Toll-like receptors 2, 3, and 4 (TLR2, TLR3, TLR4)

Toll-like receptors 2, 3, and 4 are closely related type I transmembrane proteins of the innate immune system. They function as pattern recognition receptors (PRRs) that detect conserved microbial structures and trigger intracellular signaling pathways, resulting in cytokine production and inflammation. TLR2 primarily recognizes bacterial lipoproteins and peptidoglycans, often forming heterodimers with TLR1 or TLR6 for ligand specificity [3][5]. TLR3 is an endosomal receptor specializing in the detection of viral double-stranded RNA, inducing antiviral responses via type I interferons [1][7]. TLR4 is best known for its role in recognizing bacterial lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, and requires MD-2 as an accessory protein for ligand binding and activation [2][4][6]. These receptors are critical mediators of the innate immune response and bridge innate and adaptive immunity. Dysregulation or aberrant activation of TLR2/3/4 contributes to infectious, inflammatory, and neoplastic diseases, making them important therapeutic targets and biomarkers in clinical research [1][2][3][4][7][8].

Other names

TLR2CD282TLR3TLR4

Agonists stimulate innate immunity by mimicking pathogen-associated molecular patterns (PAMPs). Antagonists inhibit excessive immune activation (e.g., during sepsis or in autoimmune conditions). Modulation of receptor dimerization (e.g., heterodimer formation for TLR2 with TLR1 or TLR6 is required for activation).