Novel pathways in T lymphocyte differentiation and function

产生针对不同感染因子的高亲和力抗体（即体液免疫）的能力是脊椎动物免疫系统的基本特性，并确保宿主存活。体液免疫反应需要B淋巴细胞（具有抗体产生潜力）和“辅助”T细胞之间高度协调的相互作用。这些相互作用由称为T滤泡辅助（Tfh）细胞的辅助性T细胞亚群介导，所述辅助性T细胞通过提供膜结合共刺激分子和分泌极化细胞因子而向B细胞提供直接帮助。我们先前已经表明，Tfh细胞提供了在免疫（King等，Nature Immunology，2012）和寄生蠕虫感染（King和Mohrs，Journal of Experimental Medicine，2009）的背景下产生体液免疫应答所需的白介素（IL）-4和IL-21的关键来源。该提案建立在这些发现的基础上，以确定以前未描述的分子和信号通路，这些分子和信号通路特异性地控制T细胞分化和功能。 为了发现Tfh细胞独特表达的分子，我们使用微阵列技术进行了初步实验，将该亚群与从感染肠道蠕虫的小鼠的发炎肠系膜淋巴结分离的其他CD 4 + T细胞亚群进行比较。我们的研究结果表明，Tfh细胞表达高水平的CD 109相比，其他CD 4 + T细胞。CD 109是一种糖磷脂酰肌醇锚定蛋白，在免疫系统中具有未知功能。使用角质形成细胞的功能研究表明，CD 109作为转化生长因子（TGF）-β 1信号传导的负调节剂，一种细胞因子，显着影响T效应细胞分化。我实验室的初步结果表明，关键的TGF-β 1靶基因，如SMAD 7在Tfh细胞中下调，这一发现与CD 109也在T细胞中负调节这一信号通路的观点一致。此外，CD 109已被证明可以调节STAT 3，STAT 3是一种促进Tfh细胞分化以及其他T效应子亚群的转录因子。因此，深入分析CD 109在T细胞生物学中的作用及其与TGF-b1和STAT 3依赖的淋巴细胞信号传导的潜在关系是必要的。在本申请中，我们提出了一项研究计划，通过追求3个特定目标来阐明CD 109在T细胞活化中的功能及其在控制T细胞分化和功能中的特异性： 1.确定CD 4 + T细胞表达CD 109的要求。 2.确定CD 109如何影响CD 4 + T细胞活化和分化。 3.识别激活的CD 4 + T细胞中的CD 109结合伴侣。 了解CD 109在T细胞分化和/或功能中的功能将为控制这一重要免疫细胞群体的分子机制提供新的见解。

The ability to generate high-affinity antibodies to diverse infectious agents (i.e. humoral immunity) is a fundamental property of the vertebrate immune system and ensures host survival. The humoral immune response requires highly coordinated interactions between B lymphocytes (which possess antibody-producing potential) and "helper" T cells. These interactions are mediated by a subset of helper T cells termed T follicular helper (Tfh) cells that provide direct help to B cells through provision of membrane-bound co-stimulatory molecules and secretion of polarizing cytokines. We have previously shown that Tfh cells provide critical sources of interleukin (IL)-4 and IL-21 required for the generation of humoral immune responses in the context of immunization (King et al, Nature Immunology, 2012) and parasitic helminth infection (King and Mohrs, Journal of Experimental Medicine, 2009). This proposal builds on these findings to identify previously undescribed molecules and signaling pathways that specifically control T cell differentiation and function. To discover molecules uniquely expressed by Tfh cells, we performed preliminary experiments using microarray technology comparing this subset to other CD4+ T cell subsets isolated from the inflamed mesenteric lymph nodes of mice infected with an intestinal helminth. Our results indicate that Tfh cells express high levels of CD109 compared to other CD4+ T cells. CD109 is a glycophosphatidylinositol-anchored protein with unknown function in the immune system. Functional studies using keratinocytes have demonstrated that CD109 acts as a negative regulator of transforming growth factor (TGF)-b1 signaling, a cytokine that dramatically influences T effector cell differentiation. Preliminary results from my laboratory indicate that key TGF-b1 target genes such as SMAD7 are downregulated in Tfh cells, findings consistent with the idea that CD109 is also negatively regulating this signaling pathway in T cells. In addition, CD109 has been been shown to regulate STAT3, a transcription factor that promotes Tfh cell differentiation as well as other T effector subsets. Thus, an in-depth analysis of CD109 in T cell biology and its potential relationship to TGF-b1 and STAT3-dependent signaling in lymphocytes is warranted. In this application, we propose a research program to elucidate the function of CD109 in T cell activation and its specificity in controlling T cell differentiation and function by pursuing 3 specific objectives: 1. Identify the requirements for CD109 expression by CD4+ T cells. 2. Determine how CD109 impacts CD4+ T cell activation and differentiation. 3. Identify CD109 binding partners in activated CD4+ T cells. Understanding the function of CD109 in T cell differentiation and/or function will provide new insight into the molecular mechanisms controlling this important immune cell population.