MyD88 as a bottle neck in Toll/IL-1 signaling.

Myeloid differentiation factor 88 (MyD88) is an adaptor molecule composed of an N-terminal death domain and a C-terminal Toll/interleukin (IL)-1R homology domain. Ligand binding to Toll-like receptor (TLR)/IL-1R family members results in the association of MyD88 to the cytoplasmic tail of receptors; this then initiates the signaling cascade that leads to the activation of nuclear factor-kappa B and mitogen-activated protein kinases. Analysis of MyD88-deficient mice revealed its essential role in TLR/IL-1R signaling as well as in both the innate and the adaptive immune response.