Modulation of Toll-Like Receptor Activity by Leukocyte Ig-Like Receptors and Their Effects during Bacterial Infection

Figure 1

TLR signalling pathways: All TLRs except TLR3 share a common initial signalling pathway through MyD88 to the IRAK1/2/4TRAF6 complex. TLR3 uses TRIF to activate the IRAK1/2/4TRAF6 complex. From here, TLR1–6 are able to signal via MAPK and NEMO to activate API and NF-$\kappa \text{B}$, respectively, and promote transcription of proinflammatory cytokines. TLR8 also follows the same pattern but is only able to signal via NEMO, not MAPK. TLR7/9 are also able to activate NEMO and additionally IKK-$\alpha$ to promote IFN-$\alpha$ production. In addition to the MAPK and NEMO pathways, TLR3 is also able to signal via TRAF3 to promote IFN-$\beta$ production [25–27].