Fig. 1.

Diagram of major TLR pathways. Upon ligand binding and receptor dimerization, TLRs interact with a TIR domain-containing adaptor protein. (Left) Canonically, TLR signal transduction occurs through the MYD88-dependent pathway. (Right) In some cases, such as with TLR3 and TLR4, TLRs require other TIR domain-containing adaptors to signal successfully for cytokine expression. SARM1, a TIR domain-containing negative regulator for TCAM1-dependent signaling pathways, is not shown. Red ellipses denote conserved TIR domains.