Fig. 2

TLRs signaling. TIR domain-containing adaptors and TLR signaling. MyD88 is an essential TIR domain-containing adaptor for the induction of inflammatory cytokines via all the TLRs. Upon stimulation, MyD88 recruits IL-1 receptor-associated kinase (IRAK) to TLRs. IRAK is activated by phosphorylation and then dimerizes with TRAF6, leading to the activation of two distinct signaling pathways, finally activating MAPK and NF-kB to elicit proinflammatory cytokines. TIRAP/Mal is a second TIR domain-containing adaptor that specifically mediates the MyD88-dependent pathway via TLR2 and TLR4, While TRIF specifically participates in the MyD88-independent pathway mediated by TLR3 and TLR4, TLR2 leads to the complexity of signal pathway by forming tlr2-tlr1 and tlr2-tlr6 heterodimers and starts intracellular signal transduction. Both homodimers (TLR10/TLR10) and heterodimers (TLR10/TLR2) can recruit MyD88. TLR10 can reduce the production of IL-1β by directly inhibiting MyD88 or MAPK. Although several studies have suggested its inflammatory properties, TLR10 has also been shown to increase the production of IL-1Ra (an anti-inflammatory factor), but the underlying mechanism is still unclear, as indicated by question marks. Nucleic acids in endolysosomes activate TLR3, TLR7 or TLR9 and initiate different and overlapping signal cascades