Evolutionarily conserved signaling intermediate in Toll pathway, mitochondrial (ECSIT), also known as SITPEC, is a protein that in humans is encoded by the ECSIT gene. Activation of NF-kB as a result of Toll-like receptor (TLR) and IL-1 receptor signaling is a major component of innate immune responses. Signals from these receptors are relayed by a number of adapter molecules such as TRIF, TIRAP, and MyD88 to kinases such as IRAK and other intermediates such as TNF receptor associated factor (TRAF)-6. ECSIT (evolutionarily conserved signaling intermediate in Toll pathways) was initially identified as a cytoplasmic protein interacting specifically with TNF receptor associated factor (TRAF)-6 in the TLR pathway. Recently however, ECSIT has also been shown to be required for bone morphogenetic protein (Bmp) signaling and mesoderm formation during mouse embryogenesis, indicating the possibility of cross-talk between the TLR/IL-B and Bmp signaling pathways.