The Trif protein is a key mediator for signaling from TLR3 and TLR4

The Trif protein, identified genetically as Lps2, is a key mediator for signaling from TLR3 and TLR4, which alert the host to infection by viruses and Gram-negative bacteria, respectively. The identification of Trif answers many questions as to how the innate immune system is "wired" for immediate responses to infection. Trif is one of five known adapter proteins (ovals) that signal within host cells when an infection is present. Two of the others, shown here, are MyD88 and Tirap. The adapters stimulate a complex network of chemical reactions within the cell leading to the release of protein messengers called cytokines, and also triggering the production of antibodies by neighboring lymphocytes.