T cell costimulation through the immunological synapse

描述（由申请人提供）：随着年龄的增长，免疫反应急剧减弱。有许多因素导致这种现象，其中之一是CD4 T细胞激活的内在缺陷。T细胞激活发生在免疫突触的背景下，其中受体、细胞骨架元件和信号分子在T细胞：APC相互作用位点被组织成离散的结构域。在成熟突触中，中央区域cSMAC包含TCR、CD28、信号成分（PKCtheta）和分泌成分。外周区pSMAC包含LFA-1和相关蛋白talin和RAPL。磷酸酶CD45被募集到T细胞：APC相互作用的位点，但在很大程度上被排除在突触之外。最近的证据表明，TCR信号发生在突触外部形成的微簇中，而cSMAC是TCR信号下调的一个位点。相反，我们发现CD28共刺激发生在cSMAC区域，通过募集PKCtheta和上调IL-2转录。此外，我们发现lfa -1依赖性pSMAC的形成是排除CD45所必需的，这与通过TCR的近端信号传导增加有关。因此，通过CD28和LFA-1的T细胞共刺激可能是通过免疫突触内的蛋白质组织介导的。有充分的证据表明，CD28和LFA-1功能在老年个体的T细胞中减弱。因此，该应用的中心假设是，衰老导致CD28和/或LFA-1或其相关蛋白分别靶向cSMAC或pSMAC的能力出现特定缺陷，这导致近端T细胞信号传导减少，这将部分解释老年人CD4 T细胞中T细胞活化的内在缺陷。我们将在两个目标中验证这一中心假设：(1)确定老年小鼠T细胞中免疫突触内外的CD28信号是否下调；(2)确定老年小鼠T细胞中LFA-1粘附和/或免疫突触组织是否被破坏。我们将使用TCR转基因、cd28缺陷和lfa -1缺陷小鼠，并结合免疫荧光显微镜、活细胞成像和分子分析。我们将确定衰老是否会影响T细胞：APC粘附的动力学、效率或TCR、LFA-1、CD28或相关蛋白进入免疫突触的募集和组织的大小。我们将确定LFA-1和/或cd28相关信号事件是否存在相应的缺陷，以及这些共刺激信号的功能后果是否存在改变。最后，如果在任何这些事件中发现缺陷，我们将解决在衰老过程中导致LFA-1和/或CD28功能丧失的特定分子过程。免疫反应在衰老过程中急剧减弱，部分原因是T细胞信号的缺陷。这个项目的总体目标是确定导致这种缺陷的精确的细胞和分子事件。我们希望了解这一衰老过程背后的机制将有助于开发特异性免疫增强剂，以抵消这些事件并促进老年人的有效免疫反应。

DESCRIPTION (provided by applicant): The immune response is dramatically attenuated during aging. There are a number of factors that contribute to this phenomenon, one of which is an intrinsic defect in CD4 T cell activation. T cell activation takes place in the context of the immunological synapse, where receptors, cytoskeletal elements, and signaling molecules are organized into discreet domains at the T cell: APC interaction site. In the mature synapse the central region, cSMAC, contains the TCR, CD28, signaling components (PKCtheta), and secretory components. The peripheral region, pSMAC, contains LFA-1 and associated proteins talin and RAPL. The phosphatase, CD45, is recruited to the site of T cell: APC interaction, but largely excluded from the synapse. Recent evidence indicates that TCR signaling takes place in microclusters that form at the outside of the synapse and the cSMAC is a site of downmodulation of TCR signaling. In contrast, we have found that CD28 costimulation occurs within the cSMAC region, through the recruitment of PKCtheta and upregulation of IL-2 transcription. In addition, we have found that LFA-1-dependent formation of the pSMAC is required for the exclusion of the CD45 and this correlates with an increase in proximal signaling through the TCR. Thus, T cell costimulation through CD28 and LFA-1 may be mediated through the organization of proteins within the immunological synapse. There is good evidence that CD28 and LFA-1 functions are diminished in T cells from aged individuals. Thus the central hypothesis of this application is that aging results in a specific defect in the ability to target CD28 and/or LFA-1, or their associated proteins, to the cSMAC or pSMAC respectively and this results in a decrease in proximal T cell signaling that will account in part for the intrinsic defect in T cell activation in CD4 T cells from aged individuals. We will test this central hypothesis in 2 Aims: (1) Determine whether CD28 signaling within and/or outside the immunological synapse is downmodulated in T cells from aged mice and (2) Determine whether LFA-1 adhesion and/or immunological synapse organization is disrupted in T cells from aged mice. We will use TCR transgenic, CD28-deficient and LFA-1-deficient mice and a combination of immunofluorescent microscopy, live cell imaging, and molecular analysis. We will determine whether aging effects T cell: APC adhesion the kinetics, efficiency, or magnitude of recruitment and organization of TCR, LFA-1, CD28, or associated proteins into the immunological synapse. We will determine whether there is a corresponding defect in LFA-1 and/or CD28-associated signaling events and whether there is an alteration in the functional consequences these costimulatory signals. Finally, if a defect is noted in any of these events we will address the specific molecular process that accounts for a loss in LFA-1 and/or CD28 function during aging. The immune response is dramatically attenuated during aging in part due to a defect in T cell signaling. The overall goal of this project is to determine the precise cellular and molecular events that account for this defect. We hope that understanding the mechanism behind this aging process will facilitate the development of specific immuno-enhancers that can counteract these events and promote effect immune responses in older individuals.