Mechanistic insights into B7 co-stimulation

描述（由申请人提供）：共同刺激T细胞导致其扩增和激活。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性T细胞的启动中起关键作用。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的启动、扩增和死亡所必需的。虽然这些分子在一些体外实验中表现相似，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小鼠患糖尿病加速。然而，当B7-2缺失时，NOD小鼠完全免受疾病的侵害。人们提出了许多假设来解释这些不同的观察结果。事实上，如果这些共刺激分子的作用能够被理解，就可以设想新的疗法来治疗自身免疫性疾病，而不干扰整个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。三个相互关联的假设将被检验。最初的一组实验验证了一个假设，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胞质尾部PKC磷酸化位点的结构差异。具体来说，我们将确定在缺乏每条链的情况下PKC是否会发生差异激活。第二种假设是B7-1和B7-2对小鼠体内大量T细胞群的扩增和稳定性有不同的影响。这将通过BrdU结合研究进行测试，并使我们能够确定在缺乏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在T细胞的细胞周期中调节进程存在差异。我们建议通过实验来确定在缺乏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，所获得的机制信息将解决我们在共同刺激和自身免疫之间关系方面的知识空白，允许未来更具体的治疗干预。

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.