Sensing, presenting, and regulating PAMPs.

Recognition of microbial infection and initiation of immune responses are controlled by multiple mechanisms. Toll-like receptors (TLRs) are key components of the innate immune system that detect microbial infection. TLR activation helps to eliminate the invading pathogens, coordinate systemic defenses, and initiate adaptive immune responses. Despite progress elucidating the TLR signaling aspects and the physiological relevance of TLRs in microbial infections, the molecular basis of microbial recognition by TLRs is still not fully understood. In this article we focus on the availability of microbial ligands to regulate presentation to TLRs and assist in our understanding of TLR-mediated microbial recognition.