Exosomes, Dendritic Cells and Transplant Tolerance

描述(由申请人提供)： 移植物排斥反应的主要原因是受体体内激发的同种抗原(Ag)特异性T细胞免疫反应。树突状细胞(DC)是一种专职的抗原提呈细胞(APC)，作为“乘客白细胞”将供者的同种异体抗原递呈给幼稚的T细胞，引发移植物排斥反应。除了在免疫和移植排斥反应中的作用外，吞噬凋亡小泡的DC还表现出免疫调节APC的特征，似乎参与了稳定状态下外周耐受的诱导。然而，凋亡小泡并不是唯一可能影响DC生物学的细胞外小泡。DC能内化胞外外体，胞外是一群来自内体的小膜泡(&lt；100 nm)，富含MHC分子，在细胞外空间中含量丰富。DC能够在MHC分子中呈递外体衍生的别肽。有证据表明，外切体和凋亡囊泡一样，可能通过与APC的相互作用参与外周耐受的诱导。我们建议研究DC-Exosome的相互作用，并验证供体来源的MHC+Exosome内化和加工后，受体DC能够产生具有调节功能的allo-Ag特异性T细胞的假设。我们预计这种相互作用将有两个重要的影响：1)受体DC呈现供体MHC+外体衍生别肽+自身MHC干扰同种异体识别的间接途径；ii)由于受体未成熟DC表达供体MHC+外体衍生别肽+自身MHC的T细胞共刺激分子水平较低，将指示受体异体抗原特异性T细胞成为凋亡、无能或调节性T(Treg)细胞。与大多数已报道的诱导DC移植耐受的技术不同，我们的方法特别针对器官排斥反应中同种异体识别的间接途径。我们建议探索这种方法来诱导同种异体心脏移植受者的抗原特异性耐受，以此作为药物治疗的替代方案，药物治疗会导致全身免疫抑制和有害的副作用。所获得的知识将加强对耐受和排斥是如何调节的理解，并将阐明DC和外切体用于移植的治疗潜力。我们提出了以下目标：目的1：研究DC与外切体的相互作用及其对DC生物学的影响。目的：研究外切小体在体内的转运，并研究外切小体暴露的DC对T细胞的杀伤能力。目的：探讨供体MHC+外切体或受体树突状细胞暴露于供体MHC+外切体对心脏移植物存活的影响。比较供体-MHC+外切体与供体-MHC+凋亡细胞的作用。

DESCRIPTION (provided by applicant): The main cause of graft rejection is the allo-antigen (Ag)-specific T cell immune response elicited within the recipient. Dendritic cells (DCs) are the professional Ag-presenting cells (APCs) that as "passenger leukocytes" present donor alloAg to naive T cells and trigger graft rejection. Besides their role in immunity and transplant rejection, DCs that have phagocytosed apoptotic vesicles exhibit characteristics of immunoregulatory APCs and seem to be involved in induction of peripheral tolerance in the steady-state. However, apoptotic vesicles are not the only extracellular vesicles that may affect DC biology. DCs can internalize extracellular exosomes, a population of small membrane vesicles (< 100 nm) of endosomal origin, rich in MHC molecules and abundant in the extracellular space. DCs are able to present exosome-derived allopeptides in MHC molecules. There is evidence that exosomes, like apoptotic vesicles, may participate in induction of peripheral tolerance probably through interaction with APCs. We propose to study the DC-exosome interaction and to test the hypothesis that after internalization and processing of donor-derived MHC + exosomes, recipient DCs are able to generate allo-Ag specific T cells with regulatory function. We expect that this interaction will have two important effects: i) recipient DCs will present the donor MHC + exosome-derived allopeptides + self-MHC interfering with the indirect pathway of allorecognition, and ii) due to their low levels of T cell costimulatory molecules, recipient immature DCs expressing donor MHC + exosome-derived allopeptides + self-MHC will instruct recipient alloAg-specific T cells to become apoptotic, anergic, or regulatory T (Treg) cells. Unlike most of the techniques reported in effort to induce transplant tolerance with DCs, our approach targets specifically the indirect pathway of allorecognition in organ rejection. We propose to explore this approach to induce Ag-specific tolerance in heart allograft recipients as an alternative to pharmacological treatment that induces generalized immunosuppression and harmful side effects. The knowledge gained will enhance understanding of how tolerance and rejection are regulated, and will clarify the therapeutic potential of DCs and exosomes for transplantation. We propose the following aims: AIM 1: To investigate the interaction of DCs with exosomes and its impact on DC biology. AIM 2: To study the trafficking of exosomes in vivo and to characterize the T cell stimnlatory capacity of exosome-exposed DCs. AIM 3: To investigate the effect of administration of donor MHC + exosomes or recipient DCs exposed to donor MHC + exosomes on heart allograft survival. To compare the effects of donor-MHC + exosomes with donor-MHC + apoptotic cells.