MyD88 was identified as an adapter molecule in the IL-1 signaling pathway. MyD88 associates with and recruits IRAK to the IL-1 receptor complex in response to IL-1 treatment. Dominant-negative form of MyD88 attenuates IL-1R-mediated NF-B activation. MyD88 is also employed as a regulator molecule by IL-18 receptor and human Toll receptor, which are members in the Toll/IL-1R family of receptors. Targeted disruption of the MyD88 gene results in loss of cellular responses to IL-1 and IL-18. MyD88 is a general adaptor protein for the Toll/IL-1R family of receptors and plays an important role in the inflammatory response induced by cytokines IL-1 and IL-18 and endotoxin. MyD88 gene is expressed in many tissues.