Medical Definition of Toll-like receptor 4
Toll-like receptor 4: TLR4. One in a family of receptors that provide critical links between immune stimulants produced by microorganisms and the initiation of host defenses. Abbreviated TLR4.
TLR4 is a transmembrane lipopolysaccharide receptor. Activation of it causes the release of antimicrobial peptides, inflammatory cytokines and chemokines, and costimulatory molecules that initiate the innate immune response to common gram-negative bacteria. TLR4 also interacts with respiratory syncytial virus, heat-shock proteins, fibronectin, fibrinogen, and hyaluronic acid.
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