Toll-Like Receptors in Natural Killer Cells and Their Application for Immunotherapy

Figure 1

PAMP recognition by TLRs and adaptor proteins to mediate cellular signaling pathways. TLR members can be divided into cell surface types (TLR1, 2, 4, 5, and 6) and endosome types (TLR3, 7, 8, and 9). TLRs form homo- or heterodimer and have their respective ligands to be activated. After ligand binding to TLRs, TLRs dimerize and undergo the conformational change to recruit downstream adaptor proteins including myeloid differentiation primary response gene 88 (MyD88), TIR domain-containing adaptor protein (TIRAP)/MyD88-adaptor-like (Mal), TIR domain-containing adaptor inducing IFN-β (TRIF)/TIR domain-containing adaptor molecule-1 (TICAM-1), and TRIF-related adaptor molecule (TRAM).