IRAK4, an IRAK type protein kinase, is a signal transducer for the immune response Toll-like receptor and interleukin-1 (IL-1) receptor signaling cascades. IRAK4 has auto- and cross-phosphorylation kinase activity and has been shown to phosphorylate and activate IRAK1. Additionally, IRAK4 interacts with IRAK1 and TRAF6 in an IL-1-dependent manner, and overexpression of IRAK4 can activate NF-kappaB as well as mitogen-activated protein (MAP) kinase pathways. IRAK4 (-/-) mice are resistant to a lethal dose of lipopolysaccharide and are severely impaired in their responses to viral and bacterial challenges. At least two mRNA transcripts have been reported: 3.0- and 4.4-kb. IRAK4, also referrred to as NY-REN-64, was first identified as an antigen in a screen of renal tumors.Synonyms: IRAK-4, Interleukin-1 receptor-associated kinase-like, NY-REN-64