Table 1.

The summary of toll-like receptors.

TLR	Cellular expression	Receptor complex	Natural Ligands	Synthetic Agonists	Signaling adaptor	Downstream effects
TLR2	Plasma membrane	2–1 2–6 2–10	Lipopeptides Peptidoglycan Lipoteichoic acid Zymosan Lipoarabinomannans	Pam2Cys Pam3Cys	MyD88	inflammatory cytokines (TNFα, IL-1β, IL-6, IL-8, IL-10, IL-12) CD80, CD86 upregulation
TLR3	Endolysosome	3–3	dsRNA	PolyI:C PolyIC12U PolyICLC ARNAX RGC100	TRIF	IFNβ CXCL10 CD80, CD86 upregulation
TLR4	Plasma membrane	4-MD2	LPS	MPLA GLA ONO-4007	MyD88 TRIF	inflammatory cytokines (TNFα,IL-1β,IL-6) IFNβ CXCL10 CD80, CD86 upregulation
TLR5	Plasma membrane	5–5	Bacterial flagellin	Flagellin	MyD88	inflammatory cytokines (TNFα,IL-1β,IL-6,IL-8) CD80, CD86 upregulation
TLR7	Endolysosome	7–7	ssRNA	Resiquimod Imiquimod Vesatolimod	MyD88	Type 1 IFN CD80, CD86 upregulation
TLR8	Endolysosome	8–8	ssRNA	Resiquimod Selgantolimod Motolimod	MyD88	inflammatory cytokines (TNFα, IL-1β, IL-6, IL-8, IL-10, IL-12) CD80, CD86 upregulation
TLR9	Endolysosome	9–9	CpG-DNA	ODN-2216(Class A) ODN-2006(Class B) ODN-2429(Class C) ODN-21798(Class P) IMO-2025 IMO-2125 MGN-1703	MyD88	Type 1 IFN CD80, CD86 upregulation
TLR10	Plasma membrane	10–1 10–2 10–6 10–10	Triacylated lipopeptides	N/A	Unknown	IL-1Ra
TLR11	Endolysosome	11–11 11–12	Profilin Flagellin	N/A	MyD88	IL-12
TLR12	Endolysosome	12–11 12–12	Profilin	N/A	MyD88	IL-12
TLR13	Endolysosome	13–13	Bacterial 23S rRNA	ORN Sa19	MyD88	IL-12