TIM molecules and the innate: adaptive interface in alloimmunity

描述(申请人提供)：移植是终末期器官衰竭患者的一种挽救生命的程序。目前的免疫抑制与显著的发病率和慢性移植功能障碍的高发生率有关，这使得诱导抗原特异性耐受成为一种理想的替代方案。TIM分子的治疗操作被认为具有巨大的耐受性潜力。与其他TIM家族成员不同，TIM-4主要表达在APC上，包括CD11c+DC和巨噬细胞。尽管利用TIM-4Ig融合蛋白的体外研究表明，它与T细胞上的共刺激分子配体结合，但结果相互矛盾，共刺激信号的性质也没有很好的界定。此外，由于这些共培养缺乏APC，因此未检测到TIM-4对DC的生理作用。TIM-4最近也被确定为一种磷脂酰丝氨酸受体，能够通过引导吞噬凋亡小体来调节免疫系统。这些角色在指导免疫反应方面的相对贡献尚不清楚。本申请的主要目的是探讨TIM-4在同种异体免疫中的作用。我们发现，抗体介导的阻断TIM-4诱导同种异体胰岛移植物长期存活，提示TIM-4在体内调节同种异体免疫中起主要作用。我们还发现，TIM-4在功能上定义了不同的DC亚群，参与了T辅助细胞命运的决定。此外，TIM-4阻断可抑制由TIM-4+DC启动的TIM-4信号转导和巨噬细胞介导的吞噬功能，导致凋亡小体聚集在脾内，吞噬功能由巨噬细胞向DC转移。这些功能对抗TIM-4对移植物存活的显著影响的相对贡献尚不清楚，这是本提案的中心焦点。我们推测，抗TIM-4的移植物延长是由于抑制了TIM-4信号转导DC和/或抑制了T细胞的共刺激。另外，TM-4阻断可能改变DC/巨噬细胞的激活状态，从而改变同种异体移植物的存活，将凋亡细胞吞噬的责任从巨噬细胞转移到DC。因此，本研究的具体目标是：1.TIM-4在DC表型和功能调节中的作用；2.DC和巨噬细胞上的TIM-4在同种异体移植物存活中的作用？3.TIM-4在体内调节同种异体反应性T细胞命运的机制是什么？这些研究不仅将为DC和Th分化的免疫生物学提供全新的基础见解，而且将使我们能够通过选择性抑制DC和/或巨噬细胞上的Tim-4功能来优化促进同种异体移植物存活的策略。此外，从拟议的研究中获得的见解将具有广泛的治疗潜力，包括在自身免疫和过敏方面开发耐受性策略，而操纵这种分子也可以用于增强免疫反应，这将在相对免疫缺陷状态(癌症和慢性感染)和疫苗开发中有用。

DESCRIPTION (provided by applicant): Transplantation is a life-saving procedure for patients with end-stage organ failure. Current immuno- suppression is associated with significant morbidity and a high incidence of chronic transplant dysfunction, rendering the induction of antigen-specific tolerance a desirable alternative. Therapeutic manipulation of the TIM molecules is thought to have great tolerogenic potential. In contrast to the other TIM family members, TIM- 4 is primarily expressed on APCs, including CD11c+ DCs and macrophages. Although in vitro studies utilizing TIM-4 Ig fusion proteins demonstrate that it binds costimulator ligands on T cells, the results are conflicting and the nature of costimulatory signals not well defined. Furthermore, as these co-cultures lacked APCs, the physiological role of TIM-4 on DCs was not examined. TIM-4 has also recently been identified as a phosphatidylserine receptor, capable of modulating the immune system by directing engulfment of apoptotic bodies. The relative contribution of these roles in directing immune responses remains unclear. The primary objective of this application is to address the role of TIM-4 in alloimmunity. We show that antibody-mediated blockade of TIM-4 induces long-term islet allograft survival, suggesting that TIM-4 plays a major role in regulating alloimmunity in vivo. We have also discovered that TIM-4 defines functionally distinct DC subsets involved in the determination of T helper cell fate. Furthermore, TIM-4 blockade inhibits both TIM-4 signaling initiated by TIM-4+ DCs and phagocytosis mediated by macrophages, resulting in the splenic accumulation of apoptotic bodies and a shift of phagocytic duty from macrophages to DCs. The relative contribution of these functions to the marked effect of anti-TIM-4 on graft survival is unknown and is the central focus of this proposal. We hypothesize that the graft prolongation achieved by anti-TIM-4 is due to inhibition of TIM-4 signaling to DCs and/or inhibition of T cell costimulation. Alternatively, TM-4 blockade may alter the activation status of DCs/macrophages and, consequently, allograft survival, by shifting the responsibility of apoptotic cell phagocytosis from macrophages to DCs. Thus, the specific aims are: 1. What is the role of TIM-4 in the regulation of DC phenotype and function? 2. What is the role of TIM-4 on DCs versus macrophages in allograft survival? 3. What are the mechanisms whereby TIM-4 regulates the fate of alloreactive T cells in vivo? These studies will not only provide brand new basic insight into the immunobiology of DCs and Th differentiation, but will allow us to optimize strategies for promoting allograft survival, by selectively inhibiting TIM-4 function on DCs and/or macrophages. Moreover, the insights gained from the proposed studies will have broad therapeutic potential, including the development of tolerogenic strategies in autoimmunity and allergy, while manipulation of this molecule could also be used to enhance the immune response, which would be useful in states of relative immunodeficiency (cancer and chronic infection) and in vaccine development.