Lee Myeong Sup, Kim Young-Joon
Department of Biochemistry, Yonsei University, Seoul 120-749, Korea.
Mol Cells. 2007 Feb 28;23(1):1-10.
Invading pathogens are recognized by diverse germline-encoded pattern-recognition receptors (PRRs) which are distributed in three different cellular compartments: extracellular, membrane, and cytoplasmic. In mammals, the major extracellular PRRs such as complements may first encounter the invading pathogens and opsonize them for clearance by phagocytosis which is mediated by membrane-associated phagocytic receptors including complement receptors. The major membrane-associated PRRs, Toll-like receptors, recognize diverse pathogens and generate inflammatory signals to coordinate innate immune responses and shape adaptive immune responses. Furthemore, certain membrane-associated PRRs such as Dectin-1 can mediate phagocytosis and also induce inflammatory response. When these more forefront detection systems are avoided by the pathogens, cytoplasmic PRRs may play major roles. Cytoplasmic caspase-recruiting domain (CARD) helicases such as retinoic acid-inducible protein I (RIG-I)melanoma differentiation-associated gene 5 (MDA5), mediate antiviral immunity by inducing the production of type I interferons. Certain members of nucleotide-binding oligomerization domain (NOD)-like receptors such as NALP3 present in the cytosol form inflammasomes to induce inflammatory responses upon ligand recognition. Thus, diverse families of PRRs coordinately mediate immune responses against diverse types of pathogens.
入侵的病原体可被多种种系编码的模式识别受体（PRR）识别，这些受体分布在三个不同的细胞区室中：细胞外、细胞膜和细胞质。在哺乳动物中，主要的细胞外PRR如补体可能首先遇到入侵的病原体，并将它们调理以便通过吞噬作用清除，吞噬作用由包括补体受体在内的膜相关吞噬受体介导。主要的膜相关PRR，即Toll样受体，识别多种病原体并产生炎症信号，以协调先天免疫反应并塑造适应性免疫反应。此外，某些膜相关PRR如Dectin-1可介导吞噬作用并诱导炎症反应。当病原体避开这些更前沿的检测系统时，细胞质PRR可能发挥主要作用。细胞质半胱天冬酶招募结构域（CARD）解旋酶如视黄酸诱导蛋白I（RIG-I）、黑色素瘤分化相关基因5（MDA5），通过诱导I型干扰素的产生来介导抗病毒免疫。某些核苷酸结合寡聚化结构域（NOD）样受体家族成员，如存在于胞质溶胶中的NALP3，形成炎性小体以在识别配体后诱导炎症反应。因此，不同家族的PRR协同介导针对不同类型病原体 的免疫反应。
