|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.