Toll-like receptor 2 and Toll-like receptor 4–MD-2 complex (TLR2, TLR4–MD-2)

Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4) are membrane-bound pattern recognition receptors of the innate immune system, critical for detecting microbial components and initiating protective inflammation[2][8]. TLR4 forms a highly stable, functional complex with the accessory protein MD-2 (also called lymphocyte antigen 96 or LY96) on the plasma membrane; this complex binds bacterial lipopolysaccharide (LPS) and mediates downstream activation of NF-κB and interferon pathways, leading to the release of pro-inflammatory cytokines and chemokines[2][5][7]. TLR2 can recognize diverse microbial ligands, sometimes with limited MD-2 association in experimental settings, but does not natively require MD-2 for high-affinity ligand recognition[1][4]. Both receptors trigger intracellular signaling through MyD88- and TRIF-dependent pathways, bridging the innate and adaptive immune responses, and play major roles in pathogen sensing, inflammation, and disease progression[2][5]. TLR4–MD-2 complex is directly targeted by multiple therapeutics (e.g., Eritoran, TAK-242) and novel agonists/antagonists. Dysregulation of TLR4/MD-2 or TLR2 activity is implicated in infectious, inflammatory, autoimmune, and neoplastic diseases[5]. Excessive activation poses safety concerns including risk of cytokine storm and sepsis[2]. Disease associations and drug targeting should always specify the exact receptor complex (TLR2 or TLR4–MD-2) due to distinct structural and functional properties. Note: The submitted target entity "Toll-like receptor 2 and Toll-like receptor 4–MD-2" is problematic: TLR2 and TLR4–MD-2 do not form a physiological single complex. MD-2 is an obligate co-receptor for TLR4, and although it can weakly modulate TLR2 activity in overexpression or reconstitution studies, this is not its canonical biological function[1][4]. For structured databases, treat TLR2 and TLR4–MD-2 as distinct canonical entities. This entry conflates two structurally distinct receptors.

Other names

Toll-like receptor 2 (TLR2)Toll-like receptor 4 (TLR4)TLR4–MD-2 complexCD282 (TLR2)CD284 (TLR4)Myeloid differentiation factor 2 (MD-2, LY96)

Agonists: Activate TLR4/MD-2 or TLR2, triggering MyD88- or TRIF-dependent signaling, leading to cytokine production. Antagonists: Block ligand (LPS, lipid A) binding, preventing receptor dimerization and downstream signaling