation-resistant，MR）DC，证明了经静脉注射携带供者抗原的MR-DC后，可以使直接途径和间接途径的T细胞反应受到抑制并延长移植心脏的存活时间。但是在利用转基因T细胞的研究中，实验结果显示MR-DC并未在体内直接调节T细胞的功能。与被广泛接受的观点相反，我们发现经静脉注射的MR-DC在体内存活时间很短并被受者DC内化、处理后将其抗原递呈至间接途径的CD4＋T细胞，导致了T细胞克隆的不完全活化和清除，增加了CD4＋FoxP3＋T细胞的相对比例而不影响其绝对数量。治疗性免疫抑制性DC的培养方法和活力，与其经静脉注射后抑制移植排斥反应的效果无关。我们还发现应用供者源性凋亡的或缺乏细胞表面MHC分子的MR-DC，可以同样有效的延长心脏移植物的存活时间，提示在体内起关键作用的是受者自身的抗原递呈细胞。与供者特异性输血相比较，静脉注射携带供者抗原的MR-DC治疗，延长小鼠心脏移植物存活时间的效果未见显著差别。本实验的结论认为：外源性DC经静脉注射后的功能为向受者抗原递呈细胞提供供者抗原；在本实验的模型中，是受者自身内源性DC介导了免疫抑制性外源性DC在调节心脏移植后移植排斥反应、延长心脏移植物有存活时间中的作用。运用治疗性外源性DC抑制移植排斥反应时，应考虑成本与效益的关系。
[Abstract]:Heart transplantation is an effective method for the treatment of end-stage heart disease. In recent years, although the short-term survival rate after transplantation has improved significantly, the long-term survival of the recipients has not been effectively improved. Because of the obvious deficiency of immunosuppressive drugs, the main causes of death after heart transplantation are all related to immune suppression (infection, malignant tumor) or deficiency (rejection, cardiac graft angiopathy, late graft failure). Immune rejection is the main obstacle that affects the long-term effect of transplantation and is the core problem in the field of heart transplantation. The research in the field of transplantation immunity is more focused on donor-specific immunomodulation, such as dendritic cell dendritic cell (DC) therapy. A large number of studies have revealed the mechanism of DC induction and maintenance of self tolerance, and in vitro culture of tolerance induced DCs for donor specific immune tolerance induction. Tolerance induction or immunosuppressive DC is immature. Mature resistant or otherwise activated DC.These DCs express MHC molecules, low level expression of costimulatory molecules, or even transmit inhibitory signals, can not normally synthesize cytokines that promote the response of Th1 cells. The mechanism of therapeutic immunosuppressive DC in controlling allograft rejection mainly lies in its direct interaction with donor reactive T cells, which induces T cell disability, clears or regulates T cell production. This view has not yet been confirmed in vivo experiments. We used a typical maturation-resistantase-resistant MRDCA in vitro cultured with VitaminD3 to demonstrate that MR-DC carrying donor antigen was injected intravenously. T cell response to both direct and indirect pathways can be inhibited and the survival time of the transplanted heart prolonged. But in the study of using transgenic T cells, The results showed that MR-DC did not directly regulate the function of T cells in vivo. Contrary to the widely accepted view, we found that intravenous MR-DC survived very short in vivo and was internalized by the recipient DC. After treatment, the antigen was presented to CD4+T cells through indirect pathway, which resulted in incomplete activation and clearance of T cell clones, increased the relative proportion of CD4+FoxP3+T cells without affecting the absolute number of CD4+FoxP3+T cells, and the culture methods and activities of therapeutic immunosuppressive DC. We also found that MR-DCwith donor-derived apoptosis or lack of MHC molecules on the cell surface could also prolong the survival time of cardiac grafts. Compared with donor-specific blood transfusion, the effect of intravenously injected MR-DC with donor antigen on prolonging the survival time of heart grafts in mice was not significantly different. The conclusion of this experiment is that the function of exogenous DC after intravenous injection is to provide donor antigen to the recipient antigen presenting cell, and in the model of this experiment, It is that endogenous DC mediates the role of immunosuppressive exogenous DC in regulating allograft rejection and prolonging the survival time of cardiac grafts. The relationship between cost and benefit should be considered.
【学位授予单位】：哈尔滨医科大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：R392

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