Endosomal Toll-like receptor (TLR (when referring collectively; see aliases for individual numbers))

Endosomal Toll-like receptors (TLRs 3, 7, 8, and 9) are **pattern recognition receptors** that reside in the membranes of endosomes and lysosomes in immune cells, notably dendritic cells and macrophages[1][3][5][6]. They detect nucleic acids from pathogens such as viruses or bacteria that have been internalized by endocytosis, as well as some endogenous molecules in disease states[6][3]. Each receptor has specificity: - **TLR3**: recognizes double-stranded RNA (dsRNA)[6][7] - **TLR7 and TLR8**: recognizes single-stranded RNA (ssRNA)[1][6][7] - **TLR9**: recognizes unmethylated CpG DNA motifs, common in bacterial and viral genomes[1][6][7] Ligand binding results in receptor dimerization and recruitment of adaptor proteins (e.g., MyD88, TRIF), leading to activation of downstream signaling pathways such as NF-κB and IRFs, culminating in inflammatory cytokine and type I IFN production[4][7]. Tight control of endosomal TLR trafficking is essential to prevent recognition of self-nucleic acids and autoimmunity[3][2][5]. Their unique localization enables a central role in **antiviral immunity, modulation of inflammation, and autoimmunity**, making them attractive but challenging drug targets. **Note:** For structured data or drug targeting, use the individual canonical names (e.g., "Toll-like receptor 7") rather than the collective/group term.

Other names

Endosomal Toll-like receptorEndosomal TLRTLR (generic; individual: TLR3, TLR7, TLR8, TLR9)Intracellular Toll-like receptorNucleic acid-sensing TLRs

Agonists: stimulate cytokine/IFN production, enhancing antiviral or antitumor immunity Antagonists: inhibit autoimmune or hyperinflammatory responses by blocking ligand recognition or signaling Endosomal localization: by restricting activation to endosomes/lysosomes, self-nucleic acid sensing is minimized, reducing risk of autoimmunity[3][1][2][5][6].