Mechanistic insights into B7 co-stimulation

描述（由申请人提供）：T细胞的共刺激导致其扩增和活化。CD 28/B7通路是调节免疫和自身免疫的中枢共刺激通路。CD 28信号传导在引发导致自身免疫性糖尿病的致病性T细胞中是关键的。CD 28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的引发、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小鼠中自身免疫的发展具有不同的影响。当B7-1缺失时，NOD小鼠患有加速糖尿病。然而，当B7-2缺失时，NOD小鼠完全免受疾病的影响。人们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，就可以设想新的治疗方法来治疗自身免疫性疾病，而不会干扰整个T细胞库。本申请的中心目标是阐明解释在B7-1和B7-2的作用中观察到的生物学差异的机制。将检验三个相互关联的假设。最初的一组实验测试了这一假设，即进入ARC的由外向内信号传导区分了B7-1和B7-2的作用。这一假设是基于B7-2和B7-1的胞质尾区的结构和PKC磷酸化位点之间的差异。具体来说，我们将确定是否差异PKC激活发生在每个链的情况下。第二个假设是B7-1和B7-2差异地影响小鼠中大量T细胞群的扩增和稳定性。这将通过BrdU掺入研究进行测试，并使我们能够确定在B7-1或B7-2不存在的情况下T细胞亚区室的复制率。最后，我们假设B7-1和B7-2通过T细胞的细胞周期差异调节进展。我们建议进行实验，以确定是否在B7-1和B7-2的情况下，调节细胞周期的关键途径受到干扰。我们相信，获得的机制信息将解决我们关于共刺激和自身免疫之间关系的知识中的新空白，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.