Structure and function of Toll-like receptor proteins

Life Sci. 2000 Dec 8;68(3):241-58. doi: 10.1016/s0024-3205(00)00939-5.


Beginning in 1997 with the identification of the first human homologue of the Drosophila protein Toll, a family of related molecules have been identified in both humans and other mammals. These Toll-like receptor (TLR) proteins appear to represent a conserved family of innate immune recognition receptors. TLR proteins share extended homology with receptors for the cytokines interleukin 1 (IL-1) and interleukin 18 (IL-18). These receptors are coupled to a signaling pathway that is conserved in mammals, insects, and plants, resulting in cellular activation, thereby stimulating innate immune defenses. A variety of bacterial and fungal products have been identified that serve as TLR ligands, and more recent studies have identified the first endogenous protein ligands for TLR proteins. While TLR signaling is likely to be a key feature of innate immune responses, these proteins may also regulate homeostasis via interaction with endogenous protein ligands.

Publication types

  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Drosophila
  • Drosophila Proteins*
  • Humans
  • Interleukin-18 Receptor alpha Subunit
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / physiology*
  • Mice
  • Molecular Sequence Data
  • Receptors, Cell Surface / chemistry*
  • Receptors, Cell Surface / physiology*
  • Receptors, Interleukin / chemistry
  • Receptors, Interleukin / physiology
  • Receptors, Interleukin-1 / chemistry
  • Receptors, Interleukin-1 / physiology
  • Receptors, Interleukin-18
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Toll-Like Receptor 5
  • Toll-Like Receptors


  • Drosophila Proteins
  • IL18R1 protein, human
  • Il18r1 protein, mouse
  • Interleukin-18 Receptor alpha Subunit
  • Membrane Glycoproteins
  • Receptors, Cell Surface
  • Receptors, Interleukin
  • Receptors, Interleukin-1
  • Receptors, Interleukin-18
  • Toll-Like Receptor 5
  • Toll-Like Receptors
  • tehao protein, Drosophila