Expression and function of the TLRs on T cells

描述(申请人提供)：Toll样受体(TLRs)在先天免疫和获得性免疫中起着不可或缺的作用。TLRs的结扎激活了先天免疫系统的细胞，诱导了吞噬、干扰素-a和干扰素-b的分泌等功能。TLR连接也是先天免疫系统和获得性免疫系统之间的桥梁。TLR对DC和巨噬细胞的刺激可诱导炎性细胞因子的产生，如IL-12，并上调MHCⅡ类分子和共刺激配体如CD40和CD86，其中大多数反应需要通过接头信号分子MyD88传递的信号。虽然TLRs和MyD88在APC上的作用已经确定，但令人惊讶的是，人们对它们在T细胞上的表达和潜在功能知之甚少。我们实验室的研究表明，在初始的CD4+CD25T细胞被激活后，几种TLR被表达。这些TLR的连接通过MyD88激活了几个下游信号通路，包括NF-kB、p38JNK和ERK。从功能上讲，这会增强T细胞的存活率，并提供与次优TCR连接的共刺激作用。新的数据还表明，在T细胞中表达MyD88可能是对弓形虫病原体的保护性免疫反应所必需的。我们的工作假设是T细胞上的TLR和MyD88信号是细胞免疫反应的重要贡献者。为此，本研究计划的长期目标是确定T细胞上TLRs的表达和功能。在特定的目标#1中，我们将描述控制T细胞上TLRs表达和上调的信号，以及TLRs和MyD88用来调节其作用的下游信号通路。具体目的#2将使用TCR转基因小鼠的细胞与体外和体内过继转移系统相结合，详细研究TLR和MyD88激活T细胞在诱导激活和共刺激分子、细胞因子产生或倾斜以及效应/记忆分化和反应性方面的影响。这种方法将允许精确定义TLR对T细胞的刺激能起什么作用。在特定的目标#3中，我们将询问在目标#2中确定的TLRs和MyD88的哪些功能在体内免疫反应中起作用。为了做到这一点，我们将使用MyD88基因敲除小鼠和骨髓嵌合体和过继转移系统来创建只有T细胞缺乏MyD88的体内模型。基于我们的初步数据，我们将使用这些模型来评估对弓形虫的反应，并将MyD88缺陷小鼠回交到TCR转基因背景，使我们能够跟踪单个T细胞在移植模型中对体内同种异体抗原的反应的命运。

DESCRIPTION (provided by applicant): Toll-like receptors (TLRs) play an integral role in innate and adaptive immunity. Ligation of TLRs activates cells of the innate immune system, inducing functions such as phagocytosis and IFN-a and IFN-b secretion. TLR-ligation also serves as a bridge between the innate and adaptive immune systems. TLR stimulation of DCs and macrophages induces the production of inflammatory cytokines such as IL-12, and upregulation of MHC class II and costimulatory ligands such as CD40 and CD86, and most of these responses require signals delivered through the adaptor signaling molecule MyD88. While roles for TLRs and MyD88 on APCs are well-established, surprisingly little is known about their expression and potential function on T cells. Studies from our laboratory show that several TLRs are expressed following activation of naive CD4+CD25 T cells. Ligation of these TLRs activates, via MyD88, several downstream signaling pathways, including NF- kB, p38 JNK, and ERK. Functionally, this leads to enhanced T cell survival and provides costimulation with sub-optimal TCR ligation. New data also indicates that in vivo expression of MyD88 in T cells may be required for a protective immune response to the pathogen Toxoplasma gondii. Our working hypothesis is that TLR and MyD88 signaling on T cells are important contributors to cellular immune responses. To this end, the long-term goals of this research program are to define the expression and function of TLRs on T cells. In specific aim #1 we will characterize the signals which govern the expression and upregulation of TLRs on T cells, and the downstream signaling pathways which TLRs and MyD88 use to mediate their effects. Specific aim #2 will use cells from TCR transgenic mice coupled with in vitro and in vivo adoptive transfer systems to conduct a detailed examination of the effects of TLR and MyD88 activation of T cells on induction of activation and costimulatory molecules, cytokine production or skewing, and effector/memory differentiation and responsiveness. This approach will allow for precise definition of what TLR stimulation of T cells can do. In specific aim #3 we will then ask which of the functions identified for TLRs and MyD88 in aim #2 are operative during in vivo immune responses. To do so, we will use MyD88 knockout mice and bone-marrow chimeras and adoptive transfer systems to create in vivo models in which only T cells are deficient in MyD88. Based on our preliminary data, we will use these models to assess responses to Toxoplasma gondii, and will also backcross the MyD88-deficient mice onto TCR transgenic backgrounds to enable us to track the fate of individual T cells as they respond to alloantigen in vivo in transplantation models.