The kinase activities of interleukin-1 receptor associated kinase (IRAK)-1 and 4 are redundant in the control of inflammatory cytokine expression in human cells.

IRAK-1 and IRAK-4 are protein kinases that mediate signaling by Toll/IL1/Plant R (TIR) domain-containing receptors including the IL-1, IL-18, and Toll-like receptors (TLRs). Although well studied in mouse systems, the mechanism by which they function in human systems is less clear. To extend our knowledge of how these proteins regulate inflammatory signaling in human cells, we genetically and pharmacologically manipulated IRAK-1 and IRAK-4 kinase activities in vitro.