Toll-like receptor (TLR) (TLR)

Toll-like receptors (TLRs) are a critical family of pattern recognition receptors (PRRs) primarily expressed on sentinel immune cells such as macrophages, dendritic cells, and neutrophils [1]. They function by detecting conserved molecular structures known as pathogen-associated molecular patterns (PAMPs) from bacteria, viruses, and fungi, as well as endogenous danger-associated molecular patterns (DAMPs) released during tissue damage [2]. Upon ligand binding, TLRs dimerize and recruit adapter proteins like MyD88 or TRIF, triggering intracellular signaling pathways that culminate in the activation of transcription factors such as NF-κB and IRFs [3]. This process leads to the robust production of pro-inflammatory cytokines, chemokines, and type I interferons, which are essential for initiating innate immunity and shaping the subsequent adaptive immune response [4]. In the pharmaceutical industry, TLRs are major therapeutic targets; agonists are utilized as potent vaccine adjuvants and in oncology to enhance anti-tumor immune surveillance, whereas antagonists are under development to mitigate hyper-inflammatory states like sepsis and chronic autoimmune diseases [5]. However, the clinical application of TLR modulators is often limited by the risk of systemic inflammatory toxicity, necessitating precise delivery and dosing strategies [6].

Other names

TLRsPattern recognition receptorPRRToll-like receptor family

TLR agonists bind to the extracellular or endosomal domains of the receptor, inducing dimerization and recruitment of adapter proteins like MyD88 or TRIF, which activates NF-κB and IRF signaling pathways to produce pro-inflammatory cytokines and interferons [3, 5]. TLR antagonists bind to the receptor to competitively inhibit ligand binding or prevent dimerization, thereby suppressing excessive inflammatory signaling [5].