Toll signaling pathways in the innate immune response

The Toll signaling pathway, which is required for the establishment of the dorsal-ventral axis in Drosophila embryos, plays an important role in the r esponse of larval and adult Drosophila to microbial infections. Recent gene tic evidence has shown that a mammalian Toll-like receptor, mouse Tlr4, is the signal transducing receptor activated by bacterial lipopolysaccharide. Thus, Toll-like receptors appear to detect a variety of microbial component s and to trigger a defensive reaction in both Drosophila and mammals. Genet ic data from both Drosophila and mice have defined components required for activation of Toll-like receptors and for the downstream pathways activated by the Toll-like receptors.