ROLES OF TOLL LIKE RECEPTORS IN INNATE IMMUNITY

最近发现的果蝇Toll受体蛋白在哺乳动物中的同源物引起了人们对确定这些蛋白在先天性免疫中的作用的兴趣。果蝇相关蛋白Toll和18-Wheeler是果蝇抗真菌和抗细菌反应所必需的。人类基因组至少编码10个不同的Toll样受体(TLR)蛋白基因，尽管它们在体内的功能在很大程度上尚不清楚。已经提出巨噬细胞可能利用TLR蛋白作为其对细菌病原体的反应的一部分。在小鼠中，单个TLR基因的突变导致对革兰氏阴性细菌脂多糖(LPS)失去反应性，并增加对细菌感染的易感性。我们和其他人最近表征了整个细菌和几个纯化的细菌细胞壁成分对巨噬细胞TLR依赖的激活。这些研究表明，不同的细菌产物通过不同的TLR蛋白激活细胞，并需要CD14，CD14是一种内毒素受体，也能结合各种细菌细胞壁成分。与这些许多细菌不同，结核分枝杆菌依赖TLR激活细胞不需要CD14。分枝杆菌配体负责通过不同的TLR依赖的途径激活细胞，已经被确定，但还没有被生化表征。该项目的长期目标是表征TLR依赖的信号，并确定这些信号在诱导巨噬细胞天然免疫反应中所起的作用。本研究的目的是：(1)确定不同TLR蛋白的结合是否激活共同的和不同的信号转导通路；(2)确定不同的TLR蛋白的参与是否激活巨噬细胞中不同的功能反应；(3)确定TLR功能的选择性丧失是否会导致先天免疫的改变。

The recent discovery of mammalian homologues of the Drosophila Toll receptor protein has elicited interest in defining the role of these proteins in innate immunity. The related Drosophila proteins Toll and 18-Wheeler are required for ani-fungal and anti-bacterial responses in the fly. The human genome encodes at least 10 distinct Toll-like receptor (TLR) protein genes, although their functions in vivo are largely unknown. It has been proposed that macrophages are likely to utilize TLR proteins as part of their responses against bacterial pathogens. In mice, the mutation in a single TLR gene results in a loss of responsiveness to Gram-negative bacterial lipopolysaccharide (LPS), and increased susceptibility to bacterial infection. We, and others, have recently characterized the TLR-dependent activation of macrophages by whole bacteria and several purified bacterial cell wall components. These studies have shown that distinct bacterial products activate cells via different TLR proteins and require CD14, an LPS receptor that also binds a variety of bacterial cell wall components. Unlike these many bacteria, TLR-dependent activation of cells by Mycobacterium tuberculosis bacilli does not require CD14. Mycobacterial ligands responsible for cellular activation by distinct TLR- dependent pathways have been identified, but have not been biochemically characterized. The long-term objectives of this project are to characterize TLR-dependent signaling, and to define the roles that these signals play in eliciting innate immune responses in macrophages. The aims of this proposal are to (1) determine whether engagement of different TLR proteins activates both shared and distinct signal transduction pathways, (2) determine if engagement of different TLR proteins activates distinct functional responses in macrophages, and (3) determine if selective loss of TLR function results in altered innate immunity.