中文摘要：

CpG DNA是指含有胞嘧啶一乌嘌呤模体的未甲基化DNA片段，常存在于细菌、病毒等的基因组以及质粒DNA中，也可通过人工合成。它具有高效的免疫刺激活性，当微生物感染时，CpG DNA的释放向机体免疫系统提供了一种“危险信号”，触发机体保护性免疫应答以清除外来病原体。CpG DNA激活的细胞信号机制包括CpGDNA的内吞，与Toll样受体9（Toll—likere—ceptor9，TLR9）特异性识别及其一系列信号级联反应，从而诱导靶基因的表达，并受到各种内源性因素的反馈调节。现对CpG DNA所激活的受体分子、与TLR9介导的信号转导与调节以及不同类型CpG DNA激活的分子机制等作一综述。

英文摘要：

CpG DNA containing unmethylated CpG dinucleotides in particular base contexts （CpG motifs） have characteristic immunostimulatory effects. The release of unmethylated CpG DNA during infection provides a ＇dangerous signal＇ to the innate immune system, triggering a protective immune response that enhances the ability of the host to eliminate the pathogen. The signal transduction activated by CpG DNA includes the cellular internalization of CpG DNA, the interaction with Toll-like receptor 9 （TLR9） and the subsequent signal cascade reaction. The intensity and duration of CpG DNA/TLR9 signaling can be negatively modulated by intracellular regulators, transmembrane proteins regulators and the reduction of TLR9 expression. In addition, three structurally distinct classes of CpG ODNs representing differential immunomodulatory activities are capable of stimulating cells through differential signaling. Above all, the study of the signaling mechanism of CpG DNA may provide a deep understanding toward CpG-mediated immune response.