Mechanistic insights into B7 co-stimulation

描述(申请人提供)：共刺激T细胞导致其扩张和激活。CD28/B7通路是调节免疫和自身免疫的中枢共刺激通路。CD28信号在引发自身免疫性糖尿病的致病T细胞的启动过程中起着关键作用。CD28的两个关键刺激配体B7-1和B7-2是T细胞在其生命周期中启动、扩增和死亡所必需的。虽然这些分子在一些体外试验中表现相似，但它们对NOD小鼠自身免疫的发展有不同的影响。当B7-1缺失时，NOD小鼠就会患上加速糖尿病。然而，当B7-2缺失时，NOD小鼠就完全免受疾病的侵袭。已经提出了许多假说来解释这些不同的观察结果。事实上，如果能够理解这些共刺激分子的作用，就可以设想在不干扰整个T细胞库的情况下治疗自身免疫性疾病的新疗法。这项应用的中心目标是阐明解释B7-1和B7-2作用中观察到的生物学差异的机制。三个相互关联的假说将被检验。最初的一组实验测试了这样一个假设，即进入ARC的自外向内信号会区分B7-1和B7-2的作用。这一假说是基于B7-2和B7-1细胞质尾部的结构和PKC磷酸化位点的差异。具体地说，我们将确定在没有每个链的情况下，是否会发生差异的PKC激活。第二个假设是，B7-1和B7-2对小鼠体内大量T细胞的扩增和稳定性有不同的影响。这将通过BrdU掺入研究进行测试，并将使我们能够确定在没有B7-1或B7-2的情况下T细胞亚室的复制率。最后，我们假设B7-1和B7-2通过细胞周期不同地调节T细胞的进程。我们建议进行实验，以确定在缺乏B7-1和B7-2的情况下，调节细胞周期的关键通路是否受到干扰。我们相信，获得的机械性信息将填补我们关于协同刺激和自身免疫之间关系的新知识空白，从而在未来进行更具体的治疗干预。

DESCRIPTION (provided by applicant): Co-stimulation of T cells leads to their expansion and activation. The CD28/B7 pathway is the central costimulatory pathway regulating immunity and autoimmunity. CD28 signaling is pivotal in the priming of pathogenic T cells that cause autoimmune diabetes. Two critical stimulatory ligands for CD28, B7-1 and B7- 2, are required for the priming, expansion, and demise of T cells during their life cycle. While these molecules behave similarly in some in vitro assays, they have divergent effects on the development of autoimmunity in the NOD mouse. When B7-1 is missing, NOD mice suffer from accelerated diabetes. However, when B7-2 is missing, NOD mice are completely protected from the disease. There have been a number of hypotheses put forth to explain these divergent observations. Indeed, if the actions of these costimulatory molecules could be understood, new therapies could be envisioned to treat autoimmune disease, without disturbing the entire T cell repertoire. The central goal of this application it to elucidate the mechanisms that explain the biological distinctions observed in the actions of B7-1 and B7-2. Three interlocking hypotheses will be tested. The initial set of experiments test the hypothesis that outside-in signaling into the ARC differentiates the actions of B7-1 and B7-2. This hypothesis is based upon differences between the structures and PKC phosphorylation sites of the cytoplasmic tails of B7-2 and B7-1. Specifically, we will determine whether differential PKC activation occurs in the absence of each chain. The second hypothesis is that B7-1 and B7-2 differentially affect the expansion and stability of bulk T cell populations in the mouse. This will be tested through BrdU incorporation studies and will allow us to determine the replication rate of T cell subcompartments in the absence of B7-1 or B7-2. Lastly, we hypothesize that B7-1 and B7-2 differentially regulate progression through the cell cycle in T cells. We propose to perform experiments to determine whether key pathways that regulate the cell cycle are perturbed in the absence of B7-1 and B7-2. We believe that the mechanistic information gained will address novel gaps in our knowledge regarding the relationship between co-stimulation and autoimmunity, allowing for more specific therapeutic intervention in the future.