Toll-like receptor 2, Toll-like receptor 4, Toll-like receptor 7, Toll-like receptor 9 (TLR2, TLR4, TLR7, TLR9)

Toll-like receptors are a family of pattern-recognition, single-pass membrane receptors critical to innate immune defense. TLR2 and TLR4 are located on the cell surface and primarily detect bacterial components (e.g., lipoproteins for TLR2, lipopolysaccharide for TLR4), triggering inflammatory responses via NF-κB and cytokine pathways. TLR7 and TLR9 are found in intracellular endosomal compartments, where they sense viral RNA (TLR7) or unmethylated CpG DNA (TLR9). Stimulation of these receptors activates pathways leading to the production of pro-inflammatory cytokines and type I interferons, driving cellular activation, pathogen clearance, and shaping adaptive immune responses. Dysregulation of TLR activity contributes to a spectrum of human diseases, including infection, chronic inflammation, atherosclerosis, cancer, and autoimmunity. Multiple TLR agonists and antagonists are under development or clinical investigation for cancer immunotherapy, infectious disease vaccines, and immune modulation.

Other names

CD282CD284Toll-like receptor familyTLR family

Agonists enhance immune response by stimulating cytokine/chemokine production via receptor activation. Antagonists inhibit excessive inflammation (e.g., in sepsis) by blocking receptor signaling (notably TLR4). Vaccine adjuvants use agonists to drive Th1 and/or cytotoxic immune responses via IFN/cytokine induction (TLR4, TLR7, TLR9).