Molecular studies of lipid presentation and T cell recognition of CD1c

描述（由申请人提供）：CD1c是CD1蛋白家族的一员，其结构与主要组织相容性复合体I类分子相似。CD1分子已经进化出独特的脂质结合口袋（称为A‘和F’），非常适合通过它们的疏水碳氢化合物尾部结合各种脂质抗原。CD1c属于人类CD1分子的1族；小鼠体内缺乏同源物。由于我们缺乏一种可处理的模型来探测1组CD1分子的功能，因此对CD1c的免疫功能和识别它的T细胞知之甚少。我们最近的CD1c晶体结构揭示了这一主题，揭示了该分子的几个独特特征，使其具有结合多种抗原的能力。该结构还显示了CD1c如何呈现结核分枝杆菌（MPM）的细胞壁脂质，这是疫苗开发的关键潜在靶点，并提供了十二聚体N端酰化脂肽（“lipo12”）如何也可以呈现的线索。然而，目前尚不清楚CD1c如何呈现其他脂质，这种复合物如何被T细胞识别，以及什么特征决定了CD1c特异性的T细胞库（以及这是否随着不同的脂质抗原而变化）。为了解决这些问题，更充分地了解CD1c及其在向T细胞呈递不同脂质的作用，我们将采用以下策略：我们的第一个目标，“表征CD1c脂质呈递的生物物理和结构细节”，重点是了解CD1c呈递的结构特征以及内在（脂质结构）和外在（pH和伴侣）因素如何调节CD1c的脂质谱。我们的第二个目标是“定义TCRs如何在分子水平上识别CD1c/脂质配体”，重点是使用结构、生物物理和功能方法来揭示TCRs如何在分子水平上识别CD1c/脂质。这是一个与全球理解T细胞识别相关的关键问题：不同的T细胞如何“看到”CD1分子？这种识别是否类似于经典的TCR/ mhc ？还是有一些特征让人想起自然杀伤T细胞对CD1d的不变识别？目前我们还没有这方面的消息。最后，我们的第三个目标，“表征识别CD1c的T细胞库”，将侧重于识别CD1c响应的T细胞库，并表征这些T细胞的细胞表面标记（共受体，记忆标记），效应功能（细胞因子分泌和/或细胞毒性）及其tcr序列，特别是确定CDR回路中是否存在用于该识别过程的基序。我们将从健康和患病个体中探索人类库，并将利用人源化CD1c小鼠模型来探索那里的T细胞库。目前，我们对CD1c对人体免疫的贡献的了解尚处于起步阶段，但其在病原体识别（如结核分枝杆菌）中的重要性已经得到明显的暗示。我们的建议将扩大我们对CD1c脂质表现和对其反应的T细胞的理解。

DESCRIPTION (provided by applicant): CD1c is a member of the CD1 family of proteins that are similar in structure to Major Histocompatibility Complex class I molecules. CD1 molecules have evolved unique lipid binding pockets (called A' and F') ideally suited for binding diverse lipid antigens via their hydrophobic hydrocarbon tails. CD1c falls into the Group 1 family of CD1 molecules found in humans; homologues are lacking in the mouse. Because we lack a tractable model by which to probe the function of Group 1 CD1 molecules, little is known about the immunological function of CD1c and the ¿¿ T cells that recognize it. Our recent crystal structure of CD1c shed light on this topic, revealing several unique features of this molecule that endows it with the capacity to bind diverse antigens. This structure also showed how CD1c presents a cell-wall lipid of Mycobacterium tuberculosis (MPM), a key potential target for vaccine development, and provides clues as to how a dodecameric N- terminally acylated lipopeptide ("lipo12") can also be presented. However, it is still unknown how CD1c presents other lipids, how this complex is recognized by ¿¿ T cells, and what characteristics dictate the ¿¿ T cell repertoire specific for CD1c (and whether this changes with different lipid antigens). In order to address these questions and more fully understand CD1c and its role in presenting diverse lipids to ¿¿ T cells, we will use the following strategies: our first aim, "To characterize the biophysical and structural details of CD1c lipid presentation." is focused on understanding the structural features of CD1c presentation and how intrinsic (lipid structure) and extrinsic (pH and chaperones) factors modulate CD1c's lipid repertoire. Our second aim, "To define how ¿¿ TCRs recognize CD1c/lipid ligands at the molecular level." is focused on using structural, biophysical and functional approaches to reveal how ¿¿ TCRs recognize CD1c/lipid at the molecular level. This is a key question relevant to globally understanding T cell recognition: How do diverse ¿¿ T cells "see" CD1 molecules? Is this recognition like classical ¿¿ TCR/MHC-like? Or are there features reminiscent of invariant Natural Killer T cell recognition of CD1d? Currently we have no information on this process. Finally, our third aim, "To characterize the repertoire of ¿¿ T cells that recognize CD1c." will focus on identifying the ¿¿ T cell repertoire that is CD1c responsive and to characterize these T cells for cell-surface markers (co-receptors, memory markers), effector functions (cytokine secretion and/or cytotoxicity) and the sequence of their TCRs, specifically to determine whether there are motifs in the CDR loops that are used in this recognition process. We will explore the human repertoire from health and diseased individuals and will make use of a humanized CD1c murine model to explore the T cell repertoire there. Currently our understanding of CD1c's contribution to human immunity is in its infancy, yet hints at its importance in pathogen recognition (such as M. tuberculosis) are already evident. Our proposal will expand our understanding of CD1c lipid presentation and the T cells that are reactive to it.