MyD88, originally isolated as myeloid differentiation primary response gene, is expressed in a variety of tissues.  MyD88 serves as a cytoplasmic adaptor protein involved in the signaling of TLR and IL-1R family members.  It associates with and recruits IRAK to IL-1R complex in response to IL-1. This pathway leads to activation of NF-kB. Targeted disruption of the MyD88 gene results in loss of cellular responses to IL-1 and IL-18. MyD88 deficient mice lack a response to LPS (a bacterial product) which employs toll like receptors 2 and 4 (TLR2 and TLR4) as signaling receptors.

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