Toll-Like Receptors: Bridging Innate and Adaptive Responses

Introduction of Toll-Like Receptors
TLR4 Antibody Inhibits LPS Effects
Human & Mouse Toll-Like Receptors Product Table

Introduction of Toll-Like Receptors

Members of the Toll-like receptor (TLR) family are responsible for the recognition of pathogen-associated molecular patterns (PAMPs) expressed by a wide spectrum of infectious agents. To date, over thirteen TLRs have been reported in human and mouse. TLRs activate the NF-κB pathway, which regulates cytokine expression, through several adaptor molecules including MyD88, TIRAP/Mal and TRIF. Activation of the NF-κB pathway links innate and adaptive immune response by production of inflammatory cytokines such as IL-1, IL-6, IL-8, TNF-α, IL-12, chemokines and induction of costimulatory molecules such as CD80, CD86, and CD40. In addition to induction of the cytokine network, MyD88 binds FADD and triggers apoptosis through the Caspase cascade. Hence, activation of the apoptosis pathway via TLRs appears to contribute to the repertoire of defense mechanisms utilized by the innate immune response.

Constitutive expression (albeit at very low levels with some family members) of human TLR1, 2, 4 and mouse TLR4/MD2 and TLR2 on the surface of myeloid lineage cells has been confirmed with specific mAbs. Activation-induced upregulation of TLR2 and 4 on other cell types such as endothelial cells, epithelial cells, and others have also been reported in the literature. TLR3, 7, 8 and 9 are localized mainly in endosomal/lysosomal compartments. Human TLR3 is detected in human fibroblast cell lines and TLR9 in in vitro-derived DCs. Specific antibodies to other members of human and mouse TLRs are used to correlate and confirm the expression of these molecules at the protein and mRNA levels.

Evidence implicates the involvement of the TLR family in a spectrum of systemic disorders following bacterial infections including sepsis, cardiac ischemia, peridontitis, and cerebral palsy. The rapid pace of research in the TLR family shall elucidate their functions and potential therapeutic interventions.

Mouse TLR2 Data

Expression of mouse TLR2 on the surface of CD11b (Mac1)+ splenic cells.
Mouse spleen cells were simultaneously stained with anti-CD11b-APC and
anti-TLR2-FITC. Viable cells were gated for analysis. Plot above shows
staining of a subset of CD11b+ cells that express TLR2 (purple population).

TLR4 Antibody Inhibits LPS Effects

TLR4 is a pattern recognition receptor and signaling molecule, responding to bacterial lipoproteins, which has been implicated in innate immunity and inflammation. TLR4 physically associates with another molecule called MD-2, and together with CD14, this complex is responsible for LPS recognition and signaling. TLR4 is expressed by peripheral blood monocytes. Most TLR cell surface expression, especially TLR1 and TLR4, occurs at low levels on monocytes and at even lower levels on other cell types including granulocytes and immature dendritic cells (iDC). While the exact mechanism is not clearly defined at the present time, antibodies to TLR4 have been reported to inhibit the LPS-induced cytokine production by human PBMCs and mouse peritoneal macrophages.

2x10⁶ ml human PBMCs were treated with 10ng/ml LPS for 24 hours. Cells in
the anti-TLR4 treated sample were preincubated with 20µg/ml HTA 125 (FG)
for one hour prior to addition of LPS. TNF-α secretion was measured using
human TNF-α Ready-SET-Go! ELISA set.

Human & Mouse Toll-Like Receptors Product Table

Table 1: Human Toll-Like Receptors
Human Toll-Like Receptors
Human	Clone	Applications	Catalog SKU	Format
TLR1	GD2.F4	FC, IHC	9911	Purified, FG Purified, PE
TLR2	Polyclonal	WB	9028	Polyclonal Serum
	T2.5	FC, BA, IHC, IP	9024	Purified, FG Purified, Biotin, PE, PE-Cy7, Alexa Fluor^® 488, Alexa Fluor^® 647
	TL2.3	FC, IHC/F	9029	Purified
	TL2.1	FC, BA, IHC/F, IP, WB	9922	Purified, FG Purified, Biotin, FITC, PE, APC, Alexa Fluor^® 488, Alexa Fluor^® 647, Alexa Fluor^® 700
TLR3	TLR3.7	FC, BA, IP	9039	Purified, FG Purified, Biotin, PE
TLR4	Polyclonal	WB	9048	Polyclonal Serum
	Polyclonal	WB	9920	Purified
	HTA125	FC, BA, IP	9917	Purified, FG Purified, Biotin, PE, PE-Cy5, PE-Cy7, APC, Alexa Fluor^® 488, Alexa Fluor^® 647, Alexa Fluor^® 700, Pacific Blue^®
TLR6	hPer6	FC, WB	9069	Purified, Biotin
TLR7	Polyclonal	WB	9079	Purified
TLR8	Polyclonal	WB	9089	Purified
TLR9	eB72-1665	ICFC, IP, WB	9099	Purified, PE
*Alexa Fluor^® and Pacific Blue^® are registered trademarks of and licensed under patents assigned to Molecular Probes, Inc. for research use only.

Table 2: Mouse Toll-Like Receptors
Mouse Toll-Like Receptors
Mouse	Clone	Applications	Catalog SKU	Format
TLR1	eBioTR23	FC, IP	9011	Purified, Biotin, Alexa Fluor^® 647
	eBioLD5	WB	9012	Purified
TLR2	6C2	FC, NU, IP	9021	Purified, FG Purified, Biotin, FITC, PE, APC
	mT2.7	FC,IHC/F, IP	9022	Purified, Biotin, FITC, PE
	T2.5	FC, BA, IHC, IP	9024	Purified, FG Purified, Biotin, PE, PE-Cy7, Alexa Fluor^® 488, Alexa Fluor^® 647
TLR3	Polyclonal	WB, FC	9031	Serum
	T3.7C3	WB	9032	Purified
TLR4	Polyclonal	WB	9004	Serum
	eBioMT439	WB	9042	Purified
	UT41 (TLR4 & TLR4/MD-2)	FC	9041	Purified, Biotin, PE, Alexa Fluor^® 488
	UT12 (TLR4/MD-2, activating)	FC, BA, IP, NU	9925	Purified, FG Purified
	MTS510 (TLR4/MD-2, blocking)	FC, BA, NU, IP	9924	Purified, FG Purified, Biotin, PE, PE-Cy7
	UT18 (TLR4/MD-2, activating)	FC, BA, IP, NU	9926	Purified, FG Purified
TLR7	Polyclonal	WB	9079	Purified
TLR8	Polyclonal	WB	9089	Purified
TLR9	Polyclonal	WB, FC	9092	Purified
	M9.D6	ICFC, WB	9093	Purified, Biotin, FITC
TLR11	Polyclonal	WB	9119	Purified
*Alexa Fluor^® and Pacific Blue^® are registered trademarks of and licensed under patents assigned to Molecular Probes, Inc. for research use only.