Pathogen recognition with Toll-like receptors.

The innate immune system is an evolutionarily conserved system of defense against microbial infections. The family of Toll-like receptors is a major class of receptors that sense molecular patterns associated with a broad range of pathogens including bacteria, viruses, fungi and protozoa. Following pathogen recognition, Toll-like receptors initiate intracellular signal transduction that results in the expression of genes involved in inflammation, antiviral responses and maturation of dendritic cells. Individual Toll-like receptors activate common and unique transcription factors through different signaling pathways to drive specific biological responses against microorganisms.