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. 2020 Oct 20;10:591970. doi: 10.3389/fcimb.2020.591970

Figure 1.

Figure 1

Signaling mediated by the activation of TLR3, 7 and 9. TLRs 3, 7, and 9 are recruited from the endoplasmic reticulum through the UNC93b1 protein to the endosome. In the endosome these receptors will recognize their specific ligands, in which TLR3 recognizes dsRNA, while TLR7 ssRNA, and TLR9 DNA. Then each of these receivers, now activated, will start different signaling pathways. TLR3 recruits TRIF with subsequent activation of TRAF3. TRAF3 can activate two ways, the first IKKε will be activated and induce the activation of IRF3, while the second will occur activation of IKKε/IRAK1 which will result in the activation of IRF7. TLR7 and TLR9 recruit MYD88 which will result in the activation of TRAF6. TRAF6 may induce 3 different signals, the first will occur the activation of IRF7 through Ikka, the second will occur the activation of the IKKs complex that will induce the activation of NF-κB and the last will occur the activation of MAPKs that will mediate the activation of AP−1. IRF3 and IF7 will be transcribed in the nucleus inducing the production of type I IFN, whereas NF- κB and AP-1 will be transcribed and will mediate the production of inflammatory cytokines and chemokines.