TLR1TLR10

TLR1TLR10 refers to the Toll-like receptor family members TLR1 through TLR10, a class of pattern recognition receptors that form a core component of the innate immune system in humans and other vertebrates. These receptors are type I transmembrane proteins with extracellular leucine-rich repeat domains that recognize conserved microbial components and an intracellular Toll/IL-1 receptor (TIR) domain that initiates signaling.

Upon recognition of ligands, most TLRs signal through the adaptor protein MyD88, leading to activation of NF-κB and production of pro-inflammatory cytokines, while TLR3 signals via TRIF, and TLR4 can utilize both MyD88 and TRIF pathways. This signaling bridges innate sensing to adaptive immunity by upregulating co-stimulatory molecules and promoting type I interferon responses.

Ligand recognition and localization vary among TLRs. TLR1 forms heterodimers with TLR2 to detect triacyl lipopeptides; TLR2 also pairs with TLR6 for diacyl lipopeptides. TLR4 detects lipopolysaccharide with the help of MD-2 and CD14. TLR5 recognizes flagellin. TLR3, TLR7, TLR8, and TLR9 sense nucleic acid motifs in endosomes (dsRNA, ssRNA, CpG DNA). TLR10’s ligand and precise signaling are less well defined, though it may modulate responses via interactions with other TLRs.

Clinical significance includes the use of TLR agonists as vaccine adjuvants and immunotherapies, and exploration of TLR antagonists for autoimmune or inflammatory conditions. Evolutionarily, the TLR1–TLR10 family represents a conserved vertebrate gene set with species-specific variations that shape innate immune recognition.