INTRATHYMIC TRANSPLANTATION TOLERANCE BY MHC PEPTIDES

器官移植是终末期器官衰竭的首选治疗方法。 移植研究的主要目标是诱导对 主要组织相容性复合体（MHC）抗原。 胸腺扮演着 在自我耐受性的发展中发挥重要作用，但其在获得性免疫中的作用 对同种异体抗原的耐受性是未知的。 几名调查人员最近 表明将供体细胞胸腺内注射到成年动物体内， 诱导对组织和器官长期特异性无应答状态 同种异体移植 MHC基因序列数据的可用性使得 有可能合成多态性肽并利用它们进行研究， 同种异体识别的机制。 胸腺内注射多形核甘酸 MHC同种异体肽复制了同种异体 细胞，表明胸腺细胞识别加工的MHC分子。 的 这项建议的主要重点是使用合成的MHC肽来研究 大鼠胸腺内获得性耐受的机制 血管化器官同种异体移植。 具体而言，该计划将：1. 探讨胸腺识别MHC异源肽的机制。 这 将通过研究哪些胸腺抗原呈递细胞， 骨髓来源的巨噬细胞/树突细胞或上皮细胞， 并将MHC同种异体肽呈递给T细胞。 方法将包括绑定 生物素化MHC肽的研究，确定对 加工和阻断特异性抗I类和II类MHC 克隆抗体 T细胞对特定MHC表位的应答 在通过用肽免疫和通过同种异体移植物引发后， 下定决心。 2. 研究胸腺调节细胞的作用。 的 将使用大鼠肾脏和心脏移植模型。 的存在 调节机制将通过进行胸腺切除术来研究， 移植后不同时间间隔，进行过继性 移植实验，研究移植物浸润细胞和细胞因子 通过免疫组织学。 3. 研究胸腺是否识别MHC 肽使活化的T细胞克隆失能或缺失。 这将涉及 通过注射诱导对特异性MHC表位的免疫无应答性 单个MHC肽进入胸腺，并使用体外增殖 和前体频率测定来研究 来自耐受动物的T细胞。 无反应性将通过测试进行研究， 通过细胞因子逆转T细胞无反应性。 克隆缺失将是 通过分析T细胞受体Vbeta库来研究。 长期 目的是开发新的方法来研究的机制， 移植无反应，包括新的策略，以诱导 特异性移植耐受

Organ transplantation is the therapy of choice for end stage organ failure. The major goal in transplantation research is the induction of tolerance to major histocompatibility complex (MHC) antigens. The thymus plays the major role in development of self tolerance, but its role in acquired tolerance to alloantigen is unknown. Several investigators have recently shown that intrathymic injection of donor cells into adult animals can induce a state of long term specific unresponsiveness to tissue and organ allografts. The availability of sequence data for the MHC genes has made it possible to synthesize polymorphic peptides and utilize them to study the mechanisms of allo-recognition. Intrathymic injection of polymorphic MHC allopeptides reproduces the same effects observed with allogeneic cells, suggesting that thymocytes recognize processed MHC molecules. The main focus of this proposal is to use synthetic MHC peptides to study the mechanisms of acquired intrathymic tolerance in the rat model of vascularized organ allografts. Specifically, the plan will be to: 1. Investigate the mechanisms of thymic recognition of MHC allopeptides. This will be accomplished by studying which thymic antigen-presenting cells, bone marrow-derived macrophages/dendritic cells or epithelial cells, bind and present MHC allopeptides to T cells. Methods will include binding studies of biotinylated MHC peptides, determining the requirement for processing, and blocking with specific anti-class I and class II MHC monoclonal antibodies. The response of T cells to specific MHC epitopes after priming by immunization with the peptides, and by an allograft, will be determined. 2. Investigate the role of thymic regulatory cells. The rat renal and cardiac transplant model will be used. The presence of regulatory mechanisms will be investigated by performing thymectomies at different time intervals after transplantation, performing adoptive transfer experiments, and studying graft infiltrating cells and cytokines by immunohistology. 3. Investigate whether thymic recognition of MHC peptides anergizes or deletes activated T cell clones. This will involve induction of immune unresponsiveness to specific MHC epitopes by injecting individual MHC peptides into the thymus, and using in vitro proliferation and precursor frequency assays to study the functional characteristics of T cells from tolerized animals. Anergy will be studied by testing for reversal of T cell unresponsiveness by cytokines. Clonal deletion will be investigated by analyzing T cell receptor Vbeta repertoire. The long term objectives are to develop novel approaches to study the mechanisms of transplantation unresponsiveness, including new strategies to induce specific transplantation tolerance.