Role of Siglec-E in Regulating Alloimmunity

摘要 尽管器官移植的短期存活率有了显著提高，但排斥反应仍然是导致移植失败的主要原因。 长期移植失败先天性免疫激活增强了适应性免疫，并且在免疫应答中起关键作用。 引发急性排斥反应并阻止移植耐受。然而，大多数免疫抑制药物用于 临床主要针对T细胞而不是先天免疫细胞。因此，开发有效的 在移植中调节先天免疫的疗法。Siglec（唾液酸结合免疫球蛋白样凝集素）-E，或 SigE是一种下调炎症的先天受体。SigE由树突状细胞（DC）表达，并抑制 TLR引发的炎症反应。SigE的参与是促进免疫调节的有前途的策略。 然而，SigE在移植中的作用尚未研究。我们发现缺乏SigE的同种异体移植物 具有加速的排斥反应，并且肾移植患者具有减少的人SigE对应物的表达。 （Siglec-9）在排斥期间。此外，我们最近发现，分枝杆菌蛋白DnaK可以结合到 SigE在同种免疫中具有强效免疫调节作用，通过下调 MHC II和CD 86。用DnaK原位靶向供体DC能够延长皮肤移植物的存活， 不存在全身免疫抑制和DnaK效应依赖于SigE。因此，靶向SigE代表 一种新的潜在的治疗靶点，以增强移植中免疫应答的调节。基于 根据我们的初步数据，我们假设SigE是以下免疫应答的关键调节剂： 移植为了解决这一假设，我们提出了三个具体目标：1）定义SigE在 调节DC成熟和抗原加工; 2）确定SigE在同种异体免疫中的作用和在免疫应答中的作用。 抗原特异性T细胞的产生;和3）研究基于以下设计的新型免疫调节分子： Siglec-9和DnaK之间的相互作用。为了实现这些目标，我们将利用心脏和人源化小鼠 移植模型，一种新的合成的SigE激动剂肽，SigE缺陷小鼠，跟踪抗原特异性T细胞 使用过继转移的细胞和使用四聚体的内源性染色的细胞。拟议的研究是创新的 重要的是，我们将探索一种重要的调节性先天免疫受体SigE的生物学， 我们将研究一种新的SigE靶向分子来抑制同种异体免疫，

Abstract Despite the significant improvements in short-term survival of organ transplants, rejection remains a leading cause of long-term transplant loss. Innate immune activation potentiates the adaptive immunity and is a crucial player in precipitating acute rejection and preventing transplant tolerance. However, most immunosuppressive drugs used in the clinic primarily target T cells and not innate immune cells. Therefore, there is an unmet need to develop effective therapies to modulate innate immunity in transplantation. Siglec (sialic acid-binding immunoglobulin-like lectin)-E, or SigE, is an innate receptor that down-modulates inflammation. SigE is expressed by dendritic cells (DCs) and inhibits TLRs-triggered inflammatory responses. Engagement of SigE is a promising strategy to promote immune regulation. However, the role of SigE in transplantation has not been investigated. We have found that allografts lacking SigE have an accelerated rejection, and kidney transplant patients have decreased expression of human SigE counterpart (Siglec-9) during rejection. Moreover, we have recently discovered that a mycobacterial protein DnaK can bind to SigE with potent immunomodulatory effects in alloimmunity by decreasing DCs activation through downregulation of MHC II and CD86. In situ targeting of donor DCs with DnaK is capable of prolonging skin allograft survival in the absence of systemic immunosuppression and DnaK-effect was dependent on SigE. Thus, targeting SigE represents a novel potential therapeutic target to enhance the modulation of the immune response in transplantation. Based on our preliminary data, we hypothesize that SigE is a critical regulator of the immune response following transplantation. To address this hypothesis, we propose three specific aims: 1) To define the role of SigE in regulating DC maturation and antigen processing; 2) To determine the role of SigE in alloimmunity and in the generation of antigen-specific T cells; and 3) To investigate a novel immunomodulatory molecule designed based on the interaction between Siglec-9 and DnaK. To accomplish these aims, we will utilize heart and humanized mouse transplantation models, a novel synthetic agonist peptide to SigE, SigE-deficient mice, tracking of antigen-specific T cells using adoptive transferred cells and endogenous staining using tetramers. The proposed studies are innovative and significant because we will explore the biology of an important regulatory innate immune receptor, SigE, in transplantation and we will investigate a novel SigE targeting molecule to inhibit alloimmunity,