TRIF is primarily active in the spleen and is often regulated when MyD88 is deficient in the liver, indicating organ-specific regulation of signaling pathways. Curiously, there is a lack of redundancy within the TLR4 signaling pathway that leads to microbial evasion of immune response in the host after mutations occur within intermediates of the pathway. Three TRAF-binding motifs present in the amino terminal region of TRIF are necessary for association with TRAF6. Destruction of these motifs reduced the activation of NF-??, a transcription factor that is also activated by the carboxy-terminal domain of TRIF in the upregulation of cytokines and co-stimulatory immune molecules. This domain recruits receptor-interacting protein (RIP1) and RIP3 through the RIP homotypic interaction motif.