Current Views of Toll-Like Receptor Signaling Pathways

Figure 2

TLR-mediated MyD88-dependent or TRIF-dependent pathways. TIR domain-containing adaptors MyD88, TIRAP, TRIF, and TRAM define TLR-mediated signaling. MyD88 and TIRAP are adaptors for the MyD88-dependent pathways, which mainly activate proinflammatory cytokine production. On the other hand, TRIF and TRAM are adaptors for IRF3 activation, resulting in production of type I IFN by TLR3- or TLR4-mediated TRIF-dependent pathways. In pDCs, TLR7/TLR9-mediated MyD88-dependent pathways induce IRF7 activation, leading to IFNα production.