MACROPHAGE GENE TRANSCRIPTION IN MUCOSAL IMMUNITY

IL-12是一种异二聚体细胞因子，由巨噬细胞和树突状细胞产生，具有多种作用，包括诱导和维持T辅助1 （Th1）反应（1,2）。IL-12 p40基因在产生生物活性IL-12的细胞中表达，并被细菌高度诱导，在体内刺激Th1反应（6,7）。IL-12在慢性粘膜炎症(3)和其他慢性炎症性疾病（4,5）的发病机制中发挥了重要作用。在th1介导的粘膜炎症小鼠模型中，炎症反应可由肠道微生物或微生物产物触发并延续（18,21）。因此，了解导致IL-12基因表达的分子事件将为了解抗原呈递细胞-细菌相互作用如何影响T细胞免疫反应提供重要的见解。通过对il - 12p40启动子的广泛分析，已经确定了一个位于转录起始位点-96至-88的C/EBP蛋白结合位点，该位点对于细菌激活基因表达至关重要(8)。我们最近在C/EBP位点的下游-79到-74处发现了一个AP-1位点，它与C/EBP元件密切相互作用。本研究将重点关注IL-12 p40启动子的这个小而关键的区域。了解C/EBP和AP-1家族成员激活该启动子将揭示巨噬细胞调节炎症反应的一般机制。巨噬细胞产生的大多数其他重要炎症基因的表达，包括tnf - α、il -1 β和IL-8，似乎也受到类似机制的调节。因此，深入分析IL-12基因调控将有助于对宿主-细菌相互作用、巨噬细胞活化和巨噬细胞特异性基因表达有一个大致的了解。这一系列的实验可能最终阐明新的分子靶点来改变体内IL-12的产生。该项目将描述il - 12p40启动子-96至-72这个小而关键的区域的功能dna -蛋白质相互作用。

IL-12 is a heterodimeric cytokine produced by macrophages and dendritic cells with pleiotropic effects that include the induction and maintenance of T helper 1 (Th1) responses (1,2). The IL-12 p40 gene is expressed in cells that make bioactive IL-12 and is highly inducible by bacteria that in vivo stimulate Th1 responses (6,7). A prominent role for IL-12 in the pathogenesis of chronic mucosal inflammation (3) and other chronic inflammatory disorders (4,5) has been established. In murine models of Th1-mediated mucosal inflammation, the inflammatory response can be triggered and perpetuated by enteric microbes or microbial products (18,21). Therefore, understanding the molecular events that lead to IL-12 gene expression will provide important insight into how antigen presenting cell-bacterial interactions influence T cell immune responses. Through an extensive analysis of the IL-12 p40 promoter, a C/EBP protein binding site at -96 to -88 with respect to the transcription start site has been identified that is critical for activation of gene expression by bacteria (8). We have recently identified an AP-1 site immediately downstream of the C/EBP site at -79 to -74 that interacts closely with the C/EBP element. This proposal will focus on this small but critical region of the IL-12 p40 promoter. Understanding activation of this promoter by C/EBP and AP-1 family members will uncover general mechanisms of regulation of the inflammatory response by macrophages. The expression of most other important inflammatory genes produced by macrophages including TNF-alpha, IL-1beta, and IL-8, appear to be regulated by similar mechanisms. Therefore, in depth analysis of IL-12 gene regulation will lead to a general understanding of host-bacterial interactions, macrophage activation, and macrophage specific gene expression. This series of experiments may ultimately elucidate novel molecular targets to alter IL-12 production in vivo. This project will describe functional DNA-protein interactions in a small but critical region, -96 to -72, of the IL-12 p40 promoter.