Table 1. Different subtypes of TLRs and their identified PAMPs.

TLRs	PAMPs	Biological activity	Reference
TLR2/TLR6 TLR2/TLR1	The lipoproteins of bacteria or mycoplasma. Lipopeptide (MALP-2), Peptidogl, ycan (PGN)	Activate intracellular signal NF-KB, induce adhesion molecules and inflammatory cytokines.	Zhu et al. (2010), Basto & Leitao (2014), Kaisho & Akira (2002)
TLR4	Lipopolysaccharides(LPS), Heat shock protein (HSP), β-defensin, Heparin-binding hemagglutinin(HBHA)	Induce the expression of adhesion molecules and inflammatory cytokines.	Reed et al. (2016), Kaisho & Akira (2002)
TLR5	Gram-negative bacteria flagellin	The potent proinflammatory activity by inducing NF-KB activation, and expression of IL-8 and inducible NO synthase in intestinal epithelial cells.	Kaisho & Akira (2002), Moyle (2017)
TLR3	Double-stranded RNA (ds RNA), Poly(I:C)	Induce IL-12 production and DC maturation and elevate CD40 expression on APCs.	Kaisho & Akira (2002), Cheng et al. (2018)
TLR7/TLR8	Single-stranded RNA (ssRNA)	Induce the expression of adhesion molecules and inflammatory cytokines	Vasilakos & Tomai (2013)
TLR9	CpG DNA, Hemozoin, Herpes simplex virus DNA	Production of Th1 cytokines and promotion of cytotoxic activity of NK cells.	Zhu et al. (2010), Kaisho & Akira (2002)

Note:

The biological activities of TLRs agonists that can activate the immune system.