Through the recognition of viral, microbial and fungal components, Toll-like receptors (TLRs) serve the critical role of alerting the host to the presence of infectious organisms. In response to these non-self structures, TLRs activate intracellular signaling cascades that are ultimately tailored to protect the host from the type of invading pathogen. Among the ten member TLR family, TLR2 requires TLR1 or TLR6 to recognize, discriminate and initiate responses to a wide variety of microbial components. Tailored host responses are achieved by recruitment of adaptor molecules specific for the TLRs that are engaged. The studies proposed here address the precise function, physical interactions and mechanism of microbial induced activation of TLR2 in association with TLR1, TLR6 and the adaptor molecules MyD88 and TIRAP/MAL. The specific function of TLR1 and TLR6 with respect to agonist discrimination and the structural basis of this discrimination are assessed through the use of synthetic agonists and receptor domain swapping experiments. The effect of abrogating endogenous receptor or adaptor molecule expression/activity on signaling and global gene induction is evaluated in order to delineate the specific role of each signaling component during pathogen-induced cellular activation. The mechanism underlying signal initiation is addressed through studies of the subcellular movement, physical interactions and protein modifications of the receptors and their adaptor molecules as a result of agonist encounter. [unreadable] [unreadable] [unreadable]