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的改善，但排斥反应仍然是导致 长期的移植损失。先天免疫激活增强了获得性免疫，并在 引发急性排斥反应，防止移植耐受。然而，大多数免疫抑制药物用于 临床主要针对T细胞，而不是天然免疫细胞。因此，有一种尚未得到满足的需求，即开发有效的 移植中调节先天免疫的治疗方法。Siglec(唾液酸结合免疫球蛋白样凝集素)-E，或 SiGe是一种先天受体，可以下调炎症反应。SiGe由树突状细胞(DC)表达并抑制 TLRs引发的炎症反应。SiGe的参与是促进免疫调节的一种有前景的策略。 然而，SiGe在移植中的作用还没有被研究。我们发现缺乏SiGe的同种异体移植物 有加速排斥反应，肾移植患者人类SiGe同源基因表达减少 (Siglec-9)在拒绝期间。此外，我们最近发现一种分枝杆菌蛋白DNAK可以与 SiGe对同种异体免疫有很强的免疫调节作用 MHC II和CD86。DNAK原位靶向供体DC能延长大鼠同种异体皮肤移植存活时间 缺乏全身免疫抑制和DNAK效应依赖于SiGe。因此，瞄准SiGe代表着 一个新的潜在的治疗靶点，以增强移植免疫反应的调节。基于 我们的初步数据，我们假设SiGe是以下免疫反应的关键调节因子 移植。为了解决这一假设，我们提出了三个具体的目标：1)定义SiGe在 调节DC成熟和抗原处理；2)确定SiGe在同种异体免疫和在 抗原特异性T细胞的产生；以及3)研究一种新的免疫调节分子，该分子基于 Siglec-9与DNAK的相互作用。为了实现这些目标，我们将利用心脏和人性化的老鼠 针对SiGe，SiGe缺陷小鼠的新型合成激动肽移植模型，抗原特异性T细胞的示踪 细胞采用过继转移细胞，内源性染色采用四聚体。建议的研究具有创新性。 而且意义重大，因为我们将探索一种重要的调节先天免疫受体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,