Toll-like receptor signaling pathway

Specific families of pattern recognition receptors are responsible for detecting microbial pathogens and generating innate immune responses. Toll-like receptors (TLRs) are membrane-bound receptors identified as homologs of Toll in Drosophila. Mammalian TLRs are expressed on innate immune cells, such as macrophages and dendritic cells, and respond to the membrane components of Gram-positive or Gram-negative bacteria. Pathogen recognition by TLRs provokes rapid activation of innate immunity by inducing production of proinflammatory cytokines and upregulation of costimulatory molecules. TLR signaling pathways are separated into two groups: a MyD88-dependent pathway that leads to the production of proinflammatory cytokines with quick activation of NF-{kappa}B and MAPK, and a MyD88-independent pathway associated with the induction of IFN-beta and IFN-inducible genes, and maturation of dendritic cells with slow activation of NF-{kappa}B and MAPK. Source: [http://www.genome.jp/kegg-bin/highlight_pathway?scale=1.0&map=map04620&keyword=toll-like KEGG:Toll-like Receptor Signaling]

特定家族的模式识别受体负责检测微生物病原体并引发先天免疫反应。Toll样受体（TLRs）是一种膜结合受体，被鉴定为果蝇中Toll的同源物。哺乳动物的TLRs表达于先天免疫细胞，如巨噬细胞和树突状细胞，并响应革兰氏阳性或革兰氏阴性细菌的细胞膜成分。TLRs对病原体的识别可激发先天免疫的快速激活，通过诱导促炎细胞因子的产生和共刺激分子的上调。TLR信号通路分为两组：一组为依赖于MyD88的通路，该通路导致产生促炎细胞因子，并迅速激活NF-κB和MAPK；另一组为不依赖于MyD88的通路，与IFN-β和IFN诱导基因的诱导以及树突状细胞的成熟相关，该通路通过缓慢激活NF-κB和MAPK。资料来源：[http://www.genome.jp/kegg-bin/highlight_pathway?scale=1.0&map=map04620&keyword=toll-like KEGG:Toll-like Receptor Signaling]