Decoding human T-cell allospecificity

摘要 CD8+T细胞是移植组织急性细胞排斥反应的主要驱动力。而T细胞可以 直接(通过对allo-HLA的直接反应)和间接(通过别肽)识别同种异体抗原 主要的共识是直接识别在ACR中起主要作用。然而，很多都是 对导致直接ACR的T细胞的生物学未知。几十年来，同种异体反应性T细胞 被认为要么主要对allo-HLA上的独特决定因素(以HLA为中心的反应)做出反应，要么对 由allo-HLA(以肽为中心)呈现的过多的非我多肽。然而，最近的数据表明， 许多同种异体反应性T细胞是同种异体特异性的，对存在于T细胞表面的独特的多肽/异基因MHC复合体作出反应 异体移植的表面。此外，更多的数据表明，同种异体反应性T细胞可能与 免疫优势病毒表位，实际上可能源自先前存在的内存池。在不断增长的同时 关于同种异体反应性T细胞的结构特征和免疫起源的清楚，缺乏知识 关于同种异体反应性T细胞的特性是我们对T细胞生物学认识有限的一个主要原因。 介导的ACR。我们现在准备在这一领域取得实质性突破，并利用它更好地 大体了解ACR和同种异体反应性。在最初的研究中，对活检和尿液进行scRNA测序 从几名接受肾移植排斥反应的患者中，我们发现了一个显著且出人意料的小 具有唯一TCR CDR3a/b序列的克隆性扩增的T细胞的数量(约10-20个/患者)，并具有 证实了它们对移植组织的特异性。这些扩增的T细胞克隆持续了几个月 排斥同种异体移植，尽管传统的抗排斥治疗。这种雄心勃勃、高风险/高回报的目标 该项目是在移植活检中识别同种异体反应性T细胞识别的配体，包括两者 同种异体抗原和任何交叉反应的病毒表位，并利用这一知识开始破译免疫生物学 确定可能的治疗靶点，并扩大我们对ACR的性质和起源的理解 同种异体反应。我们的具体假设是：(I)大多数克隆扩展的同种异体TCR识别 由allo-HLA呈递的独特的组织限制性多肽；(Ii)许多这些TCR也与 由自身人类白细胞抗原呈递的病毒表位；以及(Iii)识别多肽靶点将使我们能够解码 肾移植中同种异体特异性T细胞的转录。这项多PI R21提案的成功将为 对同种异体反应性、移植排斥反应和新的治疗调节进行大量、更深入、开创性的研究 ACR.

Summary CD8+ T cells are the main drivers of acute cellular rejection (ACR) of transplanted tissues. While T cells can recognize alloantigens directly (through direct responses to allo-HLA) as well as indirectly (through allopeptides bound to self-HLA), the major consensus is that direct recognition plays a major role in ACR. However, much is unknown about the biology of T cells responsible for direct ACR. For decades, alloreactive T cells have been viewed as either responding primarily to unique determinants on allo-HLA (HLA-centric responses), or to a plethora of non-self peptides presented by allo-HLA (peptide-centric). Recent data though has suggested that many alloreactive T cells are allospecific, responding to unique peptide/allo-MHC complexes present on the surface of allografts. Moreover, additional data suggests that alloreactive T cells may share reactivities with immunodominant viral epitopes and may in fact derive from pre-existing memory pools. While there is growing clarity around the structural features and immunological origins of alloreactive T cells, the lack of knowledge regarding the specificities of alloreactive T cells is a major reason for our limited biologic insight into T cell- mediated ACR. We are now poised to make a substantial breakthrough in this area and capitalize on it to better understand ACR and alloreactivity in general. In initial studies, using scRNA sequencing on biopsies and urine from several patients undergoing kidney transplant rejection, we found a remarkably and unexpectedly small number (~10-20/patient) of clonally expanded T cells with unique TCR CDR3 a/b sequences, and have confirmed their specificity towards the transplanted tissue. These expanded T cell clones persist for months in rejecting allografts, despite traditional anti-rejection therapy. The goal of this ambitious, high risk/high reward project is to identify the ligands recognized by alloreactive T cells within transplant biopsies, including both alloantigens and any cross-reactive viral epitopes and use this knowledge to begin decoding the immunobiology of ACR, identify possible therapeutic targets, and expand our understanding of the nature and origins of alloreactivity. Our specific hypotheses are that (i) the majority of clonally expanded allospecific TCRs recognize unique tissue restricted peptides presented by allo-HLA; (ii) many of these TCRs are also cross-reactive with viral epitopes presented by self-HLA; and (iii) identification of peptide targets will enable us to decode the transcriptomes of allospecific T cells in kidney allografts. Success in this multi-PI R21 proposal will pave the way for numerous, deeper, groundbreaking studies of alloreactivity, graft rejection, and novel therapeutic modulation of ACR.